PTPN11 and gastric cancer: IL-6 is well known to play a role as a tumorigenic factor in GC,75–78 and higher serum IL-6 levels are independent predictors of a poor prognosis in patients with GC.79,80 IL-6 binds to the alpha subunit of its specific receptor and to the gp130 homodimer on the cell membrane,81 and it activates two major signaling pathways: SHP-2/ERK and JAK/STAT.82,83 The SHP2/ERK and JAK/STAT signaling pathways are considered to play opposing roles in gastric epithelial cells, and their balance maintains the homeostasis of the gastrointestinal mucosa.