Patent Publication Number: US-2005132427-A1

Title: Animal model for the analysis of tumor metastasis

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This is a non-provisional application filed under 37 CFR 1.53(b), claiming priority under USC Section 119(e) to provisional Application No. 60/487,044, filed Jul 10, 2003. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention concerns a transgenic animal model for the analysis of tumor metastasis. In particular, the present invention provides methods for the study of tumor metastasis, including the analysis of metastasis of cancer, in a transgenic (including knock out) rodent, such as mouse model.  
      2. Related Art  
      Immunodeficient mice, such as athymic nude mice, C.B-17/severe combined immunodeficiency (scid) mice and NOD/SCID mice have been widely used as animal models in cancer metastasis research (Bruns et al.,  Int. J. Cancer  10:102(2):101-8 (2002); Ohta et al.,  Jpn. J. Cancer Chemother.  23:1669-72 (1996); Jimenez et al.,  Ann. Surg.  231:644-54 (2000)). Thus, such mouse models have been used for preclinical testing of new cancer drugs and for the detection of metastasis related genes (Bruns et al., supra; Ohta et al., supra; Jimenez et al. supra; Hotz et al.,  Pancreas  26:E89-98 (2003); Tarbe et al.,  Anticancer Res.  21:3221-8 (2001)). However, the use of these models for studying the metastases of human cancer cells has so far been limited, primarily due to the low efficiency of the incidence of cancer metastasis in the recipient mice, and the large cell number required to achieve the desired results.  
      Recently, to establish a more efficient animal recipient for xenotransplantation, a novel immunodeficiency mouse, NOD/SCID/γ c   null  (also referred to as NOD/ShiJic-scid with γ c   null , or NOG) has been developed. NOG transgenic mice have been described as an excellent recipient mouse model for engraftment of human cells (Ito et al.,  Blood  100:3175-82 (2002)), and for the study of the in vivo development of human T cells from CD34(+) cells (Saito et al.,  Int. Immunol.  14:1113-24 (2002)). When human cord blood stem cells (CBSC) were preserved in NOG mice, CBSC were differentiated to T lymphocytes and migrated to the peripheral lymphoid organs (Yahata et al.,  J. Immunol.  169:204-9 (2002)).  
      Metastasis, including hepatic metastasis, is often observed in human cancer, including pancreatic cancer even in early stage, cancers of the digestive tract, including colorectal cancer and gastrointestinal cancer, lung cancer, and the like, and is one of the most frequent causes of cancer deaths. New strategies are necessary to manage cancer metastases, which, in turn, require the availability of appropriate and efficient animal models. Accordingly, there is a great unmet need for reliable animal models that enable the study of metastasis.  
     SUMMARY OF THE INVENTION  
      In one aspect, the present invention concerns a method for testing tumor metastasis, comprising the steps of 
          (a) inoculating a tumor cell from a metastatic tumor or tumor cell line into a NOD/SCID/γ c   null  animal, such as rodent, preferably mouse, and     (b) monitoring the development of tumor metastasis.        

      In one embodiment, the tumor is cancer, such as, for example, pancreatic cancer, prostate cancer, breast cancer, colorectal cancer, gastrointestinal cancer, colon cancer, lung cancer, hepatocellular cancer, cervical cancer, ovarian cancer, liver cancer, bladder cancer, cancer of the urinary tract, thyroid cancer, renal cancer, carcinoma, melanoma, or brain cancer.  
      In another embodiment, the metastasis is hepatic, bone, brain or lung metastasis, in particular, hepatic metastasis.  
      In yet another embodiment, the tumor cell is from a metastatic tumor cell line, which can, for example, be a strongly, moderately or lightly metastatic tumor cell line.  
      Pancreatic cancer cell lines suitable for the present invention include, for example, MIAPaCa-2, AsPC-1, PANC-1, Capan-1, and BxPC-3.  
      Inoculation can be performed, for example, by portal vein injection.  
      In one embodiment, at least about 1×10 2  cells are inoculated, without any other pretreatment including irradiation or cytokine-medication.  
      In another embodiment, at least about 1×10 3  cells are inoculated.  
      In yet another embodiment, at least about 1×10 4  cells are inoculated.  
      The development of tumor metastasis can be monitored by methods known in the art, such as by observing the appearance and number of the metastatic nodules formed.  
      In another aspect, the invention concerns a method for testing a candidate anti-metastasis compound, comprising 
          (a) administering said candidate compound to a NOD/SCID/γ c   null  animal, such as a rodent, e.g. a mouse which has developed tumor metastasis, and     (b) monitoring the effect of said candidate compound on said tumor metastasis.        

      The test compound can be any kind of molecule, including, without limitation, a peptide, polypeptide, antibody or a non-peptide small molecule.  
      In a further aspect, the invention concerns a method comprising: 
          (a) introducing into a NOD/SCID/γ c   null  animal, including rodent, such as a mouse a foreign gene, and     (b) monitoring the expression of the foreign gene in the animal.        

