BCL2 and cancer: Analyzing the role of anti-apoptotic Bcl-2 family members in hypoxia-mediated radioresistance, we demonstrate here that exposure of cancer cells to acute and repeated cycles of hypoxia alters the balance of Bcl-2 rheostat in favor of anti-apoptotic family members, thereby elevating the apoptotic threshold, impeding cell death induction and restricting favorable therapeutic outcome.