Patent Publication Number: US-2009220495-A1

Title: Cancer Related Genes (PRLR)

Description:
This application claims the benefit of U.S. Provisional Application No. 60/669,861, filed Apr. 7, 2005. 
    
    
     TECHNICAL FIELD 
     This invention is in the field of cancer-associated genes. Specifically it relates to methods for detecting cancer or the likelihood of developing cancer based on the presence or absence of PRLR gene expression or proteins encoded by this gene. The invention also provides methods and molecules for upregulating or downregulating the PRLR gene. In addition, the invention provides methods and molecules for the treatment of cancer, as well as methods of screening for molecules useful for the treatment of cancer. 
     BACKGROUND OF THE INVENTION 
     Oncogenes are genes that can cause cancer. Carcinogenesis can occur by a wide variety of mechanisms, including infection of cells by viruses containing oncogenes, activation of protooncogenes (normal genes that have the potential to become an oncogene) in the host genome, and mutations of protooncogenes and tumour suppressor genes. Carcinogenesis is fundamentally driven by somatic cell evolution (i.e. mutation and natural selection of variants with progressive loss of growth control). The genes that serve as targets for these somatic mutations are classified as either protooncogenes or tumour suppressor genes, depending on whether their mutant phenotypes are dominant or recessive, respectively. 
     There are a number of viruses known to be involved in human as well as animal cancer. Of particular interest here are viruses that do not contain oncogenes themselves; these are slow-transforming retroviruses. Such viruses induce tumours by integrating into the host genome and affecting neighboring protooncogenes in a variety of ways. Provirus insertion mutation is a normal consequence of the retroviral life cycle. In infected cells, a DNA copy of the retrovirus genome (called a provirus) is integrated into the host genome. A newly integrated provirus can affect gene expression in cis at or near the integration site by one of two mechanisms. Type I insertion mutations up-regulate transcription of proximal genes as a consequence of regulatory sequences (enhancers and/or promoters) within the proviral long terminal repeats (LTRs). Type II insertion mutations located within the intron or exon of a gene can up-regulate transcription of said gene as a consequence of regulatory sequences (enhancers and/or promoters) within the proviral long terminal repeats (LTRs). Additionally, type II insertion mutations can cause truncation of coding regions due to either integration directly within an open reading frame or integration within an intron flanked on both sides by coding sequences, which could lead to a truncated or an unstable transcript/protein product The analysis of sequences at or near the insertion sites has led to the identification of a number of new protooncogenes. 
     With respect to lymphoma and leukemia, retroviruses such as AKV murine leukemia virus (MLV) or SL3-3 MLV, are potent inducers of tumours when inoculated into susceptible newborn mice, or when carried in the germline. A number of sequences have been identified as relevant in the induction of lymphoma and leukemia by analyzing the insertion sites; see Sorensen et al., J. Virology 74:2161 (2000); Hansen et al., Genome Res. 10(2):237-43 (2000); Sorensen et al., J. Virology 70:4063 (1996); Sorensen et al., J. Virology 67:7118 (1993); Joosten et al., Virology 268:308 (2000); and Li et al., Nature Genetics 23:348 (1999); all of which are expressly incorporated by reference herein. With respect to cancers, especially breast cancer, prostate cancer and cancers with epithelial origin, the mammalian retrovirus, mouse mammary tumour virus (MMTV) is a potent inducer of tumours when inoculated into susceptible newborn mice, or when carried in the germ line.  Mammary Tumours in the Mouse , edited by J. Hilgers and M. Sluyser; Elsevier/North-Holland Biomedical Press; New York, N.Y. 
     The pattern of gene expression in a particular living cell is characteristic of its current state. Nearly all differences in the state or type of a cell are reflected in the differences in RNA levels of one or more genes. Comparing expression patterns of uncharacterized genes may provide clues to their function. High throughput analysis of expression of hundreds or thousands of genes can help in (a) identification of complex genetic diseases, (b) analysis of differential gene expression over time, between tissues and disease states, and (c) drug discovery and toxicology studies. Increase or decrease in the levels of expression of certain genes correlate with cancer biology. For example, oncogenes are positive regulators of tumourigenesis, while tumour suppressor genes are negative regulators of tumourigenesis. (Marshall, Cell, 64: 313-326 (1991); Weinberg, Science, 254: 1138-1146 (1991)). 
     Immunotherapy, or the use of antibodies for therapeutic purposes has been used in recent years to treat cancer. Passive immunotherapy involves the use of monoclonal antibodies in cancer treatments. See for example,  Cancer: Principles and Practice of Oncology,  6 th  Edition (2001) Chapt. 20 pp. 495-508. Inherent therapeutic biological activity of these antibodies include direct inhibition of tumour cell growth or survival, and the ability to recruit the natural cell killing activity of the body&#39;s immune system. These agents are administered alone or in conjunction with radiation or chemotherapeutic agents. Rituxan® and Herceptin®, approved for treatment of lymphoma and breast cancer, respectively, are two examples of such therapeutics. Alternatively, antibodies are used to make antibody conjugates where the antibody is linked to a toxic agent and directs that agent to the tumour by specifically binding to the tumour. Mylotarg® is an example of an approved antibody conjugate used for the treatment of leukemia. However, these antibodies target the tumour itself rather than the cause. 
     A better approach for anti-cancer therapy would be to target the protooncogenes that can cause cancer. In order to do this, protooncogenes must first be identified. Once these genes have been identified, then they can be monitored to detect the onset of cancer and can then be targeted to treat cancer. 
     Prolactin receptor (PRLR) is a single membrane-spanning class 1 cytokine receptor that is homologous to receptors for members of the cytokine superfamily, such as the receptors for IL2, IL3, IL4, IL6, IL7, erythropoietin, and GM-CSF. PRLR is involved in multiple biological functions, including cell growth, differentiation, development, lactation and reproduction. It has no intrinsic tyrosine kinase activity; ligand binding leads to receptor dimerization, cross-phosphorylation of Jak2 and downstream signaling. Human prolactin receptor cDNA was originally isolated from hepatoma and breast cancer libraries (Boutin, J.-M. et al., Molec. Endocr. 3: 1455-1461, 1989). The nucleotide sequence predicted a mature protein of 598 amino acids with a much longer cytoplasmic domain than the rat liver PRL receptor. The prolactin receptor gene resides in the same chromosomal region as the growth hormone receptor gene, which has been mapped to 5; 13-p12 (Arden, K. C. et al. Cytogenet. Cell Gene 53: 161-165, 1990; Arden, K. C. et al., (Abstrace) AM. J. Hum. Genet. 45 (suppl.): A129 only, 1989). Growth hormone also binds to the prolactin receptor and activates the receptor. 
     The genomic organization of the human PRLR gene has been determined (Hu, Z.-Z. et al., J. Clin. Endocr. Metab. 84: 1153-1156, 1999). The 5-prime-untranslated region of the PRLR gene contains 2 alternative first exons: E13, the human counterpart o the rat and mouse E13, and a novel human type of alternative first exon termed E1N. The 5-prime-untranslated region also contains a common noncoding exon 2 and part of exon 3, which contains the translation initiation codon. The E13 and E1N exons are within 800 basepairs of each other. 
     These 2 exons are expressed in human breast tissue, breast cancer cells, gonads, and liver. Overall, the transcript containing E13 is prevalent in most tissues. The PRLR gene product is encoded by exons 3-10, of which exon 10 encodes most of the intracellular domain. The E13 and E1N exons are transcribed from alternative promoters PIII and PN, respectively. The PIII promoter contains Sp1 and C/EBP elements that are identical to those in the rodent promoter and is 81% similar to the region −480/−106 in the rat and mouse. The PN promoter contains putative binding sites for ETS family proteins and a half-site for nuclear receptors. 
     PRLR exists in a number of different isoforms that differ in the length of their cytoplasmic domains. Four PRLR mRNA isoforms (L, I, S1a, and S1b) have been demonstrated in human subcutaneous abdominal adipose tissue and breast adipose tissue (Ling, C. et al., J. Clin. Endocr. Metab. 88: 1804-1808, 2003). In addition, they detected L-PRLR and I-PRLR protein expression in human subcutaneous abdominal adipose tissue and breast adipose tissue using immunoblot analysis. PRL reduced the lipoprotein lipase activity in human adipose tissue compared with control. Ling et al. suggest that these results demonstrated a direct effect of PRL, via functional PRLRs, in reducing the LPL activity in human adipose tissue, and that these results suggested that LPL might also be regulated in this fashion during lactation. The function of these PRLR isoforms in rat has been elucidated (Perrot-Applanat, M. et al., Molec. Endocr. 11: 1020-1032, 1997). Like the known long form (591 amino acids), the Nb2 form, which lacks 198 amino acids of the cytoplasmic domain, is able to transmit a lactogenic signal. In contrast, the short form, which lacks 291 amino acids of the cytoplasmic domain, is inactive. The function of the short form was examined after cotransfection of both the long and short forms. These results show that the short form acts as a dominant-negative inhibitor through the formation of inactive heterodimers, resulting in the inhibition of Janus kinase 2 activation. Perrot-Applanat et al. suggest that heterodimerization of PRLR can positively or negatively activate PRL transcription. 
     Glasow, A. et al., J. Clin. Endocr. Metab. 86: 3826-3832, 2001, examined the presence of PRLR in 41 breast tumors by immunohistochemistry and attempted to correlate its expression to pathologic grading of the disease. The PRLR immunoreactive score did not correlate to tumor size, histopathologic grading, age, or family history of patients. In both PRLR-positive and -negative breast cancer cells, direct sequencing of the coding sequence of the PRLR gene did not detect any somatic or hereditary gene aberrations. The authors concluded that PRLR mutations do not appear to be common in human breast cancer, suggesting that constitutive activation of PRLR can be excluded as a major cause of mammary tumor genesis. 
     PRL female transgenic mice develop malignant mammary adenocarcinomas (Wennbo et al., J. Clin. Invest. 100:2744-2751, 1997). A PRLR monoclonal antibody diminished the incidence of mammary tumors in mice (Sissom et al., Am. J. Pathol. 133:589-595, 1988). In addition, a PRL antagonist (S179D mutant PRL) inhibited proliferation of a human prostate carcinoma cell line, DU-145, in vitro and DU-145 induced tumors in vivo (Xu et al., Cancer Res., 61:6098-6104, 2001). 
     SUMMARY OF THE INVENTION 
     Protooncogenes have been identified in humans using a process known as “provirus tagging”, in which slow-transforming retroviruses that act by an insertion mutation mechanism are used to isolate protooncogenes using mouse models. In some models, uninfected animals have low cancer rates, and infected animals have high cancer rates. It is known that many of the retroviruses involved do not carry transduced host protooncogenes or pathogenic trans-acting viral genes, and thus the cancer incidence must therefore be a direct consequence of proviral integration effects into host protooncogenes. Since proviral integration is random, rare integrants will “activate” host protooncogenes that provide a selective growth advantage, and these rare events result in new proviruses at clonal stoichiometries in tumors. In contrast to mutations caused by chemicals, radiation, or spontaneous errors, protooncogene insertion mutations can be easily located by virtue of the fact that a convenient-sized genetic marker of known sequence (the provirus) is present at the site of mutation. Host sequences that flank clonally integrated proviruses can be cloned using a variety of strategies. Once these sequences are in hand, the tagged protooncogenes can be subsequently identified. The presence of provirus at the same locus in two or more independent tumors is prima facie evidence that a protooncogene is present at or very near the provirus integration sites (Kim et al, Journal of Virology, 2003, 77:2056-2062; Mikkers, H and Berns, A, Advances in Cancer Research, 2003, 88:53-99; Keoko et al. Nucleic Acids Research, 2004, 32:D523-D527). This is because the genome is too large for random integrations to result in observable clustering. Any clustering that is detected is unequivocal evidence for biological selection (i.e. the tumor phenotype). Moreover, the pattern of proviral integrants (including orientations) provides compelling positional information that makes localization of the target gene at each cluster relatively simple. The three mammalian retroviruses that are known to cause cancer by an insertion mutation mechanism are FeLV (leukemia/lymphoma in cats), MLV (leukemia/lymphoma in mice and rats), and MMTV (mammary cancer in mice). Once protooncogenes have been identified in mouse models, the human orthologs can be annotated as protooncogenes and further investigations carried out. 
     Thus, the use of oncogenic retroviruses, whose sequences insert into the genome of the host organism resulting in cancer, allows the identification of host genes involved in cancer. These sequences may then be used in a number of different ways, including diagnosis, prognosis, screening for modulators (including both agonists and antagonists), antibody generation (for immunotherapy and imaging), etc. However, as will be appreciated by those in the art, oncogenes that are identified in one type of cancer such as lymphoma or leukemia have a strong likelihood of being involved in other types of cancers as well. 
     The invention therefore provides methods for detecting cancerous cells in a biological sample comprising determining the sequence or expression level of the PRLR gene, a cancer-associated gene. 
     Preferably the method includes measuring the level of expression of one or more (i.e. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) expression products of the PRLR gene, wherein a level of expression that is different to a control level is indicative of disease. 
     The expression product is preferably a protein, although alternatively mRNA expression products may be detected. If a protein is used, the protein is preferably detected by an antibody which preferably binds specifically to that protein. The term “binds specifically” means that the antibodies have substantially greater affinity for their target polypeptide than their affinity for other related polypeptides. As used herein, the term “antibody” refers to intact molecules as well as to fragments thereof, such as Fab, F(ab′)2 and Fv, which are capable of binding to the antigenic determinant in question. Further examples of antibodies include fully assembled antibodies, monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies), single chain antibodies, diabodies, and recombinant peptides comprising the forgoing as long as they exhibit the desired biological activity (e.g., binding to the extracellular domain of PRLR). By “substantially greater affinity” we mean that there is a measurable increase in the affinity for the target polypeptide of the invention as compared with the affinity for other related polypeptide. The affinity is at least 1.5-fold, 2-fold, 5-fold 10-fold, 100-fold, 10 3 -fold, 10 4 -fold, 10 5 -fold, 10 6 -fold or greater for the target polypeptide compared to the affinity of other known homologues or orthologues. Alternatively, it might be useful for the antibody to cross react with a known homologue or orthologue. 
     Preferably, the antibodies bind with high affinity, preferably with a 10 −4 M, 10 −5 M, 10 −6 M or less, preferably 10 −7 M, 10 −8 M or less, most preferably 10 −9 M or 10 −10 M or less; subnanomolar affinity (0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1 nM or even less) is preferred. 
     Where mRNA expression product is used, it is preferably detected by contacting a tissue sample with a probe under stringent conditions that allow the formation of a hybrid complex between the mRNA and the probe; and detecting the formation of a complex. 
     The PRLR gene itself may be detected by contacting a biological sample with a nucleic acid probe under stringent conditions that allow the formation of a hybrid complex between a nucleic acid expression product encoding the PRLR gene and the probe; and detecting the formation of a complex between the probe and the nucleic acid from the biological sample. In such a case, the absence of the formation of a complex preferably is indicative of a mutation in the sequence of the PRLR gene. 
     Preferred methods include comparing the amount of complex formed with that formed when a control tissue is used, wherein a difference in the amount of complex formed between the control and the sample indicates the presence of cancer. Preferably the difference between the amount of complex formed by the test tissue compared to the normal tissue is an increase or decrease. More preferably a two-fold increase or decrease in the amount of complex formed is indicative of disease. Even more preferably, a 3-fold, 4-fold, 5-fold, 10-fold, 20-fold, 50-fold or even 100-fold increase or decrease in the amount of complex formed is indicative of disease. 
     The biological sample used in the methods of the invention is preferably a tissue sample. Any tissue sample may be used. Preferably, however, the tissue is selected from breast tissue, colon tissue, kidney tissue, liver tissue, lung tissue, lymphoid tissue, ovary tissue, pancreas tissue, prostate tissue, uterine tissue, cervix tissue or skin tissue. 
     The invention also provides methods for assessing the progression of cancer in a patient comprising comparing the expression of one or more (i.e. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) expression products of the PRLR gene referred to above in a biological sample at a first time point to the expression of the same expression product at a second time point, wherein an increase or decrease in expression, or in the rate of increase or decrease of expression, at the second time point relative to the first time point is indicative of the progression of the cancer. 
     The invention also provides kits useful for diagnosing cancer comprising an antibody that binds to a polypeptide expression product of the PRLR gene; and a reagent useful for the detection of a binding reaction between said antibody and said polypeptide. Preferably, the antibody binds specifically to the polypeptide product of the PRLR gene. 
     Furthermore, the invention provides a kit useful for diagnosing cancer comprising a nucleic acid probe that hybridises under stringent conditions to the PRLR gene; primers useful for amplifying the PRLR gene; and optionally instructions for using the probe and primers for facilitating the diagnosis of disease. 
     The invention further provides antibodies, nucleic acids, or proteins suitable for use in modulating the expression of one or more (i.e. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) expression products of the PRLR gene, for use in treating cancer. 
     Accordingly, the invention provides methods for treating cancer in a patient, comprising modulating the level of one or more (i.e. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) expression products of the PRLR gene. Such a method preferably comprises administering to the patient an antibody, a nucleic acid, or a polypeptide that modulates the level of said expression product in a therapeutically-effective amount. 
     The invention therefore also provides the use of an antibody, a nucleic acid, or a polypeptide that modulates the level of an expression product of the PRLR gene, in the manufacture of a medicament for the treatment or diagnosis of cancer. Such level of expression is preferably modulated by action on the gene, mRNA or the encoded protein. The expression is preferably upregulated or downregulated. For example, the change in regulation may be 2-fold, 3-fold, 5-fold, 10-fold, 20-fold, 50-fold, or even 100 fold or more. 
     Antibodies suitable for use in accordance with the present invention may be specific for PRLR polypeptides as these are expressed on or within cancerous cells. For example, glycosylation patterns in cancer-associated proteins as expressed on cancerous cells may be different to the patterns of glycosylation in these same proteins as these are expressed on non-cancerous cells. Preferably, in such a scenario, antibodies according to the invention are specific for PRLR proteins as expressed on cancerous cells only. This is of particular value for therapeutic antibodies. Anti-target antibodies may of course bind to any or all splice variants, deletion, addition and/or substitution mutants of the target. 
     Antibodies suitable for therapeutic use in accordance with the present invention may preferably be effective to elicit antibody-dependent cellular cytotoxicity (ADCC). ADCC refers to the cell-mediated reaction wherein non-specific cytotoxic cells that express Fc receptors recognize bound antibody on a target cell and subsequently cause lysis of the target cell (Raghavan et al., 1996, Annu Rev Cell Dev Biol 12:181-220; Ghetie et al., 2000, Annu Rev Immunol 18:739-766; Ravetch et al., 2001, Annu Rev Immunol 19:275-290). Antibodies suitable for therapeutic use in accordance with the present invention may preferably be effective to elicit antibody-dependent cell-mediated phagocytosis (ADCP). ADCP is the cell-mediated reaction wherein nonspecific cytotoxic cells that express Fc receptors recognize bound antibody on a target cell and subsequently cause phagocytosis. These processes are mediated by natural killer (NK) cells, which possess receptors on their surface for the Fc portion of IgG antibodies. When IgG is made against epitopes on “foreign” membrane-bound cells, including cancer cells, the Fab portions of the antibodies react with the cancerous cell. The NK cells then bind to the Fc portion of the antibody. 
     Preferably, antibodies for therapeutic use in accordance with the invention are effective to elicit ADCC, and modulates the survival of cancerous cells by binding to target and having ADCC activity. Antibodies can be engineered to heighten ADCC activity (see, for example, US 20050054832A1, Xencor Inc. and the documents cited therein). 
     The nucleic acid type used in such methods is preferably an antisense construct, a ribozyme or RNAi, particularly siRNA. 
     The cancer may be treated by the inhibition of tumour growth or the reduction of tumour volume or, alternatively, by reducing the invasiveness of a cancer cell. In some embodiments, the methods of treatment described above are used in conjunction with one or more of surgery, hormone ablation therapy, radiotherapy or chemotherapy. For example, if a patient is already receiving chemotherapy, a compound of the invention that modulates the level of an expression product as listed above may also be administered. The chemotherapeutic, hormonal and/or rediotherapeutic agent and compound according to the invention may be administered simultaneously, separately or sequentially. 
     Preferably the cancer being detected or treated according to one of the methods described above is selected from breast cancer, colon cancer, kidney cancer, liver cancer, lung cancer, lymphoid cancer, ovary cancer, pancreas cancer, prostate cancer, uterine cancer, cervix cancer or skin cancer. 
     The invention also provides a method for identifying a patient as susceptible to treatment with a PRLR-modulating antibody, comprising measuring the expression level of the PRLR gene expression product in a biological sample from that patient. 
     Furthermore, the invention provides a method for identifying a patient as susceptible to treatment with a PRLR-modulating antibody, wherein the expression level of the PRLR gene expression product at a first time point is compared to the expression of the same expression product at a second time point, wherein an increase or decrease in expression at the second time point relative to the first time point is indicative of the progression of a cancer in which the PRLR gene is implicated. 
     The invention further provides assays for identifying a candidate agent that modulates the growth of a cancerous cell, comprising: 
     a) detecting the level of expression of one or more (i.e. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) expression product of the PRLR gene as listed in any of the above-described embodiments of the invention in the presence of the candidate agent; and
 
b) comparing that level of expression with the level of expression in the absence of the candidate agent, wherein a difference in expression indicates that the candidate agent modulates the level of expression of the expression product of the PRLR gene.
 
     The invention also provides methods for identifying an agent that modifies the expression level of the PRLR gene, comprising: 
     a) contacting a cell expressing the PRLR gene as listed in any of the above-described embodiments of the invention with a candidate agent, and
 
b) determining the effect of the candidate agent on the cell, wherein a change in expression level indicates that the candidate agent is able to modulate expression.
 