      The foreign gene be introduced into the animal, e.g. mouse by any method of gene transfer, including, without limitation, by a viral vector.  
      In a particular embodiment, the foreign gene is a gene which is differentially expressed in tumor metastasis, such as hepatic metastasis.  
      If the hepatic metastasis is metastasis of pancreatic cancer, the gene can, for example, be selected from TIS1 1B protein; prostate differentiation factor (PDF); glycoproteins hormone α-subunit; thrombopoietin (THPO); manic fringe homology (MFNG); complement component 5 (C5); jagged homolog 1 (JAG1); interleukin enhancer-binding factor (ILF); PCAF-associated factor 65 alpha; interleukin-12 α-subunit (IL-12-α); nuclear respiratory factor 1 (NRF1); stem cell factor (SCF); transcription factor repressor protein (PRDI-BF1); small inducible cytokine subfamily A member 1 (SCYA1). transducin β2 subunit; X-ray repair complementing defective repair in Chinese hamster cells 1; putative renal organic anion transporter 1; G1/S-specific cyclin E (CCNE); retinoic acid receptor-γ (RARG); S-100 calcium-binding protein A1; neutral amino acid transporter A (SATT); dopachrome tautomerase; ets transcription factor (NERF2); calcium-activated potassium channel β-subunit; CD27BP; keratin 10; 6-O-methylguanine-DNA-methyltransferase (MGMT); xeroderma pigmentosum group A complementing protein (XPA); CDC6-related protein; cell division protein kinase 4; nociceptin receptor; cytochrome P450 XXVIIB1; N-myc proto-oncogene; solute carrier family member 1 (SLC2A1); membrane-associated kinase myt1; casper, a FADD- and caspase-related inducer of apoptosis; and C-src proto-oncogene.  
      In a particular embodiment, the animal, e.g. mouse carrying a gene marker of tumor metastasis is treated with a candidate anti-metastasis compound, and the expression level of the gene marker or its expression product as a result of the treatment is monitored.  
      In a different aspect, the invention concerns an array comprising at least one gene, or its expression product, selected from the group consisting of TIS1 1B protein; prostate differentiation factor (PDF); glycoproteins hormone α-subunit; thrombopoietin (THPO); manic fringe homology (MFNG); complement component 5 (C5); jagged homolog 1 (JAG1); interleukin enhancer-binding factor (ILF); PCAF-associated factor 65 alpha; interleukin-12 α-subunit (IL-12-α); nuclear respiratory factor 1 (NRF1); stem cell factor (SCF); transcription factor repressor protein (PRDI-BF1); small inducible cytokine subfamily A member 1 (SCYA1), transducin β2 subunit; X-ray repair complementing defective repair in Chinese hamster cells 1; putative renal organic anion transporter 1; G1/S-specific cyclin E (CCNE); retinoic acid receptor-γ (RARG); S-100 calcium-binding protein A1; neutral amino acid transporter A (SATT); dopachrome tautomerase; ets transcription factor (NERF2); calcium-activated potassium channel β-subunit; CD27BP; keratin 10; 6-O-methylguanine-DNA-methyltransferase (MGMT); xeroderma pigmentosum group A complementing protein (XPA); CDC6-related protein; cell division protein kinase 4; nociceptin receptor; cytochrome P450 XXVIIB1; N-myc proto-oncogene; solute carrier family member 1 (SLC2A1); membrane-associated kinase myt1; casper, a FADD- and caspase-related inducer of apoptosis; and C-src proto-oncogene, immobilized on a solid support.  
      In various embodiments, the array displays at least 2, or at least 5, or at least 10, or at least 15, or at least 20, or at least 25 of the listed genes, or their expression products. In another embodiments, all genes that are overexpressed in tumor metastasis, or their expression products, are displayed.  
      In another embodiment, all genes that are underexpressed in tumor metastasis, or their expression products, are displayed.  
      In yet another aspect, the invention concerns a method for predicting the likelihood of tumor metastasis in a subject comprising 
          (a) determining the expression level of one or more RNA transcripts or their expression products in a biological sample comprising cancer cells obtained from said subject, wherein the RNA transcript is selected from the group consisting of TIS1 1B protein; prostate differentiation factor (PDF); glycoproteins hormone α-subunit; thrombopoietin (THPO); manic fringe homology (MFNG); complement component 5 (C5); jagged homolog 1 (JAG1); interleukin enhancer-binding factor (ILF); PCAF-associated factor 65 alpha; interleukin-12 α-subunit (IL-12-α); nuclear respiratory factor 1 (NRF1); stem cell factor (SCF); transcription factor repressor protein (PRDI-BF1); small inducible cytokine subfamily A member 1 (SCYA1), transducin β2 subunit; X-ray repair complementing defective repair in Chinese hamster cells 1; putative renal organic anion transporter 1; G1/S-specific cyclin E (CCNE); retinoic acid receptor-γ (RARG); S-100 calcium-binding protein A1; neutral amino acid transporter A (SATT); dopachrome tautomerase; ets transcription factor (NERF2); calcium-activated potassium channel β-subunit; CD27BP; keratin 10; 6-O-methylguanine-DNA-methyltransferase (MGMT); xeroderma pigmentosum group A complementing protein (XPA); CDC6-related protein; cell division protein kinase 4; nociceptin receptor; cytochrome P450 XXVIIB1; N-myc proto-oncogene; solute carrier family member 1 (SLC2A1); membrane-associated kinase myt1; casper, a FADD- and caspase-related inducer of apoptosis; and C-src proto-oncogene; and     (b) predicting an increased likelihood of metastasis, if one or more of said genes show an increased level of expression relative to the expression level to a corresponding normal cell of the same cell type.        

