Effects of splicing-regulatory polymorphisms in ABCC2, ABCG2, and ABCB1 on methotrexate exposure in Chinese children with acute lymphoblastic leukemia.

Abstract

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters play an important role in the response to methotrexate (MTX). In this study, we investigated the frequency distribution of three splicing-regulatory polymorphisms in ABC transporters (ABCC2 rs2273697 G>A, ABCG2 rs2231142 G>T, and ABCB1 rs1128503 A>G) and their effects on MTX concentrations and the clinical outcome in a Chinese pediatric population with acute lymphoblastic leukemia (ALL). A fluorescence polarization immunoassay was used to measure the serum MTX concentrations in 24h (C24h) and 42h (C42h). The Sequenom MassARRAY system was used for single-nucleotide polymorphism (SNP) genotyping. The study population had significantly lower frequencies of ABCC2 rs2273697 A, ABCG2 rs2231142 G, and ABCB1 rs1128503 G than African and European samples (P < 0.05). The dose-normalized MTX concentrations after 24h and the proportion of C42h > 0.5µmol/L were significantly lower in patients with the ABCG2 rs2231142 GG genotype than in patients with the GT or TT genotype (P = 0.01 and 0.006, respectively). No significant effects on MTX pharmacokinetics were observed for ABCC2 rs2273697 and ABCB1 rs1128503 polymorphisms. Bioinformatics analysis suggested that the three SNPs overlapped with the putative binding sites of several splicing factors. In conclusion, our study confirmed the ethnicity-based differences in the distribution of the three investigated SNPs. The ABCG2 rs2231142 polymorphism exerted a significant effect on the level of MTX exposure. These findings may help explain the variability in MTX responses and optimize MTX treatment in pediatric patients with ALL.