Identification of peptides applicable as vaccines for HLA-A26-positive cancer patients.

One-fifth of the Japanese population is positive for HLA-A26, but few peptides are available as potential cancer vaccines for HLA-A26-positive cancer patients. The objective of this study was to identify peptide vaccine candidates for HLA-A26-positive cancer patients. The HLA-A*2601-crossbinding activity of 24 peptides currently under clinical trial as vaccines for HLA-A2, -A24, or HLA-A3 supertype-positive cancer patients was evaluated by stabilization assay. Three peptides with HLA-A2-binding activity could bind the HLA-A*2601 molecule. These three peptides induced HLA-A26-restricted cytotoxic T lymphocytes from HLA-A*2601-, -A*2602-, or -A*2603-positive prostate cancer patients against HLA-A*2601- and HLA-A*2603-positive cancer cells in CD8-dependent and peptide-specific manners. In addition, one peptide with HLA-A24-binding activity could bind to HLA-A*2601 and induced HLA-A26-restricted cytotoxic T lymphocytes from HLA-A*2601-, -A*2602-, or -A*2603-positive prostate cancer patients against HLA-A*2603-positive cancer cells. These results may provide novel information for the development of a peptide-based cancer vaccine for HLA-A26-positive patients.