S100A8 and gastric neoplasm: Expression of the H. pylori virulence factor In the Drosophila gut model, CagA stimulates abnormal growth of epithelial cells, a characteristic of gastric cancer in people with H. pylori infection.CagA expression results in dysbiosis of the gut microbial population. The altered microbiota caused by CagA expression leads to increased cell proliferation, indicating that dysbiosis may worsen stomach cancer development in H. pylori infection.