     Preferably the agent is a polynucleotide, a polypeptide, an antibody or a small organic molecule. 
     The invention also provides a method for detecting breast cancer in a biological sample comprising determining the sequence or expression level of PRLR, which is correlated to breast cancer. 
     The invention also provides a method for detecting lung cancer in a biological sample comprising determining the sequence or expression level of PRLR, which is correlated to lung cancer. 
     The invention also provides a method for detecting prostate cancer in a biological sample comprising determining the sequence or expression level of PRLR, which is correlated to prostate cancer. 
     The invention also provides a method for detecting skin cancer in a biological sample comprising determining the sequence or expression level of PRLR, which is correlated to skin cancer. 
     In one embodiment of the invention, an isolated antibody is provided that specifically binds to the extracellular domain of PRLR having the amino acid sequence of residues 25 through 234 of SEQ ID NO: 2. In another embodiment, the antibody specifically binds to an S1 domain or an S2 domain of a PRLR isoform. In another embodiment, the antibody inhibits proliferation or survival of breast, lung, prostate, or skin cancer cells. In still another embodiment, the antibody is a monoclonal antibody, a humanized antibody, or a human antibody. In still another embodiment, the antibody retains binding affinity to the extracellular domain of PRLR of 10 −8  or 10 −9  M or less. 
     In one embodiment of the invention, a pharmaceutical composition is provided comprising an aforementioned antibody and a pharmaceutically suitable carrier, excipient or diluent. In another embodiment, the pharmaceutical composition further comprises a second therapeutic agent. In still another embodiment, the second therapeutic agent is a cancer chemotherapeutic agent. 
     In another embodiment, the present invention provides a method of treating a subject suffering from breast, lung, prostate, or skin cancer comprising the step of administering an aforementioned antibody in a therapeutically effective amount. In another embodiment, the subject is suffering from breast cancer, lung cancer, prostate cancer, or skin cancer. 
     In still another embodiment of the invention, a use of an aforementioned antibody in the preparation of a medicament for treatment of a cancer selected from the group consisting of breast, lung, prostate, or skin cancer is provided. In another embodiment, the cancer is breast cancer, lung cancer, prostate cancer, or skin cancer. 
     In one embodiment of the invention, the present invention provides a method of treating a subject suffering from breast, lung, prostate, or skin cancer comprising the step of administering an aforementioned antibody in a therapeutically effective amount, wherein the binding of the antibody to PRLR inhibits prolactin binding to PRLR and/or inhibits the induction of MAPK phosphorylation and/or inhibits the induction of Stat5 phosphorylation and/or inhibits the activation of c-Src/Fyn and/or PI-3 kinase and/or Akt and/or JAK2 and/or Ras signaling. Such inhibition can be, e.g., at least 2-fold, 5-fold, 10-, 20-, or 100-fold. 
     In still another embodiment of the invention, a method of screening for an antibody to the extracellular domain of a PRLR protein useful for the treatment of cancer is provided comprising the steps of a) contacting a breast, lung, prostate, or skin cell and a candidate antibody; b) detecting proliferation or survival of the cell; and c) identifying the candidate antibody as an antibody useful for the treatment of cancer if a decrease in cell proliferation or survival is detected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a gel showing PCR amplification of host/virus junction fragments. 
         FIG. 2  shows the hypothetical distribution profiles between control and disease samples. Figure taken from Pepe et. al. 
         FIG. 3  shows the results of the Rat-1 and Rat-1/PRLR soft agar assay. 
         FIG. 4  shows the results of the tumorigenicity assay of Rat-1 cell lines. 
         FIG. 5  shows that most human cancer cell lines express the long form of PRLR (LF) 
         FIG. 6  shows the effect of PRLR-specific siRNA on MCF-7 human cancer cell line proliferation 
         FIG. 7  shows that hPRL stimulates STAT5 and MAPK phosphorylation in a time-dependent manner. 
         FIG. 8  shows the PRLR splice variant structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention identifies that PRLR is implicated in the incidence of cancer. The PRLR gene is therefore referred to as a “cancer-associated gene”. Thus, PRLR polypeptides encoded by this gene are referred to as “cancer-associated polypeptides” or “cancer-associated proteins”. Nucleic acid sequences that encode these cancer-associated polypeptides are referred to as “cancer-associated polynucleotides”. Cells which encode and/or express a cancer-associated gene are referred to as “cancer-associated cells”. Cells which encode a cancer-associated gene are said to have a “cancer-associated genotype”. Cells which express a cancer-associated protein are said to have a “cancer-associated phenotype”. “Cancer-associated sequences” refers to both PRLR polypeptide and polynucleotide sequences. “Cancer-associated nucleic acids” includes the DNA comprising the cancer-associated gene (PRLR), as well as mRNA and cDNA derived from that gene. 
     “Associated” in this context means that the nucleotide or protein sequences are either differentially expressed, activated, inactivated or altered in cancers as compared to normal tissue. As outlined below, cancer-associated PRLR sequences include those that are up-regulated (i.e. expressed at a higher level), as well as those that are down-regulated (i.e. expressed at a lower level), in cancers. Cancer-associated PRLR sequences also include sequences that have been altered (i.e., truncated sequences or sequences with substitutions, deletions or insertions, including point mutations) and show either the same expression profile or an altered profile. Generally, the cancer-associated PRLR sequences are from humans; however, as will be appreciated by those in the art, cancer-associated sequences from other organisms may be useful in animal models of disease and drug evaluation; thus, other cancer-associated PRLR sequences may be identified, from vertebrates, including mammals, including rodents (rats, mice, hamsters, guinea pigs, etc.), primates, and farm animals (including sheep, goats, pigs, cows, horses, etc). In some cases, prokaryotic cancer-associated sequences may be useful. Cancer-associated sequences from other organisms may be obtained using the techniques outlined below. 
     Cancer-associated PRLR sequences include recombinant nucleic acids. By the term “recombinant nucleic acid” herein is meant nucleic acid, originally formed in vitro, in general, by the manipulation of nucleic acid by polymerases and endonucleases, in a form not normally found in nature. Thus a recombinant nucleic acid is also an isolated nucleic acid, in a linear form, or cloned in a vector formed in vitro by ligating DNA molecules that are not normally joined, are both considered recombinant for the purposes of this invention. It is understood that once a recombinant nucleic acid is made and reintroduced into a host cell or organism, it will replicate using the in vivo cellular machinery of the host cell rather than in vitro manipulations; however, such nucleic acids, once produced recombinantly, although subsequently replicated in vivo, are still considered recombinant or isolated for the purposes of the invention. As used herein a “polynucleotide” or “nucleic acid” is a polymeric form of nucleotides of any length, either ribonucleotides or deoxyribonucleotides. This term refers only to the primary structure of the molecule. Thus, this term includes double- and single-stranded DNA and RNA. It also includes known types of modifications, for example, labels which are known in the art, methylation, “caps”, substitution of one or more of the naturally occurring nucleotides with an analog, internucleotide modifications such as, for example, those with uncharged linkages (e.g., phosphorothioates, phosphorodithioates, etc.), those containing pendant moieties, such as, for example proteins (including e.g., nucleases, toxins, antibodies, signal peptides, poly-L-lysine, etc.), those with intercalators (e.g., acridine, psoralen, etc.), those containing chelators (e.g., metals, radioactive metals, etc.), those containing alkylators, those with modified linkages (e.g., alpha anomeric nucleic acids, etc.), as well as unmodified forms of the polynucleotide. 
     As used herein, a polynucleotide “derived from” a designated sequence refers to a polynucleotide sequence which is comprised of a sequence of approximately at least about 6 nucleotides, preferably at least about 8 nucleotides, more preferably at least about 10-12 nucleotides, and even more preferably at least about 15-20 nucleotides corresponding to a region of the designated nucleotide sequence. “Corresponding” means homologous to or complementary to the designated sequence. Preferably, the sequence of the region from which the polynucleotide is derived is homologous to or complementary to a sequence that is unique to a cancer-associated gene. 
     A “recombinant protein” is a protein made using recombinant techniques, i.e. through the expression of a recombinant nucleic acid as depicted above. A recombinant protein is distinguished from naturally occurring protein by at least one or more characteristics. For example, the protein may be isolated or purified away from some or all of the proteins and compounds with which it is, normally associated in its wild type host, and thus may be substantially pure. For example, an isolated protein is unaccompanied by at least some of the material with which it is normally associated in its natural state, preferably constituting at least about 0.5%, more preferably at least about 5% by weight of the total protein in a given sample. A substantially pure protein comprises about 50-75% by weight of the total protein, with about 80% being preferred, and about 90% being particularly preferred. The definition includes the production of a cancer-associated protein such as PRLR from one organism in a different organism or host cell. Alternatively, the protein may be made at a significantly higher concentration than is normally seen, through the use of an inducible promoter or high expression promoter, such that the protein is made at increased concentration levels. Alternatively, the protein may be in a form not normally found in nature, as in the addition of an epitope tag or amino acid substitutions, insertions and deletions, as discussed below. 
     As used herein, the term “tag,” “sequence tag” or “primer tag sequence” refers to an oligonucleotide with specific nucleic acid sequence that serves to identify a batch of polynucleotides bearing such tags therein. Polynucleotides from the same biological source are covalently tagged with a specific sequence tag so that in subsequent analysis the polynucleotide can be identified according to its source of origin. The sequence tags also serve as primers for nucleic acid amplification reactions. 
     A “microarray” is a linear or two-dimensional array of preferably discrete regions, each having a defined area, formed on the surface of a solid support. The density of the discrete regions on a microarray is determined by the total numbers of target polynucleotides to be detected on the surface of a single solid phase support, preferably at least about 50/cm 2 , more preferably at least about 100/cm 2 , even more preferably at least about 500/cm 2 , and still more preferably at least about 1,000/cm 2 . As used herein, a DNA microarray is an array of oligonucleotide primers placed on a chip or other surfaces used to amplify or clone target polynucleotides. Since the position of each particular group of primers in the array is known, the identities of the target polynucleotides can be determined based on their binding to a particular position in the microarray. 
     A “linker” is a synthetic oligodeoxyribonucleotide that contains a restriction site. A linker may be blunt end-ligated onto the ends of DNA fragments to create restriction sites that can be used in the subsequent cloning of the fragment into a vector molecule. 
     The term “label” refers to a composition capable of producing a detectable signal indicative of the presence of the target polynucleotide in an assay sample. Suitable labels include radioisotopes, nucleotide chromophores, enzymes, substrates, fluorescent molecules, chemiluminescent moieties, magnetic particles, bioluminescent moieties, and the like. As such, a label is any composition detectable by spectroscopic, photochemical, biochemical, immunochemical, electrical, optical, chemical, or any other appropriate means. The term “label” is used to refer to any chemical group or moiety having a detectable physical property or any compound capable of causing a chemical group or moiety to exhibit a detectable physical property, such as an enzyme that catalyzes conversion of a substrate into a detectable product. The term “label” also encompasses compounds that inhibit the expression of a particular physical property. The label may also be a compound that is a member of a binding pair, the other member of which bears a detectable physical property. 
     The term “support” refers to conventional supports such as beads, particles, dipsticks, fibers, filters, membranes, and silane or silicate supports such as glass slides. 
     The term “amplify” is used in the broad sense to mean creating an amplification product which may include, for example, additional target molecules, or target-like molecules or molecules complementary to the target molecule, which molecules are created by virtue of the presence of the target molecule in the sample. In the situation where the target is a nucleic acid, an amplification product can be made enzymatically with DNA or RNA polymerases or reverse transcriptases. 
     As used herein, a “biological sample” refers to a sample of tissue or fluid isolated from an individual, including but not limited to, for example, blood, plasma, serum, spinal fluid, lymph fluid, skin, respiratory, intestinal and genitourinary tracts, tears, saliva, milk, cells (including but not limited to blood cells), tumors, organs, and also samples of in vitro cell culture constituents. 
     The term “biological sources” as used herein refers to the sources from which the target polynucleotides are derived. The source can be of any form of “sample” as described above, including but not limited to, cell, tissue or fluid. “Different biological sources” can refer to different cells/tissues/organs of the same individual, or cells/tissues/organs from different individuals of the same species, or cells/tissues/organs from different species. 
     PRLR Genes 
     By “PRLR” we mean the gene “prolactin receptor” referred to by gene locus ID 5618 in the NCBI public database, having an mRNA referred to under accession number NM — 000949 and encoding the polypeptide referred to under accession number NP — 000940. PRLR is a receptor protein. This gene underwent types I and II integration of either the MLV or MMTV provirus in 16 cases. This gene was found to be overexpressed in 4 of the cancer tissue types tested, and to be overexpressed in 45% of skin tumors sampled, 34% of lung tumors sampled and in 40% of breast tumors sampled. This gene was also found to be overexpressed in prostate tumors sampled (t-test). This means that this gene is correlated to skin, lung, breast and prostate cancer and is therefore a target for the diagnosis and therapy of these diseases. 
     The nucleotide sequence for PRLR is set out in SEQ ID NO: 1, and the amino acid sequence is set out in SEQ ID NO: 2. The extracellular domain consists of amino acids 25 through 234 of SEQ ID NO: 2, which can be divided into two major domains, S1 (amino acids 25-122) and S2 (amino acids 123-234). A number of different isoforms of PRLR have been identified: long (L), intermediate (I), ΔS1, an inactive soluble form (PRLBP), and inactive short forms S1a and S1b. The exons and nucleotide regions contained within each isoform are displayed in  FIG. 8 . In exemplary embodiments, the invention contemplates antibodies that that bind to the S1 domain, or to the S2 domain. Such antibodies that bind to the S2 domain may target all active isoforms. The invention also contemplates antibodies that bind specifically to one isoform and not another (e.g. intermediate and not S1a or S1b), or to the active isoforms (long, intermediate and ΔS1) but not to the inactive isoforms (S1a and S1b). In exemplary embodiments, antibodies of the invention may bind specifically to the long isoform which is expressed predominantly in some cancers, and not to other isoforms (e.g. amino acids encoded by nucleotides 1293-1866), or may bind to the region: EWEIHFAGQQTEFKILSLHP. 
     Therefore the presence or absence of expression of one of the PRLR may be sufficient to cause cancer. Alternatively an increase or decrease in expression of one of the PRLR gene may be sufficient to cause cancer. In a further alternative, cancer may be induced when the expression of the PRLR gene reaches or exceeds a threshold level. The threshold level may be represented as a percentage increase or decrease in expression of the PRLR gene when compared with that in a “normal” control level of expression. 
     The invention also allows the use of homologues, fragments, and functional equivalents of the PRLR gene. Homology can be based on the full PRLR gene sequence referenced above and is generally determined as outlined below, using homology programs or hybridisation conditions. A homologue of the PRLR gene has preferably greater than about 75% (i.e. 80, 85, 90, 92, 94, 95, 96, 97, 98, 99% or more) homology with the PRLR gene. Such homologues may include splice variants, deletion, addition and/or substitution mutants and generally have functional similarity. 
     Homology in this context means sequence similarity or identity, with identity being preferred. A preferred comparison for homology purposes is to compare the sequence containing sequencing errors to the correct sequence. This homology will be determined using standard techniques known in the art, including, but not limited to, the local homology algorithm of Smith &amp; Waterman, Adv. Appl. Math. 2:482 (1981), by the homology alignment algorithm of Needleman &amp; Wunsch, J. Mol. Biol. 48:443 (1970), by the search for similarity method of Pearson &amp; Lipman, PNAS USA 85:2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Drive, Madison, Wis.), the Best Fit sequence program described by Devereux et al., Nucl. Acid Res. 12:387-395 (1984), preferably using the default settings, or by inspection. 
     One example of a useful algorithm is PILEUP. PILEUP creates a multiple sequence alignment from a group of related sequences using progressive, pairwise alignments. It can also plot a tree showing the clustering relationships used to create the alignment. PILEUP uses a simplification of the progressive alignment method of Feng &amp; Doolittle, J. Mol. Evol. 35:351-360 (1987); the method is similar to that described by Higgins &amp; Sharp CABIOS 5:151-153 (1989). Useful PILEUP parameters include a default gap weight of 3.00, a default gap length weight of 0.10, and weighted end gaps. 
     Another example of a useful algorithm is the BLAST (Basic Local Alignment Search Tool) algorithm, described in Altschul et al., J. Mol. Biol. 215, 403-410, (1990) and Karlin et al., PNAS USA 90:5873-5787 (1993). A particularly useful BLAST program is the WU-BLAST-2 program which was obtained from Altschul et al., Methods in Enzymology, 266: 460-480 (1996); http://blast.wust1.edu/]. WU-BLAST-2 uses several search parameters, most of which are set to the default values. The adjustable parameters are set with the following values: overlap span=1, overlap fraction=0.125, word threshold (T)=11. The HSP S and HSP S2 parameters are dynamic values and are established by the program itself depending upon the composition of the particular sequence and composition of the particular database against which the sequence of interest is being searched; however, the values may be adjusted to increase sensitivity. A percent amino acid sequence identity value is determined by the number of matching identical residues divided by the total number of residues of the “longer” sequence in the aligned region. The “longer” sequence is the one having the most actual residues in the aligned region (gaps introduced by WU-Blast-2 to maximize the alignment score are ignored). 
     The alignment may include the introduction of gaps in the sequences to be aligned. In addition, for sequences which contain either more or fewer nucleotides than those of the PRLR gene, it is understood that the percentage of homology will be determined based on the number of homologous nucleosides in relation to the total number of nucleosides. Thus homology of sequences shorter than those of the sequences identified herein will be determined using the number of nucleosides in the shorter sequence. 
     In another embodiment of the invention, polynucleotide compositions are provided that are capable of hybridizing under moderate to high stringency conditions to a polynucleotide sequence provided herein, or a fragment thereof, or a complementary sequence thereof. Hybridization techniques are well known in the art of molecular biology. For purposes of illustration, suitable moderately stringent conditions for testing the hybridization of a polynucleotide of this invention with other polynucleotides include prewashing in a solution of 5×SSC (“saline sodium citrate”; 9 mM NaCl, 0.9 mM sodium citrate), 0.5% SDS, 1.0 mM EDTA (pH 8.0); hybridizing at 50-60° C., 5×SSC, overnight; followed by washing twice at 65° C. for 20 minutes with each of 2×, 0.5× and 0.2×SSC containing 0.1% SDS. One skilled in the art will understand that the stringency of hybridization can be readily manipulated, such as by altering the salt content of the hybridization solution and/or the temperature at which the hybridization is performed. For example, in another embodiment, suitable highly stringent hybridization conditions include those described above, with the exception that the temperature of hybridization is increased, e.g., to 60-65° C., or 65-70° C. Stringent conditions may also be achieved with the addition of destabilizing agents such as formamide. 
     Thus nucleic acids that hybridize under high stringency to the nucleic acids identified throughout the present application and sequence listing, or its complements, are considered PRLR or cancer-associated sequences. High stringency conditions are known in the art; see for example Maniatis et al., Molecular Cloning: A Laboratory Manual, 2nd Edition, 1989, and Short Protocols in Molecular Biology, ed. Ausubel, et al., both of which are hereby incorporated by reference. Stringent conditions are sequence-dependent and will be different in different circumstances. Longer sequences hybridize specifically at higher temperatures. An extensive guide to the hybridization of nucleic acids is found in Tijssen, Techniques in Biochemistry and Molecular Biology—Hybridization with Nucleic Acid Probes, “Overview of principles of hybridization and the strategy of nucleic acid assays” (1993). Generally, stringent conditions are selected to be about 5-10° C. lower than the thermal melting point (T m ) for the specific sequence at a defined ionic strength pH. The T m  is the temperature (under defined ionic strength, pH and nucleic acid concentration) at which 50% of the probes complementary to the target hybridize to the target sequence at equilibrium (as the target sequences are present in excess, at T m , 50% of the probes are occupied at equilibrium). Stringent conditions will be those in which the salt concentration is less than about 1.0 M sodium ion, typically about 0.01 to 1.0 M sodium ion concentration (or other salts) at pH 7.0 to 8.3 and the temperature is at least about 30° C. for short probes (e.g. 10 to 50 nucleotides) and at least about 60° C. for longer probes (e.g. greater than 50 nucleotides). In another embodiment, less stringent hybridization conditions are used; for example, moderate or low stringency conditions may be used, as are known in the art; see Maniatis and Ausubel, supra, and Tijssen, supra. 
     Detection of PRLR Gene Expression 
     The PRLR gene has been identified and the coding sequence and amino acid sequence are referenced herein. Once isolated from its natural source, e.g., contained within a plasmid or other vector or excised therefrom as a linear nucleic acid segment, the recombinant PRLR nucleic acid can be further used as a probe to identify and isolate other PRLR nucleic acids, for example additional coding regions. It can also be used as a “precursor” nucleic acid to make modified or variant PRLR nucleic acids and proteins. The PRLR nucleotide sequence can be used to design probes specific for the PRLR gene. 
     The PRLR nucleic acids may be used in several ways. Nucleic acid probes hybridizable to PRLR nucleic acids can be made and attached to biochips to be used in screening and diagnostic methods, or for gene therapy and/or antisense applications. Alternatively, the PRLR nucleic acids that include coding regions of PRLR proteins can be put into expression vectors for the expression of PRLR proteins, again either for screening purposes or for administration to a patient. 
     One such system for quantifying gene expression is kinetic polymerase chain reaction (PCR). Kinetic PCR allows for the simultaneous amplification and quantification of specific nucleic acid sequences. The specificity is derived from synthetic oligonucleotide primers designed to preferentially adhere to single-stranded nucleic acid sequences bracketing the target site. This pair of oligonucleotide primers forms specific, non-covalently bound complexes on each strand of the target sequence. These complexes facilitate in vitro transcription of double-stranded DNA in opposite orientations. Temperature cycling of the reaction mixture creates a continuous cycle of primer binding, transcription, and re-melting of the nucleic acid to individual strands. The result is an exponential increase of the target dsDNA product. This product can be quantified in real time either through the use of an intercalating dye or a sequence specific probe. SYBR® Greene I, is an example of an intercalating dye, that preferentially binds to dsDNA resulting in a concomitant increase in the fluorescent signal. Sequence specific probes, such as used with TaqMan® technology, consist of a fluorochrome and a quenching molecule covalently bound to opposite ends of an oligonucleotide. The probe is designed to selectively bind the target DNA sequence between the two primers. When the DNA strands are synthesized during the PCR reaction, the fluorochrome is cleaved from the probe by the exonuclease activity of the polymerase resulting in signal dequenching. The probe signaling method can be more specific than the intercalating dye method, but in each case, signal strength is proportional to the dsDNA product produced. Each type of quantification method can be used in multi-well liquid phase arrays with each well representing primers and/or probes specific to nucleic acid sequences of interest. When used with messenger RNA preparations of tissues or cell lines, an array of probe/primer reactions can simultaneously quantify the expression of multiple gene products of interest. See Germer, S., et al., Genome Res. 10:258-266 (2000); Heid, C. A., et al., Genome Res. 6, 986-994 (1996). 
     Recent developments in DNA microarray technology make it possible to conduct a large scale assay of a plurality of PRLR nucleic acid molecules on a single solid phase support. U.S. Pat. No. 5,837,832 (Chee et al.) and related patent applications describe immobilizing an array of oligonucleotide probes for hybridization and detection of specific nucleic acid sequences in a sample. Target polynucleotides of interest isolated from a tissue of interest are hybridized to the DNA chip and the specific sequences detected based on the target polynucleotides&#39; preference and degree of hybridization at discrete probe locations. One important use of arrays is in the analysis of differential gene expression, where the profile of expression of genes in different cells, often a cell of interest and a control cell, is compared and any differences in gene expression among the respective cells are identified. Such information is useful for the identification of the types of genes expressed in a particular cell or tissue type and diagnosis of cancer conditions based on the expression profile. 
     Typically, RNA from the sample of interest is subjected to reverse transcription to obtain labeled cDNA. See U.S. Pat. No. 6,410,229 (Lockhart et al.) The cDNA is then hybridized to oligonucleotides or cDNAs of known sequence arrayed on a chip or other surface in a known order. The location of the oligonucleotide to which the labeled cDNA hybridizes provides sequence information on the cDNA, while the amount of labeled hybridized RNA or cDNA provides an estimate of the relative representation of the RNA or cDNA of interest. See Schena, et al Science 270:467-470 (1995). For example, use of a cDNA microarray to analyze gene expression patterns in human cancer is described by DeRisi, et al. (Nature Genetics 14:457-460 (1996)). 
     Nucleic acid probes corresponding to PRLR nucleic acids may be made. Typically, these probes are synthesized based on the disclosed PRLR gene. The nucleic acid probes attached to the biochip are designed to be substantially complementary to the PRLR nucleic acids, i.e. the target sequence (either the target sequence of the sample or to other probe sequences, for example in sandwich assays), such that specific hybridization of the target sequence and the probes of the present invention occurs. As outlined below, this complementarity need not be perfect, in that there may be any number of base pair mismatches that will interfere with hybridization between the target sequence and the single stranded nucleic acids of the present invention. It is expected that the overall homology of the genes at the nucleotide level probably will be about 40% or greater, probably about 60% or greater, and even more probably about 80% or greater; and in addition that there will be corresponding contiguous sequences of about 8-12 nucleotides or longer. However, if the number of mutations is so great that no hybridization can occur under even the least stringent of hybridization conditions, the sequence is not a complementary target sequence. Thus, by “substantially complementary” herein is meant that the probes are sufficiently complementary to the target sequences to hybridize under normal reaction conditions, particularly high stringency conditions, as outlined herein. Whether or not a sequence is unique to the PRLR gene according to this invention can be determined by techniques known to those of skill in the art. For example, the sequence can be compared to sequences in databanks, e.g., GeneBank, to determine whether it is present in the uninfected host or other organisms. The sequence can also be compared to the known sequences of other viral agents, including those that are known to induce cancer. 
     A nucleic acid probe is generally single stranded but can be partly single and partly double stranded. The strandedness of the probe is dictated by the structure, composition, and properties of the target sequence. In general, the oligonucleotide probes range from about 6, 8, 10, 12, 15, 20, 30 to about 100 bases long, with from about 10 to about 80 bases being preferred, and from about 30 to about 50 bases being particularly preferred. That is, generally entire genes are rarely used as probes. In some embodiments, much longer nucleic acids can be used, up to hundreds of bases. The probes are sufficiently specific to hybridize to complementary template sequence under conditions known by those of skill in the art. The number of mismatches between the probes sequences and their complementary template (target) sequences to which they hybridize during hybridization generally do not exceed 15%, usually do not exceed 10% and preferably do not exceed 5%, as determined by FASTA (default settings). 
     Oligonucleotide probes can include the naturally-occurring heterocyclic bases normally found in nucleic acids (uracil, cytosine, thymine, adenine and guanine), as well as modified bases and base analogues. Any modified base or base analogue compatible with hybridization of the probe to a target sequence is useful in the practice of the invention. The sugar or glycoside portion of the probe can comprise deoxyribose, ribose, and/or modified forms of these sugars, such as, for example, 2′-O-alkyl ribose. In an embodiment, the sugar moiety is 2′-deoxyribose; however, any sugar moiety that is compatible with the ability of the probe to hybridize to a target sequence can be used. 
     The nucleoside units of the probe may be linked by a phosphodiester backbone, as is well known in the art. In additional embodiments, internucleotide linkages can include any linkage known to one of skill in the art that is compatible with specific hybridization of the probe including, but not limited to phosphorothioate, methylphosphonate, sulfamate (e.g., U.S. Pat. No. 5,470,967) and polyamide (i.e., peptide nucleic acids). Peptide nucleic acids are described in Nielsen et al. (1991)  Science  254: 1497-1500, U.S. Pat. No. 5,714,331, and Nielsen (1999)  Curr. Opin. Biotechnol.  10:71-75. 
     The probe can be a chimeric molecule; i.e., can comprise more than one type of base or sugar subunit, and/or the linkages can be of more than one type within the same primer. The probe can comprise a moiety to facilitate hybridization to its target sequence, as are known in the art, for example, intercalators and/or minor groove binders. Variations of the bases, sugars, and internucleoside backbone, as well as the presence of any pendant group on the probe, will be compatible with the ability of the probe to bind, in a sequence-specific fashion, with its target sequence. A large number of structural modifications, both known and to be developed, are possible within these bounds. Advantageously, the probes according to the present invention may have structural characteristics such that they allow the signal amplification, such structural characteristics being, for example, branched DNA probes as those described by Urdea et al. (Nucleic Acids Symp. Ser., 24:197-200 (1991)) or in the European Patent No. EP-0225,807. Moreover, synthetic methods for preparing the various heterocyclic bases, sugars, nucleosides and nucleotides that form the probe, and preparation of oligonucleotides of specific predetermined sequence, are well-developed and known in the art. A method for oligonucleotide synthesis incorporates the teaching of U.S. Pat. No. 5,419,966. 
     Multiple probes may be designed for a particular target nucleic acid to account for polymorphism and/or secondary structure in the target nucleic acid, redundancy of data and the like. In some embodiments, where more than one probe per sequence is used, either overlapping probes or probes to different sections of a single target PRLR gene are used. That is, two, three, four or more probes, with three being preferred, are used to build in a redundancy for a particular target. The probes can be overlapping (i.e. have some sequence in common), or specific for distinct sequences of a PRLR gene. When multiple target polynucleotides are to be detected according to the present invention, each probe or probe group corresponding to a particular target polynucleotide is situated in a discrete area of the microarray. 
     Probes may be in solution, such as in wells or on the surface of a micro-array, or attached to a solid support. Examples of solid support materials that can be used include a plastic, a ceramic, a metal, a resin, a gel and a membrane. Useful types of solid supports include plates, beads, magnetic material, microbeads, hybridization chips, membranes, crystals, ceramics and self-assembling monolayers. An embodiment comprises a two-dimensional or three-dimensional matrix, such as a gel or hybridization chip with multiple probe binding sites (Pevzner et al., J. Biomol. Struc. &amp; Dyn. 9:399-410, 1991; Maskos and Southern, Nuc. Acids Res. 20:1679-84, 1992). Hybridization chips can be used to construct very large probe arrays that are subsequently hybridized with a target nucleic acid. Analysis of the hybridization pattern of the chip can assist in the identification of the target nucleotide sequence. Patterns can be manually or computer analyzed, but it is clear that positional sequencing by hybridization lends itself to computer analysis and automation. Algorithms and software, which have been developed for sequence reconstruction, are applicable to the methods described herein (R. Drmanac et al., J. Biomol. Struc. &amp; Dyn. 5:1085-1102, 1991; P. A. Pevzner, J. Biomol. Struc. &amp; Dyn. 7:63-73, 1989). 
     As will be appreciated by those in the art, nucleic acids can be attached or immobilized to a solid support in a wide variety of ways. By “immobilized” herein is meant the association or binding between the nucleic acid probe and the solid support is sufficient to be stable under the conditions of binding, washing, analysis, and removal as outlined below. The binding can be covalent or non-covalent. By “non-covalent binding” and grammatical equivalents herein is meant one or more of either electrostatic, hydrophilic, and hydrophobic interactions. Included in non-covalent binding is the covalent attachment of a molecule, such as streptavidin, to the support and the non-covalent binding of the biotinylated probe to the streptavidin. By “covalent binding” and grammatical equivalents herein is meant that the two moieties, the solid support and the probe, are attached by at least one bond, including sigma bonds, pi bonds and coordination bonds. Covalent bonds can be formed directly between the probe and the solid support or can be formed by a cross linker or by inclusion of a specific reactive group on either the solid support or the probe or both molecules. Immobilization may also involve a combination of covalent and non-covalent interactions. 
     Nucleic acid probes may be attached to the solid support by covalent binding such as by conjugation with a coupling agent or by, covalent or non-covalent binding such as electrostatic interactions, hydrogen bonds or antibody-antigen coupling, or by combinations thereof. Typical coupling agents include biotin/avidin, biotin/streptavidin,  Staphylococcus aureus  protein A/IgG antibody F c  fragment, and streptavidin/protein A chimeras (T. Sano and C. R. Cantor, Bio/Technology 9:1378-81 (1991)), or derivatives or combinations of these agents. Nucleic acids may be attached to the solid support by a photocleavable bond, an electrostatic bond, a disulfide bond, a peptide bond, a diester bond or a combination of these sorts of bonds. The array may also be attached to the solid support by a selectively releasable bond such as 4,4′-dimethoxytrityl or its derivative. Derivatives which have been found to be useful include 3 or 4 [bis-(4-methoxyphenyl)]-methyl-benzoic acid, N-succinimidyl-3 or 4 [bis-(4-methoxyphenyl)]-methyl-benzoic acid, N-succinimidyl-3 or 4 [bis-(4-methoxyphenyl)]-hydroxymethyl-benzoic acid, N-succinimidyl-3 or 4 [bis-(4-methoxyphenyl)]-chloromethyl-benzoic acid, and salts of these acids. 
     Probes may be attached to biochips in a wide variety of ways, as will be appreciated by those in the art. As described herein, the nucleic acids can either be synthesized first, with subsequent attachment to the biochip, or can be directly synthesized on the biochip. 
     Biochips comprise a suitable solid substrate. By “substrate” or “solid support” or other grammatical equivalents herein is meant any material that can be modified to contain discrete individual sites appropriate for the attachment or association of the nucleic acid probes and is amenable to at least one detection method. The solid phase support of the present invention can be of any solid materials and structures suitable for supporting nucleotide hybridization and synthesis. Preferably, the solid phase support comprises at least one substantially rigid surface on which the primers can be immobilized and the reverse transcriptase reaction performed. The substrates with which the polynucleotide microarray elements are stably associated may be fabricated from a variety of materials, including plastics, ceramics, metals, acrylamide, cellulose, nitrocellulose, glass, polystyrene, polyethylene vinyl acetate, polypropylene, polymethacrylate, polyethylene, polyethylene oxide, polysilicates, polycarbonates, Teflon®, fluorocarbons, nylon, silicon rubber, polyanhydrides, polyglycolic acid, polylactic acid, polyorthoesters, polypropylfumerate, collagen, glycosaminoglycans, and polyamino acids. Substrates may be two-dimensional or three-dimensional in form, such as gels, membranes, thin films, glasses, plates, cylinders, beads, magnetic beads, optical fibers, woven fibers, etc. One form of array is a three-dimensional array. One type of three-dimensional array is a collection of tagged beads. Each tagged bead has different primers attached to it. Tags are detectable by signaling means such as color (Luminex, Illumina) and electromagnetic field (Pharmaseq) and signals on tagged beads can even be remotely detected (e.g., using optical fibers). The size of the solid support can be any of the standard microarray sizes, useful for DNA microarray technology, and the size may be tailored to fit the particular machine being used to conduct a reaction of the invention. In general, the substrates allow optical detection and do not appreciably fluoresce. 
     The surface of the biochip and the probe may be derivatized with chemical functional groups for subsequent attachment of the two. Thus, for example, the biochip is derivatized with a chemical functional group including, but not limited to, amino groups, carboxy groups, oxo groups and thiol groups, with amino groups being particularly preferred. Using these functional groups, the probes can be attached using functional groups on the probes. For example, nucleic acids containing amino groups can be attached to surfaces comprising amino groups, for example using linkers as are known in the art; for example, homo- or hetero-bifunctional linkers as are well known (see 1994 Pierce Chemical Company catalog, technical section on cross-linkers, pages 155-200, incorporated herein by reference). In addition, in some cases, additional linkers, such as alkyl groups (including substituted and heteroalkyl groups) may be used. 
     The oligonucleotides may be synthesized as is known in the art, and then attached to the surface of the solid support. As will be appreciated by those skilled in the art, either the 5′ or 3′ terminus may be attached to the solid support, or attachment may be via an internal nucleoside. In an additional embodiment, the immobilization to the solid support may be very strong, yet non-covalent. For example, biotinylated oligonucleotides can be made, which bind to surfaces covalently coated with streptavidin, resulting in attachment. 
     Arrays may be produced according to any convenient methodology, such as performing the polynucleotide microarray elements and then stably associating them with the surface. Alternatively, the oligonucleotides may be synthesized on the surface, as is known in the art. 
     A number of different array configurations and methods for their production are known to those of skill in the art and disclosed in WO 95/25116 and WO 95/35505 (photolithographic techniques), U.S. Pat. No. 5,445,934 (in situ synthesis by photolithography), U.S. Pat. No. 5,384,261 (in situ synthesis by mechanically directed flow paths); and U.S. Pat. No. 5,700,637 (synthesis by spotting, printing or coupling); the disclosure of which are herein incorporated in their entirety by reference. Another method for coupling DNA to beads uses specific ligands attached to the end of the DNA to link to ligand-binding molecules attached to a bead. Possible ligand-binding partner pairs include biotin-avidin/streptavidin, or various antibody/antigen pairs such as digoxygenin-antidigoxygenin antibody (Smith et al., “Direct Mechanical Measurements of the Elasticity of Single DNA Molecules by Using Magnetic Beads,” Science 258:1122-1126 (1992)). Covalent chemical attachment of DNA to the support can be accomplished by using standard coupling agents to link the 5′-phosphate on the DNA to coated microspheres through a phosphoamidate bond. Methods for immobilization of oligonucleotides to solid-state substrates are well established. See Pease et al, Proc. Natl. Acad. Sci. USA 91(11):5022-5026 (1994). One method of attaching oligonucleotides to solid-state substrates is described by Guo et al., Nucleic Acids Res. 22:5456-5465 (1994). Immobilization can be accomplished either by in situ DNA synthesis (Maskos and Southern, Nucleic Acids Research, 20:1679-1684 (1992) or by covalent attachment of chemically synthesized oligonucleotides (Guo et al., supra) in combination with robotic arraying technologies. 
     Expression Products 
     The term “expression products” as used herein refers to both nucleic acids, including, for example, mRNA, and polypeptide products produced by transcription and/or translation of the PRLR gene. 
     The polypeptides may be in the form of a mature protein or may be a pre-, pro- or prepro-protein that can be activated by cleavage of the pre-, pro- or prepro- portion to produce an active mature polypeptide. In such polypeptides, the pre-, pro- or prepro- sequence may be a leader or secretory sequence or may be a sequence that is employed for purification of the mature polypeptide sequence. Such polypeptides are referred to as “cancer-associated polypeptides” or “PRLR polypeptides”. 
     The term “cancer-associated polypeptides” or “PRLR polypeptides” also includes variants such as fragments, homologues, fusions and mutants. Homologous polypeptides have at least 80% or more (i.e. 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99% or more) sequence identity with a PRLR polypeptide as referred to above, as determined by the Smith-Waterman homology search algorithm using an affine gap search with a gap open penalty of 12 and a gap extension penalty of 2, BLOSUM matrix of 62. The Smith-Waterman homology search algorithm is taught in Smith and Waterman,  Adv. Appl. Math . (1981) 2: 482-489. The variant polypeptides can be naturally or non-naturally glycosylated, i.e., the polypeptide has a glycosylation pattern that differs from the glycosylation pattern found in the corresponding naturally occurring protein. 
     Mutants can include amino acid substitutions, additions or deletions. The amino acid substitutions can be conservative amino acid substitutions or substitutions to eliminate non-essential amino acids, such as to alter a glycosylation site, a phosphorylation site or an acetylation site, or to minimize misfolding by substitution or deletion of one or more cysteine residues that are not necessary for function. Conservative amino acid substitutions are those that preserve the general charge, hydrophobicity/hydrophilicity, and/or steric bulk of the amino acid substituted. Variants of these products can be designed so as to retain or have enhanced biological activity of a particular region of the protein (e.g., a functional domain and/or, where the polypeptide is a member of a protein family, a region associated with a consensus sequence). Such variants may then be used in methods of detection or treatment. Selection of amino acid alterations for production of variants can be based upon the accessibility (interior vs. exterior) of the amino acid (see, e.g., Go et al,  Int. J. Peptide Protein Res . (1980) 15:211), the thermostability of the variant polypeptide (see, e.g., Querol et al.,  Prot. Eng . (1996) 9:265), desired glycosylation sites (see, e.g., Olsen and Thomsen,  J. Gen. Microbiol . (1991) 137:579), desired disulfide bridges (see, e.g., Clarke et al.,  Biochemistry  (1993) 32:4322; and Wakarchuk et al.,  Protein Eng . (1994) 7:1379), desired metal binding sites (see, e.g., Toma et al.,  Biochemistry  (1991) 30:97, and Haezerbrouck et al.,  Protein Eng . (1993) 6:643), and desired substitutions within proline loops (see, e.g., Masul et al.,  Appl. Env. Microbiol . (1994) 60:3579). Cysteine-depleted muteins can be produced as disclosed in U.S. Pat. No. 4,959,314. 
     Variants also include fragments of the polypeptides disclosed herein, particularly biologically active fragments and/or fragments corresponding to functional domains. Fragments of interest will typically be at least about 8 amino acids (aa) 10 aa, 15 aa, 20 aa, 25 aa, 30 aa, 35 aa, 40 aa, to at least about 45 aa in length, usually at least about 50 aa in length, at least about 75 aa, at least about 100 aa, at least about 125 aa, at least about 150 aa in length, at least about 200 aa, at least about 300 aa, at least about 400 aa and can be as long as 500 aa in length or longer, but will usually not exceed about 1000 aa in length, where the fragment will have a stretch of amino acids that is identical to a polypeptide encoded by a polynucleotide having a sequence of any one of the polynucleotide sequences provided herein, or a homolog thereof. The protein variants described herein are encoded by polynucleotides that are within the scope of the invention. The genetic code can be used to select the appropriate codons to construct the corresponding variants. 
     Altered levels of expression of the polypeptides encoded by the PRLR gene may indicate that the gene and its products play a role in cancers. Preferably, a two-fold increase or decrease in the amount of complex formed is indicative of disease. Even more preferably, a 3-fold, 4-fold, 5-fold, 10-fold, 20-fold, 50-fold or even 100-fold increase or decrease in the amount of complex formed is indicative of disease. 
     PRLR polypeptides may be shorter or longer than the wild type amino acid sequences, and the equivalent coding mRNAs may be similarly modified as compared to the wild type mRNA. Thus, included within the definition of PRLR polypeptides are portions or fragments of the wild type sequences herein. In addition, as outlined above, the PRLR gene may be used to obtain additional coding regions, and thus additional protein sequence, using techniques known in the art. 
     In an embodiment, the PRLR polypeptides are derivative or variant PRLR polypeptides as compared to the wild-type sequence. That is, as outlined more fully below, the derivative PRLR polypeptides will contain at least one amino acid substitution, deletion or insertion, with amino acid substitutions being particularly preferred. The amino acid substitution, insertion or deletion may occur at any residue within the PRLR polypeptides. 
     Also included are amino acid sequence variants of PRLR polypeptides. These variants fall into one or more of three classes: substitutional, insertional or deletional variants. These variants ordinarily are prepared by site-specific mutagenesis of nucleotides in the DNA encoding the PRLR protein, using cassette or PCR mutagenesis or other techniques well known in the art, to produce DNA encoding the variant, and thereafter expressing the DNA in recombinant cell culture as outlined above. However, variant PRLR polypeptide fragments having up to about 100-150 residues may be prepared by in vitro synthesis using established techniques. Amino acid sequence variants are characterized by the predetermined nature of the variation, a feature that sets them apart from naturally occurring allelic or interspecies variation of the PRLR polypeptide amino acid sequence. The variants typically exhibit the same qualitative biological activity as the naturally occurring analogue, although variants can also be selected which have modified characteristics as will be more fully outlined below. 
     While the site or region for introducing an amino acid sequence variation is predetermined, the mutation per se need not be predetermined. For example, in order to optimize the performance of a mutation at a given site, random mutagenesis may be conducted at the target codon or region and the expressed PRLR polypeptide variants screened for the optimal combination of desired activity. Techniques for making substitution mutations at predetermined sites in DNA having a known sequence are well known, for example, M13 primer mutagenesis and LAR mutagenesis. Screening of the mutants is done using assays of PRLR protein activities. 
     Amino acid substitutions are typically of single residues, though, of course may be of multiple residues; insertions usually will be on the order of from about 1 to 20 amino acids, although considerably larger insertions may be tolerated. Deletions range from about 1 to about 20 residues, although in some cases deletions may be much larger. 
     Substitutions, deletions, insertions or any combination thereof may be used to arrive at a final derivative. Generally these changes are done on a few amino acids to minimize the alteration of the molecule. However, larger changes may be tolerated in certain circumstances. When small alterations in the characteristics of the PRLR polypeptide are desired, substitutions are generally made in accordance with the following table: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Original Residue 
                 Exemplary Substitutions 
               
               
                   
                   
               
             
            
               
                   
                 Ala 
                 Ser 
               
               
                   
                 Arg 
                 Lys 
               
               
                   
                 Asn 
                 Gln, His 
               
               
                   
                 Asp 
                 Glu 
               
               
                   
                 Cys 
                 Ser 
               
               
                   
                 Gln 
                 Asn 
               
               
                   
                 Glu 
                 Asp 
               
               
                   
                 Gly 
                 Pro 
               
               
                   
                 His 
                 Asn, Gln 
               
               
                   
                 Ile 
                 Leu, Val 
               
               
                   
                 Leu 
                 Ile, Val 
               
               
                   
                 Lys 
                 Arg, Gln, Glu 
               
               
                   
                 Met 
                 Leu, Ile 
               
               
                   
                 Phe 
                 Met, Leu, Tyr 
               
               
                   
                 Ser 
                 Thr 
               
               
                   
                 Thr 
                 Ser 
               
               
                   
                 Trp 
                 Tyr 
               
               
                   
                 Tyr 
                 Trp, Phe 
               
               
                   
                 Val 
                 Ile, Leu 
               
               
                   
                   
               
            
           
         
       
