Previously, gemcitabine in combination with nab-paclitaxel was reported to increase PD-L1 expression in pancreatic cancer25; however, there has been no report specific to the effect of gemcitabine on PD-L1 expression in CCA, except for our previously published finding that gemcitabine alone could increase PD-L1 expression in highly gemcitabine-resistant KKU213A CCA cells14. This evidence concerns the gene CD274 and cholangiocarcinoma.