Expression of claudin-4 molecule in canine exocrine pancreatic acinar cell carcinomas

Claudins, integral membrane proteins are components of the tight junction structures between epithelial and endothelial cells. These transmembrane proteins create a primary barrier to prevent paracellular transport of solutes, and also restrict the lateral diffusion of membrane lipids and proteins to maintain the cellular polarity. The aim of the present study was to characterise the expression pattern of claudin-4 tight junction molecule in canine normal pancreatic tissues and in the well-differentiated and poorly-differentiated pancreatic acinar cell carcinomas in canines.

The necropsy samples included canine intact pancreatic tissues, and canine well-differentiated and poorly-differentiated pancreatic acinar cell carcinomas samples. Claudin-4 was detected as an intense lateral membrane labelling of acinar cells in all intact pancreatic tissues. The intact epithelial cells of the different ducts were negative for the claudin-4 molecule. All primary and secondary canine well-differentiated exocrine pancreatic acinar cell carcinoma tissues showed intense apical lateral positivity for the claudin-4 molecule. All primary and secondary poorly-differentiated pancreatic acinar cell carcinoma tissues showed diffusely the loss of claudin-4 expression.

Consequently, we hypothesize that the loss of expression of claudin-4 plays a role in the progression of canine pancreatic acinar cell carcinoma and may lead to cellular detachment, disorientation and invasion of these pancreatic cancers. Furthermore, claudin-4 can be used as an immunohistochemical marker to distinguish canine well-differentiated and undifferentiated exocrine pancreatic acinar cell carcinomas.