     
     Substantial changes in function or immunological identity occur when substitutions are less conservative than those shown in Table 1. For example, substitutions may be made full length to more significantly affect one or more of the following: the structure of the polypeptide backbone in the area of the alteration (e.g., the alpha-helical or beta-sheet structure); the charge or hydrophobicity of the molecule at the target site; and the bulk of the side chain. The substitutions which in general are expected to produce the greatest changes in the polypeptide&#39;s properties are those in which (a) a hydrophilic residue, e.g. seryl or threonyl is substituted for (or by) a hydrophobic residue, e.g. leucyl, isoleucyl, phenylalanyl, valyl or alanyl; (b) a cysteine or proline is substituted for (or by) any other residue; (c) a residue having an electropositive side chain, e.g. lysyl, arginyl, or histidyl, is substituted for (or by) an electronegative residue, e.g. glutamyl or aspartyl; or (d) a residue having a bulky side chain, e.g. phenylalanine, is substituted for (or by) one not having a side chain, e.g. glycine. 
     The variants typically exhibit the same qualitative biological activity and will elicit the same immune response as the naturally-occurring analogue, although variants may also have modified characteristics. 
     The PRLR polypeptides may be themselves expressed and used in methods of detection and treatment. They may be further modified in order to assist with their use in such methods. 
     Covalent modifications of PRLR polypeptides may be utilised, for example in screening. One type of covalent modification includes reacting targeted amino acid residues of a PRLR polypeptide with an organic derivatizing agent that is capable of reacting with selected side chains or the N- or C-terminal residues of a PRLR polypeptide. Derivatization with bifunctional agents is useful, for instance, for crosslinking PRLR polypeptides to a water-insoluble support matrix or surface for use in the method for purifying anti-PRLR antibodies or screening assays, as is more fully described below. Commonly used crosslinking agents include, e.g., 1,1-bis(diazoacetyl)-2-phenylethane, glutaraldehyde, N-hydroxysuccinimide esters, for example, esters with 4-azidosalicylic acid, homobifunctional imidoesters, including disuccinimidyl esters such as 3,3′-dithiobis(succinimidylpropionate), bifunctional maleimides such as bis-N-maleimido-1,8-octane and agents such as methyl-3-[(p-azidophenyl)dithio]propioimidate. 
     Other modifications include deamidation of glutaminyl and asparaginyl residues to the corresponding glutamyl and aspartyl residues, respectively, hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl, threonyl or tyrosyl residues, methylation of the α-amino groups of lysine, arginine, and histidine side chains (T. E. Creighton, Proteins: Structure and Molecular Properties, W.H. Freeman &amp; Co., San Francisco, pp. 79-86 (1983)), acetylation of the N-terminal amine, and amidation of any C-terminal carboxyl group. 
     Another type of covalent modification of the PRLR polypeptide included within the scope of this invention comprises altering the native glycosylation pattern of the polypeptide. “Altering the native glycosylation pattern” is intended for purposes herein to mean deleting one or more carbohydrate moieties found in native sequence PRLR polypeptide, and/or adding one or more glycosylation sites that are not present in the native sequence PRLR polypeptide. 
     Addition of glycosylation sites to PRLR polypeptides may be accomplished by altering the amino acid sequence thereof. The alteration may be made, for example, by the addition of, or substitution by, one or more serine or threonine residues to the native sequence PRLR polypeptide (for O-linked glycosylation sites). The PRLR amino acid sequence may optionally be altered through changes at the DNA level, particularly by mutating the DNA encoding the PRLR polypeptide at preselected bases such that codons are generated that will translate into the desired amino acids. 
     Another means of increasing the number of carbohydrate moieties on the PRLR polypeptide is by chemical or enzymatic coupling of glycosides to the polypeptide. Such methods are described in the art, e.g., in WO 87/05330 published 11 Sep. 1987, and in Aplin and Wriston, L A Crit. Rev. Biochem., pp. 259-306 (1981). 
     Removal of carbohydrate moieties present on the PRLR polypeptide may be accomplished chemically or enzymatically or by mutational substitution of codons encoding for amino acid residues that serve as targets for glycosylation. Chemical deglycosylation techniques are known in the art and described, for instance, by Hakimuddin, et al., Arch. Biochem. Biophys., 259:52 (1987) and by Edge et al., Anal. Biochem., 118:131 (1981). Enzymatic cleavage of carbohydrate moieties on polypeptides can be achieved by the use of a variety of endo- and exo-glycosidases as described by Thotakura et al., Meth. Enzymol., 138:350 (1987). 
     Another type of covalent modification of PRLR comprises linking the PRLR polypeptide to one of a variety of nonproteinaceous polymers, e.g., polyethylene glycol, polypropylene glycol, or polyoxyalkylenes, in the manner set forth in U.S. Pat. No. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or 4,179,337. 
     PRLR polypeptides may also be modified in a way to form chimeric molecules comprising a PRLR polypeptide fused to another, heterologous polypeptide or amino acid sequence. In one embodiment, such a chimeric molecule comprises a fusion of a PRLR polypeptide with a tag polypeptide that provides an epitope to which an anti-tag antibody can selectively bind. The epitope tag is generally placed at the amino- or carboxyl-terminus of the PRLR polypeptide, although internal fusions may also be tolerated in some instances. The presence of such epitope-tagged forms of a PRLR polypeptide can be detected using an antibody against the tag polypeptide. Also, provision of the epitope tag enables the PRLR polypeptide to be readily purified by affinity purification using an anti-tag antibody or another type of affinity matrix that binds to the epitope tag. In an alternative embodiment, the chimeric molecule may comprise a fusion of a PRLR polypeptide with an immunoglobulin or a particular region of an immunoglobulin. For a bivalent form of the chimeric molecule, such a fusion could be to the Fc region of an IgG molecule. 
     Various tag polypeptides and their respective antibodies are well known in the art. Examples include poly-histidine (poly-his) or poly-histidine-glycine (poly-his-gly) tags; the flu HA tag polypeptide and its antibody 12CA5 (Field et al., Mol. Cell. Biol., 8:2159-2165 (1988)); the c-myc tag and the 8F9, 3C7, 6E10, G4, B7 and 9E10 antibodies thereto (Evan et al., Molecular and Cellular Biology, 5:3610-36.16 (1985)); and the Herpes Simplex virus glycoprotein D (gD) tag and its antibody (Paborsky et al., Protein Engineering, 3(6):547-553 (1990)). Other tag polypeptides include the Flag-peptide (Hopp et al., BioTechnology, 6:1204-1210 (1988)); the KT3 epitope peptide (Martin et al., Science, 255:192-194 (1992)); tubulin epitope peptide (Skinner et al., J. Biol. Chem., 266:15163-15166 (1991)); and the T7 gene 10 protein peptide tag (Lutz-Freyermuth et al., Proc. Natl. Acad. Sci. USA, 87:6393-6397 (1990)). 
     Alternatively, other PRLR proteins of the PRLR protein family, and PRLR proteins from other organisms, may be cloned and expressed as outlined below. Thus, probe or degenerate polymerase chain reaction (PCR) primer sequences may be used to find other related PRLR proteins from humans or other organisms. As will be appreciated by those in the art, particularly useful probe and/or PCR primer sequences include the unique areas of the PRLR nucleic acid sequence. As is generally known in the art, preferred PCR primers are from about 15 to about 35 nucleotides in length, with from about 20 to about 30 being preferred, and may contain inosine as needed. The conditions for the PCR reaction are well known in the art. 
     In addition, as is outlined herein, PRLR proteins can be made that are longer than those encoded by the PRLR gene, for example, by the elucidation of additional sequences, the addition of epitope or purification tags, the addition of other fusion sequences, etc. 
     PRLR proteins may also be identified as being encoded by PRLR nucleic acids. Thus, PRLR proteins are encoded by nucleic acids that will hybridize to the PRLR gene listed above, or their complements, as outlined herein. 
     Expression of PRLR Polypeptides 
     Nucleic acids derived from the PRLR gene encoding PRLR proteins may be used to make a variety of expression vectors to express PRLR proteins which can then be used in screening assays, as mentioned above. The expression, vectors may be either self-replicating extrachromosomal vectors or vectors which integrate into a host genome. Generally, these expression vectors include transcriptional and translational regulatory nucleic acid operably linked to the nucleic acid encoding the PRLR protein. The term “control sequences” refers to DNA sequences necessary for the expression of an operably linked coding sequence in a particular host organism. The control sequences that are suitable for prokaryotes, for example, include a promoter, optionally an operator sequence, and a ribosome binding site. Eukaryotic cells are known to utilize promoters, polyadenylation signals, and enhancers. 
     Nucleic acid is “operably linked” when it is placed into a functional relationship with another nucleic acid sequence. For example, DNA for a presequence or secretory leader is operably linked to DNA for a polypeptide if it is expressed as a preprotein that participates in the secretion of the polypeptide; a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to facilitate translation. Generally, “operably linked” means that the DNA sequences being linked are contiguous, and, in the case of a secretory leader, contiguous and in reading phase. However, enhancers do not have to be contiguous. Linking is accomplished by ligation at convenient restriction sites. If such sites do not exist, synthetic oligonucleotide adaptors or linkers are used in accordance with conventional practice. The transcriptional and translational regulatory nucleic acid will generally be appropriate to the host cell used to express the PRLR protein; for example, transcriptional and translational regulatory nucleic acid sequences from  Bacillus  are preferably used to express the PRLR protein in  Bacillus . Numerous types of appropriate expression vectors, and suitable regulatory sequences are known in the art for a variety of host cells. 
     In general, the transcriptional and translational regulatory sequences may include, but are not limited to, promoter sequences, ribosomal binding sites, transcriptional start and stop sequences, translational start and stop sequences, and enhancer or activator sequences In an embodiment, the regulatory sequences include a promoter and transcriptional start and stop sequences. 
     Promoter sequences encode either constitutive or inducible promoters. The promoters may be either naturally occurring promoters or hybrid promoters. Hybrid promoters, which combine elements of more than one promoter, are also known in the art, and are useful in the present invention. 
     In addition, the expression vector may comprise additional elements. For example, the expression vector may have two replication systems, thus allowing it to be maintained in two organisms, for example in mammalian or insect cells for expression and in a prokaryotic host for cloning and amplification. Furthermore, for integrating expression vectors, the expression vector contains at least one sequence homologous to the host cell genome, and preferably two homologous sequences that flank the expression construct. The integrating vector may be directed to a specific locus in the host cell by selecting the appropriate homologous sequence for inclusion in the vector. Constructs for integrating vectors are well known in the art. 
     In addition, in an embodiment, the expression vector contains a selectable marker gene to allow the selection of transformed host cells. Selection genes, including antibiotic resistance genes are well known in the art and will vary depending on the host cell used. 
     The PRLR proteins may be produced by culturing a host cell transformed with an expression vector containing nucleic acid encoding a PRLR protein, under the appropriate conditions to induce or cause expression of the PRLR protein. The conditions appropriate for PRLR protein expression will vary with the choice of the expression vector and the host cell, and will be easily ascertained by one skilled in the art through routine experimentation. For example, the use of constitutive promoters in the expression vector will require optimizing the growth and proliferation of the host cell, while the use of an inducible promoter requires the appropriate growth conditions for induction. In addition, in some embodiments, the timing of the harvest is important. For example, the baculoviral systems used in insect cell expression are lytic viruses, and thus harvest time selection can be crucial for product yield. 
     Appropriate host cells include yeast, bacteria, archaebacteria, fungi, and insect, plant and animal cells, including mammalian cells. Of particular interest are  Drosophila melanogaster  cells,  Saccharomyces cerevisiae  and other yeasts,  E. coli, Bacillus subtilis , Sf9 cells, C129 cells, 293 cells,  Neurospora , BHK, CHO, COS, HeLa cells, THP1 cell line (a macrophage cell line) and human cells and cell lines. 
     Preferably PRLR proteins are expressed in mammalian cells. Mammalian expression systems are also known in the art, and include retroviral systems. A preferred expression vector system is a retroviral vector system such as is generally described in WO97/27212 (PCT/US97/01019) and WO97/27213 (PCT/US97/01048), both of which are hereby expressly incorporated by reference. Of particular use as mammalian promoters are the promoters from mammalian viral genes, since the viral genes are often highly expressed and have a broad host range. Examples include the SV40 early promoter, mouse mammary tumor virus LTR, promoter, adenovirus major late promoter, herpes simplex virus promoter, and the CMV promoter. Typically, transcription termination and polyadenylation sequences recognized by mammalian cells are regulatory regions located 3′ to the translation stop codon and thus, together with the promoter elements, flank the coding sequence. Examples of transcription terminator and polyadenylation signals include those derived form SV40. 
     The methods of introducing exogenous nucleic acid into mammalian hosts, as well as other hosts, are well known in the art, and will vary with the host cell used. Techniques include dextran-mediated transfection, calcium phosphate precipitation, polybrene mediated transfection, protoplast fusion, electroporation, viral infection, encapsulation of the polynucleotide(s) in liposomes, and direct microinjection of the DNA into nuclei. 
     In an alternative embodiment, PRLR proteins are expressed in bacterial systems. Bacterial expression systems are well known in the art. Promoters from bacteriophage may also be used and are known in the art. In addition, synthetic promoters and hybrid promoters are also useful; for example, the tac promoter is a hybrid of the trp and lac promoter sequences. Furthermore, a bacterial promoter can include naturally occurring promoters of non-bacterial origin that have the ability to bind bacterial RNA polymerase and initiate transcription. In addition to a functioning promoter sequence, an efficient ribosome binding site is desirable. The expression vector may also include a signal peptide sequence that provides for secretion of the PRLR protein in bacteria. The protein is either secreted into the growth media (Gram-positive bacteria) or into the periplasmic space, located between the inner and outer membrane of the cell (Gram-negative bacteria). The bacterial expression vector may also include a selectable marker gene to allow for the selection of bacterial strains that have been transformed. Suitable selection genes include genes that render the bacteria resistant to drugs such as ampicillin, chloramphenicol, erythromycin, kanamycin, neomycin and tetracycline. Selectable markers also include biosynthetic genes, such as those in the histidine, tryptophan and leucine biosynthetic pathways. These components are assembled into expression vectors. Expression vectors for bacteria are well known in the art, and include vectors for  Bacillus subtilis, E. coli, Streptococcus cremoris , and  Streptococcus lividans , among others. The bacterial expression vectors are transformed into bacterial host cells using techniques well known in the art, such as calcium chloride treatment, electroporation, and others. 
     PRLR proteins may be produced in insect cells. Expression vectors for the transformation of insect cells, and in particular, baculovirus-based expression vectors, are well known in the art. 
     In a further embodiment, PRLR proteins may be produced in yeast cells. Yeast expression systems are well known in the art, and include expression vectors for  Saccharomyces cerevisiae, Candida albicans  and  C. maltosa, Hansenula polymorpha, Kluyveromyces fragilis  and  K. lactis, Pichia guillerimondii  and  P. pastoris, Schizosaccharomyces pombe , and  Yarrowia lipolytica.    
     The PRLR protein may also be made as a fusion protein, using techniques well known in the art. Thus, for example, for the creation of monoclonal antibodies. If the desired epitope is small, the PRLR protein may be fused to a carrier protein to form an immunogen. Alternatively, the PRLR protein may be made as a fusion protein to increase expression, or for other reasons. For example, when the PRLR protein is a PRLR peptide, the nucleic acid encoding the peptide may be linked to other nucleic acid for expression purposes. 
     Cancer 
     Cancers detected by the method of the invention may include, but are not limited to, cancer of the oral cavity and pharynx (lip, tongue, salivary gland, floor of mouth, gum and other mouth, nasopharynx, tonsil, oropharynx, hypopharynx, other oral/pharynx); cancers of the digestive system (esophagus; stomach; small intestine; colon and rectum; anus, anal canal, and anorectum; liver; intrahepatic bile duct; gallbladder; other biliary; pancreas; retroperitoneum; peritoneum, omentum, and mesentery; other digestive); cancers of the respiratory system (nasal cavity, middle ear, and sinuses; larynx; lung and bronchus; pleura; trachea, mediastinum, and other respiratory); cancers of the mesothelioma; bones and joints; and soft tissue, including heart; skin cancers, including melanomas and other non-epithelial skin cancers; Kaposi&#39;s sarcoma and breast cancer; cancer of the female genital system (cervix uteri; corpus uteri; uterus, nos; ovary; vagina; vulva; and other female genital); cancers of the male genital system (prostate gland; testis; penis; and other male genital); cancers of the urinary system (urinary bladder; kidney and renal pelvis; ureter; and other urinary); cancers of the eye and orbit; cancers of the brain and nervous system (brain; and other nervous system); cancers of the endocrine system (thyroid gland and other endocrine, including thymus); lymphomas (Hodgkin&#39;s disease and non-Hodgkin&#39;s lymphoma), multiple myeloma, and leukemias (lymphocytic leukemia; myeloid leukemia; monocytic leukemia; and other leukemias). 
     Other cancers, classified by histological type, include, but are not limited to, Neoplasm, malignant; Carcinoma, NOS; Carcinoma, undifferentiated, NOS; Giant and spindle cell carcinoma; Small cell carcinoma, NOS; Papillary carcinoma, NOS; Squamous cell carcinoma, NOS; Lymphoepithelial carcinoma; Basal cell carcinoma, NOS; Pilomatrix carcinoma; Transitional cell carcinoma, NOS; Papillary transitional cell carcinoma; Adenocarcinoma, NOS; Gastrinoma, malignant; Cholangiocarcinoma; Hepatocellular carcinoma, NOS; Combined hepatocellular carcinoma and cholangiocarcinoma; Trabecular adenocarcinoma; Adenoid cystic carcinoma; Adenocarcinoma in adenomatous polyp; Adenocarcinoma, familial polyposis coli; Solid carcinoma, NOS; Carcinoid tumor, malignant; Bronchiolo-alveolar adenocarcinoma; Papillary adenocarcinoma, NOS; Chromophobe carcinoma; Acidophil carcinoma; Oxyphilic adenocarcinoma; Basophil carcinoma; Clear cell adenocarcinoma, NOS; Granular cell carcinoma; Follicular adenocarcinoma, NOS; Papillary and follicular adenocarcinoma; Nonencapsulating sclerosing carcinoma; Adrenal cortical carcinoma; Endometroid carcinoma; Skin appendage carcinoma; Apocrine adenocarcinoma; Sebaceous adenocarcinoma; Ceruminous adenocarcinoma; Mucoepidermoid carcinoma; Cystadenocarcinoma, NOS; Papillary cystadenocarcinoma, NOS; Papillary serous cystadenocarcinoma; Mucinous cystadenocarcinoma, NOS; Mucinous adenocarcinoma; Signet ring cell carcinoma; Infiltrating duct carcinoma; Medullary carcinoma, NOS; Lobular carcinoma; Inflammatory carcinoma; Paget&#39;s disease, mammary; Acinar cell carcinoma; Adenosquamous carcinoma; Adenocarcinoma w/ squamous metaplasia; Thymoma, malignant; Ovarian stromal tumor, malignant; Thecoma, malignant; Granulosa cell tumor, malignant; Androblastoma, malignant; Sertoli cell carcinoma; Leydig cell tumor, malignant; Lipid cell tumor, malignant; Paraganglioma, malignant; Extra-mammary paraganglioma, malignant; Pheochromocytoma; Glomangiosarcoma; Malignant melanoma, NOS; Amelanotic melanoma; Superficial spreading melanoma; Malig melanoma in giant pigmented nevus; Epithelioid cell melanoma; Blue nevus, malignant; Sarcoma, NOS; Fibrosarcoma, NOS; Fibrous histiocytoma, malignant; Myxosarcoma; Liposarcoma, NOS; Leiomyosarcoma, NOS; Rhabdomyosarcoma, NOS; Embryonal rhabdomyosarcoma; Alveolar rhabdomyosarcoma; Stromal sarcoma, NOS; Mixed tumor, malignant, NOS; Mullerian mixed tumor; Nephroblastoma; Hepatoblastoma; Carcinosarcoma, NOS; Mesenchymoma, malignant; Brenner tumor, malignant; Phyllodes tumor, malignant; Synovial sarcoma, NOS; Mesothelioma, malignant; Dysgerminoma; Embryonal carcinoma, NOS; Teratoma, malignant, NOS; Struma ovarii, malignant; Choriocarcinoma; Mesonephroma, malignant; Hemangiosarcoma; Hemangioendothelioma, malignant; Kaposi&#39;s sarcoma; Hemangiopericytoma, malignant; Lymphangiosarcoma; Osteosarcoma, NOS; Juxtacortical osteosarcoma; Chondrosarcoma, NOS; Chondroblastoma, malignant; Mesenchymal chondrosarcoma; Giant cell tumor of bone; Ewing&#39;s sarcoma; Odontogenic tumor, malignant; Ameloblastic odontosarcoma; Ameloblastoma, malignant; Ameloblastic fibrosarcoma; Pinealoma, malignant; Chordoma; Glioma, malignant; Ependymoma, NOS; Astrocytoma, NOS; Protoplasmic astrocytoma; Fibrillary astrocytoma; Astroblastoma; Glioblastoma, NOS; Oligodendroglioma, NOS; Oligodendroblastoma; Primitive neuroectodermal; Cerebellar sarcoma, NOS; Ganglioneuroblastoma; Neuroblastoma, NOS; Retinoblastoma, NOS; Olfactory neurogenic tumor; Meningioma, malignant; Neurofibrosarcoma; Neurilemmoma, malignant; Granular cell tumor, malignant; Malignant lymphoma, NOS; Hodgkin&#39;s disease, NOS; Hodgkin&#39;s; paragranuloma, NOS; Malignant lymphoma, small lymphocytic; Malignant lymphoma, large cell, diffuse; Malignant lymphoma, follicular, NOS; Mycosis fungoides; Other specified non-Hodgkin&#39;s lymphomas; Malignant histiocytosis; Multiple myeloma; Mast cell sarcoma; Immunoproliferative small intestinal disease; Leukemia, NOS; Lymphoid leukemia, NOS; Plasma cell leukemia; Erythroleukemia; Lymphosarcoma cell leukemia; Myeloid leukemia, NOS; Basophilic leukemia; Eosinophilic leukemia; Monocytic leukemia, NOS; Mast cell leukemia; Megakaryoblastic leukemia; Myeloid sarcoma; and Hairy cell leukemia. 
     Preferably a cancer detected or treated by the methods of the invention is selected from lymphoma, leukemia, breast cancer, colon cancer, kidney cancer, liver cancer, lung cancer, ovary cancer, pancreatic cancer, prostate cancer, uterine cancer, cervical cancer or skin cancer. 
     Antibodies 
     The invention uses antibodies that bind to PRLR polypeptides expressed by the PRLR gene and preferably bind specifically to such polypeptides. The term “binds specifically” means that the antibodies have substantially greater affinity for their target PRLR polypeptide than their affinity for other related polypeptides. As used herein, the term “antibody” refers to intact molecules as well as to fragments thereof, such as Fab, F(ab′)2 and Fv, which are capable of binding to the antigenic determinant in question. Further examples of antibodies include a fully assembled antibody, monoclonal antibody, polyclonal antibody, multispecific antibody (e.g., bispecific antibody), single chain antibody, chimeric antibody, humanized antibody, human engineered antibody, human antibody, diabody, triabody, tetrabody, minibody, linear antibody, chelating recombinant antibody, an intrabody, a nanobody, a small modular immunopharmaceutical (SMIP), an antigen-binding-domain immunoglobulin fusion protein, a camelized antibody, a V HH  containing antibody, or a mutein of any one of these antibodies that comprise one, or more CDR sequences of the antibody, and recombinant peptides comprising the forgoing as long as they exhibit the desired biological activity. (e.g., binding to the extracellular domain of PRLR). By “substantially greater affinity” we mean that there is a measurable increase in the affinity for the target PRLR polypeptide of the invention as compared with the affinity for other related polypeptide. Preferably, the affinity is at least 1.5-fold, 2-fold, 5-fold 10-fold, 100-fold, 10 3 -fold, 10 4 -fold, 10 5 -fold, 10 6 -fold or greater for the target PRLR polypeptide compared to the affinity of other known homologues or orthologues. Alternatively, it might be useful for the antibody to cross react with a known homologue or orthologue. 
     Preferably, the antibodies bind to PRLR with high affinity, preferably with a dissociation constant of 10 −4 M, 10 −5 M, 10 −6 M or less, preferably 10 −7 M, 10 −8 M or less, most preferably 10 −9 M or 10 −10 M or less; subnanomolar affinity (0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1 nM or even less) is preferred. When the PRLR polypeptides are to be used to generate antibodies, for example for immunotherapy, the PRLR polypeptide should share at least one epitope or determinant with the full-length protein. By “epitope” or “determinant” herein is meant a portion of a protein that will generate and/or bind an antibody or T-cell receptor in the context of MHC. Thus, in most instances, antibodies made to a smaller PRLR polypeptide will be able to bind to the full-length protein. In an embodiment, the epitope is unique; that is, antibodies generated to a unique epitope show little or no cross-reactivity. 
     Any polypeptide sequence encoded by the PRLR gene may be analyzed to determine certain preferred regions of the polypeptide. Regions of high antigenicity are determined from data by DNASTAR analysis by choosing values that represent regions of the polypeptide that are likely to be exposed on the surface of the polypeptide in an environment in which antigen recognition may occur in the process of initiation of an immune response. For example, the amino acid sequence of a polypeptide encoded by the PRLR gene sequence may be analyzed using the default parameters of the DNASTAR computer algorithm (DNASTAR, Inc., Madison, Wis.; see the worldwideweb site at dnastar.com). 
     Polypeptide features that may be routinely obtained using the DNASTAR computer algorithm include, but are not limited to, Garnier-Robson alpha-regions, beta-regions, turn-regions, and coil-regions (Garnier et al.  J. Mol. Biol.,  120: 97 (1978)); Chou-Fasman alpha-regions, beta-regions, and turn-regions ( Adv. in Enzymol.,  47:45-148 (1978)); Kyte-Doolittle hydrophilic regions and hydrophobic regions ( J. Mol. Biol.,  157:105-132 (1982)); Eisenberg alpha- and beta-amphipathic regions; Karplus-Schuilz flexible regions; Emini surface-forming regions ( J. Virol.,  55(3):836-839 (1985)); and Jameson-Wolf regions of high antigenic index ( CABIOS,  4(1):181-186 (1988)). Kyte-Doolittle hydrophilic regions and hydrophobic regions, Emini surface-forming regions, and Jameson-Wolf regions of high antigenic index (i.e., containing four or more contiguous amino acids having an antigenic index of greater than or equal to 1.5, as identified using the default parameters of the Jameson-Wolf program) can routinely be used to determine polypeptide regions that exhibit a high degree of potential for antigenicity. One approach for preparing antibodies to a protein is the selection and preparation of an amino acid sequence of all or part of the protein, chemically synthesizing the sequence and injecting it into an appropriate animal, typically a rabbit, hamster or a mouse. Oligopeptides can be selected as candidates for the production of an antibody to the PRLR protein based upon the oligopeptides lying in hydrophilic regions, which are thus likely to be exposed in the mature protein. Additional oligopeptides can be determined using, for example, the Antigenicity Index, Welling, G. W. et al.,  FEBS Lett.  188:215-218 (1985), incorporated herein by reference. 
     The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Furthermore, in contrast to conventional (polyclonal) antibody preparations that are typically include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they are synthesized by the homogeneous culture, uncontaminated by other immunoglobulins with different specificities and characteristics. 
     The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybridoma method first described by Kohler et al., Nature, 256:495 [19751, or may be made by recombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567). The “monoclonal antibodies” may also be isolated from phage antibody libraries using the techniques described in Clackson et al., Nature, 352:624628[1991] end Marks et al., J. Mol. Biol., 222:581-597 (1991), for example. 
     Depending on the amino acid sequence of the constant domain of their heavy chains, immunoglobulins can be assigned to different classes. There are five major classes, IgA, IgD, IgE, IgG and IgM, and several of these may be further divided into subclasses or isotypes, e.g. IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2. The heavy-chain constant domains that correspond to the different classes of immunoglobulins are called alpha, delta, epsilon, gamma and mu respectively. The subunit structures and three-dimensional configurations of different classes of immunoglobulins are well known. Different isotypes have different effector functions; for example, IgG1 and IgG3 isotypes have ADCC activity. 
     “Antibody fragments” comprise a portion of an intact full length antibody, preferably the antigen binding or variable region of the intact antibody. Examples of antibody fragments include Fab, Fab′, F(ab′)2, and Fv fragments; diabodies; linear antibodies (Zapata et al., Protein Eng., 8(10): 1057-1062 (1995)); single-chain antibody molecules; and multispecific antibodies formed from antibody fragments. Papain digestion of antibodies produces two identical antigen-binding fragments, called “Fab” fragments, each with a single antigen-binding site, and a residual “Fc” fragment, whose name reflects its ability to crystallize readily. Pepsin treatment yields an F(ab′)2 fragment that has two “Single-chain Fv” or “sFv” antibody fragments comprise the VH and VL domains of antibody, wherein these domains are present in a single polypeptide chain. Preferably, the Fv polypeptide further comprises a polypeptide linker between the VH and VL domains that enables the Fv to form the desired structure for antigen binding. For a review of sFv see Pluckthun in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994). 
     The term “hypervariable” region refers to the amino acid residues of an antibody which are responsible for antigen-binding. The hypervariable region comprises amino acid residues from a complementarity determining region or CDR, [i.e., residues 24-34 (L), 50-56 (L2) and 89-97 (L3) in the light chain variable domain and 31-35 (H1), 50-65 (H2) and 95-102 (H3) in the heavy chain variable domain as described by Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991)] and/or those residues from a hypervariable loop (i.e., residues 26-32 (L1), 50-52 (L2) and 91-96 (L3) in the light chain variable domain and 26-32 (H1), 53-55 (H2) and 96-101 (H3) in the heavy chain variable domain as described by [Chothia et al., J. Mol. Biol. 196: 901-917 (1987)]. 
     “Framework” or FR residues are those variable domain residues other than the hypervariable region residues. 
     Polyclonal Antibodies 
     Methods of preparing polyclonal antibodies are known to the skilled artisan. Polyclonal antibodies can be raised in a mammal, for example, by one or more injections of an immunizing agent and, if desired, an adjuvant. Typically, the immunizing agent and/or adjuvant will be injected in the mammal by multiple subcutaneous or intraperitoneal injections. The immunizing agent may include a protein encoded by a nucleic acid of the figures or fragment thereof or a fusion protein thereof. It may be useful to conjugate the immunizing agent to a protein known to be immunogenic in the mammal being immunized. Examples of such immunogenic proteins include but are not limited to keyhole limpet hemocyanin, serum albumin, bovine thyroglobulin, and soybean trypsin inhibitor. Examples of adjuvants that may be employed include Freund&#39;s complete adjuvant and MPL-TDM adjuvant (monophosphoryl Lipid A, synthetic trehalose dicorynomycolate). The immunization protocol may be selected by one skilled in the art without undue experimentation. 
     Monoclonal Antibodies 
     Preferably the antibodies are monoclonal antibodies. Monoclonal antibodies may be prepared using hybridoma methods, such as those described by Kohler and Milstein,  Nature,  256:495 (1975). In a hybridoma method, a mouse, hamster, or other appropriate host animal, is typically immunized with an immunizing agent to elicit lymphocytes that produce or are capable of producing antibodies that will specifically bind to the immunizing agent. Alternatively, the lymphocytes may be immunized in vitro. The immunizing agent will typically include a PRLR polypeptide, or fragment thereof or a fusion protein thereof. Generally, either peripheral blood lymphocytes (“PBLs”) are used if cells of human origin are desired, or spleen cells or lymph node cells are used if non-human mammalian sources are desired. The lymphocytes are then fused with an immortalized cell line using a suitable fusing agent, such as polyethylene glycol, to form a hybridoma cell (Goding, Monoclonal Antibodies: Principles and Practice, Academic Press, (1986) pp. 59-103). Immortalized cell lines are usually transformed mammalian cells, particularly myeloma cells of rodent, bovine and human origin. Usually, rat or mouse myeloma cell lines are employed. The hybridoma cells may be cultured in a suitable culture medium that preferably contains one or more substances that inhibit the growth or survival of the unfused, immortalized cells. For example, if the parental cells lack the enzyme hypoxanthine guanine phosphoribosyl transferase (HGPRT or HPRT), the culture medium for the hybridomas typically will include hypoxanthine, aminopterin, and thymidine (“HAT medium”), which substances prevent the growth of HGPRT-deficient cells. Monoclonal antibody technology is used in implementing research, diagnosis and therapy. Monoclonal antibodies are used in radioimmunoassays, enzyme-linked immunosorbent assays, immunocytopathology, and flow cytometry for in vitro diagnosis, and in vivo for diagnosis and immunotherapy of human disease. Waldmann, T. A. (1991)  Science  252:1657-1662. In particular, monoclonal antibodies have been widely applied to the diagnosis and therapy of cancer, wherein it is desirable to target malignant lesions while avoiding normal tissue. See, e.g., U.S. Pat. Nos. 4,753,894 to Frankel, et al.; 4,938,948 to Ring et al.; and 4,956,453 to Bjorn et al. 
     Antibody Fragments 
     The antibodies may be bispecific antibodies. In the present caseterm “antibody” as used herein includes antibody fragments, as are known in the art, including Fab, Fab′, F(ab′)2, and Fv fragments; diabodies; linear antibodies; single-chain antibody molecules; multispecific antibodies such as bispecific, trispecific, etc. antibodies; minibody; chelating recombinant antibody; tribodies; bibodies; intrabodies; nanobodies; small modular immunopharmaceuticals (SMIP), binding-domain immunoglobulin fusion proteins; camelized antibodies; VHH containing antibodies, chimeric antibodies, etc., and other polypeptides formed from antibody fragments either produced by the modification of whole antibodies or those synthesized de novo using recombinant DNA technologies. 
     The term “diabodies” refers to small antibody fragments with two antigen-binding sites, which fragments comprise a heavy-chain variable domain (VH) connected to a light-chain variable domain (VL) in the same polypeptide chain (VH VL). By using a linker that is too short to allow pairing between the two domains on the same chain, the domains are forced to pair with the complementary domains of another chain and create two antigen-binding sites. Diabodies are described more fully in, for example, EP 404,097; WO 93/11161; and 30 Hollinger et al., Proc. Natl. Acad. Sci. USA, 90:6444-6448 (1993). 
     Papain digestion of antibodies produces two identical antigen-binding fragments, called “Fab” fragments, monovalent fragments consisting of the VL, VH, CL and CH domains each with a single antigen-binding site, and a residual “Fc” fragment, whose name reflects its ability to crystallize readily. Pepsin treatment yields a F(ab′)2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region, that has two “Single-chain Fv” or “scFv” antibody fragments comprise the VH and VL domains of antibody, wherein these domains are present in a single polypeptide chain. Preferably, the Fv polypeptide further comprises a polypeptide linker between the VH and VL domains that enables the Fv to form the desired structure for antigen binding, resulting in a single-chain antibody (scFv), in which a VL and VH region are paired to form a monovalent molecule via a synthetic linker that enables them to be made as a single protein chain (Bird et al., Science 242:423-426, 1988, and Huston et al., Proc. Natl. Acad. Sci. USA 85:5879-5883, 1988). For a review of sFv see Pluckthun, in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994). An Fd fragment consists of the VH and CH1 domains. 
     Additional antibody fragment include a domain antibody (dAb) fragment (Ward et al., Nature 341:544-546, 1989) which consists of a VH domain. 
     “Linear antibodies” comprise a pair of tandem Fd segments (VH-CH1-VH-CH1) which form a pair of antigen binding regions. Linear antibodies can be bispecific or monospecific (Zapata et al. Protein Eng. 8:1057-62 (1995)). 
     A “minibody” consisting of scFv fused to CH3 via a peptide linker (hingeless) or via an IgG hinge has been described in Olafsen, et al., Protein Eng Des Sel. 2004 April; 17(4):315-23. 
     Functional heavy-chain antibodies devoid of light chains are naturally occurring in nurse sharks (Greenberg et al., Nature 374:168-73, 1995), wobbegong sharks (Nuttall et al., Mol. Immunol. 38:313-26, 2001) and Camelidae (Hamers-Casterman et al., Nature 363: 446-8, 1993; Nguyen et al., J. Mol. Biol. 275: 413, 1998), such as camels, dromedaries, alpacas and llamas. The antigen-binding site is reduced to a single domain, the VHH domain, in these animals. These antibodies form antigen-binding regions using only heavy chain variable region, i.e., these functional antibodies are homodimers of heavy chains only having the structure H2L2 (referred to as “heavy-chain antibodies” or “HCAbs”). Camelized VHH reportedly recombines with IgG2 and IgG3 constant regions that contain hinge, CH 2 , and CH3 domains and lack a CH1 domain (Hamers-Casterman et al., supra). For example, llama IgG1 is a conventional (H2L2) antibody isotype in which VH recombines with a constant region that contains hinge, CH1, CH2 and CH3 domains, whereas the llama IgG2 and IgG3 are heavy chain-only isotypes that lack CH1 domains and that contain no light chains. Classical VH-only fragments are difficult to produce in soluble form, but improvements in solubility and specific binding can be obtained when framework residues are altered to be more VHH-like. (See, e.g., Reichman, et al., 
     J Immunol Methods 1999, 231:25-38.) Camelized VHH domains have been found to bind to antigen with high affinity (Desmyter et al., J. Biol. Chem. 276:26285-90, 2001) and possess high stability in solution (Ewert et al., Biochemistry 41:3628-36, 2002). Methods for generating antibodies having camelized heavy chains are described in, for example, in U.S. Patent Publication Nos. 20050136049 and 20050037421. 
     Because the variable domain of the heavy-chain antibodies is the smallest fully functional antigen-binding fragment with a molecular mass of only 15 kDa, this entity is referred to as a nanobody (Cortez-Retamozo et. al., Cancer Research 64:2853-57, 2004). A nanobody library may be generated from an immunized dromedary as described in Conrath et al., (Antimicrob Agents Chemother 45: 2807-12, 2001) or using recombinant methods as described in Production of bispecific Fab-scFv (“bibody”) and trispecific Fab-(scFv)(2) (“tribody”) are described in Schoonjans et al. (J. Immunol. 165:7050-57, 2000) and Willems et al. (J Chromatogr B Analyt Technol Biomed Life Sci. 786:161-76, 2003). For bibodies or tribodies, a scFv molecule is fused to one or both of the VL-CL (L) and VH-CH1 (Fd) chains, e.g., to produce a tribody two scFvs are fused to C-term of Fab while in a bibody one scFv is fused to C-term of Fab. 
     Intrabodies are single chain antibodies which demonstrate intracellular expression and can manipulate intracellular protein function (Biocca, et al., EMBO J. 9:101-108, 1990; Colby et al., Proc Natl Acad Sci USA. 101:17616-21, 2004). Intrabodies, which comprise cell signal sequences which retain the antibody contruct in intracellular regions, may be produced as described in Mhashilkar et al (EMBO J. 14:1542-51, 1995) and Wheeler et al. (FASEB J. 17:1733-5. 2003). Transbodies are cell-permeable antibodies in which a protein transduction domains (PTD) is fused with single chain variable fragment (scFv) antibodies Heng et al., (Med Hypotheses. 64:1105-8, 2005). 
     Further contemplated are antibodies that are SMlPs or binding domain immunoglobulin fusion proteins specific for target protein. These constructs are single-chain polypeptides comprising antigen binding domains fused to immunoglobulin domains necessary to carry out antibody effector functions. See e.g., WO03/041600, U.S. Patent publication 20030133939 and US Patent Publication 20030118592. 
     Multispecific Antibodies 
     In some embodiments, it may be desirable to generate a multispecific (e.g. bispecific, trispecific, etc.) monoclonal antibody having binding specificities for at least two different epitopes. Exemplary bispecific antibodies may bind to two different epitopes of PRLR. Alternatively, an anti-PRLR arm may be combined with an arm which binds to a triggering molecule on a leukocyte such as a T-cell receptor molecule (e.g., CD2 or CD3), or Fc receptors for IgG (FcγR), such as FcγRI (CD64), FcγRII (CD32) and FcγRIII (CD16) so as to focus cellular defense mechanisms to the PRLR-expressing cell. 
     In another example, one of the binding specificities is for a PRLR polypeptide, PRLR or a fragment thereof, the other one is for any other antigen, e.g., a cell-surface protein or receptor or receptor subunit, preferably one that is tumor specific or tissue specific. Examples include a skin cancer specific antigen, a lung cancer specific antigen, a breast cancer specific antigen, or a prostate cancer specific antigen. 
     Bispecific antibodies may also be used to localize cytotoxic agents to cells which express PRLR. These antibodies possess a PRLR-binding arm and an arm which binds the cytotoxic agent (e.g., saporin, anti-interferon-60, vinca alkaloid, ricin A chain, methotrexate or radioactive isotope hapten). Bispecific antibodies can be prepared as full length antibodies or antibody fragments. 
     According to another approach for making bispecific antibodies, the interface between a pair of antibody molecules can be engineered to maximize the percentage of heterodimers which are recovered from recombinant cell culture. The preferred interface comprises at least a part of the CH3 domain of an antibody constant domain. In this method, one or more small amino acid side chains from the interface of the first antibody molecule are replaced with larger side chains (e.g., tyrosine or tryptophan). Compensatory “cavities” of identical or similar size to the large side chain(s) are created on the interface of the second antibody molecule by replacing large amino acid side chains with smaller ones (e.g., alanine or threonine). This provides a mechanism for increasing the yield of the heterodimer over other unwanted end-products such as homodimers. See WO96/27011 published Sep. 6, 1996. 
     Bispecific antibodies include cross-linked or “heteroconjugate” antibodies. For example, one of the antibodies in the heteroconjugate can be coupled to avidin, the other to biotin. Heteroconjugate antibodies may be made using any convenient cross-linking methods. Suitable cross-linking agents are well known in the art, and are disclosed in U.S. Pat. No. 4,676,980, along with a number of cross-linking techniques. 
     Techniques for generating bispecific antibodies from antibody fragments have also been described in the literature. For example, bispecific antibodies can be prepared using chemical linkage. Brennan et al., Science 229:81 (1985) describe a procedure wherein intact antibodies are proteolytically cleaved to generate F(ab′)2 fragments. These fragments are reduced in the presence of the dithiol complexing agent sodium arsenite to stabilize vicinal dithiols and prevent intermolecular disulfide formation. The Fab′ fragments generated are then converted to thionitrobenzoate (TNB) derivatives. One of the Fab′-TNB derivatives is then reconverted to the Fab′-thiol by reduction with mercaptoethylamine and is mixed with an equimolar amount of the other Fab′-TNB derivative to form the bispecific antibody. The bispecific antibodies produced can be used as agents for the selective immobilization of enzymes. In yet a further embodiment, Fab′-SH fragments directly recovered from  E. coli  can be chemically coupled in vitro to form bispecific antibodies. (Shalaby et al., J. Exp. Med. 175:217-225 (1992)) 
     Shalaby et al., J. Exp. Med. 175:217-225 (1992) describe the production of a fully humanized bispecific antibody F(ab′)2 molecule. Each Fab′ fragment was separately secreted from  E. coli  and subjected to directed chemical coupling in vitro to form the bispecific antibody. The bispecific antibody thus formed was able to bind to cells overexpressing the HER2 receptor and normal human T cells, as well as trigger the lytic activity of human cytotoxic lymphocytes against human breast tumor targets. 
     Various techniques for making and isolating bispecific antibody fragments directly from recombinant cell culture have also been described. For example, bispecific antibodies have been produced using leucine zippers. (Kostelny et al., J. Immunol. 148(5):1547-1553 (1992)) The leucine zipper peptides from the Fos and Jun proteins were linked to the Fab′ portions of two different antibodies by gene fusion. The antibody homodimers were reduced at the hinge region to form monomers and then re-oxidized to form the antibody heterodimers. This method can also be utilized for the production of antibody homodimers. The “diabody” technology described by Hollinger et al., Proc. Natl. Acad. Sci. USA 90:6444-6448 (1993) has provided an alternative mechanism for making bispecific antibody fragments. 
     The fragments comprise a heavy chain variable region (VH) connected to a light-chain variable region (VL) by a linker which is too short to allow pairing between the two domains on the same chain. Accordingly, the VH and VL domains of one fragment are forced to pair with the complementary VL and VH domains of another fragment, thereby forming two antigen-binding sites. Another strategy for making bispecific antibody fragments by the use of single-chain Fv (sFv) dimers has also been reported. See Gruber et al., J. Immunol. 152: 5368 (1994). 
     Alternatively, the bispecific antibody may be a “linear antibody” produced as described in Zapata et al. Protein Eng. 8(10):1057-1062 (1995). Briefly, these antibodies comprise a pair of tandem Fd segments (VH-CH1-VH-CH1) which form a pair of antigen binding regions. Linear antibodies can be bispecific or monospecific. 
     Antibodies with more than two valencies are also contemplated. For example, trispecific antibodies can be prepared. (Tutt et al., J. Immunol. 147:60 (1991))A “chelating recombinant antibody” is a bispecific antibody that recognizes adjacent and non-overlapping epitopes of the target antigen, and is flexible enough to bind to both epitopes simultaneously (Neri et al., J Mol. Biol. 246:367-73, 1995). 
     In another embodiment, the antibodies to PRLR polypeptides are capable of reducing or eliminating the biological function of PRLR polypeptides, as is described below. That is, the addition of anti-PRLR polypeptide antibodies (either polyclonal or preferably monoclonal) to PRLR polypeptides (or cells containing PRLR polypeptides) may reduce or eliminate the PRLR polypeptide activity. Generally, at least a 25% decrease in activity is preferred, with at least about 50% being particularly preferred and about a 95-100% decrease being especially preferred. 
     Recombinant Production of Antibodies 
     For recombinant production of the antibody, the nucleic acid encoding it is isolated and inserted into a replicable vector for further cloning (amplification of the DNA) or for expression. DNA encoding the monoclonal antibody is readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of the antibody). Many vectors are available. The vector components generally include, but are not limited to, one or more of the following: a signal sequence, an origin of replication, one or more selective marker genes, an enhancer element, a promoter, and a transcription termination sequence, examples of which are well known in the art. 
     A variety of heterologous systems is available for functional expression of recombinant polypeptides that are well known to those skilled in the art. Such systems include bacteria (Strosberg, et al., Trends in Pharmacological Sciences (1992) 13:95-98), yeast (Pausch, Trends in Biotechnology (1997) 15:487-494), several kinds of insect cells (Vanden Broeck, Int. Rev. Cytology (1996) 164:189-268), amphibian cells (Jayawickreme et al., Current Opinion in Biotechnology (1997) δ: 629-634) and several mammalian cell lines (CHO, HE 93, COS, etc.; see Gerhardt, et al., Eur. J. Pharmacology (1997) 334:1-23). These examples do not preclude the use of other possible cell expression systems, including cell lines obtained from nematodes (PCT application WO 98/37177). 
     Chimeric, Humanized, Human Engineered™ and Human Antibodies 
     A rodent antibody on repeated in vivo administration in man either alone or as a conjugate will bring about an immune response in the recipient against the rodent antibody; the so-called HAMA response (Human Anti Mouse Antibody). The HAMA response may limit the effectiveness of the pharmaceutical if repeated dosing is required. The immunogenicity of the antibody may be reduced by chemical modification of the antibody with a hydrophilic polymer such as polyethylene glycol or by using the methods of genetic engineering to make the antibody binding structure more human like. 
     In an embodiment the antibodies to the PRLR polypeptides are humanized or chimeric antibodies. “Humanized” antibodies refer to a molecule having an antigen binding site that is substantially derived from an immunoglobulin from a non-human species and the remaining immunoglobulin structure of the molecule based upon the structure and/or sequence of a human immunoglobulin. The antigen binding site may comprise either complete variable domains fused onto constant domains or only the complementarity determining regions (CDRs) grafted onto appropriate framework regions in the variable domains. Antigen binding sites may be wild type or modified by one or more amino acid substitutions, e.g., modified to resemble human immunoglobulin more closely. Alternatively, a humanized antibody may be derived from a chimeric antibody that retains or substantially retains the antigen-binding properties of the parental, non-human, antibody but which exhibits diminished immunogenicity as compared to the parental antibody when administered to humans. The phrase “chimeric antibody,” as used herein, refers to an antibody containing sequence derived from two different antibodies (see, e.g., U.S. Pat. No. 4,816,567) that typically originate from different species. Typically, in these chimeric antibodies, the variable region of both light and heavy chains mimics the variable regions of antibodies derived from one species of mammals, while the constant portions are homologous to the sequences in antibodies derived from another. Most typically, chimeric antibodies comprise human and murine antibody fragments, generally human constant and mouse variable regions. Chimeric monoclonal antibodies, in which the variable Ig domains of a rodent monoclonal antibody are fused to human constant Ig domains, can be generated using standard procedures known in the art (See Morrison, S. L., et al. (1984) Chimeric Human Antibody Molecules; Mouse Antigen Binding Domains with Human Constant Region Domains, Proc. Natl. Acad. Sci. USA 81, 6841-6855; and, Boulianne, G. L., et al, Nature 312, 643-646. (1984)). Although some chimeric monoclonal antibodies have proved less immunogenic in humans, the mouse variable Ig domains can still lead to a significant human anti-mouse response. 
     Humanized antibodies are made by replacing the complementarity determining regions (CDRs) of a human antibody (acceptor antibody) with those from a non-human antibody (donor antibody) such as mouse, rat or rabbit having the desired specificity, affinity and capacity. In some instances, Fv framework residues of the human “acceptor” antibody are replaced by corresponding non-human residues from the “donor” antibody. Humanized antibodies may also comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. In general, the humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the CDR regions correspond to those of a non-human immunoglobulin and all or substantially all of the framework residues (FR) regions are those of a human immunoglobulin consensus sequence. The humanized antibody optimally also will comprise at least a portion of an immunoglobulin constant region (Fc), typically that of a human immunoglobulin (Jones et al.,  Nature,  321:522-525 (1986); Riechmann et al.,  Nature,  332:323-329 (1988); and Presta,  Curr. Op. Struct. Biol.,  2:593-596 (1992)). One clear advantage to such chimeric forms is that, for example, the variable regions can conveniently be derived from presently known sources using readily available hybridomas or B cells from non human host organisms in combination with constant regions derived from, for example, human cell preparations. While the variable region has the advantage of ease of preparation, and the specificity is not affected by its source, the constant region being human, is less likely to elicit an immune response from a human subject when the antibodies are injected than would the constant region from a non-human source. However, the definition is not limited to this particular example. 
     Because humanized antibodies are far less immunogenic in humans than the parental mouse monoclonal antibodies, they can be used for the treatment of humans with far less risk of anaphylaxis. Thus, these antibodies may be preferred in therapeutic applications that involve in vivo administration to a human such as, e.g., use as radiation sensitizers for the treatment of neoplastic disease or use in methods to reduce the side effects of, e.g., cancer therapy. Methods for humanizing non-human antibodies are well known in the art. Generally, a humanized antibody has one or more amino acid residues introduced into it from a source that is non-human. These non-human amino acid residues are often referred to as import residues, which are typically taken from an import variable domain. Humanization can be essentially performed following the method of Winter and co-workers (Jones et al.,  Nature  321:522-525 (1986); Riechmann et al.,  Nature  332:323-327 (1988); Verhoeyen et al.,  Science  239:1534-1536 (1988)), by substituting rodent CDRs or CDR sequences for the corresponding sequences of a human antibody. Accordingly, such humanized antibodies are chimeric antibodies (U.S. Pat. No. 4,816,567), wherein substantially less than an intact human variable domain has been substituted by the corresponding sequence from a non-human species. In practice, humanized antibodies are typically human antibodies in which some CDR residues and possibly some FR residues are substituted by residues from analogous sites in rodent antibodies. 
     A disadvantage of CDR grafting, however, is that it can result in a humanized antibody that has a substantially lower binding affinity than the original mouse antibody, because amino acids of the framework regions can contribute to antigen binding, and because amino acids of the CDR loops can influence the association of the two variable Ig domains. To maintain the affinity of the humanized monoclonal antibody, the CDR grafting technique can be improved by choosing human framework regions that most closely resemble the framework regions of the original mouse antibody, and by site-directed mutagenesis of single amino acids within the framework or CDRs aided by computer modeling of the antigen binding site (e.g., Co, M. S., et al. (1994), J. Immunol. 152, 2968-2976). 
     One method of humanizing antibodies comprises aligning the non-human heavy and light chain sequences to human heavy and light chain sequences, selecting and replacing the non-human framework with a human framework based on such alignment, molecular modeling to predict the conformation of the humanized sequence and comparing to the conformation of the parent antibody. This process is followed by repeated back mutation of residues in the CDR region which disturb the structure of the CDRs until the predicted conformation of the humanized sequence model closely approximates the conformation of the non-human CDRs of the parent non-human antibody. 
     A number of “humanized” antibody molecules comprising an antigen-binding site derived from a non-human immunoglobulin have been described, including chimeric antibodies having rodent V regions and their associated CDRs fused to human constant domains (Winter et al. (1991)  Nature  349:293-299; Lobuglio et al. (1989)  Proc. Nat. Acad. Sci. USA  86:4220-4224; Shaw et al. (1987)  J Immunol.  138:4534-4538; and Brown et al. (1987)  Cancer Res.  47:3577-3583), rodent CDRs grafted into a human supporting FR prior to fusion with an appropriate human antibody constant domain (Riechmann et al. (1988)  Nature  332:323-327; Verhoeyen et al. (1988)  Science  239:1534-1536; and Jones et al. (1986)  Nature  321:522-525), and rodent CDRs supported by recombinantly veneered rodent FRs (European Patent Publication No. 519,596, published Dec. 23, 1992). 
     Humanized antibodies may be achieved by a variety of methods including, for example: (1) grafting the nonhuman complementarity determining regions (CDRs) onto a human framework and constant region (a process referred to in the art as “humanizing”), or, alternatively, (2) transplanting the entire non-human variable domains, but “cloaking” them with a human-like surface by replacement of surface residues (a process referred to in the art as “veneering”). In the present invention, humanized antibodies will include both “humanized” and “veneered” antibodies. Similarly, human antibodies can be made by introducing human immunoglobulin loci into transgenic animals, e.g., mice in which the endogenous immunoglobulin genes have been partially or completely inactivated. Upon challenge, human antibody production is observed, which closely resembles that seen in humans in all respects, including gene rearrangement, assembly, and antibody repertoire. This approach is described, for example, in U.S. Pat. Nos. 5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; 5,661,016, and in the following scientific publications: Marks et al.,  Bio/Technology  10, 779-783 (1992); Lonberg et al.,  Nature  368 856-859 (1994); Morrison,  Nature  368, 812-13 (1994); Fishwild et al.,  Nature Biotechnology  14, 845-51 (1996); Neuberger,  Nature Biotechnology  14, 826 (1996); Lonberg and Huszar,  Intern. Rev. Immunol.  13 65-93 (1995); Jones et al.,  Nature  321:522-525 (1986); Morrison et al.,  Proc. Natl. Acad. Sci, U.S.A.,  81:6851-6855 (1984); Morrison and Oi,  Adv. Immunol.,  44:65-92 (1988); Verhoeyer et al.,  Science  239:1534-1536 (1988); Padlan,  Molec. Immunol.  28:489-498 (1991); Padlan,  Molec. Immunol.  31(3):169-217 (1994); and Kettleborough, C. A. et al.,  Protein Eng.  4(7):773-83 (1991) each of which is incorporated herein by reference. 
     The phrase “complementarity determining region” refers to amino acid sequences which together define the binding affinity and specificity of the natural Fv region of a native immunoglobulin binding site. See, e.g., Chothia et al.,  J. Mol. Biol.  196:901-917 (1987); Kabat et al., U.S. Dept. of Health and Human Services NIH Publication No. 91-3242 (1991). The phrase “constant region” refers to the portion of the antibody molecule that confers effector functions. In the present invention, mouse constant regions are substituted by human constant regions. The constant regions of the subject humanized antibodies are derived from human immunoglobulins. The heavy chain constant region can be selected from any of the five isotypes: alpha, delta, epsilon, gamma or mu. One method of humanizing antibodies comprises aligning the non-human heavy and light chain sequences to human heavy and light chain sequences, selecting and replacing the non-human framework with a human framework based on such alignment, molecular modeling to predict the conformation of the humanized sequence and comparing to the conformation of the parent antibody. This process is followed by repeated back mutation of residues in the CDR region that disturb the structure of the CDRs until the predicted conformation of the humanized sequence model closely approximates the conformation of the non-human CDRs of the parent non-human antibody. Such humanized antibodies may be further derivatized to facilitate uptake and clearance, e.g, via Ashwell receptors. See, e.g., U.S. Pat. Nos. 5,530,101 and 5,585,089 which are incorporated herein by reference. 
     Human Engineering™ 
     Human Engineering™ of antibody variable domains has been described by Studnicka [See, e.g., Studnicka et al. U.S. Pat. No. 5,766,886; Studnicka et al. Protein Engineering 7: 805-814 (1994)] as a method for reducing immunogenicity while maintaining binding activity of antibody molecules. According to the method, each variable region amino acid has been assigned a risk of substitution. Amino acid substitutions are distinguished by one of three risk categories: (1) low risk changes are those that have the greatest potential for reducing immunogenicity with the least chance of disrupting antigen binding; (2) moderate risk changes are those that would further reduce immunogenicity, but have a greater chance of affecting antigen binding or protein folding; (3) high risk residues are those that are important for binding or for maintaining antibody structure and carry the highest risk that antigen binding or protein folding will be affected. Due to the three-dimensional structural role of prolines, modifications at prolines are generally considered to be at least moderate risk changes, even if the position is typically a low risk position. 
     Variable regions of the light and heavy chains of a rodent antibody are Human Engineered™ as follows to substitute human amino acids at positions determined to be unlikely to adversely effect either antigen binding or protein folding, but likely to reduce immunogenicity in a human environment. Amino acid residues that are at “low risk” positions and that are candidates for modification according to the method are identified by aligning the amino acid sequences of the rodent variable regions with a human variable region sequence. Any human variable region can be used, including an individual VH or VL sequence or a human consensus VH or VL sequence or an individual or consensus human germline sequence. The amino acid residues at any number of the low risk positions, or at all of the low risk positions, can be changed. For example, at each low risk position where the aligned murine and human amino acid residues differ, an amino acid modification is introduced that replaces the rodent residue with the human residue. Alternatively, the amino acid residues at all of the low risk positions and at any number of the moderate risk positions can be changed. Ideally, to achieve the least immunogenicity all of the low and moderate risk positions are changed from rodent to human sequence. 
     Synthetic genes containing modified heavy and/or light chain variable regions are constructed and linked to human γ heavy chain and/or kappa light chain constant regions. Any human heavy chain and light chain constant regions may be used in combination with the Human Engineered™ antibody variable regions, including IgA (of any subclass, such as IgA1 or IgA2), IgD, IgE, IgG (of any subclass, such as IgG1, IgG2, IgG3, or IgG4), or IgM. The human heavy and light chain genes are introduced into host cells, such as mammalian cells, and the resultant recombinant immunoglobulin products are obtained and characterized. Human antibodies can also be produced using various techniques known in the art, including phage display libraries [Hoogenboom and Winter, J. Mol. Biol., 227:381 (1991); Marks et al., J. Mol. Biol., 222:581 (1991)]. The techniques of Cole et al. and Boerner et al. are also available for the preparation of human monoclonal antibodies [Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985) and Boerner et al., J. Immunol., 147(1): δ 95 (1991)]. 
     Human antibodies to PRLR polypeptides can also be produced using transgenic animals that are engineered to contain human immunoglobulin loci. For example, WO 98/24893 discloses transgenic animals having a human Ig locus wherein the animals do not produce functional endogenous immunoglobulins due to the inactivation of endogenous heavy and light chain loci. WO 91/10741 also discloses transgenic non-primate mammalian hosts capable of mounting an immune response to an immunogen, wherein the antibodies have primate constant and/or variable regions, and wherein the endogenous immunoglobulin-encoding loci are substituted or inactivated. WO 96/30498 discloses the use of the Cre/Lox system to modify the immunoglobulin locus in a mammal, such as to replace all or a portion of the constant or variable region to form a modified antibody molecule. WO 94/02602 discloses non-human mammalian hosts having inactivated endogenous Ig loci and functional human Ig loci. U.S. Pat. No. 5,939,598 discloses methods of making transgenic mice in which the mice lack endogenous heavy chains, and express an exogenous immunoglobulin locus comprising one or more xenogeneic constant regions. 
     Using a transgenic animal described above, an immune response can be produced to a selected antigenic molecule, and antibody-producing cells can be removed from the animal and used to produce hybridomas that secrete human monoclonal antibodies. Immunization protocols, adjuvants, and the like are known in the art, and are used in immunization of, for example, a transgenic mouse as described in WO 96/33735. The monoclonal antibodies can be tested for the ability to inhibit or neutralize the biological activity or physiological effect of the corresponding protein. See also Jakobovits et al., Proc. Natl. Acad. Sci. USA, 90:2551 (1993); Jakobovits et al., Nature, 362:255-258 (1993); Bruggermann et al., Year in Immuno., 7:33 (1993); and U.S. Pat. No. 5,591,669, U.S. Pat. No. 5,589,369, U.S. Pat. No. 5,545,807; and U.S Patent Application No. 20020199213, WO 96/34096 and U.S. patent application no. 20030194404; and U.S. patent application no. 20030031667. U.S. Patent Application No. 20030092125 describes methods for biasing the immune response of an animal to the desired epitope. Human antibodies may also be generated by in vitro activated B cells (see U.S. Pat. Nos. 5,567,610 and 5,229,275). 
     Additional transgenic animals useful to make monoclonal antibodies include the Medarex HuMAb-MOUSE®, described in U.S. Pat. No. 5,770,429 and Fishwild, et al. (Nat. Biotechnol. 14:845-851, 1996), which contains gene sequences from unrearranged human antibody genes that code for the heavy and light chains of human antibodies. Immunization of a HuMAb-MOUSE® enables the production of monoclonal antibodies to the target protein. 
     Also, Ishida et al. (Cloning Stem Cells. 4:91-102, 2002) describes the TransChromo Mouse (TCMOUSE™) which comprises megabase-sized segments of human DNA and which incorporates the entire human immunoglobulin (hIg) loci. The TCMOUSE has a fully diverse repertoire of hIgs, including all the subclasses of IgGs (IgG1-G4). Immunization of the TC Mouse with various human antigens produces antibody responses comprising human antibodies. 
     The development of technologies for making repertoires of recombinant human antibody genes, and the display of the encoded antibody fragments on the surface of filamentous bacteriophage, has provided a means for making human antibodies directly. The antibodies produced by phage technology are produced as antigen binding fragments—usually Fv or Fab fragments—in bacteria and thus lack effector functions. Effector functions can be introduced by one of two strategies: The fragments can be engineered either into complete antibodies for expression in mammalian cells, or into bispecific antibody fragments with a second binding site capable of triggering an effector function. 
     Typically, the Fd fragment (VH-CH1) and light chain (VL-CL) of antibodies are separately cloned by PCR and recombined randomly in combinatorial phage display libraries, which can then be selected for binding to a particular antigen. The Fab fragments are expressed on the phage surface, i.e., physically linked to the genes that encode them. Thus, selection of Fab by antigen binding co-selects for the Fab encoding sequences, which can be amplified subsequently. By several rounds of antigen binding and re-amplification, a procedure termed panning, Fab specific for the antigen are enriched and finally isolated. 
     In 1994, an approach for the humanization of antibodies, called “guided selection”, was described. Guided selection utilizes the power of the phage display technique for the humanization of mouse monoclonal antibody (See Jespers, L. S., et al., Bio/Technology 12, 899-903 (1994)). For this, the Fd fragment of the mouse monoclonal antibody can be displayed in combination with a human light chain library, and the resulting hybrid Fab library may then be selected with antigen. The mouse Fd fragment thereby provides a template to guide the selection. Subsequently, the selected human light chains are combined with a human Fd fragment library. Selection of the resulting library yields entirely human Fab. 
     A variety of procedures have been described for deriving human antibodies from phage-display libraries (See, for example, Hoogenboom et al., J. Mol. Biol., 227:381 (1991); Marks et al., J. Mol. Biol, 222:581-597 (1991); U.S. Pat. Nos. 5,565,332 and 5,573,905; Clackson, T., and Wells, J. A., TIBTECH 12, 173-184 (1994)). In particular, in vitro selection and, evolution of antibodies derived from phage display libraries has become a powerful tool (See Burton, D. R., and Barbas III, C. F., Adv. Immunol. 57, 191-280 (1994); and, Winter, G., et al., Annu. Rev. Immunol. 12, 433-455 (1994); U.S. patent application no. 20020004215 and WO92/01047; U.S. patent application no. 20030190317 published Oct. 9, 2003 and U.S. Pat. No. 6,054,287; U.S. Pat. No. 5,877,293. 
     Watkins, “Screening of Phage-Expressed Antibody Libraries by Capture Lift,” Methods in Molecular Biology, Antibody Phage Display: Methods and Protocols 178: 187-193, and U.S., patent application no. 200120030044772 published Mar. 6, 2003 describe methods for screening phage-expressed antibody libraries or other binding molecules by capture lift, a method involving immobilization of the candidate binding molecules on a solid support. 
     The antibody products may be screened for activity and for suitability in the treatment methods of the invention using assays as described in the section entitled “Screening Methods” herein or using any suitable assays known in the art. 
     In the present invention, PRLR polypeptides as recited above and variants thereof may be used to immunize a transgenic animal as described above. Monoclonal antibodies are made using methods known in the art, and the specificity of the antibodies is tested using isolated PRLR polypeptides. Methods for preparation of the human or primate PRLR or an epitope thereof include, but are not limited to chemical synthesis, recombinant DNA techniques or isolation from biological samples. Chemical synthesis of a peptide can be performed, for example, by the classical Merrifeld method of solid phase peptide synthesis (Merrifeld,  J. Am. Chem. Soc.  85:2149, 1963 which is incorporated by reference) or the FMOC strategy on a Rapid Automated Multiple Peptide Synthesis system (E. I. du Pont de Nemours Company, Wilmington, Del.) (Caprino and Han,  J. Org. Chem.  37:3404, 1972 which is incorporated by reference). 
     Polyclonal antibodies can be prepared by immunizing rabbits or other animals by injecting antigen followed by subsequent boosts at appropriate intervals. Alternative animals include mice, rats, chickens, guinea pigs, sheep, horses, monkeys, camels and sharks. The animals are bled and sera assayed against purified PRLR proteins usually by ELISA or by bioassay based upon the ability to block the action of PRLR proteins. When using avian species, e.g., chicken, turkey and the like, the antibody can be isolated from the yolk of the egg. Monoclonal antibodies can be prepared after the method of Milstein and Kohler by fusing splenocytes from immunized mice with continuously replicating tumor cells such as myeloma or lymphoma cells. (Milstein and Kohler,  Nature  256:495-497, 1975; Gulfre and Milstein,  Methods in Enzymology: Immunochemical Techniques  73:1-46, Langone and Banatis eds., Academic Press, 1981 which are incorporated by reference). The hybridoma cells so formed are then cloned by limiting dilution methods and supernates assayed for antibody production by ELISA, RIA or bioassay. 
     The unique ability of antibodies to recognize and specifically bind to target proteins provides an approach for treating an overexpression of the protein. Thus, another aspect of the present invention provides for a method for preventing or treating diseases involving overexpression of a PRLR polypeptide by treatment of a patient with specific antibodies to the PRLR protein. 
     Specific antibodies, either polyclonal or monoclonal, to the PRLR proteins can be produced by any suitable method known in the art as discussed above. For example, murine or human monoclonal antibodies can be produced by hybridoma technology or, alternatively, the PRLR proteins, or an immunologically active fragment thereof, or an anti-idiotypic antibody, or fragment thereof can be administered to an animal to elicit the production of antibodies capable of recognizing and binding to the PRLR proteins. Such antibodies can be from any class of antibodies including, but not limited to IgG, IgA, IgM, IgD, and IgE or in the case of avian species, IgY and from any subclass of antibodies. 
     Amino Acid Sequence Variants 
     A useful method for identification of certain residues or regions of the antibody that are preferred locations for mutagenesis is called “alanine scanning mutagenesis,” as described by Cunningham and Wells Science, 244:1081-1085 (1989). Here, a residue or group of target residues are identified (e.g., charged residues such as arg, asp, his, lys, and glu) and replaced by a neutral or negatively charged amino acid (most preferably alanine or polyalanine) to affect the interaction of the amino acids with antigen. Those amino acid locations demonstrating functional sensitivity to the substitutions then are refined by introducing further or other variants at, or for, the sites of substitution. Thus, while the site for introducing an amino acid sequence variation is predetermined, the nature of the mutation per se need not be predetermined. For example, to analyze the performance of a mutation at a given site, ala scanning or random mutagenesis is conducted at the target codon or region and the expressed antibody variants are screened for the desired activity. 
     Amino acid sequence insertions include amino- and/or carboxyl-terminal fusions ranging in length from one residue to polypeptides containing a hundred or more residues, as well as intra-sequence insertions of single or multiple amino acid residues. Examples of terminal insertions include an antibody with an N-terminal methionyl residue or the antibody (including antibody fragment) fused to an epitope tag or a salvage receptor epitope. Other insertional variants of the antibody molecule include the fusion to a polypeptide which increases the serum half-life of the antibody, e.g. at the N-terminus or C-terminus. 
     The term “epitope tagged” refers to the antibody fused to an epitope tag. The epitope tag polypeptide has enough residues to provide an epitope against which an antibody there against can be made, yet is short enough such that it does not interfere with activity of the antibody. The epitope tag preferably is sufficiently unique so that the antibody there against does not substantially cross-react with other epitopes. Suitable tag polypeptides generally have at least 6 amino acid residues and usually between about 8-50 amino acid residues (preferably between about 9-30 residues). Examples include the flu HA tag polypeptide and its antibody 12CA5 [Field et al., Mol. Cell. Biol. 8: 2159-2165 (1988)]; the c-myc tag and the 8F9, 3C7, 6E10, G4, B7 and 9E10 antibodies thereto [Evan et al., Mol. Cell. Biol. 5(12): 3610-3616 (1985)]; and the Herpes Simplex virus glycoprotein D (gD) tag and its antibody [Paborsky et al., Protein Engineering 3(6): 547-553 (1990)]. Other exemplary tags are a poly-histidine sequence, generally around six histidine residues, that permits isolation of a compound so labeled using nickel chelation. Other labels and tags, such as the FLAG® tag (Eastman Kodak, Rochester, N.Y.), well known and routinely used in the art, are embraced by the invention. 
     Another type of variant is an amino acid substitution variant. These variants have at least one amino acid residue in the antibody molecule removed and a different residue inserted in its place. Substitutional mutagenesis within any of the hypervariable or CDR regions or framework regions is contemplated. Conservative substitutions are shown in Table 2. The most conservative substitution is found under the heading of “preferred substitutions”. If such substitutions result in no change in biological activity, then more substantial changes, denominated “exemplary substitutions” in Table 2, or as further described below in reference to amino acid classes, may be introduced and the products screened. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Preferred Residue 
               
