Apoptin-induced apoptosis: potential for antitumor therapy

Cytotoxic anticancer agents often exert their effect by inducing apoptosis. Many tumors, however, are resistant to chemotherapy. This is due to lack of expression of certain genes essential in mediating the apoptotic signal, such as p53, or to over-expression of apoptosis inhibitors, such as bcl-2 or bcr-abl. Apoptin, a small protein derived from an avian virus, induces a p53-independent, bcr-abl-insensitive, and bcl-2-stimulated apoptosis in various human tumor cells. Interestingly, apoptin does not induce apoptosis in normal diploid cells. These features make apoptin a promising antitumor agent. Strategies for anti-cancer therapy based on viral vectors expressing apoptin are under development.