DESCRIPTION IMMUNITY-INDUCING AGENT Technical Field [0001] The present invention relates to a novel immunity-inducing agent that is useful as a therapeutic and/or preventive agent for cancer or the like. Background Art [0002] Cancer is the overall leading cause of death. At present, the primary form of cancer treatment technique is surgical treatment, which is carried out in combination with radiation treatment and chemotherapy. In spite of the development of novel surgical techniques and the discovery of novel anticancer agents of recent years, outcomes from cancer treatment still remain unimproved, except in the cases of some types of cancer. In recent years, cancer antigens recognized by cytotoxic T cells that are reactive to cancer and genes encoding cancer antigens have been identified along with the development of molecular biology and cancer immunology, and expectations for antigen-specific immunotherapy have increased (Tsuyoshi Akiyoshi, Gan to Kagaku Ryouhou (Cancer and Chemotherapy), 1997, vol. 24, pp. 551-519, Cancer and Chemotherapy Publishers Inc., Japan). [0003] Immunotherapy requires the cancer-cell-specific presence of a peptide, polypeptide, or protein that is recognized as a target antigen, as well as substantial absence thereof in normal cells from the viewpoint of alleviation of side effects. In 1991, Boon et al. (the Ludwig Institute for Cancer Research, Belgium) isolated the human melanoma antigen MAGE1 recognized by the CD8+ T cell via cDNA expression cloning using an autologous cancer cell line and cancer-reactive T cells (Bruggen P. et al., Science, 254: 1643-1647, 1991). Thereafter, the SEREX (serological identifications of antigens by recombinant expression cloning) method, which identifies the tumor antigen recognized by the antibody produced in response to autologous cancer in the body of a cancer patient via gene expression cloning was reported (Proc. Natl. Acad. Sci. U.S.A., 92: 11810-11813, 1995; and US Patent No. 5,698,396). Some cancer antigens have been isolated by such techniques (Int. J. Cancer, 72: 965-971, 1997; Cancer Res., 58: 1034-1041, 1998; Int. J. Cancer, 29: 652-658, 1998; Int. J. Oncol., 14: 703-708, 1999; Cancer Res., 56: 4766-4772, 1996; and Hum. Mol. Genet. 6: 33-39, 1997). In addition, clinical testing of cancer immunotherapy targeting some such antigitens has been initiated. [0004] As in the case of humans, dogs and cats are known to suffer from a variety of tumors, such as mammary gland cancer, leukemia, and lymphoma, and tumors are highly ranked in statistics for canine or feline diseases. However, there are no effective therapeutic, preventive, or diagnostic agents for canine or feline cancer at present. Most dog or cat owners would not notice canine or feline tumors until tumors become advanced and enlarged. Even if tumors are removed via surgical operation or drugs for human use (e.g., anticancer drugs) are administered, tumors are often already beyond cure, and animals often die shortly after treatment. Under such circumstances, if therapeutic, preventive, and diagnostic agents for cancer that are effective for dogs or cats become available, application thereof for canine or feline cancer can be expected. [0005] The cytoplasmic and proliferation-associated protein 1 (CAPRIN-1) is expressed when dormant normal cells are activated or undergo cell division. CAPRIN-1 is an intracellular protein that is known to form intracellular stress granules with RNA in the cell and to be associated with regulation of mRNA transportation and translation. CAPRIN-1 is also known by various other names, and examples thereof include the GPI-anchored membrane protein 1 and the membrane component surface marker 1 protein (MUSI). CAPRIN-1 has names that convey the impression that it has been known as a cell membrane protein. Such other names derive from a report to the effect that the CAPRJN-1 gene sequence has a GPI-binding region and it is a membrane protein expressed in a large-intestine-derived cell line (J. Biol. Chem., 270: 20717-20723, 1995). Later, however, it was known that the CAPRIN-1 gene sequence in this report was incorrect, and in the gene sequence, deletion of a single nucleotide from the CAPRIN-1 gene sequence currently registered in the GenBank or the like causes a frame shift, thereby leading to deletion of 80 amino acids from the C terminus, and therefore the resulting artifact (74 amino acids) was the GPI-binding region mentioned in the foregoing report. In addition, it was also known that the CAPRIN-1 gene sequence shown in the report also had an error at the 5' side, and 53 amino acid residues had been deleted from the N-terminus (J. Immunol., 172: 2389-2400, 2004). It has also been reported that the protein encoded by the CAPRIN-1 gene sequence currently registered in GenBank or the like is not a cell membrane protein (J. Immunol., 172:2389-2400,2004). [0006] Based on the report of J. Biol. Chem., 270: 20717-20723, 1995, that CAPRIN-1 is a cell membrane protein, US 2008/0075722 and WO 2005/100998 describe that CAPRIN-1 can be a target of cancer therapy as a cell membrane protein under the name of Ml IS 1. However, they do not include any specific descriptions in the Examples. As reported in J. Immunol., 172: 2389-2400, 2004, however, it has been heretofore accepted since US 2008/0075722 was filed that CAPRIN-1 is not expressed on a cell surface. It is apparent that the disclosures of US 2008/0075722 and WO 2005/100998 based only on the incorrect information that CAPRIN-1 is a cell membrane protein should not be understood as general technical knowledge in the art. In addition, there is no report that the expression level of CAPRIN-1 is higher in cancer cells such as breast cancer cells than in normal cells. Summary of the Invention Problem to Be Solved by the Invention [0009] It is an object of the present invention to discover a novel polypeptide useful for a therapeutic and/or preventive agent for cancer and to provide use of such polypeptide as an immunity-inducing agent. Means for Solving the Problem [0010] The present inventors have conducted concentrated studies, and then they obtained cDNAs encoding proteins that bind to antibodies in the serum obtained from a cancer-bearing living body by the SEREX method using a canine-testicular-tissue-derived cDNA library and the serum of a dog afflicted with breast cancer, and they prepared a canine CAPRIN-1 polypeptide having the amino acid sequences shown by SEQ ID NOs: 6, 8, 10, 12, and 14 using such cDNAs. Using the human homologous gene of the obtained gene, also, they prepared a human CAPRIN-1 polypeptide having the amino acid sequences as shown by SEQ ID NOs: 2 and 4. Further, they found that such CAPRIN-1 polypeptides were expressed specifically in a breast cancer, brain tumor, leukemia, lymphoma, lung cancer, esophagus cancer, and colorectal cancer. Furthermore, they found that administration of such CAPRIN-1 polypeptides to living bodies would lead to induction of immunocytes against CAPRIN-1 polypeptides in the living bodies and regression of tumors in living bodies expressing the CAPRIN-1 genes. In addition, they found that the antibodies against such CAPRIN-1 polypeptides would disrupt cancer cells that express the CAPRIN-1 genes and induce antitumor effects in vivo. This has led to the completion of the present invention. [0011] Accordingly, the present invention has the following features. [0012] (1) An immunity-inducing agent comprising, as an active ingredient, at least one polypeptide having immunity-inducing