Geographic differences in gastric cancer incidence can be explained by differences between Helicobacter pylori strains

Abstract

Certain populations with high incidences of Helicobacter pylori infection, such as those in East Asian countries, have high incidences of gastric cancer, while other highly infected populations, such as those in Africa and South Asia, do not. The various rates of gastric cancer associated with different geographic areas can be explained, at least in part, by the differences in the genotypes of H. pylori cagA and vacA. Populations expressing a high incidence of gastric cancer are mostly identical with regions where East Asian type CagA is predominant. In contrast, incidence of gastric cancer is low in Africa, South Asia, and Europe, where strains typically possess Western type CagA. Within East Asia, strains from northern parts, where the incidence of gastric cancer is high, predominantly possess the vacA m1 genotype, whereas the m2 genotype is predominant in southern parts where the gastric cancer incidence is low.

Figure 1

A: Distribution of six main H. pylori genotypes before Columbus found the New World: hpEurope (green), hpEastAsia (orange), hpAfrica1 (blue), hpAfrica2 (red), hpAsia2 (gray) and hpNEAfrica (purple). hpEastAsia includes subpopulations hspMaori (Polynesians), hspAmerind (native Americans) and hspEAsia (East Asia). Before Columbus, it is likely that hpAmerind was the major strain in America. B: The present distribution of six main H. pylori genotypes. After Columbus, the H. pylori distribution changed in America and Oceania, following the human migration from Europe and Africa to America and Europe to Oceania. Currently hpAmerind genotypes are very rare even in the native American population. C: The annual incidence of gastric cancer. Case numbers per 100,000 males are presented. The circles coincide with countries in which the H. pylori genotypes have been examined (9, 12). The colors correspond to those in Figs. 1A and B. Interestingly, we can overlap the incidence of gastric cancer with H. pylori genotypes shown in Fig. 1B. For example, the high incidence of gastric cancer in East Asia corresponds to the orange hpEast Asia genotype.