BAD induces apoptosis in cells over-expressing Bcl-2 or Bcl-xL without loss of mitochondrial membrane potential

Inhibitors of Bcl-2 may be useful therapeutic agents for the treatment of a wide variety of malignancies including leukemia. A potential prototype of such a compound is the endogenous Bcl-2 and Bcl-xL binding protein BAD. Pre vious reports indicate that BAD can overcome the anti-apoptotic effect of B cl-xL but not Bcl-2. If BAD cannot induce apoptosis in cells over-expressin g Bcl-2, it would limit the application of molecules like BAD as novel anti -tumor agents. We report that transient transfection of BAD induced cell de ath in cells with and without over-expression of Bcl-2 or Bcl-xL. Forty-eig ht hours after transfection, BAD increased cell death in COS, COS Bcl-2, an d COS Bcl-xL cells as demonstrated by decreased GFP expression, and an incr ease in the number of number of floating cells. In addition, BAD induced ce ll death in leukemic cell lines over-expressing Bcl-2 and Bcl-xL as determi ned by changes in luciferase activity BAD-induced apoptosis was not accompa nied by loss of mitochondrial membrane potential. Therefore, we conclude th at transient transfection of BAD directly induces apoptosis in cells over-e xpressing Bcl-2 or Bcl-xL and validates the pursuit of molecules like BAD a s novel therapeutic agents.