activity and selected from the following polypeptides (a), (b), and (c), or a recombinant vector comprising a polynucleotide encoding such polypeptide and capable of expressing such polypeptide in vivo: [0013] (a) a polypeptide of at least seven contiguous amino acids of the amino acid sequence shown by any even SEQ ID number selected from SEQ ID NOs: 2 to 30 listed in the Sequence Listing; (b) a polypeptide of at least seven amino acids having 90% or more sequence identity with the polypeptide (a); and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof. (2) The immunity-inducing agent according to (1), wherein the polypeptide (b) is a polypeptide having 95% or more sequence identity with the polypeptide (a). [0014] (3) The immunity-inducing agent according to (1), wherein the polypeptide having immunity-inducing activity is a polypeptide of at least seven contiguous amino acids of the amino acid sequence shown by any even SEQ ID number selected from SEQ ID NOs: 2 to 30 listed in the Sequence Listing or a polypeptide comprising such polypeptide as a partial sequence thereof. [0015] (4) The immunity-inducing agent according to (3), wherein the polypeptide having immunity-inducing activity is a polypeptide comprising the amino acid sequence shown by any even SEQ ID number selected from SEQ ID NOs: 2 to 30 listed in the Sequence Listing. [0016] (5) The immunity-inducing agent according to (3), wherein the polypeptide having immunity-inducing activity is a polypeptide of at least seven contiguous amino acids in the region of amino acid residues (aa) 41 to 400 or amino acid residues (aa) 503 to 564 of the amino acid sequence shown by any even SEQ ID number selected from SEQ ID NOs: 2 to 30 listed in the Sequence Listing except for SEQ ID NO: 6 and SEQ ID NO: 18 or a polypeptide comprising such polypeptide as a partial sequence thereof. [0017] (6) The immunity-inducing agent according to (5), wherein the polypeptide having immunity-inducing activity is a polypeptide of the amino acid sequence shown by any of SEQ ID NOs: 43 to 76 in the Sequence Listing or a polypeptide of 8 to 12 amino acids comprising the amino acid sequence shown by any of SEQ ID NOs: 43 to 76 in the Sequence Listing as a partial sequence thereof. [0018] (7) The immunity-inducing agent according to any of (1) to (6), which comprises, as an active ingredient, one or plural types of such polypeptides. [0019] (8) The immunity-inducing agent according to (7), wherein the polypeptide is an agent for treating an antigen-presenting cell. [0020] (9) The immunity-inducing agent according to any of (1) to (7), which is for use in the treatment or prevention of animal cancer. [0021] (10) The immunity-inducing agent according to (9), wherein the cancer is breast cancer, brain tumor, leukemia, lymphoma, lung cancer, esophagus cancer, or colorectal cancer. [0022] (11) The immunity-inducing agent according to (9), wherein the animal is a human, dog, or cat. [0023] (12) The immunity-inducing agent according to any of (1) to (11), which further comprises an immunopotentiating agent. [0024] (13) The immunity-inducing agent according to (12), wherein the immunopotentiating agent is at least one adjuvant or cytokine selected from the group consisting of Freund's incomplete adjuvant, Montanide, poly IC and a derivative thereof, CpG oligonucleotide, interleukin 12, interleukin 18, interferon a, interferon p, interferon co, interferon y, and Flt3 ligand. [0025] (14) An isolated antigen-presenting cell comprising a complex of the above-mentioned polypeptide having immunity-inducing activity and an HLA molecule. [0026] (15) An isolated T cell, which selectively binds to a complex of the above-mentioned polypeptide having immunity-inducing activity and an HLA molecule. [0027] (16) A method for inducing immunity comprising administering to an individual at least one polypeptide having immunity-inducing activity and selected from the following polypeptides (a) to (c), or a recombinant vector comprising a polynucleotide encoding such polypeptide and capable of expressing such polypeptide in vivo: [0028] (a) a polypeptide of at least seven contiguous amino acids of the amino acid sequence shown by any even SEQ ID number selected from SEQ ID NOs: 2 to 30 listed in the Sequence Listing; (b) a polypeptide of at least seven amino acids having 90% or more sequence identity with the polypeptide (a); and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence thereof. Effects of the Invention [0029] The present invention provides a novel immunity-inducing agent useful for treatment and/or prevention of cancer. As specifically described in the examples below, administration of the polypeptide used in the present invention to a cancer-bearing animal enables induction of an immunocyte in the body of such cancer-bearing animal, which further enables shrinkage or regression of existing cancer. Brief Description of the Drawings [0030] Fig. 1 shows the expression pattern of the gene encoding the CAPRIN-1 polypeptide in normal tissue and a tumor cell line. Reference number 1 represents the expression pattern of the gene encoding the CAPRIN-1 protein, and Reference number 2 represents the expression pattern of the GAPDH gene. In Fig. 2, Reference numbers 3 to 31 on the horizontal axis each represent the capacity of HLA-A0201+ CD8+ T cells for producing IFN-y stimulated by the T2 cells pulsed with the peptides of SEQ ID NOs: 43 to 71. Reference number 32 represents the results regarding a negative control peptide of SEQ ID NO: 77 (a peptide having a sequence outside the scope of the present invention). In Fig. 3, Reference numbers 33 to 37 on the horizontal axis each represent the capacity of the HLA-A24+ CD8+ T cells for producing IFN-y stimulated by the JTK-LCL cells pulsed with the peptides of SEQ ID NOs: 72 to 76. Reference number 38 represents the results regarding a negative control of SEQ ID NO: 77. In Fig. 4, Reference numbers 39 to 67 on the horizontal axis each represent the cytotoxic activity of the HLA-A0201+ CD8+ T cells stimulated with the use of the peptides of SEQ ID NOs: 43 to 71 on the U-87MG cells. Reference number 68 represents the cytotoxic activity of the CD8+ T cells induced with the use of a negative control peptide (SEQ ID NO: 77). In Fig. 5, Reference numbers 69 to 73 on the horizontal axis each represent the cytotoxic activity of the HLA-A24+ CD 8+ T cells stimulated with the use of the peptides of SEQ ID NOs: 72 to 76 on the JTK-LCL cells. Reference number 74 represents the cytotoxic activity of the CD8+ T cells induced with the use of a negative control peptide (SEQ ID NO: 77). Embodiments for Carrying Out the Invention [0031] The polypeptides contained in the immunity-inducing agent of the present invention as an active ingredient include one or a plurality of polypeptides selected from the following polypeptides (a), (b), and (c): [0032] (a) a polypeptide of at least seven contiguous amino acids in a polypeptide having the amino acid sequence shown by any even SEQ ID number selected from SEQ ID NOs: 2 to 30 listed in the Sequence Listing and having immunity-inducing activity; (b) a polypeptide having 90% or more sequence identity with the polypeptide (a), consisting of at least 7 amino acids, and having immunity-inducing activity; and (c) a polypeptide comprising the polypeptide (a) or (b) as a partial sequence and having immunity-inducing activity. The term "polypeptide" used herein refers to a molecule formed via peptide bonds among a plurality of amino acids. The term refers not only to a polypeptide molecule constituted by a large number of amino acids but also a low-molecular-weight molecule constituted by a small number of amino acids (an oligopeptide) and a full-length protein. In the present invention, the term "polypeptide" also refers to a protein of a full length sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30. [0033] The nucleotide sequences of polynucleotides encoding separate proteins consisting of the amino acid sequences as shown by even SEQ ID numbers among SEQ ID NOs: 2 to 30 (i.e., SEQ ID NOs: 2, 4, 6...28, and 30) are shown by odd SEQ ID numbers among SEQ ID NOs: 1 to 29 (i.e., SEQ ID NOs:l, 3, 5...27, and 29). [0034] The term "having the amino acid sequence" used herein refers to a sequence composed of amino acid residues in a particular order. For example, the term "a polypeptide having the amino acid sequence shown by SEQ ID NO: 2" refers to a polypeptide of 709 amino acid residues in length possessing the amino acid sequence shown by SEQ ID NO: 2, i.e., Met Pro Ser Ala Thr...