Identification of human tumor antigens and immunotherapy

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Our studies indicated that 1) inhibitors of apoptosis (IAP) protein were expressed preferentially in neoplastic cells but not in normal tissues. Such IAP, particulary, survivin-and livin-derived HLA-A24-restricted peptides could be immunogenic to cancer patients. 2) Recoverin protein that normally expresses in retina was also detected in more than 50 % of cancer cells and cancer tissues. Recoverin-derived HLA-A24-restricted peptide could also specifically induce CTL in the cancer patients of various tissue origins. 3) SYT-SSX chromosomal translocation (X;18) fusion protein was expressed specifically in approximately 95 % of synovial sarcomas. This protein-derived HLA-A24-restricted peptide could induce antigen-specific CTL, and tetramer study suggested that the precursor of these CTL was detected more frequently in patients with lung metastasis of this tumor. These data implied that above peptides may be useful in human cancer immunotherapy.We also assessed the role of molecular chaperone, hsc73, in the transport of antigenic peptide into the ER. The data indicated that N-terminus-extended peptides that showed high, but not low, affinity to hsc73 could enter into the ER. This observation is important in determining tumor vaccines, because hsc73-binding peptides may be preferentially associated with MHC class I molecules.