FIGURE 4.

Inhibition of Cathepsin L fails to block radiation-induced cell death. Cathepsin L expression was analyzed by western blot in MDA-MB-231 cells at 6, 24, 48, 72 h after 8 Gy radiation (A). After the knockdown of Cathepsin L by siRNAs, Cathepsin L and Bid expressions were determined after 8 Gy radiation (B). Cells were untransfected or transfected with control siRNA (siNC) and siRNA against Cathepsin L (siCathepsin L) for 48 h before 8 Gy radiation, then cell death was determined (C). Cells were pretreated with CAA0225 (a Cathepsin L inhibitor, 10 μg/ml) for 1 h before 8 Gy treatment, cathepsin L and Cleaved-Caspase3 expression were tested (D). These results were representative of three independent experiments and expressed as means ± SD. P-values were calculated using repeated measure ANOVA with P < 0.05 being considered as statistical significance, *P < 0.05, #P > 0.05.