High Pgp expression is detected in about 50% of AML blast samples, is more common in older (71%), than in younger cohorts (35%) and is associated with poor response to chemotherapy.29,30 Similarly to elderly AML, secondary leukemias present higher Pgp expression compared to de novo AML (61 versus 37, P < 0.001),31 which may lead to reduced responsiveness to chemotherapy and chemoresistance. This evidence concerns the gene PGP and acute myeloid leukemia.