Activation of EGFR and ERBB2 by Helicobacter pylori Results in Survival of Gastric Epithelial Cells With DNA Damage

Abstract

BACKGROUND & AIMS The gastric cancer-causing pathogen Helicobacter pylori upregulates spermine oxidase (SMOX) in gastric epithelial cells, causing oxidative stress-induced apoptosis and DNA damage. A subpopulation of SMOXhigh cells are resistant to apoptosis, despite their high levels of DNA damage. Because epidermal growth factor receptor (EGFR) activation can regulate apoptosis, we determined its role in SMOX-mediated effects. METHODS SMOX, apoptosis, and DNA damage were measured in gastric epithelial cells from H pylori-infected Egfrwa5 mice (which have attenuated EGFR activity), Egfr wild-type mice, or in infected cells incubated with EGFR inhibitors or deficient in EGFR. Phosphoproteomic analysis was performed. Two independent tissue microarrays containing each stage of disease, from gastritis to carcinoma, and gastric biopsies from Colombian and Honduran cohorts were analyzed by immunohistochemistry. RESULTS SMOX expression and DNA damage were decreased, and apoptosis increased in H pylori-infected Egfrwa5 mice. H pylori-infected cells with deletion or inhibition of EGFR had reduced levels of SMOX, DNA damage, and DNA damagehigh apoptosislow cells. Phosphoproteomic analysis revealed increased EGFR and ERBB2 signaling. Immunoblot analysis demonstrated the presence of a phosphorylated (p)EGFR–ERBB2 heterodimer and pERBB2; knockdown of ErbB2 facilitated apoptosis of DNA damagehigh apoptosislow cells. SMOX was increased in all stages of gastric disease, peaking in tissues with intestinal metaplasia, whereas pEGFR, pEGFR–ERBB2, and pERBB2 were increased predominantly in tissues demonstrating gastritis or atrophic gastritis. Principal component analysis separated gastritis tissues from patients with cancer vs those without cancer. pEGFR, pEGFR–ERBB2, pERBB2, and SMOX were increased in gastric samples from patients whose disease progressed to intestinal metaplasia or dysplasia, compared with patients whose disease did not progress. CONCLUSIONS In an analysis of gastric tissues from mice and patients, we identified a molecular signature (based on levels of pEGFR, pERBB2, and SMOX) for the initiation of gastric carcinogenesis.

Increased Helicobacter pylori-associated gastric cancer risk in the Andean region of Colombia is mediated by spermine oxidase

“…24,25 Infection also increases the level of spermine oxidase (SMOX), which catabolizes spermine and produces hydrogen peroxide (H 2 O 2 ) and leads to DNA damage in gastric epithelial cells, a key event in the process of gastric carcinogenesis. 26–29 In the present study we demonstrate that H. pylori strains from the high risk region of Nariño, Colombia induce more SMOX and associated DNA damage in vitro and in vivo . We used inhibitors of ODC and SMOX and found that polyamine synthesis and oxidation drive H. pylori -associated gastric carcinogenesis in a gerbil model of gastric cancer.…”

Helicobacter pylori-induced cell death is counteracted by NF-κB-mediated transcription of DARPP-32

“…H. pylori upregulates the expression of EGF-related growth factors, which activate EGFR and other tyrosine kinase receptors, and then stimulate proliferation and survival through PI3K-AKT and mitogen-activated protein kinases (MAPK) pathways. 46 Notably, we have previously shown that DARPP-32 plays an important role in stabilisation of EGFR and activation of AKT in gastric cancer cells. 6 Taken together, the fact that DARPP-32 expression is induced by H. pylori-activated NF-κB strongly suggests that DARPP-32 oncogenic functions may contribute to H. pylori-mediated gastric tumourigenesis.…”

Transcriptional corepressor MTG16 regulates small intestinal crypt proliferation and crypt regeneration after radiation-induced injury

“…Small intestines were harvested 4 h postirradiation and ϳ3-to 4-cm segments of the distal small intestine were excised and further dissected before snap freezing in liquid nitrogen for use in subsequent flow cytometric analysis (8,9). The remaining section of the distal small intestine was Swissrolled, fixed, and submitted to the Vanderbilt TPSR core for processing and sectioning.…”