Activation of caspase-8 in JPX-9 cells during PDTC-induced apoptosis. JPX-9 cells were preincubated with or without CdCl₂ for 6 hours, washed with PBS, and further incubated with or without PDTC (50 μmol/L) for 24 hours. After incubation, the expression of procaspase-8 was examined as described in the text. Note that the decrease of pro-caspase-8 expression, which indicates caspase-8 activation, was almost recovered even in the presence of PDTC by preincubation of the cells with CdCl₂. Results are representative examples of 5 similar experiments.