The Role And Mechanism Of SIRT6 In Gastric Cancer

Objective:To investigate the expression of SIRT6 in human gastric cancer tissues and normal tissues,as well as in gastric cancer cell lines and normal gastric epithelial cells,and to determine the role of SIRT6 in gastric cancer and explore its molecular mechanism.To provide new ideas and theoretical basis for prognostic and molecular targeted therapy of patients with gastric cancer.Methods:The online database(Oncomine)was applied to analyze the expression of SIRT6 in gastric cancer tissues and the website Kmplot was used to determine the relationship between the expression of SIRT6 and the prognosis of gastric cancer.Western blotting,qPCR and IHC were performed to detect the expression of SIRT6 in gastric cancer tissues and adjacent normal tissues or in normal gastric mucosal cells and gastric cancer cell lines;SIRT6 silencing or overexpression cell models were constructed by transient transfection of siRNA or pcDNA-SIRT6 plasmids;CCK8 analysis and colony formation assays were used to detect proliferation of cells.Transwell experiments were used to detect cell migration.CCK8 assay and western blot were also used to determine chemo-sensitivity of tumor cells.Western blot was further used to explore the effect of ectopic SIRT6 expression on EMT,CSC and potential downstream mediated signaling pathways in gastric cancer.Results:Database analysis and results of IHC,qPCR and western blot showed that the expression of SIRT6 in gastric cancer tissues was significantly higher than that in adjacent non-cancerous tissues.High expression of SIRT6 was observed in gastric cancer cell lines.The overall survival rate and disease-free survival rate of higher SIRT6 expression patients were lower than those of patients with low expression of SIRT6;SGC-7901 SIRT6 overexpression cells were found shown increased migration rate,accelerated proliferation ability and larger size and number of cell clones,reduced cell chemo-sensitivity.The EMT and CSC progression of SGC-7901 cells with SIRT6 overexpression were all enhanced to some extent.For epithelial-mesenchymal-transition(EMT)progression,the expression of epithelial cell surface marker(E-cadherin)decreased,the expression of mesenchymal cell surface markers(N-cadherin,Vimentin,Twist1 and Snail)showed a significant increasement,the expression of various cancer stem cell markers(CD133,Oct4,Sox2 and Nanog)was increased.The results of pathways analysis showed that the overexpression of SIRT6 inhibited the expression of TGFβ pathways through suppressing TGFβ1 and P-SMAD2 / 3 in SGC-7901 cells.After silencing SIRT6,MGC-803 cells showed weakening of migration ability and slowing down of proliferation.After interference of SIRT6 in MGC-803 cells,the cells showed inhibition of EMT and CSC,and the increasement of drug sensitivity.Western blot assays showed that TGFβ and its downstream regulating molecules P-SMAD2 / 3 and P-ERK1 / 2 were suppressed in MGC-803 cells upon SIRT6 knockdown.Conclusions:SIRT6 may play a crucial role in the occurrence and development of gastric cancer.SIRT6 may promote tumor cell proliferation,metastasis and chemotherapeutic drug resistance by activating TGFβ-induced EMT and CSC in gastric cancer cells.SIRT6 is expected to be a potential indicator for the assessment of gastric cancer metastasis and prognosis,and could provide new ideas for the treatment of gastric cancer.