CEACAM6 and cholangiocarcinoma: When looking at the most upregulated proteins identified in our study, several proteins, such as protein S100-P [63, 64], carcinoembryonic antigen-related cell adhesion molecule 6 [65], keratin, type I cytoskeletal 17 [66, 67], thymidine phosphorylase [68, 69], heat shock protein 90 alpha/beta [70] and olfactomedin-4 [71, 72], are well established as upregulated proteins and tentative biomarkers in CCA.