Aetiology of childhood leukaemia

Childhood cancer incidence in British Indians & Whites in Leicester, 1996-2008

BACKGROUND

South Asians in England have an increased risk of childhood cancer but incidence by their individual ethnicities using self-assigned ethnicity is unknown. Our objective was to compare the incidence of childhood cancer in British Indians and Whites in Leicester, which has virtually complete, self-assigned, ethnicity data and the largest population of Indians in England.

METHODS

We obtained data on all cancer registrations from 1996 to 2008 for Leicester with ethnicity obtained by linkage to the Hospital Episodes Statistics database. Age-standardised incidence rates were calculated for childhood cancers in Indians and Whites as well as rate ratios, adjusted for age.

RESULTS

There were 33 cancers registered among Indian children and 39 among White children. The incidence rate for Indians was greater compared to Whites for all cancers combined (RR 1.82 (95% CI 1.14 to 2.89); p = 0.01), with some evidence of increased risk of leukaemia (RR 2.20 (0.95 to 5.07); p = 0.07), lymphoma (RR 3.96 (0.99 to 15.84); p = 0.04) and central nervous system tumours (RR 2.70 (1.00 to 7.26); p = 0.05). Rates were also higher in British Indian children compared to children in India.

CONCLUSIONS

British Indian children in Leicester had an increased risk of developing cancer compared to White children, largely due to a higher incidence of central nervous system and haematological malignancies.

Fertility treatments and childhood acute leukemia

SUMMARY Fertility treatments are enjoying increasing use around the world. As they intervene at such a sensitive time at the start of development, the effects of these treatments on children have been closely scrutinized, with generally reassuring results. Reports of a possible slightly increased risk of acute leukemia (AL) in children born after assisted reproductive technology have been investigated by a series of studies. Research in this field could provide clues not only to the effects of different treatments, but perhaps also to the etiology of AL, which remains largely enigmatic. This special report investigates the evidence of a possible association specifically between childhood AL and assisted reproductive technology, and offers an outlook for the direction of this important field in the future.

Fertility treatments, congenital malformations, fetal loss, and childhood acute leukemia: the ESCALE study (SFCE)

BACKGROUND

This study investigated the relationships between childhood acute leukemia (AL) and selective maternal and birth characteristics, including congenital malformations and the use of fertility treatment, for which the literature remains scarce.

PROCEDURE

The national registry-based case-control study ESCALE was carried out in France in 2003-2004. Population controls were frequency matched with cases on age and gender. Data were obtained from structured telephone questionnaires. Odds ratios (OR) and their 95% confidence intervals were estimated using unconditional regression models adjusted for potential confounders.

RESULTS

In all, 764 cases of AL (648 lymphoblastic AL (acute lymphoblastic leukemia, ALL) and 101 myeloblastic AL) and 1,681 controls were included. The AL cases' mothers reported congenital malformations more frequently than the controls' mothers (OR = 1.5 [1.0-2.4]). ALL was significantly associated with the use of fertility treatment for the index pregnancy (OR = 1.9 [1.3-2.8]). In particular, ALL was associated with ovulation induction only (OR = 2.6 [1.6-4.3]), but not with in vitro fertilization (IVF, OR = 1.0 [0.4-2.3]) or artificial insemination (OR = 1.3 [0.5-3.9]). A positive association was also observed for the difficulty of becoming pregnant without fertility treatment (OR = 1.5 [1.0-2.1]). AL was positively associated with a history of voluntary abortion (OR = 1.4 [1.1-1.8]) but not with a history of spontaneous (OR = 0.8 [0.7-1.0]) or therapeutic (OR = 0.7 [0.5-1.1]) abortion.

CONCLUSION

The results suggest that subfertility in itself and ovulation induction may be associated with ALL, and support a positive association with congenital malformations. The links with the various types of fertility drugs and the underlying causes of infertility need to be investigated further.

Occupational exposure to pentachlorophenol causing lymphoma and hematopoietic malignancy for two generations

Objective:

Pentachlorophenol (PCP) is characterized as likely carcinogen of lymphoma and hematopoietic neoplasm. But the carcinogenicity to human was uncertain based on population studies. A systematic review was conducted to explore two kinds of associations, one was between the workers exposed to PCP with lymphoma and hematopoietic neoplasm, the other was between childhood lymphoma and leukemia with their parents exposed to PCP.

