Econazole‐induced Ca2+ fluxes and apoptosis in human oral cancer cells

The effect of econazole on cytosolic free Ca²⁺ concentrations ([Ca²⁺]_i) and viability was explored in human oral cancer cells (OC2), using the fluorescent dyes fura‐2 and WST‐1, respectively. Econazole at concentrations of >1 µM increased [Ca²⁺]_i in a concentration‐dependent manner. The Ca²⁺ signal was reduced partly by removing extracellular Ca²⁺. The econazole‐induced Ca²⁺ influx was sensitive to blockade of aristolochic acid (phospholipase A₂ inhibitor) and GF109203X (PKC inhibitor). In Ca²⁺‐free medium, after treatment with 1 µM thapsigargin (an endoplasmic reticulum Ca²⁺ pump inhibitor), 30 µM econazole failed to induce a [Ca²⁺]_i rise. Inhibition of phospholipase C with 2 µM U73122 substantially suppressed econazole‐induced [Ca²⁺]_i rise. At concentrations of 5–70 µM econazole killed cells in a concentration‐dependent manner. The cytotoxic effect of 50 µM econazole was enhanced by prechelating cytosolic Ca²⁺ with 1,2‐bis(2‐aminophenoxy)ethane‐N,N,N′,N′‐tetraacetic acid (BAPTA). The ERK MAPK inhibitor, PD98059 (10 µM), also enhanced 20 µM econazole‐induced cell death. Propidium iodide staining data suggest that econazole induced apoptosis between concentrations of 10–70 µM. Collectively, in OC2 cells, econazole induced [Ca²⁺]_i rises by causing Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ influx from phospholipase A₂/PKC‐regulated Ca²⁺ channels. Furthermore, econazole caused cell death appeared to be regulated by ERK MAPK. Drug Dev Res 71: 240–248, 2010. © 2010 Wiley‐Liss, Inc.