STAT3 and cancer: When H. pylori enters the stomach and adheres to GECs, a major bacterial virulence factor cagA is injected into the host cells by the type IV secretion system and interferes with several signaling transduction pathways, such as Wnt–β-catenin, PI3K-AKT, and JAK-STAT3 pathways (25), and plays an important role in chronic gastritis and cancer development.