ABSTRACT
Apoptosis is a key mechanism for the termination of an immune response by elimination of unnecessary effector cells to avoid autoimmunity and tissue damage. Most apoptosis signaling pathways ultimately result in activation of caspases, a family of cysteine proteases that act as common death effector molecules in various forms of cell death. Caspases involved in apoptosis signaling are categorized into initiator and effector caspases, respectively. Despite the fact that leukemia represents a highly aggressive malignant disease in vivo, at least cells from patients with acute leukemia often show increased apoptosis when cultured in vitro. For most apoptosis regulators, numerous studies have demonstrated their importance for normal growth control in hematopoietic cells. On the basis of the concept that resistance to apoptosis is a characteristic feature of human cancers that contributes to tumor formation and progression, strategies designed to restore defective apoptosis programs in cancer cells may overcome intrinsic or acquired resistance of tumor cells.
