AbstractTo identify CTL‐directed antigens in gastrointestinal cancer, we have investigated antigens recognized by the HLA‐A2‐restricted CTL line established from T cells infiltrating into colon cancer and report herein cleavage and polyadenylation specificity factor (CPSF) as a potent antigen holding peptides capable of inducing CTLs. Five peptides at amino acid positions 250–258, 392–400, 534–542, 1296–1304 and 1359–1368 of CPSF, which were recognized by the CTL line, were found to have the ability to induce HLA‐A2‐restricted and tumor‐specific CTLs in peripheral blood mononuclear cells of the majority (69%, 11/16) of gastrointestinal cancer patients with different HLA‐A2 subtypes. Thus, these peptides might be appropriate molecules for use in the peptide‐based specific immunotherapy of HLA‐A2+ patients with gastrointestinal cancers. © 2002 Wiley‐Liss, Inc.