               
                   
                 Original 
                 Exemplary 
                 Substitutions 
               
               
                   
                   
               
             
            
               
                   
                 Ala (A) 
                 val; leu; ile 
                 val 
               
               
                   
                 Arg (R) 
                 lys; gln; asn 
                 lys 
               
               
                   
                 Asn (N) 
                 gln; his; asp, lys; gln 
                 arg 
               
               
                   
                 Asp (D) 
                 glu; asn 
                 glu 
               
               
                   
                 Cys (C) 
                 ser; ala 
                 ser 
               
               
                   
                 Gln (Q) 
                 asn; glu 
                 asn 
               
               
                   
                 Glu (E) 
                 asp; gln 
                 asp 
               
               
                   
                 Gly (G) 
                 ala 
               
               
                   
                 His (H) 
                 asn; gln; lys; arg 
               
               
                   
                 Ile (I) 
                 leu; val; met; ala; 
                 leu 
               
               
                   
                   
                 phe; 
                 norleucine 
               
               
                   
                 Leu (L) 
                 norleucine; ile; val; 
                 ile 
               
               
                   
                   
                 met; ala; phe 
               
               
                   
                 Lys (K) 
                 arg; gln; asn 
                 arg 
               
               
                   
                 Met (M) 
                 leu; phe; ile 
                 leu 
               
               
                   
                 Phe (F) 
                 leu; val; ile; ala; tyr 
               
               
                   
                 Pro (P) 
                 ala 
               
               
                   
                 Ser (S) 
                 thr 
               
               
                   
                 Thr (T) 
                 ser 
                 ser 
               
               
                   
                 Trp (W) 
                 tyr; phe 
                 tyr 
               
               
                   
                 Tyr (Y) 
                 trp; phe; thr; ser 
                 phe 
               
               
                   
                 Val (V) 
                 ile; leu; met; phe; 
                 leu 
               
               
                   
                   
                 ala; norleucine 
               
               
                   
                   
               
            
           
         
       
     
     Substantial modifications in the biological properties of the antibody are accomplished by selecting substitutions that differ significantly in their effect on maintaining (a) the structure of the polypeptide backbone in the area of the substitution, for example, as a sheet or helical conformation, (b) the charge or hydrophobicity of the molecule at the target site, or (c) the bulk of the side chain. Naturally occurring residues are divided into groups based on common side-chain properties: 
     (1) hydrophobic: norleucine, met, ala, val, leu, ile;
 
(2) neutral hydrophilic: cys, ser, thr;
 
(3) acidic: asp, glu;
 
(4) basic: asn, gln, his, lys, arg;
 
(5) residues that influence chain orientation: gly, pro; and
 
(6) aromatic: trp, tyr, phe.
 
