ARID5B, IKZF1 and non-genetic factors in the etiology of childhood acute lymphoblastic leukemia: the ESCALE study.

Genome-wide association studies (GWAS) have identified that frequent polymorphisms in ARID5B and IKZF1, two genes involved in lymphoid differentiation, increase the risk of childhood acute lymphoblastic leukemia (ALL). These findings markedly modified the current field of research on the etiology of ALL. In this new context, the present exploratory study investigated the possible interactions between these at-risk alleles and the non-genetic suspected ALL risk factors that were of sufficient prevalence in the French ESCALE study: maternal use of home insecticides during pregnancy, preconception paternal smoking, and some proxies for early immune modulation, i.e. breastfeeding, history of common infections before age one year, and birth order. The analyses were based on 434 ALL cases and 442 controls of European origin, drawn from the nationwide population-based case-control study ESCALE. Information on non-genetic factors was obtained by standardized telephone interview. Interactions between rs10740055 in ARID5B or rs4132601 in IKZF1 and each of the suspected non-genetic factors were tested, with the SNPs coded as counts of minor alleles (trend variable). Statistical interactions were observed between rs4132601 and maternal insecticide use (p = 0.012), breastfeeding p = 0.017) and repeated early common infections (p = 0.0070), with allelic odds ratios (OR) which were only increased among the children not exposed to insecticides (OR = 1.8, 95%CI: 1.3, 2.4), those who had been breastfed (OR = 1.8, 95%CI: 1.3, 2.5) and those who had had repeated early common infections (OR = 2.4, 95%CI: 1.5, 3.8). The allelic ORs were close to one among children exposed to insecticides, who had not been breastfed and who had had no or few common infections. Repeated early common infections interacted with rs10740055 (p = 0.018) in the case-only design. Further studies are needed to evaluate whether these observations of a modification of the effect of the at-risk alleles by non-genetic factors are chance findings or reflect true underlying mechanisms.

Childhood acute leukemia, maternal beverage intake during pregnancy, and metabolic polymorphisms.

PURPOSE: This study aimed to analyze the associations between childhood acute leukemia (AL) and maternal caffeinated beverage consumption during pregnancy, and to explore interactions between caffeinated and alcoholic beverage consumption and polymorphisms of enzymes involved in caffeine and ethanol metabolisms. METHODS: The data were generated by the French ESCALE study, which included 764 AL cases and 1,681 controls in 2003-2004. The case and control mothers were interviewed on their consumption habits during pregnancy using a standardized questionnaire. Genotypes of the candidate alleles (NAT2*5 rs1801280, ADH1C*2 rs698 and rs1693482, CYP2E1*5 rs2031920 and rs3813867) were obtained using high-throughput genotyping and imputation data for 493 AL cases and 549 controls with at least two grandparents born in Europe. RESULTS: Maternal regular coffee consumption during pregnancy was associated with childhood AL (OR = 1.2 [1.0-1.5], p = 0.02); the odds ratios increased linearly with daily intake (p for trend <0.001; >2 cups per day vs. no or less than 1 cup per week: AL: OR = 1.6 [1.2-2.1], lymphoblastic AL: OR = 1.5 [1.1-2.0], myeloblastic AL: OR = 2.4 [1.3-4.3]). The association was slightly more marked for children born to non-smoking mothers. Lymphoblastic AL was also associated with cola soda drinking (OR = 1.3 [1.0-1.5], p = 0.02). No significant gene-environment interactions with coffee, tea, cola soda, or alcohol drinking were observed. CONCLUSION: This study provides additional evidence that maternal coffee consumption during pregnancy may be associated with childhood AL. Coffee consumption is a prevalent habit and its potential involvement in childhood AL needs to be considered further.

Folic acid supplementation, MTHFR and MTRR polymorphisms, and the risk of childhood leukemia: the ESCALE study (SFCE).

