Hanover, NH - Research carried out in two distinct communities in Colombia illustrates how coevolution between humans and bacteria can affect a person's risk of disease. Working with colleagues in Columbia and the U.S., Scott Williams, PhD, a professor of genetics at the Geisel School of Medicine at Dartmouth, and his graduate student Nuri Kodaman discovered that the risk of developing gastric cancer depends heavily on both the ancestry of the person and the ancestry of Helicobacter pylori with which that person is infected. About half of the world's population is infected with H. pylori. The microbe usually only causes minor gastric inflammation, but it is also the primary cause of gastric cancer, which is the second-leading cause of death by cancer worldwide.
Williams' research team studied 233 people from two populations in Colombia, one located in the mountain village of Tuquerres and the other in the coastal village of Tumaco. Rates of H. pylori infection in the two communities are similar (about 90%), but the rate of gastric cancer is about 25 times higher in the mountain community. The researchers classified the ancestry of the people in both villages and of the H. pylori in each area. In the coastal village, the human population was primarily of African descent. The dominant component of the H. pylori also came from Africa. In the mountain village, the people were largely Amerindian and had very little African ancestry, and the H. pylori was predominantly derived from Europe.
The researchers examined the connections between human ancestry, the strains of H. pylori, and the severity of gastric disease and made several important findings: First, among both populations, people of European or Amerindian descent were at greater risk of developing more severe lesions than were people of African descent. Second, in the mountain community, where most people were of Amerindian or
|Contact: Derik Hertel|
The Geisel School of Medicine at Dartmouth