['The present study was designed to evaluate the association of multidrug resistance gene (MDR1), multidrug resistance-associated protein (MRP) gene and lung resistance protein (LRP) gene expression (mRNA levels) with risk factors such as phenotype, age and leukocyte count in newly diagnosed childhood acute lymphoblastic leukemia, because biological mechanisms contributing to risk factors were not known.', 'Expression of the MDR1, MRP and LRP genes in leukemic cells from 40 pediatric patients was quantitated using the reverse transcriptase polymerase chain reaction method. The associations of expression of these genes with age and leukocyte count, which are known as risk factors for acute lymphoblastic leukemia (ALL), were analyzed. Moreover, the associations with clinically classified risk-related groups (high-risk ALL and low-risk ALL) were also investigated.', 'No positive correlations between expression of these genes and age or leukocyte count were found. The expression of these genes was not different among clinically classified risk-related groups.'] Does expression of multidrug resistance-related genes contribute to risk factors in newly diagnosed childhood acute lymphoblastic leukemia?