(snip)...Gin Gin Val Asn,. The term "a polypeptide having the amino acid sequence shown by SEQ ID NO: 2" may be occasionally abbreviated as "the polypeptide of SEQ ID NO: 2." The same applies to the expression "having the nucleotide sequence." In the context of that, the term "having" is interchangeable with the expression "consisting of." [0035] The term "immunity-inducing activity" used herein refers to the capacity for inducing an immunocyte that secretes cytokine, such as interferon or interleukin, in vivo. [0036] Whether or not a polypeptide has immunity-inducing activity can be confirmed via, for example, known ELISPOT assay. Specifically, cells such as peripheral blood mononuclear cells are obtained from a living body to which a polypeptide to be assayed for the immunity-inducing activity has been administered, such cells are co-cultured in the presence of such polypeptide, and the production amount of cytokine and/or chemokine, such as IFN-y or interleukin (IL), from the cells is measured with the use of a specific antibody, as described in the Examples below, for example. Thus, the number of immunocytes among the cells can be assayed. This enables evaluation of immunity-inducing activity. [0037] Alternatively, a recombinant polypeptide prepared based on an amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 may be administered to a cancer-bearing animal, so that a tumor can be regressed by the immunity-inducing activity, as described in the Examples below. Thus, the immunity-inducing activity can be evaluated as the capacity for suppressing the growth of cancer cells expressing a polypeptide shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 or the capacity for shrinking or eliminating cancer tissue (tumor) (hereafter, such capacity is referred to as "antitumor activity"). The antitumor activity of the polypeptides can be determined by, for example, actually administering such polypeptide to a cancer-bearing living body and examining whether or not the tumor is shrinked, as specifically described in the Examples below. [0038] Alternatively, whether or not T cells stimulated by the polypeptide (i.e., T cells brought into contact with the antigen-presenting cells that present such polypeptide) exhibit cytotoxic activity on tumor cells in vitro may be examined to evaluate the antitumor activity of the polypeptide. T cells can be brought into contact with antigen-presenting cells via co-culture thereof in a liquid medium as described below. The cytotoxic activity can be assayed via a known technique referred to as the 5ICr-release assay technique described in, for example, Int. J. Cancer, 58: p. 317, 1994. When the polypeptides are used for treatment and/or prevention of cancer, it is preferable that the immunity-inducing activity be evaluated using the antitumor activity as an indicator, although a method of evaluation is not particularly limited. [0039] The amino acid sequences shown by even SEQ ID numbers among SEQ ID NOs: 2 to 30 listed in the Sequence Listing disclosed by the present invention are the amino acid sequences of the CAPRIN-1 polypeptides isolated as the polypeptides binding to the antibodies existing specifically in the serum obtained from cancer-bearing dog and human, bovine, horse, mouse, and chicken homologues of such polypeptides by the SEREX method using the normal canine testicular tissue-derived cDNA library and the serum of a dog afflicted with breast cancer (see Example 1 below). [0040] The polypeptide (a) indicated above is of at least 7 and preferably at least 8, 9, 10 or more contiguous amino acids in a polypeptide having an amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 and has immunity-inducing activity. Particularly preferably, such polypeptide has an amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30. As known in the art, a polypeptide of at least about 7 amino acid residues can exert antigenicity. Accordingly, a polypeptide of at least seven contiguous amino acid residues of the amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 can exert antigenicity and immunogenicity. That is, a polypeptide of at least seven contiguous amino acid residues of the amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 can have immunity-inducing activity, and such polypeptide can be used for preparing the immunity-inducing agent of the present invention. Based on the fact that antibodies produced against an antigenic substance in vivo are polyclonal antibodies, a polypeptide composed of a larger number of amino acid residues can induce a larger variety of antibodies recognizing various sites of the antigenic substance, thereby enhancing the immunity-inducing activity. In order to enhance immunity-inducing activity, accordingly, the number of amino acid residues may be preferably at least 30 or more, or 50 or more, more preferably at least 100 or more, 150 or more, and further preferably at least 200 or more, or still preferably 250 or more. [0041] As the principle of immunity induction via administration of a cancer antigen polypeptide, it is known that a polypeptide is incorporated into an antigen-presenting cell, the polypeptide is degraded by a peptidase in the cell into a smaller fragment (hereafter it may be referred to as an "epitope"), such fragment is presented on the cell surface, cytotoxic T cells or the like recognize such fragment and selectively kill the antigen-presenting cells. The size of a polypeptide presented on the antigen-presenting cell surface is relatively small, and it is about 7 to 30 in terms of the number of amino acids. From the viewpoint of presentation on the antigen-presenting cell, accordingly, it is sufficient that the polypeptide (a) is of about 7 to 30 and preferably about 8 to 30 or 9 to 30 contiguous amino acids in the amino acid sequences shown by any even SEQ ID number among SEQ ID NOs: 2 to 30. Such polypeptide of a relatively small size may be directly presented on the antigen-presenting cell surface without being incorporated into the antigen-presenting cell. [0042] The polypeptide incorporated into the antigen-presenting cell is cleaved at random positions with a peptidase present in the cells, a variety of polypeptide fragments are generated, and such polypeptide fragments are presented on the antigen-presenting cell surface. If a large polypeptide such as a full-length sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 is administered, accordingly, polypeptide fragments that are effective