Methods:

Systematic search for epidemiologic studies was carried out and the data were collected from MEDLINE database and from the reference lists of relevant studies. Data were extracted from 20 included studies published between 1986 and 2012.

Results:

The meta-analysis suggested a significant association between lymphoma and workers’ occupational exposing to PCP, for the pooled odds ratio = 2.57 (95% confidence interval (CI) = 1.52–4.35). The subgroup analysis indicated significant association for non-Hodgkin’s lymphoma, but not for Hodgkin’s disease. The cohort studies also showed comparatively higher relative risk (RR) and standardized mortality ratio (SMR). Two of the cohort studies found increased RR as the cumulative exposure time added. Another cohort study discovered that the white males had significantly elevated non-Hodgkin’s lymphoma mortality (SMR = 1.98, 95% CI = 1.15–3.17), and males of other races had increased leukemia mortality (SMR = 4.57, 95% CI = 1.25–11.7). For the relationship of childhood leukemia and parental exposure to PCP, three published studies suggested an increased risk of childhood leukemia because of their parental exposure to PCP at the preconception period.

Conclusion:

Our review provided the evidence that occupational exposure of workers to PCP might increase the risk of lymphoma and hematopoietic neoplasm in themselves and in their children.

Exposure to benzene and childhood leukaemia: a pilot case-control study

OBJECTIVES

Main purpose To evaluate the feasibility of a measurement-based assessment of benzene exposure in case-control studies of paediatric cancer; Additional aims To identify the sources of exposure variability; to assess the performance of two benzene biomarkers; to verify the occurrence of participation bias; to check whether exposures to benzene and to 50 Hz magnetic fields were correlated, and might exert reciprocal confounding effects.

DESIGN

Pilot case-control study of childhood leukaemia and exposure to benzene assessed by repeated seasonal weekly measurements in breathing zone air samples and outside the children's dwellings, with concurrent determinations of cotinine, t-t-muconic acid (MA) and sulfo-phenylmercapturic acid (S-PMA) in urine.

PARTICIPANTS

108 cases and 194 controls were eligible for inclusion.

RESULTS

Full-participation was obtained from 46 cases and 60 controls, with low dropout rates before four repeats (11% and 17%); an additional 23 cases and 80 controls allowed the collection of outdoor air samples only. The average benzene concentration in personal and outdoor air samples was 3 μg/m(3) (SD 1.45) and 2.7 μg/m(3) (SD 1.41), respectively. Personal exposure was strongly influenced by outdoor benzene concentrations, higher in the cold seasons than in warm seasons, and not affected by gender, age, area of residence or caseness. Urinary excretion of S-PMA and personal benzene exposure were well correlated. Outdoor benzene levels were lower among participant controls compared with non-participants, but did not differ between participant and non-participant cases; the direction of the bias was found to depend on the cut-point chosen to distinguish exposed and unexposed. Exposures to benzene and extremely low-frequency magnetic fields were positively correlated.

CONCLUSIONS

Repeated individual measurements are needed to account for the seasonal variability in benzene exposure, and they have the additional advantage of increasing the study power. Measurement-based assessment of benzene exposure in studies of childhood leukaemia appears feasible, although it is financially and logistically demanding.

Leukemia risk in children exposed to benzene and PM10 from vehicular traffic: a case-control study in an Italian population

Benzene, a recognized occupational leukemogen in adults, has been hypothesized to also increase the risk of childhood leukemia. We carried out a population-based case–control study in a northern Italy community involving 83 cases with acute childhood leukemia diagnosed in the years 1998–2009 and 332 matched controls. We assessed residential exposure to benzene and to particulate matter ≤10 μm (PM₁₀) from motorized traffic using geocoded residences and detailed emission and dispersion modeling. Exposure to benzene, and to a lesser extent to PM₁₀, appeared to be independently associated with an excess leukemia risk. When we stratified the study population by age and by leukemia subtype, the relative risk associated with benzene exposure was higher among children aged less than 5 years, and despite small numbers this relation appeared to be considerably stronger for acute myeloid leukemia than for acute lymphoblastic leukemia. Overall, these findings suggest that exposure to low levels of benzene released from motorized traffic may increase the risk of childhood leukemia, and suggest a possible independent effect of PM₁₀, although unmeasured confounding due to other pollutants cannot be ruled out.

