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Gastroenterology. 2011 Aug;141(2):553-64. doi: 10.1053/j.gastro.2011.05.004. Epub 2011 May 17.

β-Catenin and p120 mediate PPARδ-dependent proliferation induced by Helicobacter pylori in human and rodent epithelia.

Author information

1
Division of Gastroenterology, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA.

Abstract

BACKGROUND & AIMS:

Colonization of gastric mucosa by Helicobacter pylori leads to epithelial hyperproliferation, which increases the risk for gastric adenocarcinoma. One H pylori virulence locus associated with cancer risk, cag, encodes a secretion system that transports effectors into host cells and leads to aberrant activation of β-catenin and p120-catenin (p120). Peroxisome proliferator-activated receptor (PPAR)δ is a ligand-activated transcription factor that affects oncogenesis in conjunction with β-catenin. We used a carcinogenic H pylori strain to define the role of microbial virulence constituents and PPARδ in regulating epithelial responses that mediate development of adenocarcinoma.

METHODS:

Gastric epithelial cells or colonies were co-cultured with the H pylori cag(+) strain 7.13 or cagE(-), cagA(-), soluble lytic transglycosylase(-), or cagA(-)/soluble lytic transglycosylase(-) mutants. Levels of PPARδ and cyclin E1 were determined by real-time, reverse-transcription polymerase chain reaction, immunoblot analysis, or immunofluorescence microscopy; proliferation was measured in 3-dimensional culture. PPARδ and Ki67 expression were determined by immunohistochemical analysis of human biopsies and rodent gastric mucosa.

RESULTS:

H pylori induced β-catenin- and p120-dependent expression and activation of PPARδ in gastric epithelial cells, which were mediated by the cag secretion system substrates CagA and peptidoglycan. H pylori stimulated proliferation in vitro, which required PPARδ-mediated activation of cyclin E1; H pylori did not induce expression of cyclin E1 in a genetic model of PPARδ deficiency. PPARδ expression and proliferation in rodent and human gastric tissue was selectively induced by cag(+) strains and PPARδ levels normalized after eradication of H pylori.

CONCLUSIONS:

The H pylori cag secretion system activates β-catenin, p120, and PPARδ, which promote gastric epithelial cell proliferation via activation of cyclin E1. PPARδ might contribute to gastric adenocarcinoma development in humans.

PMID:
21704622
PMCID:
PMC3152603
DOI:
10.1053/j.gastro.2011.05.004
[Indexed for MEDLINE]
Free PMC Article

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