Variation of T-type calcium channel protein expression affects cell division of cultured tumor cells

In this study we investigated the T-type calcium channel and its involvement in the cell division of U87MG cultured glioma cells and NIE-115 neuroblastoma cells. Using Western blot analysis, we found that expression of both alphalG and alphalH subunits of the T-type calcium channel decreased during conditions associated with a decrease in proliferation as evidenced by increased expression of cyclin Dl, a marker for non-proliferating cells. Both serum starvation and application of mibefradil, a selective T-type calcium channel antagonist, resulted in a 50% decrease in the expression of alphalG and alphalH and a 700-900% increase in levels of cyclin Dl in U87MG and NIE-115 cells, respectively. Furthermore, overexpression of the alphalH subunit resulted in a two-fold increase in cell proliferation compared to control cultures or cultures receiving an empty vector. In contrast, blocking expression of the a I G subunit using antisense oligonucleotides lead to a 70% decrease in proliferation of U87MG and NIE-115 cells compared to control Cultures or cultures receiving a scrambled oligonucleotide. Our findings suggest that proliferation of U87MG glioma cells and NIE-115 is regulated by T-type calcium channel expression. (C) 2004 Elsevier Ltd. All rights reserved.