Antenatal maternal bereavement and childhood cancer in the offspring: a population-based cohort study in 6 million children

Background:

Prenatal stress may increase the susceptibility to childhood cancer by affecting immune responses and hormonal balance. We examined whether antenatal stress following maternal bereavement increased the risk of childhood cancer.

Methods:

All children born in Denmark from 1968 to 2007 (N=2 743 560) and in Sweden from 1973 to 2006 (N=3 400 212) were included in this study. We compared cancer risks in children born to women who lost a first-degree relative (a child, spouse, a parent, or a sibling) the year before pregnancy or during pregnancy with cancer risks in children of women who did not experience such bereavement.

Results:

A total of 9795 childhood cancer cases were observed during follow-up of 68 360 707 person years. Children born to women who lost a child or a spouse, but not those who lost other relatives, had an average 30% increased risk of any cancer (hazard ratio (HR) 1.30, 95% confidence interval (CI) 0.96–1.77). The HRs were the highest for non-Hodgkin disease (512 cases in total, HR 3.40, 95% CI 1.51–7.65), hepatic cancer (125 cases in total, HR 5.51, 95% CI 1.34–22.64), and testicular cancer (86 cases in total, HR 8.52, 95% CI 2.03–37.73).

Conclusion:

Our data suggest that severe antenatal stress following maternal bereavement, especially due to loss of a child or a spouse, is associated with an increased risk of certain childhood cancers in the offspring, such as hepatic cancer and non-Hodgkin disease, but not with childhood cancer in general.

MondoA is highly overexpressed in acute lymphoblastic leukemia cells and modulates their metabolism, differentiation and survival

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. To identify novel candidates for targeted therapy, we performed a comprehensive transcriptome analysis identifying MondoA (MLXIP) - a transcription factor regulating glycolysis - to be overexpressed in ALL compared to normal tissues. Using microarray-profiling, gene-set enrichment analysis, RNA interference and functional assays we show that MondoA overexpression increases glucose catabolism and maintains a more immature phenotype, which is associated with enhanced survival and clonogenicity of leukemia cells. These data point to an important contribution of MondoA to leukemia aggressiveness and make MondoA a potential candidate for targeted treatment of ALL.

Spectrum of HLA associations: the case of medically refractory pediatric acute lymphoblastic leukemia

Although studies of HLA and disease now date back some 50 years, a principled understanding of that relationship has been slow to emerge. Here, we examine the associations of three HLA loci with medically refractory pediatric acute lymphoblastic leukemia (pALL) patients in a case-control study involving 2,438 cases and 41,750 controls. An analysis of alleles from the class I loci, HLA-A and HLA-B, and the class II locus DRB1 illuminates a spectrum of extremely significant allelic associations conferring both predisposition and protection. Genotypes constructed from predisposing, protective, and neutral allelic categories point to an additive mode of disease causation. For all three loci, genotypes homozygous for predisposing alleles are at highest disease risk while the favorable effect of homozygous protective genotypes is less striking. Analysis of A-B and B-DRB1 haplotypes reveals locus-specific differences in disease effects, while that all three loci influence pALL; the influence of HLA-B is greater than that of HLA-A, and the predisposing effect of DRB1 exceeds that of HLA-B. We propose that the continuum in disease susceptibility suggests a system in which many alleles take part in disease predisposition based on differences in binding affinity to one or a few peptides of exogenous origin. This work provides evidence that an immune response mediated by alleles from several HLA loci plays a critical role in the pathogenesis of pALL, adding to the numerous studies pointing to a role for an infectious origin in pALL.

