Childhood cancer and parental use of tobacco: deaths from 1953 to 1955

Risk factors for childhood brain tumours: A systematic review and meta-analysis of observational studies from 1976 to 2022

BACKGROUND

Childhood brain tumours (CBTs) are the leading cause of cancer death in children under the age of 20 years globally. Though the aetiology of CBT remains poorly understood, it is thought to be multifactorial. We aimed to synthesize potential risk factors for CBT to inform primary prevention.

METHODS

We conducted a systematic review and meta-analysis of epidemiological studies indexed in the PubMed, Web of Science, and Embase databases from the start of those resources through 27 July 2023. We included data from case-control or cohort studies that reported effect estimates for each risk factor around the time of conception, during pregnancy and/or during post-natal period. Random effects meta-analysis was used to estimate summary effect sizes (ES) and 95% confidence intervals (CIs). We also quantified heterogeneity (I2) across studies.

FINDINGS

A total of 4040 studies were identified, of which 181 studies (85 case-control and 96 cohort studies) met our criteria for inclusion. Of all eligible studies, 50% (n = 91) were conducted in Europe, 32% (n = 57) in North America, 9% (n = 16) in Australia, 8% (n = 15) in Asia, 1% (n = 2) in South America, and none in Africa. We found associations for some modifiable risk factors including childhood domestic exposures to insecticides (ES 1.44, 95% CI 1.20-1.73) and herbicides (ES 2.38, 95% CI 1.31-4.33). Maternal domestic exposure to insecticides (ES 1.45, 95% CI 1.09-1.94), maternal consumption of cured meat (ES 1.51, 95% CI 1.05-2.17) and coffee ≥ 2 cups/day (ES 1.45, 95% 95% CI 1.07-1.95) during pregnancy, and maternal exposure to benzene (ES 2.22; 95% CI 1.01-4.88) before conception were associated with CBTs in case-control studies. Also, paternal occupational exposure to pesticides (ES 1.48, 95% CI 1.23-1.77) and benzene (ES 1.74, 95% CI 1.10-2.76) before conception and during pregnancy were associated in case-control studies and in combined analysis. On the other hand, assisted reproductive technology (ART) (ES 1.32, 95% CI 1.05-1.67), caesarean section (CS) (ES 1.12, 95% CI 1.01-1.25), paternal occupational exposure to paint before conception (ES 1.56, 95% CI 1.02-2.40) and maternal smoking > 10 cigarettes per day during pregnancy (ES 1.18, 95% CI 1.00-1.40) were associated with CBT in cohort studies. Maternal intake of vitamins and folic acid during pregnancy was inversely associated in cohort studies. Hormonal/infertility treatment, breastfeeding, child day-care attendance, maternal exposure to electric heated waterbed, tea and alcohol consumption during pregnancy were among those not associated with CBT in both case-control and cohort studies.

CONCLUSION

Our results should be interpreted with caution, especially as most associations between risk factors and CBT were discordant between cohort and case-control studies. At present, it is premature for any CBT to define specific primary prevention guidelines.

Effect of Microfluidic Sperm Separation vs. Standard Sperm Washing Processes on Laboratory Outcomes and Clinical Pregnancy Rates in an Unselected Patient Population

A prospective, multicenter, randomized, sibling oocyte study was conducted with 86 couples to evaluate if a microfluidic sperm separation device improved ICSI sperm selection and subsequent cycle outcomes of fertilization, blastocyst utilization, ploidy, and clinical pregnancy rate when applied to a general patient population. Patients with at least 10 metaphase II oocytes were enrolled in the study and sibling oocyte groups were split in half. One half of the oocytes underwent ICSI with the control processed sperm and the other half were injected with sperm sorted by the ZyMōt microfluidic sperm separation device. Fertilization rate was recorded and resulting blastocysts were biopsied and evaluated for ploidy status with NGS. Euploid, non-mosaic embryos were randomly selected for single embryo transfer. A total of 787 oocytes were evaluated in the ZyMōt group and 777 in the control group. No statistical differences were observed between ZyMōt and control processing methods in any of the study outcomes evaluated. It is possible that the selection of normal, progressive sperm for ICSI, and the repair capacity of oocytes are sufficient to promote normal embryonic development in the general infertility population.

The effect of paternal factors on perinatal and paediatric outcomes: a systematic review and meta-analysis

BACKGROUND

Maternal factors, including increasing childbearing age and various life-style factors, are associated with poorer short- and long-term outcomes for children, whereas knowledge of paternal parameters is limited. Recently, increasing paternal age has been associated with adverse obstetric outcomes, birth defects, autism spectrum disorders and schizophrenia in children.

OBJECTIVE AND RATIONALE

The aim of this systematic review is to describe the influence of paternal factors on adverse short- and long-term child outcomes.

SEARCH METHODS

PubMed, Embase and Cochrane databases up to January 2017 were searched. Paternal factors examined included paternal age and life-style factors such as body mass index (BMI), adiposity and cigarette smoking. The outcome variables assessed were short-term outcomes such as preterm birth, low birth weight, small for gestational age (SGA), stillbirth, birth defects and chromosomal anomalies. Long-term outcome variables included mortality, cancers, psychiatric diseases/disorders and metabolic diseases. The systematic review follows PRISMA guidelines. Relevant meta-analyses were performed.

OUTCOMES

The search included 14 371 articles out of which 238 met the inclusion criteria, and 81 were included in quantitative synthesis (meta-analyses). Paternal age and paternal life-style factors have an association with adverse outcome in offspring. This is particularly evident for psychiatric disorders such as autism, autism spectrum disorders and schizophrenia, but an association is also found with stillbirth, any birth defects, orofacial clefts and trisomy 21. Paternal height, but not BMI, is associated with birth weight in offspring while paternal BMI is associated with BMI, weight and/or body fat in childhood. Paternal smoking is found to be associated with an increase in SGA, birth defects such as congenital heart defects, and orofacial clefts, cancers, brain tumours and acute lymphoblastic leukaemia. These associations are significant although moderate in size, with most pooled estimates between 1.05 and 1.5, and none exceeding 2.0.

WIDER IMPLICATIONS

Although the increased risks of adverse outcome in offspring associated with paternal factors and identified in this report represent serious health effects, the magnitude of these effects seems modest.

Childhood cancer research in Oxford I: the Oxford Survey of Childhood Cancers

BACKGROUND

Significant research on the epidemiology and natural history of childhood cancer took place in the Universities of Oxford and Birmingham over sixty years. This is the first of three papers recording this work and describes the Oxford Survey of Childhood Cancers (OSCC), the largest case-control survey of childhood cancer ever undertaken.

METHODS

The OSCC studied deaths in Britain from 1953 to 1981. Parents were interviewed and medical records from ante-natal clinics and treatment centres were followed up and abstracted. The survey left Oxford in 1975 and was run subsequently from Birmingham. The data are now being documented and archived to make them available for future study.

RESULTS

Many papers have resulted from this survey, most notably those relating to the association first reported therein between childhood cancer and ante-natal X-raying. This paper is a historical review of the OSCC.

