Claudin-1, -2, -3, -4, -7, -8, and -10 protein expression in biliary tract cancers.

Biliary tract cancers are relatively common malignant gastrointestinal tumors in the elderly. Claudins are integral components of tight junctions that play important roles in maintaining epithelial cell polarity, controlling paracellular diffusion, and regulating cell growth and differentiation. The expression profile of claudins has been extensively characterized, but few reports exist on their expression in the normal and neoplastic biliary tract. Our aim was therefore to study claudins by IHC reactions in normal and neoplastic biliary tract samples. We detected that claudin expressions differ in the normal sample groups: the normal gallbladder strongly expressed claudin-2, -3, -4, and -10, but only weak reactions were seen in normal intrahepatic bile ducts. Although each cancer type expressed several claudins with various intensities, only claudin-4 presented especially strong immunoreactions in extrahepatic bile duct cancers and gallbladder carcinomas, whereas claudin-1 and -10 presented in intrahepatic bile duct cancers. Comparing the normal and carcinoma groups, the most significant decrease was detected in the expression of claudin-10. In conclusion, the expression pattern of claudins is different in the various parts of the normal and neoplastic biliary tract; moreover, an unequivocal decrease was detected in the carcinomas compared with their corresponding normal samples. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.