Identification of germline susceptibility loci in ETV6-RUNX1-rearranged childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a malignant disease of the white blood cells. The etiology of ALL is believed to be multifactorial and likely to involve an interplay of environmental and genetic variables. We performed a genome-wide association study of 355 750 single-nucleotide polymorphisms (SNPs) in 474 controls and 419 childhood ALL cases characterized by a t(12;21)(p13;q22) - the most common chromosomal translocation observed in childhood ALL - which leads to an ETV6-RUNX1 gene fusion. The eight most strongly associated SNPs were followed-up in 951 ETV6-RUNX1-positive cases and 3061 controls from Germany/Austria and Italy, respectively. We identified a novel, genome-wide significant risk locus at 3q28 (TP63, rs17505102, P(CMH)=8.94 × 10(-9), OR=0.65). The separate analysis of the combined German/Austrian sample only, revealed additional genome-wide significant associations at 11q11 (OR8U8, rs1945213, P=9.14 × 10(-11), OR=0.69) and 8p21.3 (near INTS10, rs920590, P=6.12 × 10(-9), OR=1.36). These associations and another association at 11p11.2 (PTPRJ, rs3942852, P=4.95 × 10(-7), OR=0.72) remained significant in the German/Austrian replication panel after correction for multiple testing. Our findings demonstrate that germline genetic variation can specifically contribute to the risk of ETV6-RUNX1-positive childhood ALL. The identification of TP63 and PTPRJ as susceptibility genes emphasize the role of the TP53 gene family and the importance of proteins regulating cellular processes in connection with tumorigenesis.

In vivo interactions between ionizing radiation, inflammation and chemical carcinogens identified by increased DNA damage responses

Exposure to ionizing radiation or a variety of chemical agents is known to increase the risk of developing malignancy and many tumors have been linked to inflammatory processes. In most studies, the potentially harmful effects of ionizing radiation or other agents are considered in isolation, mainly due to the large number of experiments required to assess the effects of mixed exposures with different doses and different schedules, and the length of time and expense of studies using disease as the measure of outcome. Here, we have used short-term DNA damage responses to identify interactive effects of mixed exposures. The data demonstrate that exposure to ionizing radiation on two separate occasions ten days apart leads to an increase in the percentage of cells with a sub-G(0) DNA content compared to cells exposed only once, and this is a greater than additive effect. Short-term measurements of p53 stabilization, induction of p21/Cdkn1a and of apoptosis also identify these interactive effects. We also demonstrate similar interactive effects of radiation with the mutagenic chemical methyl-nitrosourea and with a nonspecific pro-inflammatory agent, lipopolysaccharide. The magnitude of the interactive effects is greater in cells taken from mice first exposed as juveniles compared to adults. These data indicate that short-term measurements of DNA damage and response to damage are useful for the identification of interactions between ionizing radiation and other agents.

Statistics of hematologic malignancies in Korea: incidence, prevalence and survival rates from 1999 to 2008

Background

The nationwide statistical analysis of hematologic malignancies in Korea has not been reported yet.

Methods

The Korea Central Cancer Registry and the Korean Society of Hematology jointly investigated domestic incidence rates and prevalence of hematologic malignancies occurred between 1999 and 2008, and analyzed survival rates of patients who were diagnosed between 1993 and 2008. Data of hematologic malignancies from 1993 to 2008 were obtained from the Korean National Cancer Incidence Data base. The crude incidence rates, age-specific incidence rates, age-standardized incidence rates, annual percentage change of incidence, and prevalence from 1999-2008 were calculated. Survival rates for patients diagnosed in 1993-2008 were estimated.

Results

In 2008, a total of 8,006 cases of hematologic malignancies were occurred, which comprised 4.5% of all malignancies. In all genders, non-Hodgkin lymphoma, myeloid leukemia, and multiple myeloma were most frequent diseases. In terms of age, ages between 60 and 69 were most prevalent. From 1999 to 2008, the age-standardized incidence rates increased from 10.2 to 13.7, and the annual percentage change was 3.9%. The 5-year survival rate increased from 38.2% during 1993-1995 to 55.2% during 2004-2008. As of January 2009, number of patients with 10-year prevalence was 33,130, and with 5- to 10-year prevalence was 10,515.

Conclusion

This is the first nationwide statistical report of hematologic malignancies in Korea. It could be used as the basic information to help investigate epidemiologic characteristics, evaluate progress during the past years, and establish future strategies for hematologic malignancies. Periodic statistical analysis of hematologic malignancies in Korea should be continued.

Does electric light stimulate cancer development in children?

Incidence of cancer in children has increased in recent decades, and known risk factors can account for only a small minority of cases. Gestation and early childhood are particularly vulnerable periods in human development and an important aspect of development is in circadian rhythmicity. Emerging evidence implicates the molecular circadian mechanism in a vast array of other physiologic functions including metabolism, DNA damage response and cell-cycle regulation. Electric light exposure at night can disrupt circadian rhythms and, thereby, many other physiologic processes that are under circadian control. On this basis, it is proposed that ill-timed electric light exposure to pregnant women, to neonates, infants, and small children may increase cancer risk in those children. There are practical implications and interventions that accrue from this idea should it later be confirmed to be true.

