Initiation of apoptosis and autophagy by the Bcl-2 antagonist HA14-1

L1210 murine leukemia cells exposed to an LD(90) concentration of the Bcl-2/Bcl-x(L) antagonist HA14-1 rapidly undergo Apoptosis but also develop numerous intracellular vacuoles with double membranes, exhibit enhanced labeling by monodansylcadaverine, and convert the cytosolic protein LC3-I to LC3-II. These are hallmarks of Autophagy. Autophagic vacuoles develop rapidly, preceding the appearance of an apoptotic nuclear morphology and can be observed in both non-apoptotic and apoptotic cells. Inhibition of Autophagy by the PI 3-kinase inhibitor wortmannin promoted apoptosis; conversely inhibition of Caspase-3/7 with zDEVD-fmk promoted Autophagy. Neither process was dependent on calcium translocation. These results indicate that pharmacological suppression of Bcl-2 function can mimic the induction of Autophagy that can occur following the down-regulation of Bcl-2 expression by molecular approaches.