      The subject is preferably a human patient, and the biological sample preferably is a tumor sample obtained by standard procedure, such as, for example, biopsy. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A  and B illustrate the incidences of hepatic metastasis and the number of liver foci in NOG mice following the inoculation of 1×10 4,  1×10 3  and 1×10 2  cells of the indicated pancreatic adenocarcinoma cells lines (MIAPaCa-2, AsPC-1, PANC-1, Capan-1, and BxPC-3.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      A. Definitions  
      Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Singleton et al.,  Dictionary of Microbiology and Molecular Biology  2 nd ed.,  J. Wiley &amp; Sons (New York, N.Y. 1994), provide one skilled in the art with a general guide to many of the terms used in the present application.  
      One skilled in the art will recognize many methods and materials similar or equivalent to those described herein, which could be used in the practice of the present invention. Indeed, the present invention is in no way limited to the methods and materials described. For purposes of the present invention, the following terms are defined below.  
      The term “tumor,” as used herein, refers to all neoplastic cell growth and proliferation, whether malignant or benign, and all pre-cancerous and cancerous cells and tissues.  
      The terms “cancer” and “cancerous” refer to or describe the physiological condition in mammals that is typically characterized by unregulated cell growth. Examples of cancer include but are not limited to, pancreatic cancer, prostate cancer, breast cancer, colorectal cancer, gastrointestinal cancer, colon cancer, lung cancer, hepatocellular cancer, cervical cancer, ovarian cancer, liver cancer, bladder cancer, cancer of the urinary tract, thyroid cancer, renal cancer, carcinoma, melanoma, and brain cancer.  
      The term “metastasis” is used herein in the broadest sense and refers to the spread of tumor, e.g. cancer from one part of the body to another. Tumors formed from cells that have spread are called secondary tumors, and contain the same type of cells as the original (primary) tumor. Thus prostate cancer that has metastasized to liver or bone is not liver or bone cancer, rather metastasized prostate cancer, as it still contains prostate cancer cells, regardless of their location.  
      The “pathology” of cancer includes all phenomena that compromise the well-being of the patient. This includes, without limitation, abnormal or uncontrollable cell growth, metastasis, interference with the normal fuinctioning of neighboring cells, release of cytokines or other secretory products at abnormal levels, suppression or aggravation of inflammatory or immunological response, neoplasia, premalignancy, malignancy, invasion of surrounding or distant tissues or organs, such as lymph nodes, etc.  
      The terms “differentially expressed gene,” “differential gene expression” and their synonyms, which are used interchangeably, refer to a gene whose expression is at a higher or lower level in one cell or cell type relative to another, or one patient or test subject relative to another. Thus, for example, differential gene expression can occur in normal cell/tissue/patient relative to a corresponding diseased cell/tissue/patient, or can reflect differences is gene expression pattern between different cell types or cells in different stages of development. The terms also include genes whose expression is activated to a higher or lower level at different stages of the same disease. It is also understood that a differentially expressed gene may be either activated or inhibited at the nucleic acid level or protein level, or may be subject to alternative splicing to result in a different polypeptide product. Such differences may, for example, be evidenced by a change in mRNA levels, surface expression, or secretion or other partitioning of a polypeptide. Differential gene expression may include a comparison of expression between two or more genes or their gene products, or a comparison of the ratios of the expression between two or more genes or their gene products, or a comparison of two differently processed products of the same gene. For the purpose of the present invention, “differential gene expression” is considered to be present when there is at least an about 2-fold, preferably at least about 2.5-fold, more preferably at least about 4-fold, even more preferably at least about 6-fold, most preferably at least about 10-fold difference between the expression of a given gene or gene product between the samples compared.  
      The term “microarray” refers to an ordered arrangement of hybridizable array elements on a substrate. The term specifically includes polynucleotide microarrays, such as cDNA and oligonucleotide microarrays, and protein arrays. In a particular embodiment, a microarray is an array of thousands of individual gene (DNA) sequences immobilized in a known order on a solid support. RNAs from different tissues are hybridized to the DNA on the chips. An RNA molecule will only bind to the DNA from which it was expressed. As a result, the relative expression of thousands of genes in biological samples (e.g. normal and diseased tissue, tissue treated or untreated with a certain drug, etc.) can be compared in a single assay. In a similar protein sequences can be displayed on a microarray chip and used to study protein-protein interactions, or differences in protein levels in different biological samples, e.g. tissues.  
      The term “polynucleotide,” generally refers to any polyribonucleotide or polydeoxribonucleotide, which may be unmodified RNA or DNA or modified RNA or DNA. Thus, for instance, polynucleotides as defined herein include, without limitation, single- and double-stranded DNA, DNA including single- and double-stranded regions, single- and double-stranded RNA, and RNA including single- and double-stranded regions, hybrid molecules comprising DNA and RNA that may be single-stranded or, more typically, double-stranded or include single- and double-stranded regions. In addition, the term “polynucleotide” as used herein includes triple-stranded regions comprising RNA or DNA or both RNA and DNA. The strands in such regions may be from the same molecule or from different molecules. The term includes DNAs (including cDNAs) and RNAs that contain one or more modified bases. Thus, DNAs or RNAs with backbones modified for stability or for other reasons are “polynucleotides” as that term is intended herein. Moreover, DNAs or RNAs comprising unusual bases, such as inosine, or modified bases, such as tritiated bases, are included within the term “polynucleotides” as defined herein. In general, the term “polynucleotide” embraces all chemically, enzymatically and/or metabolically modified forms of unmodified polynucleotides, as well as the chemical forms of DNA and RNA characteristic of viruses and cells, including simple and complex cells.  
      The term “oligonucleotide” refers to a relatively short polynucleotide, including, without limitation, single-stranded deoxyribonucleotides, single- or double-stranded ribonucleotides, RNA:DNA hybrids and double-stranded DNAs.  
      The terms “transgenic animal” and “transgenic mouse” as well we their grammatical equivalents, are used to refer to animals/mice deliberately produced to carry a gene from another animal. Transgenic animals specifically include transgenic rodents, such as, for example, mice, rats, guinea pigs, and the like.  
      The term “xenotransplantation” is used in the broadest sense and refers to the transfer of living cells, tissues or organs from one animal species into another, including humans.  
      B. Detailed Description  
      The practice of the present invention will employ, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, and biochemistry, which are within the skill of the art. Such techniques are explained fully in the literature, such as, “Molecular Cloning: A Laboratory Manual”, 2 nd  edition (Sambrook et al., 1989); “Oligonucleotide Synthesis” (M. J. Gait, ed., 1984); “Animal Cell Culture” (R. I. Freshney, ed., 1987); “Methods in Enzymology” (Academic Press, Inc.); “Handbook of Experimental Immunology”, 4 th  edition (D. M. Weir &amp; C. C. Blackwell, eds., Blackwell Science Inc., 1987); “Gene Transfer Vectors for Mammalian Cells” (J. M. Miller &amp; M. P. Calos, eds., 1987); “Current Protocols in Molecular Biology” (F. M. Ausubel et al., eds., 1987); “Transgenic Mouse: Methods and Protocols” (Methods in Molecular Biology, Clifton N.J., Vol. 209, M. H. Hofker et al., eds.).  
      The present invention provides a sensitive and reliable transgenic animal model for the study of tumor metastasis. In particular, the present invention provides a reproducible mouse model of hepatic metastasis, which involves the introduction of mammalian (e.g. human) cancer cells into NOG mice.  
