The Role Of Pseudouridine Synthase PUS7 In Gastric Carcinogenesis

Gastric cancer is one of the malignant tumors with high morbidity and mortality in the world.Although the incidence of gastric cancer has been declining by years worldwide for the past few years,it still remains high in China along with high mortality.Usually,there is no obvious symptoms in the early stage of patients with gastric cancer.Patients are often diagnosed at the advanced stages,and their prognosis is generally poor.Therefore,exploring the molecular regulatory mechanism in the development of gastric cancer is helpful to discover biomarkers and therapeutic targets for early diagnosis of gastric cancer,which is of great significance for improving the survival rate of gastric cancer patients.RNA modification refers to various chemical modifications that occur on the bases of RNA,which can affect the stability and metabolic regulation of RNA.RNA modification plays an important role in the regulation of physiological functions,and its abnormality is closely related to the diseases.Pseudouridylation is one of the earliest discovered and most abundant types of RNA modification.Pseudouridine synthases(PUS)are enzymes that convert uracil into pseudouracil,which play important roles in the regulation of RNA metabolism and cell biological functions.However,the regulation and molecular mechanism of pseudouridylation in tumorprogression has not been studied yet.We detected the RNA expression levels of PUS in gastric cancer tissues,and found that there were significant expression differences in the m RNA expression of PUS7 in gastric cancer tissues compared with adjacent tissues.Additionally,we applied immunohistochemistry on tissue array to detect the protein expression level of PUS7,and found that PUS7 protein was significantly downregulated in gastric cancer tissues.First,we used gastric cancer cell lines to perform in vitro functional experiments,and found that downregulation of PUS7 significantly promote the migration and invasion of gastric cancer cells and the ability of soft agar clone formation.Importantly,overexpression of PUS7 significantly inhibits the formation of soft agar clones,but not PUS7 mutants(enzyme deactivation mutant of PUS7).Since the cloning ability of soft agar is related to stemness of gastric cancer cells,we further tested the effect of PUS7 on the expression of gastric cancer stemness-associated genes.We found that overexpression of PUS7 inhibits the expression of stemness-associated genes in gastric cancer cells,but not PUS7 mutants.These results suggest that PUS7 can inhibit the formation of soft agar clones and the expression of stemness-associated genes in gastric cancer cells,and this regulation is related to its enzymatic activity as a pseudouridine synthase.In addition,we found that overexpression of PUS7 can significantly reduce mouse subcutaneous tumorigenesis.In summary,PUS7 protein is significantly downregulated in gastric cancer tissues,and overexpression of PUS7 in gastric cancer cells can significantly inhibit mouse subcutaneous tumorigenesis.PUS7 inhibits the formation of soft agar clones and the expression of stemness-associated genes in gastric cancer cells,which is related to its enzymatic activity as a pseudouridine synthase.These results suggest that dysregulation of pseudouridylation may be involved in the development of gastric cancer.