Current understanding of the mechanism of benzene-induced leukemia in humans: implications for risk assessment

Benzene causes acute myeloid leukemia and probably other hematological malignancies. As benzene also causes hematotoxicity even in workers exposed to levels below the US permissible occupational exposure limit of 1 part per million, further assessment of the health risks associated with its exposure, particularly at low levels, is needed. Here, we describe the probable mechanism by which benzene induces leukemia involving the targeting of critical genes and pathways through the induction of genetic, chromosomal or epigenetic abnormalities and genomic instability, in a hematopoietic stem cell (HSC); stromal cell dysregulation; apoptosis of HSCs and stromal cells and altered proliferation and differentiation of HSCs. These effects modulated by benzene-induced oxidative stress, aryl hydrocarbon receptor dysregulation and reduced immunosurveillance, lead to the generation of leukemic stem cells and subsequent clonal evolution to leukemia. A mode of action (MOA) approach to the risk assessment of benzene was recently proposed. This approach is limited, however, by the challenges of defining a simple stochastic MOA of benzene-induced leukemogenesis and of identifying relevant and quantifiable parameters associated with potential key events. An alternative risk assessment approach is the application of toxicogenomics and systems biology in human populations, animals and in vitro models of the HSC stem cell niche, exposed to a range of levels of benzene. These approaches will inform our understanding of the mechanisms of benzene toxicity and identify additional biomarkers of exposure, early effect and susceptibility useful for risk assessment.

Incidence of Epstein-Barr virus in pediatric leukemia in the Sudan

BACKGROUND

Results of several studies have suggested a probable etiologic association between Epstein-Barr virus (EBV) and leukemias; therefore, the aim of this study was to investigate the association of EBV in childhood leukemia.

METHODS

A direct isothermal amplification method was developed for detection of the latent membrane protein 1 (LMP1) of EBV in the peripheral blood of 80 patients with leukemia (54 had lymphoid leukemia and 26 had myeloid leukemia) and of 20 hematologically healthy control subjects.

RESULTS

EBV LMP1 gene transcripts were found in 29 (36.3%) of the 80 patients with leukemia but in none of the healthy controls (P < .0001). Of the 29 EBV(+) cases, 23 (79.3%), 5 (17.3%), and 1 (3.4%) were acute lymphoblastic leukemia, acute myeloid leukemia, and chronic myeloid leukemia, respectively.

CONCLUSION

EBV LMP1 gene transcriptional activity was observed in a significant proportion of patients with acute lymphoblastic leukemia. EBV infection in patients with lymphoid leukemia may be a factor involved in the high incidence of pediatric leukemia in the Sudan.

Environmental radon exposure and childhood leukemia

Despite the fact that animal and human epidemiological studies confirmed a link between radon exposure in homes and increased risk of lung cancer in general population, other types of cancers induced by radon, such as leukemia, have not been consistently demonstrated. The aim of this review was to summarize data published thus far from ecological and case-control studies in exposed populations, taking into account radon dose estimation and evidence of radon-induced genotoxicity, in an effort to clarify the correlation between home radon exposure and incidence of childhood leukemia. Among 12 ecological studies, 11 reported a positive association between radon levels and elevated frequency of childhood leukemia, with 8 being significant. In conjunction with ecological studies, several case-control studies on indoor radon exposure and childhood leukemia were examined, and most investigations indicated a weak association with only a few showing significance. A major source of uncertainty in radon risk assessment is radon dose estimate. Methods for radon exposure measurement in homes of children are one of the factors that affect the risk estimates in a case-control study. The effects of radon-induced genetic damage were studied both in vitro and in vivo using genetic endpoints including chromosomal aberration (CA), micronuclei (MN) formation, gene mutation, and deletions and insertions. By applying a meta-analysis, an increased risk of childhood leukemia induced by indoor radon exposure was noted for overall leukemia and for acute lymphoblastic leukemia (ALL). Data thus indicated an association between environmental radon exposure and elevated leukemia incidence, but more evidence is required in both human investigations and animal mechanistic research before this assumption may be confirmed with certainty.