      NOG mice were developed at the Central Institute for Experimental Animals (CIEA, Kawasaki, Japan), and are also described in co-pending U.S. application Ser. No. 10/221,549 filed on Oct. 25, 2001, the entire disclosure of which is hereby expressly incorporated by reference.  
      In brief, to establish an improved animal recipient for xenotransplantation, NOD/SCID/γ c   null  (NOG) mice double homozygous for the severe combined immunodeficiency (SCID) mutation and interleukin-2Rγ (IL-2Rγ) allelic mutation (γ c   null ) were generated by 8 backcross matings of C57BL/6J-γ c   null  mice and NOD/Shi-scid mice. When human CD34+ cells from umbilical cord blood were transplanted into this strain, the engraftment rate in the peripheral circulation, spleen, and bone marrow were significantly higher than that in NOD/Shi-scid mice treated with anti-asialo GM1 antibody or in the β2-microglobulin-deficient. NOD/LtSz-scid (NOD/SCID/β 2m   null ) mice, which were as completely defective in NK cell activity as NOD/SCID/γ c   null  mice. The same high engraftment rate of human mature cells was observed in ascites when peripheral blood mononuclear cells were intraperitoneally transferred. In addition to the high engraftment rate, multilineage cell differentiation was also observed. Further, even 1×10(2) CD34+ cells could grow and differentiate in this strain. Based on these results, the NOD/SCID/γ c   null  mice were described to be superior animal recipients for xenotransplantation, especially for human stem cell assays. For further details see, e.g. Hiramatsu et al.,  Blood  100:3175-82 (2002).  
      It has now been found that the NOG mice are a superior mouse model for the study of human cancer metastasis. As such, this model can be used, for example, to screen and evaluate anti-cancer drugs and anti-metastasis drug candidates, and for the detection/screening of genes related to cancer metastasis, which, in turn, find utility in the diagnosis and/or treatment of metastatic cancer, and related conditions, including gene therapy treatment of metastatic cancer.  
      The mouse model of the present invention is suitable for modeling and studying any kind of metastasis, including hepatic, bone, brain, and lung metastasis. Metastasis occurs in all types of cancers, including, without limitation, pancreatic cancer, prostate cancer, breast cancer, colorectal cancer, gastrointestinal cancer, colon cancer, lung cancer, hepatocellular cancer, cervical cancer, ovarian cancer, liver cancer, bladder cancer, cancer of the urinary tract, thyroid cancer, renal cancer, carcinoma, melanoma, and brain cancer. Although the invention will be illustrated by analyzing hepatic metastasis of human pancreatic cancer, it is not so limited. The NOG mouse model can also be used to study metastases originating from other types of cancer at any location, including liver, bone, brain and liver.  
      Methods of xenotransplantation are well known in the art and are illustrated in Example 1 below. Typically, cancer cells are transplanted into mice via tail vein injection, with or without prior immune-suppression, such as a sublethal dose of whole body irradiation and/or the administration of an immunosuppressant. For study of hepatic metastases, the cancer cells may be introduced into the animals by intrasplenic (portal vein) injection using an appropriate indwelling catheter. Pulmonary metastasis can be established, for example, by intravenous injection of tumor cells into the recipient animals, for example as described in Worth and Kleinerman;  Clin Exp. Metastasis  17:501-6 (1999). The tumor cells may originate from tumor (cancer) cell lines, and from primary tumors (e.g. cancer) obtained from human or non-human subjects.  
      To study bone metastasis, macroscopic fragments of human fetal bone or mouse bone, may be implanted into NOG mice. A few weeks later, human tumor (cancer) cell lines or cells of primary tumors (cancer) can be injected either intravenously (colonization assay), or directly into the implanted tissue fragments. Tumor metastasis can be monitored by methods known in the art, including various imaging techniques and histologic examination.  
      When used for drug screening, following the engraftment of xenogenic tumor cells (either from cell lines or from primary tumors), the NOG mice that have developed metastatic cancer can be treated with the test compound(s), and any change in the number, size or other properties of the metastatic nodules as a result of drug treatment, and the viability of the test animals are monitored relative to untreated and/or positive control, where the positive control typically is an animal treated with a know anti-metastatic compound. The administration of the test compounds can be performed by any suitable route, including, for example, oral, transdermal, intravenous, infusion, intramuscular, etc. administration. Results obtained in this model can then be validated by follow-up pharmacokinetic, toxicologic, biochemical and immunologic studies, and ultimately human clinical studies.  
      The NOG mouse model can also be used to study targeted gene delivery to metastatic nodules in vivo, for example by portal vein infusion of a retroviral vector. In particular, this NOG model can be used to study the feasibility of gene transfer to target tumor metastasis, to monitor the duration and level of gene expression and the degree of therapeutic effect, to optimize the dosing regimen and/or mode of administration, to study the dissemination of the gene transfer vector to non-targeted tissues (which provides information about potential toxicity), and the like.  
      Gene delivery most commonly is performed using retroviral vectors by techniques well known in the art. Retroviruses are enveloped viruses containing a single stranded RNA molecule as their genome. Following infection, the viral genome is reverse transcribed into double stranded DNA, which integrates into the host genome where it is expressed. The viral genome contains at least three genes: gag (coding for core proteins), pol (coding for reverse transcriptase) and env (coding for the viral envelope protein). At each end of the genome are long terminal repeats (LTRs) which include promoter/enhancer regions and sequences involved with viral integration. In addition there are sequences required for packaging the viral DNA and RNA splice sites in the env gene. Retroviral vectors used in mouse models are most frequently based upon the Moloney murine leukemia virus (Mo-MLV). In addition, lentiviruses can, for example, be used for gene transfer into experimental animals, such as NOG mice.  
      Gene delivery can also be performed by adenoviral vectors. Adenoviroses are non-enveloped, icosahedral viruses with linear double-stranded DNA genomes. Adenoviruses infect non-dividing cells by interacting with cell surface receptors, and enter cells by endocytosis. Since the genome of adenoviruses cannot integrate with the host cell genome, the expression from adenoviral vectors is transient.  
      Further details of the invention are illustrated by the following non-limiting examples.  
     EXAMPLE 1  
     Study of Hepatic Metastasis of Human Pancreatic Cancer  
      Materials and Methods  
      Male NOG mice and NOD/shiJic-scid mice of 7-9 weeks, which had been obtained from the Central Institute for Experimental Animals (CIEA, Kawasaki, Japan), were used in this study. The animals were kept under specific pathogen-free conditions according to the Guideline for the Regulation of Animal Experimentation of CIEA. All human pancreatic cancer cell lines used in this study were obtained from the American Type Culture Collection (Rockville, Md., USA). Culture media for AsPC-1 and Capan-1 were Dulbecco&#39;s modified Eagle&#39;s medium (DMEM) supplemented with 20% and 15% fetal bovine serum (FBS, Hyclone), respectively. MIAPaCa-2 and PANC-1 were maintained a culture of DMEM supplemented with 10% FBS. BxPC-3, Capan-2 and PL45 were maintained a culture of RPMI1640 (SIGMA, Cat. No. D6046 or D5796) supplemented with 10% FBS. These were maintained at 37° C. in humidified atmosphere with 5% CO2. Experimental liver metastases were generated by intrasplenic/portal injection of cancer cells, as described previously (Khatib et al.,  Cancer Res.  62:242-50 (2002)). The animals were sacrificed 6-8 weeks later and liver metastases were enumerated immediately, without prior fixation. The metastatic lesions were evaluated on the following scale: O=No metastatic lesion; 1=1-10 metastatic lesions; 2=11-20 metastatic lesions; 3=21 or more metastatic lesions.  
      Results  
      The incidences of hepatic metastases and the number of liver foci in NOG mice were far higher than those in NOD/SCID mice (Table 1 &amp;  FIGS. 1A  and B). When the mice were inoculated with 1×10 4  cells and sacrificed 6 weeks later, the incidences of hepatic metastases in NOG mice were as follows: 
          MIAPaCa-2, AsPC-1 and PANC-1 100%;     Capan-1 90%,     BxPC-3 12.5%; and     PL45 and Capan-2 0%.        

