Gastrokine 1 (GKN1), a stomach-speci?c protein also known as 18 kDa antrum mucosa protein (AMP-18) or foveolin, belongs to the gastrokine family of gastric mucus cell-secreted proteins. The human GKN1 gene is localized in a region of chromosome 2p13 of about 6 kb and contains 6 exons. As a secreted protein, GKN1 is specifically expressed in gastric mucosa to protect and maintain the integrity of gastric epithelium. GKN1 is involved in the replenishment of the surface lumen epithelial cell layer, and could play a role in cell proliferation and differentiation. Recent findings showed that GKN1 may act as a functional gastric tumor suppressor and may also modulate apoptotic signals.