Androgens as promoters of colon carcinogenesis

The effects of androgens on colon carcinogenesis were studied in 90 male Fisher-344 rats, given 10 weekly subcutaneous (SC) injections of 7.5 mg azoxymethane (AOM)/kg body weight, starting at 12 weeks of age. Thirty rats received the AOM course only (AOM only). Thirty rats were gonadectomized at 10 weeks of age and underwent the AOM course (castrated). In 30 additional castrated rats, hormone substitution was achieved by sc injection of 1 mg dehydrotestosterone (DHT) three times a week for 12 weeks. AOM was given concommitantly, starting at 12 weeks of age (castrated and hormone substituted). Animals were sacrificed 25 weeks after first AOM injection. As assessed by weekly body weight data and periodic serum determinations of carcinoembryonic antigen (CEA), castrated animals showed a delayed onset of colonic carcinogenesis, compared to AOM-only-treated and hormone-substituted animals. Castration resulted in a decrease of mean tumor size as well as overall incidence of colonic tumors, compared to that observed AOM-only and castrated and hormone-substituted group, respectively (27 vs 47 vs 53%). Castration also resulted in lower mean serum CEA levels at the end of experiment than in the AOM-only and castrated and hormone-substituted group. These findings suggest a promoting effect of androgens in colon carcinogenesis.