Abstract

Selenium is a known cancer chemopreventive agent owing to its antitoxic nature and antitumorigenic effect. In this study the cytocidal response of sodium selenite on MCF-7 human breast adenocarcinoma cells was examined. After 48 h the number of cells in culture containing high concentration of selenium i.e. 10 and 25 mM decreased by 35% and 70% respectively, but at low concentrations i.e. 1 mM and 5 mM, their number increased by 10% and 15%, respectively. Growth stimulatory concentrations of selenium resulted in significant stimulation of polyamine levels. Significant increase in glutathione levels was also observed with 5 mM of selenium. Growth inhibitory concentrations of selenium resulted in inhibition of polyamine levels. Increase in glutathione content was much less with 10 mM selenium when compared with 5 mM of selenium. Regulation of polyamine biosynthesis by selenium could be due to the action of selenium on thiol groups which in turn are required for the activity of ornithine decarboxylase. Selenium resulted in inhibition of DNA synthesis as observed by cell cycle analysis and higher concentration of selenium resulted in DNA fragmentation.