Apoptosis is tightly regulated by a balance between pro-apoptotic and anti-apoptotic signals. The Bcl-2 family of proteins includes both pro-apoptotic members (e.g., Bax, Bak) and anti-apoptotic members (e.g., Bcl-2, Bcl-xL). The relative levels of these proteins determine the susceptibility of a cell to undergo apoptosis. Additionally, various extracellular signals such as growth factors, cytokines, and hormones can influence apoptosis by modulating these regulatory proteins.