CONCLUSIONS

In spite of many analyses of the study, this historic data set has continuing value because of the large number of examples of some very rare tumours and the detailed clinical and family history data that are available; and also because of the possibility of carrying out new analyses to investigate emerging research issues.

Parental Tobacco Smoking and Acute Myeloid Leukemia: The Childhood Leukemia International Consortium

The association between tobacco smoke and acute myeloid leukemia (AML) is well established in adults but not in children. Individual-level data on parental cigarette smoking were obtained from 12 case-control studies from the Childhood Leukemia International Consortium (CLIC, 1974-2012), including 1,330 AML cases diagnosed at age <15 years and 13,169 controls. We conducted pooled analyses of CLIC studies, as well as meta-analyses of CLIC and non-CLIC studies. Overall, maternal smoking before, during, or after pregnancy was not associated with childhood AML; there was a suggestion, however, that smoking during pregnancy was associated with an increased risk in Hispanics (odds ratio = 2.08, 95% confidence interval (CI): 1.20, 3.61) but not in other ethnic groups. By contrast, the odds ratios for paternal lifetime smoking were 1.34 (95% CI: 1.11, 1.62) and 1.18 (95% CI: 0.92, 1.51) in pooled and meta-analyses, respectively. Overall, increased risks from 1.2- to 1.3-fold were observed for pre- and postnatal smoking (P < 0.05), with higher risks reported for heavy smokers. Associations with paternal smoking varied by histological type. Our analyses suggest an association between paternal smoking and childhood AML. The association with maternal smoking appears limited to Hispanic children, raising questions about ethnic differences in tobacco-related exposures and biological mechanisms, as well as study-specific biases.

Reported associations between asthma and acute lymphoblastic leukemia: insights from a hybrid simulation study

Numerous studies have reported a protective association between asthma and acute lymphoblastic leukemia (ALL), but the causal structure of this association remains unclear. We present a hybrid simulation to examine the compatibility of this association with uncontrolled confounding by infection or another unmeasured factor. We generated a synthetic cohort using inputs on the interrelations of asthma, ALL, infections, and other suggested risk factors from the literature and the Danish National Birth Cohort. We computed odds ratios (ORs) between asthma and ALL in the synthetic cohort with and without adjustment for infections and other (including unmeasured) confounders. Only if infection was an extremely strong risk factor for asthma (OR of 10) and an extremely strong protective factor against ALL (OR of 0.1) was the asthma-ALL association compatible with the literature (OR of 0.78). Similarly, strong uncontrolled confounding by an unmeasured factor could downwardly bias the asthma-ALL association, but not enough to replicate findings in the literature. This investigation illustrates that the reported protective association between asthma and ALL is unlikely to be entirely due to uncontrolled confounding by infections or an unmeasured confounder alone. Simulation can be used to advance our understanding of risk factors for rare outcomes as demonstrated by this study.

Maternal benzene exposure during pregnancy and risk of childhood acute lymphoblastic leukemia: a meta-analysis of epidemiologic studies

Background

The prevalence of childhood leukemia is increasing rapidly all over the world. However, studies on maternal benzene exposure during pregnancy and childhood acute lymphoblastic leukemia (ALL) have not been systematically assessed. Therefore, we performed a meta-analysis to investigate the association between maternal solvent, paint, petroleum exposure, and smoking during pregnancy and risk of childhood ALL.

Methods

Relevant studies up to September 1^st, 2013 were identified by searching the PubMed, EMBASE, Cochrane library and the Web of Science databases. The effects were pooled using either fixed or random effect models based on the heterogeneity of the studies.

Results

Twenty-eight case-control studies and one cohort study were included for analysis, with a total of 16,695 cases and 1,472,786 controls involved. Pooled odds ratio (OR) with 95% confidence interval (CI) for ALL was 1.25 (1.09, 1.45) for solvent, 1.23 (1.02, 1.47) for paint, 1.42 (1.10, 1.84) for petroleum exposure, and 0.99 (0.93, 1.06) for maternal smoking during pregnancy. No publication bias was found in this meta-analysis and consistent results were observed for subgroup and sensitivity analyses.

Conclusions

Childhood ALL was associated with maternal solvent, paint, and petroleum exposure during pregnancy. No association was found between ALL and maternal smoking during pregnancy. Avoidance of maternal occupational and environmental benzene exposure during pregnancy could contribute to a decrease in the risk of childhood ALL.

Maternal and perinatal risk factors for childhood cancer: record linkage study

OBJECTIVE

To investigate maternal and perinatal risk factors for childhood cancer.

STUDY DESIGN

Case-control analysis of linked records from the Aberdeen Maternity and Neonatal Databank with the Scottish Cancer Registry and the General Registry of Births and Deaths in Scotland was carried out.

SETTING

Aberdeen, Scotland.

PARTICIPANTS

Cases (n=176) comprised children diagnosed with cancer under 15 years or recorded as having died of cancer. Four controls per case were matched by age and gender.

RISK FACTORS TESTED

Maternal age, body mass index, social class, marital status and smoking as well as pre-eclampsia, antepartum haemorrhage and previous miscarriage, gestational age, birth weight and Apgar scores were compared between groups to test for association with cancer. ORs with 95% CIs were calculated using conditional logistic regression in univariable and multivariable models.

RESULTS

Of the maternal characteristics tested, mother's age at delivery (cases mean 28.9 (SD 5.6) years vs controls mean 30.2 (SD 4.6), p=0.002) and smoking status (38.6% smokers among cases, 29.7% among controls, p=0.034) were found to be different between groups. Of the perinatal factors tested, low Apgar score at 5 min (adjusted OR (AOR) 4.59, 95% CI 1.52 to 13.87) and delivery by caesarean section (AOR 1.95, 95% CI 1.30 to 2.92) showed statistically significant associations with childhood cancer in the multivariable model.

CONCLUSIONS

Younger maternal age, maternal smoking, delivery by caesarean section and low Apgar score at 5 min were independently associated with increased risk of childhood cancer. These general findings should be interpreted with caution as this study did not have the power to detect any association with individual diagnostic categories of childhood cancer.

Male-mediated developmental toxicity

Male-mediated developmental toxicity has been of concern for many years. The public became aware of male-mediated developmental toxicity in the early 1990s when it was reported that men working at Sellafield might be causing leukemia in their children. Human and animal studies have contributed to our current understanding of male-mediated effects. Animal studies in the 1980s and 1990s suggested that genetic damage after radiation and chemical exposure might be transmitted to offspring. With the increasing understanding that there is histone retention and modification, protamine incorporation into the chromatin and DNA methylation in mature sperm and that spermatozoal RNA transcripts can play important roles in the epigenetic state of sperm, heritable studies began to be viewed differently. Recent reports using molecular approaches have demonstrated that DNA damage can be transmitted to babies from smoking fathers, and expanded simple tandem repeats minisatellite mutations were found in the germline of fathers who were exposed to radiation from the Chernobyl nuclear power plant disaster. In epidemiological studies, it is possible to clarify whether damage is transmitted to the sons after exposure of the fathers. Paternally transmitted damage to the offspring is now recognized as a complex issue with genetic as well as epigenetic components.

