Protein Arginine Methyltransferase 4 Promotes Hepatocellular Carcinoma Progression By Activating AKT/mTOR Pathway

Objective:PRMT4 is a member of the type I protein arginine methyltransferase family,it is a co-activator of many nuclear receptors and transcription factors,and plays an important role in regulating cellular transcription,RNA splicing,DNA repair,cell signal transduction,etc.It is involved in regulating cell proliferation,differentiation and apoptosis.Numerous studies have reported that PRMT4 is aberrantly expressed in a variety of human malignancies,including breast,lung,colorectal,and prostate cancers.However,the mechanism of PRMT4 in the occurrence and progression of hepatocellular carcinoma(HCC)has not been fully studied.In this study,the construction of lentivirus and plasmid vectors were used to transfect corresponding liver cancer cell lines,and the relationship between PRMT4 expression and liver cancer cell proliferation and invasion was investigated by up-regulating and downregulating the expression of PRMT4,and to explore its possible molecular mechanism.The path of treatment and prolonging the survival of patients are of great significance.Methods:1.The tumor tissue and corresponding non-tumor tissue samples of 30 clinically diagnosed hepatocellular carcinoma were collected for real-time quantitative PCR analysis to evaluate the differential expression of PRMT4 m RNA in hepatocellular carcinoma and the corresponding adjacent tissue.The relationship between PRMT4 expression and hepatocellular carcinoma was analyzed.The expression and pathological characteristics of PRMT4 were studied by immunohistochemical analysis of HCC tissue microarray(TMA)samples from 140 clinically diagnosed patients.The clinical data of the corresponding patients were collected,and the relationship between PRMT4 expression and clinicopathological characteristics was analyzed.2.Western blot was used to detect the expression level of PRMT4 in liver cancer cell lines(YY-8103,Hep3 B,SNU-398 and Huh7)and normal liver cell line THLE2,and select a suitable liver cancer cell line as an in vitro experimental model.Lentivirus and plasmid vectors were constructed for cell transfection to silence and overexpress PRMT4 in the corresponding liver cancer cell lines.CCK-8 assay and Transwell assay were used to detect cell proliferation,migration and invasion in the transfected liver cancer cell lines.condition.The PRMT4-overexpressing liver cancer cell lines were treated with a specific inhibitor of AKT(MMK2206)and a specific inhibitor of mTOR(rapamycin)respectively and the changes in cell proliferation,migration and invasion after the inhibitor treatment were detected and explored the mechanism of PRMT4 by Western Blot.Results:Compared with adjacent tissues,PRMT4 was highly expressed in HCC tissues(P<0.05).The expression of PRMT4 was significantly correlated with alphafetoprotein level,tumor size,satellite nodules and microvascular infiltration(P<0.05).The results of in vitro experiments showed that overexpression of PRMT4 promoted the proliferation,migration and invasion of hepatoma cells in vitro,while downregulation of PRMT4 expression inhibited these malignant behaviors(P<0.05).Mechanistic experiments showed that the phosphorylation expression of AKT/mTOR signaling pathway proteins was up-regulated in PRMT4-overexpressed liver cancer cell lines.The use of this pathway inhibitor MK2206 or rapamycin could significantly attenuate PRMT4 and promote the proliferation and migration of liver cancer cells.and invasive ability(P<0.05).Conclusion:PRMT4 is highly expressed in HCC tissues and cells,and indicates poor prognosis;PRMT4 expression was not significantly correlated with gender,age,HBsAg infection,tumor number,and lymph node metastasis in HCC patients,but was significantly correlated with AFP,tumor size,satellite nodules and microvascular invasion Correlation;Up-regulation of PRMT4 in vitro promotes the proliferation,migration and invasion of liver cancer cells,while down-regulation of PRMT4 in vitro inhibits the proliferation,migration and invasion of liver cancer cells;PRMT4 promotes the progression of HCC by activating the AKT/mTOR signaling pathway.