# Patent

## Title
SRPX for treatment of cancer

## Abstract

Methods of treating a tumor in a subject include identifying a subject having, at risk for, or suspected of having a tumor, and administering to the subject an effective amount of an SRPX.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national phase application under 35 U.S.C. §371 of PCT International Application No. PCT/US2012/055641, filed Sep. 14, 2012, which claims the benefit under 35 USC §119(e) of U.S. Provisional Application Ser. No. 61/534,655, filed on Sep. 14, 2011, the entire contents of these applications are hereby incorporated by reference.


TECHNICAL FIELD
This invention relates to treatment of cancers with agents that include a polypeptide.
BACKGROUND
Lung cancer, the leading cause of cancer-related death worldwide, will account for an estimated 157,000 deaths in the United States this year. Approximately 85 to 90% of all cases of lung cancer are non-small-cell lung cancer (NSCLC). There are three main forms of NSCLC, which are classified according to histological subtype: adenocarcinoma (accounting for 40% of lung cancers), squamous cell carcinoma (25%) and large-cell carcinomas (10%). Advanced-stage NSCLC is currently considered an incurable disease for which standard chemotherapy provides marginal improvement in overall survival at the expense of substantial morbidity and mortality. Furthermore, fewer than 30% of patients with metastatic NSCLC have a response to platinum-based chemotherapy, the most commonly used initial treatment in this stage of the disease. Although newer chemotherapeutic agents, such as bevacizumab, have been introduced, the median overall survival of patients with metastatic NSCLC remains approximately 1 year (Sandler et al., 2006, N. Engl. J. Med., 355:2542; Schiller et al., 2002, N. Engl. J. Med., 346:92), and only 3 to 4% of patients with metastatic NSCLC survive 5 years after diagnosis.
SUMMARY
This disclosure is based, in part, on the surprising discovery that, although previously believed to be active intracellularly (see, e.g., Tambe et al., Tambe et al. 2007, Carcinogenesis 28(4):777-784, especially FIG. 4B, which suggests that SRPX is localized to the endoplasmic reticulum), a secreted form of the Sushi-Repeat-containing Protein, X-linked (SRPX) protein induces senescence and/or apoptosis in cancer cells. Described herein are methods of diagnosing and treating tumors (e.g., cancers), inducing cellular apoptosis, inducing cellular senescence, and inhibiting cellular proliferation using SRPX agents, e.g., agents comprising SRPX polypeptides delivered to the extracellular surface of tumor cells, or comprising cells (e.g., autologous cells) expressing and secreting exogenous SRPX polypeptides and implanted into or near the tumor.
In one aspect, this application features methods of treating a tumor in a subject by identifying a subject having, at risk for, or suspected of having a tumor; and administering to the extracellular surface of tumor cells in the subject an effective amount of an SRPX agent, e.g., polypeptide or active fragment thereof, thereby treating the tumor. In some embodiments, the tumor is a cancer (e.g., a lung cancer (e.g., a non-small cell lung carcinoma, small-cell carcinoma, adenocarcinoma, or squamous cell carcinoma), a melanoma, carcinoma, breast cancer, ovarian cancer, pancreatic cancer, colorectal carcinoma, or papillary thyroid carcinoma). In some embodiments, the tumor comprises cells in which expression of SRPX is significantly reduced, e.g., undetectable, as compared to wild-type (normal) cells of the same tissue. In some embodiments, the methods include identifying a subject as having a tumor in which expression of SRPX is significantly reduced, e.g., by detecting expression of SRPX in a sample comprising cells from the tumor.
In another aspect, this application features methods of inducing senescence in a cell (e.g., a tumor cell or cancer cell) that include administering to the extracellular surface of the cell an effective amount of a SRPX agent, e.g., polypeptide or active fragment thereof. In some embodiments, the cell is a tumor cell.
In a further aspect, this application features methods of inducing apoptosis in a cell (e.g., a tumor cell or cancer cell) that include administering to the extracellular surface of the cell an effective amount of a SRPX agent, e.g., polypeptide or active fragment thereof.
In another aspect, this application features methods of inhibiting proliferation of a cell (e.g., a tumor cell or cancer cell) that include administering to the extracellular surface of the cell an effective amount of a SRPX agent, e.g., polypeptide or active fragment thereof.
In a further aspect, this application features methods of inhibiting growth (e.g., metastatic growth) in a subject of a tumor that include administering to the extracellular surface of cells of the tumor in the subject an effective amount of a SRPX agent, e.g., polypeptide or active fragment thereof.
In some embodiments, expression of SRPX is significantly reduced, e.g., undetectable, in the cell as compared to a wild-type (normal) cell of the same type/tissue type. In some embodiments, the methods include identifying a cell in which expression of SRPX is significantly reduced, e.g., by detecting expression of SRPX in a sample comprising cells from a tumor.
In another aspect, this application features the use of a SRPX agent in the preparation of a medicament for the treatment of a tumor or cancer (e.g., a lung cancer (e.g., a non-small cell lung carcinoma, small-cell carcinoma, adenocarcinoma, or squamous cell carcinoma), a melanoma, carcinoma, breast cancer, ovarian cancer, pancreatic cancer, colorectal carcinoma, or papillary thyroid carcinoma) in a subject. Compositions comprising a SRPX polypeptide or active fragment thereof are suitable for administration to the extracellular surface of cells in the tumor. In some embodiments, the tumor or cancer is metastatic.
In a further aspect, this application features an isolated SRPX agent for treating a tumor or cancer (e.g., a lung cancer (e.g., a non-small cell lung carcinoma, small-cell carcinoma, adenocarcinoma, or squamous cell carcinoma), a melanoma, carcinoma, breast cancer, ovarian cancer, pancreatic cancer, colorectal carcinoma, or papillary thyroid carcinoma) in a subject. Compositions comprising a SRPX polypeptide or active fragment thereof are suitable for administration to the extracellular surface of cells in the tumor. In some embodiments, the tumor or cancer is metastatic.
In some embodiments, the tumor comprises cells in which expression of SRPX is significantly reduced, e.g., undetectable, as compared to wild-type (normal) cells of the same tissue. In some embodiments, the methods include identifying a subject as having a tumor in which expression of SRPX is significantly reduced, e.g., by detecting expression of SRPX in a sample comprising cells from the tumor.
In some embodiments, the SRPX agent is a composition that includes a polypeptide having a sequence at least 80% identical (e.g., at least 85%, 90%, 95%, 98%, or 99% identical) to SEQ ID NO:1 or SEQ ID NO:2, or an active fragment of either. The polypeptide can be conjugated to a heterologous moiety (e.g., a heterologous polypeptide sequence). In some embodiments, the SRPX agent includes a functional fragment or domain of SEQ ID NO:1 or SEQ ID NO:2, or a fragment of either. The SRPX agent can be administered, e.g., topically, systemically, or locally (e.g., by a drug-releasing implant). The SRPX polypeptide is administered to the extracellular surface of cells in the tumor.
In some embodiments, the SRPX agent is administered by introducing into the subject a composition that induces the expression of SRPX or an active fragment or analog thereof, e.g., a nucleic acid encoding a polypeptide that includes a sequence at least 80% identical (e.g., at least 85%, 90%, 95%, 98%, or 99% identical) to SEQ ID NO:1 or SEQ ID NO:2, or a fragment of either. The nucleic acid can be in a vector, e.g., a viral vector (e.g., an adenovirus vector, an adeno-associated virus vector, a retrovirus vector, or a lentivirus vector). In some embodiments, the SRPX agent is administered by introducing into the subject a cell that includes a nucleic acid encoding a polypeptide that includes a sequence at least 80% identical (e.g., at least 85%, 90%, 95%, 98%, or 99% identical) to SEQ ID NO:1 or SEQ ID NO:2, or a fragment of either, and wherein the cell secretes the polypeptide.
In another aspect, the invention features methods for treating a tumor in a subject. The methods include identifying a subject having, at risk for, or suspected of having a tumor; and administering to the subject an effective amount of a population of cells expressing a nucleic acid encoding a polypeptide that is at least 95% identical to SEQ ID NO:1, wherein the cells are administered into or near the tumor, thereby treating the tumor.
An active or functional fragment is a portion of the SRPX protein that retains the ability to induce cancer cell senescence and/or apoptosis, e.g., is able to induce cancer cell death or senescence (e.g., lung cancer cell death or senescence) in a relevant assay known in the art, e.g., an assay described herein.
“Polypeptide” and “protein” are used interchangeably and mean any peptide-linked chain of amino acids, regardless of length or post-translational modification.
As used herein, a subject “at risk of developing cancer” is a subject that has a predisposition to develop cancer, i.e., a genetic or familial predisposition to develop cancer or has been exposed to conditions that can result in cancer. From the above it will be clear that subjects “at risk of developing cancer” are not all subjects.
A subject “suspected of having cancer” is one having one or more symptoms of cancer. Symptoms of cancer are well-known to those of skill in the art and include, without limitation, weight loss, weakness, excessive fatigue, difficulty eating, loss of appetite, unusual mole features, newly pigmented skin area, skin growths, skin ulcers, skin lumps, chronic cough, worsening breathlessness, breathing difficulty, enlarged lymph nodes, coughing up blood, blood in the urine, blood in stool, nausea, vomiting, liver metastases, lung metastases, bone metastases, breast or nipple changes, nipple discharge, abdominal fullness, bloating, fluid in peritoneal cavity, constipation, abdominal distension, perforation of colon, acute peritonitis (infection, fever, pain), vaginal bleeding, pain, vomiting blood, heavy sweating, fever, high blood pressure, anemia, diarrhea, jaundice, dizziness, chills, muscle spasms, colon metastases, lung metastases, bladder metastases, liver metastases, bone metastases, kidney metastases, pancreas metastases, difficulty swallowing, and the like. For example, a patient who has been diagnosed by a physician as having cancer is still suspected of having cancer.
The term “cancer” refers to cells having the capacity for autonomous growth. Examples of such cells include cells having an abnormal state or condition characterized by rapidly proliferating cell growth. The term is meant to include cancerous growths, e.g., tumors; oncogenic processes, metastatic tissues, and malignantly transformed cells, tissues, or organs, irrespective of histopathologic type or stage of invasiveness. Also included are malignancies of the various organ systems, such as respiratory, cardiovascular, renal, reproductive, hematological, neurological, hepatic, gastrointestinal, and endocrine systems; as well as adenocarcinomas which include malignancies such as most colon cancers, renal-cell carcinoma, prostate cancer and/or testicular tumors, non-small cell carcinoma of the lung, cancer of the small intestine, and cancer of the esophagus. Cancer that is “naturally arising” includes any cancer that is not experimentally induced by implantation of cancer cells into a subject, and includes, for example, spontaneously arising cancer, cancer caused by exposure of a patient to a carcinogen(s), cancer resulting from insertion of a transgenic oncogene or knockout of a tumor suppressor gene, and cancer caused by infections, e.g., viral infections. The term “carcinoma” is art recognized and refers to malignancies of epithelial or endocrine tissues. In some embodiments, the present methods can be used to treat a subject having an epithelial cancer, e.g., a solid tumor of epithelial origin, e.g., lung, breast, ovarian, prostate, renal, pancreatic, or colon cancer.
Unless otherwise defined, all 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. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.