[The Fetal Tobacco Syndrome - A statement of the Austrian Societies for General- and Family Medicine (ÖGAM), Gynecology and Obstetrics (ÖGGG), Hygiene, Microbiology and Preventive Medicine (ÖGHMP), Pediatrics and Adolescence Medicine (ÖGKJ) as well as Pneumology (ÖGP)]

Over more than 50 years, the nocuous effects of smoking in pregnancy on the fetus are well known. In the first years of science the focus was primarily on restricted fetal growth while in more recent years over 10.000 studies investigated the incomparably big sum of detrimental effects for the unborn's health. In this statement we want to present the recent scientific findings on this topic. The statement is aimed to show all doctors who treat pregnant women the present situation and evidence. In the beginning we give a short overview about the epidemiological situation in Europe. Then we present step by step the health effects with regards to pathophysiology and clinics. Furthermore the reader will learn about possibilities for smoking cessation in pregnancy. The problem of passive-smoking in pregnancy will be dealt with in a separate chapter. At present there is strong evidence that pregnant smoking has a detrimental effect on birth-weight, placenta-associated disease, stillbirth, sudden infant death syndrome (SIDS), childhood overweight, clefts, lung function, asthma, cardiovascular diseases and mental developmental disorders. These factors can be summarized by the term Fetal Tobacco Syndrome. There is supply for more studies for less investigated health effects. Pregnancy is a chance to stop smoking as most women show a high motivation in this period. Hence doctors of all disciplines should inform pregnant women about the detrimental effects of smoking on their unborn child and show them possibilities for smoking cessation.

Association of genetic variations in mTOR with risk of childhood acute lymphoblastic leukemia in a Chinese population

The mammalian target of rapamycin (mTOR) is an important protein kinase regulating cell survival and apoptosis. To determine whether genetic variations in mTOR are associated with risk of acute lymphoblastic leukemia (ALL) in Chinese children, we genotyped two tag single nucleotide poymorphisms (SNPs) in mTOR (rs2536 and rs2295080) in a case-control study. We observed that the variant genotype TC of mTOR rs2536 was associated with a significantly decreased risk of childhood ALL (adjusted odds ratio [OR] = 0.67, 95% confidence interval [CI] = 0.46-0.96), and the association was more pronounced in high-risk ALL and T-phenotype ALL groups. Additionally, we found that the combined genotypes TC/CC decreased the risk of ALL only in the high-risk ALL group (adjusted OR = 0.54, 95% CI = 0.32-0.91) and T-phenotype ALL group (adjusted OR = 0.29, 95% CI = 0.10-0.84). These results suggest that the mTOR rs2536 polymorphism is involved in the susceptibility to childhood ALL in a Chinese population.

Maternal prenatal cigarette, alcohol and illicit drug use and risk of infant leukaemia: a report from the Children's Oncology Group

Several case-control studies have evaluated associations between maternal smoking, alcohol consumption and illicit drug use during pregnancy and risk of childhood leukaemia. Few studies have specifically focused on infants (<1 year) with leukaemia, a group that is biologically and clinically distinct from older children. We present data from a Children's Oncology Group case-control study of 443 infants diagnosed with acute leukaemia [including acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML)] between 1996 and 2006 and 324 population controls. Mothers were queried about their cigarette, alcohol and illicit drug use 1 year before and throughout pregnancy. Odds ratios (ORs) and 95% confidence intervals [CI] were calculated using adjusted unconditional logistic regression models. Maternal smoking (>1 cigarette/day) and illicit drug use (any amount) before and/or during pregnancy were not significantly associated with infant leukaemia. Alcohol use (>1 drink/week) during pregnancy was inversely associated with infant leukaemia overall [OR = 0.64; 95% CI 0.43, 0.94], AML [OR = 0.49; 95% CI 0.28, 0.87], and leukaemia with mixed lineage leukaemia gene rearrangements ('MLL+') [OR = 0.59; 95% CI 0.36, 0.97]. While our results agree with the fairly consistent evidence that maternal cigarette smoking is not associated with childhood leukaemia, the data regarding alcohol and illicit drug use are not consistent with prior reports and are difficult to interpret. It is possible that unhealthy maternal behaviours during pregnancy, some of which carry potential legal consequences, may not be adequately measured using only self-report. Future case-control studies of childhood leukaemia that pursue these exposures may benefit from incorporation of validated instruments and/or biomarkers when feasible.

