RESUMEN
<p><b>OBJECTIVE</b>To investigate the relationship between genetic polymorphism in exon 12 C1236T, exon 21 G2677T/A and exon 26 C3435T of the multidrug resistance 1 (MDR1) gene and the risk of childhood acute lymphocytic leukemia (ALL).</p><p><b>METHOD</b>A total of 176 patients with ALL and a cohort of 170 matched healthy subjects were included. SNaPshot SNP typing was used to determine the genotypes of MDR1 C1236T, G2677T/A, C3435T. Based on the clinical data, the relationship between genetic polymorphism of MDR1 and the risk of childhood ALL was analyzed.</p><p><b>RESULT</b>There was significant difference in the distribution of genotype of MDR1 C3435T between the group of controls and cases. The mutant homozygous TT genotype was found to be associated with occurrence of ALL (P = 0.000; OR = 4.504). The data show evidence of pairwise linkage disequilibrium between the three common SNPs (C1236T-G2677T/A-C3435T). The haplotypes of TTT, TGC, CGC and CAC were predominant. The haplotype CGT distributed significantly differently between the groups of controls and cases (P = 0.034). The frequency of the haplotype TTT/TTT in the high risk group was higher than the other groups (P = 0.037).</p><p><b>CONCLUSION</b>The present findings suggest that 3435C→T polymorphism in MDR1 gene may be a genetic susceptibility factor for ALL. The haplotype of MDR1 (C1236T-G2677T/A-C3435T) could be the clinical parameter at diagnosis.</p>