Colon carcinogenesis: an overview.

The mechanisms for activation of procarcinogens and some of the factors that affect these reactions are considered. It is proposed that the nucleus of the colonic cell may actually be responsible for the formation of ultimate carcinogenic forms of exogenous procarcinogens. The contributions of the intestinal microbial flora to activation and detoxification of the carcinogens are discussed, and the suggestion that inactive glucuronides of procarcinogens are hydrolyzed to proximate carcinogens by the microbial flora is proposed. Finally, the two-stage mechanism for carcinogenesis is discussed; large bowel cancer is the focal point.