Phylogenetic origin of Helicobacter pylori pathogenicity island and risk of stomach cancer and high-grade premalignant gastric lesions.

Abstract

Infection by Helicobacter pylori (Hp) has been causally linked to risk of gastric cancer (GC). The coevolution of Hp and humans shaped the risk of GC as our species left Africa and migrated to the other continents. Latin America (LatAm) is a high GC incidence region where Hp evolved uniquely in the 500 years since European colonization. Differential virulence of the Hp cagA -pathogenicity island (cagPAI) by ancestral origin has been reported. We hypothesized that Hp phylogenetic origin might play a role in determining GC risk in LatAm. We used genotypes of 50 Hp genetic variants mapping to the Hp cagPAI, studied in 1220 subjects from Venezuela, Colombia, Mexico and Paraguay, who were infected with cagA-positive Hp, including 150 GC, 177 high-grade premalignant lesions (HGPMLs) and 893 low-grade premalignant lesions. We estimated the phylogenetic origin of Hp cagPAI in all study subjects by use of the STRUCTURE software and principal component analysis (PCA) and tested whether the estimated African ancestry percentage was associated with the risk of GC or HGPML. African ancestral component estimates by STRUCTURE and PCA were highly correlated. STRUCTURE-based African origin estimate was not significantly associated with the risk of HGPML, but it was inversely associated with GC risk: the OR associated with the continuous values of African component was 0.09 (95% CI, 0.01-0.85; P = 0.035). Similar trends were observed for GC with PCA-based estimates, but the association was not statistically significant. These results suggest that Hp ancestral origin may play a role in gastric carcinogenesis.