DESCRIPTION OF DRAWINGS
FIG. 1A is a bar graph depicting relative SRPX expression in normal lung tissue and tumor samples from patients with lung adenocarcinomas and squamous cell carcinomas.
FIG. 1B is a photograph showing growth of a normal lung cell line (MRC5) and lung cancer cell lines (NCH-H23, EKVX, HOP-62, and HOP-92) grown in the presence (+) or absence (—) of rSRPX.
FIGS. 1C and 1D are line graphs depicting tumor growth in mice with tumor xenografts treated with a control vector (AAV-LacZ) or a vector expressing SRPX (AAV-SRPX).
FIGS. 1E and 1F are line graphs showing levels of alanine aminotransferase (ALT, 1E) and aspartate aminotransferase (AST, 1F) in animals administered the indicated doses of SRPX. No significant increases were seen in either ALT or AST.
FIG. 2 is a bar graph depicting relative growth of breast, colon, leukemia, lung, and melanoma cancer cell lines without treatment or treated with control conditioned media (CM) or CM containing SRPX.
FIG. 3A is a photograph showing growth of a human lung adenocarcinoma cell line (A549) treated in the presence of control CM, SRPX-containing CM or SRPX(Δ1-35)-containing CM.
FIG. 3B is a bar graph depicting the percent apoptosis, as assessed by Annexin V staining, in A549 cells transfected with a vector expressing SRPX or SRPX(Δ1-35).
FIG. 3C is an immunoblot showing expression of SRPX and SRPX(Δ1-35) in cell lysate and CM.
FIG. 4A is a plasmid map of pAAVCMVPI.SRPXsec.
FIG. 4B is a map of adeno-associated vector AAV-SRPXsec.
FIGS. 4C-4D depict the sequence of plasmid pAAVCMVPI.SRPXsec (SEQ ID NO:5), which includes an adeno associated vector (AAV) expressing the polypeptide of SEQ ID NO:1 with a heterologous signal sequence and C-terminal Myc and His6 tags.
FIG. 5A is a plasmid map of pAAVCMVPI.SRPXwt.
FIG. 5B is a map of adeno-associated vector AAV-SRPXwt.
FIGS. 5C-5D depict the sequence of plasmid pAAVCMVPI.SRPXwt (SEQ ID NO:6), which includes an AAV expressing the polypeptide of SEQ ID NO:2 with C-terminal Myc and His6 tags.



DETAILED DESCRIPTION
This disclosure includes methods of treating tumors (e.g., cancers), inducing cellular apoptosis, inducing cellular senescence, and inhibiting cellular proliferation with SRPX agents.
SRPX Agents
SRPX agents that can be used with the methods described herein are agents that include an SRPX polypeptide sequence and, alternatively, one or more polypeptide or non-polypeptide moieties, such that the agent has at least 25% (e.g., at least: 30%; 40%; 50%; 60%; 70%; 75%; 80%; 85%; 90%; 95%; 97%; 98%; 99%; 99.5%, or 100% or even greater) of the ability of rSRPX (see Example 1) to inhibit the proliferation of one or more of NCI-H23, EKVX, HOP-62, HOP-92, HCT-15, SW-620, COLO205, HT29, HCT-116, KM-12, CCRF-CEM, K-562, MOLT-4, SR, RPMI-8226, A549-ATCC, NCI-H226, NCI-H322M in vitro. Exemplary agents include fragments and analogs of SRPX (see below). The SRPX polypeptide sequence can include a mature, soluble SRPX polypeptide (e.g., SEQ ID NO:1 or residues 29, 30, 31, 32, 33, 34 or 35 to 464 of SEQ ID NO:2), one or more domains of SRPX, or fragments or variants thereof. Exemplary fragments of SRPX include residues 59 to 115, 59 to 175, 59 to 254, 59 to 317, 120 to 175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, and 262 to 317 of SEQ ID NO:2. An exemplary mature, soluble SRPX polypeptide is provided as:







(SEQ ID NO: 1)


DSPLEDDEVGYSHPRYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTR


 


CDIRCQKGYELHGSSLLICQSNKRWSDKVICKQKRCPTLAMPANGGFKC


 


VDGAYFNSRCEYYCSPGYTLKGERTVTCMDNKAWSGRPASCVDMEPPRI


 


KCPSVKERIAEPNKLTVRVSWETPEGRDTADGILTDVILKGLPPGSNFP


 


EGDHKIQYTVYDRAENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGD


 


NYGATCEFSCIGGYELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTA


 


AALLDQFYEKRRLLIVSTPTARNLLYRLQLGMLQQAQCGLDLRHITVVE


 


