Tumoral heterogeneity of hepatic cholangiocarcinomas revealed by MALDI imaging mass spectrometry

Cholangiocarcinoma ( CC ) is the second most common primary malignancy of the liver. Although all CC derive from biliary epithelial cells, two main subtypes, hilar ( H ), and peripheral ( P ) CC are described. The objective of the study was to compare, using MALDI imaging mass spectrometry ( MALDI IMS ), in situ proteomic profiles of H ‐ and P ‐ CC in order to assess whether these subtypes may express different markers and to describe their respective localizations. Twenty‐seven CC (16 P ‐ CC and 11 H ‐ CC ) were subjected to MALDI IMS . Proteomic data were submitted to a dedicated cross‐classification comparative design, enabling comparison of the entire generated spectra. Immunohistochemistry was performed for validation. Comparative analysis yielded a list of 19 differential protein peaks for the two subtypes, 14 of which were overexpressed in H ‐ CC and five in P ‐ CC . Among H ‐ CC protein markers, most discriminant were human neutrophil peptides 1–3 that were expressed mainly by tumor cells and S 100 proteins ( A 6 and A 11) that were restricted to the stromal area. In P ‐ CC , thymosin β4 was diffusely overexpressed. These results highlight the potential of MALDI IMS to discover new relevant biomarkers of CC and to characterize the heterogeneity of the two different subtypes.