Cytotoxic T lymphocyte therapy of cancer and tumor escape mechanisms.

In animal models complete and permanent eradication of tumors can be achieved by adoptive transfer of tumor specific T cells, combined with interleukin 2. The most active cells are CD8+ cytotoxic T lymphocytes (CTL), which recognize peptides of 8-10 amino acids in length, bound to the antigen presenting groove of MHC class I molecules. In the case of virus-induced tumors these peptides are processed from viral proteins. Potentially immunogenic human tumors include melanoma and renal cell carcinoma in addition to the virus-associated cancers Burkitt's lymphoma and cervical carcinoma. The potential of CTL therapy of human cancer needs to be tested with cloned tumor cells. Remedies to over-come poor immunogenicity and evasion by tumor cells of CTL mediated-destruction are discussed.