CPT induces caspase-independent cell death in tumor cells. A, DU145 cells grown in a black wall 96-well plate were treated with CPT (0–40 μmol/L) for 24 hours, followed by adding caspase-3/7 substrate solution (50 μL/well). After incubation at room temperature for 1 hour, the fluorescence intensity was recorded by excitation at 354 nm and emission at 442 nm using a Wallac 1420 Multilabel Counter. Results are presented as mean ± SE (n = 6). Note: CPT did not significantly alter the activities of caspase-3/7. DU145 cells were grown in 6-well plates and treated with CPT at indicated concentrations for 8 hours (B), or with CPT (10 μmol/L) for indicated time (C), followed by Western blot analysis with indicated antibodies.