Prostate‐specific antigen‐derived epitopes capable of inducing cellular and humoral responses in HLA‐A24+ prostate cancer patients

BACKGROUND: We tried to identify prostate-specific antigen (PSA)-derived epitopes immunogenic in HLA-A24+ prostate cancer patients. METHODS: Peripheral blood mononuclear cells (PBMCs) were in vitro stimulated with each of four different PSA peptides carrying the HLA-A24 binding motif, and their HLA-A24-restricted anti-tumor responses were examined using a parental HLA-A24-negative prostate cancer cell line (PC93) and its HLA-A24-expressing transfectant line (PC93-A24). Serum levels of immunoglobulin G (IgG) against PSA peptides were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: PBMCs, which were in vitro stimulated with either the PSA(152-160) or PSA(248-257) peptide, showed higher levels of IFN-gamma production and cytotoxicity against the PC93-A24 than against the PC93. IgG against the PSA(248-257) peptide was detected in half of the prostate cancer patients tested. CONCLUSIONS: The PSA(152-160) and PSA(248-257) peptides could be appropriate target molecules in use for specific immunotherapy of HLA-A24+ prostate cancer patients.