Methylation of Epstein-Barr Virus-Associated Gastric Cancer Suppressor Genes

Objective: To identify the methylation silenced tumor suppressor genes in Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC). Methods: EBV-positive (GT38, PT and SNU719) and negative (SGC7901) gastric cancer cell lines were selected and treated with 5-Aza-CdR. Then real-time fluorescence quantitative PCR was used to validate the results of microarray, and methylation-specific PCR (MSP) and bisulfite genomic sequencing (BGS) were adopted to detect the CpG island methylation levels of gene promoters. Results: The expression levels of 6 differentially expressed genes (H19, LOXL1, ARMCX2, LXN, CDH3 and MMP7) before and after 5-Aza-CdR treatment were confirmed by real-time qPCR, which are consistent with the results of microarray analysis. There were different degrees of methylation in LOXL1 gene promoter in EBVaGC. GT38 and PT were fully methylated, and SGC7901 and HGC-27 was unmethylated, suggesting that this gene is a candidate methylation silenced tumor suppressor gene. The methylation rate of LOXL1 in EBVaGC was significantly higher than that in EBV-negative gastric cancer (EBVnGC). Conclusion: The promoter region of candidate tumor suppressor gene LOXL1 shows high methylation status, indicating that EBV critically accounts for the methylation of LOXL1 gene regulatory region. EBV is involved in the pathogensis of EBVaGC that aberrant methylation occurred in promoter CpG island, which inactivates tumor suppressor genes.