Abstract A34: EGF receptor-activated Notch signaling contributes to pathogenesis of premalignant gastric lesions

Abstract

Abstract Ménétrier's disease is a rare acquired protein-losing premalignant hypertrophic gastropathy characterized by giant gastric rugal folds, decreased acid secretion, increased gastric mucus production, and hypoalbuminemia. Microscopically, it is characterized by massive foveolar hyperplasia, oxyntic gland atrophy, and repatterning of cell specification. Spasmolytic polypeptide-expressing metaplasia (SPEM) is a more widely prevalent premalignant gastric lesion, and it is associated with chronic inflammatory conditions such as Helicobacter pylori infection. SPEM is microscopically similar to Ménétrier's disease except for absence of massive foveolar hyperplasia. We previously reported transgenic mice overexpressing the EGF receptor (EGFR) ligand, TGF-α, phenocopy Ménétrier's disease, that TGF-α is overexpressed in the stomach of Ménétrier's disease patients, and that the EGFR-neutralizing monoclonal antibody (mAb), cetuximab, is the first effective medical therapy for Ménétrier's disease. In a proteomic analysis of gastric tissue of Ménétrier's disease patients, we observed decreased levels of the Notch ligand, Jagged1, after cetuximab treatment. The aim of this study was to examine whether Notch signaling is a downstream target of EGFR signaling and whether it contributes to the pathogenesis of Ménétrier's disease and/ or SPEM. TGF-α transgenic mice (MT-TgfaTg) were used as a Ménétrier's disease mouse model. High-dose tamoxifen injection (5 mg intraperitoneal tamoxifen injection per 20 g body weight for 3 days) was used as a SPEM mouse model. Egfr protein reporter mouse line (EgfrEmgfp/Emgfp) was used to investigate the distribution of endogenous Egfr. Chief cell-specific reporter mouse line (Mist1CreERT2/+; Rosa26mTmg/+) was crossed with MT-TgfaTg for chief cell lineage tracing. We tested whether Notch signaling is activated in the stomach of Ménétrier's disease and SPEM mouse models by Hes-1 immunofluorescent staining. Then we tested whether Notch activation is reduced by MM-151, a cocktail of EGFR mAbs that blocks mouse EGFR, and/ or dibenzazepine (DBZ), a γ-secretase inhibitor in the gastric mucosa of MT-TgfaTg mice. We also examined the level of foveolar hyperplasia and proliferation, and the number of parietal and chief cells in the MT-TgfaTg mice using markers: UEA1 (foveolar pit cell), Ki-67 (proliferation), H+/K+ ATPase (parietal cell), GSII (neck cell), and gastric intrinsic factor (chief cell). Expression levels and distribution of endogenous Egfr protein were increased in the gastric mucosa of both Ménétrier's disease and SPEM mouse models. Nuclear Hes-1 expression was upregulated in the pit, isthmus, and neck compartments in the stomach of both mouse models compared to wild-type mice. Lineage tracing of chief cells in MT-TgfaTg mice showed that they were also positive for neck cell marker, GSII, which is a characteristic of SPEM. Number of nuclear Hes-1 positive cells was decreased by MM-151 and/ or DBZ treatment in MT-TgfaTg mice. Also, MM-151 and/ or DBZ treatment led to decreased foveolar hyperplasia and proliferation, and increased numbers of parietal and chief cells in the gastric mucosa of MT-TgfaTg mice. This study shows that the gastric mucosa of MT-TgfaTg mice also has a characteristic of SPEM for the first time. Both Ménétrier's disease and SPEM mouse models show increased EGFR and Notch signaling in the stomach. It was also shown that the activation of EGFR signaling is sufficient and necessary for the activation of Notch signaling in MT-TgfaTg mice. This study suggests that Notch signaling activated by EGFR signaling contributes, at least in part, to the pathogenesis of Ménétrier's disease and SPEM. Moreover, these findings suggest that blockade of Notch signaling may be a novel therapeutic strategy for Ménétrier's disease and SPEM. Citation Format: Won Jae Huh, Robert J. Coffey. EGF receptor-activated Notch signaling contributes to pathogenesis of premalignant gastric lesions [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr A34.