      In addition, metastases were apparent in 50-80% of NOG mice when 1×10 3  MIAPaCa-2, AsPC-1, PANC-1 and Capan-1 cells were inoculated, and even when 1×10 2  MIAPaCa-2, AsPC-1 and PANC-1 cancer cells were inoculated, 37.5-71.4% of NOG mice show hepatic metastasis. These data indicate that the hepatic metastatic lesions in NOG mice inoculated with human pancreatic cancer cell lines were reproducibly formed in a dose dependent manner.  
      Typical macroscopic views of liver metastases in NOG mice and in NOD/SCID mice are shown in  FIG. 1A . The NOG mice injected with MIAPaCa-2, AsPC-1, PANC-1, Capan-1 and BxPC-3 cells showed multiple round metastases in the liver. However, the numbers of foci in these cell lines were wildly different depending on each cell line. Five out of 7 pancreatic cancer cell lines showed the metastatic potentials in NOG mouse, in contrast, no NOD/SCID mice showed hepatic metastasis under similar conditions, except for AsPC-1. As shown in  FIGS. 1A  and B, AsPC-1 showed the metastatic potentials in both mice lines, however, the degree of metastases in NOG mice were more severe than those in NOD/SCID mice.  
      Kusama et al. ( Gastroenterology  122:308-17 (2002)) reported that metastatic lesions were apparent in 100% of athymic nude mice injected with 1×10 6  AsPC-1 cells. These findings suggest AsPC-1 may be one of the cells with high metastatic potential, where the potential is dependent on the cell numbers injected.  
      The metastatic incidences of NOG mice inoculated with Capan-1 or BxPC-3 were faded away with decreasing the number of inoculating cells. In contrast, metastatic incidences were apparent in more than 50% of NOG mice inoculated with MIAPaCa-2 or AsPC-1 even when NOG mice were inoculated with only 1×10 2  cells (Table-1). These findings clearly indicate that NOG mice represent a highly superior metastasis model relative to other immunodeficient mouse models, and in particular NOD/SCID mice.  
      Most previous publications concerning hepatic metastases of human pancreatic cancer cells using nude mice report the intrasplenal inoculation of more than one million cancer cells (Shishido et al.,  Surg. Today  29(6):519-25 (1999); Nomura et al.,  Clin. Exp. Metastasis  19:391-9 (2002); and Ikeda et al.,  Jpn. J. Cancer Res.  81:987-93 (1990)). There are few reports of 100% metastatic incidences, unless high metastatic clones derived from those cells lines were established. However, it is unlikely that more than 1 million cancer cells enter the liver at a stretch via the portal vein and form metastatic foci in pancreatic cancer patients, therefore, the current metastatic animal models are not representative of a typical human clinical situation.  
      In contrast, NOG mice represent an effective cancer metastasis model, which properly reflects the clinical conditions and behavior of human pancreatic cancer. Accordingly, the well-organized and reproducible hepatic metastases seen in NOG mice are useful in the study of hepatic metastasis of human pancreatic cancer and are expected to become the preferred model for screening and developing new anti-metastasis drugs.  
      It was reported that the murine NK activity were compensatory very high in immunodeficient animals such as nude, SCID and NOD/SCID mice, and contributed to the low rate of tumor growth and cancer metastasis (Shpitz et al.,  Anticancer Res.  14(5A):1927-34 (1994)). In contrast, Ito et al. ( Blood  100:3221-8 (2001)) reported that NOG mice have no T, B and NK cells and decrease macrophage functions and dendritic cells functions. It is suggested that in the metastasis model using NOG mice, the metastatic potentials of cancer cells are detected without complex effects upon the immune system of the host, especially NK activity.  
     Conclusions  
      The data presented demonstrate that the NOD/SCID/γ c   null  mouse model has a high potential to engraft xenogenic cells. Using this model for intrasplenic (portal vein) injection of cancer cells, reliable hepatic metastasis behavior of human pancreatic cells was observed. Four out of seven cell lines showed high hepatic metastatic potential (&gt;80% incidence), and three of the cell lines studied showed low metastatic potential (&lt;20% incidence) in NOG mice 6 weeks after transplantation only with 1×10 4  cells. Moreover, hepatic metastases were apparent in NOG mice even when 1×10 2  cells of high metastatic cell lines were inoculated. Thus, the metastatic ability of cancer cells was demonstrated with a wide range of inoculated cell number, extending through 3 logarithmic orders of magnitude. The results also show that the NOG mouse model is clearly superior over the NOD/SCID model, which is currently considered the optimal animal model for study of cancer metastasis.  
     EXAMPLE 2  
     Detection of Cancer Metastasis Related Genes in cDNA Microarray  
     Materials and Methods  
      Human pancreatic tumor cell lines, MIAPaCa-2, Panc1, Capan2 and PL45 (available from ATCC) were cultured according to the method described in Example 1. Total RNA was extracted from confluent culture of those cells using TRIZOL reagent (GIBCO BRL). Cy-3 labeled cDNA probes were synthesized from 20 μG of total RNA using Atlas human 1K specific primer set (BD), PowerScript labeling kit (BD), and Cy-3 fluorochrome (Amersham). Then, the probe was hybridized to the Atlas Glass Human 1.0 Microarray (BD) according to manufacturer&#39;s instructions.  
