Genetic variability in N-acetyltransferase 2 gene determines susceptibility to childhood lymphoid or myeloid leukemia in Brazil.

Seven single nucleotide polymorphisms (SNPs) were genotyped in 535 Brazilian children (158 with acute lymphoblastic leukemia [ALL], 74 with acute myeloid leukemia [AML] and 303 controls). The subjects were classified as fast or slow acetylators based on their genotypic variants. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals. N-acetyltransferase 2 (NAT2) SNP 341T > C frequency was higher among both leukemia subtypes compared to controls. There was also a significant difference in the frequency of SNP 590G > A in AML (OR, 1.57, 1.07-2.30). The haplotypes *14A, *5A and *5C conferred an increased risk in cases of ALL, while *14E, *6B and *6F conferred an increased risk for AML. An age-dependent analysis demonstrated that the NAT2 slow-acetylators conferred an increased risk association with leukemia in children ≤ 1 year old (OR, 7.91, 3.87-16.16) and also in older children (1 ≥ 10 years old) (OR, 1.53, 1.01-2.31). However, in this latter group the magnitude was reduced. The results demonstrate that the different NAT2 haplotypes contribute to the risk of either ALL or AML.

N-acetyltransferase 2 polymorphisms and susceptibility to infant leukemia with maternal exposure to dipyrone during pregnancy.

BACKGROUND: Maternal exposure to dipyrone during pregnancy has been associated with risk of infant leukemia (IL). N-Acetyltransferase 2 (NAT2) enzyme acetylates dipyrone, resulting in a detoxified metabolite. We performed genotyping to identify the distribution of NAT2 polymorphisms in duo samples from mothers and children previously investigated in a case-controlled study of IL. METHODS: Samples from 132 IL, 131 age-matched controls, mothers of cases (n = 86), and mothers of controls (n = 36) were analyzed. PCR-RFLP assays were used to determine the NAT2 variants 191G>A, 282C>T, 341T>C, 481C>T, 590G>A, 803A>G, and 857G>A. The test for case-control differences in the distribution of genotypes was based on χ(2) statistics. Unconditional logistic regression was used to examine the association between maternal exposure to dipyrone during the index pregnancy, IL, and NAT2 phenotypes. Crude and adjusted odds ratios (OR) are given with the 95% confidence interval (95% CI). RESULTS: NAT2 slow-acetylation haplotypes were associated with IL (OR, 8.90; 95% CI, 1.71-86.7). An association between IL and NAT2 phenotype was observed in IL whether the mothers reported dipyrone exposures (OR, 4.48; 95% CI, 1.88-10.7) or not (OR, 4.27; 95% CI, 1.75-10.5). The combination of NAT2 slow/slow (mother/child) phenotypes confers a higher risk of IL (OR, 30.0; 95% CI, 5.87-279.7). CONCLUSION: NAT2 slow-acetylation profiles are associated with IL regardless of maternal exposure to dipyrone during pregnancy. IMPACT: Further recommendations about medicine exposures during pregnancy should take into account that infants with the maternal NAT2 slow-acetylation genotypes might be particularly vulnerable to greater risk.

MTHFR 677C-->T and 1298A-->C polymorphisms in children with Down syndrome and acute myeloid leukemia in Brazil.

Down syndrome (DS) is an important risk factor associated with acute leukemia (AL). The presence of polymorphisms that reduce 5,10-methylenetetrahydrofolate reductase (MTHFR) activity has been linked to the multifactorial leukemogenic process. The authors have conducted a study to test whether 677C-->T and/or 1298A-->C polymorphisms of MTHFR would play an additional role in susceptibility of acute myeloid leukemia (AML) in DS children. They also verified whether any polymorphism in the MTHFR gene was associated with the risk of DS. Genetic polymorphisms determination was carried out in 248 samples from healthy individuals as controls and a total of 115 DS children (65 without leukemia and 50 with AML). The present study failed to reveal any association between these polymorphisms and risk of AML in DS children. The data also indicate that MTHFR polymorphisms are not associated with risk of being a DS child.

Association between the MTHFR A1298C polymorphism and increased risk of acute myeloid leukemia in Brazilian children.