Benzene, the exposome and future investigations of leukemia etiology

Benzene exposure is associated with acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and probably lymphoma and childhood leukemia. Biological plausibility for a causal role of benzene in these diseases comes from its toxicity to hematopoietic stem cells (HSC) or progenitor cells, from which all leukemias and related disorders arise. The effect of this toxicity is manifest as lowered blood counts (hematotoxicity), even in individuals occupationally exposed to low levels of benzene. Benzene can induce AML/MDS via several well-characterized pathways associated with these diseases. Through its metabolites, benzene induces multiple alterations that likely contribute to the leukemogenic process, and appears to operate via multiple modes of action. To improve mechanistic understanding and for risk assessment purposes, it may be possible to measure several of the key events in these modes of action in an in vitro model of the bone marrow stem cell niche. Even though benzene is leukemogenic at relatively low occupational levels of exposure, it seems unlikely that it is a major cause of leukemia in the general population exposed to benzene in the ppb range. Other established non-genetic causes of AML, e.g. smoking, ionizing radiation and cancer chemotherapy, also only explain about 20% of AML incidence, leaving ∼80% unexplained. The question arises as to how to find the causes of the majority of de novo AMLs that remain unexplained. We propose that we should attempt to characterize the 'exposome' of human leukemia by using unbiased laboratory-based methods to find the unknown 'environmental' factors that contribute to leukemia etiology.

Maternal exposure to household chemicals and risk of infant leukemia: a report from the Children's Oncology Group

OBJECTIVE

Utilizing data from the largest study to date, we examined associations between maternal preconception/prenatal exposure to household chemicals and infant acute leukemia.

METHODS

We present data from a Children's Oncology Group case-control study of 443 infants (<1 year of age) diagnosed with acute leukemia [including acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML)] between 1996 and 2006 and 324 population controls. Mothers recalled household chemical use 1 month before and throughout pregnancy. We used unconditional logistic regression adjusted for birth year, maternal age, and race/ethnicity to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

We did not find evidence for an association between infant leukemia and eight of nine chemical categories. However, exposure to petroleum products during pregnancy was associated with AML (OR = 2.54; 95% CI:1.40-4.62) and leukemia without mixed lineage leukemia (MLL) gene rearrangements ("MLL-") (OR = 2.69; 95% CI: 1.47-4.93). No associations were observed for exposure in the month before pregnancy.

CONCLUSIONS

Gestational exposure to petroleum products was associated with infant leukemia, particularly AML, and MLL- cases. Benzene is implicated as a potential carcinogen within this exposure category, but a clear biological mechanism has yet to be elucidated.

Paternal smoking and risk of childhood acute lymphoblastic leukemia: systematic review and meta-analysis

Objective. To investigate the association between paternal smoking and childhood acute lymphoblastic leukemia (ALL). Method. We identified 18 published epidemiologic studies that reported data on both paternal smoking and childhood ALL risk. We performed a meta-analysis and analyzed dose-response relationships on ALL risk for smoking during preconception, during pregnancy, after birth, and ever smoking. Results. The summary odds ratio (OR) of childhood ALL associated with paternal smoking was 1.11 (95% Confidence Interval (CI): 1.05-1.18, I(2) = 18%) during any time period, 1.25 (95% CI: 1.08-1.46, I(2) = 53%) preconception; 1.24 (95% CI: 1.07-1.43, I(2) = 54%) during pregnancy, and 1.24 (95% CI: 0.96-1.60, I(2) = 64%) after birth, with a dose-response relationship between childhood ALL and paternal smoking preconception or after birth. Conclusion. The evidence supports a positive association between childhood ALL and paternal ever smoking and at each exposure time period examined. Future epidemiologic studies should assess paternal smoking during well-defined exposure windows and should include biomarkers to assess smoking exposure and toxicological mechanisms.

Acute hepatitis A induction of precursor B-cell acute lymphoblastic leukemia: a causal relationship?

Background

Precursor B-cell acute lymphoblastic leukemia accounts for 2% of all lymphoid neoplasms in the United States and occurs most frequently in childhood, but can also occur in adults with a median age of 39 years. It is more commonly seen in males and in Caucasians.

