ABCG2 and chronic myelogenous leukemia, BCR-ABL1 positive: One of them is the resistance due to the reduced intracellular drug accumulation by increasing its expulsion, as occurs in CML cells overexpressing ATP-binding cassette (ABC) transporters such as P-glycoprotein (ABCB1), multidrug resistance protein 1 (ABCC1), and the breast cancer resistance protein (ABCG2) [43].