[The mechanism of apoptosis induced by anticancer agents in human leukemia cells].

Many anticancer agents induce apoptosis in human leukemia cells. Among the various leukemia cells, especially HL-60 cells and U937 cells are very sensitive to apoptosis upon anticancer agents treatment. A serine protease inhibitor TPCK and an ICE-like protease inhibitor VAD-FMK prevented etoposide, camptothecin and ara-C-induced internucleosomal DNA cleavage in human myeloid leukemia HL-60 and U937 cells. Using a cell-free system, we have examined the inhibitory mechanism of these inhibitors on anticancer agent-induced internucleosomal DNA cleavage. Our data indicate that serine and ICE-like proteases may be involved in anticancer agent-induced apoptosis at the different stages, and especially a serine protease may be closely associated with the final step for induction of DNA fragmentation during apoptosis in human myeloid leukemia HL-60 and U937 cells.