The mechanism of U937 cell apoptosis induced by a novel agonistic anti-human DR5 monoclonal antibody

The study aimed to investigate the cytotoxic effects of mouse anti-human DR5 monoclonal antibody(mDRA-6) on leukemic cell U937 and the underlying mechanism.Cytotoxicity exerted by mDRA-6 on U937 was measured by MTT colorimetry and the apoptosis of U937 after insulting by mDRA-6(10 mg/L) for 4 h was analyzed by FCM with Annexin V-FITC/PI staining.The expressions of caspase 8,10,3,9 in U937 cells were detected by Western blotting after treatment with mDRA-6.Furthermore,the inhibitors for caspase 8,10,3 were used to block the alternatively apoptotic pathways.FCM detection indicated that the apoptosis rate of the U937 cells was 69.03% in the presence of 10 mg/L mDRA-6 for 4 h.The active cleavage products of caspase 10,3,9 and Cytochome C in U937 cells were detected by Western blotting after treatment with mDRA-6 in time dependent manner,but caspase 8 was not.Caspase 10,3 inhibitors partly inhibited the apoptosis of U937 cells induced by mDRA-6,while caspase 8 inhibitor did not.The results mean that mDRA-6 is an agonistic anti-human DR5 monoclonal antibody which can induces U937 cells apoptosis through death-receptor and mitochondrial signal transduction pathways,respectively.