MicroRNA-875-5p inhibits tumor growth and metastasis of hepatocellular carcinoma by targeting eukaryotic translation initiation factor 3 subunit a

Accumulating evidence has demonstrated that aberrant microRNA (miRNA) expression is involved in hepatocellular carcinoma (HCC) progression. Previous findings suggested that miRNA (miR)-875-5p participates in the development of various types of cancer. However, the expression and function of miR-875-5p in HCC remains largely unclear. The analysis of clinical samples in the present study demonstrated that miR-875-5p expression was downregulated in HCC tissues compared to adjacent non-tumor tissues, which was associated with a large tumor size, venous infiltration, advanced tumor-node-metastasis stage and unfavorable overall survival. In vitro experiments revealed that ectopic expression of miR-875-5p suppressed, whereas inhibition of miR-875-5p promoted HCC cell proliferation, migration, invasion and epithelial-to-mesenchymal transition (EMT) progression. Overexpression of miR-875-5p restrained HCC tumor growth and metastasis in vivo. Mechanistically, eukaryotic translation initiation factor 3 subunit a (eIF3a) was identified as the downstream target of miR-875-5p in HCC. Further experiments demonstrated that the expression of eIF3a was upregulated and negatively correlated with that of miR-875-5p in HCC tissues. In addition, miR-875-5p negatively regulated the luciferase activity of wild-type, but not mutant 3'-untranslated region (3'UTR) of eIF3a mRNA. miR-875-5p suppressed eIF3a expression at the mRNA and protein level in HCC cells. Additionally, eIF3a exerted an oncogenic role, and knockdown of eIF3a inhibited the proliferation, motility and EMT of HCC cells. In addition, eIF3a overexpression abolished the inhibitory effects of miR-875-5p on the proliferation, motility and EMT in HCC cells. In conclusion, miR-875-5p, which was downregulated in HCC, may inhibit tumor growth and metastasis by eIF3a downregulation via targeting its 3'UTR and may be a promising prognostic and therapeutic strategy in HCC.