CGN PE extract treatment causes caspase dependent apoptotic cell death in human breast cancer cells. (A) ZR751 cells were treated with (5 – 40 μg/ml) or without PE extract for up to 24 h. Protein expression of p53, BAX, Bcl2, caspase-3, PARP and cleaved-PARP was determined by western blot. β - actin was used as loading control (B) ZR751 cells were treated with (5 – 40 μg/ml) or without PE extract for up to 24 h prior to caspase-3, caspase-8 and caspase-9 activity assay. Each bar represents the mean ± SD (n = 3). Bars marked without a common letter within each caspase activity are significantly different (P < 0.05) analysed by one-way ANOVA supplemented with Tukey’s HSD test.