PRMT5 Regulates Cell Proliferation In Human Gastric Cancer

Gastric cancer(GC)is one of the most common carcinomas in the world which threatens the health of people in China.The incidence and fatality rate of gastric cancer ranks the second in China.Although the incidence of GC is declining and the surgery and chemotherapy partially improve the survival of patients,the poor understanding of the mechanism of its progression prevents the further development of therapeutic approaches.The prognosis of patients remains dismal.An extensive understanding of the molecular biology of GC is highly under requirement.Protein arginine methyltransferase 5(PRMT5)catalyzes the symmetrical dimethylation of arginine residues of histone and non-histone substrates implicated in diverse biological processes.PRMT5 is expressed at a higher level compared with normal tissues in lymphomas,ovarian,breast,lung cancers,etc.In order to study the expression of PRMT5 in GC tissues,we investigated the expression of PRMT5 protein in human GCs and adjacent tissues by immunohistochemistry(IHC).Experimental results show that the levels of PRMT5 protein is higher in GCs compared with adjacent tissues.To further probe the biological function of PRMT5 in SGC7901 GC cells,we interfered PRMT5 expression using specific siRNAs.We evaluated the proliferation of SGC7901 cells by CCK-8,EdU and colony formation assays.Results show that PRMT5 knockdown significantly decreased the proliferation ability of SGC7901 cells.To further detect the influence of PRMT5 on the tumor growth potentiality,a xenograft tumor growth assay was performed with nude mice.Results show that tumor cells with PRMT5 knockdown grow more slowly than the scrambled control in the same mouse.In short,interfering PRMT5 expression markedly inhibit the proliferation of GC cells in vivo.To detect the specific mechanism by which PRMT5 regulates the proliferation of GC cells,we screened some genes related to proliferation and cell cycle after interfering PRMT5 expression via quantitative real-time reverse-transcription polymerase chain reaction(qRT-PCR)assays.We found that PRMT5 played a negative regulation role in the phosphatase and tensin homolog(PTEN)expression.PTEN as a crucial tumor suppressor plays a vital role in maintaining normal cell activities and functions.Studies have shown that PTEN undergos mutation or loss in many human cancers.To verify the specific mechanism of PTEN regulation by PRMT5,we interfered PRMT5 expression in SCG7901 cells and utilized western blot assay to detect the expression change of PTEN.Our results show that PTEN protein expression is up-regulated after interfering PRMT5 expression.To confirm that PRMT5 directly regulates PTEN expression,we used chromatin immunoprecipitation(ChIP)assay to detect the binding of PRMT5 on the promoter of PTEN.Results show that PRMT5 can bind the promoter of PTEN.Furthermore,the enrichment of epigenetic marker H4R3me2s on the promoter of PTEN significantly decreased in PRMT5 knockdown GC cells.An IHC assay and a correlation analysis were used to demonstrate the negative correlation between PRMT5 and PTEN.These results demonstrated PRMT5 could repress PTEN expression to promote cell proliferation.In summary,we studied the role of PRMT5 in the development and progression of gastric cancer by in vitro and in vivo experiments.These results provide a potential new strategy for the diagnosis and treatment of gastric cancer.