In the mid 1990's, a bacterium, Helicobacter pylori, was linked to gastric cancer, the third leading cancer killer worldwide. H. pylori establishes lifelong infection in the stomach of half the human population. The consequence of this infection ranges from undetected gastritis, to ulcer disease, and gastric cancer. This wide range of disease outcomes remains a mystery of H. pylori pathogenesis. Our lab is interested in the mechanisms by which this bacterium can establish and maintain a chronic infection in the unusual environment of the human stomach and the molecular cross talk between the host and the bacteria during the decades-long infection. The activation of host cell processes, either through direct action of bacterial products or as part of the host's attempt to contain the infection presumably causes the different diseases associated with H. pylori infection. To approach this complex problem, we are using both global and molecular approaches.