for immunity induction mediated by antigen-presenting cells via degradation in the antigen-presenting cell are naturally generated. Thus, a large-size polypeptide can be preferably used for immunity induction mediated by antigen-presenting cells, and the number of amino acids may be at least 30, more preferably at least 100, further preferably at least 200, and still further preferably at least 250. [0043] Further, the polypeptide of the present invention can be screened for a peptide being a possible epitope with the use of a matching medium that can search for a peptide serving as a possible epitope having a binding motif for each HLA type, such as the HLA Peptide Binding Predictions of Bioinformatics & Molecular Analysis Selection (BIMAS) (http://bimas.dcrt.nih.gov/molbio/hla_bind/index.html). Specifically, a polypeptide of at least seven contiguous amino acids in the region of amino acid residues (aa) 41 to 400 or amino acid residues (aa) 503 to 564 in the amino acid sequences shown by any even SEQ ID number selected from among SEQ ID NOs: 2 to 30 except for SEQ ID NO: 6 and SEQ ID NO: 18 or a polypeptide comprising such polypeptide as a partial sequence thereof is preferable. In the polypeptide of SEQ ID NO: 2, a polypeptide shown by any of SEQ ID NOs: 43 to 76 is more preferable. [0044] The polypeptide (b) above is derived from the polypeptide (a) by substitution, deletion, addition, and/or insertion of a small number of (preferably one or several) amino acid residues, it has 80% or more, 85% or more, preferably 90% or more, more preferably 95% or more, further preferably 98% or more, 99% or more, or 99.5% or more sequence identity with the original sequence, and it has immunity-inducing activity. When a small number of (preferably one or several) amino acid residues are substituted with, deleted from, added to, or inserted into the amino acid sequence of the protein antigen, in general, it is extensively known in the art that the resulting protein occasionally has substantially the same antigenicity or immunogenicity with that of the original protein. Thus, the polypeptide (b) above is capable of exerting the immunity-inducing activity and it can be thus used for preparing the immunity-inducing agent of the present invention. Alternatively, the polypeptide (b) above is preferably a polypeptide having an amino acid sequence derived from the amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 by substitution, deletion, addition, and/or insertion of one or several amino acid residues. The term "several" used herein refers to an integer from 2 to 10, preferably an integer from 2 to 6, and further preferably an integer from 2 to 4. [0045] The term "sequence identity" used herein regarding the amino acid sequence or nucleotide sequence represents a percentage (%) determined by aligning two amino acid sequences (or nucleotide sequences) to be compared so as to maximize the number of matching amino acid residues (or nucleotides) and dividing the number of matched amino acid residues (or the number of matched nucleotides) by the total number of amino acid residues (or the total number of nucleotides). When aligning the sequences as described above, a gap is adequately inserted into one or both of the two sequences to be compared, according to need. Such sequence alignment can be carried out with the use of a well-known program, for example, BLAST, FASTA, or CLUSTAL W (Karlin and Altschul, Proc. Natl. Acad. Sci. U.S.A., 87: 2264-2268, 1993; Altschul et al., Nucleic Acids Res., 25: 3389-3402,1997). When a gap is inserted, the total number of amino acid residues (or the total number of nucleotides) is the number of residues (or the number of nucleotides) counted by designating a gap as an amino acid residue (or a nucleotide). When the total number of amino acid residues (or the total number of nucleotides) thus determined differs between the two sequences to be compared, identity (%) is determined by dividing the number of the matched amino acid residues (or the number of nucleotides) by the total number of amino acid residues (or the total number of nucleotides) of a longer sequence. [0046] A preferable amino acid substituion is a conservative amino acid substition. Twenty types of amino acids constituting a naturally-occurring protein can be classified into groups of amino acids having similar properties: i.e., neutral amino acids having low-polarity side chains (Gly, He, Val, Leu, Ala, Met, and Pro); neutral amino acids having hydrophilic side chains (Asn, Gin, Thr, Ser, Tyr, and Cys); acidic amino acids (Asp, and Glu); basic amino acids (Arg, Lys, and His); and aromatic amino acids (Phe, Tyr, Tip, and His). It is known that substitution within such groups; i.e., conservative substitution, would not alter polypeptide properties in many cases. When amino acid residues in the polypeptide (a) of the present invention are substituted, accordingly, substitution may be carried out within such groups, so that a possibility of maintaining the immunity-inducing activity can be enhanced. In the present invention, however, the altered polypeptide may have non-conservative substitution, provided that the resulting polypeptide has immunity-inducing activity equivalent or substantially equivalent to that of an unaltered polypeptide. [0047] The polypeptide (c) comprises the polypeptide (a) or (b) as a partial sequence thereof and has immunity-inducing activity. Specifically, the polypeptide (c) corresponds to the polypeptide (a) or (b) to which other amino acid(s) or polypeptide(s) are added at one or both ends thereof and having immunity-inducing activity. Such polypeptide can be used for preparing the immunity-inducing agent of the present invention. [0048] The above-mentioned polypeptide can be chemically synthesized in accordance with, for example, the Fmoc (fluorenylmethyloxycarbonyl) method or the tBoc (t-butyloxycarbonyl) method (the Japanese Biochemical Society (ed.), Seikagaku Jikken Kouza (the Course for Biochemical Experiment) 1, Tanpakushitsu no Kagaku (Chemistry of Protein) IV, Kagaku Shushoku to Peptide Gousei (Chemical Modification and Peptide Synthesis), Tokyo Kagaku Dojin, Japan, 1981). Also, a variety of commercially available peptide synthesizers can be used to synthesize the polypeptide in accordance with a conventional technique. Further, known genetic engineering techniques (e.g., Sambrook et al., Molecular Cloning, vol. 2, Current Protocols in Molecular Biology, 1989, Cold Spring Harbor Laboratory Press; and Ausubel et al., Short Protocols in Molecular Biology, vol. 3, A compendium of Methods from Current Protocols in Molecular Biology, 1995, John Wiley & Sons) may be employed to prepare a polynucleotide encoding the above polypeptide, the resulting polypeptide may be incorporated into an expression vector and then introduced into a host cell, and the polypeptide may be produced in such host cell to obtain the target polypeptide. [0049] A polynucleotide encoding the above polypeptide can be easily prepared via a known genetic engineering technique or a conventional technique using a commercially available nucleic acid synthesizer. For example, DNA having the nucleotide sequence of SEQ ID NO: 1 can be prepared by performing PCR with the use of the human chromosome DNA or cDNA library as a template and a pair of primers designed so as to amplify the nucleotide sequence shown by SEQ ID NO: 1. Similarly, DNA having the nucleotide sequence of SEQ ID NO: 5 can be prepared with the use of the canine chromosome DNA or