Parental smoking and risk of childhood brain tumors by functional polymorphisms in polycyclic aromatic hydrocarbon metabolism genes

BACKGROUND

A recent meta-analysis suggested an association between exposure to paternal smoking during pregnancy and childhood brain tumor risk, but no studies have evaluated whether this association differs by polymorphisms in genes that metabolize tobacco-smoke chemicals.

METHODS

We assessed 9 functional polymorphisms in 6 genes that affect the metabolism of polycyclic aromatic hydrocarbons (PAH) to evaluate potential interactions with parental smoking during pregnancy in a population-based case-control study of childhood brain tumors. Cases (N = 202) were ≤10 years old, diagnosed from 1984-1991 and identified in three Surveillance, Epidemiology, and End Results (SEER) registries in the western U.S. Controls in the same regions (N = 286) were frequency matched by age, sex, and study center. DNA for genotyping was obtained from archived newborn dried blood spots.

RESULTS

We found positive interaction odds ratios (ORs) for both maternal and paternal smoking during pregnancy, EPHX1 H139R, and childhood brain tumors (P(interaction) = 0.02; 0.10), such that children with the high-risk (greater PAH activation) genotype were at a higher risk of brain tumors relative to children with the low-risk genotype when exposed to tobacco smoke during pregnancy. A dose-response pattern for paternal smoking was observed among children with the EPHX1 H139R high-risk genotype only (OR(no exposure) = 1.0; OR(≤3 hours/day) = 1.32, 95% CI: 0.52-3.34; OR(>3 hours/day )= 3.18, 95% CI: 0.92-11.0; P(trend )= 0.07).

CONCLUSION

Parental smoking during pregnancy may be a risk factor for childhood brain tumors among genetically susceptible children who more rapidly activate PAH in tobacco smoke.

Epidemiology of childhood acute myeloid leukemia

Although leukemia is the most common childhood cancer diagnosis, the subtype, acute myeloid leukemia (AML), is less common and fewer etiologic studies exist. This review summarizes the major risk factors for AML. We searched the literature using PubMed for articles on childhood AML and reviewed 180 articles. While few risk factors are definitive, we identified several with consistent evidence of a possible effect. Thorough analysis of genetic and epigenetic factors is missing from this literature and methodological issues are unresolved. Future studies should more closely examine causal mechanisms, improve exposure measurement, and include analysis using genetic and epigenetic factors.

Effects of β-glucan polysaccharide revealed by the dominant lethal assay and micronucleus assays, and reproductive performance of male mice exposed to cyclophosphamide

β-glucan is a well-known polysaccharide for its chemopreventive effect. This study aimed to evaluate the chemopreventive ability of β-glucan in somatic and germ cells through the dominant lethal and micronucleus assays, and its influence on the reproductive performance of male mice exposed to cyclophosphamide. The results indicate that β-glucan is capable of preventing changes in DNA in both germ cells and somatic ones. Changes in germ cells were evaluated by the dominant lethal assay and showed damage reduction percentages of 46.46% and 43.79% for the doses of 100 and 150 mg/kg. For the somatic changes, evaluated by micronucleus assay in peripheral blood cells in the first week of treatment, damage reduction percentages from 80.63–116.32% were found. In the fifth and sixth weeks, the percentage ranged from 10.20–52.54% and −0.95–62.35%, respectively. Besides the chemopreventive efficiency it appears that the β-glucan, when combined with cyclophosphamide, is able to improve the reproductive performance of males verified by the significant reduction in rates of post-implantation losses and reabsorption in the mating of nulliparous females with males treated with cyclophosphamide.

Maternal smoking during pregnancy and risk for childhood leukemia: a nationwide case-control study in Greece and meta-analysis

BACKGROUND

Maternal smoking during pregnancy has been often implicated in the development of childhood leukemia with ambiguous results. Hence, we conducted a meta-analysis aiming to summarize current evidence and quantify any tentative impact.

PROCEDURE

We retrieved one cohort (553 leukemias compared to 1,440,542 children), 20 case-control studies and also analyzed the updated Greek case-control dataset with unpublished data, yielding in total 11,092 cases and 25,221 controls.

RESULTS

Odds ratios reported in the studies included ranged from 0.70 to 2.20 for acute lymphocytic (ALL) and from 0.60 to 2.17 for acute myelocytic leukemia (AML). The combined effect regarding the association of maternal smoking (any vs. no) and leukemia risk was 1.03 for ALL (95% CI = 0.95-1.12, random effects model) and 0.99 for AML (95% CI = 0.90-1.09, fixed effects model). The results remained unchanged when sensitivity analyses were undertaken of studies reporting same maternal smoking periods, those focusing only on childhood leukemia deaths or investigations which did not clearly define AML subtype.

CONCLUSIONS

The findings of the meta-analysis challenge the limits of traditional epidemiology to provide sound inferences when point estimates of constituent studies range around the null. In particular, this study provides no support to a hypothesis linking maternal smoking during pregnancy with subsequent development of main childhood leukemia subtypes. Further investigations employing molecular and genetic epidemiology, however, might be needed in the hope to reveal even minimal risks pertaining individuals with specific susceptibility to tobacco compounds who sustain high environmental exposures prenatally or postnatally.

Could zinc prevent reproductive alterations caused by cigarette smoke in male rats?

The aim of the present study was to evaluate the effects of zinc on fertility through semen parameters, testosterone level and oxidative DNA damage to spermatozoa of rats exposed to cigarette smoke. Male Wistar rats (60 days old) were divided into four groups (n = 10 per group): control, cigarette-smoking (20 cigarettes per day), zinc (zinc chloride 20 mg kg–1 day–1) and zinc plus cigarette-smoking (zinc chloride 20 mg kg–1 day–1; 20 cigarettes per day). The treatment was applied for nine weeks and the following parameters were analysed: bodyweight, wet weights of the reproductive organs and the adrenal gland, plasma testosterone concentration, testicular function (seminal analysis and daily sperm production) and sperm DNA oxidative damage. The exposure to cigarette smoke decreased testosterone concentration, the percentage of normal morphology and the motility of spermatozoa. In addition, this exposure increased sperm DNA oxidative damage. Zinc treatment protected against the toxic damage that smoking caused to spermatozoa. This study showed a correlation between smoking and possible male infertility and subfertility, and also that the majority of smoking-induced changes in spermatozoa were prevented by zinc treatment. In conclusion, zinc, an antioxidant and stimulant of cell division, can be indicated as a promising treatment in men with infertility caused by the toxic components of cigarette smoke.

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.

