Apoptosis, or programmed cell death, is a regulated physiological process leading to cell death. Caspases, a family of cysteine acid proteases, are central regulators of apoptosis. Initiator caspases (including 8, 9, 10 and 12) are closely coupled to proapoptotic signals. Once activated, these caspases cleave and activate downstream effector caspases (including 3, 6 and 7), which in turn cleave cytoskeletal and nuclear proteins like PARP, alpha-Fodrin, DFF and Lamin A, and induce apoptosis. Cytochrome c released from mitochondria is coupled to the activation of caspase-9, a key initiator caspase. Proapoptotic stimuli include the FasL, TNF-alpha, DNA damage and ER stress. Fas and TNFR activate caspases 8 and 10; DNA damage leads to the activation of caspase-9; and ER stress leads to the calcium-mediated activation of caspase-12. The inhibitor of apoptosis protein (IAP) family includes XIAP and Survivin and functions by binding and inhibiting several caspases (4,5). Smac/Diablo, a mitochondrial protein, is released into the cytosol upon mitochondrial stress and competes with caspases for binding of IAPs. The interaction of Smac/Diablo with IAPs relieves the inhibitory effects of the IAPs on caspases (6).