COMPARISON OF THE EFFECTS OF AN ORGANIC AND AN INORGANIC FORM OF SELENIUM ON A MAMMARY-CARCINOMA CELL-LINE

The development of new compounds,vith greater cancer inhibitory activi ty and that are well tolerated continues to be a priority in chemoprev ention research involving selenium. One compound, 1,-4-phenylene-bis(m ethylene)selenocyanate (p-XSC), is representative of a series of organ oselenium compounds with these characteristics. Tn this study, the eff ects of p-XSC on a mouse mammary carcinoma cell line were compared to those of sodium selenite, which has been shown to be growth inhibitory . Treatment with p-XSC caused a 3- to 6-fold greater accumulation of s elenium within cells than did treatment with equivalent amounts of sel enite and cells were able to better tolerate higher cellular levels of selenium derived from p-XSC. Both compounds resulted in a dose-depend ent reduction in cell number after 24 h of exposure. Selenite and p-XS C also caused a dose-dependent increase in cell death by apoptosis. Th is effect was observed within 5 h of treatment. The effect of p-XSC on apoptosis was more pronounced than that of selenite, especially at th e 20 mu M level of exposure. The induction of apoptosis by selenium co mpounds may partially account for their chemopreventive activity.