Transmembrane transporters from the ATP Binding Cassette (ABC) superfamily ABCB1 (MDR1), ABCC1, ABCG2 are involved in the acquired resistance in AML, acute lymphocytic leukemia (ALL) and chronic myeloid leukemia (CML) [55,56,57]. The gene discussed is ABCG2; the disease is acute lymphoblastic leukemia.