Aquaporin-1 (AQP-1, gene symbol AQP1) has been proposed as a selective marker for differentiated cholangiocytes and as a useful biomarker to immunohistochemically differentiate between CCA and HCC and metastatic colorectal carcinomas [21], while high AQP-5 (gene symbol AQP5) expression was associated with better prognosis and drug sensitivity in biliary tract carcinoma [22]. Here, AQP1 is linked to cholangiocarcinoma.