OBJECTIVE： To investigate the apoptotic effects and underlying molecular mechanisms of Celastrus orbiculatus （C. orbiculatus） extract in human hepa- tocellular carcinoma cells. METHODS： Human hepatocellular carcinoma cells （HCCLM6） were treated with C. orbiculatus extract （COE） at different nontoxic concentrations （10, 20, 40, 80, and 160 IJg/mL）. The effect of COE on HC-CLM6 viability was examined using 3-（4,5-dimethyl- thiazol-2-yl）-2,5-diphenyl tetrazolium bromide （MTT） assays. Cellular apoptosis following COE treatment was assessed by flow cytometry and western blot analysis. RESULTS： COE significantly inhibited cell viability and induced apoptosis of HCCLM6 cells in a dose-dependent manner. Apoptosis was accompa- nied by increased Bax expression and decreased Bcl-2 expression. In addition, COE treatment led to the release of cytochrome c, activation of cas- pase-3, and cleavage of poly （ADP-ribose） poly- merase （PARP）. Furthermore, activation of extracel- lular signal-regulated kinase （ERK）, p38 kinase, and c-Jun N-terminal kinase （JNK） phosphorylation, and down-regulation of Akt phosphorylation was ob- served. CONCLUSION： COE induces mitochondrial-mediat- ed, caspase-dependent apoptosis in HCCLM6 cells, which might be attributed to the activation of mito- gen-activated protein kinase （MAPK） and inhibition of Akt signaling pathways. These data suggest that COE may be a potential treatment for human hepa- tocellular carcinoma.
