Prognostic Significance of Multidrug Resistance Gene 1 (MDR1), Multidrug Resistance-Related Protein (MRP) and Lung Resistance Protein (LRP) mRNA Expression in Acute Leukemia.

The prognostic significance of multidrug resistance (MDR) gene expression is controversial. We investigated whether multidrug resistance gene 1 (MDR1), multidrug resistance-related protein (MRP) and lung resistance protein (LRP) mRNA expression are associated with outcomes in acute leukemia patients. At diagnosis we examined MDR1, MRP and LRP mRNA expression in bone marrow samples from 71 acute leukemia patients (AML 39, ALL 32) using nested reverse transcription polymerase chain reaction (RT-PCR). The expression of each of these genes was then expressed as a ratio in relation to ß-actin gene expression, and the three genes were categorized as being either not expressed (0), weakly expressed (1+), moderately expressed (2+) or strongly expressed (3+). MDR1, MRP and LRP mRNA expression was detected in 23.9%, 83.1% and 45.1%, respectively, of acute leukemia patients. LRP mRNA expression was significantly associated with resistance to induction chemotherapy in acute leukemia patients, and in the AML proportion of these patients, compared to LRP-negative patients (p=0.02 and p=0.03, respectively). MRP and high MDR1 mRNA expression was associated with poorer 2-year survival (P=0.049 and p=0.04, respectively) compared to MRP-negative and non-high MDR1 mRNA-expressing patients, respectively. Patients expressing both MRP and LRP mRNA had poorer outcomes in response to induction chemotherapy and had worse 2-year survival compared to patients not expressing both genes. The present data suggest that MDR gene expression affects CR and survival rates in acute leukemia patients. Thus, determination of MDR gene expression at diagnosis appears likely to provide useful prognostic information for acute leukemia patients.