Homoharringtonine (HHT) is a cephalotaxine ester derived from an evergreen tree found wildely throughout southern China, which has antileukemic activities against a variety of acute myeloid leukemic cells. HHT was recently shown by us to have differentiative and apoptotic effects on human leukemic cell lines. Recently, apoptosis has been associated with oxidative stress in a number of cell systems. Here we assessed the inhibitory capacity of antioxidant on HHT-induced apoptosis in the human leukemic cell line, K562. The apoptosis was analyzed by agarose gel electrophoresis of DNA, flow cytometry and terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin nick labeling. K562 cells were treated with HHT at doses of 0ug/ml, 25ug/ml for 24 hours. Vitamin C (0.2 ug/ml) were added to medium 16 hour before addition of HHT. Results showed vitamin C inhibited oxidative stress and K562 cells apoptosis in HHT-treated groups (P < 0.05). Our data indicated that HHT treatment primarily induces K562 cells apoptosis at concentration up to 100 ug/ml. The underlying mechanism appears to involve mitochondrial damage via an increase in oxidative stress.

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