The Bcl-2 family regulates apoptosis in response to a wide range of stimuli through control of mitochondrial cytochrome c release and caspase activation. Cytosolic Apaf-1 forms a complex with caspase-9 in the presence of cytochrome c and dATP, ultimately leading to caspase-9 activation and subsequent activation of caspase-3. A large number of proteins have been found to interact with Bcl-2 and other family members that have been shown to help regulate apoptosis. Aven was identified in a yeast two-hybrid screen as a bcl-xL interacting protein. It also interacts with other anti-apoptotic family members, including Bcl-2, but fails to interact with pro-apopotic proteins Bax and Bak. Aven inhibits apoptosis and enhances anti-apopotic activity of Bcl-xL. It interferes with association with Apaf-1 and activation of caspase-9. Aven overexpression is associated with poor prognosis in acute lymphoblastic leukemia.