      The differentially expressed genes among the pancreatic tumor cell lines were globally searched using the Atlas Glass Human 1.0 Microarray (BD). The Cy-3 labeled signals were detected and obtained and analyzed the corresponding images by aGM418 array scanner (Takara). The data processing was carried out using Imagene Version 5.5 software. In this experiment, we classified human pancreatic tumor cell lines into two groups based on their metastatic potential. MIAPaCa-2 and Panc1 cell lines were classified into a highly metastatic group, while the other cell lines, Capan2 and PL45, were classified into a non-metastatic group. To compare the expression profiles, the average of the signal values from the “highly metastatic group” array was divided by the average of the signal values from the “non-metastatic group” array. The resulting values are referred to as “gene expression levels”, where a 10-fold difference and higher values were considered significant.  
     Results  
      Gene expression profiles of each cell line were recorded in an EXCEL file (ArrayData.xc1). The genes that were over-expressed in the highly metastatic cell lines (MIAPaCa-2 and Panc1) relative to the non-metastatic cell lines (Capan2 and PL45), and genes that were under-expressed in the highly metastatic cell lines relative to the non-metastatic cell lines are listed in Table 2. For example, butyrate response factor 1 gene (BRF1) was expressed over 100,000 times more in cancer cells in the highly metastatic group than in cells in the non-metastatic group. In contrast, over 100,000 times over-expression of transducing-beta-2 subunit gene was seen in cells of the non-metastatic group.  
      As shown in Table 2, the following genes are significantly over-expressed in highly metastatic cells relative to non-metastatic cells: TIS1 1B protein; prostate differentiation factor (PDF); glycoproteins hormone α-subunit; thrombopoietin (THPO); manic fringe homology (MFNG); complement component 5 (C5); jagged homolog 1 (JAG1); interleukin enhancer-binding factor (ILF); PCAF-associated factor 65 alpha; interleukin-12 α-subunit (IL-12-α); nuclear respiratory factor 1 (NRF1); stem cell factor (SCF); transcription factor repressor protein (PRDI-BF1); and small inducible cytokine subfamily A member 1 (SCYA1).  
      As shown in Table 2, the following genes are significantly under-expressed in highly metastatic cells relative to non-metastatic cells: transducin β2 subunit; X-ray repair complementing defective repair in Chinese hamster cells 1; putative renal organic anion transporter 1; G1/S-specific cyclin E (CCNE); retinoic acid receptor-γ (RARG); S-100 calcium-binding protein A1; neutral amino acid transporter A (SATT); dopachrome tautomerase; ets transcription factor (NERF2); calcium-activated potassium channel β-subunit; CD27BP; keratin 10; 6-O-methylguanine-DNA-methyltransferase (MGMT); xeroderma pigmentosum group A complementing protein (XPA); CDC6-related protein; cell division protein kinase 4; nociceptin receptor; cytochrome P450 XXVIIB1; N-myc proto-oncogene; solute carrier family member 1 (SLC2A1); membrane-associated kinase myt1; casper, a FADD- and caspase-related inducer of apoptosis; and C-src proto-oncogene.  
      The differential expression of the listed and other genes can be used, for example, in drug screening, to test anti-cancer and/or anti-metastatic drug candidates, and for diagnostic and therapeutic purposes, e.g. using gene transfer approaches.  
      All references cited herein are hereby expressly incorporated by reference in their entirety.  
      While the present invention is illustrated by way of certain embodiments, it is not so limited. One skilled in the art will understand that various modifications are possible without substantially changing the operation of the invention. Thus, for example, the mouse model described herein can be replaced by other, equivalent animals models, in particular rodent, e.g. rat, models. All such modifications are intended to be within the scope of the invention.  
                                   TABLE 1                               Cell dose   Autopsy   No. of mice with metastasis/   Incidence       Cell line   Mice   (cells/head)   (week)   total no. of mice (h)   (%)                                                        MIA PaCa-2   NOG   1 × 10 4     6   10/10   100.0       pancreas; adenocarcinoma       1 × 10 3     6   5/6   83.3               1 × 10 2     8   5/7   71.4           NOD/SCID   1 × 10 4     6    1/10   10.0               1 × 10 3     6   0/7   0.0               1 × 10 2     8   0/6   0.0       AsPC-1   NOG   1 × 10 4     6   9/9   100.0       pancreas; metastatic site:       1 × 10 3     6   8/8   100.0       ascites; adenocarcinoma       1 × 10 2     8   4/7   57.1           NOD/SCID   1 × 10 4     6   8/9   88.9               1 × 10 3     6   1/8   12.5               1 × 10 2     8   0/6   0.0       PANC-1   NOG   1 × 10 4     6   8/8   100.0       pancreas; adenocarcinoma       1 × 10 3     6   6/8   75.0               1 × 10 2     8   3/8   37.5           NOD/SCID   1 × 10 4     6    0/10   0.0               1 × 10 3     6   0/6   0.0               1 × 10 2     8   0/7   0.0       Capan-1   NOG   1 × 10 4     6    9/10   90.0       pancreas; metastatic site:       1 × 10 3     6    5/10   50.0       liver; adenocarcinoma       1 × 10 2     8   0/8   0.0           NOD/SCID   1 × 10 4     6    0/10   0.0               1 × 10 3     6    0/10   0.0               1 × 10 2     8   0/6   0.0       BxPC-3   NOG   1 × 10 5     6   8/8   100.0       pancreas; adenocarcinoma       1 × 10 4     6   1/8   12.5           NOD/SCID   1 × 10 5     6   0/8   0.0               1 × 10 4     6   0/6   0.0       Capan-2   NOG   1 × 10 5     6   0/8   0.0       pancreas; adenocarcinoma       1 × 10 4     6    0/10   0.0           NOD/SCID   1 × 10 5     6   0/8   0.0       PL45   NOG   1 × 10 5     6   0/8   0.0       Ductal adenocarcinoma;       1 × 10 4     6    0/10   0.0       pancreas   NOD/SCID   1 × 10 5     6   0/8   0.0                  
 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
               
