Fig. 1.

Effect of quercetin on TRAIL-induced apoptotic pathway in DU-145 prostate cancer cells. (A) Cells were treated for 24 h with a concentration of TRAIL (50 ng/ml) in various concentrations of quercetin (10 to 100 µM). Quercetin-treated cells showed reduced viability, as shown by trypan blue exclusion. Statistics, *Statistical significant at p<0.05. (B) Cells were treated for 4 h with TRAIL (50 ng/ml) in the presence or absence of 100 µmol/l quercetin. Quercetin enhanced apoptosis, as shown by FACS analysis. (C) Cells were treated for 4 h with TRAIL in the presence or absence of 100 µmol/l quercetin. Quercetin enhanced apoptosis, as shown by the TUNEL assay. (D) DU-145 cells were pretreated with the general caspase inhibitor Z-VAD-FMK (20 µmol/l) for 30 min and further treated with quercetin (100 µmol/l) in the presence or absence of TRAIL (50 ng/ml) for 24 h and then harvested. Quercetin enhanced the cleavage of PARP, caspase-3, and caspase-9, and Z-VAD-FMK blocked this effect, as shown by Western blot analysis. Error bars represent standard error of the mean (SEM) for three separate experiments. Con, control.