MicroRNA-181a-5p suppresses cell proliferation by targeting Egr1 and inhibiting Egr1/TGF-β/Smad pathway in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the leading cause of cancer mortality worldwide. Early growth response factor 1 (Egr1) plays a crucial role in cancer progression. However, its precise role in HCC has not been clear. Here, we identified the aggravating role of Egr1 in cell proliferation of HCC firstly. The expression of Egr1 was significantly increased in HCC tissues. Functionally, overexpression of Egr1 enhanced, whereas silenced Egr1 expression attenuated HCC cells proliferation in vitro. Mechanistically, up-regulated Egr1 induced cell proliferation through activating Transforming growth factor (TGF)-β1/Smad signaling pathway concomitantly with upregulation of p-Smad2 and p-Smad3. Secondly, miR-181a-5p was down-regulated in clinical HCC specimens and its expression was inversely correlated with Egr1 expression. Functionally, overexpression of miR-181a-5p inhibited, whereas decreased expression of miR-181a-5p promoted HCC cells proliferation in vitro. Furthermore, we demonstrated that miR-181a-5p overexpression directly suppressed Egr1, resulting in a down-regulated TGF-β1/Smad pathway. Besides, the silenced Egr1 expression could rescue the enhanced cell proliferation induced by miR-181a-5p inhibitor. Thus, we concluded that miR-181a-5p is a negative regulator of Egr1 that can suppress tumor proliferation in HCC through targeting Egr1/TGF-β1/Smad pathway, which may be a potential therapeutic approach of HCC.