Helicobacter pyloriCagA Suppresses Apoptosis through Activation of AKT in a Nontransformed Epithelial Cell Model of Glandular Acini Formation

Gabriela Vallejo-Flores,Julián Torres-Morales,Margarita Camorlinga-Ponce,María Victoria Legorreta-Haquet,Javier Torres,Isaura Meza,Adriana Karina Chávez-Rueda,Claudia Sandoval-Montes,Ezequiel M Fuentes-Pananá,Haruki Arévalo-Romero

doi:10.1155/2015/761501

Abstract

H. pylori infection is the most important environmental risk to develop gastric cancer, mainly through its virulence factor CagA. In vitro models of CagA function have demonstrated a phosphoprotein activity targeting multiple cellular signaling pathways, while cagA transgenic mice develop carcinomas of the gastrointestinal tract, supporting oncogenic functions. However, it is still not completely clear how CagA alters cellular processes associated with carcinogenic events. In this study, we evaluated the capacity of H. pylori CagA positive and negative strains to alter nontransformed MCF-10A glandular acini formation. We found that CagA positive strains inhibited lumen formation arguing for an evasion of apoptosis activity of central acini cells. In agreement, CagA positive strains induced a cell survival activity that correlated with phosphorylation of AKT and of proapoptotic proteins BIM and BAD. Anoikis is a specific type of apoptosis characterized by AKT and BIM activation and it is the mechanism responsible for lumen formation of MCF-10A acini in vitro and mammary glands in vivo. Anoikis resistance is also a common mechanism of invading tumor cells. Our data support that CagA positive strains signaling function targets the AKT and BIM signaling pathway and this could contribute to its oncogenic activity through anoikis evasion.

Highlights

Helicobacter pylori (H. pylori) colonizes the human gastric epithelium and is considered the most important cause of chronic active gastritis, peptic ulcer, and gastric cancer [1]
Two cytotoxin-associated gene ABioMed Research International (CagA) positive H. pylori strains were used in this study: strain 11637 with a Western-type CagA (EPIYA ABCCC) that was obtained from the American Type Culture Collection (ATCC, Manassas, VA, USA No 43504); and strain NY02-149 with an EastAsian-type CagA (EPIYA ABD) that was kindly donated by Dr Guillermo Perez-Perez from New York University
To determine if MCF-10A cells were permissive to H. pylori infection, infected cells were analyzed by immunofluorescence and Western blot

Summary

Introduction

Helicobacter pylori (H. pylori) colonizes the human gastric epithelium and is considered the most important cause of chronic active gastritis, peptic ulcer, and gastric cancer [1]. H. pylori activation of the phosphoinositide 3-kinase (PI3K) and protein kinase B (PKB/AKT) signaling pathway has been previously documented in transformed gastric epithelial cells (AGS cells), the mechanism by which this happens is not fully understood. Some studies support CagA phosphorylation dependent and independent roles [9,10,11]. Multiple targets downstream of PI3K/AKT have been documented, including mammalian target for rapamycin (mTOR), forkhead box O (FoxO)-1 and -3a ERK mitogen activated kinase, and proapoptotic protein BAD [15,16,17,18,19]. The consequence of H. pylori activation of PI3K/AKT is unclear, with different studies supporting deregulation of apoptosis, proliferation, or cell migration

Methods

Results

Conclusion