Inhibition of DcR2 protein expression by siRNA sensitizes LNCaP cells to TRAIL-induced apoptosis, in medium containing 10 nM R1881. LNCaP cells, untransfected (Ct: control) or transfected with scrambled siRNA (si0) or siDcR2 (0.5 μg) for 48 h were treated with TRAIL (100 ng/ml) for 24 h. (A) Histograms represent the number of fragmented nuclei per 1,000 cells from 5,000 randomly selected cells per culture. The values represent the mean ± SD determined from triplicate cultures of a representative experiment from 3 independent experiments. *P < 0.005 versus the other treatment conditions. (B) TRAIL-induced apoptosis, under previous conditions, was controlled by caspase-3 activity assay. Histogram values represent the mean ± SD determined from triplicate cultures of a representative experiment from 2 independent experiments performed at 10 nM R1881, *P < 0.05 with the Fisher post-test versus the other treatment conditions, except the control with TRAIL.