Calcimycin mediates apoptosis in Breast and Cervical cancer cells by inducing intracellular calcium levels in a P2RX4-dependent manner

Calcimycin (A23187) is a polyether antibiotic and divalent cation ionophore, extracted from Streptomyces chartrecensis. With wide variety of antimicrobial activities, it also exhibits cytotoxicity of tumor cells. Calcimycin exhibit therapeutic potential against tumor cell growth; however, the molecular mechanism remains to be fully elucidated. Present study explores the mechanism of calcimycin-induced apoptosis cancer cell lines. Calcimycin induces apoptosis accompanied by increased intracellular calcium-level and increased expression of purinergic receptor-P2RX4, a ligand-gated ion channel. The percentage of apoptotic cancer cells in a dose-dependent manner quickly rose as recorded with MTT assays, Phase contrast imaging, wound healing assay, fluorescence imaging by DAPI and AO/EB staining and FACS. Mitochondrial potential was analyzed by TMRM assay as Ca2+ signaling is well known to be influenced and synchronized by mitochondria also. Calcimycin treatment tends to increase the intracellular calcium level, mRNA expression of ATP receptor P2RX4, and phosphorylation of p38. Blocking of either intracellular calcium by BAPTA-AM, P2RX4 expression by antagonist 5-BDBD, and phospho-p38 by SB203580, abrogated the apoptotic activity of calcimycin. Taken together, these results show that calcimycin induces apoptosis in P2RX4 dependent ATP mediated intracellular Ca2+ and p38 MAPK mediated pathway in both the cancer cell lines.