In vivo expression of Helicobacter pylori virulence genes in patients with gastritis, ulcer, and gastric cancer

Abstract

The best-studied Helicobacter pylori virulence factor associated with development of peptic ulcer disease or gastric cancer (GC) rather than asymptomatic nonatrophic gastritis (NAG) is the cag pathogenicity island (cagPAI), which encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into host epithelial cells. Here we used real-time reverse transcription-PCR (RT-PCR) to measure the in vivo expression of genes on the cagPAI and of other virulence genes in patients with NAG, duodenal ulcer (DU), or GC. In vivo expression of H. pylori virulence genes was greater overall in gastric biopsy specimens of patients with GC than in those of patients with NAG or DU. However, since in vitro expression of cagA was not greater in H. pylori strains from patients with GC than in those from patients with NAG or DU, increased expression in GC in vivo is likely a result of environmental conditions in the gastric mucosa, though it may in turn cause more severe pathology. Increased expression of virulence genes in GC may represent a stress response to elevated pH or other environmental conditions in the stomach of patients with GC, which may be less hospitable to H. pylori colonization than the acidic environment in patients with NAG or DU.

Fig 1

Relative in vivo expression of H. pylori genes on the cagPAI (A) and of other putative virulence genes (B). Bars represent mean (±SD) relative expression in vivo for each gene in patients with NAG (n = 10), DU (n = 10), and GC (n = 11). Expression of cag2 was not measured because it is highly polymorphic and efficient primers could not be determined. NAG, nonatrophic gastritis; DU, duodenal ulcer; GC, gastric cancer.

Fig 2

Scattergram of the ratios of mean relative gene expression in patients with NAG/DU compared to those with NAG/GC. Cardinal numbers represent the cagPAI gene designations. Non-cagPAI genes are designated as follows: v11 = virB11, R = rocF, S = sabA, V = vacA, B = babA, K = katA, and N = napA. Most genes showed higher expression in patients with GC, so they have ratios of <1.0 on the x axis and are located above the diagonal line. No data are shown for cag19 or cag24 because expression was not detected in patients with GC. NAG, nonatrophic gastritis; DU, duodenal ulcer; GC, gastric cancer.

Fig 3

Relative expression of cagA in vivo in patients with NAG, DU, and GC versus that from the same strains determined in vitro. cagA expression was generally greater in vitro than in vivo. NAG, nonatrophic gastritis; DU, duodenal ulcer; GC, gastric cancer.

Fig 4

Relative expression in vitro of cag19 and cag24 in five H. pylori strains recovered from patients with GC. Although no expression was detected for cag19 or cag24 in vivo (Fig. 1A), strains from these patients expressed these genes in vitro.