Modulation of tumor incidence and possible mechanisms of inhibition of mammary carcinogenesis by dietary antioxidants.

The interaction of effects of various levels and types of dietary fat and antioxidants on 7,12-dimethylbenz(alpha)anthracene- and nitrosomethylurea-induced mammary gland carcinogenesis has been studied. Dramatic differences were noted with respect to dietary fat effects as has been reported previously by others as well as ourselves. A dependence upon dietary fat type and amount, as well as upon whether diets are undefined laboratory chows or semipurified diets, is examined with regard to the effectiveness of antioxidants as tumor-inhibitory agents. The possible role and function of "antioxidants" as a class of compounds in chemical as well as the more complex biological system are discussed. A brief summary of the effectiveness of specific antioxidants in various tumor models as well as sex differences is presented, with a concluding discussion of possible strategies for obtaining information on the mechanism by which various dietary substances with antioxidant properties may inhibit tumorigenesis.