Up-regulated miR-500a enhances hepatocarcinoma metastasis by repressing PTEN expression

It has been shown that miR-500a may play an important role in the metastasis of hepatocarcinoma. The present study is to explore the influence of miR-500a on hepatocarcinoma proliferation and metastasis, and the related molecular mechanism. The levels of miR-500a in the serum and tissues of patients with metastatic or non-metastatic hepatocarcinoma or normal people were determined by quantitative reverse transcription-PCR (qRT-PCR). The proliferation, invasion, and cloning of hepatocarcinoma cell lines SMMC-7721 after transfection with mimic miR-500a or inhibitor miR-500a were determined. Luciferase reported assay was used to explore the relationship between miR-500a and phosphatase and tensin homologue (PTEN). Then, the protein expression of PTEN, p-Akt (S473), p-Akt (T308), Akt, p-mTOR, mTOR, p-4E-BP1, 4E-BP1, p-S6K, and S6K in SMMC-7721 cells were also determined by Western blotting. The expression of miR-500a in patients with metastatic hepatocarcinoma was significantly higher than the non-metastatic hepatocarcinoma. Overexpression of miR-500a promoted the proliferation, invasion, and cloning of SMMC-7721 cells. Luciferase reported assay showed miR-500a could directly target at 3′-UTR of PTEN. Overexpression of miR-500a significantly reduced the expression of PTEN, and enhanced phosphorylation of Akt, mTOR, S6K, and 4E-BP1. In conclusion, the expression of miR-500a was related to the proliferation and metastasis of hepatocarcinoma, which may be partly because of the activation of AKT/mTOR pathway through targetting PTEN.