Role Of Histone Modification In The Carcinogenesis And Progression Of Gastric Cancer

Part one:Role and correlation of H3K27me3and EZH2in gastric tumorigenesis.Objective:To investigate the expression of H3K27me3and EZH2in multi-stage tissues of gastric carcinogenesis and gastric cancer cell lines, and to evaluate its possible correlation with clinicopathological factors of gastric carcinoma.Methods:Immunohistochemistry(IHC) was utilized to examine the protein expression of H3K27me3and EZH2in153tissue specimens including20of normal gastric epithelium tissue,21of intestinal metaplasia (IM),24of dysplasia (DYS),23of early gastric cancer (EGC) and65of advanced gastric cancer (AGC). The expression of H3K27me3and EZH2were detected by Western Blot in gastric cancer lines SGC7901, BGC823, AGS and normal gastric mucosal epithelium cell GES-1.Results:1. The high expression of H3K27me3was found in2(10.0%) of normal tissue,4(19.0%) of IM,7(29.2%) of dysplasia,9(39.1%) of EGC and 35(53.8%) of AGC. In precancerous and EGC groups, which include IM, DYS, and EGC groups, the expression of H3K27me3wasn’t associated with clinicopathological characteristics such as age, sex, location of lesion and tumor markers, however, in progressive GC group, the expression levels of H3K27me3significantly associated with tumor size, the depth of invasion, lymph node metastasis, vascular invasion, clinical stage, T staging (P<0.05).2. The high expression of EZH2was showed in0(0.0%) of normal tissue,5(23.8%) of IM,11(45.8%) of dysplasia,12(52.2%) of EGC and37(56.9%) of AGC. In IM, DYS and EGC groups, the expression of EZH2wasn’t correlated with clinicopathological characteristics such as age, sex, location of lesion and tumor markers, however, in AGC group, the expression levels of EZH2significantly associated with tumor size, the depth of invasion, lymph node metastasis, vascular invasion, nerve invasion, clinical stage and T staging (P<0.05).3. The correlation of H3K27me3and EZH2was only observed in early GC and progressive GC groups by Sperman correlation analysis.4. H3K27me3and EZH2expression were significantly increased in gastric cancer lines SGC7901、 BGC823、AGS compared with normal gastric mucosal epithelium cell GES-1.Conclusion:H3K27me3and EZH2play an important role in the Carcinogenesis and Progression of GC. High expression of H3K27me3and EZH2, as detected by IHC and WB, may be important prognostic factors in patients with gastric cancer. Part two:Expression of DNMT1, EZH2and HDAC1in gastric cancer and their interactionsObjective:To study the expression of DNMT1,EZH2and HDAC1in gastric cancer cell lines and tissue, and investigate interactions between three candidate proteins.Methods:Realtime-PCR and Western Blot were utilized to examine the mRNA and protein expression of DNMT1, EZH2and HDAC1in gastric cancer lines MKN28, SGC7901, BGC823, AGS and10cases of gastric cancer tissue. The interactions between protein of DNMT1, EZH2and HDAC1was detected by Co-IP in gastric cancer cell lines and tissue.Results:High expression of DNMT1, EZH2and HDAC1, as detected by Realtime-PCR and WB, was found in gastric cancer cell lines and tissue compared with the corresponding control group. DNMT1, EZH2and HDAC1form complex in the high, medium, and poorly differentiated gastric cancer cells and the medium, medium-low, poorly differentiated gastric cancer tissues.Conclusion:Our findings indicate that DNMT1, EZH2and HDAC1expression are severely improved and interacts with each other in gastric cancer. The interactions between DNMT1, EZH2and HDAC1may be an important mechanism accounting for the correlation of DNA methylation and histone modifications in gastric cancer.