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Induction of aberrant DNA methylation by H.pylori infection
It has long been known that inflammation is associated with cancer development. For instance, individuals with gastritis due to H. pylori infection tend to develop gastric cancers. We found that significantly larger fractions of DNA molecules were methylated in gastric mucosae of H. pylori-infected individuals than in those of non-infected individuals (Maekita et al., 2006 , Ando et al., 2009 ), and that patients with multiple gastric cancers have higher methylation levels in gastric mucosae than patients with a single gastric cancer (Nakajima et al., 2006 ).
Furthermore, by using an animal model, we clarified that inflammation due to H. pylori infection is important to induce aberrant DNA methylation (Niwa et al., 2010 , Hur et al., 2011 , Katsurano et al., 2012 ). The findings in human and an animal model indicate that inflammation due to H. pylori infection induces aberrant DNA methylation in gastric epithelial cells and produces a high-risk status for cancer development (field for cancerization) (Fig. ). We are currently clarifying what molecules in inflammation are responsible for induction of aberrant DNA methylation using the animal model.
Fig. Aberrant DNA methylation induced by H. pylori infection and development of gastric cancer