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1.  Parental Smoking and Risk of Childhood Brain Tumors by Functional Polymorphisms in Polycyclic Aromatic Hydrocarbon Metabolism Genes 
PLoS ONE  2013;8(11):e79110.
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 (Pinteraction = 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 (ORno exposure = 1.0; OR≤3 hours/day = 1.32, 95% CI: 0.52–3.34; OR>3hours/day = 3.18, 95% CI: 0.92–11.0; Ptrend = 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.
doi:10.1371/journal.pone.0079110
PMCID: PMC3832498  PMID: 24260161
2.  Polymorphisms in metabolic genes, their combination and interaction with tobacco smoke and alcohol consumption and risk of gastric cancer: a case-control study in an Italian population 
BMC Cancer  2007;7:206.
Background
The distribution and the potential gene-gene and gene-environment interaction of selected metabolic genetic polymorphisms was investigated in relation to gastric cancer risk in an Italian population.
Methods
One hundred and seven cases and 254 hospital controls, matched by age and gender, were genotyped for CYP1A1, CYP2E1, mEH, GSTM1, GSTT1, NAT2 and SULT1A1 polymorphisms. Haplotype analysis was performed for EPHX1 exons 3 and 4, as well as CYP2E1 RsaI (*5 alleles) and CYP2E1 DraI (*5A or *6 alleles). The effect modification by alcohol and cigarette smoking was tested with the heterogeneity test, while the attributable proportion (AP) was used to measure the biological interaction from the gene-gene interaction analysis.
Results
Gastric cancer risk was found to be associated with the inheritance of GSTT1 null genotype (OR = 2.10, 95%CI: 1.27–3.44) and the SULT1A1 His/His genotype (OR = 2.46, 95%CI: 1.03–5.90). No differences were observed for the haplotype distributions among cases and controls. For the first time an increased risk was detected among individuals carrying the *6 variant allele of CYP2E1 if ever-drinkers (OR = 3.70; 95%CI: 1.45–9.37) with respect to never-drinkers (OR = 0.18; 95% CI: 0.22–1.46) (p value of heterogeneity among the two estimates = 0.001). Similarly, the effect of SULT1A1 variant genotype resulted restricted to ever-smokers, with an OR of 2.58 (95%CI: 1.27–5.25) for the carriers of His allele among smokers, and an OR of 0.86 (95%CI: 0.45–1.64) among never-smokers (p value of heterogeneity among the two estimates = 0.03). The gene-gene interaction analyses demonstrated that individuals with combined GSTT1 null and NAT2 slow acetylators had an additional increased risk of gastric cancer, with an OR of 3.00 (95%CI: 1.52–5.93) and an AP of 52%.
Conclusion
GSTT1, SULT1A1 and NAT2 polymorphisms appear to modulate individual's susceptibility to gastric cancer in this Italian population, particularly when more than one unfavourable genotype is present, or when combined with cigarette smoke. The increased risk for the carriers of CYP2E1*5A or *6 alleles among drinkers need to be confirmed by larger prospective studies.
doi:10.1186/1471-2407-7-206
PMCID: PMC2194718  PMID: 17996038
3.  Effects of SNPs (CYP1B1*2 G355T, CYP1B1*3 C4326G, and CYP2E1*5 G-1293C), Smoking, and Drinking on Susceptibility to Laryngeal Cancer among Han Chinese 
PLoS ONE  2014;9(10):e106580.
Purpose
This study was conducted to explore the effects of genetic polymorphisms (CYP1B1*2 G355T, CYP1B1*3 C4326G, and CYP2E1*5 G-1293C) and environmental factors (smoking and drinking) on susceptibility to laryngeal cancer in a Han Chinese study group.
Methods
This case-control study included 552 Han Chinese patients diagnosed with laryngeal cancer and 666 healthy control subjects of the same ethnicity, similar age, and gender. Genetic polymorphisms were examined using multi-PCR and Matrix Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF MS) methodology. The association of these genetic and environmental factors with susceptibility to laryngeal cancer was evaluated using a statistical approach.
Results
The frequencies of all three polymorphisms in the patient cohort were significantly different from those in the control cohort. Compared to the control cohort, carriers of variant alleles of CYP1B1*2 355T and CYP2E1*5 -1293C showed a higher risk for developing laryngeal cancer (for CYP1B1*2 355T, adjusted OR = 2.657, P <0.001; for CYP2E1*5 -1293C, adjusted OR = 1.938, P <0.001), while carriers of mutation allele CYP1B1*3 4326G showed a lower risk (adjusted OR = 0.562, P <0.001). Joint effects of these polymorphisms were observed. When compared to haplotype G355C4326G−1293, haplotypes T355C4326G−1293 (adjusted OR = 1.809, P <0.001), G355C4326C−1293 (adjusted OR = 1.644, P = 0.044), and T355C4326C−1293 (adjusted OR = 3.104, P <0.001) were associated with a significantly higher laryngeal cancer risk. The adjusted ORs for non-smokers, non-drinkers, smokers, and drinkers with the GT/TT genotype at CYP1B1*2 G355T were 2.190 (P = 0.006), 2.008 (P = 0.001), 5.875 (P <0.001), and 4.518 (P <0.001), respectively.
