The multidrug resistance-associated protein 3 (MRP3) is associated with a poor outcome in childhood ALL and may account for the worse prognosis in male patients and T-cell immunophenotype.

The family of multidrug resistance-associated proteins (MRPs) belongs to the superfamily of adenosine triphosphate-binding-cassette (ABC) transporters, which have the ability to function as outward pumps for chemotherapeutic drugs and therefore might be involved in drug resistance. In this study the expression of the MRP2, MRP3, MRP4, MRP5, and SMRP genes was measured using TaqMan real-time polymerase chain reaction (PCR) in 103 children with previously untreated acute lymphoblastic leukemia (ALL) (precursor B-cell ALL [B-ALL], n = 71; T-cell ALL [T-ALL], n = 32). All 5 genes were expressed with a great variability.