     Conservative substitutions involve replacing an amino acid with another member of its class. Non-conservative substitutions involve replacing a member of one of these classes with a member of another class. 
     Any cysteine residue not involved in maintaining the proper conformation of the monoclonal, human, humanized, or variant antibody also may be substituted, generally with serine, to improve the oxidative stability of the molecule and prevent aberrant crosslinking. Conversely, cysteine bond(s) may be added to the antibody to improve its stability (particularly where the antibody is an antibody fragment such as an Fv fragment). 
     Affinity maturation involves preparing and screening antibody variants that have substitutions within the CDRs of a parent antibody and selecting variants that have improved biological properties such as binding affinity relative to the parent antibody. A convenient way for generating such substitutional variants is affinity maturation using phage display. Briefly, several hypervariable region sites (e.g. 6-7 sites) are mutated to generate all possible amino substitutions at each site. The antibody variants thus generated are displayed in a monovalent fashion from filamentous phage particles as fusions to the gene III product of M13 packaged within each particle. The phage-displayed variants are then screened for their biological activity (e.g. binding affinity). 
     Alanine scanning mutagenesis can be performed to identify hypervariable region residues that contribute significantly to antigen binding. Alternatively, or in addition, it may be beneficial to analyze a crystal structure of the antigen-antibody complex to identify contact points between the antibody and antigen. Such contact residues and neighboring residues are candidates for substitution according to the techniques elaborated herein. Once such variants are generated, the panel of variants is subjected to screening as described herein and antibodies with superior properties in one or more relevant assays may be selected for further development. 
     Antibody variants can also be produced that have a modified glycosylation pattern relative to the parent antibody, for example, deleting one or more carbohydrate moieties found in the antibody, and/or adding one or more glycosylation sites that are not present in the antibody. 
     Glycosylation of antibodies is typically either N-linked or O-linked. N-linked refers to the attachment of the carbohydrate moiety to the side chain of an asparagine residue. The tripeptide sequences asparagine-X-serine and asparagine-X-threonine, where X is any amino acid except proline, are the recognition sequences for enzymatic attachment of the carbohydrate moiety to the asparagine side chain. The presence of either of these tripeptide sequences in a polypeptide creates a potential glycosylation site. Thus, N-linked glycosylation sites may be added to an antibody by altering the amino acid sequence such that it contains one or more of these tripeptide sequences. O-linked glycosylation refers to the attachment of one of the sugars N-aceylgalactosamine, galactose, or xylose to a hydroxyamino acid, most commonly serine or threonine, although 5-hydroxyproline or 5-hydroxylysine may also be used. O-linked glycosylation sites may be added to an antibody by inserting or substituting one or more serine or threonine residues to the sequence of the original antibody. 
     Altered Effector Function 
     Other modifications of the antibody are contemplated. For example, it may be desirable to modify the antibody of the invention with respect to effector function, e.g., half-life, CDC or ADCC activity, so as to enhance the effectiveness of the antibody in treating cancer, for example. For example cysteine residue(s) may be introduced in the Fc region, thereby allowing interchain disulfide bond formation in this region. The homodimeric antibody thus generated may have improved internalization capability and/or increased complement-mediated cell killing and antibody-dependent cellular cytotoxicity (ADCC). See Caron et al., J. Exp Med. 176: 1191-1195 (1992) and Shopes, B. J. Immunol. 148: 2918-2922 (1992). Homodimeric antibodies with enhanced anti-tumor activity may also be prepared using heterobifunctional cross-linkers as described in Wolff et al., Cancer Research 53: 2560-2565 (1993). Alternatively, an antibody can be engineered which has dual Fc regions and may thereby have enhanced complement lysis and ADCC capabilities. See Stevenson et al., Anti-Cancer Drug Design 3: 219-230 (1989). In addition, it has been shown that sequences within the CDR can cause an antibody to bind to MHC Class II and trigger an unwanted helper T-cell response. A conservative substitution can allow the antibody to retain binding activity yet lose its ability to trigger an unwanted T-cell response. Also see Steplewski et al., Proc Natl Acad Sci USA. 1988; 85(13):4852-6, incorporated herein by reference in its entirety, which described chimeric antibodies wherein a murine variable region was joined with human gamma 1, gamma 2, gamma 3, and gamma 4 constant regions. Also see Presta et al., Biochem Soc Trans. 2002; 30(4):487-90, incorporated herein by reference in its entirety, which described several positions in the Fc region of IgG1 were found which improved binding only to specific Fc gamma receptors (R) or simultaneously improved binding to one type of Fc gamma R and reduced binding to another type. Selected IgG1 variants with improved binding to Fc gamma RIIIa were then tested in an in vitro antibody-dependent cellular cytotoxicity (ADCC) assay and showed an enhancement in ADCC when either peripheral blood mononuclear cells or natural killer cells were used. 
     In certain embodiments of the invention, it may be desirable to use an antibody fragment, rather than an intact antibody, to increase tumor penetration, for example. In this case, it may be desirable to modify the antibody fragment in order to increase its serum half-life, for example, adding molecules such as PEG or other water soluble polymers, including polysaccharide polymers, to antibody fragments to increase the half-life. This may also be achieved, for example, by incorporation of a salvage receptor binding epitope into the antibody fragment (e.g., by mutation of the appropriate region in the antibody fragment or by incorporating the epitope into a peptide tag that is then fused to the antibody fragment at either end or in the middle, e.g., by DNA or peptide synthesis) (see, e.g., WO96/32478). 
     Additionally, antibodies can be chemically modified by covalent conjugation to a polymer to increase their circulating half-life, for example. Each antibody molecule may be attached to one or more (i.e. 1, 2, 3, 4, 5 or more) polymer molecules. Polymer molecules are preferably attached to antibodies by linker molecules. The polymer may, in general, be a synthetic or naturally occurring polymer, for example an optionally substituted straight or branched chain polyalkene, polyalkenylene or polyoxyalkylene polymer or a branched or unbranched polysaccharide, e.g. homo- or hetero-polysaccharide. Preferred polymers are polyoxyethylene polyols and polyethylene glycol (PEG). PEG is soluble in water at room temperature and has the general formula: R(O—CH2—CH2) n O—R where R can be hydrogen, or a protective group such as an alkyl or alkanol group. Preferably, the protective group has between 1 and 8 carbons, more preferably it is methyl. The symbol n is a positive integer, preferably between 1 and 1,000, more preferably between 2 and 500. The PEG has a preferred average molecular weight between 1000 and 40,000, more preferably between 2000 and 20,000, most preferably between 3,000 and 12,000. Preferably, PEG has at least one hydroxy group, more preferably it is a terminal hydroxy group. It is this hydroxy group which is preferably activated to react with a free amino group on the inhibitor. However, it will be understood that the type and amount of the reactive groups may be varied to achieve a covalently conjugated PEG/antibody of the present invention. Preferred polymers, and methods to attach them to peptides, are shown in U.S. Pat. Nos. 4,766,106; 4,179,337; 4,495,285; and 4,609,546 which are all hereby incorporated by reference in their entireties. 
     As used herein, the term “salvage receptor binding epitope” refers to an epitope of the Fc region of an IgG molecule (e.g., IgG1, IgG2, IgG3, or IgG4) that is responsible for increasing the in vivo serum half-life of the IgG molecule. 
     The salvage receptor binding epitope preferably constitutes a region wherein any one or more amino acid residues from one or two loops of a Fc domain are transferred to an analogous position of the antibody fragment. Even more preferably, three or more residues from one or two loops of the Fc domain are transferred. Still more preferred, the epitope is taken from the CH2 domain of the Fc region (e.g., of an IgG) and transferred to the CH1, CH3, or VH region, or more than one such region, of the antibody. Alternatively, the epitope is taken from the CH2 domain of the Fc region and transferred to the CL region or VL region, or both, of the antibody fragment. See also International applications WO 97/34631 and WO 96/32478 which describe Fc variants and their interaction with the salvage receptor. 
     Thus, antibodies of the invention may comprise a human Fc portion, a human consensus Fc portion, or a variant thereof that retains the ability to interact with the Fc salvage receptor, including variants in which cysteines involved in disulfide bonding are modified or removed, and/or in which the a met is added at the N-terminus and/or one or more of the N-terminal 20 amino acids are removed, and/or regions that interact with complement, such as the C1q binding site, are altered or removed, and/or the ADCC site is altered or removed [see, e.g., Molec. Immunol. 29 (5): 633-9 (1992)]. 
     Previous studies mapped the binding site on human and murine IgG for FcR primarily to the lower hinge region composed of IgG residues 233-239. Other studies proposed additional broad segments, e.g. Gly316-Lys338 for human Fc receptor 1, Lys274-Arg301 and Tyr407-Arg416 for human Fc receptor III, or found a few specific residues outside the lower hinge, e.g. Asn297 and Glu318 for murine IgG2b interacting with murine Fc receptor II. The report of the 3.2-Å crystal structure of the human IgG1 Fc fragment with human Fc receptor IIIA delineated IgG1 residues Leu234-Ser239, Asp265-Glu269, Asn297-Thr299, and Ala327-Ile332 as involved in binding to Fc receptor IIIA. It has been suggested based on crystal structure that in addition to the lower hinge (Leu234-Gly237), residues in IgG CH2 domain loops FG (residues 326-330) and BC (residues 265-271) might play a role in binding to Fc receptor IIA. See Shields et al., J. Biol. Chem., 276(9):6591-6604 (2001), incorporated by reference herein in its entirety. Mutation of residues within Fc receptor binding sites can result in altered effector function, such as altered ADCC or CDC activity, or altered half-life. As described above, potential mutations include insertion, deletion or substitution of one or more residues, including substitution with alanine, a conservative substitution, a non-conservative substitution, or replacement with a corresponding amino acid residue at the same position from a different IgG subclass (e.g. replacing an IgG1 residue with a corresponding IgG2 residue at that position). 
     Shields et al. reported that IgG1 residues involved in binding to all human Fc receptors are located in the CH2 domain proximal to the hinge and fall into two categories as follows: 1) positions that may interact directly with all FcR include Leu234-Pro238, Ala327, and Pro329 (and possibly Asp265); 2) positions that influence carbohydrate nature or position include Asp265 and Asn297. The additional IgG1 residues that affected binding to Fc receptor II are as follows: (largest effect) Arg255, Thr256, Glu258, Ser267, Asp270, Glu272, Asp280, Arg292, Ser298, and (less effect) His268, Asn276, His285, Asn286, Lys290, Gln295, Arg301, Thr307, Leu309, Asn315, Lys322, Lys326, Pro331, Ser337, Ala339, Ala378, and Lys414. A327Q, A327S, P329A, D265A and D270A reduced binding. In addition to the residues identified above for all FcR, additional IgG1 residues that reduced binding to Fc receptor 111A by 40% or more are as follows: Ser239, Ser267 (Gly only), His268, Glu293, Gln295, Tyr296, Arg301, Val303, Lys338, and Asp376. Variants that improved binding to FcRIIIA include T256A, K290A, S298A, E333A, K334A, and A339T. Lys414 showed a 40% reduction in binding for FcRIIA and FcRIIB, Arg416 a 30% reduction for FcRIIA and FcRIIIA, Gln419 a 30% reduction to FcRIIA and a 40% reduction to FcRIIB, and Lys360 a 23% improvement to FcRIIIA. See also Presta et al., Biochem. Soc. Trans. (2001) 30, 487-490. 
     For example, U.S. Pat. No. 6,194,551, incorporated herein by reference in its entirety, describes variants with altered effector function containing mutations in the human IgG Fc region, at amino acid position 329, 331 or 322 (using Kabat numbering), some of which display reduced C1q binding or CDC activity. As another example, U.S. Pat. No. 6,737,056, incorporated herein by reference in its entirety, describes variants with altered effector or Fc-gamma-receptor binding containing mutations in the human IgG Fc region, at amino acid position 238, 239, 248, 249, 252, 254, 255, 256, 258, 265, 267, 268, 269, 270, 272, 276, 278, 280, 283, 285, 286, 289, 290, 292, 294, 295, 296, 298, 301, 303, 305, 307, 309, 312, 315, 320, 322, 324, 326, 327, 329, 330, 331, 333, 334, 335, 337, 338, 340, 360, 373, 376, 378, 382, 388, 389, 398, 414, 416, 419, 430, 434, 435, 437, 438 or 439 (using Kabat numbering), some of which display receptor binding profiles associated with reduced ADCC or CDC activity. Of these, a mutation at amino acid position 238, 265, 269, 270, 327 or 329 are stated to reduce binding to FcRI, a mutation at amino acid position 238, 265, 269, 270, 292, 294, 295, 298, 303, 324, 327, 329, 333, 335, 338, 373, 376, 414, 416, 419, 435, 438 or 439 are stated to reduce binding to FcRII, and a mutation at amino acid position 238, 239, 248, 249, 252, 254, 265, 268, 269, 270, 272, 278, 289, 293, 294, 295, 296, 301, 303, 322, 327, 329, 338, 340, 373, 376, 382, 388, 389, 416, 434, 435 or 437 is stated to reduce binding to FcRIII. 
     U.S. Pat. No. 5,624,821, incorporated by reference herein in its entirety, reports that Clq binding activity of an murine antibody can be altered by mutating amino acid residue 318, 320 or 322 of the heavy chain and that replacing residue 297 (Asn) results in removal of lytic activity. 
     United States Application Publication No. 20040132101, incorporated by reference herein in its entirety, describes variants with mutations at amino acid positions 240, 244, 245, 247, 262, 263, 266, 299, 313, 325, 328, or 332 (using Kabat numbering) or positions 234, 235, 239, 240, 241, 243, 244, 245, 247, 262, 263, 264, 265, 266, 267, 269, 296, 297, 298, 299, 313, 325, 327, 328, 329, 330, or 332 (using Kabat numbering), of which mutations at positions 234, 235, 239, 240, 241, 243, 244, 245, 247, 262, 263, 264, 265, 266, 267, 269, 296, 297, 298, 299, 313, 325, 327, 328, 329, 330, or 332 may reduce ADCC activity or reduce binding to an Fc gamma receptor. 
     Chappel et al., Proc Natl Acad Sci USA. 1991; 88(20):9036-40, incorporated herein by reference in its entirety, report that cytophilic activity of IgG1 is an intrinsic property of its heavy chain CH2 domain. Single point mutations at any of amino acid residues 234-237 of IgG1 significantly lowered or abolished its activity. Substitution of all of IgG1 residues-234-237 (LLGG) into IgG2 and IgG4 were required to restore full binding activity. An IgG2 antibody containing the entire ELLGGP sequence (residues 233-238) was observed to be more active than wild-type IgG1. 
     Isaacs et al., J. Immunol. 1998; 161(8):3862-9, incorporated herein by reference in its entirety, report that mutations within a motif critical for Fc gammaR binding (glutamate 233 to proline, leucine/phenylalanine 234 to valine, and leucine 235 to alanine) completely prevented depletion of target cells. The mutation glutamate 318 to alanine eliminated effector function of mouse IgG2b and also reduced the potency of human IgG4. 
     Armour et al., Mol. Immunol. 2003; 40(9):585-93, incorporated by reference herein in its entirety, identified IgG1 variants which react with the activating receptor, FcgammaRIIa, at least 10-fold less efficiently than wildtype IgG1 but whose binding to the inhibitory receptor, FcgammaRIIb, is only four-fold reduced. Mutations were made in the region of amino acids 233-236 and/or at amino acid positions 327, 330 and 331. See also WO 99/58572, incorporated by reference herein in its entirety. 
     Xu et al., J Biol. Chem. 1994; 269(5):3469-74, incorporated by reference herein in its entirety, report that mutating IgG1 Pro331 to Ser markedly decreased C1q binding and virtually eliminated lytic activity. In contrast, the substitution of Pro for Ser331 in IgG4 bestowed partial lytic activity (40%) to the IgG4 Pro331 variant. 
     Schuurman et al., Mol Immunol. 2001; 38(1):1-8, incorporated by reference herein in its entirety, report that mutating one of the hinge cysteines involved in the inter-heavy chain bond formation, Cys226, to serine resulted in a more stable inter-heavy chain linkage. Mutating the IgG4 hinge sequence Cys-Pro-Ser-Cys to the IgG1 hinge sequence Cys-Pro-Pro-Cys also markedly stabilizes the covalent interaction between the heavy chains. 
     Angal et al., Mol Immunol. 1993; 30(1):105-8, incorporated by reference herein in its entirety, report that mutating the serine at amino acid position 241 in IgG4 to proline (found at that position in IgG1 and IgG2) led to the production of a homogeneous antibody, as well as extending serum half-life and improving tissue distribution compared to the original chimeric IgG4. 
     The invention also contemplates production of antibody molecules with altered carbohydrate structure resulting in altered effector activity, including antibody molecules with absent or reduced fucosylation that exhibit improved ADCC activity. A variety of ways are known in the art to accomplish this. For example, ADCC effector activity is mediated by binding of the antibody molecule to the FcγRIII receptor, which has been shown to be dependent on the carbohydrate structure of the N-linked glycosylation at the Asn-297 of the CH2 domain. Non-fucosylated antibodies bind this receptor with increased affinity and trigger FcγRIII-mediated effector functions more efficiently than native, fucosylated antibodies. For example, recombinant production of non-fucosylated antibody in CHO cells in which the alpha-1,6-fucosyl transferase enzyme has been knocked out results in antibody with 100-fold increased ADCC activity [Yamane-Ohnuki et al., Biotechnol Bioeng. 2004 Sep. 5; 87(5):614-22]. Similar effects can be accomplished through decreasing the activity of this or other enzymes in the fucosylation pathway, e.g., through siRNA or antisense RNA treatment, engineering cell lines to knockout the enzyme(s), or culturing with selective glycosylation inhibitors [Rothman et al., Mol. Immunol. 1989 December; 26(12):1113-23]. Some host cell strains, e.g. Lec13 or rat hybridoma YB2/0 cell line naturally produce antibodies with lower fucosylation levels. Shields et al., J Biol. Chem. 2002 Jul. 26; 277(30):26733-40; Shinkawa et al., J Biol Chem. 2003 Jan. 31; 278(5):3466-73. An increase in the level of bisected carbohydrate, e.g. through recombinantly producing antibody in cells that overexpress GnTIII enzyme, has also been determined to increase ADCC activity. Umana et al., Nat. Biotechnol. 1999 February; 17(2):176-80. It has been predicted that the absence of only one of the two fucose residues may be sufficient to increase ADCC activity. Ferrara et al., J Biol. Chem. 2005 Dec. 5; [Epub ahead of print] 
     Other Covalent Modifications 
     Covalent modifications of the antibody are also included within the scope of this invention. They may be made by chemical synthesis or by enzymatic or chemical cleavage of the antibody, if applicable. Other types of covalent modifications of the antibody are introduced into the molecule by reacting targeted amino acid residues of the antibody with an organic derivatizing agent that is capable of reacting with selected side chains or the N- or C-terminal residues. 
     Cysteinyl residues most commonly are reacted with α-haloacetates (and corresponding amines), such as chloroacetic acid or chloroacetamide, to give carboxymethyl or carboxyamidomethyl derivatives. Cysteinyl residues also are derivatized by reaction with bromotrifluoroacetone, .alpha.-bromo-□-(5-imidozoyl)propionic acid, chloroacetyl phosphate, N-alkylmaleimides, 3-nitro-2-pyridyl disulfide, methyl 2-pyridyl disulfide, p-chloromercuribenzoate, 2-chloromercuri-4-nitrophenol, or chloro-7-nitrobenzo-2-oxa-1,3-diazole. 
     Histidyl residues are derivatized by reaction with diethylpyrocarbonate at pH 5.5-7.0 because this agent is relatively specific for the histidyl side chain. Para-bromophenacyl bromide also is useful; the reaction is preferably performed in 0.1 M sodium cacodylate at pH 6.0. 
     Lysinyl and amino-terminal residues are reacted with succinic or other carboxylic acid anhydrides. Derivatization with these agents has the effect of reversing the charge of the lysinyl residues. Other suitable reagents for derivatizing .alpha.-amino-containing residues include imidoesters such as methyl picolinimidate, pyridoxal phosphate, pyridoxal, chloroborohydride, trinitrobenzenesulfonic acid, O-methylisourea, 2,4-pentanedione,- and transaminase-catalyzed reaction with glyoxylate. 
     Arginyl residues are modified by reaction with one or several conventional reagents, among them phenylglyoxal, 2,3-butanedione, 1,2-cyclohexanedione, and ninhydrin. Derivatization of arginine residues requires that the reaction be performed in alkaline conditions because of the high pKa of the guanidine functional group. Furthermore, these reagents may react with the groups of lysine as well as the arginine epsilon-amino group. 
     The specific modification of tyrosyl residues may be made, with particular interest in introducing spectral labels into tyrosyl residues by reaction with aromatic diazonium compounds or tetranitromethane. Most commonly, N-acetylimidizole and tetranitromethane are used to form O-acetyl tyrosyl species and 3-nitro derivatives, respectively. Tyrosyl residues are iodinated using 125I or 131I to prepare labeled proteins for use in radioimmunoassay. 
     Carboxyl side groups (aspartyl or glutamyl) are selectively modified by reaction with carbodiimides (R—N.dbd.C.dbd.N—R′), where R and R′ are different alkyl groups, such as 1-cyclohexyl-3-(2-morpholinyl-4-ethyl) carbodiimide or 1-ethyl-3-(4-azonia-4,4-dimethylpentyl) carbodiimide. Furthermore, aspartyl and glutamyl residues are converted to asparaginyl and glutaminyl residues by reaction with ammonium ions. 
     Glutaminyl and asparaginyl residues are frequently deamidated to the corresponding glutamyl and aspartyl residues, respectively. These residues are deamidated under neutral or basic conditions. The deamidated form of these residues falls within the scope of this invention. 
     Other modifications include hydroxylation of proline and lysine, phosphorylation of hydroxyl groups of seryl or threonyl residues, methylation of the .alpha.-amino groups of lysine, arginine, and histidine side chains (T. E. Creighton, Proteins: Structure and Molecular Properties, W.H. Freeman &amp; Co., San Francisco, pp. 79-86 (1983)), acetylation of the N-terminal amine, and amidation of any C-terminal carboxyl group. 
     Another type of covalent modification involves chemically or enzymatically coupling glycosides to the antibody. These procedures are advantageous in that they do not require production of the antibody in a host cell that has glycosylation capabilities for N- or O-linked glycosylation. Depending on the coupling mode used, the sugar(s) may be attached to (a) arginine and histidine, (b) free carboxyl groups, (c) free sulfhydryl groups such as those of cysteine, (d) free hydroxyl groups such as those of serine, threonine, or hydroxyproline, (e) aromatic residues such as those of phenylalanine, tyrosine, or tryptophan, or (f) the amide group of glutamine. These methods are described in WO87/05330 published 11 Sep. 1987, and in Aplin and Wriston, CRC Crit. Rev. Biochem., pp. 259-306 (1981). 
     Removal of any carbohydrate moieties present on the antibody may be accomplished chemically or enzymatically. Chemical deglycosylation requires exposure of the antibody to the compound trifluoromethanesulfonic acid, or an equivalent compound. This treatment results in the cleavage of most or all sugars except the linking sugar (N-acetylglucosamine or N-acetylgalactosamine), while leaving the antibody intact. Chemical deglycosylation is described by Hakimuddin, et al. Arch. Biochem. Biophys. 259: 52 (1987) and by Edge et al. Anal. Biochem., 118: 131 (1981). Enzymatic cleavage of carbohydrate moieties on antibodies can be achieved by the use of a variety of endo- and exo-glycosidases as described by Thotakura et al. Meth. Enzymol. 138: 350 (1987). 
     Another type of covalent modification of the antibody comprises linking the antibody to one of a variety of nonproteinaceous polymers, e.g., polyethylene glycol, polypropylene glycol, polyoxyethylated polyols, polyoxyethylated sorbitol, polyoxyethylated glucose, polyoxyethylated glycerol, polyoxyalkylenes, or polysaccharide polymers such as dextran. Such methods are known in the art, see, e.g. U.S. Pat. Nos. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192, 4,179,337, 4,766,106, 4,179,337, 4,495,285, 4,609,546 or EP 315 456. 
     Gene Therapy 
     Delivery of a therapeutic antibody to appropriate cells can be effected via gene therapy ex vivo, in situ, or in vivo by use of any suitable approach known in the art, including by use of physical DNA transfer methods (e.g., liposomes or chemical treatments) or by use of viral vectors (e.g., adenovirus, adeno-associated virus, or a retrovirus). For example, for in vivo therapy, a nucleic acid encoding the desired antibody, either alone or in conjunction with a vector, liposome, or precipitate may be injected directly into the subject, and in some embodiments, may be injected at the site where the expression of the antibody compound is desired. For ex vivo treatment, the subject&#39;s cells are removed, the nucleic acid is introduced into these cells, and the modified cells are returned to the subject either directly or, for example, encapsulated within porous membranes which are implanted into the patient. See, e.g. U.S. Pat. Nos. 4,892,538 and 5,283,187. There are a variety of techniques available for introducing nucleic acids into viable cells. The techniques vary depending upon whether the nucleic acid is transferred into cultured cells in vitro, or in vivo in the cells of the intended host. Techniques suitable for the transfer of nucleic acid into mammalian cells in vitro include the use of liposomes, electroporation, microinjection, cell fusion, DEAE-dextran, and calcium phosphate precipitation. A commonly used vector for ex vivo delivery of a nucleic acid is a retrovirus. 
     Other in vivo nucleic acid transfer techniques include transfection with viral vectors (such as adenovirus, Herpes simplex I virus, or adeno-associated virus) and lipid-based systems. The nucleic acid and transfection agent are optionally associated with a microparticle. Exemplary transfection agents include calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, quaternary ammonium amphiphile DOTMA ((dioleoyloxypropyl) trimethylammonium bromide, commercialized as Lipofectin by GIBCO-BRL))(Felgner et al, (1987) Proc. Natl. Acad. Sci. USA 84, 7413-7417; Malone et al. (1989) Proc. Natl. Acad. Sci. USA 86 6077-6081); lipophilic glutamate diesters with pendent trimethylammonium heads (Ito et al. (1990) Biochem. Biophys. Acta 1023, 124-132); the metabolizable parent lipids such as the cationic lipid dioctadecylamido glycylspermine (DOGS, Transfectam, Promega) and dipalmitoylphosphatidyl ethanolamylspermine (DPPES) (J. P. Behr (1986) Tetrahedron Lett. 27, 5861-5864; J. P. Behr et al. (1989) Proc. Natl. Acad. Sci. USA 86, 6982-6986); metabolizable quaternary ammonium salts (DOTB, N-(1-[2,3-dioleoyloxy]propyl)-N,N,N-trimethylammonium methylsulfate (DOTAP) (Boehringer Mannheim), polyethyleneimine (PEI), dioleoyl esters, ChoTB, ChoSC, DOSC) (Leventis et al. (1990) Biochim. Inter. 22, 235-241); 3beta[N—(N′,N′-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol), dioleoylphosphatidyl ethanolamine (DOPE)/3beta[N—(N′,N′-dimethylaminoethane)-carbamoyl]cholesterolDC-Chol in one to one mixtures (Gao et al., (1991) Biochim. Biophys. Acta 1065, 8-14), spermine, spermidine, lipopolyamines (Behr et al., Bioconjugate Chem, 1994, 5: 382-389), lipophilic polylysines (LPLL) (Zhou et al., (1991) Biochim. Biophys. Acta 939, 8-18), [[(1,1,3,3-tetramethylbutyl)cre-soxy]ethoxy]ethyl]dimethylbenzylammonium hydroxide (DEBDA hydroxide) with excess phosphatidylcholine/cholesterol (Ballas et al., (1988) Biochim. Biophys. Acta 939, 8-18), cetyltrimethylammonium bromide (CTAB)/DOPE mixtures (Pinnaduwage et al, (1989) Biochim. Biophys. Acta 985, 33-37), lipophilic diester of glutamic acid (TMAG) with DOPE, CTAB, DEBDA, didodecylammonium bromide (DDAB), and stearylamine in admixture with phosphatidylethanolamine (Rose et al., (1991) Biotechnique 10, 520-525), DDAB/DOPE (TransfectACE, GIBCO BRL), and oligogalactose bearing lipids. Exemplary transfection enhancer agents that increase the efficiency of transfer include, for example, DEAE-dextran, polybrene, lysosome-disruptive peptide (Ohmori N I et al, Biochem Biophys Res Commun Jun. 27, 1997; 235(3):726-9), chondroitan-based proteoglycans, sulfated proteoglycans, polyethylenimine, polylysine (Pollard H et al. J Biol Chem, 1998 273 (13):7507-11), integrin-binding peptide CYGGRGDTP, linear dextran nonasaccharide, glycerol, cholesteryl groups tethered at the 3′-terminal internucleoside link of an oligonucleotide (Letsinger, R. L. 1989 Proc Natl Acad Sci USA 86: (17):6553-6), lysophosphatide, lysophosphatidylcholine, lysophosphatidylethanolamine, and 1-oleoyl lysophosphatidylcholine. 
     In some situations it may be desirable to deliver the nucleic acid with an agent that directs the nucleic acid-containing vector to target cells. Such “targeting” molecules include antibodies specific for a cell-surface membrane protein on the target cell, or a ligand for a receptor on the target cell. Where liposomes are employed, proteins which bind to a cell-surface membrane protein associated with endocytosis may be used for targeting and/or to facilitate uptake. Examples of such proteins include capsid proteins and fragments thereof tropic for a particular cell type, antibodies for proteins which undergo internalization in cycling, and proteins that target intracellular localization and enhance intracellular half-life. In other embodiments, receptor-mediated endocytosis can be used. Such methods are described, for example, in Wu et al., 1987 or Wagner et al., 1990. For review of the currently known gene marking and gene therapy protocols, see Anderson 1992. See also WO 93/25673 and the references cited therein. For additional reviews of gene therapy technology, see Friedmann, Science, 244: 1275-1281 (1989); Anderson, Nature, supplement to vol. 392, no 6679, pp. 25-30 (1998); Verma, Scientific American: 68-84 (1990); and Miller, Nature, 357: 455-460 (1992). 
     Screening Methods 
     Effective therapeutics depend on identifying efficacious agents devoid of significant toxicity. Antibodies may be screened for binding affinity by methods known in the art. For example, gel-shift assays, Western blots, radiolabeled competition assay, co-fractionation by chromatography, co-precipitation, cross linking, ELISA, and the like may be used, which are described in, for example, Current Protocols in Molecular Biology (1999) John Wiley &amp; Sons, NY, which is incorporated herein by reference in its entirety. 
     To initially screen for antibodies which bind to the desired epitope on PRLR (e.g., the extracellular domain of PRLR), a routine cross-blocking assay such as that described in Antibodies, A Laboratory Manual, Cold Spring Harbor Laboratory, Ed Harlow and David Lane (1988), can be performed. Routine competitive binding assays may also be used, in which the unknown antibody is characterized by its ability to inhibit binding of PRLR to a PRLR specific antibody of the invention. Epitope mapping is described in Champe et al., J. Biol. Chem. 270: 1388-1394 (1995). 
     In one variation of an in vitro binding assay, the invention provides a method comprising the steps of (a) contacting an immobilized PRLR with a candidate antibody and (b) detecting binding of the candidate antibody to the PRLR. In an alternative embodiment, the candidate antibody is immobilized and binding of PRLR is detected. Immobilization is accomplished using any of the methods well known in the art, including covalent bonding to a support, a bead, or a chromatographic resin, as well as non-covalent, high affinity interaction such as antibody binding, or use of streptavidin/biotin binding wherein the immobilized compound includes a biotin moiety. Detection of binding can be accomplished (i) using a radioactive label on the compound that is not immobilized, (ii) using a fluorescent label on the non-immobilized compound, (iii) using an antibody immunospecific for the non-immobilized compound, (iv) using a label on the non-immobilized compound that excites a fluorescent support to which the immobilized compound is attached, as well as other techniques well known and routinely practiced in the art. 
     Antibodies that modulate (i.e., increase, decrease, or block) the activity or expression of PRLR may be identified by incubating a putative modulator with a cell expressing a PRLR and determining the effect of the putative modulator on the activity or expression of the PRLR. The selectivity of an antibody that modulates the activity of a PRLR polypeptide or polynucleotide can be evaluated by comparing its effects on the PRLR polypeptide or polynucleotide to its effect on other related compounds. Selective modulators may include, for example, antibodies and other proteins, peptides, or organic molecules which specifically bind to PRLR polypeptides or to a nucleic acid encoding a PRLR polypeptide. Modulators of PRLR activity will be therapeutically useful in treatment of diseases and physiological conditions in which normal or aberrant activity of PRLR polypeptide is involved. 
     Compounds potentially useful in preventing or treating cancer may be screened using various assays. For instance, a candidate antagonist may first be characterized in a cultured cell system to determine its ability to prevent PRLR dimerization and/or neutralize PRLR in inducing STAT5 and/or MAPK phosphorylation. 
     The anti-tumor activity of a particular PRLR antibody, or combination of PRLR antibodies, may be evaluated in vivo using a suitable animal model (Loukopoulos et al., Pancreas, 29(3):193-203 (2004)). In addition, the anti-tumor activity of a particular PRLR antibody may be evaluated by assaying, e.g., STAT5 and/or MAPK phosphorylation or other indicators of PRLR signaling. Additionally, cellular assays including proliferation assays, soft agar assays, and/or cytotoxicity assays as described herein may be used to evaluate a particular PRLR antibody. 
     The invention also comprehends high throughput screening (HTS) assays to identify antibodies that interact with or inhibit biological activity (i.e., inhibit enzymatic activity, binding activity, etc.) of a PRLR polypeptide. HTS assays permit screening of large numbers of compounds in an efficient manner. Cell-based HTS systems are contemplated to investigate the interaction between PRLR polypeptides and their binding partners. HTS assays are designed to identify “hits” or “lead compounds” having the desired property, from which modifications can be designed to improve the desired property. Chemical modification of the “hit” or “lead compound” is often based on an identifiable structure/activity relationship between the “hit” and PRLR polypeptides. 
     Another aspect of the present invention is directed to methods of identifying antibodies which modulate (i.e., decrease) activity of a PRLR comprising contacting a PRLR with an antibody, and determining whether the antibody modifies activity of the PRLR. The activity in the presence of the test antibody is compared to the activity in the absence of the test antibody. Where the activity of the sample containing the test antibody is lower than the activity in the sample lacking the test antibody, the antibody will have inhibited activity. 
     Antibody Conjugates 
     Anti-PRLR antibodies may be administered in their “naked” or unconjugated form, or may be conjugated directly to other therapeutic or diagnostic agents, or may be conjugated indirectly to carrier polymers comprising such other therapeutic or diagnostic agents. 
     Antibodies can be detectably labeled through the use of radioisotopes, affinity labels (such as biotin, avidin, etc.), enzymatic labels (such as horseradish peroxidase, alkaline phosphatase, etc.) fluorescent or luminescent or bioluminescent labels (such as FITC or rhodamine, etc.), paramagnetic atoms, and the like. Procedures for accomplishing such labeling are well known in the art; for example, see (Sternberger, L. A. et al., J. Histochem. Cytochem. 18:315 (1970); Bayer, E. A. et al., Meth. Enzym. 62:308 (1979); Engval, E. et al., Immunol. 109:129 (1972); Goding; J. W. J. Immunol. Meth. 13:215 (1976)). 
     Conjugation of antibody moieties is described in U.S. Pat. No. 6,306,393. General techniques are also described in Shih et al., Int. J. Cancer 41:832-839 (1988); Shih et al., Int. J. Cancer 46:1101-1106 (1990); and Shih et al., U.S. Pat. No. 5,057,313. This general method involves reacting an antibody component having an oxidized carbohydrate portion with a carrier polymer that has at least one free amine function and that is loaded with a plurality of drug, toxin, chelator, boron addends, or other therapeutic agent. This reaction results in an initial Schiff base (imine) linkage, which can be stabilized by reduction to a secondary amine to form the final conjugate. 
     The carrier polymer may be, for example, an aminodextran or polypeptide of at least 50 amino acid residues. Various techniques for conjugating a drug or other agent to the carrier polymer are known in the art. A polypeptide carrier can be used instead of aminodextran, but the polypeptide carrier should have at least 50 amino acid residues in the chain, preferably 100-5000 amino acid residues. At least some of the amino acids should be lysine residues or glutamate or aspartate residues. The pendant amines of lysine residues and pendant carboxylates of glutamine and aspartate are convenient for attaching a drug, toxin, immunomodulator, chelator, boron addend or other therapeutic agent. Examples of suitable polypeptide carriers include polylysine, polyglutamic acid, polyaspartic acid, co-polymers thereof and mixed polymers of these amino acids and others, e.g., serines, to confer desirable solubility properties on the resultant loaded carrier and conjugate. 
     Alternatively, conjugated antibodies can be prepared by directly conjugating an antibody component with a therapeutic agent. The general procedure is analogous to the indirect method of conjugation except that a therapeutic agent is directly attached to an oxidized antibody component. For example, a carbohydrate moiety of an antibody can be attached to polyethyleneglycol to extend half-life. 
     Alternatively, a therapeutic agent can be attached at the hinge region of a reduced antibody component via disulfide bond formation, or using a heterobifunctional cross-linker, such as N-succinyl 3-(2-pyridyldithio)proprionate (SPDP). Yu et al., Int. J. Cancer 56:244 (1994). General techniques for such conjugation are well-known in the art. See, for example, Wong, Chemistry Of Protein Conjugation and Cross-Linking (CRC Press 1991); Upeslacis et al., “Modification of Antibodies by Chemical Methods,” in Monoclonal Antibodies: Principles and Applications, Birch et al. (eds.), pages 187-230 (Wiley-Liss, Inc. 1995); Price, “Production and Characterization of Synthetic Peptide-Derived Antibodies,” in Monoclonal Antibodies: Production, Engineering and Clinical Application, Ritter et al. (eds.), pages 60-84 (Cambridge University Press 1995). A variety of bifunctional protein coupling agents are known in the art, such as N-succinimidyl-3-(2-pyridyldithiol) propionate (SPDP), iminothiolane (IT), bifunctional derivatives of imidoesters (such as dimethyl adipimidate HCL), active esters (such as disuccinimidyl suberate), aldehydes (such as glutareldehyde), bis-azido compounds (such as bis (p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (such as bis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (such as tolyene 2,6-diisocyanate), and bis-active fluorine compounds (such as 1,5-difluoro-2,4-dinitrobenzene). 
     Finally, fusion proteins can be constructed that comprise one or more anti-PRLR antibody moieties and another polypeptide. Methods of making antibody fusion proteins are well known in the art. See, e.g., U.S. Pat. No. 6,306,393. Antibody fusion proteins comprising an interleukin-2 moiety are described by Boleti et al., Ann. Oncol. 6:945 (1995), Nicolet et al., Cancer Gene Ther. 2:161 (1995), Becker et al., Proc. Nat&#39;l Acad. Sci. USA 93:7826 (1996), Hank et al., Clin. Cancer Res. 2:1951 (1996), and Hu et al., Cancer Res. 56:4998 (1996). 
     Combination Therapy 
     Having identified more than one PRLR antibody that is effective in an animal model, it may be further advantageous to mix two or more such PRLR antibodies together to provide still improved efficacy against cancer. Compositions comprising one or more PRLR antibody may be administered to persons or mammals suffering from, or predisposed to suffer from, cancer. A PRLR antibody may also be administered with another therapeutic agent, such as a cytotoxic agent, or cancer chemotherapeutic. Concurrent administration of two therapeutic agents does not require that the agents be administered at the same time or by the same route, as long as there is an overlap in the time period during which the agents are exerting their therapeutic effect. Simultaneous or sequential administration is contemplated, as is administration on different days or weeks. 
     The method of the invention contemplate the administration of single anti-PRLR antibodies, as well as combinations, or “cocktails”, of different antibodies. Such antibody cocktails may have certain advantages inasmuch as they contain antibodies which exploit different effector mechanisms or combine directly cytotoxic antibodies with antibodies that rely on immune effector functionality. Such antibodies in combination may exhibit synergistic therapeutic effects. 
     A cytotoxic agent refers to a substance that inhibits or prevents the function of cells and/or causes destruction of cells. The term is intended to include radioactive isotopes (e.g., I131, I125, Y90 and Re186), chemotherapeutic agents, and toxins such as enzymatically active toxins of bacterial, fungal, plant or animal origin or synthetic toxins, or fragments thereof. A non-cytotoxic agent refers to a substance that does not inhibit or prevent the function of cells and/or does not cause destruction of cells. A non-cytotoxic agent may include an agent that can be activated to be cytotoxic. A non-cytotoxic agent may include a bead, liposome, matrix or particle (see, e.g., U.S. Patent Publications 2003/0028071 and 2003/0032995 which are incorporated by reference herein). Such agents may be conjugated, coupled, linked or associated with an antibody according to the invention. 
     Cancer chemotherapeutic agents include, without limitation, alkylating agents, such as carboplatin and cisplatin; nitrogen mustard alkylating agents; nitrosourea alkylating agents, such as carmustine (BCNU); antimetabolites, such as methotrexate; folinic acid; purine analog antimetabolites, mercaptopurine; pyrimidine analog antimetabolites, such as fluorouracil (5-FU) and gemcitabine (Gemzar®); hormonal antineoplastics, such as goserelin, leuprolide, and tamoxifen; natural antineoplastics, such as aldesleukin, interleukin-2, docetaxel, etoposide (VP-16), interferon alfa, paclitaxel, (Taxol®), and tretinoin (ATRA); antibiotic natural antineoplastics, such as bleomycin, dactinomycin, daunorubicin, doxorubicin, daunomycin and mitomycins including mitomycin C; and vinca alkaloid natural antineoplastics, such as vinblastine, vincristine, vindesine; hydroxyurea; aceglatone, adriamycin, ifosfamide, enocitabine, epitiostanol, aclarubicin, ancitabine, nimustine, procarbazine hydrochloride, carboquone, carboplatin, carmofur, chromomycin A3, antitumor polysaccharides, antitumor platelet factors, cyclophosphamide (Cytoxin®), Schizophyllan, cytarabine (cytosine arabinoside), dacarbazine, thioinosine, thiotepa, tegafur, dolastatins, dolastatin analogs such as auristatin, CPT-11 (irinotecan), mitozantrone, vinorelbine, teniposide, aminopterin, caminomycin, esperamicins (See, e.g., U.S. Pat. No. 4,675,187), neocarzinostatin, OK-432, bleomycin, furtulon, broxuridine, busulfan, honvan, peplomycin, bestatin (Ubenimex®), interferon-β, mepitiostane, mitobronitol, melphalan, laminin peptides, lentinan,  Coriolus versicolor  extract, tegafur/uracil, estramustine (estrogen/mechlorethamine). Further, additional agents used as therapy for cancer patients include EPO, G-CSF, ganciclovir; antibiotics, leuprolide; meperidine; zidovudine (AZT); interleukins 1 through 18, including mutants and analogues; interferons or cytokines, such as interferons α, β, and γ hormones, such as luteinizing hormone releasing hormone (LHRH) and analogues and, gonadotropin releasing hormone (GnRH); growth factors, such as transforming growth factor-β (TGF-β), fibroblast growth factor (FGF), nerve growth factor (NGF), growth hormone releasing factor (GHRF), epidermal growth factor (EGF), fibroblast growth factor homologous factor (FGFHF), hepatocyte growth factor (HGF), and insulin growth factor (IGF); tumor necrosis factor-α &amp; β (TNF-α &amp; β); invasion inhibiting factor-2 (IIF-2); bone, morphogenetic proteins 1-7 (BMP 1-7); somatostatin; thymosin-α-1; γ-globulin; superoxide dismutase (SOD); complement factors; anti-angiogenesis factors; antigenic materials; and pro-drugs. 
     Prodrug refers to a precursor or derivative form of a pharmaceutically active substance that is less cytotoxic or non-cytotoxic to tumor cells compared to the parent drug and is capable of being enzymatically activated or converted into an active or the more active parent form. See, e.g., Wilman, “Prodrugs in Cancer Chemotherapy” Biochemical Society Transactions, 14, pp. 375-382, 615th Meeting Belfast (1986) and Stella et al., “Prodrugs: A Chemical Approach to Targeted Drug Delivery,” Directed Drug Delivery, Borchardt et al., (ed.), pp. 247-267, Humana Press (1985). Prodrugs include, but are not limited to, phosphate-containing prodrugs, thiophosphate-containing prodrugs, sulfate-containing prodrugs, peptide-containing prodrugs, D-amino acid-modified prodrugs, glycosylated prodrugs, □-lactam-containing prodrugs, optionally substituted phenoxyacetamide-containing prodrugs or optionally substituted phenylacetamide-containing prodrugs, 5-fluorocytosine and other 5-fluorouridine prodrugs which can be converted into the more active cytotoxic free drug. Examples of cytotoxic drugs that can be derivatized into a prodrug form for use herein include, but are not limited to, those chemotherapeutic agents described above. 
     Administration and Preparation 
     The anti-PRLR antibodies used in the practice of a method of the invention may be formulated into pharmaceutical compositions comprising a carrier suitable for the desired delivery method. Suitable carriers include any material which, when combined with the anti-PRLR antibodies, retains the anti-tumor function of the antibody and is nonreactive with the subject&#39;s immune systems. Examples include, but are not limited to, any of a number of standard pharmaceutical carriers such as sterile phosphate buffered saline solutions, bacteriostatic water, and the like. A variety of aqueous carriers may be used, e.g., water, buffered water, 0.4% saline, 0.3% glycine and the like, and may include other proteins for enhanced stability, such as albumin, lipoprotein, globulin, etc., subjected to mild chemical modifications or the like. 
     Therapeutic formulations of the antibody are prepared for storage by mixing the antibody having the desired degree of purity with optional physiologically acceptable carriers, excipients or stabilizers (Remington&#39;s Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980)), in the form of lyophilized formulations or aqueous solutions. Acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol); low molecular weight (less than about 10 residues) polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine, or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counter-ions such as sodium; metal complexes (e.g., Zn-protein complexes); and/or non-ionic surfactants such as TWEEN™, PLURONICS™ or polyethylene glycol (PEG). 
     The formulation herein may also contain more than one active compound as necessary for the particular indication being treated, preferably those with complementary activities that do not adversely affect each other. For example, it may be desirable to further provide an immunosuppressive agent. Such molecules are suitably present in combination in amounts that are effective for the purpose intended. 
     The active ingredients may also be entrapped in microcapsule prepared, for example, by coacervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or gelatin-microcapsule and poly-(methylmethacylate) microcapsule, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules) or in macroemulsions. Such techniques are disclosed in  Remington&#39;s Pharmaceutical Sciences  16th edition, Osol, A. Ed. (1980). 
     The formulations to be used for in vivo administration must be sterile. This is readily accomplished by filtration through sterile filtration membranes. 
     The antibody is administered by any suitable means, including parenteral, subcutaneous, intraperitoneal, intrapulmonary, and intranasal, and, if desired for local treatment, intralesional administration. Parenteral infusions include intravenous, intraarterial, intraperitoneal, intramuscular, intradermal or subcutaneous administration. In addition, the antibody is suitably administered by pulse infusion, particularly with declining doses of the antibody. Preferably the dosing is given by injections, most preferably intravenous or subcutaneous injections, depending in part on whether the administration is brief or chronic. Other administration methods are contemplated, including topical, particularly transdermal, transmucosal, rectal, oral or local administration e.g. through a catheter placed close to the desired site. 
     Compositions of the present invention can be in the form of, for example, granules, powders, tablets, capsules, syrup, suppositories, injections, emulsions, elixirs, suspensions or solutions. The instant compositions can be formulated for various routes of administration, for example, by oral administration, by nasal administration, by rectal administration, subcutaneous injection, intravenous injection, intramuscular injections, or intraperitoneal injection. The following dosage forms are given by way of example and should not be construed as limiting the instant invention. 
     Injectable dosage forms generally include aqueous suspensions or oil suspensions which may be prepared using a suitable dispersant or wetting agent and a suspending agent. Injectable forms may be in solution phase or in the form of a suspension, which is prepared with a solvent or diluent. Acceptable solvents or vehicles include sterilized water, Ringer&#39;s solution, or an isotonic aqueous saline solution. Alternatively, sterile oils may be employed as solvents or suspending agents. Preferably, the oil or fatty acid is non-volatile, including natural or synthetic oils, fatty acids, mono-, di- or tri-glycerides. 
     For injection, the pharmaceutical formulation and/or medicament may be a powder suitable for reconstitution with an appropriate solution as described above. Examples of these include, but are not limited to, freeze dried, rotary dried or spray dried powders, amorphous powders, granules, precipitates, or particulates. For injection, the formulations may optionally contain stabilizers, pH modifiers, surfactants, bioavailability modifiers and combinations of these. 
     Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semipermeable matrices of solid hydrophobic polymers containing the antibody, which matrices are in the form of shaped articles, e.g., films, or microcapsule. Examples of sustained-release matrices include polyesters, hydrogels (for example, poly(2-hydroxyethyl-methacrylate), or poly(vinylalcohol)), polylactides (U.S. Pat. No. 3,773,919), copolymers of L-glutamic acid and y ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradable lactic acid-glycolic acid copolymers such as the Lupron Depot™ (injectable microspheres composed of lactic acid-glycolic acid copolymer and leuprolide acetate), and poly-D-(−)-3-hydroxybutyric acid. While polymers such as ethylene-vinyl acetate and lactic acid-glycolic acid enable release of molecules for over 100 days, certain hydrogels release proteins for shorter time periods. When encapsulated antibodies remain in the body for a long time, they may denature or aggregate as a result of exposure to moisture at 37° C., resulting in a loss of biological activity and possible changes in immunogenicity. Rational strategies can be devised for stabilization depending on the mechanism involved. For example, if the aggregation mechanism is discovered to be intermolecular S—S bond formation through thio-disulfide interchange, stabilization may be achieved by modifying sulfhydryl residues, lyophilizing from acidic solutions, controlling moisture content, using appropriate additives, and developing specific polymer matrix compositions. 
     The formulations of the invention may be designed to be short-acting, fast-releasing, long-acting, or sustained-releasing as described herein. Thus, the pharmaceutical formulations may also be formulated for controlled release or for slow release. 
     The instant compositions may also comprise, for example, micelles or liposomes, or some other encapsulated form, or may be administered in an extended release form to provide a prolonged storage and/or delivery effect. Therefore, the pharmaceutical formulations and medicaments may be compressed into pellets or cylinders and implanted intramuscularly or subcutaneously as depot injections or as implants such as stents. Such implants may employ known inert materials such as silicones and biodegradable polymers. 
     Besides those representative dosage forms described above, pharmaceutically acceptable excipients and carries are generally known to those skilled in the art and are thus included in the instant invention. Such excipients and carriers are described, for example, in “Remingtons Pharmaceutical Sciences” Mack Pub. Co., New Jersey (1991), which is incorporated herein by reference. 
     Specific dosages may be adjusted depending on conditions of disease, the age, body weight, general health conditions, sex, and diet of the subject, dose intervals, administration routes, excretion rate, and combinations of drugs. Any of the above dosage forms containing effective amounts are well within the bounds of routine experimentation and therefore, well within the scope of the instant invention. 
     PRLR antibodies useful as therapeutics will often be prepared substantially free of other naturally occurring immunoglobulins or other biological molecules. Preferred PRLR antibodies will also exhibit minimal toxicity when administered to a subject in need thereof. 
     The compositions of the invention may be sterilized by conventional, well known sterilization techniques. The resulting solutions may be packaged for use or filtered under aseptic conditions and lyophilized, the lyophilized preparation being combined with a sterile solution prior to administration. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions, such as pH adjusting and buffering agents, tonicity adjusting agents and the like, for example, sodium acetate, sodium lactate, sodium chloride, potassium chloride, calcium chloride and stabilizers (e.g., 1 20% maltose, etc.). 
     The PRLR antibodies of the present invention may also be administered via liposomes, which are small vesicles composed of various types of lipids and/or phospholipids and/or surfactant which are useful for delivery of a drug (such as the antibodies disclosed herein and, optionally, a chemotherapeutic agent). Liposomes include emulsions, foams, micelles, insoluble monolayers, phospholipid dispersions, lamellar layers and the like, and can serve as vehicles to target the PRLR antibodies to a particular tissue as well as to increase the half life of the composition. A variety of methods are available for preparing liposomes, as described in, e.g., U.S. Pat. Nos. 4,837,028 and 5,019,369, which patents are incorporated herein by reference. 
     Liposomes containing the antibody are prepared by methods known in the art, such as described in Epstein et al., Proc. Natl. Acad. Sci. USA 82: 3688 (1985); Hwang et al., Proc. Natl. Acad. Sci. USA 77: 4030 (1980); and U.S. Pat. Nos. 4,485,045 and 4,544,545. Liposomes with enhanced circulation time are disclosed in U.S. Pat. No. 5,013,556. 
     Particularly useful liposomes can be generated by the reverse phase evaporation method with a lipid composition comprising phosphatidylcholine, cholesterol and PEG-derivatized phosphatidylethanolamine (PEG-PE). Liposomes are extruded through filters of defined pore size to yield liposomes with the desired diameter. Fab′ fragments of the antibody of the present invention can be conjugated to the liposomes as described in Martin et al., J. Biol. Chem. 257: 286-288 (1982) via a disulfide interchange reaction. A chemotherapeutic agent (such as Doxorubicin) is optionally contained within the liposome [see, e.g., Gabizon et al., J. National Cancer Inst. 81(19): 1484 (1989)]. 
     The concentration of the PRLR antibody in these compositions can vary widely, i.e., from less than about 10%, usually at least about 25% to as much as 75% or 90% by weight and will be selected primarily by fluid volumes, viscosities, etc., in accordance with the particular mode of administration selected. Actual methods for preparing orally, topically and parenterally administrable compositions will be known or apparent to those skilled in the art and are described in detail in, for example, Remington&#39;s Pharmaceutical Science, 19th ed., Mack Publishing Co., Easton, Pa. (1995), which is incorporated herein by reference. 
     Compositions of the invention are administered to a mammal already suffering from, or predisposed to, cancer in an amount sufficient to prevent or at least partially arrest the development of cancer. An amount adequate to accomplish this is defined as a “therapeutically effective dose.” Effective amounts of a PRLR antibody will vary and depend on the severity of the disease and the weight and general state of the patient being treated, but generally range from about 1.0 μg/kg to about 100 mg/kg body weight, or about 10 μg/kg to about 30 mg/kg, with dosages of from about 0.1 mg/kg to about 10 mg/kg or about 1 mg/kg to about 10 mg/kg per application being more commonly used. For example, about 10 μg/kg to 5 mg/kg or about 30 μg/kg to 1 mg/kg of antibody is an initial candidate dosage for administration to the patient, whether, for example, by one or more separate administrations, or by continuous infusion. Administration is daily, on alternating days, weekly or less frequently, as necessary depending on the response to the disease and the patient&#39;s tolerance of the therapy. Maintenance dosages over a longer period of time, such as 4, 5, 6, 7, 8, 10 or 12 weeks or longer may be needed until a desired suppression of disease symptoms occurs, and dosages may be adjusted as necessary. The progress of this therapy is easily monitored by conventional techniques and assays. 
     Single or multiple administrations of the compositions can be carried out with the dose levels and pattern being selected by the treating physician. For the prevention or treatment of disease, the appropriate dosage of antibody will depend on the type of disease to be treated, as defined above, the severity and course of the disease, whether the antibody is administered for preventive or therapeutic purposes, previous therapy, the patient&#39;s clinical history and response to the antibody, and the discretion of the attending physician. The antibody is suitably administered to the patient at one time or over a series of treatments. 
     The antibody composition will be formulated, dosed, and administered in a fashion consistent with good medical practice. Factors for consideration in this context include the particular disorder being treated, the particular mammal being treated, the clinical condition of the individual patient, the cause of the disorder, the site of delivery of the agent, the method of administration, the scheduling of administration, and other factors known to medical practitioners. The therapeutically effective amount of the antibody to be administered will be governed by such considerations, and is the minimum amount necessary to prevent, ameliorate, or treat the PRLR mediated disease, condition or disorder, particularly to treat cancer cells, and most particularly to treat tumor cell metastases. Such amount is preferably below the amount that is toxic to the host or renders the host significantly more susceptible to infections. 
     The antibody need not be, but is optionally formulated with one or more agents currently used to prevent or treat the disorder in question. For example, in cancer, the antibody may be given in conjunction with chemo therapeutic agent or in ADEPT as described above. The effective amount of such other agents depends on the amount of antibody present in the formulation, the type of disease, condition or disorder or treatment, and other factors discussed above. These are generally used in the same dosages and with administration routes as used hereinbefore or about from 1 to 99% of the heretofore employed dosages. 
     In another embodiment of the invention, an article of manufacture containing materials useful for the treatment of the diseases, disorders or conditions described above is provided, including for treatment of cancer. The article of manufacture comprises a container and a label. Suitable containers include, for example, bottles, vials, syringes, and test tubes. The containers may be formed from a variety of materials such as glass or plastic. The container holds a composition which is effective for treating the condition and may have a sterile access port (for example the container may be an intravenous solution bag or a vial having a stopper pierceable by a hypodermic injection needle). The active agent in the composition is the antibody of the invention. The label on, or associated with, the container indicates that the composition is used for treating the condition of choice. The article of manufacture may further comprise a second container comprising a pharmaceutically-acceptable buffer, such as phosphate-buffered saline, Ringer&#39;s solution and dextrose solution. It may further include other materials desirable from a commercial and user standpoint, including other buffers, diluents, filters, needles, syringes, and package inserts with instructions for use. 
     Labelling 
     In one embodiment, the PRLR nucleic acids, proteins and antibodies of the invention are labeled. By “labeled” herein is meant that a compound has at least one element, isotope or chemical compound attached to enable the detection of the compound. In general, labels fall into three classes: a) isotopic labels, which may be radioactive or heavy isotopes; b) immune labels, which may be antibodies or antigens; and c) coloured or fluorescent dyes. The labels may be incorporated into the PRLR nucleic acids, proteins and antibodies at any position. For example, the label should be capable of producing, either directly or indirectly, a detectable signal. The detectable moiety may be a radioisotope, such as  3 H,  14 C,  32 P,  35 S, or  125 I, a fluorescent or chemiluminescent compound, such as fluorescein isothiocyanate, rhodamine, or luciferin, or an enzyme, such as alkaline phosphatase, beta-galactosidase or horseradish peroxidase. Any method known in the art for conjugating the antibody to the label may be employed, including those methods described by Hunter et al., Nature, 144:945 (1962); David et al., Biochemistry, 13:1014 (1974); Pain et al., J. Immunol. Meth., 40:219 (1981); and Nygren, J. Histochem. and Cytochem., 30:407 (1982). 
     Detection of Cancer Phenotype 
     Once expressed and, if necessary, purified, the PRLR proteins and nucleic acids are useful in a number of applications. In one aspect, the expression levels of genes are determined for different cellular states in the cancer phenotype; that is, the expression levels of genes in normal tissue and in cancer tissue (and in some cases, for varying severities of lymphoma that relate to prognosis, as outlined below) are evaluated to provide expression profiles. An expression profile of a particular cell state or point of development is essentially a “fingerprint” of the state; while two states may have any particular gene similarly expressed, the evaluation of a number of genes simultaneously allows the generation of a gene expression profile that is unique to the state of the cell. By comparing expression profiles of cells in different states, information regarding which genes are important (including both up- and down-regulation of genes) in each of these states is obtained. Then, diagnosis may be done or confirmed: does tissue from a particular patient have the gene expression profile of normal or cancer tissue. 
     “Differential expression,” or equivalents used herein, refers to both qualitative as well as quantitative differences in the temporal and/or cellular expression patterns of genes, within and among the cells. Thus, a differentially expressed gene can qualitatively have its expression altered, including an activation or inactivation, in, for example, normal versus cancer tissue. That is, genes may be turned on or turned off in a particular state, relative to another state. As is apparent to the skilled artisan, any comparison of two or more states can be made. Such a qualitatively regulated gene will exhibit an expression pattern within a state or cell type which is detectable by standard techniques in one such state or cell type, but is not detectable in both. Alternatively, the determination is quantitative in that expression is increased or decreased; that is, the expression of the gene is either up-regulated, resulting in an increased amount of transcript, or down-regulated, resulting in a decreased amount of transcript. The degree to which expression differs need only be large enough to quantify via standard characterization techniques as outlined below, such as by use of Affymetrix GeneChip® expression arrays, Lockhart, Nature Biotechnology, 14:1675-1680 (1996), hereby expressly incorporated by reference. Other techniques include, but are not limited to, quantitative reverse transcriptase PCR, Northern analysis and RNase protection. As outlined above, preferably the change in expression (i.e. upregulation or downregulation) is at least about 2-fold, 3-fold, 5-fold, 10-fold, 20-fold, 50-fold, or even 100 fold or more. 
     As will be appreciated by those in the art, this may be done by evaluation at either the gene transcript, or the protein level; that is, the amount of gene expression may be monitored using nucleic acid probes to the DNA or RNA equivalent of the gene transcript, and the quantification of gene expression levels, or, alternatively, the final gene product itself (protein) can be monitored, for example through the use of antibodies to the PRLR protein and standard immunoassays (ELISAs, etc.) or other techniques, including mass spectroscopy assays, 2D gel electrophoresis assays, etc. Thus, the proteins corresponding to PRLR genes, i.e. those identified as being important in a particular cancer phenotype, can be evaluated in a diagnostic test specific for that cancer. 
     In an embodiment, gene expression monitoring is done and a number of genes are monitored simultaneously. However, multiple protein expression monitoring can be done as well to prepare an expression profile. Alternatively, these assays may be done on an individual basis. 
     In one embodiment, the PRLR nucleic acid probes may be attached to biochips as outlined herein for the detection and quantification of PRLR sequences in a particular cell. The assays are done as is known in the art. As will be appreciated by those in the art, any number of different PRLR sequences may be used as probes, with single sequence assays being used in some cases, and a plurality of the sequences described herein being used in other embodiments. In addition, while solid-phase assays are described, any number of solution based assays may be done as well. 
     In an embodiment, both solid and solution based assays may be used to detect PRLR sequences that are up-regulated or down-regulated in cancers as compared to normal tissue. In instances where the PRLR sequence has been altered but shows the same expression profile or an altered expression profile, the protein will be detected as outlined herein. 
     In an embodiment nucleic acids encoding the PRLR protein are detected. Although DNA or RNA encoding the PRLR protein may be detected, of particular interest are methods wherein the mRNA encoding a PRLR protein is detected. The presence of mRNA in a sample is an indication that the PRLR gene has been transcribed to form the mRNA, and suggests that the protein is expressed. Probes to detect the mRNA can be any nucleotide/deoxynucleotide probe that is complementary to and base pairs with the mRNA and includes but is not limited to oligonucleotides, cDNA or RNA. Probes also should contain a detectable label, as defined herein. In one method the mRNA is detected after immobilizing the nucleic acid to be examined on a solid support such as nylon membranes and hybridizing the probe with the sample. Following washing to remove the non-specifically bound probe, the label is detected. In another method detection of the mRNA is performed in situ. In this method permeabilized cells or tissue samples are contacted with a detectably labeled nucleic acid probe for sufficient time to allow the probe to hybridize with the target mRNA. Following washing to remove the non-specifically bound probe, the label is detected. For example a digoxygenin labeled riboprobe (RNA probe) that is complementary to the mRNA encoding a PRLR protein is detected by binding the digoxygenin with an anti-digoxygenin secondary antibody and developed with nitro blue tetrazolium and 5-bromo-4-chloro-3-indoyl phosphate. 
     Any of the three classes of proteins as described herein (secreted, transmembrane or intracellular proteins) may be used in diagnostic assays. The PRLR proteins, antibodies, nucleic acids, modified proteins and cells containing PRLR sequences are used in diagnostic assays. This can be done on an individual gene or corresponding polypeptide level, or as sets of assays. 
     As described and defined herein, PRLR proteins find use as markers of cancers. Detection of these proteins in putative cancer tissue or patients allows for a determination or diagnosis of the type of cancer. Numerous methods known to those of ordinary skill in the art find use in detecting cancers. 
     Antibodies may be used to detect PRLR proteins. One method separates proteins from a sample or patient by electrophoresis on a gel (typically a denaturing and reducing protein gel, but may be any other type of gel including isoelectric focusing gels and the like). Following separation of proteins, the PRLR protein is detected by immunoblotting with antibodies raised against the PRLR protein. Methods of immunoblotting are well known to those of ordinary skill in the art. The antibodies used in such methods may be labeled as described above. 
     In another method, antibodies to the PRLR protein find use in in situ imaging techniques. In this method cells are contacted with from one to many antibodies to the PRLR protein(s). Following washing to remove non-specific antibody binding, the presence of the antibody or antibodies is detected. In one embodiment the antibody is detected by incubating with a secondary antibody that contains a detectable label. In another method the primary antibody to the PRLR protein(s) contains a detectable label. In another method, each one of multiple primary antibodies contains a distinct and detectable label. This method finds particular use in simultaneous screening for a plurality of PRLR proteins. As will be appreciated by one of ordinary skill in the art, numerous other histological imaging techniques are useful in the invention. 
     The label may be detected in a fluorometer that has the ability to detect and distinguish emissions of different wavelengths. In addition, a fluorescence activated cell sorter (FACS) can be used in the method. 
     Antibodies may be used in diagnosing cancers from blood samples. As previously described, certain PRLR proteins are secreted/circulating molecules. Blood samples, therefore, are useful as samples to be probed or tested for the presence of secreted PRLR proteins. Antibodies can be used to detect the PRLR proteins by any of the previously described immunoassay techniques including ELISA, immunoblotting (Western blotting), immunoprecipitation, BIACORE technology and the like, as will be appreciated by one of ordinary skill in the art. 
     In situ hybridization of labeled PRLR nucleic acid probes to tissue arrays may be carried out. For example, arrays of tissue samples, including cancer tissue and/or normal tissue, are made. In situ hybridization as is known in the art can then be done. 
     It is understood that when comparing the expression fingerprints between an individual and a standard, the skilled artisan can make a diagnosis as well as a prognosis. It is further understood that the genes that indicate diagnosis may differ from those that indicate prognosis. 
     As noted above, the PRLR proteins, antibodies, nucleic acids, modified proteins and cells containing PRLR sequences can be used in prognosis assays. As above, gene expression profiles can be generated that correlate to cancer, especially lymphoma, severity, in terms of long term prognosis. Again, this may be done on either a protein or gene level, with the use of genes being preferred. As above, the PRLR probes are attached to biochips for the detection and quantification of PRLR sequences in a tissue or patient. The assays proceed as outlined for diagnosis. 
     Screening for Drugs Targeted to the PRLR Gene and Expression Products 
     Any of the cPRLR gene sequences as described herein may be used in drug screening assays. The PRLR proteins, antibodies, nucleic acids, modified proteins and cells containing PRLR gene sequences are used in drug screening assays or by evaluating the effect of drug candidates on a “gene expression profile” or expression profile of polypeptides. In one method, the expression profiles are used, preferably in conjunction with high throughput screening techniques to allow monitoring for expression profile genes after treatment with a candidate agent, Zlokarnik, et al., Science 279, 84-8 (1998), Heid, et al., Genome Res., 6:986-994 (1996). 
     In another method, the PRLR proteins, antibodies, nucleic acids, modified proteins and cells containing the native or modified PRLR proteins are used in screening assays. That is, the present invention provides novel methods for screening for compositions that modulate the cancer phenotype. As above, this can be done by screening for modulators of gene expression or for modulators of protein activity. Similarly, this may be done on an individual gene or protein level or by evaluating the effect of drug candidates on a “gene expression profile”. In an embodiment, the expression profiles are used, preferably in conjunction with high throughput screening techniques to allow monitoring for expression profile genes after treatment with a candidate agent, see Zlokarnik, supra. 
     A variety of assays to evaluate the effects of agents on PRLR gene expression may be executed. In an embodiment, assays may be run on an individual gene or protein level. That is, having identified a particular gene as aberrantly regulated in cancer, candidate bioactive agents may be screened to modulate the gene&#39;s regulation. “Modulation” thus includes both an increase and a decrease in gene expression or activity. The preferred amount of modulation will depend on the original change of the gene expression in normal versus tumor tissue, with changes of at least 10%, preferably 50%, more preferably 100-300%, and in some embodiments 300-1000% or greater. Thus, if a gene exhibits a 4-fold increase in tumor compared to normal tissue, a decrease of about four fold is desired; a 10-fold decrease in tumor compared to normal tissue gives a 10-fold increase in expression for a candidate agent is desired, etc. Alternatively, where the PRLR sequence has been altered but shows the same expression profile or an altered expression profile, the protein will be detected as outlined herein. 
     As will be appreciated by those in the art, this may be done by evaluation at either the gene or the protein level; that is, the amount of gene expression may be monitored using nucleic acid probes and the quantification of gene expression levels, or, alternatively, the level of the gene product itself can be monitored, for example through the use of antibodies to the PRLR protein and standard immunoassays. Alternatively, binding and bioactivity assays with the protein may be done as outlined below. 
     In an embodiment, a number of genes are monitored simultaneously, i.e. an expression profile is prepared, although multiple protein expression monitoring can be done as well. 
     In this embodiment, the PRLR nucleic acid probes are attached to biochips as outlined herein for the detection and quantification of PRLR sequences in a particular cell. The assays are further described below. 
     Generally, in a preferred method, a candidate bioactive agent is added to the cells prior to analysis. Moreover, screens are provided to identify a candidate bioactive agent that modulates a particular type of cancer, modulates PRLR proteins, binds to a PRLR protein, or interferes between the binding of a PRLR protein and an antibody. 
     The term “candidate bioactive agent” or “drug candidate” or grammatical equivalents as used herein describes any molecule, e.g., protein, oligopeptide, small organic or inorganic molecule, polysaccharide, polynucleotide, etc., to be tested for bioactive agents that are capable of directly or indirectly altering either the cancer phenotype, binding to and/or modulating the bioactivity of a PRLR protein, or the expression of a PRLR sequence, including both nucleic acid sequences and protein sequences. In one embodiment, the candidate agent suppresses a PRLR phenotype, for example to a normal tissue fingerprint. Similarly, the candidate agent preferably suppresses a severe PRLR cancer-associated phenotype. Generally a plurality of assay mixtures are run in parallel with different agent concentrations to obtain a differential response to the various concentrations. Typically, one of these concentrations serves as a negative control, i.e., at zero concentration or below the level of detection. 
     Preferably, a candidate agent will neutralize the effect of a PRLR protein. By “neutralize” is meant that activity of a protein is either inhibited or counter acted against so as to have substantially no effect on a cell and hence reduce the severity of cancer, or prevent the incidence of cancer. 
     Candidate agents encompass numerous chemical classes, though typically they are organic or inorganic molecules, preferably small organic compounds having a molecular weight of more than 100 and less than about 2,500 Daltons. Preferred small molecules are less than 2000, or less than 1500 or less than 1000 or less than 500 Da. Candidate agents comprise functional groups necessary for structural interaction with proteins, particularly hydrogen bonding, and typically include at least an amine, carbonyl, hydroxyl or carboxyl group, preferably at least two of the functional chemical groups. The candidate agents often comprise cyclical carbon or heterocyclic structures and/or aromatic or polyaromatic structures substituted with one or more of the above functional groups. Candidate agents are also found among biomolecules including peptides, saccharides, fatty acids, steroids, purines, pyrimidines, derivatives, structural analogs or combinations thereof. Particularly preferred are peptides. 
     Candidate agents are obtained from a wide variety of sources including libraries of synthetic or natural compounds. For example, numerous means are available for random and directed synthesis of a wide variety of organic compounds and biomolecules, including expression of randomized oligonucleotides. Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant and animal extracts are available or readily produced. Additionally, natural or synthetically produced libraries and compounds are readily modified through conventional chemical, physical and biochemical means. Known pharmacological agents may be subjected to directed or random chemical modifications, such as acylation, alkylation, esterification, or amidification to produce structural analogs. 
     In one embodiment, the candidate bioactive agents are proteins. By “protein” herein is meant at least two covalently attached amino acids, which includes proteins, polypeptides, oligopeptides and peptides. The protein may be made up of naturally occurring amino acids and peptide bonds, or synthetic peptidomimetic structures. Thus “amino acid”, or “peptide residue”, as used herein means both naturally occurring and synthetic amino acids. For example, homo-phenylalanine, citrulline and norleucine are considered amino acids for the purposes of the invention. “Amino acid” also includes imino acid residues such as proline and hydroxyproline. The side chains may be in either the (R) or the (S) configuration. In one embodiment, the amino acids are in the (S) or L-configuration. If non-naturally occurring side chains are used, non-amino acid substituents may be used, for example to prevent or retard in vivo degradations. 
     In an embodiment, the candidate bioactive agents are naturally occurring proteins or fragments of naturally occurring proteins. Thus, for example, cellular extracts containing proteins, or random or directed digests of proteinaceous cellular extracts, may be used. In this way libraries of prokaryotic and eukaryotic proteins may be made for screening in the methods of the invention. Particularly preferred in this embodiment are libraries of bacterial, fungal, viral, and mammalian proteins, with the latter being preferred, and human proteins being especially preferred. 
     In another embodiment, the candidate bioactive agents are peptides of from about 5 to about 30 amino acids, with from about 5 to about 20 amino acids being preferred, and from about 7 to about 15 being particularly preferred. The peptides may be digests of naturally occurring proteins as is outlined above, random peptides, or “biased” random peptides. By “randomized” or grammatical equivalents herein is meant that each nucleic acid and peptide consists of essentially random nucleotides and amino acids, respectively. Since generally these random peptides (or nucleic acids, discussed below) are chemically synthesized, they may incorporate any nucleotide or amino acid at any position. The synthetic process can be designed to generate randomized proteins or nucleic acids, to allow the formation of all or most of the possible combinations over the length of the sequence, thus forming a library of randomized candidate bioactive proteinaceous agents. 
     In one embodiment, the library is fully randomized, with no sequence preferences or constants at any position. In an embodiment, the library is biased. That is, some positions within the sequence are either held constant, or are selected from a limited number of possibilities. For example, in one embodiment, the nucleotides or amino acid residues are randomized within a defined class, for example, of hydrophobic amino acids, hydrophilic residues, sterically biased (either small or large) residues, towards the creation of nucleic acid binding domains, the creation of cysteines, for cross-linking, prolines for SH-3 domains, serines, threonines, tyrosines or histidines for phosphorylation sites, etc., or to purines, etc. 
     In one embodiment, the candidate bioactive agents are nucleic acids. As described generally for proteins, nucleic acid candidate bioactive agents may be naturally occurring nucleic acids, random nucleic acids, or “biased” random nucleic acids. In another embodiment, the candidate bioactive agents are organic chemical moieties, a wide variety of which are available in the literature. 
     In assays for testing alteration of the expression profile of other PRLR gene, after the candidate agent has been added and the cells allowed to incubate for some period of time, a nucleic acid sample containing the target sequences to be analyzed is prepared. The target sequence is prepared using known techniques (e.g., converted from RNA to labeled cDNA, as described above) and added to a suitable microarray. For example, an in vitro reverse transcription with labels covalently attached to the nucleosides is performed. Generally, the nucleic acids are labeled with a label as defined herein, especially with biotin-FITC or PE, Cy3 and Cy5. 
     As will be appreciated by those in the art, these assays can be direct hybridization assays or can comprise “sandwich assays”, which include the use of multiple probes, as is generally outlined in U.S. Pat. Nos. 5,681,702, 5,597,909, 5,545,730, 5,594,117, 5,591,584, 5,571,670, 5,580,731, 5,571,670, 5,591,584, 5,624,802, 5,635,352, 5,594,118, 5,359,100, 5,124,246 and 5,681,697, all of which are hereby incorporated by reference. In this embodiment, in general, the target nucleic acid is prepared as outlined above, and then added to the biochip comprising a plurality of nucleic acid probes, under conditions that allow the formation of a hybridization complex. 
     A variety of hybridization conditions may be used in the present invention, including high, moderate and low stringency conditions as outlined above. The assays are generally run under stringency conditions that allow formation of the label probe hybridization complex only in the presence of target. Stringency can be controlled by altering a step parameter that is a thermodynamic variable, including, but not limited to, temperature, formamide concentration, salt concentration, chaotropic salt concentration, pH, organic solvent concentration, etc. These parameters may also be used to control non-specific binding, as is generally outlined in U.S. Pat. No. 5,681,697. Thus it may be desirable to perform certain steps at higher stringency conditions to reduce non-specific binding. 
     The reactions outlined herein may be accomplished in a variety of ways, as will be appreciated by those in the art. Components of the reaction may be added simultaneously, or sequentially, in any order, with suggested embodiments outlined below. In addition, the reaction may include a variety of other reagents in the assays. These include reagents like salts, buffers, neutral proteins, e.g. albumin, detergents, etc which may be used to facilitate optimal hybridization and detection, and/or reduce non-specific or background interactions. Also reagents that otherwise improve the efficiency of the assay, such as protease inhibitors, nuclease inhibitors, anti-microbial agents, etc., may be used, depending on the sample preparation methods and purity of the target. In addition, either solid phase or solution based (i.e., kinetic PCR) assays may be used. 
     Once the assay is run, the data are analyzed to determine the expression levels, and changes in expression levels as between states, of individual genes, forming a gene expression profile. 
     In an embodiment, as for the diagnosis and prognosis applications, having identified the differentially expressed gene(s) or mutated gene(s) important in any one state, screens can be run to test for alteration of the expression of the PRLR genes individually. That is, screening for modulation of regulation of expression of a single gene can be done. Thus, for example, in the case of target genes whose presence or absence is unique between two states, screening is done for modulators of the target gene expression. 
     In addition, screens can be done for novel genes that are induced in response to a candidate agent. After identifying a candidate agent based upon its ability to suppress a PRLR expression pattern leading to a normal expression pattern, or modulate a PRLR gene expression profile so as to mimic the expression of the gene from normal tissue, a screen as described above can be performed to identify genes that are specifically modulated in response to the agent. Comparing expression profiles between normal tissue and agent treated tissue reveals genes that are not expressed in normal tissue or cancer tissue, but are expressed in agent treated tissue. These agent specific sequences can be identified and used by any of the methods described herein for the PRLR gene or proteins. In particular these sequences and the proteins they encode find use in marking or identifying agent-treated cells. In addition, antibodies can be raised against the agent-induced proteins and used to target novel therapeutics to the treated tissue sample. 
     Thus, in one embodiment, a candidate agent is administered to a population of cancer-associated cells, that has an associated PRLR expression profile. By “administration” or “contacting” herein is meant that the candidate agent is added to the cells in such a manner as to allow the agent to act upon the cell, whether by uptake and intracellular action, or by action at the cell surface. In some embodiments, nucleic acid encoding a proteinaceous candidate agent (i.e. a peptide) may be put into a viral construct such as a retroviral construct and added to the cell, such that expression of the peptide agent is accomplished; see PCT US97/01019, hereby expressly incorporated by reference. 
     Once the candidate agent has been administered to the cells, the cells can be washed if desired and are allowed to incubate under preferably, physiological conditions for some period of time. The cells are then harvested and a new gene expression profile is generated, as outlined herein. 
     Thus, for example, cancer tissue may be screened for agents that reduce or suppress the PRLR-associated phenotype. A change in at least one gene of the expression profile indicates that the agent has an effect on PRLR activity. By defining such a signature for the PRLR-associated phenotype, screens for new drugs that alter the phenotype can be devised. With this approach, the drug target need not be known and need not be represented in the original expression screening platform, nor does the level of transcript for the target protein need to change. 
     In an embodiment, as outlined above, screens may be done on individual genes and gene products (proteins). That is, having identified a particular differentially expressed gene as important in a particular state, screening of modulators of either the expression of the gene or the gene product itself can be done. The PRLR protein may be a fragment, or alternatively, be the full-length protein to the fragment encoded by the PRLR gene recited above. In another embodiment, the sequences are sequence variants as further described above. 
     Preferably, the PRLR protein is a fragment approximately 14 to 24 amino acids in length. More preferably the fragment is a soluble fragment. Preferably, the fragment includes a non-transmembrane region. In an embodiment, the fragment has an N-terminal Cys to aid in solubility. In one embodiment, the C-terminus of the fragment is kept as a free; acid and the N-terminus is a free amine to aid in coupling, e.g., to a cysteine. 
     In one embodiment the PRLR proteins are conjugated to an immunogenic agent as discussed herein. In one embodiment the PRLR protein is conjugated to BSA. 
     In an embodiment, screening is done to alter the biological function of the expression product of the PRLR gene. Again, having identified the importance of a gene in a particular state, screening for agents that bind and/or modulate the biological activity of the gene product can be run as is more fully outlined below. 
     In an embodiment, screens are designed to first find candidate agents that can bind to PRLR proteins, and then these agents may be used in assays that evaluate the ability of the candidate agent to modulate the PRLR protein activity and the cancer phenotype. Thus, as will be appreciated by those in the art, there are a number of different assays that may be run; binding assays and activity assays. 
     In an embodiment, binding assays are done. In general, purified or isolated gene product is used; that is, the gene products of one or more PRLR nucleic acids are made. In general, this is done as is known in the art. For example, antibodies are generated to the protein gene products, and standard immunoassays are run to determine the amount of protein present. Alternatively, cells comprising the PRLR proteins can be used in the assays. 
     Thus, in an embodiment, the methods comprise combining a PRLR protein and a candidate bioactive agent, and determining the binding of the candidate agent to the PRLR protein. Some embodiments utilize the human or mouse PRLR protein, although other mammalian proteins may also be used, for example for the development of animal models of human disease. In some embodiments, as outlined herein, variant or derivative PRLR proteins may be used. 
     Generally, in one embodiment of the methods herein, the PRLR protein or the candidate agent is non-diffusably bound to an insoluble support having isolated sample receiving areas (e.g. a microtiter plate, an array, etc.). The insoluble support may be made of any composition to which the compositions can be bound, is readily separated from soluble material, and is otherwise compatible with the overall method of screening. The surface of such supports may be solid or porous and of any convenient shape. Examples of suitable insoluble supports include microtiter plates, arrays, membranes and beads. These are typically made of glass, plastic (e.g., polystyrene), polysaccharides, nylon or nitrocellulose, Teflon®, etc. Microtiter plates and arrays are especially convenient because a large number of assays can be carried out simultaneously, using small amounts of reagents and samples. 
     The particular manner of binding of the composition is not crucial so long as it is compatible with the reagents and overall methods of the invention, maintains the activity of the composition and is nondiffusable. Preferred methods of binding include the use of antibodies (which do not sterically block either the ligand binding site or activation sequence when the protein is bound to the support), direct binding to “sticky” or ionic supports, chemical crosslinking, the synthesis of the protein or agent on the surface, etc. Following binding of the protein or agent, excess unbound material is removed by washing. The sample receiving areas may then be blocked through incubation with bovine serum albumin (BSA), casein or other innocuous protein or other moiety. 
     In an embodiment, the PRLR protein is bound to the support, and a candidate bioactive agent is added to the assay. Alternatively, the candidate agent is bound to the support and the PRLR protein is added. Novel binding agents include specific antibodies, non-natural binding agents identified in screens of chemical libraries or peptide analogs. Of particular interest are screening assays for agents that have a low toxicity for human cells. A wide variety of assays may be used for this purpose, including labeled in vitro protein-protein binding assays, electrophoretic mobility shift assays, immunoassays for protein binding, functional assays (phosphorylation assays, etc.) and the like. 
     The determination of the binding of the candidate bioactive agent to the PRLR protein may be done in a number of ways. In an embodiment, the candidate bioactive agent is labeled, and binding determined directly. For example, this may be done by attaching all or a portion of the PRLR protein to a solid support, adding a labeled candidate agent (for example a fluorescent label), washing off excess reagent, and determining whether the label is present on the solid support. Various blocking and washing steps may be utilized as is known in the art. 
     In some embodiments, only one of the components is labeled. For example, the proteins (or proteinaceous candidate agents) may be labeled at tyrosine positions using  125 I, or with fluorophores. Alternatively, more than one component may be labeled with different labels; using  125 I for the proteins, for example, and a fluorophore for the candidate agents. 
     In an embodiment, the binding of the candidate bioactive agent is determined through the use of competitive binding assays. In this embodiment, the competitor is a binding moiety known to bind to the target molecule (i.e. PRLR protein), such as an antibody, peptide, binding partner, ligand, etc. Under certain circumstances, there may be competitive binding as between the bioactive agent and the binding moiety, with the binding moiety displacing the bioactive agent. 
     In one embodiment, the candidate bioactive agent is labeled. Either the candidate bioactive agent, or the competitor, or both, is added first to the protein for a time sufficient to allow binding, if present. Incubations may be performed at any temperature which facilitates optimal activity, typically between 4 and 40° C. Incubation periods are selected for optimum activity, but may also be optimized to facilitate rapid high throughput screening. Typically between 0.1 and 1 hour will be sufficient. Excess reagent is generally removed or washed away. The second component is then added, and the presence or absence of the labeled component is followed, to indicate binding. 
     In an embodiment, the competitor is added first, followed by the candidate bioactive agent. Displacement of the competitor is an indication that the candidate bioactive agent is binding to the PRLR protein and thus is capable of binding to, and potentially modulating, the activity of the PRLR protein. In this embodiment, either component can be labeled. Thus, for example, if the competitor is labeled, the presence of label in the wash solution indicates displacement by the agent. Alternatively, if the candidate bioactive agent is labeled, the presence of the label on the support indicates displacement. 
     In an alternative embodiment, the candidate bioactive agent is added first, with incubation and washing, followed by the competitor. The absence of binding by the competitor may indicate that the bioactive agent is bound to the PRLR protein with a higher affinity. Thus, if the candidate bioactive agent is labeled, the presence of the label on the support, coupled with a lack of competitor binding, may indicate that the candidate agent is capable of binding to the PRLR protein. 
     In an embodiment, the methods comprise differential screening to identity bioactive agents that are capable of modulating the activity of the PRLR proteins. In this embodiment, the methods comprise combining a PRLR protein and a competitor in a first sample. A second sample comprises a candidate bioactive agent, a PRLR protein and a competitor. The binding of the competitor is determined for both samples, and a change, or difference in binding between the two samples indicates the presence of an agent capable of binding to the PRLR protein and potentially modulating its activity. That is, if the binding of the competitor is different in the second sample relative to the first sample, the agent is capable of binding to the PRLR protein. 
     Alternatively, an embodiment utilizes differential screening to identify drug candidates that bind to the native PRLR protein, but cannot bind to modified PRLR proteins. The structure of the PRLR protein may be modeled, and used in rational drug design to synthesize agents that interact with that site. Drug candidates that affect PRLR bioactivity are also identified by screening drugs for the ability to either enhance or reduce the activity of the protein. 
     Positive controls and negative controls may be used in the assays. Preferably all control and test samples are performed in at least triplicate to obtain statistically significant results. Incubation of all samples is for a time sufficient for the binding of the agent to the protein. Following incubation, all samples are washed free of non-specifically bound material and the amount of bound, generally labeled agent determined. For example, where a radiolabel is employed, the samples may be counted in a scintillation counter to determine the amount of bound compound. 
     A variety of other reagents may be included in the screening assays. These include reagents like salts, neutral proteins, e.g. albumin, detergents, etc which may be used to facilitate optimal protein-protein binding and/or reduce non-specific or background interactions. Also reagents that otherwise improve the efficiency of the assay, such as protease inhibitors, nuclease inhibitors, anti-microbial agents, etc., may be used. The mixture of components may be added in any order that provides for the requisite binding. 
     Screening for agents that modulate the activity of PRLR proteins may also be done. In an embodiment, methods for screening for a bioactive agent capable of modulating the activity of PRLR proteins comprise adding a candidate bioactive agent to a sample of PRLR proteins, as above, and determining an alteration in the biological activity of PRLR proteins. “Modulating the activity of a PRLR protein” includes an increase in activity, a decrease in activity, or a change in the type or kind of activity present. Thus, in this embodiment, the candidate agent should both bind to PRLR proteins (although this may not be necessary), and alter its biological or biochemical activity as defined herein. The methods include both in vitro screening methods, as are generally outlined above, and in vivo screening of cells for alterations in the presence, distribution, activity or amount of PRLR proteins. 
     Thus, in this embodiment, the methods comprise combining a PRLR sample and a candidate bioactive agent, and evaluating the effect on PRLR activity. By “PRLR activity” or grammatical equivalents herein is meant one of the PRLR protein&#39;s biological activities, including, but not limited to, its role in tumorigenesis, including cell division, preferably in lymphatic tissue, cell proliferation, tumor growth and transformation of cells. In one embodiment, PRLR activity includes activation of or by a protein encoded by a nucleic acid derived, from the PRLR gene as identified above. An inhibitor of PRLR activity is the inhibition of any one or more PRLR activities. 
     In one embodiment, the activity of the PRLR protein is increased; in another embodiment, the activity of the PRLR protein is decreased. Thus, bioactive agents that are antagonists are preferred in some embodiments, and bioactive agents that are agonists may be preferred in other embodiments. 
     In one embodiment, the invention provides methods for screening for bioactive agents capable of modulating the activity of a PRLR protein. The methods comprise adding a candidate bioactive agent, as defined above, to a cell comprising PRLR proteins. Preferred cell types include almost any cell. The cells contain a recombinant nucleic acid that encodes a PRLR protein. In one embodiment, a library of candidate agents is tested on a plurality of cells. 
     In one aspect, the assays are evaluated in the presence or absence or previous or subsequent exposure of physiological signals, for example hormones, antibodies, peptides, antigens, cytokines, growth factors, action potentials, pharmacological agents including chemotherapeutics, radiation, carcinogenics, or other cells (i.e. cell-cell contacts). In another example, the determinations are determined at different stages of the cell cycle process. 
     In this way, bioactive agents are identified. Compounds with pharmacological activity are able to enhance or interfere with the activity of the PRLR protein. 
     The Diagnosis and Treatment of Cancer 
     Methods of inhibiting cancer cell division are provided by the invention. In another embodiment, methods of inhibiting tumor growth are provided. In a further embodiment, methods of treating cells or individuals with cancer are provided. 
     The methods may comprise the administration of a cancer inhibitor. In particular embodiments, the cancer inhibitor is an antisense molecule, a pharmaceutical composition, a therapeutic agent or small molecule, or a monoclonal, polyclonal, chimeric or humanized antibody. In particular embodiments, a therapeutic agent is coupled with an antibody, preferably a monoclonal antibody. 
     Methods for detection or diagnosis of cancer cells in an individual are also provided. In particular embodiments, the diagnostic/detection agent is a small molecule that preferentially binds to a PRLR protein according to the invention. In one embodiment, the diagnostic/detection agent is an antibody, preferably a monoclonal antibody, preferably linked to a detectable agent. 
     In other embodiments of the invention, animal models and transgenic animals are provided, which find use in generating animal models of cancers, particularly lymphomas and carcinomas. 
     (a) Antisense Molecules 
     The cancer inhibitor used may be an antisense molecule. Antisense molecules as used herein include antisense or sense oligonucleotides comprising a single-stranded nucleic acid sequence (either RNA or DNA) capable of binding to target mRNA (sense) or DNA (antisense) sequences for cancer molecules. Antisense or sense oligonucleotides, according to the present invention, comprise a fragment generally at least about 14 nucleotides, preferably from about 14 to 30 nucleotides. The ability to derive an antisense or a sense oligonucleotide, based upon a cDNA sequence encoding a given protein is described in, for example, Stein and Cohen, Cancer Res. 48:2659, (1988) and van der Krol et al., BioTechniques 6:958, (1988). 
     Antisense molecules can be modified or unmodified RNA, DNA, or mixed polymer oligonucleotides. These molecules function by specifically binding to matching sequences resulting in inhibition of peptide synthesis (Wu-Pong, November 1994, BioPharm, 20-33) either by steric blocking or by activating an RNase H enzyme. Antisense molecules can also alter protein synthesis by interfering with RNA processing or transport from the nucleus into the cytoplasm (Mukhopadhyay &amp; Roth, 1996, Crit. Rev. in Oncogenesis 7, 151-190). In addition, binding of single stranded DNA to RNA can result in nuclease-mediated degradation of the heteroduplex (Wu-Pong, supra). Backbone modified DNA chemistry which have thus far been shown to act as substrates for RNase H are phosphorothioates, phosphorodithioates, borontrifluoridates, and 2′-arabino and 2′-fluoro arabino-containing oligonucleotides. 
     Antisense molecules may be introduced into a cell containing the target nucleotide sequence by formation of a conjugate with a ligand binding molecule, as described in WO 91/04753. Suitable ligand binding molecules include, but are not limited to, cell surface receptors, growth factors, other cytokines, or other ligands that bind to cell surface receptors. Preferably, conjugation of the ligand binding molecule does not substantially interfere with the ability of the ligand binding molecule to bind to its corresponding molecule or receptor, or block entry of the sense or antisense oligonucleotide or its conjugated version into the cell. Alternatively, a sense or an antisense oligonucleotide may be introduced into a cell containing the target nucleic acid sequence by formation of an oligonucleotide-lipid complex, as described in WO 90/10448. It is understood that the use of antisense molecules or knock out and knock in models may also be used in screening assays as discussed above, in addition to methods of treatment. 
     (b) RNA Interference 
     RNA interference refers to the process of sequence-specific post transcriptional gene silencing in animals mediated by short interfering RNAs (siRNA) (Fire et al., Nature, 391, 806 (1998)). The corresponding process in plants is referred to as post transcriptional gene silencing or RNA silencing and is also referred to as quelling in fungi. The presence of dsRNA in cells triggers the RNAi response though a mechanism that has yet to be fully characterized. This mechanism appears to be different from the interferon response that results from dsRNA mediated activation of protein kinase PKR and 2′,5′-oligoadenylate synthetase resulting in non-specific cleavage of mRNA by ribonuclease L. (reviewed in Sharp, P. A., RNA interference—2001, Genes &amp; Development 15:485-490 (2001)). 
     Small interfering RNAs (siRNAs) are powerful sequence-specific reagents designed to suppress the expression of genes in cultured mammalian cells through a process known as RNA interference (RNAi). Elbashir, S. M. et al.  Nature  411:494-498 (2001); Caplen, N. J. et al.  Proc. Natl. Acad. Sci. USA  98:9742-9747 (2001); Harborth, J. et al.  J. Cell Sci.  114:4557-4565 (2001). The term “short interfering RNA” or “siRNA” refers to a double stranded nucleic acid molecule capable of RNA interference “RNAi”, (see Kreutzer et al., WO 00/44895; Zernicka-Goetz et al. WO 01/36646; Fire, WO 99/32619; Mello and Fire, WO 01/29058). As used herein, siRNA molecules are limited to RNA molecules but further encompasses chemically modified nucleotides and non-nucleotides. siRNA gene-targeting experiments have been carried out by transient siRNA transfer into cells (achieved by such classic methods as liposome-mediated transfection, electroporation, or microinjection). 
     Molecules of siRNA are 21- to 23-nucleotide RNAs, with characteristic 2- to 3-nucleotide 3′-overhanging ends resembling the RNase III processing products of long double-stranded RNAs (dsRNAs) that normally initiate RNAi. When introduced into a cell, they assemble with yet-to-be-identified proteins of an endonuclease complex (RNA-induced silencing complex), which then guides target mRNA cleavage. As a consequence of degradation of the targeted mRNA, cells with a specific phenotype characteristic of suppression of the corresponding protein product are obtained. The small size of siRNAs, compared with traditional antisense molecules, prevents activation of the dsRNA-inducible interferon system present in mammalian cells. This avoids the nonspecific phenotypes normally produced by dsRNA larger than 30 base pairs in somatic cells. 
     Intracellular transcription of small RNA molecules is achieved by cloning the siRNA templates into RNA polymerase III (Pol III) transcription units, which normally encode the small nuclear RNA (snRNA) U6 or the human RNase P RNA H1. Two approaches have been developed for expressing siRNAs: in the first, sense and antisense strands constituting the siRNA duplex are transcribed by individual promoters (Lee, N. S. et al.  Nat. Biotechnol.  20, 500-505 (2002); Miyagishi, M. &amp; Taira, K.  Nat. Biotechnol.  20, 497-500 (2002).); in the second, siRNAs are expressed as fold-back stem-loop structures that give rise to siRNAs after intracellular processing (Paul, C. P. et al.  Nat. Biotechnol.  20:505-508 (2002)). The endogenous expression of siRNAs from introduced DNA templates is thought to overcome some limitations of exogenous siRNA delivery, in particular the transient loss of phenotype. U6 and H1 RNA promoters are members of the type III class of Pol III promoters. (Paule, M. R. &amp; White, R. J.  Nucleic Acids Res.  28, 1283-1298 (2000)). 
     Co-expression of sense and antisense siRNAs mediate silencing of target genes, whereas expression of sense or antisense siRNA alone do not greatly affect target gene expression. Transfection of plasmid DNA, rather than synthetic siRNAs, may appear advantageous, considering the danger of RNase contamination and the costs of chemically synthesized siRNAs or siRNA transcription kits. Stable expression of siRNAs allows new gene therapy applications, such as treatment of persistent viral infections. Considering the high specificity of siRNAs, the approach also allows the targeting of disease-derived transcripts with point mutations, such as RAS or TP53 oncogene transcripts, without alteration of the remaining wild-type allele. Finally, by high-throughput sequence analysis of the various genomes, the DNA-based methodology may also be a cost-effective alternative for automated genome-wide loss-of-function phenotypic analysis, especially when combined with miniaturized array-based phenotypic screens. (Ziauddin, J. &amp; Sabatini, D. M.  Nature  411:107-110 (2001)). 
     The presence of long dsRNAs in cells stimulates the activity of a ribonuclease III enzyme referred to as dicer. Dicer is involved in the processing of the dsRNA into short pieces of dsRNA known as short interfering RNAs (siRNA) (Berstein et al., 2001, Nature, 409:363 (2001)). Short interfering RNAs derived from dicer activity are typically about 21-23 nucleotides in length and comprise about 19 base pair duplexes. Dicer has also been implicated in the excision of 21 and 22 nucleotide small temporal RNAs (stRNA) from precursor RNA of conserved structure that are implicated in translational control (Hutvagner et al., Science, 293, 834 (2001)). The RNAi response also features an endonuclease complex containing a siRNA, commonly referred to as an RNA-induced silencing complex (RISC), which mediates cleavage of single stranded RNA having sequence homologous to the siRNA. Cleavage of the target RNA takes place in the middle of the region complementary to the guide sequence of the siRNA duplex (Elbashir et al., Genes Dev., 15, 188 (2001)). 
     This invention provides an expression system comprising an isolated nucleic acid molecule comprising a sequence capable of specifically hybridizing to the PRLR sequences. In an embodiment, the nucleic acid molecule is capable of inhibiting the expression of the PRLR protein. A method of inhibiting expression of PRLR gene expression inside a cell by a vector-directed expression of a short RNA which short RNA can fold in itself and create a double strand RNA having PRLR mRNA sequence identity and able to trigger posttranscriptional gene silencing, or RNA interference (RNAi), of the PRLR gene inside the cell. In another method a short double strand RNA having a PRLR mRNA sequence identity is delivered inside the cell to trigger posttranscriptional gene silencing, or RNAi, of the PRLR gene. In various embodiments, the nucleic acid molecule is at least a 7 mer, at least a 10 mer, or at least a 20 mer. In a further embodiment, the sequence is unique. 
     (c) Pharmaceutical Compositions 
     Pharmaceutical compositions encompassed by the present invention include as active agent, the polypeptides, polynucleotides, antisense oligonucleotides, or antibodies of the invention disclosed herein in a therapeutically effective amount. An “effective amount” is an amount sufficient to effect beneficial or desired results, including clinical results. An effective amount can be administered in one or more administrations. For purposes of this invention, an effective amount of an adenoviral vector is an amount that is sufficient to palliate, ameliorate, stabilize, reverse, slow or delay the progression of the disease state. 
     The compositions can be used to treat cancer as well as metastases of primary cancer. In addition, the pharmaceutical compositions can be used in conjunction with conventional methods of cancer treatment, e.g., to sensitize tumors to radiation or conventional chemotherapy. The terms “treatment”, “treating”, “treat” and the like are used herein to generally refer to obtaining a desired pharmacologic and/or physiologic effect. The effect may be prophylactic in terms of completely or partially preventing a disease or symptom thereof and/or may be therapeutic in terms of a partial or complete stabilization or cure for a disease and/or adverse effect attributable to the disease. “Treatment” as used herein covers any treatment of a disease in a mammal, particularly a human, and includes: (a) preventing the disease or symptom from occurring in a subject which may be predisposed to the disease or symptom but has not yet been diagnosed as having it; (b) inhibiting the disease symptom, i.e., arresting its development; or (c) relieving the disease symptom, i.e., causing regression of the disease or symptom. 
     Where the pharmaceutical composition comprises an antibody that specifically binds to a gene product encoded by a differentially expressed polynucleotide, the antibody can be coupled to a drug for delivery to a treatment site or coupled to a detectable label to facilitate imaging of a site comprising cancer cells, such as prostate cancer cells. Methods for coupling antibodies to drugs and detectable labels are well known in the art, as are methods for imaging using detectable labels. 
     A “patient” for the purposes of the present invention includes both humans and other animals, particularly mammals, and organisms. Thus the methods are applicable to both human therapy and veterinary applications. In one embodiment the patient is a mammal, and preferably the patient is human. One target patient population includes all patients currently undergoing treatment for cancer, particularly the specific cancer types mentioned herein. Subsets of these patient populations include those who have experienced a relapse of a previously treated cancer of this type in the previous six months and patients with disease progression in the past six months. 
     The term “therapeutically effective amount” as used herein refers to an amount of a therapeutic agent to treat, ameliorate, or prevent a desired disease or condition, or to exhibit a detectable therapeutic or preventative effect. The effect can be detected by, for example, chemical markers or antigen levels. Therapeutic effects also include reduction in physical symptoms, such as decreased body temperature. The precise effective amount for a subject will depend upon the subject&#39;s size and health, the nature and extent of the condition, and the therapeutics or combination of therapeutics selected for administration. The effective amount for a given situation is determined by routine experimentation and is within the judgment of the clinician. For purposes of the present invention, an effective dose will generally be from about 0.01 mg/kg to about 5 mg/kg, or about 0.01 mg/kg to about 50 mg/kg or about 0.05 mg/kg to about 10 mg/kg of the compositions of the present invention in the individual to which it is administered. 
     A pharmaceutical composition can also contain a pharmaceutically acceptable carrier. The term “pharmaceutically acceptable carrier” refers to a carrier for administration of a therapeutic agent, such as antibodies or a polypeptide, genes, and other therapeutic agents. The term refers to any pharmaceutical carrier that does not itself induce the production of antibodies harmful to the individual receiving the composition, and which can be administered without undue toxicity. Suitable carriers can be large, slowly metabolized macromolecules such as proteins, polysaccharides, polylactic acids, polyglycolic acids, polymeric amino acids, amino acid copolymers, and inactive virus particles. Such carriers are well known to those of ordinary skill in the art. Pharmaceutically acceptable carriers in therapeutic compositions can include liquids such as water, saline, glycerol and ethanol. Auxiliary substances, such as wetting or emulsifying agents, pH buffering substances, and the like, can also be present in such vehicles. Typically, the therapeutic compositions are prepared as injectables, either as liquid solutions or suspensions; solid forms suitable for solution in, or suspension in, liquid vehicles prior to injection can also be prepared. Liposomes are included within the definition of a pharmaceutically acceptable carrier. Pharmaceutically acceptable salts can also be present in the pharmaceutical composition, e.g., mineral acid salts such as hydrochlorides, hydrobromides, phosphates, sulfates, and the like; and the salts of organic acids such as acetates, propionates, malonates, benzoates, and the like. A thorough discussion of pharmaceutically acceptable excipients is available in  Remington: The Science and Practice of Pharmacy  (1995) Alfonso Gennaro, Lippincott, Williams, &amp; Wilkins. 
     The pharmaceutical compositions can be prepared in various forms, such as granules, tablets, pills, suppositories, capsules, suspensions, salves, lotions and the like. Pharmaceutical grade organic or inorganic carriers and/or diluents suitable for oral and topical use can be used to make up compositions containing the therapeutically-active compounds. Diluents known to the art include aqueous media, vegetable and animal oils and fats. Stabilizing agents, wetting and emulsifying agents, salts for varying the osmotic pressure or buffers for securing an adequate pH value, and skin penetration enhancers can be used as auxiliary agents. 
     The pharmaceutical compositions of the present invention comprise a PRLR protein in a form suitable for administration to a patient. In one embodiment, the pharmaceutical compositions are in a water soluble form, such as being present as pharmaceutically acceptable salts, which is meant to include both acid and base addition salts. “Pharmaceutically acceptable acid addition salt” refers to those salts that retain the biological effectiveness of the free bases and that are not biologically or otherwise undesirable, formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and the like. “Pharmaceutically acceptable base addition salts” include those derived from inorganic bases such as sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Particularly preferred are the ammonium, potassium, sodium, calcium, and magnesium salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, and ethanolamine. 
     The pharmaceutical compositions may also include one or more of the following: carrier proteins such as serum albumin; buffers; fillers such as microcrystalline cellulose, lactose, corn and other starches; binding agents; sweeteners and other flavoring agents; coloring agents; and polyethylene glycol. Additives are well known in the art, and are used in a variety of formulations. 
     The compounds having the desired pharmacological activity may be administered in a physiologically acceptable carrier to a host, as previously described. The pharmaceutical compositions may be administered in a variety of routes including, but not limited to, intravenous, intramuscular, intra-arterial, intramedullary, intrathecal, intraventricular, transdermal or transcutaneous applications (for example, see WO98/20734), subcutaneous, intraperitoneal, intranasal, enteral, topical, sublingual, intravaginal or rectal means. Depending upon the manner of introduction, the compounds may be formulated in a variety of ways. The concentration of therapeutically active compound in the formulation may vary from about 0.1-100% wgt/vol. Once formulated, the compositions contemplated by the invention can be (1) administered directly to the subject (e.g., as polynucleotide, polypeptides, small molecule agonists or antagonists, and the like); or (2) delivered ex vivo, to cells derived from the subject (e.g., as in ex vivo gene therapy). Direct delivery of the compositions will generally be accomplished by parenteral injection, e.g., subcutaneously, intraperitoneally, intravenously or intramuscularly, intratumoral or to the interstitial space of a tissue. Other modes of administration include oral and pulmonary administration, suppositories, and transdermal applications, needles, and gene guns (see the worldwideweb site at powderject.com) or hyposprays. Dosage treatment can be a single dose schedule or a multiple dose schedule. 
     Methods for the ex vivo delivery and reimplantation of transformed cells into a subject are known in the art and described in e.g., WO 93/14778. Examples of cells useful in ex vivo applications include, for example, stem cells, particularly hematopoetic, lymph cells, macrophages, dendritic cells, or tumor cells. Generally, delivery of nucleic acids for both ex vivo and in vitro applications can be accomplished by, for example, dextran-mediated transfection, calcium phosphate precipitation, polybrene mediated transfection, protoplast fusion, electroporation, encapsulation of the polynucleotide(s) in liposomes, and direct microinjection of the DNA into nuclei, all well known in the art. 
     Once differential expression of a gene corresponding to a PRLR polynucleotide described herein has been found to correlate with a proliferative disorder, such as neoplasia, dysplasia, and hyperplasia, the disorder can be amenable to treatment by administration of a therapeutic agent based on the provided polynucleotide, corresponding polypeptide or other corresponding molecule (e.g., antisense, ribozyme, etc.). In other embodiments, the disorder can be amenable to treatment by administration of a small molecule drug that, for example, serves as an inhibitor (antagonist) of the function of the encoded gene product of a gene having increased expression in cancerous cells relative to normal cells or as an agonist for gene products that are decreased in expression in cancerous cells (e.g., to promote the activity of gene products that act as tumor suppressors). 
     The dose and the means of administration of the inventive pharmaceutical compositions are determined based on the specific qualities of the therapeutic composition, the condition, age, and weight of the patient, the progression of the disease, and other relevant factors. For example, administration of polynucleotide therapeutic compositions agents includes local or systemic administration, including injection, oral administration, particle gun or catheterized administration, and topical administration. Preferably, the therapeutic polynucleotide composition contains an expression construct comprising a promoter operably linked to a polynucleotide of at least 12, 22, 25, 30, or 35 contiguous nt of the polynucleotide disclosed herein. Various methods can be used to administer the therapeutic composition directly to a specific site in the body. For example, a small metastatic lesion is located and the therapeutic composition injected several times in several different locations within the body of tumor. Alternatively, arteries that serve a tumor are identified, and the therapeutic composition injected into such an artery, in order to deliver the composition directly into the tumor. A tumor that has a necrotic center is aspirated and the composition injected directly into the now empty center of the tumor. An antisense composition is directly administered to the surface of the tumor, for example, by topical application of the composition. X-ray imaging is used to assist in certain of the above delivery methods. 
     Targeted delivery of therapeutic compositions containing an antisense polynucleotide, subgenomic polynucleotides, or antibodies to specific tissues can also be used. Receptor-mediated DNA delivery techniques are described in, for example, Findeis et al.,  Trends Biotechnol . (1993) 11:202; Chiou et al.,  Gene Therapeutics: Methods And Applications Of Direct Gene Transfer  (J. A. Wolff, ed.) (1994); Wu et al.,  J. Biol. Chem . (1988) 263:621; Wu et al.,  J. Biol. Chem . (1994) 269:542; Zenke et al.,  Proc. Natl. Acad. Sci . ( USA ) (1990) 87:3655; Wu et al.,  J Biol. Chem . (1991) 266:338. Therapeutic compositions containing a polynucleotide are administered in a range of about 100 ng to about 200 mg of DNA for local administration in a gene therapy protocol. Concentration ranges of about 500 ng to about 50 mg, about 1 μg to about 2 mg, about 5 μg to about 500 μg, and about 20 μg to about 100 μg of DNA can also be used during a gene therapy protocol. Factors such as method of action (e.g., for enhancing or inhibiting levels of the encoded gene product) and efficacy of transformation and expression are considerations that will affect the dosage required for ultimate efficacy of the antisense subgenomic polynucleotides. Where greater expression is desired over a larger area of tissue, larger amounts of antisense subgenomic polynucleotides or the same amounts re-administered in a successive protocol of administrations, or several administrations to different adjacent or close tissue portions of, for example, a tumor site, may be required to effect a positive therapeutic outcome. In all cases, routine experimentation in clinical trials will determine specific ranges for optimal therapeutic effect. 
     The therapeutic polynucleotides and polypeptides of the present invention can be delivered using gene delivery vehicles. The gene delivery vehicle can be of viral or non-viral origin (see generally, Jolly,  Cancer Gene Therapy  (1994) 1:51; Kimura,  Human Gene Therapy  (1994) 5:845; Connelly,  Human Gene Therapy  (1995) 1:185; and Kaplitt,  Nature Genetics  (1994) 6:148). Expression of such coding sequences can be induced using endogenous mammalian or heterologous promoters. Expression of the coding sequence can be either constitutive or regulated. 
     Viral-based vectors for delivery of a desired polynucleotide and expression in a desired cell ate well known in the art. Exemplary viral-based vehicles include, but are not limited to, recombinant retroviruses (see, e.g., WO 90/07936; WO 94/03622; WO 93/25698; WO 93/25234; U.S. Pat. No. 5,219,740; WO 93/11230; WO 93/10218; U.S. Pat. No. 4,777,127; GB Patent No. 2,200,651; EP 0 345 242; and WO 91/02805), alphavirus-based vectors (e.g., Sindbis virus vectors, Semliki forest virus (ATCC VR-67; ATCC VR-1247), Ross River virus (ATCC VR-373; ATCC VR-1246) and Venezuelan equine encephalitis virus (ATCC VR-923; ATCC VR-1250; ATCC VR 1249; ATCC VR-532)), and adeno-associated virus (AAV) vectors (see, e.g., WO 94/12649, WO 93/03769; WO 93/19191; WO 94/28938; WO 95/11984 and WO 95/00655). Administration of DNA linked to killed adenovirus as described in Curiel,  Hum. Gene Ther . (1992) 3:147 can also be employed. 
     Non-viral delivery vehicles and methods can also be employed, including, but not limited to, polycationic condensed DNA linked or unlinked to killed adenovirus alone (see, e.g., Curiel,  Hum. Gene Ther . (1992) 3:147); ligand-linked DNA (see, e.g., Wu,  J. Biol. Chem . (1989) 264:16985); eukaryotic cell delivery vehicles cells (see, e.g., U.S. Pat. No. 5,814,482; WO 95/07994; WO 96/17072; WO 95/30763; and WO 97/42338) and nucleic charge neutralization or fusion with cell membranes. Naked DNA can also be employed. Exemplary naked DNA introduction methods are described in WO 90/11092 and U.S. Pat. No. 5,580,859. Liposomes that can act as gene delivery vehicles are described in U.S. Pat. No. 5,422,120; WO 95/13796; WO 94/23697; WO 91/14445; and EP 0524968. Additional approaches are described in Philip,  Mol. Cell Biol . (1994) 14:2411, and in Woffendin,  Proc. Natl. Acad. Sci . (1994) 91:1581. 
     Further non-viral delivery suitable for use includes mechanical delivery systems such as the approach described in Woffendin et al.,  Proc. Natl. Acad. Sci. USA  (1994) 91(24):11581. Moreover, the coding sequence and the product of expression of such can be delivered through deposition of photopolymerized hydrogel materials or use of ionizing radiation (see, e.g., U.S. Pat. No. 5,206,152 and WO 92/11033). Other conventional methods for gene delivery that can be used for delivery of the coding sequence include, for example, use of hand-held gene transfer particle gun (see, e.g., U.S. Pat. No. 5,149,655); use of ionizing radiation for activating transferred gene (see, e.g., U.S. Pat. No. 5,206,152 and WO 92/11033). 
     In one embodiment, PRLR proteins and modulators are administered as therapeutic agents, and can be formulated as outlined above. Similarly, the PRLR gene (including both the full-length sequence, partial sequences, or regulatory sequences of the PRLR coding regions) can be administered in gene therapy applications, as is known in the art. The PRLR gene can include antisense applications, either as gene therapy (i.e. for incorporation into the genome) or as antisense compositions, as will be appreciated by those in the art. 
     Thus, in one embodiment, methods of modulating PRLR gene activity in cells or organisms are provided. In one embodiment, the methods comprise administering to a cell an anti-PRLR antibody that reduces or eliminates the biological activity of an endogenous PRLR protein. Alternatively, the methods comprise administering to a cell or organism a recombinant nucleic acid encoding a PRLR protein. As will be appreciated by those in the art, this may be accomplished in any number of ways. In one embodiment, for example when the PRLR sequence is down-regulated in cancer, the activity of the PRLR expression product is increased by increasing the amount of PRLR expression in the cell, for example by overexpressing the endogenous PRLR gene or by administering a gene encoding the PRLR sequence, using known gene-therapy techniques. In one embodiment, the gene therapy techniques include the incorporation of the exogenous gene using enhanced homologous recombination (EHR), for example as described in PCT/US93/03868, hereby incorporated by reference in its entirety. Alternatively, for example when the PRLR sequence is up-regulated in cancer, the activity of the PRLR gene is decreased, for example by the administration of a PRLR antisense nucleic acid. 
     (d) Vaccines 
     In one embodiment, the PRLR gene is administered as a DNA vaccine, either alone or in combinations with other genes. Naked DNA vaccines are generally known in the art. Brower, Nature Biotechnology, 16:1304-1305 (1998). 
     In one embodiment, the PRLR gene of the present invention is used in a DNA vaccine. Methods for the use of genes as DNA vaccines are well known to one of ordinary skill in the art, and include placing a PRLR gene or portion of a PRLR gene under the control of a promoter for expression in a patient with cancer. The PRLR gene used for DNA vaccines can encode full-length PRLR proteins, but more preferably encodes portions of the PRLR proteins including peptides derived from PRLR. In one embodiment a patient is immunized with a DNA vaccine comprising a plurality of nucleotide sequences derived from a PRLR gene. Similarly, it is possible to immunize a patient with a plurality of nucleotide sequences derived from the PRLR gene. Without being bound by theory, expression of the polypeptide encoded by the DNA vaccine, cytotoxic T-cells, helper T-cells and antibodies are induced that recognize and destroy or eliminate cells expressing PRLR proteins. 
     In one embodiment, the DNA vaccines include a gene encoding an adjuvant molecule with the DNA vaccine. Such adjuvant molecules include cytokines that increase the immunogenic response to the PRLR polypeptide encoded by the DNA vaccine. Additional or alternative adjuvants are known to those of ordinary skill in the art and find use in the invention. 
     (e) Antibodies 
     The PRLR antibodies described above find use in a number of applications. For example, the PRLR antibodies may be coupled to standard affinity chromatography columns and used to purify PRLR proteins. The antibodies may also be used therapeutically as blocking polypeptides, as outlined above, since they will specifically bind to the PRLR protein. 
     The present invention further provides methods for detecting the presence of and/or measuring a level of a polypeptide in a biological sample, which PRLR polypeptide is encoded by a PRLR polynucleotide that is differentially expressed in a cancer cell, using an antibody specific for the encoded polypeptide. The methods generally comprise: a) contacting the sample with an antibody specific for a polypeptide encoded by a PRLR polynucleotide that is differentially expressed in a cancer cell; and b) detecting binding between the antibody and molecules of the sample. 
     Detection of specific binding of the antibody specific for the encoded PRLR polypeptide, when compared to a suitable control is an indication that encoded polypeptide is present in the sample. Suitable controls include a sample known not to contain the encoded PRLR polypeptide or known not to contain elevated levels of the polypeptide; such as normal tissue, and a sample contacted with an antibody not specific for the encoded polypeptide, e.g., an anti-idiotype antibody. A variety of methods to detect specific antibody-antigen interactions are known in the art and can be used in the method, including, but not limited to, standard immunohistological methods, immunoprecipitation, an enzyme immunoassay, and a radioimmunoassay. In general, the specific antibody will be detectably labeled, either directly or indirectly. Direct labels include radioisotopes; enzymes whose products are detectable (e.g., luciferase, β-galactosidase, and the like); fluorescent labels (e.g., fluorescein isothiocyanate, rhodamine, phycoerythrin, and the like); fluorescence emitting metals, e.g.,  152 Eu, or others of the lanthanide series, attached to the antibody through metal chelating groups such as EDTA; chemiluminescent compounds, e.g., luminol, isoluminol, acridinium salts, and the like; bioluminescent compounds, e.g., luciferin, aequorin (green fluorescent protein), and the like. The antibody may be attached (coupled) to an insoluble support, such as a polystyrene plate or a bead. Indirect labels include second antibodies specific for antibodies specific for the encoded polypeptide (“first specific antibody”), wherein the second antibody is labeled as described above; and members of specific binding pairs, e.g., biotin-avidin, and the like. The biological sample may be brought into contact with and immobilized on a solid support or carrier, such as nitrocellulose, that is capable of immobilizing cells, cell particles, or soluble proteins. The support may then be washed with suitable buffers, followed by contacting with a detectably-labeled first specific antibody. Detection methods are known in the art and will be chosen as appropriate to the signal emitted by the detectable label. Detection is generally accomplished in comparison to suitable controls, and to appropriate standards. 
     In some embodiments, the methods are adapted for use in vivo, e.g., to locate or identify sites where cancer cells are present. In these embodiments, a detectably-labeled moiety, e.g., an antibody, which is specific for a PRLR polypeptide is administered to an individual (e.g., by injection), and labeled cells are located using standard imaging techniques, including, but not limited to, magnetic resonance imaging, computed tomography scanning, and the like. In this manner, cancer cells are differentially labeled. 
     (f) Other Methods for the Detection and Diagnosis of Cancers 
     Without being bound by theory, it appears that the PRLR gene is important in cancers. Accordingly, disorders based on mutant or variant PRLR gene may be determined. In one embodiment, the invention provides methods for identifying cells containing variants of the PRLR gene comprising determining all or part of the sequence of at least one endogenous PRLR gene in a cell. As will be appreciated by those in the art, this may be done using any number of sequencing techniques. In an embodiment, the invention provides methods of identifying the PRLR genotype of an individual comprising determining all or part of the sequence of at least one PRLR gene of the individual. This is generally done in at least one tissue of the individual, and may include the evaluation of a number of tissues or different samples of the same tissue. The method may include comparing the sequence of the sequenced PRLR gene to a known PRLR gene, i.e., a wild-type gene. As will be appreciated by those in the art, alterations in the sequence of the PRLR gene can be an indication of either the presence of the disease, or propensity to develop the disease, or prognosis evaluations. 
     The sequence of all or part of the PRLR gene can then be compared to the sequence of a known PRLR gene to determine if any differences exist. This can be done using any number of known homology programs, such as Bestfit, etc. In one embodiment, the presence of a difference in the sequence between the PRLR gene of the patient and the known PRLR gene is indicative of a disease state or a propensity for a disease state, as outlined herein. 
     In one embodiment, the PRLR gene is used as a probe to determine the number of copies of the PRLR gene in the genome. For example, some cancers exhibit chromosomal deletions or insertions, resulting in an alteration in the copy number of a gene. 
     In another embodiment the PRLR gene is used as a probe to determine the chromosomal location of the PRLR gene. Information such as chromosomal location finds use in providing a diagnosis or prognosis in particular when chromosomal abnormalities such as translocations, and the like are identified in PRLR gene loci. 
     The present invention provides methods of using the polynucleotides described herein for detecting cancer cells, facilitating diagnosis of cancer and the severity of a cancer (e.g., tumor grade, tumor burden, and the like) in a subject, facilitating a determination of the prognosis of a subject, and assessing the responsiveness of the subject to therapy (e.g., by providing a measure of therapeutic effect through, for example, assessing tumor burden during or following a chemotherapeutic regimen). Detection can be based on detection of a polynucleotide that is differentially expressed in a cancer cell, and/or detection of a polypeptide encoded by a polynucleotide that is differentially expressed in a cancer cell. The detection methods of the invention can be conducted in vitro or in vivo, on isolated cells, or in whole tissues or a bodily fluid e.g., blood, plasma, serum, urine, and the like). 
     In some embodiments, methods are provided for detecting a cancer cell by detecting expression in the cell of a transcript that is differentially expressed in a cancer cell. Any of a variety of known methods can be used for detection, including, but not limited to, detection of a transcript by hybridization with a polynucleotide that hybridizes to a polynucleotide that is differentially expressed in a prostate cancer cell; detection of a transcript by a polymerase chain reaction using specific oligonucleotide primers; in situ hybridization of a cell using as a probe a polynucleotide that hybridizes to a gene that is differentially expressed in a prostate cancer cell. The methods can be used to detect and/or measure mRNA levels of a gene that is differentially expressed in a cancer cell. In some embodiments, the methods comprise: a) contacting a sample with a polynucleotide that corresponds to a differentially expressed gene described herein under conditions that allow hybridization; and b) detecting hybridization, if any. 
     Detection of differential hybridization, when compared to a suitable control, is an indication of the presence in the sample of a polynucleotide that is differentially expressed in a cancer cell. Appropriate controls include, for example, a sample that is known not to contain a polynucleotide that is differentially expressed in a cancer cell, and use of a labeled polynucleotide of the same “sense” as the polynucleotide that is differentially expressed in the cancer cell. Conditions that allow hybridization are known in the art, and have been described in more detail above. Detection can also be accomplished by any known method, including, but not limited to, in situ hybridization, PCR (polymerase chain reaction), RT-PCR (reverse transcription-PCR), TMA, bDNA, and Nasbau and “Northern” or RNA blotting, or combinations of such techniques, using a suitably labeled polynucleotide. A variety of labels and labeling methods for polynucleotides are known in the art and can be used in the assay methods of the invention. Specificity of hybridization can be determined by comparison to appropriate controls. 
     Polynucleotides generally comprising at least 10 nt, at least 12 nt or at least 15 contiguous nucleotides of a polynucleotide provided herein, are used for a variety of purposes, such as probes for detection of and/or measurement of, transcription levels of a polynucleotide that is differentially expressed in a prostate cancer cell. As will be readily appreciated by the ordinarily skilled artisan, the probe can be detectably labeled and contacted with, for example, an array comprising immobilized polynucleotides obtained from a test sample (e.g. mRNA). Alternatively, the probe can be immobilized on an array and the test sample detectably labeled. These and other variations of the methods of the invention are well within the skill in the art and are within the scope of the invention. 
     Nucleotide probes are used to detect expression of a gene corresponding to the provided polynucleotide. In Northern blots, mRNA is separated electrophoretically and contacted with a probe. A probe is detected as hybridizing to an mRNA species of a particular size. The amount of hybridization can be quantitated to determine relative amounts of expression, for example under a particular condition. Probes are used for in situ hybridization to cells to detect expression. Probes can also be used in vivo for diagnostic detection of hybridizing sequences. Probes are typically labeled with a radioactive isotope. Other types of detectable labels can be used such as chromophores, fluorophores, and enzymes. Other examples of nucleotide hybridization assays are described in WO92/02526 and U.S. Pat. No. 5,124,246. 
     PCR is another means for detecting small amounts of target nucleic acids (see, e.g., Mullis et al.,  Meth. Enzymol . (1987) 155:335; U.S. Pat. No. 4,683,195; and U.S. Pat. No. 4,683,202). Two primer oligonucleotides that hybridize with the target nucleic acids are used to prime the reaction. The primers can be composed of sequence within or 3′ and 5′ to the PRLR polynucleotides disclosed herein. Alternatively, if the primers are 3′ and 5′ to these polynucleotides, they need not hybridize to them or the complements. After amplification of the target with a thermostable polymerase, the amplified target nucleic acids can be detected by methods known in the art, e.g., Southern blot. mRNA or cDNA can also be detected by traditional blotting techniques (e.g., Southern blot, Northern blot, etc.) described in Sambrook et al., “Molecular Cloning: A Laboratory Manual” (New York, Cold Spring Harbor Laboratory, 1989) (e.g., without PCR amplification). In general, mRNA or cDNA generated from mRNA using a polymerase enzyme can be purified and separated using gel electrophoresis, and transferred to a solid support, such as nitrocellulose. The solid support is exposed to a labeled probe, washed to remove any unhybridized probe, and duplexes containing the labeled probe are detected. 
     Methods using PCR amplification can be performed on the DNA from a single cell, although it is convenient to use at least about 10 5  cells. The use of the polymerase chain reaction is described in Saiki et al. (1985)  Science  239:487, and a review of current techniques may be found in Sambrook, et al. Molecular Cloning: A Laboratory Manual, CSH Press 1989, pp. 14.2-14.33. A detectable label may be included in the amplification reaction. Suitable detectable labels include fluorochromes, (e.g. fluorescein isothiocyanate (FITC), rhodamine, Texas Red, phycoerythrin, allophycocyanin, 6-carboxyfluorescein (6-FAM), 2′,7′-dimethoxy-4′,5′-dichloro-6-carboxyfluorescein, 6-carboxy-X-rhodamine (ROX), 6-carboxy-2′,4′,7′,4,7-hexachlorofluorescein (HEX), 5-carboxyfluorescein (5-FAM) or N,N,N′,N′-tetramethyl-6-carboxyrhodamine (TAMRA)), radioactive labels, (e.g.  32 P,  35 S,  3 H, etc.), and the like. The label may be a two stage system, where the polynucleotides is conjugated to biotin, haptens, etc. having a high affinity binding partner, e.g. avidin, specific antibodies, etc., where the binding partner is conjugated to a detectable label. The label may be conjugated to one or both of the primers. Alternatively, the pool of nucleotides used in the amplification is labeled, so as to incorporate the label into the amplification product. 
     The reagents used in detection methods can be provided as part of a kit. Thus, the invention further provides kits for detecting the presence and/or a level of a polynucleotide that is differentially expressed in a cancer cell (e.g., by detection of an mRNA encoded by the differentially expressed gene of interest), and/or a polypeptide encoded thereby, in a biological sample. Procedures using these kits can be performed by clinical laboratories, experimental laboratories, medical practitioners, or private individuals. The kits of the invention for detecting a polypeptide encoded by a polynucleotide that is differentially expressed in a cancer cell may comprise a moiety that specifically binds the polypeptide, which may be an antibody that binds the polypeptide or fragment thereof. The kits of the invention used for detecting a polynucleotide that is differentially expressed in a prostate cancer cell may comprise a moiety that specifically hybridizes to such a polynucleotide. The kit may optionally provide additional components that are useful in the procedure, including, but not limited to, buffers, developing reagents, labels, reacting surfaces, means for detection, control samples, standards, instructions, and interpretive information. 
     The present invention further relates to methods of detecting/diagnosing a neoplastic or preneoplastic condition in a mammal (for example, a human). “Diagnosis” as used herein generally includes determination of a subject&#39;s susceptibility to a disease or disorder, determination as to whether a subject is presently affected by a disease or disorder, prognosis of a subject affected by a disease or disorder (e.g., identification of pre-metastatic or metastatic cancerous states, stages of cancer, or responsiveness of cancer to therapy), and therametrics (e.g., monitoring a subject&#39;s condition to provide information as to the effect or efficacy of therapy). 
     An “effective amount” is an amount sufficient to effect beneficial or desired results, including clinical results. An effective amount can be administered in one or more administrations. 
     A “cell sample” encompasses a variety of sample types obtained from an individual and can be used in a diagnostic or monitoring assay. The definition encompasses blood and other liquid samples of biological origin, solid tissue samples such as a biopsy specimen or tissue cultures or cells derived therefrom, and the progeny thereof. The definition also includes samples that have been manipulated in any way after their procurement, such as by treatment with reagents, solubilization, or enrichment for certain components, such as proteins or polynucleotides. The term “cell sample” encompasses a clinical sample, and also includes cells in culture, cell supernatants, cell lysates, serum, plasma, biological fluid, and tissue samples. 
     As used herein, the terms “neoplastic cells”, “neoplasia”, “tumor”, “tumor cells”, “cancer” and “cancer cells”, (used interchangeably) refer to cells which exhibit relatively autonomous growth, so that they exhibit an aberrant growth phenotype characterized by a significant loss of control of cell proliferation (i.e., de-regulated cell division). Neoplastic cells can be malignant or benign. 
     The terms “individual,” “subject,” “host,” and “patient,” are used interchangeably herein and refer to any mammalian subject for whom diagnosis, treatment, or therapy is desired, particularly humans. Other subjects may include cattle, dogs, cats, guinea pigs, rabbits, rats, mice, horses, and so on. Examples of conditions that can be detected/diagnosed in accordance with these methods include cancers. Polynucleotides corresponding to genes that exhibit the appropriate expression pattern can be used to detect cancer in a subject. For a review of markers of cancer, see, e.g., Hanahan et al. Cell 100:57-70 (2000). 
     Some detection/diagnostic methods comprise: (a) obtaining from a mammal (e.g., a human) a biological sample, (b) detecting the presence in the sample of a PRLR protein and (c) comparing the amount of product present with that in a control sample. In accordance with these methods, the presence in the sample of elevated levels of a PRLR gene product indicates that the subject has a neoplastic or preneoplastic condition. 
     Biological samples suitable for use in this method include biological fluids such as serum, plasma, pleural effusions, urine and cerebro-spinal fluid, CSF, tissue samples (e.g., mammary tumor or prostate tissue slices) can also be used in the method of the invention, including samples derived from biopsies. Cell cultures or cell extracts derived, for example, from tissue biopsies can also be used. 
     The compound is preferably a binding protein, e.g., an antibody, polyclonal or monoclonal, or antigen binding fragment thereof, which can be labeled with a detectable marker (e.g., fluorophore, chromophore or isotope, etc). Where appropriate, the compound can be attached to a solid support such as a bead, plate, filter, resin, etc. Determination of formation of the complex can be effected by contacting the complex with a further compound (e.g., an antibody) that specifically binds to the first compound (or complex). Like the first compound, the further compound can be attached to a solid support and/or can be labeled with a detectable marker. 
     The identification of elevated levels of PRLR protein in accordance with the present invention makes possible the identification of subjects (patients) that are likely to benefit from adjuvant therapy. For example, a biological sample from a post primary therapy subject (e.g., subject having undergone surgery) can be screened for the presence of circulating PRLR protein, the presence of elevated levels of the protein, determined by studies of normal populations, being indicative of residual tumor tissue. Similarly, tissue from the cut site of a surgically removed tumor can be examined (e.g., by immunofluorescence), the presence of elevated levels of product (relative to the surrounding tissue) being indicative of incomplete removal of the tumor. The ability to identify such subjects makes it possible to tailor therapy to the needs of the particular subject. Subjects undergoing non-surgical therapy, e.g., chemotherapy or radiation therapy, can also be monitored, the presence in samples from such subjects of elevated levels of PRLR protein being indicative of the need for continued treatment. Staging of the disease (for example, for purposes of optimizing treatment regimens) can also be effected, for example, by biopsy e.g. with antibody specific for a PRLR protein. 
     (g) Animal Models and Transgenics 
     The genes also find use in generating animal models of cancers. As is appreciated by one of ordinary skill in the art, when the PRLR gene identified is repressed or diminished in cancer tissue, gene therapy technology wherein antisense RNA directed to the PRLR gene will also diminish or repress expression of the gene. An animal generated as such serves as an animal model of PRLR-associated cancer that finds use in screening bioactive drug candidates. Similarly, gene knockout technology, for example as a result of homologous recombination with an appropriate gene targeting vector, will result in the absence of the PRLR protein. When desired, tissue-specific expression or knockout of the PRLR protein may be necessary. It is also possible that the PRLR protein is overexpressed in cancer, particularly breast, prostate, lung and skin cancer. As such, transgenic animals can be generated that overexpress the PRLR protein. Depending on the desired expression level, promoters of various strengths can be employed to express the transgene. Also, the number of copies of the integrated transgene can be determined and compared for a determination of the expression level of the transgene. Animals generated by such methods find use as animal models of PRLR-associated cancer and are additionally useful in screening for bioactive molecules to treat cancer. 
     EXAMPLES 
     The following examples are described so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all and only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Celsius, and pressure is at or near atmospheric. 
     Example 1 
     Insertion Site Analysis Following Tumor Induction in Mice 
     Tumors were induced in mice using either mouse mammary tumor virus (MMTV) or murine leukemia virus (MLV). MMTV causes mammary adenocarcinomas and MLV causes a variety of different hematopoetic malignancies (primarily T- or B-cell lymphomas). 
     Three routes of infection were used: (1) injection of neonates with purified virus preparations,
     (2) infection by milk-borne virus during nursing, and (3) genetic transmission of pathogenic proviruses via the germ-line (Akvr1 and/or Mtv2). The type of malignancy present in each affected mouse was determined by histological analysis of H&amp;E-stained thin sections of formalin-fixed, paraffin-embedded biopsy samples. Host DNA sequences flanking all clonally-integrated proviruses in each tumor were recovered by nested anchored-PCR using two virus-specific primers and two primers specific for a 40 bp double stranded DNA anchor ligated to restriction enzyme digested tumor DNA. Amplified bands representing host/virus junction fragments were cloned and sequenced. Then the host sequences (called “tags”) were used to BLAST analyze the mouse genomic sequence.   

