Demethylation Of TET1 Gene In Association With Pathogenesis Of Pancreatic Cancer

PURPOSE:Pancreatic cancer is one of the most common tumors in the digestive tract,with high incidence rate,high mortality rate and poor prognosis.DNA methylation and demethylation,a dynamic transformation between 5-methylcytosine(5-m C)and 5-Cytosine(5-C),play an important role in differentiation and tumorigenesis.Ten-eleven translocation 1(TET1)is a dioxygenase that converts 5-m C to5-hydroxymethylcytosine(5-hm C),induces Cp G island demethylation in various genes,and has been identified as a tumor suppressor in various types of cancers.However,the function of TET1 in pancreatic tumor is unknown.In this study,we focused on whether TET1 can inhibits pancreatic tumor and found the mechanism of TET1 in pancreatic tumor.METHODS:We collected pancreatic tumor tissue and paired adjacent non-tumor pancreatic samples from pancreatic tumor patients,detected the content of 5-m C,5-hm C and m RNA levels of TET1 in these samples by dot blot and real-time PCR,and analyzed the correlation between 5-hm C and TET1.We further analyzed the level of TET1 and patients' clinical parameters.Cell Counting Kit-8,flow cytometry,Edu staining,transwell assays,wound healing,mouse tumor xenograft were used to evaluate cell proliferation,cell cycle,apoptosis,migration and invasion in vivo and in vitro.RNA real-time PCR,western blot,immunofluorescence,co-immunoprecipitation,chromatin immunoprecipitation,immunohistochemistry,HE stain,Methylation Specific PCR,Bisulfite Sequencing PCR were used to investigate the molecular mechanism of TET1 in pancreatic tumor.RESULTS:We found that content of 5-hm C and expression of TET1 were decreased in pancreatic tumors and levels of TET1 was positively correlated with 5-hm C content.In clinical parameters analysis,Patients with low expression of TET1 had shorter time of 5-year overall survival times comparing the patients with high expression of TET1.Over-expression of TET1 inhibited pancreatic tumors proliferation and metastasis in vivo and in virto.Mechanistically,TET1-mediated the demethylation of the promoter of CDKN2A(p16),activated p16 expression,arrested the cell cycle in G0/G1 through the p16-CDK4/6-p Rb axis,and induced p16-dependent apoptosis.Besides,TET1 demethylated the promoter of SFRP2,activated SFRP2 expression and inhibited Wnt signaling pathway,inducing the suppression of EMT in pancreatic tumor.CONCLUSIONS:These results suggest that TET1 functions as a tumor suppressor in pancreatic cancer,arrests the cell cycle and induces apoptosis by activating p16 expression,inhibits Wnt signaling pathway,which induces the suppression of EMT in pancreatic tumor by activating SFRP2 expression.