Evidences showing that low claudin-4 expression is linked to poor prognosis of patients with breast [106], esophageal [107], colon [108,109] and pancreatic cancers [110] suggest that claudin-4 expression is likely to play a tumor suppressive role in several cancers, although its role in ovarian cancer remains unclear. This evidence concerns the gene CLDN4 and familial pancreatic carcinoma.