Conclusions
CYP1B1*2 355T and CYP2E1*5 -1293C are associated with an increased laryngeal cancer risk, while CYP1B1*3 4326G is associated with a decreased risk. These polymorphisms showed joint effects on laryngeal cancer risk. Smoking and drinking showed collaborative effects with two high risk alleles (CYP1B1*2 355T and CYP1B1*3 4326G) for promoting laryngeal cancer risk.
doi:10.1371/journal.pone.0106580
PMCID: PMC4191961  PMID: 25299224
4.  Risk of childhood cancer and adult lung cancer after childhood exposure to passive smoke: A meta-analysis. 
We identified more than 30 studies on the association between exposure to maternal tobacco smoke during pregnancy and cancer in childhood. We combined their results in meta-analyses based on a random effects model. The results of the meta-analyses suggest a small increase in risk of all neoplasms [relative risk (RR) 1.10; 95% confidence interval (CI), 1.03-1.19; based on 12 studies], but not of specific neoplasms such as leukemia (RR 1.05; CI, 0.82-1.34; 8 studies) and central nervous system tumors (RR 1.04; CI, 0.92-1. 18; 12 studies). Results for other specific neoplasms were sparse, but the available data did not suggest a strong association for any type of tumor. No clear evidence of dose response was present in the studies that addressed this issue. The results on exposure to maternal tobacco smoke before or after pregnancy are too sparse to allow a conclusion. The results on exposure to paternal tobacco smoke suggest an association with brain tumors (RR 1.22; CI, 1.05-1. 40; based on 10 studies) and lymphomas (RR 2.08; CI, 1.08-3.98; 4 studies). The data are too sparse for the other neoplasms, although the results of a few recent large studies are compatible with a weak carcinogenic effect of paternal smoke. For exposure from either maternal or paternal smoke, bias and confounding cannot yet be ruled out. Further studies are needed to confirm the hypothesis that parental tobacco smoke, from the father in particular, is a risk factor of childhood cancer. Results on the risk of lung cancer in adulthood and childhood passive smoking exposure are available from 11 studies: they do not provide evidence of an increased risk (summary RR 0.91; CI, 0.80-1.05).
Images
PMCID: PMC1637845  PMID: 10620527
5.  Paternal Smoking and Risk of Childhood Acute Lymphoblastic Leukemia: Systematic Review and Meta-Analysis 
Journal of Oncology  2011;2011:854584.
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, I2 = 18%) during any time period, 1.25 (95% CI: 1.08–1.46, I2 = 53%) preconception; 1.24 (95% CI: 1.07–1.43, I2 = 54%) during pregnancy, and 1.24 (95% CI: 0.96–1.60, I2 = 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.
doi:10.1155/2011/854584
PMCID: PMC3132639  PMID: 21765828
6.  Childhood cancer and parental use of tobacco: findings from the inter-regional epidemiological study of childhood cancer (IRESCC) 
British Journal of Cancer  2001;84(1):141-146.
Parental smoking data have been re-abstracted from the interview records of the Inter-Regional Epidemiological Study of Childhood Cancer (IRESCC) to test further the hypothesis that paternal cigarette smoking is a risk factor for the generality of childhood cancer. Reported cigarette smoking habits for the parents of 555 children diagnosed with cancer in the period 1980–1983 were compared, in two separate matched pairs analyses, with similar information for the parents of 555 children selected from GP lists (GP controls) and for the parents of 555 hospitalized children (hospital controls). When cases were compared with GP controls there was a statistically significant positive trend (P = 0.02) between the risk of childhood cancer and paternal daily consumption of cigarettes before the pregnancy; there was no significant trend for maternal smoking habit. When cases were compared with hospital controls there was a statistically significant negative trend (P< 0.001) between the risk of childhood cancer and maternal daily consumption of cigarettes before the pregnancy; there was no significant trend for paternal smoking habit. Neither of the significant trends could be explained by adjustment for socioeconomic grouping, ethnic origin or parental age at the birth of the child, or by simultaneous analysis of parental smoking habits. Relations between maternal consumption of cigarettes and birth weights suggested that (maternal) smoking data were equally reliable for case and control subjects, although comparisons with national data suggested that the hospital control parents were unusually heavy smokers. These findings give some support for the hypothesis that paternal cigarette smoking is a potential risk factor for the generality of childhood cancers. © 2001 Cancer Research Campaign http://www. bjcancer.com
doi:10.1054/bjoc.2000.1556
PMCID: PMC2363626  PMID: 11139329
childhood cancer; smoking; case-control study
7.  Cigarette smoking, genetic polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study 
BMC Cancer  2010;10:274.
Background
It is uncertain whether smoking is related to colorectal cancer risk. Cytochrome P-450 CYP1A1, glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1) are important enzymes in the metabolism of tobacco carcinogens, and functional genetic polymorphisms are known for these enzymes. We investigated the relation of cigarette smoking and related genetic polymorphisms to colorectal cancer risk, with special reference to the interaction between smoking and genetic polymorphism.
Methods
We used data from the Fukuoka Colorectal Cancer Study, a population-based case-control study, including 685 cases and 778 controls who gave informed consent to genetic analysis. Interview was conducted to assess lifestyle factors, and DNA was extracted from buffy coat.
Results
In comparison with lifelong nonsmokers, the odds ratios (OR) of colorectal cancer for <400, 400-799 and ≥800 cigarette-years were 0.65 (95% confidence interval [CI], 0.45-0.89), 1.16 (0.83-1.62) and 1.14 (0.73-1.77), respectively. A decreased risk associated with light smoking was observed only for colon cancer, and rectal cancer showed an increased risk among those with ≥400 cigarette-years (OR 1.60, 95% CI 1.04-2.45). None of the polymorphisms under study was singly associated with colorectal cancer risk. Of the gene-gene interactions studied, the composite genotype of CYP1A1*2A or CYP1A1*2C and GSTT1 polymorphisms was associated with a decreased risk of colorectal cancer, showing a nearly statistically significant (Pinteraction = 0.06) or significant interaction (Pinteraction = 0.02). The composite genotypes of these two polymorphisms, however, showed no measurable interaction with cigarette smoking in relation to colorectal cancer risk.