Maternal smoking during pregnancy and childhood lymphoma: a meta-analysis

Results from epidemiological studies exploring the association between childhood lymphoma and maternal smoking during pregnancy have been contradictory. This meta-analysis included all published cohort (n = 2) and case-control (n = 10) articles; among the latter, the data of the Greek Nationwide Registry for Childhood Hematological Malignancies study were updated to include all recently available cases (-2008). Odds ratios (ORs), relative risks and hazard ratios were appropriately pooled in three separate analyses concerning non-Hodgkin lymphoma (NHL, n = 1,072 cases), Hodgkin lymphoma (HL, n = 538 cases) and any lymphoma (n = 1,591 cases), according to data availability in the included studies. An additional metaregression analysis was conducted to explore dose-response relationships. A statistically significant association between maternal smoking (any vs. no) during pregnancy and risk for childhood NHL was observed (OR = 1.22, 95% confidence interval, CI: 1.03-1.45, fixed effects model), whereas the risk for childhood HL was not statistically significant (OR = 0.90, 95% CI: 0.66-1.21, fixed effects model). The analysis on any lymphoma did not reach statistical significance (OR = 1.10, 95% CI = 0.96-1.27, fixed effects model), possibly because of the case-mix of NHL to HL. No dose-response association was revealed in the metaregression analysis. In conclusion, this meta-analysis points to a modest increase in the risk for childhood NHL, but not HL, among children born by mothers smoking during pregnancy. Further investigation of dose-response phenomena in the NHL association, however, warrants accumulation of additional data.

Gene-environment interaction and male reproductive function

As genetic factors can hardly explain the changes taking place during short time spans, environmental and lifestyle-related factors have been suggested as the causes of time-related deterioration of male reproductive function. However, considering the strong heterogeneity of male fecundity between and within populations, genetic variants might be important determinants of the individual susceptibility to the adverse effects of environment or lifestyle. Although the possible mechanisms of such interplay in relation to the reproductive system are largely unknown, some recent studies have indicated that specific genotypes may confer a larger risk of male reproductive disorders following certain exposures. This paper presents a critical review of animal and human evidence on how genes may modify environmental effects on male reproductive function. Some examples have been found that support this mechanism, but the number of studies is still limited. This type of interaction studies may improve our understanding of normal physiology and help us to identify the risk factors to male reproductive malfunction. We also shortly discuss other aspects of gene-environment interaction specifically associated with the issue of reproduction, namely environmental and lifestyle factors as the cause of sperm DNA damage. It remains to be investigated to what extent such genetic changes, by natural conception or through the use of assisted reproductive techniques, are transmitted to the next generation, thereby causing increased morbidity in the offspring.

Cigarette smoking during pregnancy: chromosome translocations and phenotypic susceptibility in mothers and newborns

The effects of maternal cigarette smoking during pregnancy on structural chromosome aberrations were evaluated in peripheral lymphocytes from 239 mothers and their 241 newborns to determine whether smoking during pregnancy, genetic susceptibility, and race are associated with chromosome aberrations including translocations. Demographic information and cigarette smoking data were obtained via questionnaire. There were 119 Caucasian Americans, 118 African Americans, and 2 Asian Americans. The average maternal age was 24.9+/-5.8 (mean+/-S.D.) years. Thirty-nine percent of the Caucasian Americans and 45.4% of the African Americans self-reported that they were active smokers during the index pregnancy. The average number of cigarettes smoked per day was 2.65+/-5.75 and 1.37+/-3.17 for Caucasian and African American mothers, respectively. Peripheral blood lymphocytes from the mother and from the fetal side of the placenta were evaluated for chromosome aberrations by whole chromosome painting. Aliquots from the same blood samples were also used to assess genetic susceptibility with an in vitro bleomycin challenge assay. Spontaneous translocation frequencies in both maternal and newborn lymphocytes were not associated with cigarette smoking, socioeconomic status, or education. The absence of a smoking effect may be attributable to the low level of cigarette usage in these subjects. The average bleomycin-induced damage in the maternal and newborn populations was 0.37+/-0.27 and 0.15+/-0.14 breaks per cell, respectively, a difference that was highly significant (p<0.0001). In newborns there was a positive association between bleomycin sensitivity and the frequencies of aberrations as measured by chromosome painting: p Collapse

Key Words

• cigarette smoking
• pregnancy
• newborns
• mothers
• chromosome translocations
• genomic susceptibility

Collapse

MESH Headings

• Adolescent
• Adult
• Black or African American
• Chromobacterium
• Female
• Humans
• Infant, Newborn
• Male
• Maternal-Fetal Exchange
• Pregnancy
• Smoking/adverse effects
• Translocation, Genetic/genetics
• White People

Collapse

Grants

• ZIJ BC011218-01 Intramural NIH HHS
• R01 HD33016 NICHD NIH HHS

Collapse

Affiliation(s) Collapse

A review of the potential association between childhood leukemia and benzene

Chronic exposure to high concentrations of benzene is an established cause of acute myeloid leukemia (AML) in occupationally exposed workers. Based on this association, it is not unreasonable to assume that children could also get AML if they were exposed to comparable levels of benzene. Fortunately, reports of such exposures and subsequent AML development in children are non-existent. However, the question of whether children can develop leukemia at far lower, environmental levels of benzene remains. The existing scientific evidence relevant to this question will be addressed in this review. While positive findings have been reported, the collective literature does not indicate that exposure to environmental levels of benzene is related to an increased risk of childhood leukemia. Our understanding of this important issue would be strengthened by additional studies that accurately characterize exposures as well as differentiate between the various forms of leukemias observed in children.

Cigarette smoke extract immobilizes human spermatozoa and induces sperm apoptosis

Cigarette smoking by the male partner adversely affects assisted reproductive techniques, suggesting that it may damage sperm chromatin/DNA and consequently embryo development. The effects of graded concentrations of research cigarettes smoke extract (CSE) on motility, mitochondrial membrane potential (MMP), chromatin integrity and apoptosis were evaluated in spermatozoa obtained from 13 healthy, non-smoking men with normal sperm parameters, by flow cytometry. CSE suppressed sperm motility in a concentration- and time-dependent manner and increased the number of spermatozoa with low MMP, the main source of energy for sperm motility. In addition, CSE had a detrimental effect on sperm chromatin condensation and apoptosis. Indeed, it increased the number of spermatozoa with phosphatidylserine externalization, an early apoptotic sign, and fragmented DNA, a late apoptotic sign, in a concentration- and time-dependent manner. These effects of CSE were of similar or even greater magnitude to those obtained following incubation with tumour necrosis factor-alpha, a cytokine known for its negative impact on sperm function, used as positive control. Since transmission of smoking-induced sperm DNA alterations has been found in pre-implantation embryos, and this may predispose offspring to a greater risk of malformations, cancer and genetic diseases, men seeking to father a child are recommended to give up smoking.

