Caspase-dependent and caspase-independent mechanisms of cell death.

Caspase-dependent apoptosis induced by death-receptor ligation can act independently of the mitochondria and is inhibited by P-glycoprotein (P-gp) at the level of caspase-8 and caspase-3 activation. In contrast, some cytotoxic drugs induce the disruption of mitochondrial membrane potential (ΔΨ_m), release of cytochrome c, and subsequent activation of caspase-9. In addition, disruption of ΔΨ_m can also lead to caspase-independent cell death that is not inhibited by P-gp.