LINC01980 Induced By TGF-beta Promotes Hepatocellular Carcinoma Metastasis Via MiR-376b-5p/E2F5 Axis

Objective: Hepatocellular carcinoma(Hepatocellular Carcinoma,HCC)is one of the most common human malignancies in the world,but the molecular mechanism of HCC metastasis is not fully understood.Long non-coding RNA have key roles in gene regulation,and its dysregulation is critical to cancer metastasis.In addition,TGF-β/SMAD signaling pathway often promotes tumor migration and invasion by inducing epithelial-mesenchymal transition.However,whether long non-coding RNAs are involved in the TGF-β/SMAD signaling during HCC metastasis is still poorly understood.The purpose of this study is to explore the function and mechanism of LINC01980 in HCC metastasis.Furthermore,the role of LINC01980 in the canonical TGF-β/SMAD signaling pathway is also investigated.Methods: qRT-PCR assay was used to test the expression of LINC01980,miR-376b-5p and E2F5 in HCC tissues and cell lines.Transwell assay was used to evaluate cell migration and invasion ability.Animal experiment was used to explore the effects of LINC01980 and E2F5 on HCC metastasis in vivo.Bioinformatic analysis,dual-luciferase reporter assay,RNA immunoprecipitation assay and biotinylated RNA Pull-down assay were performed to confirm the regulatory relationship between LINC01980,miR-376b-5p and E2F5.ChIP assay was used to prove the interaction between LINC01980 promoter and Smad protein complex.Results: LINC01980 was upregulated and associated with notably poor overall survival in HCC patients.In addition,LINC01980 expression was positively correlated with tumor grade and stage,and HCC patients with high LINC01980 expression were more prone to vascular invasion.Functionally,LINC01980 played a carcinogenic role and promoted HCC cells metastasis in vivo and in vitro.Further exploration revealed that LINC01980 was mainly located in the cytoplasm of HCC cells and directly bond to miR-376b-5p,while E2F5 was a direct target of miR-376b-5p in HCC cells.Mechanically,LINC01980 enhanced the expression of E2F5,the target gene of miR-376b-5p,through competitive binding of miR-376b-5p,thereby inducing epithelial-mesenchymal transition to promote the migration and invasion of HCC cells.In vitro and in vivo experiments,LINC01980-mediated HCC cells metastasis was dependent on E2F5.What’s more,TGF-β activated LINC01980 transcription through the canonical TGF-β/SMAD signaling pathway in HCC.Conclusions: LINC01980 promoted cells migration and invasion by sponging miR-376b-5p to increase E2F5 expression and induce epithelial-mesenchymal transition in HCC.TGF-βactivated LINC01980 transcription through the canonical TGF-β/SMAD3 pathway in HCC.Overall,this study provided a new perspective to understand HCC metastasis and offered a new potential target for treating hepatocellular carcinoma.