As O-GlcNAcylation occurs on thousandsof protein substrates, targeting OGT and OGA using either chemicalor biological methodologies might sabotage normal biological processes.In addition, other functional consequences of K18 O-GlcNAcylation at other sites still remain ambiguous because onlya limited number of tools exist to study its site-specific O-GlcNAcylation effects.59 Furtherpreclinical and clinical studies are needed to confirm the truenessof CCA-associated O-GlcNAcylated proteins as diagnosis/prognosisindicators. This evidence concerns the gene OGA and cholangiocarcinoma.