cDNA library as the template. PCR conditions can be adequately determined. For example, a reaction cycle of denaturation at 94°C for 30 seconds, annealing at 55°C for 30 seconds to 1 minute, and extension at 72°C for 2 minutes with the use of thermostable DNA polymerase (e.g., Taq polymerase) and Mg2+-containing PCR buffer is repeated 30 times, followed by the reaction at 72°C for 7 minutes, although the reaction conditions are not limited thereto. PCR techniques, conditions, and the like are described in, for example, Ausubel et al., Short Protocols in Molecular Biology, vol. 3, A compendium of Methods from Current Protocols in Molecular Biology, 1995, John Wiley & Sons (Chapter 15, in particular). Also, adequate probes or primers may be prepared based on the information of the nucleotide sequences and the amino acid sequences shown by SEQ ID NOs: 1 to 30 in the Sequence Listing of the present invention, and human, canine, bovine, or other cDNA libraries may be screened for with the use of such probes or primers, so that DNA of interest can be isolated. cDNA libraries are preferably prepared from cells, organs, or tissue in which a protein shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 is expressed. Procedures, such as preparation of probes or primers, construction of cDNA library, screening of cDNA library, and cloning of target genes, described above are known in the art. For example, such procedures can be carried out in accordance with the methods described in Sambrook et al., Molecular Cloning, vol. 2, Current Protocols in Molecular Biology, 1989), Ausubel et al. (as above). DNA encoding polypeptide (a) above can be obtained from DNA thus obtained. Since a codon encoding each amino acid is known, a nucleotide sequence of a polynucleotide encoding a particular amino acid sequence can be easily identified. Accordingly, the nucleotide sdquence of a polynucleotide encoding polypeptide (b) or (c) can be easily identified, and such polynucleotide can also be easily synthesized with the use of a commercially available nucleic acid synthesizer in accordance with a conventional technique. [0050] The host cells may be any cells, provided that the aforementioned polypeptide can be expressed therein. The host cells include, but not limited to, an E. coli cell as prokaryotic cells; and monkey kidney cells (COS 1), Chinese hamster ovary (CHO) cells, the human embryonic kidney cell line (HEK293), and the fetal mouse skin cell line (NIH3T3), budding yeast cells, dividing yeast cells, silk worm cells, and xenopus egg cells as eukaryotic cells [0051] When prokaryotic host cells are used, expression vectors having, for example, an origin, a promoter, a ribosome-binding site, a multi-cloning site, a terminator, a drug-tolerant gene, and an auxotrophic complementary gene that can be replicated in prokaryotic cells, are used. Examples of E. coli expression vectors include pUC, pBluescriptll, the pET expression system, and the pGEX expression system. DNA encoding the above polypeptide may be incorporated into such expression vector, prokaryotic host cells may be transformed with such vector, and the resulting transformant may be cultured. Thus, a polypeptide encoded by the DNA can be expressed in prokaryotic host cells. In this case, such polypeptide can be expressed in the form of a fusion protein with another protein. [0052] When eukaryotic host cells are used, eukaryotic cell expression vectors having, for example, a promoter, a splicing region, and a poly(A) addition site are used. Examples of such expression vectors include pKAl, pCDM8, pSVK3, pMSG, pSVL, pBK-CMV, pBK-RSV, EBV, pRS, pcDNA3, and pYES2 vectors. As described above, DNA encoding the above polypeptide may be incorporated into such expression vector, eukaryotic host cells may be transformed with such vector, and the resulting transformant may then be cultured. Thus, a polypeptide encoded by the DNA can be expressed in eukaryotic host cells. When pIND/V5-His, pFLAG-CMV-2, pEGFP-Nl, pEGFP-Cl, or other expression vectors are used, the polypeptide can be expressed in the form of a fusion protein with a variety of tags, such as His tag (e.g., (His)6 to (His)io), FLAG tag, myc tag, HA tag, or GFP. [0053] Expression vectors can be introduced into host cells via conventional techniques, such as electroporation, the calcium phosphate method, the liposome method, the DEAE-dextran method, microinjection, virus infection, lipofection, or binding with a cell-permeable peptide. [0054] The target polypeptide can be isolated and purified from host cells by employing known separation techniques in combination. Examples thereof include, but are not limited to, treatment with the use of a denaturing agent such as urea or a surfactant, ultrasonication, enzyme digestion, salting out or fractional precipitation with a solvent, dialysis, centrifugation, ultrafiltration, gel filtration, SDS-PAGE, isoelectric focusing, ion exchange chromatography, hydrophobic chromatography, affinity chromatography, and reverse phase chromatography. [0055] Some polypeptides obtained by such methods are in the form of fusion proteins with any other proteins as described above. Examples thereof include fusioin proteins with glutathione-S-transferase (GST) or His tag. Such polypeptides in the form of fusion proteins are within the scope of the present invention as polypeptide (c). Further, polypeptides expressed in transformed cells are translated, and the translated polypeptides occassionally undergo various types of modification in the cells. Such post-translationally modified polypeptides are also within the scope of the present invention, provided that such polypeptides have immunity-inducing activity. Examples of such post-translational modification include elimination of N-terminal methionine, N-terminal acetylation, sugar chain addition, limited degradation with intracellular protease, myristoylation, isoprenylation and phosphorylation. [0056] As specifically described in the examples below, administration of the above-mentioned polypeptide having immunity-inducing activity to a cancer-bearing living body enables regression of an existing tumor. Thus, the immunity-inducing agent of the present invention can be used as a therapeutic and/or preventive agent for cancer. [0057] The terms "tumor" and "cancer" used herein refer to malignant neoplasms, and these terms are used interchangeably with each other. [0058] In this case, target cancers are those expressing a gene encoding a polypeptide comprising an amino acid sequence shown by any even SEQ ID number among SEQ ID NOs: 2 to 30 or a partial sequence thereof consisting of at least 7 contiguous amino acids. Preferably, such cancers are breast cancer, brain tumor, leukemia, lung cancer, lymphoma, mast cell tumor, esophagus cancer, and colorectal cancer. Examples of such specified cancers include, but are not limited to, mammary gland cancer, combined mammary gland cancer, malignant mixed tumor of the mammary gland, intraductal papillary adenocarcinoma, chronic lymphocytic leukemia, gastrointestinal lymphoma, digestive lymphoma, and small to medium cell lymphoma. [0059] Target animals are mammalians, and examples thereof include mammalian animals, including primates, pet animals, livestock animals, and competitive animals, with humans, dogs, and cats being particularly preferable. [0060] The immunity-inducing agent of the present invention may be administered orally or parenterally to an organism. Parenteral administration, such as intramuscular, subcutaneous, intravenous, or