Comparing the overall benign (PSC and benign) and malignant lesions (pancreatic cancer and CCA), several proteins including myeloperoxidase, inter-alpha-trypsin inhibitor heavy chain H4, complement C3, ceruloplasmin, alpha-2-macroglobulin, apolipoprotein B-100 and kininogen-1 isoform 2 were found to be significantly elevated in patients with malignant biliary strictures. Here, C3 is linked to cholangiocarcinoma.