Caspase-3 activity assay
The caspase-3 activity was measured using caspase-3 colorimetric assay kit (BioVision Inc., Milpitas, CA, USA) as per the manufacturer's protocol. Briefly, apoptosis was induced as per the treatments under investigation and the cells were lysed using lysis buffer. The protein concentration in the lysates was measured using BCA Protein Assay Kit (Pierce Biotechnology, Rockford, IL, USA) and 50 μl of lysates containing 200 μg protein was used for caspase-3 activity. The lysates were mixed with 2 × reaction buffer containing 10 μM DTT and DEVD-pNA substrate and incubated at 37 °C for 2 h. Finally, the absorbance was measured using Benchmark Microplate Reader (Bio-Rad Laboratories) at 405 nm and the caspase activity was calculated with relative standard curve obtained using substrate alone.