intraarterial administration, is preferable. When such immunity-inducing agent is used for the purpose of cancer treatment, the agent can be administered to the regional lymph node in the vicinity of the tumor to be treated, so as to improve the antitumor effects as described in the examples below. The dose may be any amount as long as it is effective for immunity induction. When the agent is used for treatment and/or prevention of cancer, for example, an amount effective for treatment and/or prevention of cancer is sufficient, and such amount can be altered depending on, for example, the body weight, sex (i.e., male or female), or symptom of an animal. The amount effective for treatment and/or prevention of cancer is adequately determined in accordance with the tumor size, symptoms, or other conditions. In general, an effective amount for a target animal per day is 0.0001 \ig to 1,000 ug, and preferably 0.001 (j.g to 1,000 ug, and the agent can be administered via a single dose or a plurality of doses. Preferably, the agent is administered via several separate doses every several days or months. As specifically described in the examples below, the immunity-inducing agent of the present invention enables regression of an existing tumor. Thus, the agent can exert the antitumor effects on a small number of cancer cells in an early developmental stage. Use thereof before the onset of cancer or after treatment leads to prevention of the development or recurrence of cancer. Specifically the immunity-inducing agent of the present invention is useful for treatment and prevention of cancer. [0061] The immunity-inducing agent of the present invention may consist of a polypeptide, or it may be adequately mixed with an additive that is suitable for a relevant dosage form, such as a pharmaceutically acceptable carrier, a diluent, an excipient, or the like. Methods of preparing an agent and additives that can be used are well-known in the medical preparation field, and any methods and additives can be employed. Specific examples of additives include, but are not limited to: diluents, such as physiological buffer solutions; excipients, such as sugar, lactose, corn starch, calcium phosphate, sorbitol, and glycine; binders, such as syrup, gelatin, gum Arabic, sorbitol, polyvinyl chloride, and tragacanth; and lubricants, such as magnesium stearate, polyethylene glycol, talc, and silica. Examples of forms of preparations include oral agents, such as tablets, capsules, granules, powders, and syrup solutions, and parenteral agents, such as inhalants, injection preparations, suppositories, and liquid drugs. Such agents can be prepared by common methods. [0062] The immunity-inducing agent of the present invention can be used in combination with an immunopotentiating agent capable of potentiating an immunological response in vivo. The immunopotentiating agent may be incorporated into the immunity-inducing agent of the present invention, or it may be administered to a patient as another composition in combination with the immunity-inducing agent of the present invention. [0063] The term "patient" used herein refers to an animal, a mammalian animal in particular, and it is preferably a human, dog, or cat. [0064] An example of the immunopotentiating agent is an adjuvant. An adjuvant provides an antigen reservoir (outside the cell or in the macrophage), it activates the macrophage, and it stimulates lymphocytes in a given tissue. Thus, an adjuvant can potentiate an immunological response and enhance the antitumor effects. When the immunity-inducing agent of the present invention is used for treatment and/or prevention of cancer, accordingly, it is particularly preferable that the immunity-inducing agent further comprise an adjuvant in addition to the polypeptide as an active ingredient. Various types of adjuvants are well-known in the art, and any such adjuvants can be used. Specific examples thereof include: MPL (SmithKline Beecham); an equivalent obtained by purification and acid hydrolysis of a lipopolysaccharide of Salmonella minnesota Re 595; QS21 (SmithKline Beecham); a pure saponin QA-21 purified from the Quillja saponaria extract; DQS21 disclosed in the PCT application (WO 96/33739, SmithKline Beecham); QS-7, QS-17, QS-18, and QS-L1 (So et al., Molecules and Cells, 1997, 7: 178-186); Freund's incomplete adjuvant; Freund's complete adjuvant; vitamin E; Montanide; alum; CpG oligonucleotide (e.g., Kreig et al., Nature, 1995, 374: 546-549); poly IC and a derivative thereof (e.g., poly ICLC); and various water-in-oil emulsions prepared from biodegradable oil, such as squalene and/or tocopherol. Freund's incomplete adjuvant, Montanide, poly I:C, a derivative thereof, and CpG oligonucleotide are particularly preferable. The rate of the adjuvant mixed with a polypeptide is typically about 1:10 to 10:1, preferably about 1:5 to 5:1, and further preferably about 1:1. It should be noted that adjuvants are not limited to those exemplified above, and other adjuvants known in the art can also be used at the time of administration of the immunity-inducing agent of the present invention (e.g., Goding, Monoclonal Antibodies: Principles and Practice, vol. 2, 1986). A method for preparing a mixture of polypeptide and adjuvant or an emulsion is well-known to a person skilled in the field of immunization. [0065] As the immunopotentiating agent, factors that stimulate an immunological response of interest can be used in addition to the aforementioned adjuvants. For example, various cytokines that stimulate lymphocytes or antigen-presenting cells can be used as the immunopotentiating agent in combination with the immunity-inducing agent of the present invention. Many cytokines that can potentiate immunological responses are known in the art. Examples thereof include, but are not limited to, interleukin-12 (IL-12), GM-CSF, IL-18, interferon a, interferon p\ interferon co, interferon y, and Flt3 ligand that are known to potentiate the protective effects of a vaccine. Such factor can be used as the immunopotentiating agent and can be administered to a patient in the form of a mixture thereof with the immunity-inducing agent of the present invention or in combination with the immunity-inducing agent of the present invention as another composition. [0066] Further, the above-mentione,d polypeptides may be brought into contact with antigen-presenting cells in vitro to present such polypeptides to the antigen-presenting cells. Specifically, the polypeptides (a) to (c) can be used as agents for treating the antigen-presenting cells. Examples of antigen-presenting cells include dendritic cells, B cells, and macrophages, and dendritic cells or B cells having MHC class I molecules are preferably used. A variety of MHC class I molecules have been identified and well-known. Human MHC molecules are referred to as "HLA." Examples of HLA class I molecules include HLA-A, HLA-B, and HLA-C. Specific examples include HLA-A1, HLA-A0201, HLA-A0204, HLA-A0205, HLA-A0206, HLA-A0207, HLA-A11, HLA-A24, HLA-A31, HLA-A6801, HLA-B7, HLA-B8, HLA-B2705, HLA-B37, HLA-Cw0401, and HLA-Cw0602. [0067] Dendritic cells or B cells having MHC class I molecules can be prepared from the peripheral blood by a well-known technique. For example, dendritic cells are induced from the bone marrow, umbilical blood, or peripheral blood of a patient with the use of the granulocyte-macrophage colony-stimulating factors (GM-CSF) and IL-3 (or IL-4), and tumor-associated peptides are added to the culture