Conclusions
Cigarette smoking may be associated with increased risk of rectal cancer, but not of colon cancer. The observed interactions between CYP1A1 and GSTT1 polymorphisms warrant further confirmation.
doi:10.1186/1471-2407-10-274
PMCID: PMC2906477  PMID: 20534171
8.  Socioeconomic Status and Other Characteristics in Childhood Leukemia 
Background
Leukemia is the most prevalent childhood cancer, and Acute Lymphoblastic Leukemia (ALL) constitutes 75% of all cases. Some epidemiological studies have shown a relationship between socioeconomic status (SES) and some childhood cancers. In the present study, an attempt was made to assess socioeconomical status in a case-control study.
Materials and Methods
In 2010, a case-control study was conducted on 100 cases of acute lymphoblastic leukemia aged 1 to14 years in Department of Pediatric Oncology of Dr.Sheikh Hospital in Mashhad – Iran and matched age and sex with 400 healthy controls. Data was collected by interview using a questionnaire. Ninety five percent confidence intervals were used to measure the relationship between childhood Acute Lymphoblastic Leukemia and parental education, income status, father's job (Socioeconomic status), number of children, birth score and paternal smoking.
Results
There was a significant difference in parental education level, income status, and number of children, birth score, father's job and paternal smoking between two groups. Regression analysis showed that the risk of childhood ALL associated with paternal smoking, and father's high risk job. Fifty percent cases and thirty five percent of control groups located in upper lower and lower middle class of socioeconomic status, respectively. There is a meaningful different between socioeconomic status in two groups. But the risk of childhood ALL did not associate with socioeconomic status.
Conclusion
The results suggest that paternal smoking and father’s high risk job are related to risk of childhood leukemia. It should be considered for planning support.
PMCID: PMC3915441  PMID: 24575261
Child; Leukemia; Social Class
9.  CYP2C9 Variants Increase Risk of Colorectal Adenoma Recurrence and Modify Associations with Smoking but Not Aspirin Treatment 
Cancer causes & control : CCC  2012;24(1):47-54.
Purpose
The cytochrome P450 2C9 enzyme (CYP2C9) is involved in metabolism of endogenous compounds, drugs and procarcinogens. Two common nonsynonymous polymorphisms in CYP2C9 are associated with reduced enzyme activity: CYP2C9*2 (rs1799853, R144C) and CYP2C9*3 (rs1057910, I359L).
Methods
We investigated whether CYP2C9 genotype was associated with risk of colorectal adenoma and/or modified associations with aspirin treatment or cigarette smoking in a cohort of 928 participants in a randomized trial of aspirin chemoprevention. Generalized linear regression was used to compute relative risks (RRs) and 95% confidence intervals (95% CIs). Multiplicative interactions terms were used to assess effect modification.
Results
CYP2C9 genotype was associated with increased risks for adenoma recurrence of 29% (RR=1.29, 95% CI =1.09–1.51) for ≥1 variant allele (CYP2C9*2 or *3) and 47% (RR=1.47, 95% CI=1.19–1.83) for ≥1 CYP2C9*3 allele. The risk for advanced lesions or multiple (≥3) adenomas was increased by 64% (RR=1.64, 95% CI=1.18–2.28) for ≥1 variant allele (CYP2C9*2 or *3) and 79% (RR=1.79, 95% CI=1.16–2.75) for ≥1 CYP2C9*3 allele. Genotype modified associations with smoking, but not aspirin treatment. The adenoma risk was increased by 26% (RR=1.26, 95% CI=0.99–1.58) for former smokers and 60% (RR=1.60, 95% CI=1.19–2.15) for current smokers among wild-type individuals, but there was no increased risk among individuals with ≥1 variant allele (CYP2C9*2 or *3) (Pinteraction=0.04).
Conclusions
Carriers of CYP2C9 variants with lower enzyme activity have increased overall risk of colorectal adenoma but reduced adenoma risk associated with cigarette smoking. These results may be due to effects on the synthesis of endogenous eicosanoids and/or reduced activation of procarcinogens in smoke by CYP2C9 variants.
doi:10.1007/s10552-012-0088-6
PMCID: PMC3529799  PMID: 23081681
colorectal neoplasia; CYP2C9; smoking; aspirin; polymorphism
10.  Birth weight and other perinatal characteristics and childhood leukemia in California 
Cancer epidemiology  2012;36(6):e359-e365.
Aims
We conducted a large registry-based study in California to investigate the association of perinatal factors and childhood leukemia with analysis of two major subtypes, acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML).
Methods
We linked California cancer and birth registries to obtain information on 5788 cases and 5788 controls matched on age and sex (1:1). We examined the association of birth weight, gestational age, birth and pregnancy order, parental ages, and specific conditions during pregnancy and risk of total leukemia, ALL and AML using conditional logistic regression, with adjustment for potential confounders.
