Increased activation of pro-caspases in TRAIL-treated metastatic cancer cells. (A) The cell lysates obtained from PC3 and PC3-MM2 cells treated with 2 or 10 ng/ml TRAIL for 6 h (left) or KM12 and KM12L4A cells treated with 5 or 25 ng/ml TRAIL for 8 h (right) were subjected to Western blot analysis to monitor the levels of caspase-8, -9 and -3, Bax and Bcl-2. The levels of PARP and its cleavage fragment (CF) in TRAIL-treated cells were also determined. (B) PC3-MM2 cells were transfected with siRNA against c-myc or scrambled siRNA as a control. After 48 h, the transfectants were treated with TRAIL (1 or 5 ng/ml) for 6 h and were subjected to Western blot analysis to monitor the change in activities of caspases and PARP. Actin was used as a loading control.