PURPOSE: Fetal folate deficiency may increase the risk of subsequent childhood acute leukemia (AL), since folates are required for DNA methylation, synthesis, and repair, but the literature remains scarce. This study tested the hypothesis that maternal folic acid supplementation before or during pregnancy reduces AL risk, accounting for the SNPs rs1801133 (C677T) and rs1801131 (A1298C) in MTHFR and rs1801394 (A66G) and rs1532268 (C524T) in MTRR, assumed to modify folate metabolism. METHODS: The nationwide registry-based case-control study, ESCALE, carried out in 2003-2004, included 764 AL cases and 1,681 controls frequency matched with the cases on age and gender. Information on folic acid supplementation was obtained by standardized telephone interview. The genotypes were obtained using high-throughput platforms and imputation for untyped polymorphisms. Odds ratios (OR) were estimated using unconditional regression models adjusted for potential confounders. RESULTS: AL was significantly inversely associated with maternal folic acid supplementation before and during pregnancy (OR = 0.4; 95 % confidence interval: [0.3-0.6]). MTHFR and MTRR genetic polymorphisms were not associated with AL. However, AL was positively associated with homozygosity for any of the MTHFR polymorphisms and carriership of both MTRR variant alleles (OR = 1.6 [0.9-3.1]). No interaction was observed between MTHFR, MTRR, and maternal folate supplementation. CONCLUSION: The study findings support the hypothesis that maternal folic acid supplementation may reduce the risk of childhood AL. The findings also suggest that the genotype homozygous for any of the MTHFR variants and carrying both MTRR variants could be a risk factor for AL.

Childhood leukemia around French nuclear power plants--the Geocap study, 2002-2007.

The aim of this work is to study the risk of childhood acute leukemia (AL) around French nuclear power plants (NPPs). The nationwide Geocap case-control study included the 2,753 cases diagnosed in mainland France over 2002-2007 and 30,000 contemporaneous population controls. The last addresses were geocoded and located around the 19 NPPs. The study used distance to NPPs and a dose-based geographic zoning (DBGZ), based on the estimated dose to bone marrow related to NPP gaseous discharges. An odds ratio (OR) of 1.9 [1.0-3.3], based on 14 cases, was evidenced for children living within 5 km of NPPs compared to those living 20 km or further away, and a very similar association was observed in the concomitant incidence study (standardized incidence ratio (SIR)=1.9 [1.0-3.2]). These results were similar for all the 5-year-age groups. They persisted after stratification for several contextual characteristics of the municipalities of residence. Conversely, using the DBGZ resulted in OR and SIR close to one in all of the dose categories. There was no increase in AL incidence over 1990-2001 and over the entire 1990-2007 period. The results suggest a possible excess risk of AL in the close vicinity of French NPPs in 2002-2007. The absence of any association with the DBGZ may indicate that the association is not explained by NPP gaseous discharges. Overall, the findings call for investigation for potential risk factors related to the vicinity of NPP and collaborative analysis of multisite studies conducted in various countries.

Spatial variations of childhood acute leukaemia in France, 1990-2006: global spatial heterogeneity and cluster detection at 'living-zone' level.

Childhood acute leukaemia (AL) accounts for a third of childhood cancers. Analysing the spatial distribution of the incidence of AL and its lymphoblastic and myeloblastic subtypes may contribute to the identification of risk factors. This national registry-based study aimed to evaluate global spatial heterogeneity in the incidence rates of AL and to detect clusters in France over the period 1990-2006 on the 'living-zone' scale. Between 1990 and 2006, 7675 cases of AL were registered in the National Registry of Childhood Haematopoietic malignancies. Their spatial distribution in the 1895 'living zone' was first evaluated with two tests for global spatial heterogeneity (Potthoff-Witthinghill and Rogerson's tests) and then with the SaTScan and FleXScan methods, which aim to locate spatial and space-time clusters. Over 1990-2006, no spatial heterogeneity of AL or its subtypes was evidenced. In addition, none of the most likely clusters identified with SaTScan and FleXScan over the whole period was significant, and the systematic search for space-time clusters yielded nonsignificant results. However, when three subperiods were considered, five statistically significant nonoverlapping spatial clusters were identified. This study did not find evidence of any global spatial heterogeneity of AL incidence rates in France over the period 1990-2006. Although no significant spatial cluster was detected over the whole period, the study identified a few significant spatial clusters in specific periods. Even though the significance levels of those clusters do not strongly support the existence of local risk factors, the clusters may still reflect a slight impact of shared risk factors, including background environmental exposures, which require further investigation.

