EPCAM and bile duct carcinoma: 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