To analyze the properties of PBX1, we investigated which transcript is the main mRNA variant and found that PBX1_202 (ENST00000367897.5, also known as PBX1b) was the predominant splice variant in the initial patient cohort as well as in the biliary and CCA cell lines (Figure S5A–C and Supporting information Note). This evidence concerns the gene PBX1 and cholangiocarcinoma.