Role of DNA methylation in the development of Epstein–Barr virus‐associated gastric carcinoma

Abstract

The frequencies of DNA methylation of certain tumor-related genes are higher in Epstein-Barr virus (EBV)-associated gastric carcinomas than in EBV-negative gastric carcinomas. EBV-associated gastric carcinomas have distinct clinicopathological features; however, there are no case-control studies comparing methylation frequency between EBV-associated gastric carcinomas and controls that have been adjusted according to the clinicopathological features of EBV-associated gastric carcinomas. This study evaluated 25 EBV-associated gastric carcinomas that were positive for EBV-encoded small RNA 1 (EBER-1) by in situ hybridization and 50 EBV-negative gastric carcinomas that were matched with the EBV-associated gastric carcinomas by age, sex, histology, depth of tumor invasion, and stage. Methylation status of 16 loci associated with tumor-related genes was analyzed by methylation-specific polymerase chain reaction (PCR) to identify genes in which DNA methylation specifically occurred in EBV-associated gastric carcinomas. Methylation frequencies of 12 of the 16 genes were higher in EBV-associated gastric carcinomas than in EBV-negative controls, and the frequency of methylation of 6 specific loci (MINT2, MINT31, p14, p16, p73, and RUNX3) was significantly higher in EBV-associated gastric carcinomas than in EBV-negative controls. There were no significant differences in the methylation frequencies of the other genes. The mean methylation index in EBV-associated gastric carcinomas was significantly higher than that in EBV-negative controls. DNA methylation of tumor suppressor genes that regulate the cell cycle and apoptosis specifically occurred in EBV-associated gastric carcinomas. Aberrant DNA methylation might lead to the development and progression of EBV-associated gastric carcinoma.

Decitabine inhibits tumor cell proliferation and up‐regulates e‐cadherin expression in Epstein–Barr virus‐associated gastric cancer

“…CpG island methylation status of cells treated in the presence or absence of DAC for 72 hr was analyzed by methylation‐specific PCR (MSP) according to previously published studies [Okada et al, ; Saito et al, ]. Genomic DNA was isolated using an All Prep DNA/RNA Mini Kit (Qiagen, Hilden, Germany).…”

“…EBV‐associated gastric cancer (EBVaGC) is reported to display extreme DNA hypermethylation, recurrent PIK3CA mutation and PD‐L1/2 overexpression. Researchers have reported that promoter hypermethylation and down‐regulation of various tumor suppressor genes are frequently observed in EBVaGC [Chang et al, ; Kusano et al, ; Kaneda et al, ; Okada et al, ; Saito et al, ]. Thus, treatment with a DNA demethylating agent can be applied to EBVaGC.…”

Genome-Wide DNA Methylation as an Epigenetic Consequence of Epstein-Barr Virus Infection of Immortalized Keratinocytes

“…To investigate epigenetic marks that result in the NOK cell line following EBV infection, we chose to map genome-wide alterations in DNA methylation. We focused on CpG methylation because the distribution of CpG methylation is altered in various EBV-associated malignancies (9,(15)(16)(17)(18)(19)(20)(21). EBV immortalization of B cells has been shown to be associated with large-scale hypomethylation that affected twothirds of the B cell genome and led to promoter hypomethylation of a number of proliferative genes, consistent with the conversion of resting B cells to proliferating blasts (26,27).…”

“…EBV immortalization of B cells has been shown to be associated with large-scale hypomethylation that affected twothirds of the B cell genome and led to promoter hypomethylation of a number of proliferative genes, consistent with the conversion of resting B cells to proliferating blasts (26,27). In contrast, EBVassociated gastric and nasopharyngeal carcinomas display hypermethylation at a number of tumor suppressor gene promoters (17)(18)(19)(20). Since EBV infection has contrasting DNA methylation effects depending on the cellular background, we examined the impact of EBV infection on the cellular methylome of the various NOK cell lines that possibly recapitulated the DNA methylation alterations seen in vivo.…”

“…EBV-positive nasopharyngeal and gastric carcinomas exhibit a high frequency of CpG island (CGI) hypermethylation (CpG island methylator phenotype [CIMP]) at various tumor suppressor genes (9,(15)(16)(17)(18)(19)(20)(21). Furthermore, expression of LMP1 and LMP2A viral oncoproteins has been shown through induction of the host DNMTs to result in hypermethylation and silencing of E-cadherin and PTEN tumor suppressor promoter regions, respectively (9,10,22).…”