Results
The odds ratio (OR) per 1000 gram increase in birth weight was 1.11 for both total leukemia and ALL. The OR were highest for babies weighing ≥4,500g with reference <2,500g: 1.59 (95% CI: 1.05-2.40) and 1.70 (95% CI: 1.08-2.68) for total leukemia and ALL, respectively. For AML, increase in risk was also observed but the estimate was imprecise due to small numbers. Compared to average-for-gestational age (AGA), large-for-gestational age (LGA) babies were at slightly increased risk of total childhood leukemia (OR=1.10) and both ALL and AML (OR=1.07 and OR=1.13, respectively) but estimates were imprecise. Being small-forgestational age (SGA) was associated with reduced risk of childhood leukemia (OR=0.81, 95% CI: 0.67-0.97) and ALL (OR=0.77, 95% CI: 0.63-0.94), but not AML. Being first-born was associated with decreased risk of AML only (OR=0.70; 95% CI: 0.53-0.93). Compared to children with paternal age <25 years, children with paternal age between 35 and 45 years were at increased risk of total childhood leukemia (OR=1.12; 95% CI: 1.04-1.40) and ALL (OR=1.23; 95% CI: 1.04-1.47). None of conditions during pregnancy examined or maternal age were associated with increased risk of childhood leukemia or its subtypes.
Conclusions
Our results suggest that high birth weight and LGA were associated with increased risk and SGA with decreased risk of total childhood leukemia and ALL, being first-born was associated with decreased risk of AML, and advanced paternal age was associated with increased risk of ALL. These findings suggest that associations of childhood leukemia and perinatal factors depend highly on subtype of leukemia.
doi:10.1016/j.canep.2012.08.002
PMCID: PMC4034745  PMID: 22926338
childhood leukemia; birth weight; birth order; parental age; perinatal factors; pregnancy complications
11.  Tobacco Smoke Exposure and the Risk of Childhood Acute Lymphoblastic and Myeloid Leukemias by Cytogenetic Subtype 
Background
Tobacco smoke contains carcinogens known to damage somatic and germ cells. We investigated the effect tobacco smoke on the risk of childhood acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML), especially subtypes of pre-natal origin like ALL with translocation t(12;21) or high-hyperdiploidy (51–67 chromosomes).
Methods
We collected information on exposures to tobacco smoking before conception, during pregnancy, and after birth in 767 ALL cases, 135 AML cases, and 1,139 controls (1996–2008). Among cases, chromosome translocations, deletions, or aneuploidy were identified by conventional karyotype and fluorescence in-situ hybridization.
Results
Multivariable regression analyses for ALL and AML overall showed no definite evidence of associations with self-reported (yes/no) parental prenatal active smoking and child's passive smoking. However, children with history of paternal prenatal smoking combined with postnatal passive smoking had a 1.5-fold increased risk of ALL (95% CI: 1.01–2.23), compared to those without smoking history (ORs for pre- or postnatal smoking only were close to one). This joint effect was seen for B-cell precursor ALL with t(12;21) (OR=2.08; 95% CI: 1.04–4.16), but not high hyperdiploid B-cell ALL. Similarly, child's passive smoking was associated with an elevated risk of AML with chromosome structural changes (OR=2.76; 95% CI: 1.01–7.58), but not aneuploidy.
Conclusions
our data suggest that exposure to tobacco smoking before were associated with increased risks of childhood ALL and AML; and risks varied by timing of exposure (before and/or after birth) and cytogenetic subtype, based on imprecise estimates.
Impact
Parents should limit exposures to tobacco smoke before and after the child's birth.
doi:10.1158/1055-9965.EPI-13-0350
PMCID: PMC3769478  PMID: 23853208
Childhood leukemia; tobacco smoking; cytogenetics
12.  Childhood Exposure to Secondhand Smoke and Functional Mannose Binding Lectin Polymorphisms Are Associated with Increased Lung Cancer Risk 
Background
Exposure to secondhand smoke during adulthood has detrimental health effects, including increased lung cancer risk. Compared with adults, children may be more susceptible to secondhand smoke. This susceptibility may be exacerbated by alterations in inherited genetic variants of innate immunity genes. We hypothesized a positive association between childhood secondhand smoke exposure and lung cancer risk that would be modified by genetic polymorphisms in the mannose binding lectin-2 (MBL2) gene resulting in well-known functional changes in innate immunity.
Methods
Childhood secondhand smoke exposure and lung cancer risk was assessed among men and women in the ongoing National Cancer Institute-Maryland Lung Cancer (NCI-MD) study, which included 624 cases and 348 controls. Secondhand smoke history was collected via in-person interviews. DNA was used for genotyping the MBL2 gene. To replicate, we used an independent case-control study from Mayo Clinic consisting of 461 never smokers, made up of 172 cases and 289 controls. All statistical tests were two-sided.
Results
In the NCI-MD study, secondhand smoke exposure during childhood was associated with increased lung cancer risk among never smokers [odds ratio (OR), 2.25; 95% confidence interval (95% CI), 1.04-4.90]. This was confirmed in the Mayo study (OR, 1.47; 95% CI, 1.00-2.15). A functional MBL2 haplotype associated with high circulating levels of MBL and increased MBL2 activity was associated with increased lung cancer risk among those exposed to childhood secondhand smoke in both the NCI-MD and Mayo studies (OR, 2.52; 95% CI, 1.13-5.60, and OR, 2.78; 95% CI, 1.18-3.85, respectively).
Conclusions
Secondhand smoke exposure during childhood is associated with increased lung cancer risk among never smokers, particularly among those possessing a haplotype corresponding to a known overactive complement pathway of the innate immune system.
doi:10.1158/1055-9965.EPI-09-0986
PMCID: PMC2951599  PMID: 19959685
13.  Parental smoking during pregnancy and risk of overweight and obesity in the daughter 
Objective
Emerging evidence suggests that prenatal exposures may affect long-term health outcomes. In utero exposure to smoking is associated with an increased risk of overweight and obesity in children and adolescents. However, few studies have examined how prenatal exposure to parental smoking influences risk of obesity in adulthood and whether these associations are independent of childhood and adolescent adiposity. The aim of the current study was to investigate whether prenatal exposure to parental smoking influences body size in adulthood and whether any association may be mediated by childhood and adolescent body size.