     Extracted mouse genomic tag sequences were then mapped to the draft mouse genome assembly (NCBI m33 release) downloaded from www.ensembl.org. Tag sequences 45 bp or longer were mapped to the genome using Timelogic&#39;s accelerated blast algorithm, terablast, with the following parameter setup: −t=10 −X=1e−10 −v=20 −b=20 −R. Short tag sequences (&lt;45 bp) were mapped to the genome by NCBI blastall algorithm, with the following parameter setup: −e 1000 −F F−W 9 −v 20 −b 20. The combined blast results were then filtered for the best matches for each tag sequence, which typically requires a minimum of 95% identity over at least 30% of the tag sequence length. Tags with uniq chromosome locations were passed on to the gene call process. 
     For each individual tag, three parameters were recorded: (1) the mouse chromosome assignment, (2) base pair coordinates at which the integration occurred, and (3) provirus orientation. Using this information, all available tags from all analyzed tumors were mapped to the mouse genome. To identify the protooncogene targets of provirus insertion mutation, the provirus integration pattern at each cluster of integrants was analyzed relative to the locations of all known genes in the transcriptome. The presence of provirus at the same locus in two or more independent tumors is prima facie evidence that a protooncogene is present at or very near the proviral integration sites. This is because the genome is too large for random integrations to result in observable clustering. Any clustering that was detected provides unequivocal evidence for biological selection during tumorigenesis. In order to identify the human orthologs of the protooncogene targets of provirus insertion mutation, a comparative analysis of syntenic regions of the mouse and human genomes was performed. 
     Ensemb1 mouse gene models and UCSC refseq and knowngene sets were used to represent the mouse transcriptome. As noted above, based on the tag chromosome positions and the proviral insertion orientation relative to the adjacent genes, each tag was assigned to its nearest neighboring gene. Proviral insertions linked to a gene were grouped in 2 categories, type I insertions or type II insertions. If the insertion was within the gene locus, either intron or exon, it was designated as a type II insertion. If not, the insertion was designated as a type I insertion provided the insertion fulfilled these additional criteria: 1) it was outside the gene locus but within 100 kilobases from the gene&#39;s start or end positions, 2) for upstream insertions, the proviral orientation was the opposite to that of the gene, and 3) for downstream insertion, the proviral orientation was the same as the gene. Genes or transcripts discovered in this process were assigned with locus IDs from NCBI Locus Link annotations. The uniq mouse locus IDs with at least 2 viral inserts make up the current Oncogenome™. 
     To assign human orthologs for the mouse genes in the Oncogenome™, the MGI&#39;s mouse to human ortholog annotation and NCBI&#39;s homologene annotation was used. When there were conflicts or lack of ortholog annotation, comparative analysis of syntenic regions of the mouse and human genomes was performed, using the UCSC or Ensemb1 genome browser. The orthologous human genes were assigned with Locus Id&#39;s from NCBI Locus Link, and these human genes were further evaluated as potential targets for cancer therapeutics as described herein. 
     An example of PCR amplification of host/virus junction fragments is presented in  FIG. 1 . Lane 1 contains the amplification products from normal control DNA and lane 2 contains the amplification products from tumor DNA. The bands result from 5′ host/virus junction fragments present in the DNA samples. Lane 1 has bands from the env/3′ LTR junctions from all proviruses (upper) and the host/5′ LTR from the pathogenic endogenous Mtv2 provirus present in this particular mouse strain. This endogenous provirus is detected because its sequence is identical to the new clonally integrated proviruses in the tumor. All four new clonally integrated proviruses known to be in this tumor are readily detected. 
     Example 2 
     Analysis of Quantitative RT-PCR: Comparative C T  Method 
     The RT-PCR analysis was divided into 4 major steps: 1) RNA purification from primary normal and tumor tissues; 2) Generation of first strand cDNA from the purified tissue RNA for Real Time Quantitative PCR; 3) Setup RT-PCR for gene expression using ABI PRISM 7900HT Sequence Detection System tailored for 384-well reactions; 4) Analyze RT-PCR data by statistical methods to identify genes differentially expressed (up-regulated) in cancer. 
     These steps are set out in more detail below. 
     A) RNA Purification from Primary Normal and Tumor Tissues 
     This was performed using Qiagen RNeasy mini Kit CAT#74106. Tissue chucks typically yielded approximately 30 μg of RNA resulting in a final concentration of approximately 200 ng/μl if 150 μl of elution buffer was used. 
     After RNA was extracted using Qiagen&#39;s protocol, Ribogreen quantitation reagents from Molecular Probes was used to determine yield and concentration of RNA according to manufacture protocol. 
     Integrity of extracted RNA was assessed on EtBr stained agarose gel to determine if the 28S and 18S band have equal intensity. In addition, sample bands should be clear and visible. If bands were not visible or smeared down through the gel, the sample was discarded. 
     Integrity of extracted RNA was also assessed using Agilent 2100 according to manufacture protocol. The Agilent Bioanalyzer/“Lab-On-A-Chip” is a micro-fluidics system that generates an electropherogram of an RNA sample. By observing the ratio of the 18S and 28S bands and the smoothness of the baseline a determination of the level of RNA degradation was made. Samples that have 28S:18S ratio below 1 were discarded. 
     RNA samples were also examined by RT-PCR to determine level of genomic DNA contamination during extraction. In general, RNA samples were assayed directly using validated Taqman primers and probes of gene of interest in the presence and absence of Reverse Transcriptase. 12.5 ng of RNA was used per reaction in quadruplicate in a 384 wells format in a volume of 5 ul per well. (2 ul of RNA+3 ul of RT+ or RT− master mix). The following thermocycle parameters was used (2-step PCR): 
     Thermocycling Parameters 
       
