EPHX1 rs1051740 T>C (Tyr113His) is strongly associated with acute myeloid leukemia and KMT2A rearrangements in early age.

Experimental and epidemiological data have shown that acute myeloid leukemia in early-age (i-AML) originates prenatally. The risk association between transplacental exposure to benzene metabolites and i-AML might be influenced by genetic susceptibility. In this study, we investigated the relationship between genetic polymorphisms in CYP2E1, EPHX1, MPO, NQO1, GSTM1 and GSTT1 genes, and i-AML risk. The study included 101 i-AMLs and 416 healthy controls. Genomic DNA from study subjects was purified from bone marrow or peripheral blood aspirates and genotyped for genetic polymorphisms by real-time PCR allelic discrimination, Sanger sequencing and multiplex PCR. Crude and adjusted odds ratios (OR, adjOR, respectively) with 95% confidence intervals (95% CI) were assessed using unconditional logistic regression to estimate the magnitude of risk associations. EPHX1 rs1051740 T>C was associated with i-AML risk under the co-dominant (adjOR 3.04, P = 0.003) and recessive (adjOR 2.99, P = 0.002) models. In stratified analysis, EPHX1 rs1051740 was associated with increased risk for i-AML with KMT2A rearrangement (adjOR 3.06, P = 0.045), i-AML with megakaryocytic differentiation (adjOR 5.10, P = 0.008), and i-AML with type I mutation (adjOR 2.02, P = 0.037). EPHX1 rs1051740-rs2234922 C-G haplotype was also associated with increased risk for i-AML (adjOR 2.55, P = 0.043), and for i-AML with KMT2A rearrangement (adjOR 3.23, P = 0.034). Since EPHX1 enzyme is essential in cellular defense against epoxides, the diminished enzymatic activity conferred by the variant allele C could explain the risk associations found for i-AML. In conclusion, EPHX1 rs1051740 plays an important role in i-AML's genetic susceptibility by modulating the carcinogenic effects of epoxide exposures in the bone marrow.

MTHFR rs1801133 polymorphism is associated with increased risk of B-cell precursor lymphoblastic leukaemia with recurrent genetic aberrations of fetal origin.

BACKGROUND: Childhood acute lymphoblastic leukaemia (ALL) is a heterogeneous disease associated with multiple risk factors including genetic susceptibility. Polymorphisms in folate genes have been associated with a protective effect against ALL, although some studies contradict these findings. We aimed to test whether there is an association between the MTHFR rs1801133 variant and the occurrence of B-cell precursor ALL (BCP-ALL) taking in account molecularly distinct subtypes of fetal origin. METHODS: We performed a case-control genotyping study with 2067 samples, 1309 ALL and 758 controls, from children aged ≤ 15 years for MTHFR rs1801133 polymorphism. Risk associations were calculated by odds ratios estimated with unconditional logistic regression, adjusted for frequency-matched ethnic groups. RESULTS: Overall, MTHFR rs1801133 does not impact ALL risk in children with more than 6 years of age. A significant positive association for MTHFR rs1801133 variant was found for ALL with KMT2A-r in the dominant model (adj. OR, 1.48, 95 % CI, 1.01-2.17), while ETV6-RUNX1 and Hyperdiploid subgroups have shown a borderline effect (adj. OR, 1.33, 95 % CI, 0.99-1.78). CONCLUSIONS: The polymorphism MTHFR rs1801133 increased the risk of infant ALL in Brazilian population.

Acute myeloid leukaemia at an early age: Reviewing the interaction between pesticide exposure and KMT2A-rearrangement.

Acute myeloid leukaemia (AML) in early childhood is characterised by a high frequency of recurrent genomic aberrations associated with distinct myeloid subtypes, clinical outcomes and pathogenesis. Genomic instability is the first step of pathogenic mechanism in early childhood AML. A sum of adverse events is necessary to the development of infant AML (i-AML), which includes latency of biochemical-molecular and cellular effects. Inherited genetic susceptibility associated with exposures to biotransformation substances can modulate the risk of DNA damage and it is a very important piece in the pathogenic puzzle. In this review, we have aimed to explore the chain of events in the time-points of the natural history of i-AML, which includes maternal exposures during pregnancy, the speculations about the formation of somatic mutations during foetal life and the secondary genomic aberrations associated with i-AML. The modulation of risk conferred by xenobiotic metabolism´s genes variants is the bottom line of the pathogenic process. Since we have conducted observational and molecular investigations in early childhood leukaemia, the data focused here is based on Brazilian findings with summarised results of our experience with epidemiological and molecular studies in early-age leukaemia.

Molecular Characterization of Pediatric Acute Myeloid Leukemia: Results of a Multicentric Study in Brazil.

BACKGROUND AND AIMS: The biological characterization of childhood acute myeloid leukemia (c-AML) is an important outcome predictor. In Brazil, very little is known about the frequency of AML subgroups, although c-AML accounts for about 18% of leukemias. We carried out this study to investigate the contribution of type I and II gene mutations in the probability of overall survival (pOS) of c-AML in Brazil. METHODS: Seven hundred and three de novo pediatric AML cases (2000-2015) were assessed throughout a multicentric network study. Mutations in hotspot regions of FLT3, NRAS, KRAS, PTPN11, and c-KIT genes were analyzed as well as fusion genes (RUNX1-RUNX1T1, MLL/KMT2A-r, CBFß-MYH11, and PML-RARα) associated with AML. Patients were treated out of the clinical trial although following the BFM-AML2004 protocol. Acute promyelocytic leukemia (APL) was treated differently. AML with Down syndrome was excluded. RESULTS: There were significant differences in gene mutations among age ranges (≤2 years-old; >2-10 years old and ≥11 years old) and the nonrandom association between type I/II mutations. Lower white blood cell count (≤50 × 109/L) was associated with RUNX1-RUNX1T1, whereas higher WBC with CBFß-MYH11 (p <0.05). Cumulative pOS in 5 years was 37.7 ± 2.8% for total AMLs and 59.8 ± 6.2% for APL (p = 0.03). pOS differences were observed between Brazilian regions. The South-Southeast regions had a better 5-year pOS, whereas the Midwest region presented the poorest pOS (23.7 ± 4.9%). PTPN11 mutations conferred an adverse prognosis as an independent prognostic factor. CONCLUSIONS: Identification of genetic subgroups contributes to the molecular epidemiology and biology of AML worldwide, reflecting the profile of pediatric AML cases in Brazil.