Methods
We investigated the association between parental smoking during pregnancy and risk of overweight and obesity in adulthood and at age 18, and adiposity during childhood among 35,370 participants in the Nurses’ Health Study II. Data on smoking during pregnancy and socioeconomic variables were provided by the mothers, and anthropometric data and adult risk factors were reported by participants.
Results
After adjustment for socioeconomic and behavioral variables, maternal smoking during pregnancy was associated with adiposity at ages 5–10, age 18, and during adulthood. For age 18 overweight the ORs (95% CIs) for 1–14, 15–24, and 25+cigarettes/day were 1.13 (1.18–1.50), 1.40 (1.20–1.64), and 1.15 (0.79–1.69) and for obesity were 1.41 (1.14–1.75), 1.69 (1.31–2.18), and 2.36 (1.44–3.86). The corresponding ORs (95% CIs) for obesity in adulthood were 1.26 (1.16–1.37), 1.46 (1.30–1.63), and 1.43 (1.10–1.86). Risk of adiposity was not increased among daughters whose mothers stopped smoking during the first trimester (OR [95% CI] for overweight (1.03 [95% CI 0.90–1.17] and obesity (1.12 [95% CI 0.97–1.30]). Women whose fathers smoked during pregnancy were also at increased risk of overweight and obesity in adulthood with covariate-adjusted ORs (95% CIs) for obesity of 1.19 (1.11–1.29) for 1–14 cigarettes/day, 1.27 (1.18–1.37) for 15–24 cigarettes/day, and 1.40 (1.27–1.54) for 25+ cigarettes/day compared to fathers who did not smoke (ptrend<0.0001). Paternal smoking during pregnancy was also associated with an increased risk of obesity at age 18 among those whose fathers smoked 15 or more cigarettes/day but was not associated with childhood body size.
Conclusions
Maternal smoking during pregnancy was associated in a dose-response manner with overweight and obesity in the daughter through adolescence and adult life. Smoking cessation during the first trimester appears to mitigate this excess risk.
Paternal smoking was also associated with risk of overweight and obesity of the adult daughter and this association persisted after adjustment for maternal smoking.
doi:10.1038/ijo.2013.101
PMCID: PMC3795801  PMID: 23736356
pregnancy; prenatal programming; cigarette smoking; obesity
14.  Parental Smoking during Pregnancy and Offspring Cardio-Metabolic Risk Factors at ages 17 and 32 
Atherosclerosis  2014;235(2):430-437.
Objective
To examine the association of maternal and/or paternal smoking during pregnancy with offspring cardio-metabolic risk (CMR) factors at adolescence and early adulthood, taking into account socio-demographic, medical and lifestyle characteristics of parents and offspring, as well as offspring common genetic variation.
Methods
We used a population-based cohort of all 17 003 births in Jerusalem during 1974–76, with available archival data on parental and birth characteristics. Measurements at age 17 were assessed at military induction examinations for 11 530 offspring. 1440 offspring from the original 1974–1976 birth cohort were sampled using a stratified sampling approach, and were interviewed and examined at age 32. Parental smoking during pregnancy (i.e. maternal, paternal and any parent) was primarily defined dichotomously (any number of cigarettes smoked daily by mother or father during pregnancy vs. non-smokers). Additionally, smoking was assessed by quantity of cigarettes smoked daily. Linear regression models were used to evaluate the associations of parental smoking during pregnancy with various offspring CMR factors, after controlling for potential confounders and for genetic variation in candidate genes.
Results
Prevalence of exposure to parental smoking in-utero (i.e. smoking of any parent) was 53.2% and 48.4% among the 17 years old and 32 years old samples, respectively. At age 17, smoking of at least one parent during pregnancy was significantly associated with weight (B=1.39), height (B=0.59), BMI (B=0.32) and pulse rate (B=−0.78) (p-values<0.001). At age 32, parental smoking, adjusted for covariates, was associated with 2.22 kg higher mean offspring weight, 0.95 cm higher mean offspring height, 0.57 kg/m2 higher BMI, and 1.46 cm higher waist-circumference (p-values≤0.02). Similar results, reflecting a dose response, were observed when maternal and paternal smoking were assessed by number of cigarettes smoked daily.
Conclusions
This prospective study demonstrates a potential long-term adverse effect of parental smoking during pregnancy on offspring health and calls for increasing efforts to promote smoking cessation of both parents before pregnancy.
doi:10.1016/j.atherosclerosis.2014.05.937
PMCID: PMC4123626  PMID: 24937467
cohort study; smoking; pregnancy; obesity; risk factors
15.  Parental risk factors and anorectal malformations: systematic review and meta-analysis 
Background
Anorectal malformations (ARM) are rare forms of congenital uro-rectal anomalies with largely unknown causes. Besides genetic factors, prenatal exposures of the parents to nicotine, alcohol, caffeine, illicit drugs, occupational hazards, overweight/obesity and diabetes mellitus are suspected as environmental risk factors.
Methods
Relevant studies published until August 2010 were identified through systematic search in PubMed, EMBASE, ISI Web of Knowledge and the Cochrane Library databases. Furthermore, related and cross-referencing publications were reviewed. Pooled odds ratios (95% confidence intervals) were determined to quantify associations of maternal and paternal smoking, maternal alcohol consumption, underweight (body mass index [BMI] < 18.5), overweight (BMI 25-29.9), obesity (BMI ≥30) and maternal diabetes mellitus with ARM using meta-analyses.
