HL-60 세포에서 Comptothecin의 apoptosis 유도작용

Induction of Apoptosis by Camptothecin in HL-60 Cells

Camptothecin (CPT) has been known to induce apoptosis in various cancer cell lines. To examine the intracellular apoptotic death signal initiated by CPT, we investigated the possible connection between caspase-3 activation and GSH depletion during CPT-induced apoptosis in HL-60 cells. Treatment of cells with 1mcM CPT induced PARP cleavage accompanied by DNA fragmentation. z-VAD-fmk, a caspase-3 inhibitor, blocked the CPT-induced DNA fragmentation. Pretreatment of cells with N-ace-ylcysteine, a precursor of GSH biosynthesis, failed to inhibit CPT-induced PARP celavage and DNA fragmentation. No significant changes in GSH levels were observed during 6hr after CPT treatment. Taken together, these results show that GSH depletion is not essential for caspase activation during CPT-induced apoptosis. We also investigated whether CPT-induced apoptosis is associated with changes of the levels of Bax and Bcl-2, two proteins involved in the control of apoptosis. Bcl-2 levels exhibited a late decrease compared with the kinetics of DNA fragmeentation, whereas Bax levels increased more rapidly after CPT treatment. These results suggest that Bax plays more important role than Bcl-2 in inducing DNA fragmentation and may function upstream of proteolytic activation of caspase-3 pathway in CPT-induced apoptosis.