Additionally, ABCB1 was highlighted as a fundamental factor contributing to MDR and overexpression of P‐gp is significantly associated with the acquisition of MDR as well as the reduced sensitivity to chemotherapy in many cancers.33, 34 Therefore, we investigated the association between TET1 and P‐gp expression in CCA with gemcitabine resistance. The gene discussed is ABCB1; the disease is cholangiocarcinoma.