S100A8 and gastric cancer: Helicobacter pylori-derived CagA has been shown to induce the expression of spermine oxidase (SMOX), which leads to the production of hydrogen peroxide (H2O2). The increased H2O2 levels may in turn lead to ROS accumulation via mitochondrial membrane depolarization and activation of cysteine-mediated apoptosis. This pathway may contribute to the development of gastric cancer.