LVGVFPTLIGRIGAKIMPPALALQLRLLLRIPLYSFSMVLVDKHGMDKE


 


RYVSLVMPVALFNLIDTFPLRKEEMVLQAEMSQTCNT






In certain embodiments, SRPX polypeptides include sequences substantially identical to all or a portion of a naturally occurring SRPX polypeptide. Polypeptides “substantially identical” to the SRPX polypeptide sequence described herein can contain an amino acid sequence that is at least 65% (e.g., at least 75%, 80%, 85%, 90%, 95%, 98%, or 99%, e.g., 100%), identical to the amino acid sequences of the SRPX polypeptide represented by SEQ ID NO:1, an amino acid sequence of GenBank Accession No. NP—006298.1 (SEQ ID NO:2), NP—001164221.1 (residues 1 to 32 and 53 to 464 of SEQ ID NO:2), NP—001164222.1 (SEQ ID NO:7), or NP—001164223.1 (SEQ ID NO:8), or a fragment as disclosed herein (e.g., residues 29, 30, 31, 32, 33, 34, 35, or 36 to 464 of SEQ ID NO:2 or residues 59 to 115, 59 to 175, 59 to 254, 59 to 317, 120 to 175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, and 262 to 317 of SEQ ID NO:2). The human NP—006298.1 sequence is shown below.







(SEQ ID NO: 2)


MGSPAHRPALLLLLPPLLLLLLLRVPPSRSFPGSGDSPLEDDEVGYSHP


 


RYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGS


 


SLLICQSNKRWSDKVICKQKRCPTLAMPANGGFKCVDGAYFNSRCEYYC


 


SPGYTLKGERTVTCMDNKAWSGRPASCVDMEPPRIKCPSVKERIAEPNK


 


LTVRVSWETPEGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRA


 


ENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGY


 


ELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLL


 


IVSTPTARNLLYRLQLGMLQQAQCGLDLRHITVVELVGVFPTLIGRIGA


 


KIMPPALALQLRLLLRIPLYSFSMVLVDKHGMDKERYVSLVMPVALFNL


 


IDTFPLRKEEMVLQAEMSQTCNT






The human NP—001164222.1 sequence is shown below.







(SEQ ID NO: 7)


MGSPAHRPALLLLLPPLLLLLLLRVPPSRSFPGSGDSPLEDDEVGYSHP


 


RYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGS


 


SLLICQSNKRWSDKVICKHMEPPRIKCPSVKERIAEPNKLTVRVSWETP


 


EGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRAENKGTCKFRV


 


KVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGYELQGSPARVC


 


QSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLLIVSTPTARNL


 


LYRLQLGMLQQAQCGLDLRHITVVELVGVFPTLIGRIGAKIMPPALALQ


 


LRLLLRIPLYSFSMVLVDKHGMDKERYVSLVMPVALFNLIDTFPLRKEE


 


MVLQAEMSQTCNT






The human NP—001164223.1 sequence is shown below.







(SEQ ID NO: 8)


MGSPAHRPALLLLLPPLLLLLLLRVPPSRSFPGSGDSPLEDDEVGYSHP


 


RYKDTPWCSPIKVKYGDVYCRAPQGGYYKTALGTRCDIRCQKGYELHGS


 


SLLICQSNKRWSDKVICKQKRCPTLAMPANGGFKCVDGAYFNSRCEYYC


 


SPGYTLKGERTVTCMDNKAWSGRPASCVDMEPPRIKCPSVKERIAEPNK


 


LTVRVSWETPEGRDTADGILTDVILKGLPPGSNFPEGDHKIQYTVYDRA


 


ENKGTCKFRVKVRVKRCGKLNAPENGYMKCSSDGDNYGATCEFSCIGGY


 


ELQGSPARVCQSNLAWSGTEPTCAAMNVNVGVRTAAALLDQFYEKRRLL


 


