Selenium causes growth inhibition and apoptosis in human brain tumor cell lines

We examined the effect of the trace element selenium on human glioma cell lines: T98G, U373MG, and U87MG, in addition to dermal fibroblast cells. Cultures were incubated with sodium selenite, and the following parameters were studied: cell growth, mitochondrial function, and ultrastructure. Cell growth was assayed by counting the number of viable cells after treatment with selenium. Mitochondrial function was analyzed using the MTT (tetrazolium salt reduction) assay. Apoptosis was determined by evaluating nuclear chromatin condensation by electron microscopy. The results indicated that selenium had a significant inhibitory effect on the growth of the tumor cells but had little effect upon dermal fibroblasts which had been passaged numerous times. Selenium also induced mitochondrial damage as shown by MTT assay in two brain tumor cell lines and in minimally passaged fibroblasts, but it had little effect upon the high-passage fibroblasts. Ultrastructurally, mitochondria had electron-dense inclusions resulting from selenium treatment. High rates of apoptosis were induced by selenium in the tumor cell lines and in the minimally passaged fibroblasts, whereas the fibroblasts with a high number of passages had some resistance to selenium treatment. This study correlates the adverse effects of selenium on mitochondrial function, inhibition of cell growth, and apoptosis and shows that selenium similarly affects three different brain tumor cell lines and minimally passaged fibroblasts. Further, the results with fibroblasts show that some types of cells after repeated passages can develop resistance to selenium damage.