             
            
               
                 Miapaca, 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Panc1&gt;&gt;Capan2, 
               
               
                 PL45 
                 Miapaca, Panc1&gt;&gt;Capan2, PL45 
                   
                   
                 2High 
                   
                   
                 Low 
                 2H_AV- 
                 Human 
               
               
                 MRMCRC 
                 Gene Name 
                 Miapaca 
                 Panc1 
                 AVG 
                 Capan2 
                 PL45 
                 AVG 
                 LAV 
                 RNA 
               
               
                   
               
               
                 4176 
                 TIS11B protein; butyrate response factor 1 (BRF1); 
                 5.351 
                 6.311 
                 5.331 
                 0.000 
                 0.000 
                 0.000 
                 5.331 
                 0.000 
               
               
                   
                 EGF response factor 1 (E   
               
               
                 6272 
                 prostate differentiation factor (PDF); macrophage 
                 3.389 
                 3.375 
                 3.382 
                 0.000 
                 0.000 
                 0.000 
                 3.382 
                 0.000 
               
               
                   
                 inhibitory cytokine 1(MIC1);    
               
               
                 6274 
                 glycoprotein hormone alpha subunit 
                 3.821 
                 2.680 
                 3.250 
                 0.000 
                 0.000 
                 0.000 
                 3.250 
                 3.605 
               
               
                 6153 
                 thrombopoletin (THPO); megakaryocyte colony 
                 3.579 
                 2.921 
                 3.250 
                 0.000 
                 0.000 
                 0.000 
                 3.250 
                 3.265 
               
               
                   
                 stimulating factor; o-mpi ligand; 
               
               
                 6322 
                 manic  nge homolog (MFNG) 
                 3.678 
                 2.757 
                 3.167 
                 0.000 
                 0.000 
                 0.000 
                 3.167 
                 3.021 
               
               
                 8267 
                 complement component 5 (C5) 
                 3.911 
                 2.373 
                 3.142 
                 0.000 
                 0.000 
                 0.000 
                 3.142 
                 2.893 
               
               
                 6371 
                 jagged homolog 1 (JAG1; hJ1) 
                 3.913 
                 2.356 
                 3.135 
                 0.000 
                 0.000 
                 0.000 
                 3.135 
                 1.980 
               
               
                 4262 
                 interfeukin enhancer-binding factor (ILF) 
                 3.209 
                 3.029 
                 3.119 
                 0.000 
                 0.000 
                 0.000 
                 3.119 
                 0.000 
               
               
                   
                 ILF + interleukin enhancer binding fac   
               
               
                 4261 
                 PCAF-associated factor 65 alpha 
                 3.193 
                 2.989 
                 3.091 
                 0.000 
                 0.000 
                 0.000 
                 3.091 
                 2.812 
               
               
                 6227 
                 Interleukin 12 alpha subunit (IL12-alpha; IL 12A); 
                 3.376 
                 2.779 
                 3.078 
                 0.000 
                 0.000 
                 0.000 
                 3.078 
                 0.000 
               
               
                   
                 cytoloxic lymphocyte maturat   
               
               
                 4257 
                 nuclear respiratory factor 1 (NRF1); alpha 
                 2.893 
                 3.178 
                 3.035 
                 0.000 
                 0.000 
                 0.000 
                 3.035 
                 2.606 
               
               
                   
                 palindromic binding protein 
               
               
                 6154 
                 stem cell factor (SCF); mast cell growth 
                 3.497 
                 2.558 
                 3.027 
                 0.000 
                 0.000 
                 0.000 
                 3.027 
                 2.394 
               
               
                   
                 factor (MGF); c-kit ligand 
               
               
                 4251 
                 transcription repressor protein PRDI-BF1; 
                 3.233 
                 2.812 
                 3.023 
                 0.000 
                 0.000 
                 0.000 
                 3.023 
                 2.473 
               
               
                   
                 beta-interferon gene positive regular 
               
               
                 6144 
                 small inducible cytokine subfamily A 
                 3.341 
                 2.691 
                 3.016 
                 0.000 
                 0000 
                 0.000 
                 3.016 
                 0.000 
               
               
                   
                 member 1 (SCYA1); T-cell-secreated protel 
               
               
                   
               
               
                 Miapaca, 
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Panc1&lt;&lt;Capan2, 
               
               
                 PL45 
                 Miapaca, Panc1&lt;&lt;Capan2, PL45 
                   
                   
                 2High 
                   
                   
                 Low 
                 2H_AV- 
                 Human 
               
               
                 MRMCRC 
                 Gene Name 
                 Miapaca 
                 Panc1 
                 AVG 
                 Capan2 
                 PL45 
                 AVG 
                 LAV 
                 RNA 
               