Results
22 studies that reported on the association between prenatal environmental risk factors and infants born with ARM were included in this review. These were conducted in the United States of America (n = 12), Spain (n = 2), Sweden (n = 2), the Netherlands (n = 2), Japan (n = 1), France (n = 1), Germany (n = 1) and Hungary (n = 1). However, only few of these studies reported on the same risk factors. Studies were heterogeneous with respect to case numbers, control types and adjustment for covariates. Consistently increased risks were observed for paternal smoking and maternal overweight, obesity and diabetes, but not for maternal smoking and alcohol consumption. In meta-analyses, pooled odds ratios (95% confidence intervals) for paternal smoking, maternal overweight, obesity, pre-gestational and gestational diabetes were 1.53 (1.04-2.26), 1.25 (1.07-1.47), 1.64 (1.35-2.00), 4.51 (2.55-7.97) and 1.81 (1.23-2.65), respectively.
Conclusion
Evidence on risk factors for ARM from epidemiological studies is still very limited. Nevertheless, the few available studies indicate paternal smoking and maternal overweight, obesity and diabetes to be associated with increased risks. Further, ideally large-scale multicentre and register-based studies are needed to clarify the role of key risk factors for the development of ARM.
doi:10.1186/1750-1172-6-25
PMCID: PMC3121580  PMID: 21586115
anorectal malformations; imperforate anus; anal atresia; birth defects; risk factors; pregnancy
16.  Polymorphisms in genes involved in the estrogen pathway and mammographic density 
BMC Cancer  2010;10:636.
Background
Single nucleotide polymorphisms (SNPs) in genes involved in the estrogen pathway appear to be associated with breast cancer risk and possibly with mammographic density (MD), but little is known of these associations among premenopausal women. This study examines the association of 11 polymorphisms in five estrogen-related genes (estrogen receptors alpha and beta (ERα, ERβ), 17β-hydroxysteroid dehydrogenase 1 (HSD17B1), catechol-O-methyltransferase (COMT), cytochrome P450 1B1 (CYP1B1)) with premenopausal MD. Effect modification of four estrogen-related factors (parity, age at menarche, hormonal derivatives use and body mass index (BMI)) on this relation is also assessed.
Methods
Polymorphisms were genotyped in 741 premenopausal Caucasian women whose MD was measured in absolute density (AD, cm2) and percent density using a computer-assisted method. Multivariate linear models were used to examine the associations (Ptrend) and interactions (Pi).
Results
None of the SNPs showed a statistically significant association with AD. However, each additional rare allele of rs1056836 CYP1B1 was associated with a reduction in AD among nulliparous women (Ptrend = 0.004), while no association was observed among parous women (Ptrend = 0.62; Pi = 0.02). An increase in the number of rare alleles of the HSD17B1 SNP (rs598126 and rs2010750) was associated with an increase in AD among women who never used hormonal derivatives (Ptrend = 0.06 and Ptrend = 0.04, respectively), but with a decrease in AD among past hormonal derivatives users (Ptrend = 0.04; Pi = 0.02 and Ptrend = 0.08; Pi = 0.01, respectively). Moreover, a negative association of rs598126 HSD17B1 SNP with AD was observed among women with higher BMI (>median) (Ptrend = 0.01; Pi = 0.02). A negative association between an increased number of rare alleles of COMT rs4680 SNP and AD was limited to women who never used hormonal derivatives (Ptrend = 0.02; Pi = 0.03) or with late age at menarche (>median) (Ptrend = 0.03; Pi = 0.02). No significant association was observed between polymorphisms in the ERα or ERβ genes and AD. Similar results, although less significant, were observed when MD was assessed in percent density.
Conclusion
SNPs located in CYP1B1, COMT or HSD17B1 genes seem to be associated with MD in some strata of estrogen-related factors. Our findings suggest that modifying effects of estrogen-related factors should be considered when evaluating associations of polymorphisms in estrogen-related genes with premenopausal mammographic density.
doi:10.1186/1471-2407-10-636
PMCID: PMC3000407  PMID: 21092186
17.  CYP2E1 Rsa I polymorphism impacts on risk of colorectal cancer association with smoking and alcohol drinking 
AIM: To investigate associations between the Rsa I polymorphism of CYP2E1 and risk of colorectal cancer.
METHODS: A case-control study was conducted with 315 colorectal cancer cases (105 colon, 210 rectal) and 439 population-based controls in Jiangsu Province of China. Genomic DNA samples were assayed for restriction fragment length polymorphisms in CYP2E1 by PCR amplification followed by digestion with Rsa I. Information on smoking and alcohol drinking was collected using a questionnaire. Odds ratios (ORs) were estimated with an unconditional logistic model.
RESULTS: The proportional distribution of the CYP2E1 Rsa I c1/c1, c1/c2 and c2/c2 genotypes were 61.4%, 35.6% and 3.0% in controls, 60.6%, 33.7% and 5.8% in colon cancer cases, and 58.4%, 34.0% and 7.7% in rectal cancer cases, respectively. A significant difference was noted between controls and rectal cancer cases (P = 0.029), the c2/c2 genotype being associated with elevated OR (adjusted age, sex and status of the smoking and alcohol drinking) for rectal cancer (1.64, 95% CI, 1.12-2.41, vs c1 allele carriers), but not for colon cancer. In interaction analysis between the CYP2E1 Rsa I genotype and smoking and drinking habits, we found a significant cooperative action between the c2/c2 genotype and alcohol drinking in the sex-, age-adjusted ORs for both colon (4.74, 95% CI, 1.10-20.40) and rectal (5.75, 95% CI, 1.65-20.05) cancers. Among non-smokers, the CYP2E1 Rsa I c2/c2 genotype was also associated with elevated ORs in the two sites (1.95, 95% CI, 0.99-3.86 and 2.30, 95% CI, 1.32-3.99).