Parental smoking and childhood leukemia

Childhood leukemia is the most common cancer among children, representing 31% of all cancer cases occurring in children younger than the age of 15 years in the USA. There are only few known risk factors of childhood leukemia (sex, age, race, exposure to ionizing radiation, and certain congenital diseases, such as Down syndrome and neurofibromatosis), which account for only 10% of the childhood leukemia cases. Several lines of evidence suggest that childhood leukemia may be more due to environmental rather than genetic factors, although genes may play modifying roles. Human and animal studies showed that the development of childhood leukemia is a two-step process that requires a prenatal initiating event(s) plus a postnatal promoting event(s). Despite a substantial public health effort to reduce cigarette smoking, a large proportion of the US and world population still smoke. Tobacco smoke contains at least 60 known human or animal carcinogens, with the major chemical classes being volatile hydrocarbons, aldehydes, aromatic amines, polycyclic aromatic hydrocarbons, and nitrosamines; among these chemicals, only benzene is an established leukemogen, although other chemicals in the tobacco could interact with one another in a complex way to jointly attain a significant carcinogenic effect on the development of leukemia. Although tobacco smoke is an established risk factor for adult myeloid leukemia, the studies of association between parental smoking and childhood leukemia have produced inconsistent results. The majority of the studies on maternal smoking and childhood leukemia did not find a significant positive association and some even reported an inverse association. In contrast to studies of maternal smoking, studies of paternal smoking and childhood leukemia reported more positive associations but only by less than half of the studies. Future directions to be considered for improving the study of parental smoking and childhood leukemia are: 1) consider all sources of benzene exposure in addition to smoking, including occupational exposure and traffic exhausts; 2) childhood leukemia is a heterogeneous disease and epidemiologic studies of childhood leukemia can be greatly improved by grouping childhood leukemia into more homogeneous groups by molecular techniques (e.g., structural and numerical chromosomal changes); and 3) assess gene-environment interaction. It is hoped that through the continual effort, more will be uncovered regarding the causes of childhood leukemia. In the meantime, more effort should be spent on educating the parents to quit smoking, because parental smoking is known to affect many childhood diseases (e.g., asthma, respiratory tract infection, and otitis media) that are much more prevalent than childhood leukemia.

Childhood hematopoietic malignancies and parental use of tobacco and alcohol: the ESCALE study (SFCE)

OBJECTIVES

Investigating the role of parental smoking and maternal alcohol consumption in the etiology of childhood hematopoietic malignancies.

METHODS

The national registry-based case-control study ESCALE was carried out in France over the period 2003-2004. Population controls were frequency matched with the cases on age and gender. Maternal smoking and alcohol consumption during pregnancy and paternal smoking since before conception were reported by the mothers in a structured telephone questionnaire. Odds ratios (OR) were estimated using unconditional regression models closely adjusted for potential confounders.

RESULTS

A total of 765 cases of acute leukemia (AL), 130 of Hodgkin's lymphoma (HL), 165 of non-Hodgkin's lymphoma (NHL) and 1681 controls were included. Paternal smoking was significantly associated with childhood ALL (OR = 1.4 [1.1-1.7]), AML (OR = 1.5 [1.0-2.3]), Burkitt (OR = 2.0 [1.2-3.2]), and anaplastic large cell (OR = 3.2 [1.2-9.1]) NHL. For the four diseases, the ORs significantly increased with the number of cigarettes smoked. No association with HL or with other types of NHL was observed. The associations with maternal alcohol consumption and cigarette smoking during pregnancy were less consistent.

CONCLUSION

The results support the hypothesis that only paternal smoking, and not maternal alcohol consumption or cigarette smoking, plays a role in childhood hematopoietic malignancies.

Human sperm DNA fragmentation: correlation of TUNEL results as assessed by flow cytometry and optical microscopy

An association between DNA fragmentation in sperm determined by the terminal deoxynucleotidyl transferase [TdT]-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) assay and the incidence of reproductive failure has been reported, either using flow cytometry or optical microscopy. However, the results obtained using each of these two approaches are different. Since there is a relative lack of studies standardizing these two approaches, the direct comparison of the results described in the different articles is difficult at present. To allow the comparison of the TUNEL results obtained using flow cytometry and optical microscopy, we applied these two approaches in a total of 66 human sperm samples. A positive correlation is detected in the TUNEL results as measured by flow cytometry and optical microscopy (Spearman; r = 0.720, P < 0.001). The percentage of TUNEL-positive spermatozoa assessed by flow cytometry is 2.6 times higher than that detected in optical microscopy (39.7% +/- 23.1% versus 15.3% +/- 10.3%). Although there is a good correlation of the TUNEL results obtained by flow cytometry and optical microscopy, the percentages obtained with either technique are different. Therefore, the TUNEL results described in the present work should be valuable to compare the results described in many independent articles, using either optical microscopy or flow cytometry.

Long-term effects of mouse intracytoplasmic sperm injection with DNA-fragmented sperm on health and behavior of adult offspring

Genetic and environmental factors produce different levels of DNA damage in spermatozoa. Usually, DNA-fragmented spermatozoa (DFS) are used with intracytoplasmic sperm injection (ICSI) treatments in human reproduction, and use of DFS is still a matter of concern. The purpose of the present study was to investigate the long-term consequences on development and behavior of mice generated by ICSI with DFS. Using CD1 and B6D2F1 mouse strains, oocytes were injected with fresh spermatozoa or with frozen-thawed spermatozoa without cryoprotector. This treatment increased the percentage of TUNEL-positive spermatozoa, tail length as measured by comet assay, and loss of telomeres as measured by quantitative PCR. The ICSI-generated embryos were cultured for 24 h in KSOM, and 2-cell embryos were transferred into CD1 females. The DFS reduced both the rate of preimplantation embryo development and number of offspring. Immunofluorescence staining with an antibody against 5-methylcytosine showed a delay of 2 h on the active demethylation of male pronucleus in the embryos produced by ICSI. Moreover, ICSI affected gene transcription and methylation of some epigenetically regulated genes like imprinting, X-linked genes, and retrotransposon genes. At 3 and 12 mo of age, ICSI with DFS-produced animals and in vivo-fertilized controls were submitted to behavioral tests: locomotor activity (open field), exploratory/anxiety behavior (elevated plus maze, open field), and spatial memory (free-choice exploration paradigm in Y maze). Females produced by ICSI showed increased anxiety, lack of habituation pattern, deficit in short-term spatial memory, and age-dependent hypolocomotion in the open-field test (P<0.05). Postnatal weight gain of mice produced by ICSI with fresh or frozen sperm was higher than that of their control counterparts from 16 wk on (P<0.01). Anatomopathological analysis of animals at 16 mo of age showed some large organs and an increase in pathologies (33% of CD1 females produced with DFS presented some solid tumors in lungs and dermis of back or neck). Moreover, 20% of the B6D2F1 mice generated with DFS died during the first 5 mo of life, with 25% of the surviving animals showing premature aging symptoms, and 70% of the B6D2F1 mice generated with DFS died earlier than controls with different kind of tumors. We propose that depending on the level of DFS, oocytes may partially repair fragmented DNA, producing blastocysts able to implant and produce live offspring. The incomplete repair, however, may lead to long-term pathologies. Our data indicate that use of DFS in ICSI can generate effects that only emerge during later life, such as aberrant growth, premature aging, abnormal behavior, and mesenchymal tumors.

