| Background: In esophageal squamous carcinoma has high morbidity and mortality,its diagnosis often is middle-late,5 years of survival rate of less than 25%,therefore,a deeper understanding of the molecular mechanism of esophageal squamous carcinoma(ESCC)development,screening effective biomarkers,to improve the early diagnosis of esophageal squamous carcinoma and the status quo of the clinical treatment is of great significance.It is well known that epigenetic changes,including DNA methylation and covalent histone modification,play a key role in the occurrence and development of human cancer.The role of trimethylated H3K27(H3K27me3)and methylated H3K9(H3K9me2)expression in the prognosis of patients with different types of human cancer is not yet clear,and further studies are actually needed in different cancer patients.Therefore,we explored the mechanism of the role of H3K27me3 in the malignant progression of esophageal squamous cell carcinoma.Methods: 1.135 patients with esophageal squamous cell carcinoma and normal esophageal mucosal tissue samples were selected from the thoracic surgery department of Fujian cancer hospital.The expression of H3K27me3 and H3K9me2 were detected by immunohistochemical staining and the relationship between its expression and clinical pathological manifestations was analyzed.However,there was no significant difference between the expression of H3K9me2 in esophageal squamous cell carcinoma and that in normal esophageal mucosa.2.Ch IP-seq technology was used to obtain DNA sequences binding to H3K27me3 protein,and the downstream target genes regulated by H3K27me3 were screened through bioinformatics.3.EZH2 inhibitor was used in the esophageal squamous cell carcinoma cell line EC9706,and the expression of EZH2,H3K27me3 and GADD45 G in the esophageal squamous cell carcinoma cell line was detected by western blot assay,q RT-PCR assay.Based on the overexpression plasmid designed for GADD45 G gene,the cell function experiment was conducted to investigate the effect of GADD45 G on the proliferation,migration and invasion ability of esophageal squamous cell carcinoma cells.The effect of overexpression of GADD45 G gene on the growth of esophageal squamous cell carcinoma cells in immunodeficient mice was observed in the subcutaneous tumor-bearing model experiment.Results: 1.The expression of H3K27me3 in esophageal squamous cell carcinoma was significantly higher than that in the corresponding non-tumor esophageal mucosa,and the survival period of patients in the H3K27me3 high-expression group was lower than that in the H3K27me3 low-expression group.High expression of H3K27me3 was positively correlated with the progression of T stage of esophageal squamous cell carcinoma.Multivariate Cox regression analysis indicated that high expression of H3K27me3 could be an independent prognostic factor for esophageal squamous cell carcinoma.2.A comprehensive analysis of the H3K27me3 site in the esophageal squamous cell carcinoma cell line was conducted through Ch IP-seq,and the results indicated that the genes involved in the regulation of H3K27me3 were significantly enriched in the TP53-related pathways,and the intersection was found to be the common gene for the enrichment analysis of the tumor suppressor gene GADD45 G.3.After inhibiting the catalytic enzyme EZH2 of H3K27me3,the expressions of EZH2 and H3K27me3 decreased significantly.The decreased expression of H3K27me3 can increase the expression of GADD45 G,and the overexpression of GADD45 G gene inhibits the proliferation,metastasis and invasion ability of esophageal squamous cell line EC9706.The results of subcutaneous tumor-bearing experiments in immunodeficient mice showed that GADD45 G inhibited the proliferation ability of esophageal squamous cell carcinoma cells in vivo.4.The expression of H3K27me3 in esophageal squamous cell carcinoma is positively correlated with EZH2 and negatively correlated with GADD45 G.Conclusion: H3K27me3 is highly expressed in esophageal squamous cell carcinoma tissues and promotes the malignant progression of esophageal squamous cell carcinoma by inhibiting the expression of the tumor suppressor gene GADD45 G. |
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