system. Thus, tumor-specific dendritic cells can be induced. [0068] Administration of an effective amount of such dendritic cells enables induction of a response desirable for cancer treatment. Examples of cells that can be used include the bone marrow and the umbilical blood provided by a healthy individual and the bone marrow and the peripheral blood of the patient. When the patient's own autologous cells are used, a safety level is high, and serious side effects can be avoided. The peripheral blood or bone marrow may be a fresh, hypothermically stored, or cryopreserved sample. The peripheral blood may be prepared by culturing the whole blood or by culturing the separated leukocyte components, with the latter being preferable from the viewpoint of efficiency. Further, mononuclear cells may be isolated from the leukocyte components. When the sample is prepared from the bone marrow or umbilical blood, the entire cells that constitute the bone marrow may be cultured, or mononuclear cells may be separated therefrom and cultured. The peripheral blood, the leukocyte component thereof, and the bone marrow cells comprise mononuclear cells, hematopoietic stem cells, immature dendritic cells, or CD4+ cells from which dendritic cells originate. Cytokines may be of a naturally-occurring or gene recombinant type, and methods for producing the same are not limited, provided that safety and physiological activities thereof have been verified. Preferably, the minimum requirement of samples with verified medical qualities is used. The concentration of cytokine added is not particularly limited, provided that dendritic cells are induced. In general, the total cytokine concentration of approximately 10 to 1,000 ng/ml is preferable, and about 20 to 500 ng/ml is further preferable. Culture can be conducted with the use of a well-known medium that is generally used for leukocyte culture. A culture temperature is not particularly limited, provided that leukocytes can be multiplied, and the human body temperature (i.e., approximately 37°C) is the most preferable. A gaseous environment during culture is not particularly limited, provided that leukocytes can be multiplied. Aeration with 5% CO2 is preferable. Further, a culture duration is not particularly limited, provided that a nucessary number of cells is induced. It is generablly 3 days to 2 weeks. An adequate apparatus can be used for cell separatioin or culture, and it is preferable that such apparatus have the approved medical safety and stable and simple operability. In particular, cell culture apparatuses are not limited to common containers, such as petri-dishes, flasks, and bottles, and laminated or multistage containers, roller bottles, spinner bottles, bag-type culture apparatus, hollow fiber columns, or the like can also be used. [0069] The above-mentioned polypeptides can be brought into contact with antigen-presenting cells in vitro via a well-known technique. For example, antigen-presenting cells can be cultured in a coluture solution containing such polypeptides. Peptide concentration in a medium is not particularly limited. In general, it is about 1 to 100 |ig/ml, and preferably about 5 to 20 ug/ml. Cell density during culture is not particularly limited, and it is generally about 10 to 10 cells/ml, and preferably about 5 x 104 to 5 x 106 cells/ml. It is preferable that culture be conducted at 37°C in 5% CO2 in accordance with a conventional technique. A peptide length that can be presented on the antigen-presenting cell surface is generally about 30 amino acid residues at maximum. When antigen-presenting cells are brought into contact with polypeptides in vitro, accordingly, the length of the polypeptide may be adjusted to about 30 amino acid residues or less, although the length is not particularly limited thereto. [0070] By culturing antigen-presenting cells in the presence of the polypeptides, peptides are incorporated into MHC molecules of the antigen-presenting cells and presented on the surfaces thereof. Thus, the isolated antigen-presenting cells containing the complex of polypeptides and MHC molecules can be prepared with the use of such polypeptides. Such antigen-presenting cells can present the polypeptides to T cells in vivo or in vitro, induce cytotoxic T cells specific for the polypeptides, and multiply such T cells. [0071] The thus-prepared antigen-presenting cells containing the complex of polypeptides and MHC molecules may be brought into contact with T cells in vitro, so that cytotoxic T cells specific for such polypeptides can be induced and multiplied. It can be achieved by culturing the antigen-presenting cells together with the T cells in a liquid medium. For example, culture can be conducted by suspending antigen-presenting cells in a liquid medium, introducing the resulting suspension into a container such as wells of a microplate, and adding T cells thereto. The mixing ratio of antigen-presenting cells to T cells at the time of coculture is not particularly limited, and it is generally about 1:1 to 1:10, and preferably about 1:5 to 1:20 in terms of the cell count. Also, the density of antigen-presenting cells suspended in a liquid medium is not particularly limited, and it is generally about 100 to 107 cells/ml, and preferably about 104 to 106 cells/ml. Co-culture is preferably carried out in accordance with a conventional technique at 37°C in 5% CO2. A culture duration is not particularly limited, and it is generally 2 days to 3 weeks, and preferably about 4 days to 2 weeks. It is preferable that coculture be carried out in the presence of a single type or a plurality of types of interleukins, such as IL-2, IL-6, IL-7, and IL-12. In such a case, IL-2 or IL-7 concentration is generally about 5 U/ml to 20 U/ml, IL-6 concentration is generally about 500 U/ml to 2,000 U/ml, and IL-12 concentration is generally about 5 ng/ml to 20 ng/ml, although the concentration is not limited thereto. The unit "U" used herein indicates a unit of activity. Co-culture may be repeated once or several times with the addition of fresh antigen-presenting cells. For example, the culture supernatant after coculture is discarded, coculture is further carried out with the addition of a suspension of fresh antigen-presenting cells, and such procedure may be repeated once or several times. Coculture conditions may be as described above. [0072] Cytotoxic T cells specific for the polypeptides are induced and multiplied via the co-culture. Thus, isolated T cells that selectively bind to the complex of polypeptides and MHC molecules can be prepared with the use of the above polypeptides. [0073] As described in the Examples below, genes encoding polypeptides of any even SEQ ID number among SEQ ID NOs: 2 to 30 are expressed specifically in the breast cancer cells, the leukemia cells, and the lymphoma cells. Accordingly, it is considered that a significantly larger number of polypeptides of even SEQ ID numbers among SEQ ID NOs: 2 to 30 are present in such cancer cells than in normal cells. When some polypeptides in cancer cells are presented to the MHC molecules on the cancer cell surface and the cytotoxic T cells prepared as described above are administered into a living body, cytotoxic T cells can disrupt cancer cells using the same as a marker. Since the antigen-presenting cells presenting the polypeptides are capable of inducing and multiplying cytotoxic T cells specific for the polypeptides in vivo, administration of the antigen-presenting cells into a living body can also disrupt cancer