EFFECTS OF METHOXYCHLOR ON SKIN TUMOR-DEVELOPMENT

Organochlorine pesticides increase the incidence of liver cancer throu gh a multistage process involving tumor promotion. Mirex, an organochl orine pesticide has been shown to be a tumor promoter in mouse skin. I n the present study, the effects of methoxychlor, a commonly used orga nochlorine pesticide, on the development of papillomas in 7,12-dimethy l-benz[a]anthracene (DMBA)-initiated mouse skin and induction of mouse epidermal ornithine decarboxylase (ODC) activity were investigated an d compared with 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a well-kn own tumor promoter. Methoxychlor neither caused tumor development nor induced epidermal ODC activity, However, TPA resulted in l00% tumor in cidence and 8.8 tumors per mouse after 20 weeks of promotion, and indu ced epidermal ODC activity,