Comparison of the effects of an organic and an inorganic form of selenium on a mammary carcinoma cell line

4To whom correspondence should be addressed The development of new compounds with greater cancer inhibitory activity and that are well tolerated continues to be a priority in chemoprevention research involving selenium. One compound, l,-4-phenylene-bis(methylene)selenocyanate (p-XSC), is representative of a series of organoselenium compounds with these characteristics. In this study, the effects 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 selenium within cells than did treatment with equivalent amounts of selenite and cells were able to better tolerate higher cellular levels of selenium derived from p-XSC. Both compounds resulted in a dose-dependent reduction in cell number after 24 h of exposure. Selenite and p-XSC also caused a dose-dependent increase in cell death by apoptosis. This effect was observed within 5 h of treatment. The effect of p-XSC on apoptosis was more pronounced than that of selenite, especially at the 20 /JV1 level of exposure. The induction of apoptosis by selenium compounds may partially account for their chemopreventive activity