Human–microbe mismatch boosts risk of stomach cancer

Ed Yong in Nature:

WEB_1_14501_42-31108440The Colombian town of Tuquerres, nestled high in the Andes Mountains, has one of the highest rates of stomach cancer in the world: about 150 cases per 100,000 people. Meanwhile in the coastal town of Tumaco, just 200 kilometres away, the equivalent rate is only around 6 in 100,000. The main cause of stomach cancer is Helicobacter pylori, a bacterium that infects half the world’s population. It is usually harmless, but occasionally leads to tumours. H. pylori has been infecting humans since our origins in Africa, and diversified with us as we spread around the world. But in places such as South America, the arrival of European colonists has broken this long history of co-evolution, leaving some people with H. pylori strains that do not share their ancestry.

Now, a team of scientists led by Pelayo Correa and Scott Williams at Vanderbilt University Medical Center in Nashville, Tennessee, has shown that this mismatch can turn a normally benign infection into a potentially carcinogenic one. When analysed together, the genomes of hosts and microbes give a better prediction of the risk of disease than when considered alone, the team found. Their results are published in Proceedings of the National Academy of Sciences1. “A lot of people have H. pylori, but very few have bad outcomes. Is that due to the organism or the host?” says Martin Blaser, a microbiologist at New York University School of Medicine. “This paper provides evidence that the fit is important. It’s a very nice advance.”

More here.