In recent years, researchers have become particularly interested in targeting this network because of three key advances: (1) the seemingly paradoxical observation that cancers typically maintain apoptotic competence3; (2) the observation that some cancer cells are particularly “primed” to undergo apoptosis relative to most normal cells in the adult2, and (3) the development of selective, potent, and in vivo bioavailable small molecule inhibitors of the BCL-2 family proteins (e.g., BCL-XL, BCL-2, and MCL-1), known as “BH3 mimetic” drugs4,5. Here, BCL2 is linked to cancer.