It is known that Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway is induced in various biologic reactions related to gastric cancer, including inflammatory process caused by chronic Helicobacter pylori (H. pylori) infection and interaction between gastric epithelium and microenvironmental stromal cells to promote migration or invasion of cancer cells. This evidence concerns the gene STAT3 and cancer.