Calcium entry via ORAI1 regulates glioblastoma cell proliferation and apoptosis

Abstract

Introduction Calcium entry plays a critical role in the proliferation and survival of certain tumors. Ca 2+ release activated Ca 2+ (CRAC) channels constitute one of the most important pathways for calcium entry especially that of store-operated calcium entry (SOCE). ORAI1 and stromal interaction molecule1 (STIM1) are essential protein components of CRAC channels. In this study we tested the effect of inhibiting CRAC through ORAI1 and STIM1 on glioblastoma multiforme (GBM) tumor cell proliferation and survival. Methods Two glioblastoma cell lines, C6 (rat) and U251 (human), were used in the study. ORAI1 and STIM1 expressions were examined using Western blot and immunohistochemistry. CRAC channel activity and its components were inhibited with ion channel blockers and using siRNA knockdown. Changes in intracellular calcium concentration were recorded using Fura-2 fluorescent calcium imaging. Cell proliferation and apoptosis were examined using MTS and TUNEL assays, respectively. Results CRAC blockers, such as SKF-96365 (1-[2-(4-methoxyphenyl)-2-[3-(4-methoxyphenyl) propoxy]ethyl-1H-imidazole), 2-aminoethoxydiphenyl borate (2-APB) and Diethylstilbestrol (DES), inhibited cell proliferations and SOCE in GBM cells. Knockdown of ORAI1 and STIM1 proteins using siRNA significantly inhibited C6 cell proliferation and SOCE compared with those in control cells, and a more significant effect was observed in cells with ORAI1 siRNA knockdown than that of STIM1-treated cells. Both CRAC blockers and siRNA treatments increased apoptosis in C-6 cells compared with control. Conclusion Calcium entry via ORAI1 and CRAC channels are important for GBM proliferation and survival.