XIAP is a member of the family of inhibitor of apoptosis proteins (IAP). Overexpression of IAP family members, particularly survivin and livin, in cancer cell lines and primary tumors suggests an important role for these proteins in cancer progression. XIAP inhibits activated caspase-3, leading to the resistance of FAS-mediated apoptosis. XIAP is highly characterized with respect to its structure and biochemical mechanisms, and has received interest as a therapeutic target. In addition, binding of IAP family members to the mitochondrial protein Smac blocks their interaction with caspase-9, thereby allowing the processing and activation of the caspase.
