Risk Prediction of Gastric Cancer by Analysis of Aberrant DNA Methylation in Non-Neoplastic Gastric Epithelium

Abstract

Background: Aberrant DNA methylation is one of the major events in carcinogenesis. Promoter DNA methylation is also present in various non-neoplastic tissues including gastric epithelium as age-related phenomenon, suggesting that it occurs early in the process of tumorigenesis. Aim: We aimed to clarify the relationship of aberrant DNA methylation in non-neoplastic gastric epithelia with the risk of gastric cancer, Helicobactor pylori infection, and the degree of H. pylori-induced gastritis. Methods: 89 patients enrolled in this study. The status of aberrant DNA methylation was compared in two groups of patients: 43 cases with gastric cancer (mean age 65.9 years [29–91], F:M = 0.30, intestinal type [n = 25], diffuse type [n = 18]) and 46 age- and sex-matched patients without gastric cancer (peptic ulcer diseases [n = 11], gastritis [n = 35]) as a control group. Genomic DNA was extracted directly from non-neoplastic epithelia of antral biopsies obtained by endoscopy. The promoter methylation status of the p14 and p21 genes was determined by methylation-specific-polymerase chain reaction (MSP). The promoter methylation status of the p16 gene was quantified by digital densitographic analysis following MSP. The degree of gastritis in the antrum was assessed according to the updated Sydney system. The PG I/II ratio was calculated based on the data of serum PG I and PG II levels measured by radioimmunoassay. Results: In all 89 subjects, CpG island methylation was found in 25.8% for p14, 52.8% for p16, 1.1% for p21. Among non-cancer patients, the methylation frequency of the p14 gene was significantly higher in H. pylori-positive than in H. pylori-negative patients (38.5 vs. 10.0%, p = 0.03). The mean (± SD) methylation levels of the p16 gene in non-neoplastic gastric epithelium was significantly higher in gastric cancer cases both in all patients and in H. pylori-positive patients (0.45 ± 0.31 vs. 0.20 ± 0.17; p = 0.019, 0.45 ± 0.31 vs. 0.20 ± 0.17; p = 0.016, respectively). The methylation level of the p16 gene was also associated with the presence of intestinal-type gastric cancer (p = 0.017). The methylation level of the p16 gene was significantly higher in patients with intestinal metaplasia (IM) than those without (p = 0.04). Furthermore, the methylation level of the p16 gene was correlated with lower PG l/ll ratio (p = 0.04). The methylation of the p21gene was found in only 1 patient with gastric cancer. Conclusions: Our data suggest that promoter of the p14 gene may be one of the specific regions whose methylation is closely associated with H. pylori infection. Methylation levels of the p16 gene seem to be accumulated in the progression of gastric mucosal atrophy and IM, and thus may be associated with the presence of gastric cancer especially for intestinal-type histopathology.

Morphologic Characterization of Residual DNA Methylation in the Gastric Mucosa after Helicobacter Pylori Eradication

“…The multivariate analysis showed that atrophic type or intestinal metaplasia was the strong independent risk for DNA methylation after H. pylori eradication. Although DNA hypermethylation might be a risk of gastric cancer regardless of H. pylori infection status [6,[19][20][21], in our study, the most important factor of DNA hypermethylation was magnifying NBI and histologic features. This indicates that the methylation change is closely linked to the magnifying NBI and histologic features within the focal points.…”

Effect of polymorphisms of IL-17A, -17F and MIF genes on CpG island hyper-methylation (CIHM) in the human gastric mucosa

“…One of the most important factors causing CIHM in the stomach is H. pylori infection (7,11,12), which induces chronic inflammation, causing oxidative stress to the gastric epithelium (16,17). Indeed, the methylation of certain genes in non-neoplastic gastric mucosa correlate with H. pylori related histological or serological severity of gastritis (12) and gastric cancer occurrence (13)(14)(15). Thus, this epigenetic change is thought to be an early step in gastric carcinogenesis.…”

“…To detect CIHM, we chose four candidate promoter CpG islands, which were thought to be most susceptible for methylation in the stomach (7,(11)(12)(13)(14)(15): p14, p16, DAP-kinase and CDH1. For the examination of DNA methylation, genomic DNA was treated with sodium bisulfite using BislFast DNA modification kit for methylated DNA detection (Toyobo, Co., Ltd., Osaka, Japan).…”

“…Methylation of DAP-kinase has been reported in many cancers (8) including gastric cancer (9,10). It has also been reported that CIHM of those 4 genes are frequently occurred in non-cancerous gastric mucosa in relation to H. pylori infection (7,11,12), histological or serological severity of gastritis (12) and gastric cancer occurrence (13)(14)(15). Therefore, they may be susceptible candidate genes for CIHM in the stomach.…”

“…In this study, we investigated the prevalence of CIHM of 4 candidate genes: p14, p16, CDH1 and DAP-kinase, they have been thought to be most susceptible for methylation in the stomach (7,(11)(12)(13)(14)(15) among non-cancerous gastric mucosa and its relation to IL-17A, IL-17F and MIF polymorphisms.…”