Maternal smoking during pregnancy, genetic polymorphisms of metabolic enzymes, and childhood acute leukemia: the ESCALE study (SFCE).

PURPOSE: This study explored interactions between prenatal exposure to maternal smoking and polymorphisms in metabolic genes in the risk of childhood acute leukemia (AL). METHODS: The data were generated by the ESCALE study, which included 764 AL cases and 1,681 controls in 2003-2004. The data on maternal smoking during pregnancy were obtained by standardized telephone interview of the cases' and controls' mothers. The genotypes CYP1A1*2A/2B (rs4646903), CYP2E1*5 (rs2031920, rs3813867), NQO1*2 (rs1800566), NAT2*5 (rs1801280), and EPHX1 exon 3 (rs1051740) and exon 4 (rs2234922) were obtained using a high-throughput platform and imputation for untyped polymorphisms. The analyses were restricted to the 493 cases (433 cases of lymphoblastic (ALL) and 51 of myeloblastic (AML) leukemia) and 441 controls with at least 2 grandparents born in Europe, who were genotyped with individual call rates greater than 95%. Odds ratios were estimated by logistic regression in case-control analyses and, for gene-gene and gene-environment interactions, by case-only analyses. RESULTS: ALL and AML were not associated with either maternal smoking during pregnancy or candidate polymorphisms in CYP1A1, CYP2E1, EPHX1, and NQO1. Carrying two NAT2*5 alleles was significantly associated with ALL (OR = 1.8 [1.3-2.5]). The analyses also suggested an interaction between three genes involved in benzene metabolism CYP2E1, NQO1, and EPHX1. There was no interaction between maternal smoking and any of the polymorphisms under study. CONCLUSIONS: The ESCALE study did not evidence the interaction between CYP1A1*2A/2B and maternal smoking suggested previously. The association with NAT2*5 and the gene-gene interactions need to be replicated.

Detection of clusters of a rare disease over a large territory: performance of cluster detection methods.

BACKGROUND: For many years, the detection of clusters has been of great public health interest. Several detection methods have been developed, the most famous of which is the circular scan method. The present study, which was conducted in the context of a rare disease distributed over a large territory (7675 cases registered over 17 years and located in 1895 units), aimed to evaluate the performance of several of the methods in realistic hot-spot cluster situations. METHODS: All the methods considered aim to identify the most likely cluster area, i.e. the zone that maximizes the likelihood ratio function, among a set of cluster candidates. The circular and elliptic scan methods were developed to detect regularly shaped clusters. Four other methods that focus on irregularly shaped clusters were also considered (the flexible scan method, the genetic algorithm method, and the double connected and maximum linkage spatial scan methods). The power of the methods was evaluated via Monte Carlo simulations under 27 alternative scenarios that corresponded to three cluster population sizes (20, 45 and 115 expected cases), three cluster shapes (linear, U-shaped and compact) and three relative risk values (1.5, 2.0 and 3.0). RESULTS: Three situations emerged from this power study. All the methods failed to detect the smallest clusters with a relative risk lower than 3.0. The power to detect the largest cluster with relative risk of 1.5 was markedly better for all methods, but, at most, half of the true cluster was captured. For other clusters, either large or with the highest relative risk, the standard elliptic scan method appeared to be the best method to detect linear clusters, while the flexible scan method localized the U-shaped clusters more precisely than other methods. Large compact clusters were detected well by all methods, with better results for the circular and elliptic scan methods. CONCLUSIONS: The elliptic scan method and flexible scan method seemed the most able to detect clusters of a rare disease in a large territory. However, the probability of detecting small clusters with relative risk lower than 3.0 remained low with all the methods tested.