IVSTPTARNLLYRLQLGMLQAVAANPTLLLQYGASG






Any of the above polypeptides can be provided in mature form without the signal sequence (e.g., residues 1 to 29, 30, 31, 32, 33, 34, or 35 of SEQ ID NO: 2, 7, or 8).
Furthermore, a SRPX polypeptide (e.g., SEQ ID NO:1, an amino acid sequence of GenBank Accession No. NP—006298.1 (SEQ ID NO:2), NP—001164221.1, NP—001164222.1, or NP—006298.1, or a fragment as disclosed herein (e.g., residues 29, 30, 31, 32, 33, 34 or 35 to 464 of SEQ ID NO:2 or residues 59 to 115, 59 to 175, 59 to 254, 59 to 317, 120 to 175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, and 262 to 317 of SEQ ID NO:2)) with up to 50, e.g., 1, 3, 5, 10, 15, 20, 25, 30, or 40, amino acid insertions, deletions, or substitutions (e.g., conservative amino acid substitutions) will be useful in the compositions and methods described herein. A “conservative amino acid substitution” is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine).
The percent identity between two amino acid sequences can be determined using the BLAST 2.0 program, which is available to the public at ncbi.nlm.nih.gov/BLAST. Sequence comparison is performed using the default parameters (BLOSUM 62 matrix, gap existence cost of 11, per residue gap cost of 1, and a lambda ratio of 0.85). The mathematical algorithm used in BLAST programs is described in Altschul et al., 1997, Nucleic Acids Research, 25:3389-3402.
SRPX polypeptides useful in the methods described herein can be, but are not limited to, recombinant polypeptides and naturally occurring polypeptides. A SRPX polypeptide can be obtained from any human or mammalian species, and include alternatively spliced forms and other isoforms that have the disclosed activities. Non-human SRPX polypeptides with similarity to human SRPX polypeptides have been identified in chimpanzees (e.g., GenBank Accession No. XP—521003.3), rhesus monkeys (e.g., GenBank Accession Nos. XP—001083979.1, XP—001084091.1), common marmosets (e.g., GenBank Accession Nos. XP—002762821.1, XP—002762820.1), Sumatran orangutans (GenBank Accession Nos. XP—002831567.1, XP—002831566.1), white-cheeked gibbons (GenBank Accession No. XP—003271118.1), cattle (e.g., GenBank Accession Nos. DAA12706.1, NP—001035579.1), horses (e.g., GenBank Accession No. XP—001489693.3), dogs (e.g., GenBank Accession No. XP—548948.3), mice (e.g., GenBank Accession Nos. CAM18748.1, NP—058607.1), and rats (e.g., GenBank Accession Nos. AAH87639.1, NP—071969.1).
Also useful in the new methods are fusion proteins in which a portion of a SRPX polypeptide is fused to an unrelated polypeptide (e.g., a marker polypeptide or purification tag) to create a fusion protein. For example, the polypeptide can be fused to a peptide tag to facilitate purification (e.g., a hexa-histidine tag or a FLAG tag to facilitate purification of bacterially expressed polypeptides or to a hemagglutinin tag or a FLAG tag to facilitate purification of polypeptides expressed in eukaryotic cells). Also useful are, for example, polypeptides that include a first portion and a second portion; the first portion includes, e.g., a SRPX polypeptide, and the second portion includes, e.g., a detectable marker or a serum protein, e.g., an immunoglobulin constant region, or human serum albumin.
SRPX contains three complement control protein (CCP) modules (aka short consensus repeats (SCRs) or SUSHI repeats; Norman et al., J. Mol. Biol., 219:717-725; Kirkitadze et al., 2001, Immunol. Rev., 180:146-161) at residues 59 to 115, 120 to 175, and 262 to 317 of SEQ ID NO:2. Additionally, the protein contains a hyaline repeat (HYR) domain at residues 175 to 254 of SEQ ID NO:2. Exemplary fragments of SRPX can include one or more of residues 59 to 115, 59 to 175, 59 to 254, 59 to 317, 120 to 175, 120 to 254, 120 to 317, 175 to 254, 175 to 317, or 262 to 317 of SEQ ID NO:2. Conserved residues and domains can be used when producing fragments, analogs, and variants of SRPX polypeptides.
A SRPX agent can have one or more chemical modifications (e.g., posttranslational modifications) at one or more sites on the polypeptide, e.g., at the amino or carboxy terminus. Methods of chemical modification are well-known to those of skill in the art, and can be used to alter one or more properties, e.g., activity, stability, retention, or pharmacokinetics of the SRPX agent. Exemplary modifications include glycosylation and PEGylation. SRPX contains a putative O-glycosylation site at residue 383 of SEQ ID NO:2. Pegylation of proteins is described in US 2006/0100144. Similar modifications and methods can be used with SRPX agents.
A SRPX agent can also be a peptidomimetic version of a SRPX polypeptide (e.g., SEQ ID NO:1), functional fragment, or variant thereof. These polypeptides can be modified according to the methods known in the art for producing peptidomimetics. See, e.g., Kazmierski, W. M., ed., Peptidomimetics Protocols, Human Press (Totowa N.J. 1998); Goodman et al., eds., Houben-Weyl Methods of Organic Chemistry: Synthesis of Peptides and Peptidomimetics, Thiele Verlag (New York 2003); and Mayo et al., J. Biol. Chem., 278:45746 (2003). In some cases, these modified peptidomimetic versions of the peptides and fragments disclosed herein exhibit enhanced stability in vivo, relative to the non-peptidomimetic peptides.
Methods for creating a peptidomimetic include substituting one or more, e.g., all, of the amino acids in a peptide sequence with D-amino acid enantiomers. Such sequences are referred to herein as “retro” sequences. In another method, the N-terminal to C-terminal order of the amino acid residues is reversed, such that the order of amino acid residues from the N-terminus to the C-terminus of the original peptide becomes the order of amino acid residues from the C-terminus to the N-terminus in the modified peptidomimetic. Such sequences can be referred to as “inverso” sequences.
Peptidomimetics can be both the retro and inverso versions, i.e., the “retro-inverso” version of a peptide disclosed herein. The new peptidomimetics can be composed of D-amino acids arranged so that the order of amino acid residues from the N-terminus to the C-terminus in the peptidomimetic corresponds to the order of amino acid residues from the C-terminus to the N-terminus in the original peptide.
Other methods for making a peptidomimetics include replacing one or more amino acid residues in a peptide with a chemically distinct but recognized functional analog of the amino acid, i.e., an artificial amino acid analog. Artificial amino acid analogs include β-amino acids, β-substituted β-amino acids (“β3-amino acids”), phosphorous analogs of amino acids, such as amino phosphonic acids and amino phosphinic acids, and amino acids having non-peptide linkages. Artificial amino acids can be used to create peptidomimetics, such as peptoid oligomers (e.g., peptoid amide or ester analogues), β-peptides, cyclic peptides, oligourea or oligocarbamate peptides; or heterocyclic ring molecules.
Also useful in the methods disclosed herein are nucleic acid molecules that encode SRPX agents described herein, e.g., naturally occurring SRPX polypeptides or forms of SRPX polypeptides in which naturally occurring amino acid sequences are altered or deleted (e.g., fragments or analogs of SRPX). Certain nucleic acids can encode polypeptides that are soluble under normal physiological conditions. SRPX agents can be expressed (e.g., exogenously expressed) within a cell by any means known in the art. To generate cells that express SRPX agents, the cells can be transfected, transformed, or transduced using any of a variety of techniques known in the art. Any number of transfection, transformation, and transduction protocols known to those in the art may be used, for example those outlined in Current Protocols in Molecular Biology, John Wiley & Sons, New York, N.Y., or in numerous kits available commercially (e.g., Invitrogen Life Technologies, Carlsbad, Calif.). Such techniques may result in stable or transient transformants. One suitable transfection technique is electroporation, which can be performed on a variety of cell types, including mammalian cells, yeast cells and bacteria, using commercially available equipment. Optimal conditions for electroporation (including voltage, resistance and pulse length) are experimentally determined for the particular host cell type, and general guidelines for optimizing electroporation can be obtained from manufacturers.
When the polypeptide expressed by a nucleic acid is intended to be secreted, the nucleic acid sequence can encode an N-terminal signal sequence that directs secretion of the polypeptide. In some embodiments, the signal sequence is a heterologous signal sequence. Signal sequences that function in prokaryotes and eukaryotes are well known, and one of ordinary skill can select or design an appropriate signal sequence accordingly. In some embodiments, the nucleic acid can encode a SRPX polypeptide, variant, or fragment as disclosed herein with a SRPX or heterologous signal sequence.
Exemplary methods of administering SRPX agents include introducing into a subject a nucleic acid that encodes an SRPX agent described herein. In some embodiments, the nucleic acid that encodes the SRPX agent is contained within a vector, e.g., as a virus that includes a nucleic acid that expresses the SRPX agent. Exemplary viral vectors include adenoviruses (reviewed in Altaras et al., 2005, Adv. Biochem. Eng. Biotechnol., 99:193-260), adeno-associated viruses (reviewed in Park et al., 2008, Front. Biosci., 13:2653-59; see also Williams, 2007, Mol. Ther., 15:2053-54), parvoviruses, lentiviruses, retroviruses (reviewed in Tai et al., 2008, Front. Biosci., 13:3083-95), and the herpes simplex virus. Methods of delivery of nucleic acids are reviewed in Patil et al., 2005, AAPS J., 7:E61-77, which is incorporated herein by reference in its entirety.
An exemplary AAV vector containing a polypeptide that includes SEQ ID NO:1 is shown in FIG. 4B and has the sequence:







(SEQ ID NO: 3)


attaggctgcgcgctcgctcgctcactgaggccgcccgggcaaagcccgg


 


gcgtcgggcgacctttggtcgcccggcctcagtgagcgagcgagcgcgca


 


gagagggagtggccaactccatcactaggggttccttgtagttaatgatt


 


aacccgccatgctacttatctaccagggtaatggggatcctctagaacta


 


tagctagcatgcctgcaggctgaccgcccaacgacccccgcccattgacg


 


tcaataatgacgtatgttcccatagtaacgccaatagggactttccattg


 


acgtcaatgggtggagtatttacggtaaactgcccacttggcagtacatc


 


aagtgtatcatatgccaagtccgccccctattgacgtcaatgacggtaaa


 


tggcccgcctggcattatgcccagtacatgaccttacgggactttcctac


 


ttggcagtacatctacgtattagtcatcgctattaccatggtgatgcggt


 


tttggcagtacaccaatgggcgtggatagcggtttgactcacggggattt


 


ccaagtctccaccccattgacgtcaatgggagtttgttttggcaccaaaa


 


tcaacgggactttccaaaatgtcgtaataaccccgccccgttgacgcaaa


 


tgggcggtaggcgtgtacggtgggaggtctatataagcagagctcgttta


 


gtgaaccgtcagatcactagaagctttattgcggtagtttatcacagtta


 


aattgctaacgcagtcagtgcttctgacacaacagtctcgaacttaagct


 


gcagaagttggtcgtgaggcactgggcaggtaagtatcaaggttacaaga


 


caggtttaaggagaccaatagaaactgggcttgtcgagacagagaagact


 


cttgcgtttctgataggcacctattggtcttactgacatccactttgcct


 


ttctctccacaggtgtccactcccagttcaattacagctcttaaggctag


 


agtacttaatacgactcactataggctagcctcgagaattcacgcgtggt


 


acggtaccatgatggagacagacacactcctgctatgggtactgctgctc


 


tgggttccaggttccactggtgacgcggcccagccggccaggcgcgcgcg


 


ccgtacgaagcttgactcaccactagaagacgatgaagtcgggtattcac


 


accctagatataaagataccccgtggtgctcccccatcaaggtgaagtat


 


ggggatgtgtactgcagggcccctcaaggaggatactacaaaacagccct


 


gggaaccaggtgcgacattcgctgccagaagggctacgagctgcatggct


 


cttccctactgatctgccagtcaaacaaacgatggtctgacaaggtcatc


 


tgcaaacaaaagcgatgtcctacccttgccatgccagcaaatggagggtt


 


