The cover shows merged images of cytochrome c and SMAC in prostate cancer LNCaP cells. Both proteins reside in the mitochondria of healthy cells and are released into the cytoplasm in response to pro-apoptotic signals. Cytochrome c triggers the formation of multiprotein complex required for activation of caspase 9 and effector caspases. SMAC titrates away IAP proteins that bind to and inhibit caspases. Mixture of SMAC and cytochrome c effectively induces caspase activity when injected into the cytoplasm, while none of these two proteins can activate caspases when microinjected alone. Thus, coordinate release of cytochrome c and SMAC from mitochondria is required for effective activation of the caspase cascade. These data emphasize the central role of mitochondria in apoptosis of prostate cancer cells. For details, see the article by Carson et al. on p. 18 of this issue.