| Gastric cancer(GC)is the most common malignant neoplasm of digestive system.In China,the incidence and mortality of gastric cancer are ranked in the top three,which is severely threatening the human health.Because the development and progression of gastric cancer is extremely secretive,most patients were diagnosed with the middle and late stages of the disease.And the traditional surgical treatment or radiotherapy and chemotherapy is less effective.So far,the pathogenesis of gastric cancer has not completely clear,treatment of this cancer has not significantly break through,which can't meet the clinical requirement in the prevention and treatment of this disease.Therefore,exploring the pathogenesis of gastric cancer,finding new tumor markers and gene therapy targets for early diagnosis,recurrence and metastasis prediction and prognosis evaluation of gastric cancer play an important role in the prevention and treatment of gastric cancer.EphB3 is a member of the EPH receptor family and has been found to play an important role in the development of cancer.However,the expression and clinical significance of EphB3 in gastric cancer is not clear.Objective: To investigate the function of EphB3 on proliferation and metastasis in GC through clinical tissues,cell lines and xenograft tumors in vivo,and explore its underlying mechanism.Methods: In our study,The m RNA and protein expression levels of EphB3 were detected by reverse transcription polymerase chain reaction(RT-PCR)and Immunohistochemistry(IHC)in 120 matched gastric cancers and corresponding adjacent tissues of GC patients.Western blot was used to detect the expression of EphB3 in 30 pairs of matched gastric cancer tissues and gastric cancer cell lines.The relationship between EphB3 expression and clinical pathology of GC was analyzed.By silencing or overexpressinng EphB3 in GC cells,cell proliferation,invasion and metastasis were detected using the CCK-8 assay,wound healing assay and Transwell assay.The effect of EphB3 on the tumorigenic ability of gastric cancer cells was studied by nude mice.Chromosome immunoprecipitation(CHIP)and firefly luciferase assays were used to detect the relationship of enhancer of zeste homolog 2(EZH2)and EphB3.Moreover,the correlation between EphB3 expression and clinicopathological variables or disease-free survival(DFS)was analyzed by 120 GC samples.Results: In this study,we found EphB3 is downregulated in 75%(90/120)GC cells and tissues(P < 0.01).The expression of EphB3 was negatively correlated with gastric cancer tissue size(P=0.028),invasion depth(P=0.020),lymph node(P=0.026)metastasis and staging(P=0.017).Of most relevance,translation of these findings into human GC tissue samples demonstrated that patients with low levels of EphB3 expression had a shorter DFS(18m vs30 m,P=0.004).Knockdown of its expression leads to cell growth arrest and invasion inhibition,while transfection of EphB3 into GC cells resulted in a significant anti-tumoral effect,both in culture and in xenografted nude mice.Moreover,EphB3 was found to have a key role in the epithelial–mesenchymal transition through the regulation of E-cad and Vimentin expression.We showed that epigenetic silencing of EphB3 occurs in GC cells through direct transcriptional repression mediated by the Polycomb group protein enhancer of zeste homolog 2(EZH2).Conclusion: EphB3 expression was significantly lower in the tumor tissues and gastric cancer cell lines than in the adjacent normal tissues and normal gastric epithelium cell line.EphB3 downregulation in GC was mediated by the EZH2.EphB3 inhibit the proliferation and metastasis of gastric cancer cells.EphB3 may serve as a promising diagnostic and prognostic biomarker. |
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