NQO1 rs1800566 (C609T), PON1 rs662 (Q192R), and PON1 rs854560 (L55M) polymorphisms segregate the risk of childhood acute leukemias according to age range distribution.

PURPOSE: The risk of developing childhood leukemia has been associated with gene polymorphisms that decrease the activity of detoxifying metabolic enzymes and enzymes involved in systemic oxidative stress. We investigated the NQO1 and PON1 polymorphisms for associations with susceptibility to childhood leukemia. METHODS: Samples from 1,027 Brazilian children (519 acute lymphoblastic leukemia, ALL; 107 acute myeloid leukemia, AML; 401 controls) were analyzed. TaqMAN real-time assays were used to determine the NQO1 rs1800566 (C609T), PON1 rs662 (Q192R), and PON1 rs854560 (L55M) frequencies. Logistic regression was used to evaluate the association of polymorphisms with cases and controls, with age and somatic fusion genes (MLL-r and ETV6-RUNX1) as covariables. RESULTS: Children with at least one NQO1 variant allele were at lower risk for developing infant AML (odds ratio (OR) 0.26, 95 % confidence interval (CI) 0.10-0.68); no association was detected for ALL. PON1 rs854560 (L55M) was associated with an increased risk of developing childhood leukemia (LM + MM, OR 1.93, 95 % CI 1.32-2.81). The PON1 rs662 R192R genotype had a statistically significant decreased frequency in ALL (OR 0.64, 95 % CI 0.43-0.93). Infant ALL cases were more likely to harbor homozygous PON1 rs854560 alleles than controls (OR 1.72, 95 % CI 1.03-2.89); at least one M allele was associated with an increased risk of ALL in children older than 1 year (OR 1.99, 95 % CI 1.17-3.3). CONCLUSIONS: The NQO1 rs1800566 (C609T), PON1 rs854560 (L55M), and PON1 rs662 (Q192R) polymorphisms modified risk depending on leukemia subtype (decreased in AML, increased and decreased in ALL, respectively), age strata, and variant genotype combinations.

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.

Clinical and molecular epidemiology of neonatal leukemia in Brazil.

The clinical and molecular findings of 77 cases of neonatal leukemia (NL) and 380 of infant leukemia (IL) were selected to distinguish features between NL and IL. Somatic gene mutations associated with acute leukemia including FLT3, RAS and PTPN11 were revisited. There were 42 cases of congenital leukemia associated with Down syndrome (DS) and 39 of these cases presented features of acute myeloid leukemia (AML)-M7. Twenty-seven of the DS cases underwent spontaneous remission and were reclassified as a transient myeloproliferative disorder. GATA1 mutations were found in 70% of these cases. In non-DS, frequent abnormalities were MLL rearrangements, mainly MLL-AFF1 in acute lymphoblastic leukemia and MLL-MLLT3 in AML. The FLT3 mutation was not found, while RAS (n = 4) and PTPN11 (n = 2) mutations were identified and reported for the first time in NL. There was substantial evidence to support that somatic abnormalities occur in utero. Thus, congenital leukemia is a good model for understanding leukemogenesis.

Detection of mutations in GATA1 gene using automated denaturing high-performance liquid chromatography and direct sequencing in children with Down syndrome.

Denaturing high-performance liquid chromatography (dHPLC) was developed to screen DNA variations by separating heteroduplex and homoduplex DNA fragments by ion-pair reverse-phase liquid chromatography. In this study, we have evaluated the dHPLC screening method and direct sequencing for the detection of GATA1 mutations in peripheral blood and bone marrow aspirates samples from children with Down syndrome (DS). Cases were ascertained consecutively as part of an epidemiological study of DS and hematological disorders in Brazil. A total of 130 samples corresponding to 115 children with DS were analysed using dHPLC and direct sequencing methods to detect mutations in GATA1 exons 2, 3 and 4 gene sequences. The overall detection rate of sequencing and dHPLC screening methods was similar. Twenty mutations were detected in exon 2 and one mutation in exon 3 (c.231_232 dupGT) sequences of acute megakaryoblastic leukemia and transient leukemia samples. Four GATA1 mutations were newly described [c.155C > G; c.156_178 del23 bp; c.29_30 del GG; c.182C > A and c.151A > T,c.153_162 del 10 bp). Out of four, three had single nucleotide change. In conclusion, our results indicate that dHPLC is an efficient and valuable tool for GATA1 mutational analysis.

