Helicobacter pylori induces promoter methylation of E‐cadherin via interleukin‐1β activation of nitric oxide production in gastric cancer cells

Abstract

BACKGROUND:Helicobacter pylori infection causes gastric mucosal inflammatory responses, resulting in up-regulation of interleukin1b (IL-1b) and overproduction of mutagenic nitric oxide (NO). The authors previously demonstrated that IL-1b plays an important role in H. pylori-induced E-cadherin (E-cad) methylation. Here, they extend the study to investigate the downstream effect of IL-1b on H. pylori-induced gastric inflammation and aberrant DNA methylation. METHODS: Human gastric cancer cell lines (MKN7, MKN74, and TMK-1) with and without pretreatment of IL-1 receptor antagonist (IL-1ra) were treated with IL-1b or infected with H. pylori. Promoter methylation status of E-cad was examined by methylation-specific polymerase chain reaction (PCR). Expression of E-cad, inducible nitric oxide synthase (iNOS), and nuclear factor jB (NFjB) was assessed by quantitative reverse transcriptase PCR, Western blotting, or immunofluorescence. NO production and total DNA methyltransferase (DNMT) activity were assayed fluorometrically. RESULTS: Both IL-1b treatment and H. pylori infection-induced E-cad methylation led to a decrease in E-cad expression at both mRNA and protein levels. Total DNMT enzymatic activity was significantly elevated in treated cells, accounting for the observed E-cad methylation induction. Increased expression of NFjB was accompanied by up-regulation of iNOS and production of NO in treated cells. Reversal of all these phenomena in cells pretreated with IL-1ra suggested H. pylori-induced E-cad methylation via IL-1b stimulation of the NFjB transcriptional system, leading to activation of DNMT activity by NO production. CONCLUSIONS: These findings reveal a previously unknown effect of IL-1b and NO on H. pylori-induced aberrant DNA methylation. This possible pathway indicates the role of NO in epigenetic modification that links inflammation to carcinogenesis. Cancer 2012;118:4969-80.

Interleukin-1β increases the risk of gastric cancer through induction of aberrant DNA methylation in a mouse model

“…The results of the present study additionally support the mechanism of H. pylori-induced epigenetic changes and gastric carcinogenesis via IL-1β activation of iNOS and NO production, as proposed in our previous studies (5,17,18). Excessive NO production causes tissue damage with subsequent cellular genome injuries (10).…”

“…This methylation induction effect could be reversed following the administration of IL-1β antagonist, interleukin-1 receptor antagonist (5,17,18). These findings suggest the potential mechanistic basis of H. pylori in induction of epigenetic changes for gastric diseases.…”

“…It has been demonstrated that IL-1β may induce DNA methylation in vitro (16)(17)(18). This methylation-dependent gene silencing mechanism is via IL-1β activation of NO production (16,18).…”

“…This methylation-dependent gene silencing mechanism is via IL-1β activation of NO production (16,18). Thus, the present study used mice in which the interleukin 1 receptor type 1 (IL-1R1) was deleted in order to characterize the specific role of IL-1β in H. pylori-induced DNA methylation.…”

Epigenetic Silencing of miR-490-3p Reactivates the Chromatin Remodeler SMARCD1 to PromoteHelicobacter pylori–Induced Gastric Carcinogenesis

“…Similar to our study, Ando and colleagues (21) reported that miR-124a is silenced by aberrant DNA methylation in gastric cancer as well as H. pylori-infected, noncancerous gastric epithelium, favoring the field cancerization model. The mechanisms by which H. pylori promotes DNA hypermethylation of tumor-suppressor genes in gastric cancer are not entirely clear, but chronic inflammation induced by H. pylori infection, which triggers infiltration of monocytes and production of reactive oxygen and nitrogen species, appears to be involved in methylation induction (22,23). In this regard, it would be intriguing to explore whether such epigenetic dysregulation of miRNAs might contribute to chromatin remodeling in the development of other malignancies that arise in the context of microbially initiated inflammatory states (24).…”