Expression of tumor rejection antigens in colorectal carcinomas

BACKGROUND The authors recently reported that the SART2 and SART3 antigens encode tumor epitopes recognized by HLA-A24-restricted and tumor-specific cytotoxic T lymphocytes (CTLs) established from esophageal carcinoma patients. The current study investigated these antigens to explore a potential molecule for specific immunotherapy for colorectal carcinoma patients. METHODS The SART2 and SART3 antigens were investigated by Western blotting in colorectal carcinoma cell lines and in cancer tissues. For induction of CTLs, peripheral blood mononuclear cells (PBMCs) of HLA A-24-positive cancer patients were stimulated in vitro with peptides. RESULTS The 140 kD SART3 antigen was expressed in both the cytosol and nuclear fractions of all six colon carcinoma cell lines, 27 of 41 (65.9%) cytosol fractions, 30 of 41 (73.2%) nuclear fractions of colorectal carcinoma tissue samples, and in 0 of 7 non-tumorous tissues. The 100 kD SART2 antigen was expressed in the cytosol fractions of 2 of 6 colon carcinoma cell lines, 5 of 20 (25%) cytosol fractions of colorectal carcinoma tissue samples, and in 0 of 7 non tumorous tissues. HLA-A24-restricted CTLs cytotoxic to colon carcinoma cells were induced from PBMCs of colon carcinoma patients by stimulation with the two immunogenic peptides of SART3. CONCLUSIONS The SART3 antigen could be an appropriate target molecule for specific immunotherapy for colorectal carcinoma patients. Cancer 2002;94:1636–41. © 2002 American Cancer Society. DOI 10.1002/cncr.10421