Before-treatment and on-treatment biopsies were compared, revealing that mtIDH1 inhibition induced a more differentiated morphology of cholangiocarcinoma cells on H&E staining and the expression of hepatocyte lineage markers HNF-4α, FOXA1 (HNF-3α), FOXA2 (HNF-3β), and PPARA. This evidence concerns the gene FOXA1 and cholangiocarcinoma.