taagtgtgtagatggtgcctactttaactcccggtgtgagtattattgtt


 


caccaggatacacgttgaaaggggagcggaccgtcacatgtatggacaac


 


aaggcctggagcggccggccagcctcctgtgtggatatggaacctcctag


 


aatcaagtgcccaagtgtgaaggaacgcattgcagaacccaacaaactga


 


cagtccgggtgtcctgggagacacccgaaggaagagacacagcagatgga


 


attcttactgatgtcattctaaaaggcctccccccaggctccaactttcc


 


agaaggagaccacaagatccagtacacagtctatgacagagctgagaata


 


agggcacttgcaaatttcgagttaaagtaagagtcaaacgctgtggcaaa


 


ctcaatgccccagagaatggttacatgaagtgctccagcgacggtgataa


 


ttatggagccacctgtgagttctcctgcatcggcggctatgagctccagg


 


gtagccctgcccgagtatgtcaatccaacctggcttggtctggcacggag


 


cccacctgtgcagccatgaacgtcaatgtgggtgtcagaacggcagctgc


 


acttctggatcagttttatgagaaaaggagactcctcattgtgtccacac


 


ccacagcccgaaacctcctttaccggctccagctaggaatgctgcagcaa


 


gcacagtgtggccttgatcttcgacacatcaccgtggtggagctggtggg


 


tgtgttcccgactctcattggcaggataggagcaaagattatgcctccag


 


ccctagcgctgcagctcaggctgttgctgcgaatcccactctactccttc


 


agtatggtgctagtggataagcatggcatggacaaagagcgctatgtctc


 


cctggtgatgcctgtggccctgttcaacctgattgacacttttcccttga


 


gaaaagaagagatggtcctacaagccgaaatgagccagacctgtaacacc


 


gctcgaggagggcccgaacaaaaactcatctcagaagagaatctgaatag


 


cgccgtcgaccatcatcatcatcatcattgaggtaccctctagagtcgac


 


ccgggcggcctcgaggacggggtgaactacgcctgaggatccgatctttt


 


tccctctgccaaaaattatggggacatcatgaagccccttgagcatctga


 


cttctggctaataaaggaaatttattttcattgcaatagtgtgttggaat


 


tttttgtgtctctcactcggaagcaattcgttgatctgaatttcgaccac


 


ccataatacccattaccctggtagataagtagcatggcgggttaatcatt


 


aactacaaggaacccctagtgatggagttggccactccctctctgcgcgc


 


tcgctcgctcactgaggccgggcgaccaaaggtcgcccgacgcccgggct


 


ttgcccgggcggcctcagtgagcgagcgagcgcgcagccttaattaatta


 


attaaggcctta






An exemplary AAV vector containing a polypeptide that includes SEQ ID NO:2 is shown in FIG. 5B and has the sequence:







(SEQ ID NO: 4)


attaggctgcgcgctcgctcgctcactgaggccgcccgggcaaagcccgg


 


gcgtcgggcgacctttggtcgcccggcctcagtgagcgagcgagcgcgca


 


gagagggagtggccaactccatcactaggggttccttgtagttaatgatt


 


aacccgccatgctacttatctaccagggtaatggggatcctctagaacta


 


tagctagcatgcctgcaggctgaccgcccaacgacccccgcccattgacg


 


tcaataatgacgtatgttcccatagtaacgccaatagggactttccattg


 


acgtcaatgggtggagtatttacggtaaactgcccacttggcagtacatc


 


aagtgtatcatatgccaagtccgccccctattgacgtcaatgacggtaaa


 


tggcccgcctggcattatgcccagtacatgaccttacgggactttcctac


 


ttggcagtacatctacgtattagtcatcgctattaccatggtgatgcggt


 


tttggcagtacaccaatgggcgtggatagcggtttgactcacggggattt


 


ccaagtctccaccccattgacgtcaatgggagtttgttttggcaccaaaa


 


tcaacgggactttccaaaatgtcgtaataaccccgccccgttgacgcaaa


 


tgggcggtaggcgtgtacggtgggaggtctatataagcagagctcgttta


 


gtgaaccgtcagatcactagaagctttattgcggtagtttatcacagtta


 


aattgctaacgcagtcagtgcttctgacacaacagtctcgaacttaagct


 


gcagaagttggtcgtgaggcactgggcaggtaagtatcaaggttacaaga


 


caggtttaaggagaccaatagaaactgggcttgtcgagacagagaagact


 


cttgcgtttctgataggcacctattggtcttactgacatccactttgcct


 


ttctctccacaggtgtccactcccagttcaattacagctcttaaggctag


 


agtacttaatacgactcactataggctagcctcgagaattcacgcgtggt


 


acggtaccatggggagccccgcacatcggcccgcgctgctgctgctgctg


 


ccgcctctgctgctgctgctgctgctgcgcgtcccgcccagccgcagctt


 


cccaggatcgggagactcaccactagaagacgatgaagtcgggtattcac


 


accctagatataaagataccccgtggtgctcccccatcaaggtgaagtat


 


ggggatgtgtactgcagggcccctcaaggaggatactacaaaacagccct


 


gggaaccaggtgcgacattcgctgccagaagggctacgagctgcatggct


 


cttccctactgatctgccagtcaaacaaacgatggtctgacaaggtcatc


 


tgcaaacaaaagcgatgtcctacccttgccatgccagcaaatggagggtt


 


taagtgtgtagatggtgcctactttaactcccggtgtgagtattattgtt


 


caccaggatacacgttgaaaggggagcggaccgtcacatgtatggacaac


 


aaggcctggagcggccggccagcctcctgtgtggatatggaacctcctag


 


aatcaagtgcccaagtgtgaaggaacgcattgcagaacccaacaaactga


 


cagtccgggtgtcctgggagacacccgaaggaagagacacagcagatgga


 


attcttactgatgtcattctaaaaggcctccccccaggctccaactttcc


 


agaaggagaccacaagatccagtacacagtctatgacagagctgagaata


 


agggcacttgcaaatttcgagttaaagtaagagtcaaacgctgtggcaaa


 


ctcaatgccccagagaatggttacatgaagtgctccagcgacggtgataa


 


ttatggagccacctgtgagttctcctgcatcggcggctatgagctccagg


 


gtagccctgcccgagtatgtcaatccaacctggcttggtctggcacggag


 


cccacctgtgcagccatgaacgtcaatgtgggtgtcagaacggcagctgc


 


acttctggatcagttttatgagaaaaggagactcctcattgtgtccacac


 


ccacagcccgaaacctcctttaccggctccagctaggaatgctgcagcaa


 


gcacagtgtggccttgatcttcgacacatcaccgtggtggagctggtggg


 


tgtgttcccgactctcattggcaggataggagcaaagattatgcctccag


 


ccctagcgctgcagctcaggctgttgctgcgaatcccactctactccttc


 


agtatggtgctagtggataagcatggcatggacaaagagcgctatgtctc


 


cctggtgatgcctgtggccctgttcaacctgattgacacttttcccttga


 


gaaaagaagagatggtcctacaagccgaaatgagccagacctgtaacacc


 


gaacaaaaactcatctcagaagaggatctgaatagcgccgtcgaccatca


 


tcatcatcatcattgaggtaccctctagagtcgacccgggcggcctcgag


 


gacggggtgaactacgcctgaggatccgatctttttccctctgccaaaaa


 


ttatggggacatcatgaagccccttgagcatctgacttctggctaataaa


 


ggaaatttattttcattgcaatagtgtgttggaattttttgtgtctctca


 


ctcggaagcaattcgttgatctgaatttcgaccacccataatacccatta


 


ccctggtagataagtagcatggcgggttaatcattaactacaaggaaccc


 


ctagtgatggagttggccactccctctctgcgcgctcgctcgctcactga


 


ggccgggcgaccaaaggtcgcccgacgcccgggctttgcccgggcggcct


 


