| Cell junctions are an important basis for the intercellular and cytoplasmic intercellular interactions and synergies between adjacent cells in a multicellular organism.There are four forms in humans and animals,tight junction is one of the most important ones.The tight junction is the most potent component of the cell / cell complex,which is the primary barrier to the passage of the liquid and solute through the cell gap and plays a critical role in regulating the balance between cell proliferation,differentiation and apoptosis,which is mainly composed of claudins,occluding,JAMs,secretory proteins(ZO-1,ZO-2 and Z0-3),and other cytoplasmic proteins,among which claudin is tightly connected to the most important components,mainly determining the structure and function of the tight connection.The expression of CLDNs is often altered in tumors,for instance,the expression of CLDN1 was downregulated in esophageal cancer,the expression of CLDN7 was down-regulated in pancreatic ductal carcinoma,the expression and localization of CLDN4 in bladder cancer were both changed.As a consequence,it has been speculated that changes in the expression or localization of CLDNs lead to the destruction of the structure and function of tight junctions and thus contribute to the development of tumors.CLDN 4,a member of 27 family members,is a receptor for the C-terminal fragment of Clostridium perfringens(CPE).CLDN 4 interacts with CLDN 4 on the adjacent cell surface by the action of the extracellular loop,which is such that CLDN 4is confined to the tight junction structure and provides a good barrier for cell proliferation.Studies have shown that the downregulation of CLDN4 expression in bladder cancer is due to hypermethylation in its promoter region.In our preliminary work,we found that compared with paracancerous tissue,the expression of CLDN 4in laryngeal squamous cell carcinoma was significantly down-regulated,theexpression of methylated protein Me CP2 was up-regulated,and there was a correlation between them two.And the expression of CLDN4 was up-regulated after administration of 5-aza-d C to hep-2 cells,and upregulation of CLDN4 can inhibit the proliferation,migration and invasion of hep-2 cells.Then whether 5-aza-d C up-regulates CLDN4 expression is achieved by directly altering its DNA methylation status and whether the malignant phenotype of hep-2 cell is regulated by CLDN4 is the key problem to be solved in this study.Aim: To investigate the relationship between the down-regulation of CLDN4 expression and methylation in laryngeal carcinoma hep-2 cells and the effects of down-regulation of CLDN4 expression on proliferation and invasion of laryngeal carcinoma hep-2 cells and other malignant phenotypes.Methods: Methylation specific PCR(MSP)was used to detect the effect of5-aza-d C on the DNA methylation of CLDN4 gene.CCK8 assay ?wound-healing test and Transwell chamber was used to analysis the effect of CLDN4 gene on the proliferation?migration andinvasive ability of hep-2 cells in silencing 5-aza-d C group.Results:1?DNA methylation of CLDN4 gene was detected in hep-2 cells with low expression of CLDN4,and DNA methylation of CLDN4 gene was not detected in5-aza-d C-treated group of hep-2 cells.2?The proliferation,migration and invasion of hep-2 cells in the silencing 5-aza-d C group were significantly enhanced.Conclusions: In summary,this study shows that down-regulation of CLDN4 expression in laryngeal carcinoma hep-2 cells was associated with DNA methylation;DNA methylation down-regulation of CLDN4 expression can promote the malignant phenotypes of laryngeal hep-2 cells. |
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