Methylenetetrahydrofolate reductase (MTHFR) is an essential enzyme in the metabolism of folate. The presence of polymorphisms that reduce the activity of MTHFR has been linked to the multifactor process of development of acute leukemia. A case control study was conducted on Brazilian children in different regions of the country with the aim of investigating the role of MTHFR C677T and A1298C polymorphisms as risk factors in the development of acute myeloid leukemia (AML). We used the polymerase chain reaction restriction fragment length polymorphism method to genotyping 182 AML and 315 healthy individuals. The genotype 677 CT was associated with decreased risk [odds ratio (OR), 0.37; confidence interval (CI) 95%, 0.14 - 0.92], whereas 1298 AC genotype was linked with an increased risk [OR, 2.90; CI 95%, 1.26 - 6.71] of developing AML in non-white children. Further epidemiological study is needed to unravel the complex multiple gene-environment interactions in the role of the AML leukemogenesis.

The role of methylenetetrahydrofolate reductase in acute lymphoblastic leukemia in a Brazilian mixed population.

The polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene are associated with leukemogenesis. In order to investigate the influence of two polymorphisms in the MTHFR gene, 677C>T and 1298A>C, on the risk of acute lymphoblastic leukemia (ALL) we performed a case-control study in children from different Brazilians' regions. Genotyping of 176 ALL and 199 unselected healthy subjects was performed using PCR-RFLP assay. There was no association between the 677C>T or 1298A>C and risk of ALL in total case-control sample. However, 677T allele was linked to a decrease risk of ALL [odds ratio (OR), 0.43; 95% confidence interval (CI), 0.22-0.86], whereas the 1298A>C polymorphism presents an elevated risk factor [OR, 2.01; 95% CI, 1.01-3.99] in non-White children. Our investigation provides interesting data concerning the opposite effect of A1298C polymorphisms, particularly in the light of relatively scarce data regarding the MTHFR role in leukemia susceptibility in different populations.

Influência da metileno-tetrahidrofolato redutase na patogênese das leucemias agudas infantis / Influence of the methylenetetrahydrofolate reductase in the pathogenesis of the childhood acute leukemia

As leucemias resultam de uma interação adversa entre gene-ambiente, com susceptibilidade condicionada, pelo menos em parte, por polimorfismos de múltiplos genes. Como a metilenotetrahidrofolato redutase (MTHFR) possui papel chave no metabolismo do folato, alterações na sua atividade (resultante de polimorfismos) ou alterações na suplementação de folato, podem influenciar na síntese, reparo e metilação de DNA. Neste estudo, determinamos a frequência dos polimorfismos 677C maior que T e 1298A maior que C do gene MTHFR em 177 crianças menores de 16 anos com leucemias agudas (LA) de diversas regiões brasileiras e em 249 amostras de indivíduos normais como o grupo controle. O método utilizado para genotipagem foi PCR-RFLP. As frequências dos genótipos 677CC, 677CT e 677TT foram 51 por cento, 40 por cento e 9 por cento nos controles, 57 por cento, 33 por cento e 10 por cento para os casos de leucemia linfoblástica aguda (LLA), e 49 por cento, 39 por cento e 12 por cento para os casos de leucemia mielóide aguda (LMA), respectivamente. Já as frequências dos genótipos 1298AA, 1298AC e 1298CC foram respectivamente 62 por cento, 31 por cento e 7 por cento nos controles, 51 por cento, 41 por cento e 8 por cento nos casos de LLA e, 67 por cento, 31 por cento e 2 por cento nos casos de LMA, respectivamente. Quando comparamos casos de LLA com os controles, para o polimorfismo 677C maoir que T, encontramos um OR igual a 0,7 (0,5 - 1,2) e OR igual a 1,0 (0,4 - 2,1) para os genótipos CT e TT, respectivamente. Para o polimorfismo 1298A maior que C, o OR foi 1,6 (1,0 - 2,5) e 1,3 (0,6-3,0) para os genótipos AC e CC, respectivamente. Para os casos de LMA, o OR foi 1,0 (0,5 - 2,1) para o genótipo CT, e 1,3 (0,5 - 3,9) para o genótipo TT. Para o genótipo AC, encontramos um OR igual a 0,9 (0,4 - 1,9); para o genótipo CC, o OR foi 0,3 (0,04 - 2,3). Não houve diferenças entre as frequências do MTHFR 677C maior que T e1298A maior que C em ambos os grupos na análise global. Os resultados indicam que MTHFR 677C maior que T e 1298A maior que C não conferem efeito protetor contra a LA infantil.