Identification of human melanoma antigens recognized by tumor infiltrating T lymphocytes and their use for immunotherapy

Adoptive transfer of cultured tumor infiltrating T-lymphocytes (TIL) with interleukin 2 (IL2) resulted in tumor regression in melanoma patients, indicating the important role of T-cells in mediating in vivo melanoma regression. TIL secrete cytokines and lyse tumor cells in vitro by recognizing autologous melanoma. Using cDNA expression cloning methods with these TIL, cDNAs encoding melanoma antigens including 5 melanosomal proteins (MART-1, gp100, tyrosinase, TRP1, and TRP2), p15 and β-catenin, were identified. Non-mutated and mutated T cell epitopes have also been identified. A variety of mechanisms to generate these T cell epitopes on melanoma has been identified including peptides derived from regular open reading frames (ORFs), an alternative ORF, introns, or sequences with a mutation. Some melanoma epitopes had relatively low major histocompatibility complex (MHC) binding affinities, suggesting that these were subdominant self epitopes. Several MART-1 and gp100 epitopes were recognized by TIL from many patients, suggesting that these were immunodominant common epitopes. By in vitro stimulation with these identified epitopes, melanoma reactive cytotoxic T lymphocytes (CTL) could be efficiently induced from peripheral blood lymphocytes (PBL) or TIL of melanoma patients. Since adoptive transfer of the TIL reacting to these melanoma antigens into autologous patients with IL2 resulted in tumor regression, these peptides may function as tumor rejection antigens. Tumor regression correlated with vitiligo development after IL2 based immunotherapies in melanoma indicating that these epitopes may also be present on the surface of melanocytes in vivo and that autoreactive T-cells may be involved in the tumor regression. A variety of Phase I clinical trials including immunization with the MART-1 and gp100 peptides, or recombinant viruses containing the MART-1 or gp100 gene, with or without administration of cytokines such as IL2, granulocyte macrophagecolony stimulating factor (GM-CSF), IL12, is being conducted in the Surgery Branch of the National Cancer Institute (NCI), and tumor regression has been observed in some patients.