     
       
         
           
               
               
               
               
            
               
                   
                   
               
               
                   
                 Reverse 
                 Amp. Gold 
                 PCR 
               
               
                   
                 Transcription 
                 Activation 
                 40 CYCLES 
               
            
           
           
               
               
               
               
               
            
               
                 Step 
                 HOLD 
                 HOLD 
                 Denature 
                 Anneal/Extend 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Temperature 
                 48° 
                 C. 
                 95° 
                 C. 
                 95° 
                 C. 
                 60° 
                 C. 
               
               
                 Time 
                 30 
                 min. 
                 10 
                 min. 
                 15 
                 sec. 
                 1 
                 min 
               
               
                   
               
            
           
         
       
     
     RNA samples required the following criteria to consider as pass QC.
         a. Ct difference must be 7 Ct or greater for a pass. Anything less is a “fail” and should be re-purified.   b. Mean sample Ct must be within 2 STDEV (all samples) from Mean (all samples) to pass. Use conditional formatting to find the outliers of the sample group. *Do not include the outliers on the RNA panels.   c. —RT amplification or (Ct) must be &gt;34 cycles or it is a “fail”.   d. Human genomic DNA must be between 23 and 27.6 Ct.       

     RNA was assembled into panel only if samples passed all QC steps (Gel run, Agilent and RT-PCR for genomic DNA). RNA was arrayed for cDNA synthesis. In general, a minimum of 10 normals and 20 tumors were required for each tumor type (i.e., if a tissue type can have a squamous cell carcinoma and an adenocarcinoma, 20 samples of each tumor type must be used (the same 10 normals will be used for each tumor type)). In general, 11 μg of RNA was required per panel. A fudge factor of at least 2 μg should be allowed; i.e., samples in database must have 13 μg, or they will be dropped during cDNA array. Sample numbers were arranged in ascending orders, starting at well A1 and working down the column on 96 wells format. Four control samples will be placed at the end of the panel: hFB, hrRNA, hgDNA and Water (in that order). An additional NTC control (water) was be placed in well A2. All lot numbers of controls were recorded. RNA samples were normalised to 100 ng/μl in Nuclease-free water. 11 μg of RNA was used, the total volume being 110 μl. NOTE: the concentration of RNA required can vary depending on the particular cDNA synthesis kit used. RNA samples that were below 100 ng/μl, were loaded pure. After normalization was complete, the block was sealed using the heat sealer with easy peel foil @ 175° C. for 2 seconds. The block was visually inspected to make sure foil was completely sealed. The manual sealer was then run over the foil. The block was stored in the −80° C. freezers, ready for cDNA synthesis. 
     B) Generation of First Strand cDNA from the Purified Tissue RNA for Real Time Quantitative PCR: 
     The following reaction mixture was setup in advance: 
     
       
         
           
               
               
               
             
               
                   
               
               
                 Reagents 
                 1 RXN Volumes (μl) 
                 RXN 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 10X Taqman RT BUFFER 
                 1 
                   
               
               
                 25 mM Magnesium chloride 
                 2.2 
               
               
                 10 mM deoxyNTPS mixture 
                 2 
               
               
                 50 uM Random Hexamer 
                 0.5 
               
               
                 Rnase inhibitor 
                 0.2 
               
               
                 50 u/ul MultiScribe Rev. Transcriptase 
                 0.25 
               
               
                 Water 
                 0.85 
               
               
                   
               
            
           
         
       
     
     Arrayed RNA in a 96 well block (11 μg) was distributed to daughter plates using Hydra to create 1 μg of cDNA synthesis per 96 well plate. Each of these daughter plates was used to setup RT reaction using the following thermocycle parameters: 
     
       
         
           
               
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 Incubation 
                 RT 
                 RT Inactivation 
               
               
                   
                 Step 
                 Hold 
                 Hold 
                 Hold 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Time 
                 10 
                 min. 
                 30 
                 min. 
                 5 
                 min. 
               
               
                   
                 Temperature 
                 25° 
                 C. 
                 48° 
                 C. 
                 95° 
                 C. 
               
