Messenger RNA analysis of the multidrug resistance related protein (MRP1) and the lung resistance protein (LRP) in de novo and relapsed childhood acute lymphoblastic leukemia.

In this study, 86 children (58 initial ALL and 28 children with relapsed disease) were investigated for lung resistance protein (LRP) and multidrug resistance related protein (MRPI)-mRNA expression by semiquantitative RT-PCR. The majority of investigated cases demonstrated variable LRP and MRP1 mRNA expression, when normalized for beta-microglobulin expression. LRP and MRPI mRNA expression may be coordinately regulated, as expression of both transcripts was found to be significantly correlated (p = 0.0001). No differences of LRP and MRP expression were observed between initial and relapsed stage patients (LRP: p = 0.89 and for MRP: p = 0.09). The prognostic value of both resistance mechanisms was subjected to Kaplan-Meier analysis for event-free survival. For this analysis the patients were divided into groups with high or low LRP or MRPI mRNA expression by utilizing the median value as the cut-off point. Overexpression of both resistance mechanisms had no prognostic significance in our retrospective study (log-rank test for LRP: p = 0.12 and for MRPI: p = 0.95), however, patients who showed high LRP expression exhibited a lower tendency of remaining in continuous first remission.