Objective       To investigate the mechanism by which miR-134 regulates the expression of forkhead box M1 (FOXM1) and determine the effect of miR-134 on the proliferation of hepatocellular carcinoma cells (HCC).  Methods      The proliferation of HCC cells was analyzed by CCK=8 assay. The

levels of FOXM1 and miR-134 were separately examined by Western blotting and real-time PCR in human normal hepatic cell line L02 and 5 kinds of HCC cell lines. After transfection with miR-134 mimic or inhibitor

the expression of FOXM1 and its target gene CyclinD1 in HCC cells were measured by Western blotting and real-time PCR. The potential binding site of miR-134 on the 3′ UTR of human FOXM1 mRNA was predicted by using online bioinformative databases. Then the luciferase reporter assays were performed to identify the specific binding of miR-134 with 3′ UTR of FOXM1 mRNA. After cotransfected with miR-134 mimic or FOXM1-expressing plasmids (without 3′ UTR)

the HCC cell proliferation was detected by CCK-8 assay. Results      miR-134 dramatically suppressed the proliferation of HCC cells (P0.05). Compared to normal liver cell line

L02 cells

miR-134 was lowly expressed while the FOXM1 protein was highly expressed in the HCC cells(P0.05)

and a negative correlation was found between miR-134 level and FOXM1 protein level  (R

2

=0.705

P0.05). miR-134 significantly downregulated FOXM1 protein

and its downstream target gene

CyclinD1

in HCC cells (P0.05). The luciferase reporter assay showed that miR-134 specifically bound to the 3′UTR of FOXM1 mRNA (P0.01). The cell proliferation assay revealed that the ectopic expression of FOXM1 without 3′UTR in HCC cells significantly attenuated the miR-134-mediated growth inhibition of HCC cells (P0.05). Conclusion      miR134 down-regulates FOXM1 protein by directly targeting the 3′ UTR of FOXM1 mRNA

and subsequently suppresses the proliferation of HCC cells.