Galanin System in the Human Bile Duct and Perihilar Cholangiocarcinoma

Background: Perihilar cholangiocarcinoma (pCCA) is characterised by poor outcomes. Early diagnosis is essential for patient survival. The peptide galanin (GAL) and its receptors GAL(1–3) are expressed in various tumours. Detailed characterisation of the GAL system in pCCA is lacking. Our study sought to characterise GAL and GAL(1–3) receptor (GAL(1–3)–R) expression in the healthy human bile duct, in cholestasis and pCCA. Methods: Immunohistochemical staining was performed in healthy controls (n = 5) and in the peritumoural tissues (with and without cholestasis) (n = 20) and tumour tissues of pCCA patients (n = 33) using validated antibodies. The score values of GAL and GAL(1–3)–R expression were calculated and statistically evaluated. Results: GAL and GAL(1)–R were expressed in various bile duct cell types. GAL(2)–R was only slightly but still expressed in almost all the examined tissues, and GAL(3)–R specifically in cholangiocytes and capillaries. In a small pCCA patient cohort (n = 18), high GAL expression correlated with good survival, whereas high GAL(3)–R correlated with poor survival. Conclusions: Our in-depth characterisation of the GAL system in the healthy human biliary duct and pCCA in a small patient cohort revealed that GAL and GAL(3)–R expression in tumour cells of pCCA patients could potentially represent suitable biomarkers for survival.