PROPHYLAXIS OF MAMMARY NEOPLASIA BY SELENIUM SUPPLEMENTATION IN THE INITIATION AND PROMOTION PHASES OF CHEMICAL CARCINOGENESIS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 41  (11) , 4386-4390
Abstract
The chemopreventive effect of dietary Se supplementation in the initiation or promotion phase of 7,12-dimethylbenz[a]anthracene-induced mammary carcinogenesis was studied in rats fed a high-fat diet. Control animals received 0.1 ppm of Se (as sodium selenite); experimental groups were supplemented with 5 ppm of selenium for various periods of time as follows: -2 to +24, -2 to +2, +2 to +24, +2 to +12, +12 to +24 and -2 to +12. The time of 7,12-dimethylbenz[a]anthracene administration (50 days of age) was taken as Time 0; minus and plus signs represent the time in weeks before and after 7,12-dimethylbenz[a]anthracene administration, respectively. Apparently Se can inhibit both the initiation and promotion phases of carcinogenesis; a continuous intake of Se is necessary to achieve maximal inhibition of tumorigenesis; the inhibitory effect of Se in the early promotion phase is probably reversible; and the efficacy of Se is attenuated when it is given long after carcinogenic injury. The effectiveness of Se in inhibiting the reappearance of mammary tumors that had regressed after ovariectomy was also assessed. By supplementing tumor-bearing animals with 5 ppm of Se in the diet immediately after endocrine ablation, tumors reappeared at a slower rate compared to the controls. Se is not only effective in chemoprevention but probably can also be used as an adjuvant chemotherapeutic agent.