High multidrug resistance protein activity in acute myeloid leukaemias is associated with poor response to chemotherapy and reduced patient survival

Multidrug resistance protein (MRP) activity was investigated in 44 newly diagnosed acute myeloid leukaemia (AML) patients using a functional assay based on efflux of carboxy-2',7'-dichlorofluorescein, an anionic dye handled by both MRP1 and MRP2. Elevated MRP transport was detected in 29% of cases. but was not significantly correlated with sex, age. white blood cell count at diagnosis or karyotype. In contrast, it was associated with secondary AML (P = 0.002), CD34 positivity (P = 0.041) and P-glycoprotein activity (P = 0.01). There was a lower rate of complete remission in MRP-positive patients versus MRP-negative patients (23% versus 81%: P = 0.001): overall survival was also better for MRP-negative patients (P = 0.004). These data indicate a probable role for MRP activity in the clinical outcome of AML.