Expression of the SART1 tumor-rejection antigen in hepatocellular carcinomas

We previously reported a tumor-rejection antigen, SART1(259), possessing tumor epitopes capable of inducing cytotoxic T lymphocytes (CTL) in epithelial cancer patients. The present study investigated the expression of the SART1(259) antigen in hepatocellular carcinomas (HCC) in order to explore for a potential molecule for use in specific immunotherapy of HCC patients. Expression of the SART1 antigens in samples was analyzed by Western blot analysis with anti-SART1(259) and anti-SART1(800) polyclonal antibodies. In addition HLA-A24(-) restricted CTLs were induced from peripheral blood mononuclear cells (PBMCs) of HLA-A24(+) HCC patients by the SART1(690-698) (EYRGFTQDF) peptide with an HLA-A24 binding motif. The SART1(259) antigen was detected in the cytoplasmic fraction of 6 of 8 HCC cell lines and 12 of 23 (52%) HCC tissues, but in none of the normal liver tissues or those of chronic hepatitis or cirrhosis. The HLA-A24 restricted and SART1-specific CTLs recognized the HLA-A24(+) and SART1(259)+ HCC cells. Further, in peripheral blood mononuclear cells of HCC patients, the SART1(690-698) peptide induced CTLs that reacted to the HCC cells in an HLA-A24(-)restricted manner. These results suggest that the SART1(259) antigen could be an appropriate target molecule for use in specific immunotherapy of HCC patients.