Calpain inhibitor attenuates GRP induction (A) and promotes AST-induced apoptosis (B). HCT116 colon cancer cells were either incubated with culture medium only (control) or pre-treated with the calpain inhibitor ALLN for 30 min. AST (80 μg/ml) was then administrated to cells and incubated for 24 h in all groups except the ALLN alone group. Specific antibodies against GRP78, GRP94, cleaved caspase-3 and PARP were used in Western immunoblotting to detect the expression of different proteins. Data shown are representative immunoblots with similar findings, normalized by β-actin. Blots were scanned and optical densities were determined using the Quantity One software. Each histogram represents mean ± SEM of four independent experiments. *p <0.05 compared with the control without drug treatment; #
p <0.05 compared with cells treated with ALLN alone.