Overexpression of miR-218 inhibits hepatocellular carcinoma cell growth through RET.

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world with poor prognosis. Here, we investigated the role of microRNA 218 (miR-218) in regulating human HCC development. Quantitative PCR (qPCR) was used to compare the expression levels of miR-218 between eight HCC and a normal liver cell lines, as well as nine primary HCC tissues and adjacent non-carcinoma tissues. HCC cell lines MHCC97L and Huh7 were transfected with lentiviral vector of miR-218 mimics. The effect of miR-218 overexpression on cancer cell growth, both in vitro and in vivo, as well as cancer cell invasion was examined. A bioinformatic method was used to predict the binding of miR-218 to RET proto-oncogene (RET). Small interfering RNA (SiRNA)-mediated genetic knock-down of RET was performed in MHCC97L and Huh7 cells, and its modulatory effect on miR-218-mediated HCC development was examined. miR-218 was found to be downregulated in HCC cell lines and primary HCC tissues. Overexpression of miR-218 in MHCC97L or Huh7 cells resulted in significant decrease in cell proliferation and invasion capability. Overexpression of miR-218 also reduced the tumor growth of xenografted Huh7 cells in vivo. The expression of endogenous RET was found to be upregulated by miR-218, and siRNA-induced RET downregulation resulted in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) upregulation and reversal of the inhibitory effect of miR-218 upregulation on HCC proliferation. Our results indicate that miR-218 modulates HCC development, and this effect may be through RET and PTEN.