Prenatal Multivitamin Supplementation and Rates of Pediatric Cancers: A Meta-Analysis

Prenatal supplementation of folic acid has been shown to decrease the risk of several congenital malformations. Several studies have recently suggested a potential protective effect of folic acid on certain pediatric cancers. The protective role of prenatal multivitamins has not been elucidated. We conducted a systematic review and meta-analysis to assess the potential protective effect of prenatal multivitamins on several pediatric cancers. Medline, PubMed, EMBASE, Toxline, Healthstar, and Cochrane databases were searched for studies published in all languages from 1960 to July 2005 on multivitamin supplementation and pediatric cancers. References from all articles collected were reviewed for additional articles. Two blinded independent reviewers assessed the articles for inclusion and exclusion. Rates of cancers in women supplemented with multivitamins were compared with unsupplemented women using a random effects model. Sixty-one articles were identified in the initial search, of which, seven articles met the inclusion criteria. There was an apparent protective effect for leukemia (odds ratio (OR)=0.61, 95% confidence interval (CI)=0.50-0.74), pediatric brain tumors (OR=0.73, 95% CI=0.60-0.88) and neuroblastoma (OR=0.53, 95% CI=0.42-0.68). In conclusion, maternal ingestion of prenatal multivitamins is associated with a decreased risk for pediatric brain tumors, neuroblastoma, and leukemia. Presently, it is not known which constituent(s) among the multivitamins confer this protective effect.

Environmental genotoxicants/carcinogens and childhood cancer: Bridgeable gaps in scientific knowledge

Cancer in children is a major concern in many countries. An important question is whether these childhood cancers are caused by something, or are just tragic random events. Causation of at least some children's cancers is suggested by direct and indirect evidence, including epidemiological data, and animal studies that predict early life sensitivity of humans to carcinogenic effects. Candidate risk factors include genotoxic agents (chemicals and radiation), but also diet/nutrition, and infectious agents/immune responses. With regard to likelihood of risks posed by genotoxicants, there are pros and cons. The biological properties of fetuses and infants are consistent with sensitivity to preneoplastic genotoxic damage. Recent studies of genetic polymorphisms in carcinogen-metabolizing enzymes confirm a role for chemicals. On the other hand, in numerous epidemiological studies, associations between childhood cancers and exposure to genotoxicants, including tobacco smoke, have been weak and hard to reproduce. Possibly, sensitive genetic or ontogenetic subpopulations, and/or co-exposure situations need to be discovered to allow identification of susceptible individuals and their risk factors. Among the critical knowledge gaps needing to be bridged to aid in this effort include detailed tissue and cellular ontogeny of carcinogen metabolism and DNA repair enzymes, and associations of polymorphisms in DNA repair enzymes with childhood cancers. Perinatal bioassays in animals of specific environmental candidates, for example, benzene, could help guide epidemiology. Genetically engineered animal models could be useful for identification of chemical effects on specific genes. Investigations of interactions between factors may be key to understanding risk. Finally, fathers and newborn infants should receive more attention as especially sensitive targets.

Parental smoking and the risk of childhood leukemia

Cigarette smoke has been linked to adult myeloid leukemia; however, the association between parental smoking and childhood leukemia remains unclear. Parental smoking and the risk of childhood leukemia were examined in the Northern California Childhood Leukemia Study, a case-control study, between 1995 and 2002. The present analysis included 327 acute childhood leukemia cases (281 acute lymphoblastic leukemia (ALL) and 46 acute myeloid leukemia (AML)) and 416 controls matched on age, sex, maternal race, and Hispanic ethnicity. Maternal smoking was not associated with an increased risk of either ALL or AML. Paternal preconception smoking was significantly associated with an increased risk of AML (odds ratio = 3.84, 95% confidence interval: 1.04, 14.17); an increased risk for ALL was suggestive for paternal preconception smoking (odds ratio = 1.32, 95% confidence interval: 0.86, 2.04). Greater risks of ALL were observed compared with the risk associated with paternal preconception smoking alone, when paternal preconception smoking was combined with maternal postnatal smoking (p(interaction) = 0.004) or postnatal passive smoking exposure (p(interaction) = 0.004). These results strongly suggest that exposure to paternal preconception smoking alone or in combination with postnatal passive smoking may be important in the risk of childhood leukemia.

Levels of 1-hydroxypyrene and other monohydroxy polycyclic aromatic hydrocarbons in children: A study based on U.S. reference range values

Urine samples collected in 1999 and 2000 as part of the National Health and Nutrition Examination Survey (NHANES) were analyzed for 14 monohydroxy polycyclic aromatic hydrocarbons (PAH, metabolites of 7 PAH compounds) and for the first time reference range values were calculated for these metabolites in the U.S. population. The purpose of this paper is to explore differences in these PAH metabolites between children (6-11 years old), adolescents, and adults. More than 99% of the urine samples contained a detectable amount of 1-hydroxypyrene (1-OHpyrene), a metabolite of pyrene. We found that children in the youngest age group (6-11 years) had a geometric mean level (creatinine corrected data) 30% higher than children and adults in the other age groups, but no statistical differences existed between the two genders and among different racial groups. Smokers and persons exposed to environmental tobacco smoke (ETS) in 12-19-year-old group and the 20-year-and-older group had higher levels of urinary 1-OHpyrene by a factor of 2-3 than non-smokers in the corresponding age group. Measurements of 3-hydroxyphenanthrene also suggested increased levels in children and in smokers. These results may indicate that young children are at a greater risk for PAH exposure, or that they absorb, distribute, metabolize, or eliminate PAH differently than adults.

Maternal coffee and alcohol consumption during pregnancy, parental smoking and risk of childhood acute leukaemia

INTRODUCTION

We investigated the role of maternal alcohol and coffee drinking and parental smoking on the risk of childhood acute leukemia in a multicenter case-control study.

METHODS

The study included 280 incident cases and 288 hospitalized controls, frequency matched with the cases by age, gender and center. Data collection was completed by face-to-face standardized interviews of the case and control mothers.

RESULTS

An association with maternal alcohol consumption during pregnancy was observed with acute lymphoid leukemia (ALL) (OR=2.0 [1.4-3.0]) and acute non-lymphoid leukemia (ANLL) (OR=2.6 [1.2-5.8]). Maternal coffee consumption during pregnancy was associated with childhood acute leukemia, ORs increasing in ALL with coffee consumption (OR=1.1 [0.7-1.8], OR=2.4 [1.3-4.7] and OR=3.1 [1.0-9.5], respectively, for < or =3, 4-8 and >8 cups/day). No association with maternal smoking during pregnancy or parental smoking before or after the index child's birth was observed.

DISCUSSION

Our results suggest an association with maternal alcohol and coffee drinking during pregnancy and call for further investigations. Besides, the present study does not support the hypothesis of an increase in the risk of childhood leukemia related to parental smoking.

Cigarette smoking is related to a decrease in semen volume in a population of fertile men

OBJECTIVE

To evaluate the semen quality and hormonal levels in fertile men according to their level of cigarette smoking.

