ABCG2 and cholangiocarcinoma: Recently, it has been revealed that the down-regulation of C1GALT1 in cholangiocarcinoma (CCA) promoted the expression of immature core 1 O-glycan, enhancing CCA progression, which was associated with the up-regulation of ABC transporter genes and anti-apoptotic proteins [32], which are both effects associated with the emergence of MDR phenotypes.