cagtgagcgagcgagcgcgcagccttaattaattaattaaggcctta






In some embodiments, a nucleic acid that expresses a SRPX polypeptide is administered directly to cancer cells or to cells in the vicinity of the cancer cells. In some embodiments, a nucleic acid that expresses a SRPX polypeptide is administered to a cell ex vivo, which is then administered to the subject in the vicinity of the tumor.
A SRPX agent can be produced by any means known in the art, e.g., by chemical synthesis, recombinant methods, or isolation from cells that naturally produce SRPX. Methods of purification and isolation of molecules that include polypeptides are also well known to those of skill in the art.
Production of Fragments and Analogs of SRPX
Generation of Fragments
Fragments of a protein can be produced in several ways, e.g., recombinantly, by proteolytic digestion, or by chemical synthesis. Internal or terminal fragments of a polypeptide can be generated by removing one or more nucleotides from one end (for a terminal fragment) or both ends (for an internal fragment) of a nucleic acid that encodes the polypeptide. Expression of the mutagenized DNA produces polypeptide fragments. Digestion with “end-nibbling” endonucleases can thus generate DNAs that encode an array of fragments. DNAs that encode fragments of a protein can also be generated by random shearing, restriction digestion or a combination of the above-discussed methods.
Fragments can also be chemically synthesized using techniques known in the art such as conventional Merrifield solid phase f-Moc or t-Boc chemistry. For example, peptides of the present invention can be arbitrarily divided into fragments of desired length with no overlap of the fragments, or divided into overlapping fragments of a desired length.
Generation of Analogs: Production of Altered DNA and Peptide Sequences by Random Methods
Amino acid sequence variants of a protein can be prepared by random mutagenesis of DNA which encodes a protein or a particular domain or region of a protein. Useful methods include PCR mutagenesis and saturation mutagenesis. A library of random amino acid sequence variants can also be generated by the synthesis of a set of degenerate oligonucleotide sequences. (Methods for screening proteins in a library of variants are elsewhere herein.)
PCR Mutagenesis
In PCR mutagenesis, reduced Taq polymerase fidelity is used to introduce random mutations into a cloned fragment of DNA (Leung et al., 1989, Technique 1:11-15). This is a very powerful and relatively rapid method of introducing random mutations. The DNA region to be mutagenized is amplified using the polymerase chain reaction (PCR) under conditions that reduce the fidelity of DNA synthesis by Taq DNA polymerase, e.g., by using a dGTP/dATP ratio of five and adding Mn2+ to the PCR reaction. The pool of amplified DNA fragments is inserted into appropriate cloning vectors to provide random mutant libraries.
Saturation Mutagenesis
Saturation mutagenesis allows for the rapid introduction of a large number of single base substitutions into cloned DNA fragments (Mayers et al., 1985, Science 229:242). This technique includes generation of mutations, e.g., by chemical treatment or irradiation of single-stranded DNA in vitro, and synthesis of a complimentary DNA strand. The mutation frequency can be modulated by modulating the severity of the treatment, and essentially all possible base substitutions can be obtained. Because this procedure does not involve a genetic selection for mutant fragments both neutral substitutions, as well as those that alter function, are obtained. The distribution of point mutations is not biased toward conserved sequence elements.
Degenerate Oligonucleotides
A library of homologs can also be generated from a set of degenerate oligonucleotide sequences. Chemical synthesis of a degenerate sequences can be carried out in an automatic DNA synthesizer, and the synthetic genes then ligated into an appropriate expression vector. The synthesis of degenerate oligonucleotides is known in the art (see for example, Narang, S A (1983) Tetrahedron 39:3; Itakura et al. (1981) Recombinant DNA, Proc 3rd Cleveland Sympos. Macromolecules, ed. A G Walton, Amsterdam: Elsevier pp 273-289; Itakura et al. (1984) Annu. Rev. Biochem. 53:323; Itakura et al. (1984) Science 198:1056; Ike et al. (1983) Nucleic Acid Res. 11:477. Such techniques have been employed in the directed evolution of other proteins (see, for example, Scott et al. (1990) Science 249:386-390; Roberts et al. (1992) PNAS 89:2429-2433; Devlin et al. (1990) Science 249: 404-406; Cwirla et al. (1990) PNAS 87: 6378-6382; as well as U.S. Pat. Nos. 5,223,409, 5,198,346, and 5,096,815).
Generation of Analogs: Production of Altered DNA and Peptide Sequences by Directed Mutagenesis
Non-random or directed, mutagenesis techniques can be used to provide specific sequences or mutations in specific regions. These techniques can be used to create variants that include, e.g., deletions, insertions, or substitutions, of residues of the known amino acid sequence of a protein. The sites for mutation can be modified individually or in series, e.g., by (1) substituting first with conserved amino acids and then with more radical choices depending upon results achieved, (2) deleting the target residue, or (3) inserting residues of the same or a different class adjacent to the located site, or combinations of options 1-3.
Alanine Scanning Mutagenesis
Alanine scanning mutagenesis is a useful method for identification of certain residues or regions of the desired protein that are preferred locations or domains for mutagenesis, Cunningham and Wells (Science 244:1081-1085, 1989). In alanine scanning, 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). Replacement of an amino acid can affect the interaction of the amino acids with the surrounding aqueous environment in or outside the cell. Those domains demonstrating functional sensitivity to the substitutions are then 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 optimize the performance of a mutation at a given site, alanine scanning or random mutagenesis can be conducted at the target codon or region and the expressed desired protein subunit variants are screened for the optimal combination of desired activity.
Oligonucleotide-Mediated Mutagenesis
Oligonucleotide-mediated mutagenesis is a useful method for preparing substitution, deletion, and insertion variants of DNA, see, e.g., Adelman et al., (DNA 2:183, 1983). Briefly, the desired DNA is altered by hybridizing an oligonucleotide encoding a mutation to a DNA template, where the template is the single-stranded form of a plasmid or bacteriophage containing the unaltered or native DNA sequence of the desired protein. After hybridization, a DNA polymerase is used to synthesize an entire second complementary strand of the template that will thus incorporate the oligonucleotide primer, and will code for the selected alteration in the desired protein DNA. Generally, oligonucleotides of at least 25 nucleotides in length are used. An optimal oligonucleotide will have 12 to 15 nucleotides that are completely complementary to the template on either side of the nucleotide(s) coding for the mutation. This ensures that the oligonucleotide will hybridize properly to the single-stranded DNA template molecule. The oligonucleotides are readily synthesized using techniques known in the art such as that described by Crea et al. (Proc. Natl. Acad. Sci. (1978) USA, 75: 5765).
Cassette Mutagenesis
Another method for preparing variants, cassette mutagenesis, is based on the technique described by Wells et al. (Gene (1985) 34:315). The starting material is a plasmid (or other vector) that includes the protein subunit DNA to be mutated. The codon(s) in the protein subunit DNA to be mutated are identified. There must be a unique restriction endonuclease site on each side of the identified mutation site(s). If no such restriction sites exist, they can be generated using the above-described oligonucleotide-mediated mutagenesis method to introduce them at appropriate locations in the desired protein subunit DNA. After the restriction sites have been introduced into the plasmid, the plasmid is cut at these sites to linearize it. A double-stranded oligonucleotide encoding the sequence of the DNA between the restriction sites but containing the desired mutation(s) is synthesized using standard procedures. The two strands are synthesized separately and then hybridized together using standard techniques. This double-stranded oligonucleotide is referred to as the cassette. This cassette is designed to have 3′ and 5′ ends that are comparable with the ends of the linearized plasmid, such that it can be directly ligated to the plasmid. This plasmid now contains the mutated desired protein subunit DNA sequence.
Combinatorial Mutagenesis