CONCLUSION: The results of the present study suggest that the CYP2E1 c2/c2 genotype increases susceptibility to rectal cancer and the gene-environmental interactions between the CYP2E1 polymorphism and smoking or alcohol drinking exist for colorectal neoplasia in general.
doi:10.3748/wjg.v13.i43.5725
PMCID: PMC4171258  PMID: 17963298
CYP2E1; Gene polymorphism; Smoking; Alcohol drinking; Colorectal cancer
18.  Socioeconomic Status and Childhood Leukemia Incidence in Switzerland 
Frontiers in Oncology  2015;5:139.
Socioeconomic status (SES) discrepancies exist for child and adult cancer morbidity and are a major public health concern. In this Swiss population-based matched case–control study on the etiology of childhood leukemia, we selected the cases from the Swiss Childhood Cancer Registry diagnosed since 1991 and the controls randomly from census. We assigned eight controls per case from the 1990 and 2000 census and matched them by the year of birth and gender. SES information for both cases and controls was obtained from census records by probabilistic record linkage. We investigated the association of SES with childhood leukemia in Switzerland, and explored whether it varied with different definitions of socioeconomic status (parental education, living condition, area-based SES), time period, and age. In conditional logistic regression analyses of 565 leukemia cases and 4433 controls, we found no consistent evidence for an association between SES and childhood leukemia. The odds ratio comparing the highest with the lowest SES category ranged from 0.95 (95% CI: 0.71–1.26; Ptrend = 0.73) for paternal education to 1.37 (1.00–1.89; Ptrend = 0.064) for maternal education. No effect modification was found for time period and age at diagnosis. Based on this population-based study, which avoided participation and reporting bias, we assume the potential association of socioeconomic status and childhood leukemia if existing to be small. This study did not find evidence that socioeconomic status, of Switzerland or comparable countries, is a relevant risk factor or strong confounder in etiological investigations on childhood leukemia.
doi:10.3389/fonc.2015.00139
PMCID: PMC4485172  PMID: 26175964
childhood cancer; leukemia; socioeconomic status; risk factor; case–control study
19.  ‘Smoking Genes’: A Genetic Association Study 
PLoS ONE  2011;6(10):e26668.
Some controversy exists on the specific genetic variants that are associated with nicotine dependence and smoking-related phenotypes. The purpose of this study was to analyse the association of smoking status and smoking-related phenotypes (included nicotine dependence) with 17 candidate genetic variants: CYP2A6*1×2, CYP2A6*2 (1799T>A) [rs1801272], CYP2A6*9 (−48T>G) [rs28399433], CYP2A6*12, CYP2A13*2 (3375C>T) [rs8192789], CYP2A13*3 (7520C>G), CYP2A13*4 (579G>A), CYP2A13*7 (578C>T) [rs72552266], CYP2B6*4 (785A>G), CYP2B6*9 (516G>T), CHRNA3 546C>T [rs578776], CHRNA5 1192G>A [rs16969968], CNR1 3764C>G [rs6928499], DRD2-ANKK1 2137G>A (Taq1A) [rs1800497], 5HTT LPR, HTR2A −1438A>G [rs6311] and OPRM1 118A>G [rs1799971]. We studied the genotypes of the aforementioned polymorphisms in a cohort of Spanish smokers (cases, N = 126) and ethnically matched never smokers (controls, N = 80). The results showed significant between-group differences for CYP2A6*2 and CYP2A6*12 (both P<0.001). Compared with carriers of variant alleles, the odds ratio (OR) for being a non-smoker in individuals with the wild-type genotype of CYP2A6*12 and DRD2-ANKK1 2137G>A (Taq1A) polymorphisms was 3.60 (95%CI: 1.75, 7.44) and 2.63 (95%CI: 1.41, 4.89) respectively. Compared with the wild-type genotype, the OR for being a non-smoker in carriers of the minor CYP2A6*2 allele was 1.80 (95%CI: 1.24, 2.65). We found a significant genotype effect (all P≤0.017) for the following smoking-related phenotypes: (i) cigarettes smoked per day and CYP2A13*3; (ii) pack years smoked and CYP2A6*2, CYP2A6*1×2, CYP2A13*7, CYP2B6*4 and DRD2-ANKK1 2137G>A (Taq1A); (iii) nicotine dependence (assessed with the Fagestrom test) and CYP2A6*9. Overall, our results suggest that genetic variants potentially involved in nicotine metabolization (mainly, CYP2A6 polymorphisms) are those showing the strongest association with smoking-related phenotypes, as opposed to genetic variants influencing the brain effects of nicotine, e.g., through nicotinic acetylcholine (CHRNA5), serotoninergic (HTR2A), opioid (OPRM1) or cannabinoid receptors (CNR1).
doi:10.1371/journal.pone.0026668
PMCID: PMC3202555  PMID: 22046326
20.  Phase I Metabolic Genes and Risk of Lung Cancer: Multiple Polymorphisms and mRNA Expression 
PLoS ONE  2009;4(5):e5652.
