ABCB1 and cholangiocarcinoma: In another study, the administration of β-escin (a compound that induces β-catenin degradation) in combination with some of the most commonly used antitumor drugs for treating CCA patients (5-fluorouracil, vincristine sulfate, and mitomycin C) enhanced the response of human CCA cells due in part to reduced MDR1 protein expression [103].