Case Report

We present a case of a 51-year-old Caucasian female with the development of precursor B-cell acute lymphoblastic leukemia after suffering acute hepatitis A 4 weeks prior to her diagnosis. She presented with malaise for a month without spontaneous bruising/bleeding, infections, or B-symptoms, such as fevers, night sweats, or unintentional weight loss.

Conclusion

Nonspecific viral transformation of bone marrow has been discussed in the literature, but we specifically describe hepatitis A-induced adult-onset precursor B-cell acute lymphoblastic leukemia, which is the first reported case in the literature.

Exposure to sodium tungstate and Respiratory Syncytial Virus results in hematological/immunological disease in C57BL/6J mice

The etiology of childhood leukemia is not known. Strong evidence indicates that precursor B-cell Acute Lymphoblastic Leukemia (Pre-B ALL) is a genetic disease originating in utero. Environmental exposures in two concurrent, childhood leukemia clusters have been profiled and compared with geographically similar control communities. The unique exposures, shared in common by the leukemia clusters, have been modeled in C57BL/6 mice utilizing prenatal exposures. This previous investigation has suggested in utero exposure to sodium tungstate (Na2WO4) may result in hematological/immunological disease through genes associated with viral defense. The working hypothesis is (1) in addition to spontaneously and/or chemically generated genetic lesions forming pre-leukemic clones, in utero exposure to Na2WO4 increases genetic susceptibility to viral influence(s); (2) postnatal exposure to a virus possessing the 1FXXKXFXXA/V9 peptide motif will cause an unnatural immune response encouraging proliferation in the B-cell precursor compartment. This study reports the results of exposing C57BL/6J mice to Na2WO4 in utero via water (15 ppm, ad libetum) and inhalation (mean concentration PM5 3.33 mg/m3) and to Respiratory Syncytial Virus (RSV) within 2 weeks of weaning. Inoculation of C57BL/6J mice with RSV was associated with a neutrophil shift in 56% of 5-month old mice. When the RSV inoculation was combined with Na2WO4-exposure, significant splenomegaly resulted (p=0.0406, 0.0184, 0.0108 for control, Na2WO4-only and RSV-only, respectively) in addition to other hematological pathologies which were not significant. Exposure to Na2WO4 and RSV resulted in hematological/immunological disease, the nature of which is currently inconclusive. Further research is needed to characterize this potential leukemia mouse model.

Residential exposure to pesticides and childhood leukaemia: a systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review of published studies on the association between residential/household/domestic exposure to pesticides and childhood leukaemia, and to provide a quantitative estimate of the risk.

METHODS

Publications in English were searched in MEDLINE (1966-31 December 2009) and from the reference list of identified publications. Extraction of relative risk (RR) estimates was performed independently by 2 authors using predefined inclusion criteria. Meta-rate ratio estimates (mRR) were calculated according to fixed and random-effect models. Separate analyses were conducted after stratification for exposure time windows, residential exposure location, biocide category and type of leukaemia.

RESULTS

RR estimates were extracted from 13 case-control studies published between 1987 and 2009. Statistically significant associations with childhood leukaemia were observed when combining all studies (mRR: 1.74, 95% CI: 1.37-2.21). Exposure during and after pregnancy was positively associated with childhood leukaemia, with the strongest risk for exposure during pregnancy (mRR: 2.19, 95% CI: 1.92-2.50). Other stratifications showed the greatest risk estimates for indoor exposure (mRR: 1.74, 95% CI: 1.45-2.09), for exposure to insecticides (mRR: 1.73, 95% CI: 1.33-2.26) as well as for acute non-lymphocytic leukaemia (ANLL) (mRR: 2.30, 95% CI: 1.53-3.45). Outdoor exposure and exposure of children to herbicides (after pregnancy) were not significantly associated with childhood leukaemia (mRR: 1.21, 95% CI: 0.97-1.52; mRR: 1.16, 95% CI: 0.76-1.76, respectively).

CONCLUSIONS

Our findings support the assumption that residential pesticide exposure may be a contributing risk factor for childhood leukaemia but available data were too scarce for causality ascertainment. It may be opportune to consider preventive actions, including educational measures, to decrease the use of pesticides for residential purposes and particularly the use of indoor insecticides during pregnancy.