Activation of caspase-3 is required for cisplatinum - Dependent apoptosis

Activation of the caspase family of proteases is a critical step in the cellular pathway(s) leading to apoptotic cell death. Here we report that multiple myeloma cells treated with cisplatinum undergo apoptosis in a dose dependent manner, resulting in a 10-fold increase in apoptosis at 15 μg/ml cisplatinum. Cell cycle analysis demonstrated that cisplatinum-dependent apoptosis was cell cycle independent. Measurement of caspase protease activity showed that caspase-3 was increased at 9 h after cisplatinum treatment of cells and was maximally activated at 15 h demonstrating a 3.5 fold increase over control. Caspase-1 activity was unaffected by cisplatinum. This cisplatinum-dependent increase in caspase-3 activity was coupled to a loss of poly(ADP-ribose) polymerase (PARP) integrity. Blockage of cellular caspase-3 activity with benzyloxycarbonyl-Asp-2,6-dichloro-benzoyloxymethylketone (Z-Asp) completely inhibited cisplatinum-dependent apoptosis and PARP degradation. Finally, cisplatinum treatment of cells increased c-Jun N-terminal kinase-1 (JNK1) activity at 9 h and produced a maximum increase of 3 fold at 15 h. Inhibition studies with Z-Asp found that JNK1 activation was independent of caspase-3 activation. These results indicate that apoptosis induced by cisplatinum require the activation of caspase-3 and that JNK1 activation is independent of caspase-3 activation.