SUBJECTS AND METHODS

We evaluated 889 fertile men who came for a vasectomy for sterilization purposes. The men included 522 non-smokers, 143 mild smokers (<10 cigarettes/day), 154 moderate smokers (11-20/day), and 70 heavy smokers (>20/day). We evaluated sperm concentration, motility, motion variables and hormonal levels in these men.

RESULTS

There were no significant differences among the groups in sperm concentration or motility, or in levels of follicle-stimulating hormone, luteinizing hormone, or serum total testosterone. Also, sperm motion characteristics did not differ across the groups. Semen volume was the only semen variable which tended to decrease according to the number of cigarettes smoked.

CONCLUSIONS

Cigarette smoking had no apparent effect on sperm concentration, motility or reproductive hormonal levels, but tended to reduce semen volume.

Environmental Tobacco Smoke and Risk of Adult Leukemia

BACKGROUND

The role of environmental tobacco smoke (ETS) in the causation of lung and breast cancer has been repeatedly evaluated over recent years. In contrast, its impact on the risk of adult leukemia has received little attention.

METHODS

We used the lifetime residential and occupational ETS exposure histories from a population-based sample of 1068 incident and histologically confirmed adult leukemia cases and 5039 population controls age 20 to 74 years to evaluate the relationship between ETS exposure and adult leukemia risk among nonsmokers in Canada. The duration of exposure and smoker-years index were used as indices of ETS exposure. We restricted our analysis to the 266 case and 1326 control subjects who reported being lifetime nonsmokers and provided residential ETS exposure history for at least 75% of their lifetime.

RESULTS

No association was found for most leukemia subtypes, and in particular for acute myeloid leukemia. In contrast, the risk for chronic lymphocytic leukemia was clearly associated with ETS exposure, with an adjusted odds ratio of 2.3 (95% confidence interval = 1.2-4.5) for more than 83 smoker-years of residential exposure and 2.4 (1.3-4.3) for more than 72 smoker-years of occupational exposure. There was a dose-response relationship for chronic lymphocytic leukemia with both indices of exposure. Risk was not higher with recent exposure, using time-window-exposure analyses.

CONCLUSIONS

Regular long-term ETS exposure may be a risk factor for chronic lymphocytic leukemia.

DNA damage to spermatozoa has impacts on fertilization and pregnancy

DNA damage in the male germ line has been associated with poor semen quality, low fertilization rates, impaired preimplantation development, increased abortion and an elevated incidence of disease in the offspring, including childhood cancer. The causes of this DNA damage are still uncertain but the major candidates are oxidative stress and aberrant apoptosis. The weight of evidence currently favours the former and, in keeping with this conclusion, positive results have been reported for antioxidant therapy both in vivo and in vitro. Resolving the causes of DNA damage in the male germ line will be essential if we are to prevent the generation of genetically damaged human embryos, particularly in the context of assisted conception therapy.

HPRT gene alterations in umbilical cord blood T-lymphocytes in newborns of mothers exposed to tobacco smoke during pregnancy

Prenatal exposure to tobacco smoke has been associated with an increased risk of pediatric malignancies, yet the transplacental induction of genetic alterations by tobacco smoke carcinogens and their implication to childhood diseases remain poorly understood. We characterized mutations in the HPRT gene in umbilical cord blood T-lymphocytes of self-reported 103 never-smoking mothers and 104 smoking mothers (54 mothers smoked throughout and 50 mothers quit smoking during pregnancy). The results showed the illegitimate V(D)J recombinase-mediated deletion of HPRT exons 2-3 was the most prominent alteration occurring in 48.2% (26/54) of mutants from neonates of the smoking mothers who smoked during pregnancy, compared with 28.0% (14/50) from those of smoking mothers who quit smoking during pregnancy (p=0.035, Fisher's exact test), 34.9% (36/103) from never-smoking mothers (p=0.08), or 32.7% (50/153) of those of neonates born from the latter two groups of mothers combined (p=0.043). There was no significant difference in the frequency of this deletion between neonates of the never-smoking mothers and the smoking mothers who quit smoking during pregnancy (34.9% versus 28.0%, respectively, p=0.39). The results show an increase in illegitimate V(D)J recombinase-mediated deletion of HPRT exons 2-3 in cord blood T-lymphocytes of newborns of mothers who smoked during pregnancy, compared with the group of mothers who did not smoke during pregnancy, implying an increase in illegitimate V(D)J recombinase-mediated alteration, a genetic recombination event associated with childhood malignancies, may be induced in utero during pregnancy by maternal exposure to tobacco smoke-derived genotoxicants.

Nucleotide excision repair activity varies among murine spermatogenic cell types

Germ cells perform a unique and critical biological function: they propagate the DNA that will be used to direct development of the next generation. Genetic integrity of germ cell DNA is essential for producing healthy and reproductively fit offspring, and yet germ cell DNA is damaged by endogenous and exogenous agents. Nucleotide excision repair (NER) is an important mechanism for coping with a variety of DNA lesions. Little is known about NER activity in spermatogenic cells. We expected that germ cells would be more efficient at DNA repair than somatic cells, and that this efficiency may be reduced with age when the prevalence of spontaneous mutations increases. In the present study, NER was measured in defined spermatogenic cell types, including premeiotic cells (A and B type spermatogonia), meiotic cells (pachytene spermatocytes), and postmeiotic haploid cells (round spermatids) and compared with NER in keratinocytes. Global genome repair and transcription-coupled repair subpathways of NER were examined. All spermatogenic cell types from young mice displayed good repair of (6-4) pyrimidone photoproducts, although the repair rate was slower than in primary keratinocytes. In aged mice, repair of 6-4 pyrimidone photoproducts was depressed in postmeiotic cells. While repair of cyclobutane pyrimidine dimers was not detected in spermatogenic cells or in keratinocytes, the transcribed strands of active genes were repaired with greater efficiency than nontranscribed strands or inactive genes in keratinocytes and in meiotic and postmeiotic cells; spermatogonia displayed low to moderate ability to repair cyclobutane pyrimidine dimers on both DNA strands regardless of transcriptional status. Overall, the data suggest cell type-specific NER activity during murine spermatogenesis, and our results have possible implications for germ cell aging.

Causes of childhood leukaemia and lymphoma

Childhood cancer is rare comprising less than 1% of all malignancies diagnosed each year in developed countries. Leukaemia is the commonest form of cancer in children accounting for around a third of all childhood cancer, with acute lymphoblastic leukaemia (ALL) being the most prevalent. Biologically specific subtypes of ALL and acute myeloblastic leukaemia (AML), the other major morphological type of childhood leukaemia, are characterised by chromosomal changes. Whilst over 200 genes have been associated with chromosomal translocations, to date, only MLL, TEL, and AML1 have been linked with childhood leukaemia. Interestingly, there is increasing evidence to support the theory that gene rearrangements such as these may originate in utero. As with many other human diseases, both genetic and environmental factors have been implicated in the aetiology of the disease. Although much has been documented with regard to diet, smoking, alcohol consumption and recreational and prescription drug use during pregnancy, there is no consistent evidence to support a link with any of these factors and childhood leukaemia. However, findings from studies investigating prenatal and early life exposures are often based on small numbers of cases as both the type of cancer and exposure are rare. Furthermore, accurate information relating to past exposures can be difficult to obtain and is often reliant on self-reporting. To further our understanding of the aetiology of childhood leukaemia and lymphoma, there are areas which clearly warrant investigation. These include collection of parental dietary folate data combined with genetic analysis of the folate related genes, in utero exposure to DNA topoisomerase II inhibitors, and the possible effects of assisted reproduction technology on disease susceptibility.

