CLDN1 and familial pancreatic carcinoma: Mechanistically, in pancreatic cancer, zinc transporter protein 4 (ZIP4) was highly expressed and inhibited ZO-1 and claudin-1 expressions by regulating a mesenchymal cell marker zinc finger E-box binding homeobox 1 (ZEB1), which bound directly to the promoters of ZO-1 and claudin-1 and repressed their transcriptions.