Rise of [Ca²âº]i and apoptosis induced by M-3M3FBS in SCM1 human gastric cancer cells.

M-3M3FBS (2,4,6-trimethyl-N-(meta-3-trifluoromethyl-phenyl)-benzenesulfonamide is a presumed phospholipase C activator which induced Ca²âº movement and apoptosis in different cell models. How- ever, the effect of m-3M3FBS on cytosolic free Ca²âº concentrations ([Ca²âº]i) and apoptosis in SCM1 human gastric cancer cells is unclear. This study explored whether m-3M3FBS elevated basal [Ca²âº]i levels in suspended cells by using fura-2 as a Ca²âº-sensitive fluorescent dye. M-3M3FBS at concentrations between 5-50 µM increased [Ca²âº]i in a concentration-dependent manner. The Ca²âº signal was reduced by half by removing extracellular Ca²âº. M-3M3FBS-induced Ca²âº influx was inhibited by nifedipine, econazole, SK&F96365, aristolochic acid, and GF109203X. In Ca²âº-free medium, 50 µM m-3M3FBS pretreatment inhibited the [Ca²âº]i rise induced by the endoplasmic reticulum Ca²âº pump inhibitor thapsigargin. Conversely, pretreatment with thapsigargin partly reduced m-3M3FBS-induced [Ca²âº]i rise. Suppression of inositol 1,4,5-trisphosphate production with U73122 did not change m-3M3FBS- induced [Ca²âº]i rise. At concentrations between 25 and 50 µM m-3M3FBS killed cells in a concentration- dependent manner. The cytotoxic effect of m-3M3FBS was not reversed by prechelating cytosolic Ca²âº with acetoxy-methyl ester of bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA/AM). Annexin V/propidium iodide staining data suggest that m-3M3FBS induced apoptosis at 25 and 50 µM. M-3M3FBS also increased levels of superoxide. Together, in human gastric cancer cells, m-3M3FBS induced a [Ca²âº]i rise by inducing phospholipase C-independent Ca²âº release from the endoplasmic reticulum and Ca²âº entry via protein kinase C-sensitive store-operated Ca²âº channels. M-3M3FBS induced cell death that might involve apoptosis via reactive oxygen species production.