[Analysis on GST-Pi genetic polymorphism in children with acute leukemia]

To study the frequency distribution patterns of the genetic polymorphisms for glutathione S-transferase Pi (GST-Pi) in children with acute leukemia, and explore the possible relationship of GST-Pi gene mutation to the vulnerability of children with leukemia and the chemotherapeutic response.

Direct DNA sequencing was applied to detect the genotype polymorphism in 85 healthy children as the control group and 120 children with acute leukemia. The distribution difference of the genotypes between them was analyzed.

Gene mutation rate of GST-Pi exon5 was 47.5% in children with acute leukemia, significantly higher than that of 31.8% in the control group (OR = 1.944, 95% CI 1.088-3.473), and this polymorphism distribution pattern was similar to that reported abroad. The mutation rate was much higher in ALL group than in others groups and was not significantly between the AML children and the control group. The overall mutation rate of B-lineage ALL (60.3%) was markedly higher than that of T-ALL (47.1%), but the homozygous mutation rate of the latter group (17.6%) was much higher than that of the former group (3.4%) (P < 0.05). The average survival time of the children with wild type exon5 was 24 months, longer than that of the mutation group (17.6 months), however with no statistical difference (P > 0.05). The genotype of exon5 had no effect on the survival time of AML children. No Ala(114)Val variant genotype of GST-Pi exon6 reported in literatures was found in this study, but two new mutant genotypes were discovered. A/G hybridity at 99 loci of exon6 was found in one healthy child and such hybrid genotype did not result in amino acid alteration. G-->T/G bases hybridity at 103 loci of exon6 occurred in two children with leukemia, leading to GAC of Asp (aspartic acid) replaced by TAC of Try (tyrosine) at 147 loci of the protein peptide chain, producing Asp(147) Try hybrid mutation with a genotypic frequency of 1.7%.

The gene mutation of GST-Pi exon5 is one of the potential vulnerable factors in leukemogenesis of the Chinese children and the genetic polymorphism of exon6 in Chinese is greatly different from that in other races. The role of the newly discovered variant genotype Asp(147) Try in leukemogenesis remains to be further studied.