H. pylori-encoded CagA disrupts tight junctions and induces invasiveness of AGS gastric carcinoma cells via Cdx2-dependent targeting of Claudin-2

Abstract

Helicobacter pylori encoded CagA is presently the only known virulence factor that is injected into gastric epithelial cells where it destroys apical junctional complexes and induces dedifferentiation of gastric epithelial cells, leading to H. pylori-related gastric carcinogensis. However, little is known about the molecular mechanisms by which CagA mediates these changes. Caudal-related homeobox 2 (Cdx2) is an intestine-specific transcription factor highly expressed in multistage tissues of dysplasia and cancer. One specific target of Cdx2, Claudin-2, is involved in the regulation of tight junction (TJ) permeability. In this study, our findings showed that the activity of Cdx2 binding to Cdx binding sites of CdxA (GTTTATG) and CdxB (TTTTAGG) of probes corresponding to claudin-2 flanking region increased in AGS cells, infected with CagA positive wild-type strain of H. pylori, compared to CagA negative isogenic mutant-type strain. Moreover, Cdx2 upregulated claudin-2 expression at transcriptional level and translational level. In the meantime, we found that TJs of AGS cells, infected with CagA positive wild-type strain of H. pylori, compared to CagA negative isogenic mutant-type strain, were more severely destroyed, leading to wider cell gap, interference of contact, scattering and highly elevated migration of cells. Herein, this study is firstly demonstrated that H. pylori-encoded CagA disrupts TJs and induces invasiveness of AGS gastric carcinoma cells via Cdx2-dependent targeting of Claudin-2. This provides a new mechanism whereby CagA induced dedifferentiation of AGS cells, leading to malignant behavior of biology.

Keywords: AJC; CagA; Cdx2; Claudin-2; DS; EDTA; EMSA; FCS; HNF; Helicobacter pylori; IBD; Invasiveness; PI; Signal transduction; TJ; TJ zone; TJz; Tight junction; ZO-1; apical junctional complex; cytotoxin-associated gene A; desmosome; electrophoretic mobility shift assay; ethylenediaminetetraacetic acid disodium salt; fetal calf serum; hepatocyte nuclear factor; inflammatory bowel disease; propidium iodide; tight junction; zonulae occludentes-1.