CHAMPAIGN, lll. — Researchers report that Helicobacter pylori, the only bacterium known to survive in the harsh environment of the human stomach, directly activates an enzyme in host cells that has been associated with several types of cancer, including gastric cancer. Chronic infection with H. pylori is a well-documented risk factor for several forms of gastric cancer, but researchers have not yet determined the mechanisms by which specific bacterial factors contribute to cancer development. Nearly one-half of the world’s population is infected with H. pylori, and gastric cancer is one of the leading causes of cancer-related death. The new study,...