We confirmed that the gene expression levels of cholangiocyte markers (Epithelial cell adhesion molecule (EpCAM), cytokeratin7 (CK7), cytokeratin19 (CK19)) were upregulated to the same level as those of HuCCT1 cells, a human bile duct carcinoma cell line (Fig. S1B), whereas hepatocyte markers (cytochrome P450 family 3 subfamily A member 4 (CYP3A4), albumin (ALB)) decreased (Fig. S1C) compared to those of PHHs, as previously reported for the human liver organoids produced by Huch et al.4,5. Here, KRT19 is linked to bile duct carcinoma.