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Aims To validate whether the anti-cancer effect of micro RNA-122 ( miR-122) on hepatocellular carcinoma ( HCC) is mediated through regulating Wnt/β-catenin signalling pathways. Methods The expression levels of miR-122 in HCC tissues and varied hepatoma cells were quantified by real-time PCR. MiR-122 agomir was transfected into HepG2, Hep3B cells to over-express miR-122. The effect of over-expression miR-122 on proliferation and apoptosis of HepG2 and Hep3B cells was evaluated using CCK-8 kit and flow cytometer respectively. The 3′- UTR segments of Wnt1 containing the miR-122 binding sites were amplified by PCR and the luciferase activity in the transfected cells was assayed. Wnt1 mRNA level was quantified using RT-PCR. Protein levels of Wnt1, β-catenin and TCF-4 were detected using Western blotting. Results In comparison with the expression level of miR-122 in para-cancerous tissues or Chang liver cell, the expression level in HCC tissues or varied hepatoma cells was significantly decreased ( P < 0.05). Over-expression of miR-122 significantly inhibited the proliferation ( P < 0.05), and promoted the apoptosis of HepG2 and Hep3B cells. Over-expressed miR-122 down-regulated the protein levels of Wnt1, β-catenin and TCF-4 ( P < 0.05). MiR-122 suppressed the luciferase activity of the pmiR-Wnt1-wt by approximately 50% compared with the negative control, while mutation or removal of the miR-122 binding site using si RNA or mir-122 inhibitor blocked the suppressive effect ( P < 0.05). Conclusions MiR-122 expression is down-regulated in human HCC. Over-expression of miR-122 inhibits HCC cell growth and promotes the cell apoptosis by affecting Wnt/β-catenin- TCF signalling pathway. [ABSTRACT FROM AUTHOR]