Human tumor antigens recognized by T lymphocytes: Implications for cancer therapy

The adoptive transfer of cytotoxic T lymphocytes (CTLs) derived from tumor-infiltrating lymphocytes (TIL) along with interleukin-2 (IL-2) into autologous patients with cancer resulted in the objective regression of tumor, indicating that these CTLs recognized cancer rejection antigens on tumor cells. In the past year, a number of such tumor antigens were isolated by the use of cDNA expression systems and biochemical approaches. The majority of tumor antigens identified to date have been found to be nonmutated, self proteins. This raises important questions regarding the mechanism of antitumor activity and autoimmune disease. Several tumor-specific mutated tumor antigens have also been recently identified, which include cell cyclin-dependent kinase 4 (CDK4) and β-catenin. For the first time, a novel human cancer antigen was recently found to be generated by the use of an alternative open reading frame of the previously identified tyrosinase-related protein-1 (TRP-1) gene. The identification of human tumor rejection antigens provides new opportunities for the development of therapeutic strategies against cancer. The potential clinical applications of these tumor antigens will be discussed.