Parental cigarette smoking and childhood risks of hepatoblastoma: OSCC data

Reported cigarette smoking habits for the parents of 43 UK children who died with hepatoblastoma (1953-55 deaths, 1971-81 deaths) have been compared with corresponding information for the parents of 5777 healthy control children by means of unconditional logistic regression. Hepatoblastoma risks were doubled if both parents smoked relative to neither parent smoking (RR 2.28, 95% CI 1.02-5.09).

Parental smoking and childhood cancer: results from the United Kingdom Childhood Cancer Study

There are strong a priori reasons for considering parental smoking behaviour as a risk factor for childhood cancer but case - control studies have found relative risks of mostly only just above one. To investigate this further, self-reported smoking habits in parents of 3838 children with cancer and 7629 control children included in the United Kingdom Childhood Cancer Study (UKCCS) were analysed. Separate analyses were performed for four major groups (leukaemia, lymphoma, central nervous system tumours and other solid tumours) and more detailed diagnostic subgroups by logistic regression. In the four major groups, after adjustment for parental age and deprivation there were nonsignificant trends of increasing risk with number of cigarettes smoked for paternal preconception smoking and nonsignificant trends of decreasing risk for maternal preconception smoking (all P-values for trend >0.05). Among the diagnostic subgroups, a statistically significant increased risk of developing hepatoblastoma was found in children whose mothers smoked preconceptionally (OR=2.68, P=0.02) and strongest (relative to neither parent smoking) for both parents smoking (OR=4.74, P=0.003). This could be a chance result arising from multiple subgroup analysis. Statistically significant negative trends were found for maternal smoking during pregnancy for all diagnoses together (P<0.001) and for most individual groups, but there was evidence of under-reporting of smoking by case mothers. In conclusion, the UKCCS does not provide significant evidence that parental smoking is a risk factor for any of the major groups of childhood cancers.

Infertility and environmental pollutants

While it has long been known that female fertility is impaired by oestrogen exposure, it is unclear whether environmental pollutants with weak oestrogenic effects are sufficiently potent and prevalent to have biological effects in humans. Male fertility, or sperm concentration at least, appears to have deteriorated, and there is substantial spatial variation at both national and global level, as well as a genetic component. Sperm morphology and motility are implicated too. There is good evidence for an increase in testicular cancer, and possibly in other conditions that certain spatial characteristics plus evidence on heritability suggest are linked to impaired spermatogenesis. A candidate agent would need to have started increasing in the early 20th century. Weak environmental oestrogens are not responsible. Candidates include agents affecting endogenous maternal oestrogen levels, environmental anti-androgens (although these cannot explain the epidemiological findings), and dioxin and related compounds. Genetic damage should be considered as a unifying hypothesis, possibly focused on the Y-chromosome.

Tobacco use and cancer causation: association by tumour type

In the second part of our review we describe the association between tobacco use and risk of specific cancer types. There is evidence for an established association of tobacco use with cancer of the lung and larynx, head and neck, bladder, oesophagus, pancreas, stomach and kidney. In contrast, endometrial cancer is less common in women who smoke cigarettes. There are some data suggesting that tobacco use increases the risk for myeloid leukaemia, squamous cell sinonasal cancer, liver cancer, cervical cancer, colorectal cancer after an extended latency, childhood cancers and cancer of the gall bladder, adrenal gland and small intestine. Other forms of cancer, including breast, ovarian and prostate cancer, are unlikely to be linked to tobacco use.

Are vitamin and mineral deficiencies a major cancer risk?

Diet is estimated to contribute to about one-third of preventable cancers -- about the same amount as smoking. Inadequate intake of essential vitamins and minerals might explain the epidemiological findings that people who eat only small amounts of fruits and vegetables have an increased risk of developing cancer. Recent experimental evidence indicates that vitamin and mineral deficiencies can lead to DNA damage. Optimizing vitamin and mineral intake by encouraging dietary change, multivitamin and mineral supplements, and fortifying foods might therefore prevent cancer and other chronic diseases.

Effect of cigarette smoking on levels of seminal oxidative stress in infertile men: a prospective study

OBJECTIVE

To investigate levels of seminal oxidative stress (OS) and sperm quality in a group of infertile men with a history of cigarette smoking.

DESIGN

A prospective clinical study.

SETTING

Male infertility clinic, Urological Institute, the Cleveland Clinic Foundation, Cleveland, Ohio.

PATIENT(S)

Infertile men who smoked cigarettes (n = 20), infertile men who were nonsmokers (n = 32), and healthy nonsmoking donors (n = 13).

INTERVENTION(S)

Genital examination, standard semen analysis, sperm DNA damage.

MAIN OUTCOME MEASURE(S)

Levels of seminal reactive oxygen species (ROS) and total antioxidant capacity (TAC) measured by a chemiluminescence assay and seminal OS assessed by calculating a ROS-TAC score. Sperm DNA damage was measured by sperm chromatin structure assay.

RESULT(S)

Smoking was associated with a 48% increase in seminal leukocyte concentrations (P<.0001), a 107% increase in ROS levels (P=.001), and a 10-point decrease in ROS-TAC scores (P=.003). Differences in standard sperm variables and DNA damage indices between the infertile smokers and infertile nonsmokers were not statistically significant.

CONCLUSION(S)

Infertile men who smoke cigarettes have higher levels of seminal OS than infertile nonsmokers. Given the potential adverse effects of seminal OS on fertility, physicians should advise infertile men who smoke cigarettes to quit.

Importance of mitochondrial and nuclear sperm DNA in sperm quality assessment and assisted reproduction outcome

Intracytoplasmic sperm injection (ICSI) has made irrelevant the conventional criteria of concentration, motility and morphology for assessment of sperm quality and so we urgently need new assays by which to gauge sperm 'health'. ICSI may be facilitating the transfer of genetic disorders to future generations by bypassing all the natural hurdles for sperm selection without imposing more pertinent criteria of selection. Sperm DNA quality is vital to the future offspring irrespective of whether the child is conceived naturally, by in vitro fertilization (IVF) or by ICSI. The DNA integrity of sperm can be determined quickly and accurately using a range of techniques that also have strong prognostic power in predicting successful IVF and ICSI outcomes with ejaculated sperm. Moreover, there is a close correlation between testicular nuclear DNA integrity and pregnancy rates in ICSI. Mitochondrial DNA can be measured using long PCR in ejaculated and testicular sperm and is also useful for predicting success in assisted conception. This review discusses how the integrity of both nuclear and mitochondrial affect the choice of sperm for assisted conception.