CLDN7 and gastric cancer: As is well known, the two claudin proteins, claudin-1 and claudin-7, are integral membrane proteins crucial to formation of tight junctions, maintaining cell-to-cell adhesion and regulating paracellular and transcellular transport of solutes across human epithelia and endothelia, which are differentially expressed in various cancers such as cervical neoplasia [20], renal carcinoma [21] and an intestinal type of gastric cancer [22].