Abstract: Objective To identify the effects of miR-122(a hepatic microRNA)on the cellular behavior of hepatocellular carcinoma cells(HCC).Methods The apoptosis and cell cycle of HepG2 and Huh-7 cells transfected with miR-122 or anti-miR-122 were analyzed by Annexin ⅴ-based flow cytometry,terminal deoxynucleotidy1 transferase dUTP nick end labeling(TUNEL)detection as well as PI-based flow cytometry at 24 and 48h posttransfection.Cells transfected with Mock were served as negative controls.Results There was no significant difference between the apoptosis,cell cycles of HepG2 cells transfected with miR-122 and Mock HepG2 cells at 24,48h posttransfection(P＞0.05).However,compared to Mock Huh-7 cells,the apoptosis of Huh-7 cells transfected with anti-miR-122 was signaficantly decreased at 48h posttransfection(P＜0.05);the rate of Huh-7 cells treated with anti-miR-122 in G₀~G₁ phase was significantly up-regulated,compared with that of mock cells.The rates in S phase and G₂-M phase were down-regulated(P＜0.05).Conclusion The down-regulation of miR-122 expression might prevent the apoptosis of certain type of HCC,such as Huh-7 cells.miR-122 may be as an endogenous regulating factor of apoptosis to play the antineoplastic effect in the liver tissues.