Mechanism Of TET1 Epigenetic Modification Of Gene BCL6B In The Regulation Of Gastric Cancer

Background and Objectives:As one of the most common malignancy of gastric cancer(GC) of digestive system, the incidence of GCranks fourth,mortality of GC ranks second worldwide. Although the diagnosis and treatment of gastric cancer has made great progress, in the last 10 years, the5 year survival rate was not significantly improved, postoperative recurrence and metastasis are important reasons for the high mortality. High morbidity and mortalitymake it difficult to solve of the research and treatment of gastric cancer.BCL6 B is an important tumor suppressor gene that it has been confirmedto be a major issue in the process and development of GC.The promoter GC island hypermethylation inactivate the tumor suppressor function in epigenetic has been confirmed. However, what are the mechanisms of epigenetic regulation of BCL6 B gene has not been reported.This is the first study of the mechanism of DNA hydroxylase TET1 epigenetic modification of tumor suppressor gene BCL6 B in the regulation of GC,intended to clarify the main reasons of alterations in methylation level of BCL6 B in the development of GC, which will reveal the mechanism of Tet1 regulatingthe tumor progression and drug resistance function of cancer cells and related downstream molecular regulation. The project's successful implementation will reveal a novel mechanism for the occurrence and development of GC, and may provide a new target for the clinical treatment and diagnosis of GC in epigenetic.Methods: In this experiment, we chose SGC7901 and its cisplatin resistant strains SGC7901/DDP as compared, western blot detected the expression of BCL6 B and use Methylmion Specific PCR(MSP) to detected BCL6 B in the promoter region methylation status of two cell lines; using lentiviral method to construct stable strain of BCL6 B knockdown in SGC7901 and overexpression in SGC7901/DDP. And the level of cisplatin cultured after growth curve of MTT was detected by comparing the experimental group and the control group of TET1 protein and m RNA expression of SGC7901 and SGC7901/DDP respectively; detectthe expression BCL6 B of two cell strains after the drug resistance experiment; in vivo SGC7901 and knockdown of SGC7901, stable transfection strains were measured in situ transplantation, tumor volume,quality, analysis of liver and lung metastasis.Results: Compared with SGC7901/DDP, the promoter methylation of BCL6 B in SGC7901 is low. The protein and m RNA expression also significantly reduced. In BCL6 B knockdown of SGC7901, TET1 expression was also reduced; after dosing cisplatin measuring growth curve showed BCL6 B knockdown of SGC7901 strains with high survival rate than the control group of SGC7901. In BCL6 B overexpression of SGC7901/DDP strains, TET1 expression was also up-regulated;after cisplatin dosing measuring growth curve showed that BCL6 B overexpression of SGC7901/DDP strains with low survival rate compared with the control group. The DDP-resistant experiment of SGC7901 and SGC7901/DDP show the expression of BCLB both reduced after dosing, and change followed different drug concentration. In vivo SGC7901 and BCL6 B knockdown stable transfection strains after situ transplantation,the tumor growth rate and tumor formation rate, tumor size of SGC7901 were significantly lower than that of BCL6 B knockdown.Conclusions: The experimental results show that the BCL6 B methylated highly in GC cell lines, TET1 in epigenetic regulation of high methylation of gene BCL6 B promoter plays an important work, and the expression level of BCL6 B gene will be a negative feedback effect on expression of TET1 gene.High degree of BCL6 B gene's methylation in GC is closely related to tumor's malignancy which suggests methylation of BCL6 may be an indicator of the prognosis and a detective marker of GC. Through removal the methylation of BCL6 B promote by express TET1, and increase BCL6 B expression to inhibit the growth of tumor development may be used in GC in future. But the role BCL6 B played on the invasion and metastasis of GCand the mechanism of TET1 still need further study.