               
                   
                   
               
            
           
         
       
     
     Upon completion of thermocyling, plates were removed from the cycler and using the Hydra pipet, 60 μl of 0.016M EDTA solution was pippetted into every well of cDNA the plates. Each cDNA plate (no more than 10 plates) was be pooled to a 2 ml-96 well block for storage. 
     C) Setup RT-PCR for Gene Expression Using ABI PRISM 7900HT Sequence Detection System Tailored for 384-Well Reactions: 
     Create Cocktails 
     
         
         1. This protocol was designed to create cocktails for a panel with 96 samples; this is 470 rxns for the whole panel. 
         2. FRT (Forward and Reverse primers and Target probe) mix was removed from −20° C. and place in 4° C. fridge thaw. 
         3. The first 10 FRT&#39;s to be made were taken out and placed in a cold metal rack or in a rack on ice. 
         4. New 1.5 ml cocktail tube caps were labelled with target number, side with the date of synthesis (found on FRT tube, if no date of synthesis label with today&#39;s date), and initials of scientist, one tube for each FRT being made. 
         5. FRT tubes and cocktails tubes were organised in rack so that they were in order and easy to keep track of. 
         6. When pipeting a p200 was used at speed 6. Aspiration was carried out at the surface of the liquid, and dispensed near the top of the inside of the tube. Tips were changed after each aspirate/dispense step.
       6.1 All cocktail tubes were opened and 94 μl of Ambion water (poured fresh daily) was added, then tubes were closed.   6.2 The FRT was Pulse vortexed 15 times, then centrifuged for 10 sec. One by one 141 μl of FRT was added to corresponding cocktail tubes.   6.3 When done with first 10, FRT was put back to −20° C. immediately (if vol was less than 10 μl then they were thrown away).   6.4 Cocktail was stored in 4° C. until ready to run. (−20° C. if it wait was longer than 1 day)   6.5 Master mix was added to cocktails when ready to run cocktails (refer to step 2.7)   
     
         7. Steps 1.3 to 1.6.5 were repeated for the next 10 cocktails, and so on until all cocktails had been made. 
       
    
     
       
         
           
               
             
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     2 μl of cDNA from the arrayed 96-well plates was added to the 3 μl of Taqman Master Mix to makeup a 5 μl QPCR reaction. 
     The primers and probes used in the QPCR for the PRLR gene are given in Table 3. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Primer 
                   
                   
                   
               
               
                   
                 Probe 
               
               
                 Gene 
                 ID 
                 ForwardPrimer 
                 ReversePrimer 
                 ProbeSequence 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 PRLR 
                 133 
                 TGGGCAGCAAACA 
                 GGTTTGCAGCGAA 
                 TCTCAGCCTACAT 
                   
               
               
                   
                   
                 GAGTTTAAGA 
                 CCTGG 
                 CCAGGACAGAAAT 
               
               
                   
                   
                 (SEQ ID 
                 (SEQ ID 
                 ACCTTG 
               
               
                   
                   
                 NO: 3) 
                 NO: 4) 
                 (SEQ ID 
               
               
                   
                   
                   
                   
                 NO: 5) 
               
               
                   
               
            
           
         
       
     
     D) Analyze RT-PCR Data by Statistical Methods to Identify Genes Differentially Expressed (Up-Regulated) in Cancer: 
     The expression level of a target gene in both normal and tumor samples was determined using Quantitative RT-PCR using the ABI PRISM 7900HT Sequence Detection System (Applied Biosystems, California). The method is based on the quantitation of the initial copy number of target template in comparison to that of a reference (normalizer) housekeeper gene (Pre-Developed TaqMan® Assay Reagents Gene Expression Quantification Protocol, Applied Biosystems, 2001). Accumulation of DNA product with each PCR cycle is related to amplicon efficiency and the initial template concentration. Therefore the amplification efficiency of both the target and the normalizer must be similar. The threshold cycle (C T ), which is dependent on the starting template copy number and the DNA amplification efficiency, is a PCR cycle during which PCR product growth is exponential. Each assay was performed in quadruplicates; therefore, 4 C T  values were obtained for the target gene in a given sample. Simultaneously, the expression level of a group of housekeeper genes were also measured in the same fashion. The outlier within the 4 quadruplicates is detected and removed if the standard deviation of the remaining 3 triplicates is 30% or less compared to the standard deviation of the original 4 quadruplicates. The mean of the remaining C T  values (designated as C t  or C n ) was calculated and used in the following computation. 
     Data Normalization. For normalization, a ‘universal normalizer’ was developed that is based on the set of housekeepers available for analysis (5 to 8 genes). Briefly, the housekeeper genes were weighted according to their variations in expression level across the whole panel of tissue samples. For n samples of the same tissue type, the weight (w) for the lath house keeper gene was calculated with the following formulas: 
     
       
         
           
             
               
                 
                   
                     w 
                     k 
                   
                   = 
                   
                     
                       1 
                       / 
                       
                         S 
                         k 
                         2 
                       
                     
                     
                       
                         ∑ 
                         
                           k 
                           = 
                           1 
                         
                         n 
                       
                        
                       
                         1 
                         / 
                         
                           S 
                           k 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
     Where S k  stands for the standard deviation of the kth housekeeper gene across the all samples of same tissue type in the panel. The mean expression of all housekeeper genes in the ith sample (Mi) was estimated using the weighted least square method, and the difference between the Mi and the average of all Mi is computed as the normalization factor Ni for the ith sample (Equation 2). The mean Ct value of the target gene in the ith sample was then normalized by subtracting the normalization factor Ni. The performance of the above normalization method was validated by comparing the correlation between RT-PCR and microarray data that were generated from the same set of samples: increased correlation between RT-PCR data and microarray data was observed after applying the above normalization method. 
     
       
         
           
             
               
                 
                   
                     N 
                     i 
                   
                   = 
                   
                     
                       M 
                       i 
                     
                     - 
                     
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             1 
                           
                           n 
                         
                          
                         
                           M 
                           i 
                         
                       
                       n 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   2 
                 
               
             
           
         
       
     
     Identification of significantly dysregulated Genes. To, determine if a gene is significantly up-regulated in the tumor versus normal samples, two statistics, t (Equation 3) and Receiver Operating Characteristic (ROC; Equation 4) were calculated: 
     
       
         
           
             
               
                 
                   t 
                   = 
                   
                     
                       
                         
                           C 
                           _ 
                         
                         t 
                       
                       - 
                       
                         
                           C 
                           _ 
                         
                         n 
                       
                     
                     
                       
                         
                           
                             S 
                             t 
                             2 
                           
                           
                             n 
                             t 
                           
                         
                         + 
                         
                           
                             S 
                             n 
                             2 
                           
                           
                             n 
                             n 
                           
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   3 
                 
               
             
             
               
                 
                   
                     ROC 
                      
                     
                       ( 
                       
                         t 
                         0 
                       
                       ) 
                     
                   
                   = 
                   
                     P 
                      
                     
                       [ 
                       
                         
                           C 
                           t 
                         
                         ≤ 
                         
                           
                             C 
                             n 
                           
                            
                           
                             ( 
                             
                               t 
                               0 
                             
                             ) 
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   4 
                 
               
             
           
         
       
     
     where  C   t  is the average of C t  in the tumor sample group,  C   n  is the average of C n  in the normal sample group, S t , S n  are standard deviations of the tumor and normal control groups, and n t , n n , are the number of the tumor and normal samples used in the analysis. The degree of freedom v′ of t is calculated as: 
     
       
         
           
             
               
                 
                   
                     v 
                     ′ 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           
                             
                               S 
                               t 
                               2 
                             
                             
                               n 
                               t 
                             
                           
                           + 
                           
                             
                               S 
                               n 
                               2 
                             
                             
                               n 
                               n 
                             
                           
                         
                         ) 
                       
                       2 
                     
                     
                       
                         
                           
                             ( 
                             
                               
                                 S 
                                 t 
                                 2 
                               
                               
                                 n 
                                 t 
                               
                             
                             ) 
                           
                           2 
                         
                         
                           
                             n 
                             t 
                           
                           - 
                           1 
                         
                       
                       + 
                       
                         
                           
                             ( 
                             
                               
                                 S 
                                 t 
                                 2 
                               
                               
                                 n 
                                 n 
                               
                             
                             ) 
                           
                           2 
                         
                         
                           
                             n 
                             n 
                           
                           - 
                           1 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   5 
                 
               
             
           
         
       
     
     In the ROC equation, t 0  is the accepted false positive rate in the normal population, which is set to 0.1 in our study. Therefore, C n (t 0 ) is the 10 percentile of C n , in the normal samples, and the ROC (0.1) is the percentage of tumor samples with C t  lower than the 10 percentile of the normal samples. The t statistic identifies genes that show higher average expression level in tumor samples compared to normal samples, while the ROC statistic is more suitable to identify genes that show elevated expression level only in a subset of tumors. The rationale of using ROC statistic is discussed in detail in Pepe, et al (2003) Biometrics 59, 133-142. The distribution of t under null hypothesis is empirically estimated by permutation to avoid normal distribution assumption, in which we randomly assign normal or tumor labels to the samples, and then calculate the t statistic (t p ) as above for 2000 times. The p value was then calculated as the number of t p  less than t from real samples divided by 2000. To access the variability of ROC, the samples were bootstrapped 2000 times, each time, a bootstrap ROC(ROC b ) was calculated as above. If 97.5% of 2000 ROC b  is above 0.1, the acceptable false positive rate we set for normal population, the ROC from the real samples was then considered as statistically significant. The threshold to determine significance was set at &gt;20% incidence for ROC and &lt;0.05 for the T-test P value. 
     Application of the above methodologies allowed us to model 3 hypothetical distributions between the normal and sample sets ( FIG. 2 ). 
     In scenario I, there was essentially complete separation between the two sample populations (control and disease). Both the ROC and T-Test score this scenario with high significance. In scenario II, the samples exhibit overlapping distributions and only a subset of the disease sample is distinct from the control (normal) population. Only the ROC method will score this scenario as significant. In scenario III, the disease sample population overlaps entirely with the control population. In contrast to scenario I and II, only the T-Test method will score this scenario as significant. In sum, the combination of both statistical methods allows one to accurately characterize the expression pattern of a target gene within a sample population. 
     Results of these tests are expressed in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Cancer Typer, % Incidence vs. Corresponding Normal 
               
            
           
           
               
               
               
            
               
                 Breast 
                 Breast 
                 Prostate 
               
               
                   
               
               
                 40% 
                 34% 
                 55% 
               
               
                   
               
            
           
         
       
     
     Results for expression of PRLR in cancerous and normal tissue is shown in Table 4A. 
     
       
         
           
               
               
               
             
               
                 TABLE 4A 
               
             
            
               
                   
               
               
                 Data 
                 Analysis 
                 Cancer Type, % Incidence vs. Corresponding Normal 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Source 
                 Method 
                 Breast 
                 Cervix 
                 Colon 
                 Kidney 
                 Liver 
                 Lung 
                 Lymphoid 
                 Ovary 
                 Pancreas 
                 Prostate 
                 Skin 
               
               
                   
               
               
                 Sagres 
                 ROC 
                 40% 
                 ns 
                 ns 
                 ns 
                 ns 
                 34% 
                 ns 
                 ns 
                 ns 
                 ns 
                 45% 
               
               
                 QPCR 
                 P-Value 
                 0.1315 
                 0.6085 
                 0.36 
                 0.319 
                 0.138 
                 0.191 
                 0.754 
                 1 
                 1 
                 0.03 
                 0.449 
               
               
                   
               
            
           
         
       
     
     Example 3 
     Detection of PRLR-Sequences in Human Cancer Cells and Tissues 
     DNA from prostate and breast cancer tissues and other human cancer tissues, human colon, normal human tissues including non-cancerous prostate, and from other human cell lines are extracted following the procedure of Delli Bovi et al. (1986, Cancer Res. 46:6333-6338). The DNA is resuspended in a solution containing 0.05 M Tris HCl buffer, pH 7.8, and 0.1 mM EDTA, and the amount of DNA recovered is determined by microfluorometry using Hoechst 33258 dye. Cesarone, C. et al., Anal Biochem 100:188-197 (1979). 
     Polymerase chain reaction (PCR) is performed using Taq polymerase following the conditions recommended by the manufacturer (Perkin Elmer Cetus) with regard to buffer, Mg 2+ , and nucleotide concentrations. Thermocycling is performed in a DNA cycler by denaturation at 94° C. for 3 min. followed by either 35 or 50 cycles of 94° C. for 1.5 min., 50° C. for 2 min. and 72° C. for 3 min. The ability of the PCR to amplify the selected regions of the PRLR gene is tested by using a cloned PRLR polynucleotide(s) as a positive template(s). Optimal Mg 2+ , primer concentrations and requirements for the different cycling temperatures are determined with these templates. The master mix recommended by the manufacturer is used. To detect possible contamination of the master mix components, reactions without template are routinely tested. 
     Southern blotting and hybridization are performed as described by Southern, E. M., (J. Mol. Biol. 98:503-517, 1975), using the cloned sequences labeled by the random primer procedure (Feinberg, A. P., et al., 1983, Anal. Biochem. 132:6-13). Prehybridization and hybridization are performed in a solution containing 6×SSPE, 5% Denhardt&#39;s, 0.5% SDS, 50% formamide, 100 μg/ml denaturated salmon testis DNA, incubated for 18 hrs at 42° C., followed by washings with 2×SSC and 0.5% SDS at room temperature and at 37° C. and finally in 0.1×SSC with 0.5% SDS at 68° C. for 30 min (Sambrook et al., 1989, in “Molecular Cloning: A Laboratory Manual”, Cold Spring Harbor Lab. Press). For paraffin-embedded tissue sections the conditions described by Wright and Manos (1990, in “PCR Protocols”, Innis et al., eds., Academic Press, pp. 153-158) are followed using primers designed to detect a 250 bp sequence. 
     Example 4 
     Expression of Cloned Polynucleotides in Host Cells 
     To study the protein products of PRLR genes, restriction fragments from PRLR DNA are cloned into the expression vector pMT2 (Sambrook, et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press pp 16.17-16.22 (1989)) and transfected into COS cells grown in DMEM supplemented with 10% FCS. Transfections are performed employing calcium phosphate techniques (Sambrook, et al (1989) pp. 16.32-16.40, supra) and cell lysates are prepared forty-eight hours after transfection from both transfected and untransfected COS cells. Lysates are subjected to analysis by immunoblotting using anti-peptide antibody. 
     In immunoblotting experiments, preparation of cell lysates and electrophoresis are performed according to standard procedures. Protein concentration is determined using BioRad protein assay solutions. After semi-dry electrophoretic transfer to nitrocellulose, the membranes are blocked in 500 mM NaCl, 20 mM Tris, pH 7.5, 0.05% Tween-20 (TTBS) with 5% dry milk. After washing in TTBS and incubation with secondary antibodies (Amersham), enhanced chemiluminescence (ECL) protocols (Amersham) are performed as described by the manufacturer to facilitate detection. 
     Example 5 
     Generation of Antibodies Against Polypeptides 
     Polypeptides, unique to PRLR genes are synthesized or isolated from bacterial or other (e.g., yeast, baculovirus) expression systems and conjugated to rabbit serum albumin (RSA) with m-maleimido benzoic acid N-hydroxysuccinimide ester (MBS) (Pierce, Rockford, Ill.). Immunization protocols with these peptides are performed according to standard methods. Initially, a pre-bleed of the rabbits is performed prior to immunization. The first immunization includes Freund&#39;s complete adjuvant and 500 μg conjugated peptide or 100 μg purified peptide. All subsequent immunizations, performed four weeks after the previous injection, include Freund&#39;s incomplete adjuvant with the same amount of protein. Bleeds are conducted seven to ten days after the immunizations. 
     For affinity purification of the antibodies, the corresponding PRLR polypeptide is conjugated to RSA with MBS, and coupled to CNBr-activated Sepharose (Pharmacia, Uppsala, Sweden). Antiserum is diluted 10-fold in 10 mM Tris-HCl, pH 7.5, and incubated overnight with the affinity matrix. After washing, bound antibodies are eluted from the resin with 100 mM glycine, pH 2.5. 
     Example 6 
     Generation of Monoclonal Antibodies Against a PRLR Polypeptide 
     A non-denaturing adjuvant (Ribi, R730, Corixa, Hamilton Mont.) is rehydrated to 4 ml in phosphate buffered saline. 100 μl of this rehydrated adjuvant is then diluted with 400 μl of Hank&#39;s Balanced Salt Solution and this is then gently mixed with the cell pellet used for immunization. Approximately 500 μg conjugated peptide or 100 μg purified peptide and Freund&#39;s complete are injected into Balb/c mice via foot-pad, once a week. After 6 weeks of weekly injection, a drop of blood is drawn from the tail of each immunized animal to test the titer of antibodies against PRLR polypeptides using FACS analysis. When the titer reaches at least 1:2000, the mice are sacrificed in a CO 2  chamber followed by cervical dislocation. Lymph nodes are harvested for hybridoma preparation. Lymphocytes from mice with the highest titer are fused with the mouse myeloma line X63-Ag8.653 using 35% polyethylene glycol 4000. On day 10 following the fusion, the hybridoma supernatants are screened for the presence of CAP-specific monoclonal antibodies by fluorescence activated cell sorting (FACS). Conditioned medium from each hybridoma is incubated for 30 minutes with a combined aliquot of PC3, Colo-205, LnCap, or Panc-1 cells. After incubation, the cell: samples are washed, resuspended in 0.1 ml diluent and incubated with 1 μg/ml of FITC conjugated F(ab′)2 fragment of goat anti-mouse IgG for 30 min at 4° C. The cells are washed, resuspended in 0.5 ml FACS diluent and analyzed using a FACScan cell analyzer (Becton Dickinson; San Jose, Calif.). Hybridoma clones are selected for further expansion, cloning, and characterization based on their binding to the surface of one or more of cell lines which express the PRLR polypeptide as assessed by FACS. A hybridoma making a monoclonal antibody designated mAbPRLR which binds an antigen designated Ag-CA.x and an epitope on that antigen designated Ag-CA.x.1 is selected. 
     Example 7 
     ELISA Assay for Detecting PRLR Related Antigens 
     To test blood samples for antibodies that bind specifically to recombinantly produced PRLR antigens, the following procedure is employed. After a recombinant PRLR related protein is purified, the recombinant protein is diluted in PBS to a concentration of 5 μg/ml (500 ng/100 μl). 100 microliters of the diluted antigen solution is added to each well of a 96-well Immulon 1 plate (Dynatech Laboratories, Chantilly, Va.), and the plate is then incubated for 1 hour at room temperature, or overnight at 4° C., and washed 3 times with 0.05% Tween 20 in PBS. Blocking to reduce nonspecific binding of antibodies is accomplished by adding to each well 200 μl of a 1% solution of bovine serum albumin in PBS/Tween 20 and incubation for 1 hour. After aspiration of the blocking solution, 100 μl of the primary antibody solution (anticoagulated whole blood, plasma, or serum), diluted in the range of 1/16 to 1/2048 in blocking solution, is added and incubated for 1 hour at room temperature or overnight at 4° C. The wells are then washed 3 times, and 100 μl of goat anti-human IgG antibody conjugated to horseradish peroxidase (Organon Teknika, Durham, N.C.), diluted 1/500 or 1/1000 in PBS/Tween 20, 100 μl of o-phenylenediamine dihydrochloride (OPD, Sigma) solution is added to each well and incubated for 5-15 minutes. The OPD solution is prepared by dissolving a 5 mg OPD tablet in 50 ml 1% methanol in H 2 O and adding 50 μl 30% H 2 O 2  immediately before use. The reaction is stopped by adding 25 μl of 4M H 2 SO 4 . Absorbances are read at 490 m in a microplate reader (Bio-Rad). 
     Example 8 
     Identification and Characterization of PRLR on Cancer Cell Surface 
     A cell pellet of proximately 25 ul packed cell volume of a cancer cell preparation is lysed by first diluting the cells to 0.5 ml in water followed by freezing and thawing three times. The solution is centrifuged at 14,000 rpm. The resulting pellet, containing the cell membrane fragments, is resuspended in 50 μl of SDS sample buffer (Invitrogen, Carlsbad, Calif.). The sample is heated at 80° C. for 5 minutes and then centrifuged for 2 minutes at 14,000 rpm to remove any insoluble materials. 
     The samples are analyzed by Western blot using a 4 to 20% polyacrylamide gradient gel in Tris-Glycine SDS (Invitrogen; Carlsbad Calif.) following the manufacturer&#39;s directions. Ten microliters of membrane sample are applied to one lane on the polyacrylamide gel. A separate 10 μL sample is reduced first by the addition of 2 μL of dithiothreitol (100 mM) with heating at 80° C. for 2 minutes and then loaded into another lane. Pre-stained molecular weight markers SeeBlue Plus2 (Invitrogen; Carlsbad, Calif.) are used to assess molecular weight on the gel. The gel proteins are transferred to a nitrocellulose membrane using a transfer buffer of 14.4 g/l glycine, 3 g/l of Tris Base, 10% methanol, and 0.05% SDS. The membranes are blocked, probed with a CAP-specific monoclonal antibody (at a concentration of 0.5 ug/ml), and developed using the Invitrogen WesternBreeze Chromogenic Kit-AntiMouse according to the manufacturer&#39;s directions. In the reduced sample of the tumor cell membrane samples, a prominent band is observed migrating at a molecular weight within about 10% of the predicted molecular weight of the corresponding PRLR protein. 
     Example 9 
     Preparation of Vaccines 
     The present invention also relates to a method of stimulating an immune response against cells that express PRLR polypeptides in a patient using PRLR polypeptides of the invention that act as an antigen produced by or associated with a malignant cell. This aspect of the invention provides a method of stimulating an immune response in a human against cancer cells or cells that express PRLR polynucleotides and polypeptides. The method comprises the step of administering to a human an immunogenic amount of a polypeptide comprising: (a) the amino acid sequence of a human PRLR protein or (b) a mutein or variant of a polypeptide comprising the amino acid sequence of a human PRLR protein. 
     Example 10 
     Generation of Transgenic Animals Expressing Polypeptides as a Means for Testing Therapeutics 
     PRLR nucleic acids are used to generate genetically modified non-human animals, or site specific gene modifications thereof, in cell lines, for the study of function or regulation of prostate tumor-related genes, or to create animal models of diseases, including prostate cancer. The term “transgenic” is intended to encompass genetically modified animals having an exogenous PRLR gene(s) that is stably transmitted in the host cells where the gene(s) may be altered in sequence to produce a modified protein, or having an exogenous PRLR LTR promoter operably linked to a reporter gene. Transgenic animals may be made through a nucleic acid construct randomly integrated into the genome. Vectors for stable integration include plasmids, retroviruses and other animal viruses, YACs, and the like. Of interest are transgenic mammals, e.g. cows, pigs, goats, horses, etc., and particularly rodents, e.g. rats, mice, etc. 
     The modified cells or animals are useful in the study of PRLR gene function and regulation. For example, a series of small deletions and/or substitutions may be made in the PRLR gene to determine the role of different genes in tumorigenesis. Specific constructs of interest include, but are not limited to, antisense constructs to block PRLR gene expression, expression of dominant negative PRLR gene mutations, and over-expression of a PRLR gene. Expression of a PRLR gene or variants thereof in cells or tissues where it is not normally expressed or at abnormal times of development is provided. In addition, by providing expression of proteins derived from PRLR gene in cells in which it is otherwise not normally produced, changes in cellular behavior can be induced. 
     DNA constructs for random integration need not include regions of homology to mediate recombination. Conveniently, markers for positive and negative selection are included. For various techniques for transfecting mammalian cells, see Keown et al., Methods in Enzymology 185:527-537 (1990). 
     For embryonic stem (ES) cells, an ES cell line is employed or embryonic cells are obtained freshly from a host, e.g. mouse, rat, guinea pig, etc. Such cells are grown on an appropriate fibroblast-feeder layer or grown in the presence of appropriate growth factors, such as leukemia inhibiting factor (LIF). When ES cells are transformed, they may be used to produce transgenic animals. After transformation, the cells are plated onto a feeder layer in an appropriate medium. Cells containing the construct may be detected by employing a selective medium. After sufficient time for colonies to grow, they are picked and analyzed for the occurrence of integration of the construct. Those colonies that are positive may then be used for embryo manipulation and blastocyst injection. Blastocysts are obtained from 4 to 6 week old superovulated females. The ES cells are trypsinized, and the modified cells are injected into the blastocoel of the blastocyst. After injection, the blastocysts are returned to each uterine horn of pseudopregnant females. Females are then allowed to go to term and the resulting chimeric animals screened for cells bearing the construct. By providing for a different phenotype of the blastocyst and the ES cells, chimeric progeny can be readily detected. 
     The chimeric animals are screened for the presence of the modified gene and males and females having the modification are mated to produce homozygous progeny. If the gene alterations cause lethality at some point in development, tissues or organs are maintained as allogeneic or congenic grafts or transplants, or in in vitro culture. The transgenic animals may be any non-human mammal, such as laboratory animals, domestic animals, etc. The transgenic animals are used in functional studies, drug screening, etc., e.g. to determine the effect of a candidate drug on prostate cancer, to test potential therapeutics or treatment regimens, etc. 
     Example 11 
     Diagnostic Imaging Using CA Specific Antibodies 
     The present invention encompasses the use of antibodies to PRLR polypeptides to accurately stage cancer patients at initial presentation and for early detection of metastatic spread of cancer. Radioimmunoscintigraphy using monoclonal antibodies specific for PRLR polypeptides can provide an additional cancer-specific diagnostic test. The monoclonal antibodies of the instant invention are used for histopathological diagnosis of carcinomas. 
     Subcutaneous human xenografts of cancer cells in nude mice are used to test whether a technetium-99m ( 99m Tc)-labeled monoclonal antibody of the invention can successfully image the xenografted cancer by external gamma scintography as described for seminoma cells by Marks, et al., Brit. J. Urol. 75:225 (1995). Each monoclonal antibody specific for a PRLR polypeptide is purified from ascitic fluid of BALB/c mice bearing hybridoma tumors by affinity chromatography on protein A-Sepharose. Purified antibodies, including control monoclonal antibodies such as an avidin-specific monoclonal antibody (Skea, et al., J. Immunol. 151:3557 (1993)) are labeled with  99m Tc following reduction, using the methods of Mather, et al., J. Nucl. Med. 31:692 (1990) and Zhang et al., Nucl. Med. Biol. 19:607 (1992). Nude mice bearing human cancer cells are injected intraperitoneally with 200-500 μCi of  99m Tc-labeled antibody. Twenty-four hours after injection, images of the mice are obtained using a Siemens ZLC3700 gamma camera equipped with a 6 mm pinhole collimator set approximately 8 cm from the animal. To determine monoclonal antibody biodistribution following imaging, the normal organs and tumors are removed, weighed, and the radioactivity of the tissues and a sample of the injectate are measured. Additionally, PRLR-specific antibodies conjugated to antitumor compounds are used for cancer-specific chemotherapy. 
     Example 12 
     Immunohistochemical Methods 
     Frozen tissue samples from cancer patients are embedded in an optimum cutting temperature (OCT) compound and quick-frozen in isopentane with dry ice. Cryosections are cut with a Leica 3050 CM mictrotome at thickness of 5 μm and thaw-mounted on vectabound-coated slides. The sections are fixed with ethanol at −20° C. and allowed to air dry overnight at room temperature. The fixed sections are stored at −80° C. until use. For immunohistochemistry, the tissue sections are retrieved and first incubated in blocking buffer (PBS, 5% normal goat serum, 0.1% Tween 20) for 30 minutes at room temperature, and then incubated with the PRLR-specific monoclonal antibody and control monoclonal antibodies diluted in blocking buffer (1 μg/ml) for 120 minutes. The sections are then washed three times with the blocking buffer. The bound monoclonal antibodies are detected with a goat anti-mouse IgG+IgM (H+L) F(ab′) 2 -peroxidase conjugates and the peroxidase substrate diaminobenzidine (1 mg/ml, Sigma Catalog No. D 5637) in 0.1 M sodium acetate buffer pH 5.05 and 0.003% hydrogen peroxide (Sigma cat. No. H1009). The stained slides are counter-stained with hematoxylin and examined under Nikon microscope. 
     Monoclonal antibody against a PRLR protein (antigen) is used to test reactivity with various cell lines from different types of tissues. Cells from different established cell lines are removed from the growth surface without using proteases, packed and embedded in OCT compound. The cells are frozen and sectioned, then stained using a standard IHC protocol. The CellArray™ technology is described in WO 01/43869. Normal tissue (human) obtained by surgical resection are frozen and mounted. Cryosections are cut with a Leica 3050 CM mictrotome at thickness of 5 μm and thaw-mounted on vectabound-coated slides. The sections are fixed with ethanol at −20° C. and allowed to air dry overnight at room temperature. PolyMICA™ Detection kit is used to determine binding of a PRLR-specific monoclonal antibody to normal tissue. Primary monoclonal antibody is used at a final concentration of 1 μg/ml. 
     Results from immunohistochemistry analyses are set out in Table 5. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 # patients PRLR (+) 
                   
               
               
                 Patient tissue 
                 Total patients 
                 (&gt;10% tumor cells) 
                 Percentage 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Breast CA 
                   
                   
                   
               
               
                 Infiltrating ductal CA 
                 129 
                 66 
                 51% 
               
               
                 Adenocarcinoma 
                 24 
                 14 
                 58% 
               
               
                 Metastatic 
                 28 
                 7 
                 25% 
               
               
                 Prostate CA 
                 46 
                 10 
                 22% 
               
               
                 Lung CA 
                 47 
                 22 
                 47% 
               
               
                   
               
            
           
         
       
     
     Example 13 
     PRLR is Transforming and Tumorigenic 
     I. Rat-1 Stable Cell Line Generation 
     Cells were trypsinized, washed once with PBS, resuspended in cell culture medium [DMEM(containing glutamine)+10% FBS (fetal bovine serum)], and 2×10 6  cells per well were seeded into 6-well culture plates in a total volume of 2 mls. Plasmid DNA (2 ug) was mixed with 100 μl serum-free medium, followed by addition of 10 μl of Superfect transfection reagent (Qiagen), vortexed for 10 seconds and incubated at room-temperature for 10 minutes. While the complex was forming, the cells were washed twice with PBS. 600 ul DMEM+10% FBS was then added to the complex, mixed, transferred to the cell-containing well, and incubated for 4 hours at 37° C. Then 2 mls DMEM+10% FBS was added followed by a 48 hr incubation at 37° C., 5% CO 2 . 
     The cells were then trypsinized, resuspended with 1 ml DMEM+10% FBS+800 ug/ml G418 and seeded at different densities (1:10, 1:20 up to 1:100) in 10-cm dishes. The dishes were incubated at 37° C., 5% CO 2  until G418-resistant colonies formed, after which individual clones were picked and transferred to a 24-well dish containing 1 ml DMEM+10% FBS+800 ug/ml G418. 
     The cloned cells were expanded further and screened for the presence of the plasmid-expressed gene product, generally by western blot analysis. 
     II. Soft Agar Transformation Assay 
     A 0.7% and 1% low temperature melting agarose (DNA grade, J. T. Baker) solution was prepared in sterile water, heated to boiling, and cooled to 40° C. in a waterbath. A 2×DMEM solution was prepared by mixing 10× powdered DMEM (Invitrogen) in water, mixing, followed by addition of 3.7 g of NaHCO 3  per liter volume, followed by addition of FBS to 20%. 0.75 ml of the culture medium (pre-warmed to 40° C.) was mixed with 0.75 ml of the 1% agarose solution and the final 1.5 ml 0.5% agarose solution was added per well to a 6-well dish. Rat1 stable cell were trypsinized, washed twice with PBS, and diluted to 50000 cells per ml 1×DMEM+10% FBS. 0.1 ml of this cell suspension was mixed gently with 1 ml 2×DMEM+20% FBS and 1 ml 0.7% agarose solution and the final 1.5 ml suspension was added to the 6-well dish containing the solidified 0.5% agar. These agar plates were placed at 37° C., 5% CO 2  in a humidified incubator for 10-14 days and the cells were re-feed fresh 1×DMEM+10% FBS every 3-4 days. 
     The results of the Rat-1 and Rat-1/PRLR soft agar assay are shown in  FIG. 3 . As can be seen from these results, expression of PRLR in Rat-1 cells increases the proliferation of the cells. 
     III. Mouse Tumorigenicity Assays 
     Rat-1 stable cell lines were grown in two T150 flasks to 70-80% confluency. The cells were trypsinized, washed twice in PBS, and resuspended with PBS to 107, 106, and 105 cells/ml. The cell suspension was kept on ice until injection into mice. Female NOD.CB17-Prkdc&lt;scid&gt;/J mice, 3-5 weeks of age were obtained from JAX West&#39;s M-3 facility (UC Davis) and housed 4 per cage in an isolator unit at JAX West&#39;s West Sacramento facility. Using a 25 gauge needle, mice were injected with 0.1 ml cell suspension subcutaneously in the thoracic region (2 sites per mouse). Once a tumor began to form, tumor growth was measured twice per week using a caliper. The tumor was measured in two directions, rostral-caudal and medial-lateral. Measurements were recorded as width×length and the tumor volume was calculated using the conversion formula (length×width2)/2. 
     The results of the tumorigenicity assay of Rat-1 cell lines are shown in  FIG. 4 . It is clear that transfection of the PRLR gene (here referred to as code 1-1) causes a marked increase in tumorigenicity of the cells. 
     Example 14 
     PRLR(+) Cells Predominantly Express the Long Form of PRLR 
     Human cancer cell lines were seeded overnight in 10-cm dish at a density of 1×106 cells/dish. Two days later, cells were rinsed once in PBS and lysed in a buffer consisting of 50 mM Tris-HCl, pH7.5, 150 mM NaCl, 1 mM EDTA, 1% NP-40, 1 mM Na3OV4, 50 mM NaF, 0.25% deoxycholate and protease inhibitors. Tubes were spun down at 14,000 rpm in a refrigerated microfuge and lysates were quantitated using Bradford reagent. 20 ug of whole cell lysates were separated by 10% SDS-PAGE and proteins were detected using PRLR monoclonal antibody (Zymed, clone 1A2BI) and ECL. 
       FIG. 5  shows that most human cancer cell lines express the long form of PRLR (LF). In addition to the long form, three more isoforms were found in T47D human cell line ( FIG. 5 ) including the intermediate form (IF) and the short isoforms S1a and S1b. 
     Example 15 
     siRNA Inhibition of Proliferation and Cell Growth 
     I. Transfection 
     siRNAs for PRLR were designed (Table 6) to be complementary to the PRLR gene sequence and reduction of gene expression. siRNA transfections were performed according to the recommendations of the transfection reagent vendor (Invitrogen). The final siRNA concentration used to transfect the cells was 100 nM, unless otherwise noted. In general, cells were grown to 30-50% confluency on the day of transfection (e.g. 5000-20000 cells per well for a 48-well plate). 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Table of PRLR siRNA oligonucleotides 
               
            
           
           
               
               
            
               
                 siRNA 
                   
               
               
                 Name 
                 Target Sequence 
               
               
                   
               
            
           
           
               
               
               
            
               
                 cc477-1Si 
                 AACCAGACCATGGATACTGGA (SEQ ID NO:6) 
                   
               
               
                   
               
               
                 cc477-2Si 
                 GAGGACTTCCTACCAATTATT (SEQ ID NO:7) 
               
               
                   
               
               
                 cc477-12Si 
                 AAGGGCTATAGCATGGTGACC (SEQ ID NO:8) 
               
               
                   
               
            
           
         
       
     
     A mixture of Opti-MEM I (Invitrogen), siRNA oligo, and Plus Reagent (Invitrogen) was prepared as recommended by Invitrogen and incubated at room-temperature for 15-20 minutes. This mix was then combined with an appropriate volume of an Oligofectamine (Invitrogen) reagent in Opti-MEM/siRNA/Plus Reagent mix and incubated for 15 minutes at room-temperature. The cell culture medium was removed from the cell-containing wells and replaced with the appropriate volume of Opti-MEM I. An appropriate volume of siRNA/Oligofectamine mix was added to the cells. The cells were then incubated at 37° C., 5% CO2 for 4 hours followed by addition of growth medium. Day 0 plates are analyzed immediately. For later time-points, the transfection reagent/medium mixture was replaced with fresh cell culture medium and the cells are incubated at 37° C., 5% CO2. The transfection mixture volumes were scaled up or down depending on the tissue culture plate, ie 6-, 48-, 96-well plate. 
     II. RNA Extraction for QPCR Analysis of siRNA Transfected Cells 
     For conducting QPCR analysis, the RNA was extracted from the transfected cells using an RNAesy 96 Kit (Qiagen) and was performed according to the manufacturer&#39;s recommendations. In general, the cells from one well of a 48-well plate were collected, lysed, and the RNA was collected in one well of the 96-well RNAesy plate. 
     III. Cell Proliferation Assays of siRNA Transfected Cells 
     Proliferation assays were performed using general assays, such as Cell Titer Glo (Promega) or WST-1 (Roche Applied Science) and were performed according to the manufacturers&#39; recommendations. In general, assays were performed in triplicate. The percent inhibition of proliferation was calculated relative to cells that had been transfected with a scrambled siRNA control oligo. 
       FIG. 6  shows the effect of PRLR-specific siRNA on MCF-7 human cancer cell line proliferation. MCF-7 cell line was transfected either with PRLR-specific, a positive control (Eg5) or a negative control (Eg5s) siRNAs. Cell proliferation was measured three days post-transfection by CellTiter Glo assay. The results demonstrate that PRLR knock-down specifically impairs the proliferation of the MCF-7 cell line.  FIG. 6  shows the reduction of cell proliferation in siRNA cc477-1Si and cc477-12Si treated cells when compared to a scrambled siRNA control. As shown in  FIG. 6 , the two PRLR-specific siRNAs knock-down PRLR protein relative to the control. PRLR knockdown in MCF-7, by cc477-1 Si and 12Si oligonucleotides, also caused a dramatic reduction in the ability of MCF-7 in soft-agar. 
     Example 16 
     Phosphorylation of STAT5 and MAPK by PRL is Dose/Time-Dependent in T47D Cells 
     Cells were seeded overnight in 6 well plates at a density of 3×105 cells/ml in phenol red-free RPMI/10% FBS. The following day, media was replaced with serum-free RPMI for 30 min. For time-dependency study, cells were stimulated with 50 ng/ml human recombinant prolactin hPRL for various times (0-50 minutes). In contrast, for dose-dependency study cells were stimulated with increasing concentrations of hPRL (0-100 ng/ml) for 30 minutes. Cells were, then, rinsed once in PBS and lyzed in a buffer consisting of 50 mM Tris-HCl, pH7.5, 150 mM NaCl, 1 mM EDTA, 1% NP-40, 1 mM Na 3 OV 4 , 50 mM NaF, 0.25% deoxycholate and protease inhibitors. Tubes were spun down at 14,000 rpm in a refrigerated microfuge and lysates were quantitated using Bradford reagent. Whole cell lysate (20 ug for Phospho-STAT5 and Phospho-MAPK and 10 ug for STAT5 and MAPK proteins) was separated by 10% SDS-PAGE and proteins were detected using phospho-specific antibodies for STAT5A/B (Y694/Y699, Upstate) or MAPK (Thr202/Tyr204, Cell Signaling Technology) and ECL. Equal protein loading was determined by staining with antibodies specific for total STAT5 (BD-Transduction Lab) or MAPK (Cell Signaling Technology). 
       FIG. 7  shows that hPRL stimulates STAT5 and MAPK phosphorylation in a time-dependent manner. Maximal phosphorylation of both proteins is detected at 30 minutes post-stimulation with hPRL. Also, hPRL induced STA5 and MAPK phosphorylation in a dose-dependent manner ( FIG. 7 ). 
     Example 17 
     Testing of PRLR Antibodies In Vivo 
     T47D or MCF-7 breast cancer cell lines with matrigel (1:1) are injected subcutaneously (T47D) or in the mammary fat pad (MCF-7) of female nu/nu mice (pre-implanted with slow-release E2 pellets), aged 4-6 weeks. Tumor volume and animal body weight are monitored weekly. When tumors reach approximately 100-150 mm in size, animals will be randomized into treatment groups and dosed accordingly with vehicle control, PRLR antibody at one or more doses, optionally with or without chemotherapeutic agent. At the end of the study, final tumor volume measurements will be taken and data analyzed using appropriate statistical tests; endpoint: tumor growth inhibition (regression). 
     Alternatively, animals are pre-treated with antibody prior to cell implantation, and the relative inhibition of tumor growth is measured compared to vehicle control. 
     Similarly, PRLR antibody can be tested in lung cancer models or other cancer models. Suitable models are reported in, e.g., Pukac et al.,  Br. J. Cancer  92:1430-1441 (2005). 
     All publications, patents and patent applications cited in this specification are herein incorporated by reference as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. 
     It will be understood that the invention has been described by way of example only and modifications may be made whilst remaining within the scope and spirit of the invention.