Similar results were observed following cyclopamine treatment, as well as a reduction in the expression of Bmi1 and the ATP-binding drug transporter ABCG2, suggesting that Bmi1 may function as a downstream Hh target in pancreatic cancer, as in breast cancer, and Hh blockade can reverse chemoresistance via ABCG2 downregulation in pancreatic CSCs [127,130]. Here, ABCG2 is linked to breast cancer.