Helicobacter pylori cagA and vacA genotypes increase gastric cancer risk
MedWire News: The Helicobacter pylori cagA and vacA s1/m1 gene variants are associated with increased risk for advanced gastric preneoplastic lesions that are likely to progress, say researchers.
H. pylori is a genetically diverse species of bacteria and the researchers suggest that this diversity could be used to identify patients with gastric neoplastic lesions who need more intensive surveillance.
Both the cagA-positive and vacA s1/m1 genotypes have previously been associated with gastric preneoplastic lesions. In this study, Carlos González (Catalan Institute of Oncology, Barcelona, Spain) and co-workers assessed the association of these H. pylori genotypes with progression of such lesions in a long-term follow-up study.
Overall, 312 patients, aged 48.5 years on average, were enrolled when undergoing upper endoscopy with gastric biopsy during 1988-1994. The patients had diagnoses of normal mucosa, non-atrophic gastritis (NAG), non-metaplastic multifocal atrophic gastritis (MAG), and complete or incomplete intestinal metaplasia, and underwent a second biopsy during 2005-2007. Mean follow-up time was 12.8 years.
The researchers found that 77.9% of the cohort were positive for H. pylori. Of these, 47.7% had the cagA-positive, 40.1% the vacA s1, and 28.8% the vacA m1 variants.
As reported in the American Journal of Gastroenterology, presence of the H. pyloricagA, vacA s1, and vacA m1 variants was associated with a significant 2.28-, 2.90-, and 3.38-fold increased risk for progression of gastric preneoplastic lesions, respectively.
Individuals infected with strains with both the cagA-positive and vacA s1/m1 genotypes had a 4.80-fold increased risk for progression of pre-existing lesions, compared with those with a cagA-negative and vacA s2/m2 genotype.
Carriers of cagA-positive and vacA s1/m1 genotype H. pylori strains had a significantly higher percentage of advanced gastric preneoplastic lesions than carriers of other variants.
For example, 71.4% and 77.1% of complete and incomplete intestinal metaplasia patients, respectively, were cagA positive compared with 0.0%, 41.7%, and 31.8% of normal, NAG, and MAG patients, respectively. Similar results were obtained for the vacA s1/m1 variants.
"Genotypes of H. pylori could be useful for identifying high-risk patients who could be included in a program of more intensive surveillance of gastric preneoplastic lesions," write González et al.
"Further studies in other populations are needed to confirm our findings," they conclude.
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By Helen Albert