Apoptosis regulator Bcl-2 (Bcl-2) suppresses apoptosis in a variety of cell systems including factor-dependent lymphohematopoietic and neural cells. Bcl-2 regulates cell death by controlling mitochondrial membrane permeability. Bcl-2 functions in a feedback loop system with caspases, inhibiting caspase activity either by preventing the release of cytochrome c from the mitochondria and/or by binding to the apoptosis-activating factor (APAF-1). A chromosomal aberration involving Bcl-2 has been found in chronic lymphatic leukemia.