               
                   
               
               
                 2327 
                 Transducin beta-2 subunit; GTP-binding protein 
                 0.000 
                 0.000 
                 0.000 
                 5.307 
                 5.170 
                 5.239 
                 −5.239 
                 4.991 
               
               
                   
                 G(l)/G(s)/G(t) beta subunit 2 
               
               
                 3366 
                 X-ray repair-complementing defective repair in 
                 0.000 
                 0.000 
                 0.000 
                 4.023 
                 3.457 
                 3.740 
                 −3.740 
                 4.468 
               
               
                   
                 Chinese hamster cells 1(XRCC 
               
               
                 1433 
                 putative renal organic anion transporter 1 (hROAT1) 
                 0.000 
                 0.000 
                 0.000 
                 3.857 
                 3.594 
                 3.726 
                 −3.726 
                 4.873 
               
               
                 1227 
                 G1/S-specific cyclin E (CCNE) 
                 0.000 
                 0.000 
                 0.000 
                 3.840 
                 3.435 
                 3.637 
                 −3.637 
                 4.686 
               
               
                 4365 
                 retinoic acid receptor gamma (RARG) 
                 0.000 
                 0.000 
                 0.000 
                 3.843 
                 3.400 
                 3.621 
                 −3.621 
                 3.678 
               
               
                 2437 
                 S100 calcium-binding protein A1; S-100 protein 
                 0.000 
                 0.000 
                 0.000 
                 3.769 
                 3.384 
                 3.577 
                 −3.577 
                 4.406 
               
               
                   
                 alpha chain 
               
               
                 1446 
                 neutral amino acid transporter A (SATT); alanine/ 
                 0.000 
                 0.000 
                 0.000 
                 3.373 
                 3.580 
                 3.476 
                 −3.476 
                 3.938 
               
               
                   
                 serine/cysteine/threonine tran 
               
               
                 6434 
                 dopachrome tautomerace; dopachrome delta-isomerase 
                 0.000 
                 0.000 
                 0.000 
                 3.536 
                 3.332 
                 3.434 
                 −3.434 
                 4.262 
               
               
                 4312 
                 ets transcription factor; NERF2 
                 0.000 
                 0.000 
                 0.000 
                 3.546 
                 3.301 
                 3.424 
                 −3.424 
                 2.477 
               
               
                 1443 
                 calcium-activated potassium channel beta subunit; 
                 0.000 
                 0.000 
                 0.000 
                 3.680 
                 2.944 
                 3.312 
                 −3.312 
                 4.554 
               
               
                   
                 maxi K channel beta subunit 
               
               
                 3232 
                 CD27BP (Siva) 
                 0.000 
                 0.000 
                 0.000 
                 3.365 
                 3.182 
                 3.274 
                 −3.274 
                 4.018 
               
               
                 4442 
                 keratin 10 (KRT10; K10) 
                 0.000 
                 0.000 
                 0.000 
                 3.505 
                 3.010 
                 3.257 
                 −3.257 
                 2.721 
               
               
                 3374 
                 6-O-methylguanine-DNA methyltransferase (MGMT); 
                 0.000 
                 0.000 
                 0.000 
                 3.030 
                 3.475 
                 3.252 
                 −3.252 
                 3.275 
               
               
                   
                 methylated-DNA-protein- 
               
               
                 3375 
                 xeroderma pigmentosum group A complementing 
                 0.000 
                 0.000 
                 0.000 
                 4.284 
                 2.200 
                 3.242 
                 −3.242 
                 3.592 
               
               
                   
                 protein (XPA) 
               
               
                 1347 
                 CDC6-related protein 
                 0.000 
                 0.000 
                 0.000 
                 3.390 
                 3.040 
                 3.215 
                 −3.215 
                 3.093 
               
               
                 1312 
                 cell division protein kinase 4; cyclin-dependent 
                 0.000 
                 0.000 
                 0.000 
                 3.201 
                 3.205 
                 3.203 
                 −3.203 
                 3.332 
               
               
                   
                 kinase 4 (CDK4); PSK-J3 
               
               
                 3432 
                 noclceptin receptor; orphanin FQ receptor; opioid 
                 0.000 
                 0.000 
                 0.000 
                 3.432 
                 2.967 
                 3.200 
                 −3.200 
                 4.165 
               
               
                   
                 receptor kappa 3 (OPRK3) 
               
               
                 5456 
                 cytochrome P450 XXVIIB1 (CYP27B1); 
                 0.000 
                 0.000 
                 0.000 
                 3.346 
                 3.049 
                 3.197 
                 −3.197 
                 3.856 
               
               
                   
                 25-hydroxyvitamin D-1-alpha-hydroxyl; 
               
               
                 1174 
                 N-myc proto-oncogene 
                 0.000 
                 0.000 
                 0.000 
                 3.323 
                 3.012 
                 3.167 
                 −3.167 
                 3.466 
               
               
                 1442 
                 solute carrier family 2 member 1 (SLC2A1); glucose 
                 0.000 
                 0.000 
                 0.000 
                 3.215 
                 3.059 
                 3.137 
                 −3.137 
                 4.077 
               
               
                   
                 transporter 1 (GLUT1) 
               
               
                 1324 
                 membrane-associated kinase myt1 
                 0.000 
                 0.000 
                 0.000 
                 3.869 
                 2.379 
                 3.124 
                 −3.124 
                 3.645 
               
               
                 3247 
                 caspor, a FADD- and caspase-related inducer of 
                 0.000 
                 0.000 
                 0.000 
                 3.531 
                 2.659 
                 3.095 
                 −3.095 
                 4.255 
               
               
                   
                 apoptosis (CASH-alpha + CA 
               
               
                 1241 
                 C-arc photo-oncogene (SRC1) 
                 0000 
                 0.000 
                 0.000 
                 3.316 
                 2.829 
                 3.072 
                 −3.072 
                 2.795