Involvement of microRNA-718, a new regulator of EGR3, in regulation of malignant phenotype of HCC cells.

OBJECTIVE: Hepatocellular carcinoma (HCC) is still one of the most common death-related malignancies worldwide. Because the way onset and progression are hidden most, HCC diagnoses are made at an advanced stage, when they are unsuitable for surgical resection. MicroRNAs are a class of small non-coding RNAs, participating in many aspects of cancers. In this study, we tried to establish the role of microRNA-718 (miR-718) in the malignant phenotype of HCC cells and its possible role in HCC diagnosis.

METHODS: Here we first used a methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, Transwell migration and invasion assays, and colony formation assay to evaluate the impact of miR-718 on the malignant phenotypes of HCC cells. Then, we used bioinformatic methods to predict the target gene of miR-718 and used green fluorescence protein (GFP) reporter assay, Western blot, and quantitative real-time polymerase chain reaction (qRT-PCR) to validate the regulation relationship. Finally, we determined the role of the target gene in the HCC phenotype.

RESULTS: We found that the expression of miR-718 was significantly reduced in various HCC cell lines and HCC tissues. Re-expression of miR-718 significantly reduced the cellular viability and colony formation ability as well as inhibited the migration and invasion abilities of HCC cell lines. Early growth response protein 3 (EGR3) is a direct target of miR-718 and is negatively regulated by miR-718. EGR3 could increase the viability and proliferation of HCC cells, and promot the migration and invasion of HCC cells.

CONCLUSIONS: miR-718 acts as a tumor suppressive microRNA in HCC via regulating the expression of EGR3, which may provide a new diagnostic marker and treatment target for HCC.