Killing of tumor cells by anticancer therapies commonly used in the treatment of cancer, e.g. chemotherapy, gamma-irradiation, immunotherapy or suicide gene therapy, is predominantly mediated by triggering apoptosis, the cell's intrinsic death program. Accordingly, defects in apoptosis pathways can result in cancer resistance to current treatment approaches. Understanding the molecular mechanisms that regulate cell death programs including apoptosis, and how resistant forms of cancer evade apoptotic events, may provide novel opportunities for cancer drug development.