Altered patterns of DNA methylation associated with Helicobacter pylori (HP) infection of gastric epithelial cells are thought to contribute to gastric cancer risk. However, it is unclear whether this increased risk reflects an infection-associated inflammatory response or the infection itself. In this study, we sought to clarify mechanisms in a gerbil model of gastric cancer where we showed that HP infection is causally involved in induction of aberrant DNA methylation. By genome-wide screening, CpG islands that were aberrantly methylated in gerbil gastric cancer cell lines were isolated, and 10 islands were shown to be specifically methylated only in gastric mucosae infected with HP. By temporal analysis, methylation levels in gastric epithelial cells started to increase at 5 to 10 weeks after infection and reached high levels by 50 weeks. When HP was eradicated, methylation levels markedly decreased 10 and 20 weeks later, but they remained higher than those in gerbils that were not infected by HP. Expression levels of several inflammation-related genes (CXCL2, IL-1β, NOS2, and TNF-α) paralleled the temporal changes of methylation levels. Significantly suppressing inflammation with the immunosuppressive drug cyclosporin A did not affect colonization by HP but blocked the induction of altered DNA methylation. Our findings argue that DNA methylation alterations that occur in gastric mucosae after HP infection are composed of transient components and permanent components, and that it is the infection-associated inflammatory response, rather than HP itself, which is responsible for inducing the altered DNA methylation.

Down-regulation of Sox2, besides ectopic expression of Cdx genes, may be important factors for the development of IM.

Spasmolytic polypeptide (TFF2)-expressing metaplasia (SPEM) is observed in mucosa adjacent to human gastric cancer and in fundic glands showing oxyntic atrophy in Helicobacter felis-infected mice. Mongolian gerbils infected with Helicobacter pylori (Hp) develop goblet cell intestinal metaplasia and adenocarcinoma, but the presence of SPEM has not been studied in gerbils. We therefore have sought to examine the development of metaplastic mucosal changes in Hp-infected Mongolian gerbils. Mongolian gerbils were assigned to either uninfected controls or infected with Hp at 17 weeks of age. The animals were killed at 17, 20, 26, 31, 41 and 56 weeks of age. Stomach sections were stained using antibodies for TFF2, intrinsic factor, H/K-ATPase, BrdU and MUC2. Dual immunofluorescence staining for TFF2 with intrinsic factor and for TFF2 with MUC2 was performed. In uninfected animals, no SPEM or intestinal metaplasia was observed. Infected gerbils developed SPEM initially in the intermediate zone along the lesser curvature and subsequently spread out towards the greater curvature. In the earlier stages of infection, SPEM glands demonstrated TFF2 and intrinsic factor double staining cells. However, after 35 weeks of infection, the number of double staining SPEM cells decreased. While early in infection SPEM organized in straight glands, in the later stages of infections, SPEM glands became distorted or dilated along with the development of gastritis cystica profunda that was TFF2 positive. Goblet cell intestinal metaplasia developed only late in the infection. Dual staining for TFF2 and MUC2 showed glands containing both SPEM-and MUC2-positive goblet cell intestinal metaplasia. SPEM develops early in Hp infection in Mongolian gerbils, and alterations in gland morphology arise from SPEM glands during the course of gastric infection with goblet cell intestinal metaplasia developing subsequent to SPEM.

elicobacter pylori (Hp) is a major causative factor for gastric disorders and strong epidemiological evidence has been accumulated indicating a significant relationship with active chronic gastritis, peptic ulcers, atrophic gastritis, intestinal metaplasia, and malignant lymphoma or cancer development.