Combinatorial mutagenesis can also be used to generate mutants. For example, the amino acid sequences for a group of homologs or other related proteins are aligned, preferably to promote the highest homology possible. All of the amino acids that appear at a given position of the aligned sequences can be selected to create a degenerate set of combinatorial sequences. The variegated library of variants is generated by combinatorial mutagenesis at the nucleic acid level, and is encoded by a variegated gene library. For example, a mixture of synthetic oligonucleotides can be enzymatically ligated into gene sequences such that the degenerate set of potential sequences are expressible as individual peptides, or alternatively, as a set of larger fusion proteins containing the set of degenerate sequences.
Primary High-Through-Put Methods for Screening Libraries of Peptide Fragments or Homologs
Various techniques are known in the art for screening generated mutant gene products. Techniques for screening large gene libraries often include cloning the gene library into replicable expression vectors, transforming appropriate cells with the resulting library of vectors, and expressing the genes under conditions in which detection of a desired activity, e.g., inhibition of growth of human cancer cell lines (e.g., NCI-H23, EKVX, HOP-62, HOP-92, HCT-15, SW-620, COLO205, HT29, HCT-116, KM-12, CCRF-CEM, K-562, MOLT-4, SR, RPMI-8226, A549-ATCC, NCI-H226, NCI-H322M) is measured. Each of the techniques described below is amenable to high through-put analysis for screening large numbers of sequences created, e.g., by random mutagenesis techniques.
Cancers
The new methods can be used to treat several types of cancer, e.g., lung cancers (e.g., adenocarcinoma, nonsmall cell lung cancer), colorectal cancers, thyroid cancers (e.g., papillary thyroid carcinoma, anaplastic thyroid carcinoma, follicular carcinoma, follicular adenoma), lymphomas (e.g., non-Hodgkin lymphoma), multiple myeloma, leukemias, breast cancers, ovarian cancers, gastric cancers, bladder cancers, pancreatic cancers, gall bladder cancers, bile duct cancers, and other carcinomas. In some embodiments, the present methods can be used to treat a subject having an epithelial cancer, e.g., a solid tumor of epithelial origin, e.g., lung, breast, ovarian, prostate, renal, pancreatic, or colon cancer. Methods of diagnosing cancers are well known to those of skill in the art.
In addition, the methods described herein can include identifying the cancer as lacking SRPX expression. A number of methods for detecting levels of SRPX expression are known in the art. In some embodiments, levels of SRPX mRNA are detected in cells from the tumor; alternatively or in addition, levels or SRPX polypeptide are detected in a sample comprising tissue or cells from the tumor. See, e.g., Yamashita et al. 1999, Oncogene 18:4777; Tambe et al. 2009, Cancer Lett 283:74; Kim et a. 2003, Hum Pathol 34:654; Mukaisho et al. 2002, Jpn J Cancer Res 93:888; Shimakage et al. 2000, Int J Cancer 87:5; Shimakage et al. 2002, Hum Pathol 33:615; Shimakage et al. 2009, Oncol Rep 21:1367; and Tambe et al. 2007, Carcinogenesis 28(4):777-784, all of which are incorporated herein by reference.
Pharmaceutical Formulations
The SRPX agents described herein (all of which can be referred to herein as “active compounds”), can be incorporated into pharmaceutical compositions. Such compositions typically include the active compound and a pharmaceutically acceptable carrier or excipient. A “pharmaceutically acceptable carrier” can include solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. Supplementary active compounds can also be incorporated into the compositions.
There are a number of methods by which the new compositions for use in the new methods can be delivered to subjects, in general, and to specific cells or tissue in those subjects, in particular. For example, a SRPX agent (e.g., a polypeptide or active fragment thereof) as described herein can be injected into a subject or a tissue of the subject. In another example, a vector (e.g., a plasmid or virus) encoding a SRPX agent can be introduced into a cell or tissue of the subject. The vector would then enter the cell or cells in that tissue and express the SRPX agent. Delivery specificity of such plasmids can be enhanced by associating them with organ- or tissue-specific affinity, so that they preferentially enter specified cell types; in preferred embodiments, the vector would enter cells in or near the tumor. Because SRPX can act extracellularly, it is not necessary to deliver the vector directly to tumor cells. The vector can be delivered to the tissue surrounding the tumor, or cells expressing and secreting SRPX can be delivered to a site near the tumor. Similarly, when SRPX polypeptides or active fragments thereof are administered, the active agents need not enter the cells, but are delivered to the extracellular surface. Methods of expressing proteins for tumor therapy are described, e.g., in Cross and Burmester, 2006, Clin. Med. Res., 4:218-227; Lejuene et al., 2007, Expert Rev. Anticancer Ther. 7:701-713; and Bloquel et al., 2004, J. Gene Med., 6:S11-S23.
Compounds and their physiologically acceptable salts and solvates can be formulated for oral, topical, buccal, parenteral or rectal administration or administration by inhalation or insufflation (either through the mouth or the nose).
The compounds will generally be formulated for parenteral administration by injection, for example, by bolus injection or continuous infusion. Formulations for injection can be presented in unit dosage form, for example, in ampoules or in multi-dose containers, with an added preservative. The compositions can take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and can contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient can be in powder form for constitution with a suitable vehicle, for example, sterile pyrogen-free water, before use. Where the compositions are intended for use in a specific treatment area, the compositions can be administered by one or more local injections into the tumor site to diminish as much as possible any side effects relating to the compound's activities outside of the treatment area.
In addition to the formulations described previously, the compounds can also be formulated as a depot preparation. Such long acting formulations can be administered by implantation (for example subcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the compounds can be formulated with suitable polymeric or hydrophobic materials (for example as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt. A depot preparation can include embedded or encapsulated cells or tissue that secrete a SRPX agent, which can be administered, e.g., by implantation or by intramuscular injection.
The compositions can, if desired, be presented in a pack or dispenser device that can contain one or more unit dosage forms containing the active ingredient. The pack can, for example, include metal or plastic foil, such as a blister pack. The pack or dispenser device can be accompanied by instructions for administration.
The therapeutic compositions of the invention can also contain a carrier or excipient, many of which are known to skilled artisans. Methods for making such formulations are well known and can be found in, for example, Remington: The Science and Practice of Pharmacy, University of the Sciences in Philadelphia (USIP), 2005.
The SRPX-encoding nucleic acid compositions can also be formulated for intracellular delivery of the active compounds, using methods known in the art. For example, the compositions can include liposomes or other carriers that deliver the active compound across the plasma membrane. Vesicles that are covered with membrane-permeant peptides, such as Tat or Antennapedia, can also be used. A number of other methods for enhancing intracellular delivery are familiar to those of skill in the art. Such methods are not needed when the SRPX polypeptides or fragments thereof are used, as the SRPX polypeptides act extracellularly, and are thus delivered to the extracellular surface of the tumor cells. Thus in some embodiments, the methods include the use of a composition comprising a SRPX polypeptide or active fragment thereof, but not including any cell membrane permeation-enhancing compounds, e.g., the composition does not include liposomes or membrane-permeant peptides.
It is recognized that the pharmaceutical compositions and methods described herein can be used independently or in combination with one another. That is, subjects can be administered one or more of the pharmaceutical compositions, e.g., pharmaceutical compositions that include a SRPX agent, subjected to one or more of the therapeutic methods described herein, or both, in temporally overlapping or non-overlapping regimens. When therapies overlap temporally, the therapies can generally occur in any order and can be simultaneous (e.g., administered simultaneously together in a composite composition or simultaneously but as separate compositions) or interspersed. By way of example, a subject afflicted with a disorder described herein can be simultaneously or sequentially administered both a cytotoxic agent which selectively kills aberrant cells and an antibody (e.g., an antibody of the invention) which can, in one embodiment, be conjugated or linked with a therapeutic agent, a cytotoxic agent, an imaging agent, or the like.
