The Role And Mechanism Of Long Noncoding RNA-GMAN Promotes Hepatocellular Carcinoma Progression By Combing With EIF4B

BackgroundHepatocellular Carcinoma(HCC)is a common malignant tumor in China.Most HCC patients have lost the opportunity for radical surgery due to the difficulty of early diagnosis.Although radical resection is available,the overall five-year survival rate after surgery is less than 30% due to high recurrence after surgical resection.Therefore,it is an urgent improtant to find new molecular mechanisms of the occurrence and development of HCC and to discover new therapeutic targets.Long noncoding RNAs(lncRNAs)are a class of transcripts with a length of more than 200 base pairs that have no protein-coding ability.Accumulating evidence showed that aberrant lncRNAs participate in the regulation of many biological functions such as proliferation,migration,invasion and apoptosis of many types of tumors.Lnc RNA-GMAN is a newly discovered sense lncRNA,which is located in the ephrin A1 gene cluster.In gastric cancer,lncRNA-GMAN can competitively interact with its corresponding antisense lncRNA to improve the translation of ephrin A1 and boost invasion and metastasis.However,the functions and mechanisms between lncRNA-GMAN and HCC are unclear.AimsThe study aims to study the expression pattern of lncRNA-GMAN in hepatocarcinoma tissues and its correlation with clinicopathological data and prognosis.We explore the effects of lncRNA-GMAN on the biological functions of HCC and identify the mechanisms of lncRNA-GMAN on the occurrence and development of HCC.MethodsThe association between lncRNA GMAN expression and clinicopathologic characteristics and prognosis in patients with HCC was analyzed by quantitative PCR(q RT-PCR).RNA levels were knocked down in SMMC-7721 and LM3 cell lines with high expression of lncRNA-GMAN using small interfering and lentivirus.Genes were overexpressed by transfected plasmids in MHCC-97 H cell with low expression of lncRNA-GMAN.The effects of lncRNA-GMAN on HCC cells were evaluated by CCK8 assay,colony formation assay,cell migration assay,cell invasion assay,cell cycle assay,cell apoptosis assay and nude mouse xenograft tumor formation assay.RNA-pulldown,mass spectrometry,RNA immunoprecipitation and WB assays were used to identify lncRNA-GMAN-specifically bound protein.ResultsThe expression of lncRNA-GMAN in HCC tissues was significantly higher than that in adjacent tissues and higher lncRNA-GMAN expression is associated with vascular invasion,histologic grade,TNM stage,short overall survival and disease-free survival.Lnc RNA-GMAN inhibited cell apoptosis,promoted cell migration and metastasis,but had no effect on cell proliferation and cell cycle.Knockdown of lncRNA-GMAN inhibited the formation of subcutaneous tumors and lung metastases in nude mice.Mechanistic analyses indicate that GMAN directly combines with eukaryotic translation initiation factor 4B(e IF4B)and promotes its phosphorylation at serine-422 by preventing e IF4 B binding and dephosphorization of the protein phosphatase 2A subunit B.The stability of p-e IF4 B increases anti-apoptosis-related protein and epithelial-mesenchymal transition-related(EMT)protein expression,further inducing cell survival,invasion and metastasis in HCC.ConclusionGMAN is upregulated in HCC tissues and serves as a poor prognostic of HCC.Inhibition of apoptosis,rather than promotion of proliferation,is responsible for GMAN-enhanced cellular viability.Lnc RNA-GMAN combines wtih e IF4 B and increases its phosphorylation level by competitively binding PP2R2 A,further increasing the expression of anti-apoptotic protein and EMT-related protein and promoting tumor survival,invasion and metastasis.