Helicobacter pylori induced transactivation of SRE and AP-1 through the ERK signalling pathway in gastric cancer cells

Gut. 2001 Jul;49(1):18-22. doi: 10.1136/gut.49.1.18.

Abstract

Background and aims: Helicobacter pylori infection induces expression of proinflammatory cytokines such as interleukin (IL)-8 and tumour necrosis factor alpha (TNF-alpha) in gastric mucosa, and their genes have AP-1 binding sites in the promoter region. c-Fos is important for transactivation of AP-1 which has SRE in the promoter region. We conducted this study to confirm H pylori induced transactivation of these binding sites.

Methods: Transactivation of SRE and AP-1 was evaluated in human gastric cancer cells TMK1 and MKN45 by luciferase reporter assay in transient transfection. We compared the effects of coculture with four H pylori strains, a cag pathogenicity island (PAI) positive strain TN2, its isogenic vacA negative (TN2-DeltavacA) or cagE negative (TN2-DeltacagE) mutants, and a cag PAI negative clinical isolate T68. Phosphorylation of ERK1/2, JNK, and c-Jun was measured by immunoblot, induction of IL-8 secretion by ELISA, and the effects of MEK by inhibitor U0126.

Results: Both SRE and AP-1 were transactivated by coculture with TN2. Although TN2-DeltavacA induced comparable transactivation, TN2-DeltacagE and T68 showed decreased transactivation of SRE (65% and 51%) and AP-1 (71% and 54%, respectively, of TN2). Heat killed TN2 or indirect contact using a permeable membrane inhibited transactivation. Levels of phosphorylated ERK1/2, JNK, and c-Jun were increased by coculture with TN2. MEK inhibitor U0126 reduced TN2 induced transactivation of SRE and AP1, as well as secretion of IL-8, by 83%, 87%, and 53%, respectively, of TN2.

Conclusions: Transactivation of SRE and AP-1, through ERK/MAPK and JNK/SAPK cascades, respectively, was found in gastric cancer cells cocultured with H pylori. Direct contact with viable bacteria possessing intact cag PAI is a prerequisite for the onset of intracellular signalling leading to AP-1 transactivation.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Butadienes / pharmacology
  • CpG Islands / physiology
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Inhibitors / pharmacology
  • Enzyme-Linked Immunosorbent Assay
  • Fungal Proteins*
  • GATA Transcription Factors
  • Genes, jun
  • Helicobacter pylori / physiology*
  • Humans
  • Immunoblotting
  • Interleukin-8 / physiology
  • MAP Kinase Signaling System / physiology*
  • Mitogen-Activated Protein Kinase Kinases / drug effects
  • Nitriles / pharmacology
  • Phosphorylation
  • Stomach Neoplasms / pathology
  • Stomach Neoplasms / physiopathology
  • Transcriptional Activation / physiology*
  • Tumor Cells, Cultured

Substances

  • Bacterial Proteins
  • Butadienes
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Fungal Proteins
  • GATA Transcription Factors
  • Interleukin-8
  • Nitriles
  • PicB protein, Helicobacter pylori
  • Sre protein, Neurospora crassa
  • U 0126
  • VacA protein, Helicobacter pylori
  • Mitogen-Activated Protein Kinase Kinases