DNA repair and cytokines in antimutagenesis and anticarcinogenesis.

UV is a complete carcinogen because it can induce skin cancer by sequential steps of initiation, promotion and progression. It produces the mutagenic DNA photoproducts that lead to activation of skin oncogenes, and also suppresses the cellular immune responses that are otherwise able to eliminate highly antigenic skin tumors. What is new is that these two steps are related because unrepaired DNA photoproducts cause the release of cytokines, producing a variety of response that contribute to tumor promotion, tumor progression, immunosuppression, and the induction of latent viruses. DNA repair enzymes are a key genoprotection mechanism not only by reversing DNA photoproducts, but also by blocking the carcinogenic cellular responses triggered by cytokines.