Copper Ceruloplasmin as a Potential Biomarker of Biliary Tract Cancers: A Pilot Study

Copper (Cu) and its distribution among circulating Cu-binding proteins may be altered in cancer and could provide diagnostic or prognostic information. However, the specificity of individual Cu species as biomarkers of biliary tract cancers (BTCs) remains unclear. In this pilot study, we investigated Cu speciation in serum samples from 10 patients with BTCs before and after chemotherapy or immuno-chemotherapy and 10 healthy individuals. Cu species were separated using conjoint liquid chromatography (CLC) with inductively coupled plasma mass spectrometry (ICP-MS) detection. The CLC column, comprising two immunoaffinity (α-HSA) and one DEAE anion-exchange disk, separated Cu bound to ceruloplasmin (Cu-Cp), low-molecular-mass (Cu-LMM), and human serum albumin (Cu-HSA) species, which were quantified by isotope dilution ICP-MS or protein standard–based quantification. Cu speciation analysis revealed that Cu-Cp concentrations followed total serum Cu concentrations in patients with BTCs before and after chemotherapy or immuno-chemotherapy and in healthy individuals, while Cu-HSA and Cu-LMM concentrations also decreased. Cu-Cp accounted for approximately 90% of total serum Cu across all groups, and there were no significant differences in its relative contribution to total Cu. Cu-Cp accounted for approximately 90% of total serum Cu across the investigated groups, with no statistically significant differences in its relative contribution. These preliminary findings suggest that changes in Cu-Cp concentrations largely reflect changes in total serum Cu rather than BTC-specific alterations in Cu distribution. Therefore, Cu-Cp is unlikely to serve as a specific biomarker for BTCs. However, further studies involving larger patient cohorts are needed to establish the potential diagnostic and prognostic relevance of Cu-Cp in BTCs.