CD44 and acute myeloid leukemia: Resistance to the PI BTZ has been observed, and in human AML cells has been reported to be unrelated to the presence of multi-drug resistance (MDR) genes such as P-glycoprotein 1/ATP-binding cassette sub-family B member 1 (P-gp1/ABCB1), multi-drug resistance protein 1 (MRP1/ABCC1), Breast Cancer Resistance Protein (BCRP/ABCG2), and lung resistance-related protein (LRP).