Study On Methylation Of The Tumor Suppressor Gene In Epstein-Barr Virus-associated Gastric Carcinoma

Epstein-Barr virus (EBV) is an important DNA virus, which has a close relationship with many kinds of human malignant tumor. DNA methylation is the most cutting-edge and the most studied epigenetic mechanism. Besides mutation and deletion, the hypermethylation of tumor suppressor gene promoter is considered the key mechanism of inactivation in the tumor.Objective To identify the methylation silenced tumor suppressor genes in EBVaGC.Methods Agilent Human Whole Genome Expression Profiling (4×44K) chips were used to compare the changes in gene expression profiles following the treatment of 5-Aza-CdR in EBVaGC (PT,GT38 and SNU719) and EBVnGC (SGC7901) cell lines. real-time qPCR was used to validate the results of microarray, MSP and BGS was adopted to detect the methylation levels of gene promoters.Results①T he differential expression genes were identified by microarray analysis, up-regulated genes:GT38,860 genes; PT,804 genes; SNU719,1099 genes; SGC7901,5924 genes. Down-regulated genes:GT38,679 genes; PT,667 genes; SNU719,667 genes; SGC7901,5882 genes.②A total of 42 up-regulated genes were found in three EBVaGC (PT, GT38 and SNU719) cell lines. The functions of these genes were involved in tumor suppression, immunity, cell adhesion, cell cycle, cell proliferation, apoptosis, signal transduction and etc. Compared to the EBVnGC cell lines,19 differential genes were found in these 42 selected genes.③The expression levels of 6 differential genes (H19, LOXL1, ARMCX2, LXN, CDH3 and MMP7) in 5-Aza-CdR treated cells were confirmed by real-time qPCR, which were consistent with the results of microarray.④The methylation status of LOXL1 was detected by MSP and BGS in cell lines. The results showed that the promoter of LOXL1 was hypermethylation in different degrees, suggesting that this gene as candidate methylation silenced tumor suppressor gene.⑤The methylation rates of LOXL1 in EBVaGC were significantly higher than those in EBVnGC.Conclusion①The expression chip screens 19 genes silenced by methylation and reactivated by 5-Aza-CdR in EBVaGC. These genes may play an important role in the pathogenesis of EBVaGC.②The promoter methylation of LOXL1 is an important regulation mechanism of gene expression. It suggested LOXL-1 is a methylation silenced tumor suppressor gene in EBVaGC. The hypermethylation of tumor suppressor gene promoter induced by EBV may play an important role in the pathogenesis of EBVaGC...