Inhibitors of Apoptosis (IAPs) A promising group of E3s as drug targets in cancer is the IAP (anti-apoptotic proteins) family [188] that is augmenting the anti-apoptotic NF-kB pathway and inhibiting the pro-apoptotic apoptotic caspases and Smac proteins [59, 189]. The gene discussed is NFKB1; the disease is cancer.