Caspase-3 activity assay

The detailed protocol for the caspase-3 activity assay was described early [37]. In brief, following the applied treatment, floating cells and growing cells were combined. The cells were then lysed in 2× caspase lysis buffer [37]. Fifty μg of total proteins per sample were mixed with 2× caspase assay buffer [37] and the caspase-3 substrate: Ac-DEVD-AFC. After incubation, the fluorometric detection of cleaved AFC product was performed on a CytoFluor Multi-Well Plate Reader Series 4000 (PerSeptive Biosystems) using a 400-nm excitation filter and a 530-nm emission filter. The caspase-3 activity of treatment group was always normalized to that of untreated control group.