RAS mutations in early age leukaemia modulated by NQO1 rs1800566 (C609T) are associated with second-hand smoking exposures.

BACKGROUND: Deregulation of the MAPK genes signalling caused by somatic mutations have been implied in leukaemia pathogenesis, including RAS mutation (RASmut) in acute myeloid leukaemia (AML), which has been associated with intra-uterine chemical exposures. A case-case study was conducted in order to explore maternal and child exposures to tobacco smoking associations with early age leukaemia (EAL). METHODS: Covariables of reference were MLL rearrangements (MLL-r), RASmut and NQO1 rs1800566 (C609T). Samples from 150 acute lymphoblastic leukaemia (ALL) and 85 AML were included. Maternal exposures were assessed using a structured questionnaire with demographic, personal habits and residence history information. Restriction fragment length polymorphism and denaturing high performance liquid chromatography were used to screen FLT3, KRAS, and NRAS mutations; direct sequencing was performed to validate the results. NQO1 polymorphism was detected by real-time allelic discrimination technique. RESULTS: Overall, RASmut were detected in 28.7% of EAL cases; BRAFmut was found only in one AML patient. Higher rate of KRASmut was found in ALL (30.3%) compared to AML (20.8%) with MLL-r; RASmut showed an association with second-hand tobacco smoking exposures (OR, 3.06, 95% CI, 1.03-9.07). A considerable increased risk for EAL with the combination of RASmut and NQO1 609CT (OR, 4.24, 95% CI, 1.24-14.50) was observed. CONCLUSIONS: Our data demonstrated the increased risk association between maternal smoking and EAL with MLL-r. Additionally, suggests that children second-hand tobacco exposures are associated with increased risk of EAL with RASmut modulated by NQO1 rs1800566 (C609T).

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.

Polimorfismo dos genes NQO1 e PON1 na etiologia das leucemias agudas infantis

As leucemias pediátricas são doenças hetereogêneas, consequentes da combinação de susceptibilidade genética individual e exposições a fatores ambientais. Polimorfismos em genes que codificam enzimas do metabolismo modificam correlações de riscos entre exposições e as leucemias. Baseados nas hipóteses que as leucemias na infância têm origem durante a vida intra-uterina, estudos demonstraram associações de exposições maternas durante a gestação à pesticidas e algumas substâncias medicamentosas. Especulamos se os polimorfismos NQO1C609T, PON1Q192R e PON1L55M poderiam influenciar na etiologia das leucemias infantis. O objetivo principal deste estudo foi determinar a freqüência dos polimorfismos nos genes NQO1 e PON1 em crianças com leucemias agudas e suas mães para avaliar as possíveis associações de riscos entre susceptibilidade genética e exposição ambiental. Foram testadas amostras brasileiras de crianças com diagnóstico de leucemia aguda (578); 393 amostras de crianças saudáveis não-sindrômicas (controles), bem como, amostras das respectivas mães. As genotipagens dos genes NQO1 e PON1 foram realizadas através da técnica de discriminação alélica por PCR em tempo real utilizando sondas TaqMan. O genótipo mutante do polimorfismo NQO1C609T confere um risco para o desenvolvimento de leucemias agudas [OR=2,5; IC95%, 1,05-5,88] às crianças com idade ≥24 meses. Na análise estratificada por subtipo leucêmico, nas leucemias mielóides o genótipo mutante confere um risco elevado [OR=5,44; IC95%, 1,08-27,63] nas crianças entre 13-24 meses de idade. A somatória dos genótipos heterozigoto e homozigoto-mutante do NQO1 apresentou uma tendência de risco 2,0 vezes maior da ocorrência nas leucemias com rearranjos do gene MLL [IC95%, 0,94-4,57]. A presença do alelo polimórfico do NQO1C609T nas mães apresenta risco para leucemias agudas pediátricas [OR=1,76; IC95%, 1,03-3,02]. O polimorfismo PON1L55M apresentou associação de risco para LLA, tanto com o genótipo mutante [OR=3,21; IC95%, 1,21-8,51], quanto com a somatória dos genótipos heterozigoto e homozigoto-mutante [OR= 1,94; IC95%, 1,02-3,68]. Este risco aumenta nas crianças com idade entre 13-24 meses [OR=3,22; IC95%, 1,15-8,99]. Foram realizadas análises de exposição materna a pesticidas, antibióticos e infusões de ervas. O polimorfismo do gene NQO1 não mostrou associação de risco, enquanto os polimorfismos do gene PON1 mostraram associações com as exposições e apresentaram magnitudes de risco independentes do tipo de exposição

Pediatric leukemias are heterogeneous diseases which result from the combination of individual genetic susceptibility factors and environmental exposures. Polymorphisms in genes that codify metabolic enzymes alter the risk associations between exposures and leukemias. Based on the prenatal origin of leukemias, studies have demonstrated association between maternal exposures during pregnancy to pesticides or some medicines and childhood leukemia. We speculated whether the polymorphisms NQO1C609T, PON1Q192R and PON1L55M could influence the etiology of the infant leukemias. The main objective of this study was to determine the frequency of these polymorphisms in children with acute leukemia and their mothers to evaluate the possible risk associations between genetic susceptibility and environmental exposures. Samples from children diagnosed with acute leukemia were tested (cases); samples from health children (controls) as well as samples from the respective mothers of both cases and controls were also tested. The genotyping of NQO1 and PON1 was performed using the allelic discrimination real time PCR assay using TaqMan probes. The NQO1C609T mutant genotype was associated with a higher risk of acute leukemia development [OR=2.5; CI95%, 1.05-5.88] in children ≥24 months-old. In the stratified analysis considering the leukemia subtypes, the group of myeloid leukemias presented an increased risk [OR=5.44; CI95%, 1.08-27.63] in children between 13-24 months-old. The sum of NQO1 heterozygous and mutant homozygous alleles showed a trend of 2-fold higher risk of leukemia occurrence in association with MLL gene rearrangements [CI95%, 0.94-4.57]. The polymorphism NQO1C609T within the mothers’ group was associated with childhood leukemias [OR=1.76; CI95%, 1.03-3.02]. The polymorphism PON1L55M presented a risk association with ALL, both considering the homozygous mutant genotype [OR=3.21; CI95%, 1.21-8.51], as well as considering the sum of the heterozygous and the mutant homozygous genotypes [OR= 1.94; CI95%, 1.02-3.68]. This risk increases in children aged between 13-24 months [OR=3.22; CI95%, 1.15-8.99]. The maternal exposures during pregnancy to pesticides, antibiotics and herbal infusions were analyzed in comparison to the genotypes. While no interaction risk associations were observed with the NQO1 polymorphism, the PON1 polymorphisms showed associations with the exposures and presented magnitudes independent of the type of exposure