P-glycoprotein (p-gp) expression and function as an independent prognostic factor in childhood acute lymphoblastic leukemia

8503 Background: Little is known about the prognostic role of multidrug resistance (MDR) in newly diagnosed childhood with acute lymphoblastic leukemia (ALL). The aim of this retrospective study was to evaluate in 85 children with ALL the impact of P-glycoprotein 170 (p-gp) product of the mdr-1 gene on achievement of complete remission (CR), and clinical outcome. Methods: MDR-1 protein expression was performed by immunocytochemistry (ICC), and flow cytometry (FC). MDR-1 functional activity was performed by rhodamine (Rhd)-123 efflux test with or without verapamil. All patients enrolled in our study were treated with AIEOP 91–95 protocols. Results: Forty patients (47%) expressed MDR1 protein at significant levels, and 45 (53%) were MDR1 negative. Forty-three of the last patients were also negative for MDR1 function, while 34 out of 40 (85%) patients MDR-1 positive preserved the function. Rhd-123 efflux was inhibited by the MDR modulator verapamil in 12 of 40 (30%) patients. After induction treatment, CR wa...