Effective Doses
Toxicity and therapeutic efficacy of a SRPX agent can be determined by standard pharmaceutical procedures, using either cells in culture or experimental animals to determine the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Inhibitors that exhibit large therapeutic indices are preferred. While inhibitors that exhibit toxic side effects can be used, care can be taken to design a delivery system that targets such compounds to the site of affected tissue to minimize potential damage to non-target cells and, thereby, reduce side effects.
The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage can vary within this range depending upon the dosage form employed and the route of administration utilized. For any compound used in the new methods, the therapeutically effective dose can be estimated initially from cell culture assays. A dose can also be calculated in animal models to achieve a circulating plasma concentration range that includes the IC50 (that is, the concentration of the test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans.
EXAMPLES
Example 1
SRPX Inhibits the Growth of Cancer Cells and Lung Cancer Xenografts
Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis was performed to monitor SRPX expression in 9 normal lung samples, 14 lung adenocarcinoma samples, and 6 lung squamous cell carcinoma samples. Total RNA from the human samples was obtained from the University of Massachusetts Medical School Cancer Center Tissue Bank. Reverse transcription was performed using SuperScriptTM II Reverse Transcriptase (Invitrogen) and an oligo(dT) primer (Invitrogen), followed by quantitative PCR using Fast SYBRTM Green Master Mix (Applied Biosystems) and gene-specific primers for SRPX. For each sample, expression of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) provided an internal normalization control. For normal lung samples, the average of the 9 samples is shown. Error bars indicate standard deviation. SRPX expression was significantly decreased relative to normal lung tissue in all squamous cell carcinoma samples and at least 13 of 14 lung adenocarcinoma samples (FIG. 1A).
To determine if SRPX could affect growth of cancer cells, several lung cancer cell lines and, as a control, the normal lung cell line MRC5, were plated in 6-well plates (3×105 cells per well), treated with or without 10 μg/ml recombinant SRPX (rSRPX) and stained with crystal violet. To express and purify rSRPX, an SRPXsec expression construct including a nucleic acid encoding SEQ ID NO:1 with a heterologous signal sequence and Myc and His6 tags was transfected into FreeStyleTM Chinese Hamster Ovary (CHO) cells (Invitrogen), and conditioned medium was collected 96 hours later and incubated with TALONTM Metal Affinity Resin (Clontech) to purify the His6-tagged SRPX protein. The purified protein was dialyzed in phosphate buffered saline (PBS) to remove free salts. rSRPX decreased growth of the cancer cell lines tested but had no effect on the growth of the normal lung cell line (FIG. 1B).
To investigate the effect of SRPX on tumors in vivo, 5×106 A549 human alveolar adenocarcinoma cells (mixed with MatrigelTM matrix in a volume of 100 μl) were injected subcutaneously into the right flank of female BALB/c nu/nu (nude) mice (n=2 mice per experimental group). Three days later, the mice were injected into the anterior tibialis muscle of the left leg with either 3.0×1011 particles of AAV-SRPXwt or, as a control, AAV-LacZ. Tumor dimensions were measured on days 7, 11, 17, 23, 30 and 38 after injection, and tumor volume was calculated using the formula π/6×(length)×(width)2. Error bars indicate standard deviation. AAV-SRPX significantly reduced tumor growth at days 30 and 38 as compared to the control (FIG. 1C).
In another experiment, about 106 A549 cells were injected in Balb/c Nu/Nu mice, and AAv9-SRPX virus was injected when the tumors reached the size of 250 mm3. The results, shown in FIG. 1D, are for two mice per group as one animal in the control group failed to develop the tumor and one animal in SRPX group developed an abnormal mass around the belly. The difference in tumor growth is very significant.
To determine whether in vivo administration of SRPX was associated with significant toxicity, increasing doses were administered to mice and levels of liver enzymes, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), increases in which are typically associated with toxic insult, were measured. The results, as shown in FIGS. 1E (ALT) and 1F (AST), demonstrated that SRPX has no detectable liver toxicity at the doses tested.
The NCI60 panel of human cancer cell lines (see Shoemaker, 2006, Nat. Rev. Cancer, 6:813-823) was obtained from the National Cancer Institute. The panel includes cell lines corresponding to breast (MDA-MB-231, HS 578T, 8T-549, T47-D, MCF7), ovarian (NCI-ADR-RES, OVCAR-3, OVCAR-5, OVCAR-8, OVCAR-4, SK-OV-3, IGROV1), prostate (DU-145, PC-3), renal (TK-10, CAKI-1, A496, ACHN, RXF-393, 786-0, SN12C, UO-31), non-small-cell lung (NCI-H460, HOP-62, A549-ATCC, NCI-H226, EKVX, NCI-H322M, HOP-92, NCI-H522), central nervous system (CNS) (SF-295, SF-268, SF-539, SNB-19, SNB-75, U251), colon (HCT-15, SW-620, COLO205, HT29, HCC-2998, HCT-116, KM-12), melanoma (SK-MEL-28, SK-M2L-2, LOX IMVI, M14, MALM-3M, SK-MEL-5, UACC-257, UACC-62, MDA-MB-435), and hematopoietic (CCRF-CEM, K-562, MOLT-4, SR, RPMI-8226) cancers (only a subset of the NCI60 panel is shown). Cells (3×105 for breast, colon, leukemia, lung cell lines, and 2×105 for melanoma cell lines) were plated and treated with 30% control CM or SRPX-containing CM (produced as described above for FIG. 1B), or left untreated. After 3 days, the CM was replaced with complete medium, and the cells allowed were to grow for an additional 4 days before staining with crystal violet. Percent growth was calculated relative to the untreated control cells, which was set to 100%. Error bars indicate standard deviation. The results show that in addition to lung cancer, SRPX inhibits the growth of several other cancer cell types, including breast cancer, colon cancer, and leukemia cell lines (FIG. 2).
As a secreted protein, SRPX contains an N-terminal signal sequence that directs its secretion. To determine whether the signal sequence is required for the ability of SRPX to inhibit cancer cell growth, a derivative of full-length SRPX that lacks the N-terminal signal sequence (amino acids 1-35; hereafter called SRPX(Δ1-35)) was constructed and tested for its ability to inhibit growth of A549 human lung adenocarcinoma epithelial cells. Briefly, 3×105 A549 cells were plated in 6-well plates and treated with 30% CM derived from cells expressing either empty vector (control), full-length SRPX or SRPX(Δ1-35). After 3 days, the CM was replaced with complete medium, and the cells were allowed to grow for an additional 4 days before staining with crystal violet. The results show that in contrast to full-length SRPX, SRPX(Δ1-35) does not inhibit growth of A549 cells (FIG. 3A). To confirm these results, the ability of SRPX(Δ1-35) was analyzed for its ability to kill A549 cells using an apoptosis assay. A549 cells (1.5×106) were transfected with a construct expressing either full-length SRPX or SRPX(Δ1-35), and 48 hours later were stained with Annexin V and 7 AAD (BD Bioscience) and analyzed by fluorescence-activated cell sorting (FACS). The results show that SRPX(Δ1-35) did not induce apoptosis compared to full-length SRPX. Immunoblot analysis confirmed that SRPX(Δ1-35) is expressed at roughly equivalent levels to full-length SRPX but, as expected, is not secreted into the CM (FIG. 3C). Collectively, the results show that secretion of SRPX is required for cell killing and that SRPX mediates cell killing extracellularly.
These results strongly support the use of SRPX to treat and prevent a wide range of cancers, including lung cancers, colon cancers, and leukemias.
Other Embodiments
A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

## Claims

1. A method of treating a solid tumor in a mammalian subject, the method comprising:
identifying a subject having a solid tumor;
administering to the subject an effective amount of a therapeutic composition comprising an SRPX polypeptide that is at least 80% identical to SEQ ID NO:1, wherein the composition is administered to the extracellular surfaces of cells in the tumor by one or more local injections into the tumor site, thereby treating the tumor.

2. The method of claim 1, wherein the tumor is a carcinoma.

3. The method of claim 1, wherein the tumor is a lung adenocarcinoma.

4. The method of claim 1, wherein the tumor is a breast cancer, bladder cancer, ovarian cancer, pancreatic cancer, colon cancer, colorectal cancer, or papillary thyroid carcinoma.

5. The method of claim 1, wherein the SRPX agent comprises a polypeptide at least 90% identical to SEQ ID NO:1.

6. The method of claim 1, wherein the polypeptide is at least 95% identical to SEQ ID NO:1.