Alterações renais nas doenças falciformes / Renal abnormalities in sickle cell disease

A doença falciforme associa-se a anormalidades renais estruturais glomerulares e tubulares, alterações hemodinâmicas e da síntese dos hormônios renais (eritropoetina, renina e prostaglandinas). Estas se iniciam na infância, em conseqüência da anemia crônica, fluxo sangüíneo aumentado, e eventos de veno-oclusão intraparenquimatosos, principalmente na medular renal. Na doença SS, a taxa de filtração glomerular encontra-se elevada desde os primeiros anos de vida e decresce com a idade. Decorrente de anormalidade tubular distal está a hipostenúria com as manifestações clínicas de poliúria, noctúria, enurese e susceptibilidade a desidratação, diminuição da capacidade de acidificar urina e excretar potássio. As anormalidades de túbulo proximal se traduzem por secreção aumentada de creatinina e ácido úrico, reabsorção aumentada de fosfatos e b2-microglobulina. A hipersecreção de creatinina superestima a taxa de filtração glomerular (FG), tornando o clearance de creatinina impróprio como detector precoce da deterioração da função renal. A proteinúria ocorre em 29 por cento-50 por cento dos pacientes acima de 10 anos de idade; 2/3 destes evoluem para insuficiência renal crônica de evolução ruim. A literatura apresenta benefícios consistentes com o uso de inibidores de enzimas conversoras de angiotensina (IECA) na redução da proteinúria, que talvez tenha impacto na progressão da insuficiência renal. Microalbuminúria (MA) é um marcador sensível da glomerulopatia falcêmica que precede a proteinúria. Na população pediátrica documenta-se prevalência de 19 por cento, estando associado com idade, síndrome torácica aguda, níveis de Hb baixos e altas de leucometrias. Recomenda-se screening para MA a partir de 10 anos de idade. Em andamento estudo multicêntrico com uso precoce de hidroxiuréia na prevenção das lesões orgânicas crônicas (Baby HUG).

Sickle cell disease is associated with glomerular and tabular structural abnormalities, hemodynamic changes and renal hormone synthesis alterations (erythropoietin, renin, prostaglandins). These changes appear in childhood with consequences including chronic anemia, increased blood flow and vaso-occlusion, especially within the renal medulla. In SS disease, the glomerular filtration rate (GFR) is markedly higher in young patients but this drops with age. As a consequence of abnormalities in the distal nephron function there is reduced capacity of urine acidification, potassium excretion and hyposthenuria. Among the clinical effects of the latter are polyuria, nocturia, enuresis and a susceptability for dehydration. Abnormalities of the proximal tubular function include increased reabsorption of phosphates and b2 microglobulin and incresed secretion of uric acid and creatinine. For this reason, creatinine clearance significantly overestimates the glomerular filtration rate making creatinine learance inappropriate to detect early renal function impairment. Proteinuria occurs in 29-50 percent of over 10-years-old SS patients with 2/3 progressing to chronic renal failure. The use of angiotensin-converting enzyme inhibitor proves to be successful to reduce proteinuria which may have an impact of the progression of renal failure. Microalbuminuria is a sensitive marker of sickle nephropathy that precedes proteinuria. In pediatric population a prevalence of 19 percent of microbuminuria was observed; a percentage that increases with age and has a positive association with lower hemoglobin levels, higher leucocyte counts and acute chest syndrome. Screening for microalbuminuria is recommended from the age of 10 years old. A multicentric trial is ongoing with the aim of demonstrate potential benefits of early hydroxyurea therapy in the prevention of chronic organic lesions. (BabyHUG).

Biological diversity variations of pediatric acute leukemia in Brazil: contribution of immunophenotypic profiles to epidemiological studies

Os autores descrevem as características biológicas de 1.459 crianças com leucemias agudas no Brasil, para comparar os efeitos de diferentes perfis imunofenotípicos com fatores ambientais que podem estar associados à etiologia das leucemias linfoblásticas agudas (LLA). As classificações morfológicas e imunofenotípicas combinadas foram aplicadas em 96% dos casos. Nestes, 55% foram classificados como LLA de células B precursoras (LLA-Bp) que compreendem LLA-pro-B e LLA-comum, 15% LLA-T, e 1,6% LLA-B. A proporção de LLA-Bp e LLA-T difere entre si quanto à raça, com 59% das LLA-Bp em crianças brancas, enquanto 60,7% LLA-T em crianças não-brancas. No entanto, as análises proporcionais de brancos versus não brancos para cada subtipo, quando ajustadas por idade, são semelhantes em crianças maiores de 6 anos (60,3% LLA-Bp e 59,3% LLA-T), mas diferem substancialmente em crianças menores, com 63,6% de LLA-Bp e 37,3% de LLA-T em brancos (0,0001). Estes resultados são consistentes com excesso de LLA-Bp em crianças brancas mais jovens, embora a distribuição entre LLA-Bp e LLA-T em cada região seja semelhante sem significado estatístico. As taxas de incidências de LLA calculadas para cada região variaram de 2,2, 2,6 e 3,3/105 casos por ano para Bahia, Rio de Janeiro e Brasília, respectivamente. Para avaliar se o pico de incidência observado de LLA-Bp estaria relacionado com incidência de infeção viral, nós observamos que LLA-Bp apresentou uma curva ascedente de casos no verão e inverno, enquanto LLA-T apresentou pico de incidência no outono. Este estudo adiciona informações sobre epidemiologia de leucemias agudas no Brasil, no qual sugere que o subtipo LLA-comum poderia estar associado com tempo de exposição a infecção viral requerendo futuras análises específicas.