cells. That is, the cytotoxic T cells prepared with the use of the polypeptides or the antigen-presenting cells are useful as the therapeutic and/or preventive agent for cancer as with the immunity-inducing agent of the present invention. [0074] When the isolated antigen-presenting cells or isolated T cells are administered to a living body, it is preferable that such isolated cells are prepared from the antigen-presenting cells or T cells sampled from the patient who receives the treatment with the use of the polypeptides (a) to (c) in order to avoid an immunological response that recognize such cells as foreign matter and attacks such cells in vivo. [0075] The route of administration of a therapeutic and/or preventive agent for cancer comprising, as an active ingredient, the antigen-presenting cells or isolated T cells is preferably a parenteral route, such as intravenous or intraarterial administration. A dosage is adequately selected in accordance with the symptom, the purpose of administration, and other conditions, and in general, 1 to 1013 cells, and preferably 106 to 109 cells are used for administration, and such cells are preferably administered once every several days or several months. A preparation may be, for example, a suspension of cells in a physiological buffered saline solution, and it can be used in combination with other antitumor agents or cytokines. Also, one or more additives well-known in the medical preparation field can be added. [0076] Polynucleotides encoding the polypeptides (a) to (c) may be expressed in the body of a target animal, so that antibody production or cytotoxic T cells can be induced in the body, and effects equivalent to those attained via polypeptide administration can be attained. Specifically, the immunity-inducing agent of the present invention may comprise polynucleotides encoding the polypeptides (a) to (c) and comprise, as an active ingredient, a recombinant vector capable of expressing such polypeptide in vivo. Such recombinant vector capable of expressing an antigen polypeptide is also referred to as a "gene-based vaccine." [0077] A vector used for preparing a gene-based vaccine is not particularly limited, provided that it can express polypeptides of interest in the target animal cells (preferably mammalian animal cells). It may be a plasmid or virus vector, and any vector known in the gene-based vaccine field may be used. Polynucleotides, such as DNA or RNA encoding the polypeptides, can be easily prepared in accordance with a conventional technique as described above. Also, the polynucleotides can be incorporated into a vector by a method well-known in the art. [0078] Preferably, a gene-based vaccine is administered parenterally (e.g., intramuscular, subcutaneous, intravenous, or intraarterial administration), and the dosage can be adequately selected in accordance with an antigen type or other conditions. A dosage is generally about 0.1 ug to 100 mg, and preferably about 1 jj.g to 10 mg, in terms of the weight of the gene-based vaccine per kg of the body weight. Examples of methods involving the use of virus vectors include methods in which the polynucleotide encoding the above polypeptide is incorporated into the RNA virus or DNA virus, such as retrovirus, lentivirus, adenovirus, adeno-associated virus, herpes virus, vaccinia virus, poxvirus, polio virus, or Sindbis virus, and the target animal is infected therewith. Methods involving the use of retrovirus, adenovirus, adeno-associated virus, or vaccinia virus are particularly preferable. [0080] Examples of other methods include a method in which an expression plasmid is directly administered into the muscle (the DNA vaccine method), the liposome method, the Lipofectin method, microinjection, the calcium phosphate method, and electroporation, with the DNA vaccine method and the liposome method being particularly preferable. [0081] The gene encoding the polypeptide used in the present invention is actually allowed to function as a pharmaceutical product by the in vivo method in which the gene is introduced directly into the body or the ex vivo method in which a given cell is sampled from a target animal, the gene is introduced into the cell ex vivo, and the cell is then returned into the body (Nikkei Science (the Japanese version of Scientific American), April 1994, pp. 20-45, Japan; Gekkan Yakuji (the Pharmaceuticals Monthly), 1994, vol. 36, No. 1, pp. 23-48, Japan; Jikken Igaku Zoukan (an extra number of Experimental Medicine), 1994, vol. 12, No. 15, Japan; and cited documents thereof). The in vivo method is more preferable. [0082] When a pharmaceutical agent is administered via the in vivo method, the agent can be administered through an adequate route in accordance with diseases, symptoms, and ohter conditions of the target of treatment. For example, administration can be carried out intravenously, intraarterially, subcutaneously, or intramuscularily. When the agent is administered via the in vivo method, for example, the agent can be in the form of a liquid drug. In general, the agent is in the form of an injection preparation containing DNA encoding the peptide of the present invention as an active ingredient, and common carriers may be added according to need. Also, the liposome or membrane fusion liposome (e.g., hemagglutinating virus of Japan (HVJ)-liposome) comprising the DNA can be in the form of a liposome preparation such as a suspension, cryogen, or cryogen condensed by centrifugation. [0083] In the present invention, the term "the nucleotide sequence shown by SEQ ID NO: 1" refers not only to the nucleotide sequence that is actually shown by SEQ ID NO: 1 but also a sequence complementary thereto. Accordingly, the term "a polynucleotide having the nucleotide sequence shown by SEQ ID NO: 1" refers to a single-stranded polynucleotide having the nucleotide sequence that is actually shown by SEQ ID NO: 1, a single-stranded polynucleotide comprising a nucleotide sequence complementary thereto, and a double-stranded polynucleotide comprised of such single-stranded polynucleotides. When preparing a polynucleotide encoding the polypeptide used in the present invention, an adequate nucleotide sequence is to be selected. A person skilled in the art would readily select such adequate sequence. Examples [0084] Hereafter, the present invention is described in greater detail with reference to the Examples, although the technical scope of the present invention is not limited to the concrete examples below. [0085] Example 1: Acquisition of novel cancer antigen protein by the SEREX method (1) Preparation of cDNA library Total RNA was extracted from the testicular tissue of a healthy dog by the acid guanidium-phenol-chloroform method, and poly(A) RNA was purified with the use of the Oligotex-dT30 mRNA purification Kit (Takara Shuzo Co., Ltd.) in accordance with the protocols included in the kit. [0086] The canine testis cDNA phage library was synthesized using the obtained mRNA (5 ug). The cDNA phage library was prepared using the cDNA Synthesis Kit, theZAP-cDNA Synthesis Kit, and the ZAP-cDNA Gigapacklll Gold Cloning Kit (STRATAGENE) in accordance with the protocols included in the kits. The size of the prepared cDNA phage library was 7.73 x 105 pfu/ml. [0087] (2) Screening of cDNA library with the use of serum Immunoscreening was carried out using the canine testis cDNA phage library prepared above. Specifically, host E. coli cells (XLl-Blue MRF') was infected with the phage library in 2,210 clones per a NZY agarose plate (