bcl-x gene is an important member of the bcl-2 multigene family.Three isoforms:Bcl-X_L,Bcl-X_S and Bcl-X_γ,are generated by alternative splicing.Bcl-X_L and Bcl-X_γ inhibit apoptosis. However,Bcl-X_S enhances apoptosis. Bcl-x plays a role in cell development,homeostatic balance, tumorigenesis and prognosis, which regulates apoptosis through interacting with Bcl-2, Bax, Bad and so on.