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

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.

Helicobacter pyloriCagA and IL-1βPromote the Epithelial-to-Mesenchymal Transition in a Nontransformed Epithelial Cell Model

“…MCF-10A cells are human mammary epithelial cells that were obtained from the American Type Culture Collection (ATCC CRL-10317, Manassas, VA, USA). MCF-10A three-dimensional (3D) or monolayer (2D) cultures were performed as previously reported by us and Debnath et al [ 47 , 51 ]. For infection assays, MCF-10A cells were seeded at 3000 cells/cm 2 and cultured for 48 hrs to reach 70% subconfluency and then switched to DMEM-F12 without fetal bovine serum (FBS).…”

“…We recently found that CagA induces anoikis resistance through activation of the AKT signaling pathway [ 47 ]. AKT is also an important mediator of EMT through inactivation of glycogen synthase kinase 3 β (GSK3 β ), a critical negative regulator of β -catenin.…”

Loss of p53 expression in the gastric epithelial cells of Helicobacter pylori infected Jordanian patients

“…As in many other infections, H. pylori triggers the downregulation of p53 protein by which the bacterium blocks apoptosis one of the main defensive mechanism in infected cells (23,24). This protective function of p53 is also impaired in many forms of cancer (25,26).…”

“…This protective function of p53 is also impaired in many forms of cancer (25,26). (8,23,24), by activating pathways that are already present in cells (14). Yet, this has possibly lethal consequences for the host as the damage of p53, the central "guardian of the genome", upsurges the risk of mutant cells to survive and develop into cancer cells (25,26) Numerous bacterial contagions are now supposed to be a factor in cancer development but their association is not so decisively proven as for H. pylori, which can induce chronic gastritis, gastric ulcer and finally lead to cancer development ( 7 ) .…”

“…With the recognition of H. pylori's cagPAI type 4 secretion system (T4SS) as a significant virulence factor, our study did not show whether Cag A is expressed in patients infected with H. pylori and this needs further investigation. CagA is an inflammatory and potentially transforming determinant of H. pylori(23). The translocation of CagA effector protein into host cells and its phosphorylation by Src kinase and uncovered crucial signaling routes induced by CagA, including its function in downregulating innate epithelial defense factors, are responsible for the vast pro-inflammatory activity of the T4SS(27).…”