Differential involvement of caspases in apoptosis of myeloid leukemic cells induced by chemotherapy versus growth factor withdrawal.

To assess the potential involvement of the caspase family in the IL-3-dependent murine myeloid leukemic cell line 32D, we studied the effect of bcl-2, crmA and three synthetic caspase inhibitors on apoptosis induced by chemotherapy or IL-3 withdrawal. Apoptosis induced by IL-3 deprivation or by ActD appears to be mediated by a crmA-insensitive pathway. Cell death by IL-3 withdrawal is inhibited by the caspase-inhibitor ZVAD-fmk, but not DEVD-fmk or YVAD-cmk. In contrast, DEVD-fmk as well as ZVAD-fmk protect 32D cells from ActD-induced apoptosis. These results indicate that different caspases are involved in apoptosis induced by growth factor withdrawal and by chemotherapy.