Selenium-mediated inhibition of 7,12-dimethylbenz[a]anthracene-induced mouse mammary tumorigenesis.

The effect of supplemental selenium on 7,12-dimethylbenz[a] anthracene (DMBA)-induced mammary tumorigenesis was investigated in several mouse strains. Selenium, administered as SeO2 in the drinking water, inhibited mammary tumor formation in DMBA-treated (C57BL x DBA/2f)F1, C3H/StWi and BALB/c female mice. In addition, selenium inhibited the occurrence of DMBA-induced ductal hyperplasias in (C57BL x DBA/2f)F1 and BALB/c mice and mammary tumour virus-induced alveolar hyperplasias in BALB/cfC3H mice. Selenium did not alter the growth of established mammary tumors. These results demonstrate that supplemental selenium inhibits both chemical-and viral-induced mouse mammary tumorigenesis, and secondly, that the development of preneoplastic lesions, an early stage in mammary tumorigenesis, is very sensitive to selenium-mediated inhibition.