Figure 2

Camptothecin induces caspase activation. Cells were treated with no drug, or CPT or caspase inhibitor plus CPT at doses as indicated for 48 h. Following drug treatment, cells were lysed and cell lysate immunoblotted for cleaved caspase-3 and cleaved Parp protein expression. A, Cleaved caspase-3 and cleaved PARP protein expression in wildtype DLM8 and K7M3 cells. B, Pan caspase inhibitor blocks caspase-3 activation. Cells were treated with CPT doses indicated in figure for 48 h. Treatment doses were based on cell sensitivity to CPT. C, Caspase inhibition reverses CPT-induced cell death in DLM8. Wildtype DLM8 and K7M3 cells were pretreated with a pan-caspase inhibitor for 2 h followed by CPT treatment for 48 h. Control group received no drug and an additional group received CPT only. Cell viability was determined by trypan blue exclusion assay. *, p < 0.05, compared with control group. Data represents the results of at least three independent experiments, ± SE. p < 0.05 was considered significant. Actin served as a protein loading control. Immunoblots are representative of immunoblots from at least two independent experiments.