A practical prescription for cancer prevention--synergistic use of chemopreventive agents

Selenium Toxicity in Animals with Emphasis on Man

This review was undertaken to establish what might be the maximum safe dose of selenium that could be administered to man in studies on the use of the element in cancer prevention. The early history of selenium poisoning is briefly summarized. The literature on clinical signs and toxicity data for acute and for chronic selenosis in farm and experimental animals is discussed. Several cases of acute selenosis in man are reviewed, and a number of reports on chronic selenosis in man are reviewed and evaluated. Based on these, the maximum safe single oral dose of selenite, selenate, DL-selenocysteine, or DL-selenomethionine is suggested as 0.05 mg Se/kg body weight (milligrams of selenium per kilogram of body weight). The maximum safe multiple oral dose is suggested as 5 μg Se/kg body weight.

Chemoprevention of tongue carcinogenesis in rats

The inhibitory effects of vitamin A, selenium, butylated hydroxytoluene, and their combinations on tongue carcinogenesis induced by 4-nitroquinoline 1-oxide were examined in Sprague-Dawley rats. After 4 months of administration of 4-nitroquinoline 1-oxide, a wide range of lesions from hyperplasia to early invasive carcinoma was seen. The lesions were fewer and the carcinomas were less advanced in the rats given preventive treatment. The chemopreventive effect of vitamin A plus butylated hydroxytoluene was most effective. After 7 months of 4-nitroquinoline 1-oxide administration, the incidence, the macroscopic diameter, and the microscopic depth of invasion among carcinomas were smaller in the chemopreventive groups than in the nonchemopreventive group. We conclude that vitamin A, selenium, and butylated hydroxytoluene inhibit tongue carcinogenesis induced by 4-nitroquinoline 1-oxide in rats. The inhibitory effect of combined chemopreventives is not always superior to that of each chemopreventive agent used alone.