Nine proteins (3%) were identified as less abundant in cholangiocarcinoma, which included pro-activator polypeptide isoform a pre-pro-protein, carboxypeptidase B, chymotrypsin-like elastase family member 2A, chymotrypsin like elastase family member 3B, and chymotrypsin-C. Here, CELA2A is linked to cholangiocarcinoma.