Insufficient role of cell proliferation in aberrant DNA methylation induction and involvement of specific types of inflammation

Keun Hur, Tohru Niwa, Takeshi Toyoda, Tetsuya Tsukamoto, Masae Tatematsu, Han Kwang Yang, Toshikazu Ushijima

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Chronic inflammation is deeply involved in induction of aberrant DNA methylation, but it is unclear whether any type of persistent inflammation can induce methylation and how induction of cell proliferation is involved. In this study, Mongolian gerbils were treated with five kinds of inflammation inducers [Helicobacter pylori with cytotoxin-associated gene A (CagA), H.pylori without CagA, Helicobacter felis, 50% ethanol (EtOH) and saturated sodium chloride (NaCl) solution]. Two control groups were treated with a mutagenic carcinogen that induces little inflammation (20 p.p.m. of N-methyl-N-nitrosourea) and without any treatment. After 20 weeks, chronic inflammation with lymphocyte and macrophage infiltration was prominent in the three Helicobacter groups, whereas neutrophil infiltration was mainly observed in the EtOH and NaCl groups. Methylation levels of eight CpG islands significantly increased only in the three Helicobacter groups. By Ki-67 staining, cell proliferation was most strongly induced in the NaCl group, demonstrating that induction of cell proliferation is not sufficient for methylation induction. Among the inflammation-related genes, Il1b, Nos2 and Tnf showed increased expression specifically in the three Helicobacter groups. In human gastric mucosae infected by H.pylori, NOS2 and TNF were also increased. These data showed that inflammation due to infection of the three Helicobacter strains has a strong potential to induce methylation, regardless of their CagA statuses, and increased cell proliferation was not sufficient for methylation induction. It was suggested that specific types of inflammation characterized by expression of specific inflammation-related genes, along with increased cell proliferation, are necessary for methylation induction.

Original languageEnglish
Pages (from-to)35-41
Number of pages7
JournalCarcinogenesis
Volume32
Issue number1
DOIs
Publication statusPublished - 01-12-2011

All Science Journal Classification (ASJC) codes

  • Cancer Research

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