Gastrokine 1, also known as GKN1 and CA11, is a 185aa containing secreted protein belonging to the gastrokine family with a BRICHOS domain and an asn-rich region. GKN1 (also known as an antioncogene) is reported to be down-regulated in human gastric cancer tissue as compared to normal gastric mucosa. Differential display of normal and cancerous gastric tissue suggested that this protein is predominantly expressed in stomach and the expression is down-regulated to considerable frequency in cancer tissue or gastric cancer cell lines examined. This extra cellular protein is co-secreted with mucins and is a signaling growth factor with mitogenic activity and may be involved in maintaining the integrity of the gastric mucosal epithelium.