Helicobacter pylori Induces Gastric Epithelial Cell Invasion in a c-Met and Type IV Secretion System-dependent Manner

Abstract

Helicobacter pylori interacts with gastric epithelial cells, activating signaling pathways important for carcinogenesis. In this study we examined the role of H. pylori on cell invasion and the molecular mechanisms underlying this process. The relevance of H. pylori cag pathogenicity island-encoded type IV secretion system (T4SS), CagA, and VacA for cell invasion was also investigated. We found that H. pylori induces AGS cell invasion in collagen type I and in Matrigel invasion assays. H. pyloriinduced cell invasion requires the direct contact between bacteria and cancer cells. H. pylori-mediated cell invasion was dependent on the activation of the c-Met receptor and on increased MMP-2 and MMP-9 activity. The abrogation of the c-Met receptor using the specific NK4 inhibitor or the silencing of c-Met expression with small interference RNA suppressed both cell invasion and MMP activity. Studies with different H. pylori strains revealed that cell invasion, c-Met tyrosine phosphorylation, and increased MMP-2 and MMP-9 activity were all dependent on the presence of a functional bacterial T4SS, but not on VacA cytotoxicity. Our findings demonstrate that H. pylori strains with a functional T4SS stimulate gastric epithelial cell invasion through a c-Met-dependent signaling pathway that comprises an increase in MMP-2 and MMP-9 activity.Helicobacter pylori is a bacterial pathogen that colonizes the gastric mucosa of more than half of the human population (1). In most individuals the infection induces chronic superficial gastritis, a condition that will remain throughout life. However, in some individuals, more severe outcomes of the infection may develop, such as peptic ulcer disease, mucosa-associated lymphoid tissue lymphoma, and gastric carcinoma (2). This diversity of clinical outcomes associated with H. pylori infection is probably a result of the interactions among host, environmental, and bacterial virulence factors (2, 3). Numerous studies have shown that H. pylori is able to interact with gastric epithelial cells, activating signaling pathways, modifying host cellular functions, and inducing cell phenotypes important for carcinogenesis (4 -7). One of the less explored cell phenotypes induced by H. pylori is cellular invasion. Although little is known about the mechanisms involved in this process, H. pylori was shown to activate tyrosine kinase receptors frequently involved in invasion-related pathways, such as the epidermal growth factor receptor (EGFR), 4 Her2/Neu (ErbB-2), and c-Met (8 -10).Another group of molecules associated with cancer cell invasion and influenced by H. pylori are matrix metalloproteinases (MMPs) (11). MMP expression and activity are frequently enhanced in tumors as compared with normal tissue (11,12). It has been shown that H. pylori up-regulates the expression and activity of several MMPs, both in gastric epithelial cell lines and in the gastric mucosa (13-15).H. pylori virulence factors differentially interfere with signaling pathways in gastric epithelial cells (16). One well establishe...

The β1 Integrin Activates JNK Independent of CagA, and JNK Activation Is Required for Helicobacter pylori CagA+-induced Motility of Gastric Cancer Cells

“…Recent studies also showed that H. pylori induced cell invasion through a combination of CagA-dependent and CagAindependent (but TFSS-dependent) signaling (22,32).…”

“…The critical role of CagA in cancer cell motility was emphasized by Higashi et al (11) who showed that CagA transfection of AGS cells was sufficient to induce the motile phenotype. These data suggest that CagA stimulates all signaling necessary to induce cell motility, although this hypothesis is not universally accepted (22).…”

“…Additionally, H. pylori stimulates gastric cancer cell invasion through in vitro basement membranes, suggesting a role for H. pylori in cancer progression to metas-tasis (22)(23)(24). The mechanism of H. pylori-induced cell motility and invasion are unclear, although recent studies show that CagA associates with key regulators of cell adhesion, motility, and invasion, including c-Met, Grb2, SHP-2 phosphatase, and ZO-1 (11,12,14,22,25). The critical role of CagA in cancer cell motility was emphasized by Higashi et al (11) who showed that CagA transfection of AGS cells was sufficient to induce the motile phenotype.…”

Helicobacter pylori – Not Only a Gastric Pathogene?

“…H. pylori strains producing CagA are associated with increased risk of severe gastric pathologies compared with CagA negative strains (Portal-Celhay and Perez-Perez 2006). Injection of bacterial proteins into the gastric cells by a type IV bacterial secretion system (a multi-molecular complex that mediates the translocation of bacterial factors into the host cell) has been described (Segal et al 1999;Oliveira et al 2006). In this way, CagA protein can get inside the host cells and stimulate cell signalling through interaction with several host proteins.…”

A Double-Edged Sword: Roles of Helicobacter Pylori in Gastric Carcinoma

“…Being the receptor of HGF, cMet is activated by H. pylori, involved in malignant transformation of gastric mucosa and invasive growth of tumor cells, and strongly implicated in late-stage cancer progression and worse prognosis (Zhuang X et al, 2001;Churin et al, 2003;Snider & Cardelli, 2009). In addition, H. pylori-mediated GEC invasion depends on c-Met activation, besides on increased activities of MMP-2 and MMP-9 (Oliveira et al, 2006). The c-Met interacts with CagA and suppresses the phosphatidylinositol 3-kinase/Akt pathway, which then leads to -catenin activation and NF-κB signalling (Suzuki et al, 2009).…”