Expression of the multidrug resistance-associated protein (MRP) in acute leukaemia

A semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to investigate and compare transcription levels of the human multidrug resistance gene (MDR1) and the recently described multidrug resistance-associated protein (MRP) in 105 samples from patients with acute leukaemia at presentation and relapse. MRP gene expression was significantly greater in samples from patients with acute lymphoblastic leukaemia (ALL) compared with samples from normal peripheral mononuclear cells (PBMC) and patients with de novo acute myeloid leukaemia (AML). MRP gene expression was found to be higher in patients with relapsed de novo AML compared to those at presentation but prior therapy did not affect MRP gene expression in ALL. MDR1 gene expression was significantly lower in ALL patients compared to normal PBMC and AML samples. Samples from patients with secondary AML had higher levels of MDR1 expression than those of de novo AML. No changes of MDR1 expression were observed in AML or ALL at relapse. No correlation was observed between MDR1 and MRP gene expression in this group of patients. Our results suggest that MRP expression may be of prognostic importance in AML but the significance of the increased levels we have detected remain unclear.