The Role And Underlying Mechanism Of Protein Arginine Methyltransferase 3 In Promoting Glycolysis And Hepatocellular Carcinoma Growth

Aims: The incidence of hepatocellular carcinoma(HCC)ranks fifth among various cancers in our country,and is the second leading cause of cancer-related mortality.Lack of effective molecular targeted therapy is one of the challenges in the field of HCC therapy.Epigenetic modification plays a critical role in tumorigenesis and progression of HCC,and its reversibility provides more opportunities for cancer therapy.In the past,the studies on protein methylation modification focused on lysine sites.With the development of biological technology,arginine methylation modification has gradually attracted more attention.More and more studies have confirmed the important role of protein arginine methyltransferase(PRMTs)family in tumorigenesis and progression.The role of PRMT3 in HCC is still unknown.This study aims to explore the role of PRMT3 in HCC progression,as well as the underlying molecular mechanisms,thereby providing experimental evidence to find novel targets for HCC therapy.Methods: RT-q PCR,Western blotting,and immunohistochemical assays were used to determine the expression patterns of PRMT3 in HCC.Loss-of-function and gain-offunction experiments were carried out to determine the oncogenic role of PRMT3 in HCC.Glucose consumption and lactate production assays,seahorse bioscience,mass spectrometry,co-immunoprecipitation,metabonomic analysis and site-specific mutation experiments were used to explore the underlying molecular mechanisms.Furthermore,a xenograft mouse model was established to investigate the effects of PRMT3 and its inhibitor,SGC707,treatment on tumor growth in vivo.Results: The expression of PRMT3 was significantly upregulated in HCC,with high expression of which correlated with poor prognosis.PRMT3 knockdown led to the decrease in proliferation,glycolysis of HCC cells and tumor growth,whilst its overexpression showed opposite results.The catalytic activity of PRMT3 was important in mediating these biological processes.Mechanistically,our data showed that PRMT3 interacted with and mediated asymmetric dimethylarginine(ADMA)modification of lactate dehydrogenase A(LDHA)at arginine 112(R112).Compared with LDHA-wild-type(LDHA-WT)cells,LDHA-R112K-mutant-expressing HCC cells exhibited a decrease in lactate dehydrogenase(LDH)activity,HCC cell glycolysis and proliferation.Furthermore,the administration of SGC707,a selective inhibitor of PRMT3,disrupted the PRMT3-mediated LDHA methylation and abolished PRMT3-induced HCC glycolysis and tumor growth.Conclusions: Our results suggested a novel oncogenic role of PRMT3 in HCC,and it could be a promising therapeutic target for HCC by linking posttranslational modification and cancer metabolism.