Distinct effects of different concentrations of sodium selenite on apoptosis, cell cycle, and gene expression profile in acute promyeloytic leukemia-derived NB4 cells

Selenium at a low concentration has a chemopreventive role against cancer, while at a high concentration, it exerts a direct antitumor effect. However, the mechanisms remain elusive. In this article, we discovered that Na2SeO3 at 20 mu mol/l concentration could significantly inhibit the proliferation of NB4 cells, affect the cell cycle distribution of cell population, and induce cellular changes characteristic of apoptotic cells, while this same compound at 2 mu mol/l concentration had no such effects. The mechanisms underlying these overt differences caused by treatment of different concentrations of selenium were further investigated. cDNA microarray analysis showed that after treatment by 20 mu mol/l Na2SeO3, 34 genes were changed in expression, while treatment by 2 mu mol/l Na2SeO3 resulted in the changes of 29 genes. Nine genes were regulated in both groups, among which three showed opposite changes caused by 2 and 20 mu mol/l Na2SeO3. The majority of regulated genes did not coincide between the two experiment groups. In conclusion, 2 and 20 mu mol/l Na2SeO3 could have different effects on NB4 cells, and some genes might be involved in the underlying mechanisms. Our findings could provide basis for further uncovering the molecular mechanisms of the chemopreventive and antitumor effects of selenium and, in turn, for probing the rationality of treating leukemia with selenium.