The present studies were designed to examine the influence of dietary selenite supplementation on the initiation phase of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis and to correlate selenite-induced changes in the binding of DMBA metabolites to rat mammary cell DNA with the ultimate tumor incidence. Diets formulated to contain selenium, as sodium selenite at 0.1, 0.5, 1, 2, or 4 µg/g were fed for 2 weeks prior to and 2 weeks following treatment with DMBA (5 mg/kg body weight). Food intake and weight gain did not differ among treatments. Tumor incidence correlated inversely to the quantity of selenium consumed (r = -0.99). Final tumor incidences were 52, 32, 24, 14, and 10% for rats fed 0.1, 0.5, 1, 2, and 4 µg selenium/g, respectively. In a separate group of rats fed a diet containing 4 µg selenium/g during both the initiation and promotion stages the final tumor incidence was 4.8%. Selenite supplementation for 2 weeks markedly depressed the occurrence of individual and total DMBA-DNA adducts. The final mammary tumor incidence correlated positively with total DMBA-DNA adducts (r = 0.99). These studies clearly demonstrate that selenite can inhibit the initiation stage of mammary carcinogenesis. This reduction in tumor incidence is likely due to a reduction in carcinogen metabolism and ultimately adduct formation.
↵1 Supported in part by NIH Grant CA44567. Presented in part at the 14th International Congress of Nutrition, Seoul, Korea, 1989, and in part at the Annual Meeting of the Federation of the American Society of Experimental Biology, Washington, D.C., 1990 (FASEB J., 4: A1042, 1990).
↵2 To whom requests for reprints should be addressed, at Department of Nutrition, 126 Henderson Building South, The Pennsylvania State University, University Park, PA 16802.
- Received April 3, 1991.
- Accepted June 14, 1991.
- ©1991 American Association for Cancer Research.