Polymorphisms in genes coding for enzymes that activate tobacco lung carcinogens may generate inter-individual differences in lung cancer risk. Previous studies had limited sample sizes, poor exposure characterization, and a few single nucleotide polymorphisms (SNPs) tested in candidate genes. We analyzed 25 SNPs (some previously untested) in 2101 primary lung cancer cases and 2120 population controls from the Environment And Genetics in Lung cancer Etiology (EAGLE) study from six phase I metabolic genes, including cytochrome P450s, microsomal epoxide hydrolase, and myeloperoxidase. We evaluated the main genotype effects and genotype-smoking interactions in lung cancer risk overall and in the major histology subtypes. We tested the combined effect of multiple SNPs on lung cancer risk and on gene expression. Findings were prioritized based on significance thresholds and consistency across different analyses, and accounted for multiple testing and prior knowledge. Two haplotypes in EPHX1 were significantly associated with lung cancer risk in the overall population. In addition, CYP1B1 and CYP2A6 polymorphisms were inversely associated with adenocarcinoma and squamous cell carcinoma risk, respectively. Moreover, the association between CYP1A1 rs2606345 genotype and lung cancer was significantly modified by intensity of cigarette smoking, suggesting an underling dose-response mechanism. Finally, increasing number of variants at CYP1A1/A2 genes revealed significant protection in never smokers and risk in ever smokers. Results were supported by differential gene expression in non-tumor lung tissue samples with down-regulation of CYP1A1 in never smokers and up-regulation in smokers from CYP1A1/A2 SNPs. The significant haplotype associations emphasize that the effect of multiple SNPs may be important despite null single SNP-associations, and warrants consideration in genome-wide association studies (GWAS). Our findings emphasize the necessity of post-GWAS fine mapping and SNP functional assessment to further elucidate cancer risk associations.
doi:10.1371/journal.pone.0005652
PMCID: PMC2682568  PMID: 19479063
21.  IL13 gene polymorphisms modify the effect of exposure to tobacco smoke on persistent wheeze and asthma in childhood, a longitudinal study 
Respiratory Research  2008;9(1):2.
Background
Tobacco smoke and genetic susceptibility are risk factors for asthma and wheezing. The aim of this study was to investigate whether there is a combined effect of interleukin-13 gene (IL13) polymorphisms and tobacco smoke on persistent childhood wheezing and asthma.
Methods
In the Isle of Wight birth cohort (UK, 1989–1999), five IL13 single nucleotide polymorphisms (SNPs): rs1800925 (-1112C/T), rs2066960, rs1295686, rs20541 (R130Q) and rs1295685 were genotyped. Parents were asked whether their children had wheezed in the last 12 months at ages 1, 2, 4 and 10 years. Children who reported wheeze in the first 4 years of life and also had wheezing at age 10 were classified as early-onset persistent wheeze phenotype; non-wheezers never wheezed up to age 10. Persistent asthma was defined as having a diagnosis of asthma both during the first four years of life and at age 10. Logistic regression methods were used to analyze data on 791 children with complete information. Potential confounders were gender, birth weight, duration of breast feeding, and household cat or dog present during pregnancy.
Results
Maternal smoking during pregnancy was associated with early-onset persistent wheeze (OR 2.93, p < 0.0001); polymorphisms in IL13 were not (OR 1.15, p = 0.60 for the common haplotype pair). However, the effect of maternal smoking during pregnancy was stronger in children with the common IL13 haplotype pair compared to those without it (OR 5.58 and OR 1.29, respectively; p for interaction = 0.014). Single SNP analysis revealed a similar statistical significance for rs20541 (p for interaction = 0.02). Comparable results were observed for persistent childhood asthma (p for interaction = 0.03).
Conclusion
This is the first report that shows a combined effect of in utero exposure to smoking and IL13 on asthma phenotypes in childhood. The results emphasize that genetic studies need to take environmental exposures into account, since they may explain contradictory findings.
doi:10.1186/1465-9921-9-2
PMCID: PMC2265286  PMID: 18186920
22.  Environmental Tobacco Smoke in Relation to Bladder Cancer Risk – The Shanghai Bladder Cancer Study 
Background
Environmental tobacco smoke (ETS) contains tobacco carcinogens. Hepatic cytochrome P450 (CYP) 1A2 and N-acetyltransferase (NAT2) are important isoenzymes in activation and detoxification, respectively, of tobacco carcinogens. Data on ETS and bladder cancer risk are sparse.
Methods
We examined the effects of ETS alone and combined with NAT2/CYP1A2 on bladder cancer risk among lifelong-nonsmokers in a case-control study involving 195 patients and 261 controls in Shanghai, China. A comprehensive history of ETS exposure was determined through in-person interviews while CYP1A2 and NAT2 phenotypes by a caffeine-based urinary assay.
Results
ETS exposure was related to an overall statistically non-significant 38% increased bladder cancer risk. The risk increased with increasing number of cigarettes smoked by household members or number of hours per day at workplace where coworkers smoked. Compared with no ETS exposure, subjects living with smoking parents during childhood had an OR of 2.43 (95% CI=0.99–5.96) for bladder cancer. When all ETS sources were combined, the risk increased with increasing total ETS score (Ptrend = 0.03). The OR for high versus nil ETS exposure was 3.00 (95% CI =1.24–7.26). The increased risk with ETS was mainly seen among individuals possessing a CYP1A2 high efficiency and/or a NAT2 slow acetylation phenotype (Ptrend = 0.04).
Conclusions
ETS was associated with an increased bladder cancer risk for lifelong-nonsmokers. The association was stronger for people possessing the at-risk phenotypes of CYP1A2 and/or NAT2.
Impact
Reducing exposure to ETS for children and genetically more susceptible individuals could be more effective for bladder cancer prevention.
doi:10.1158/1055-9965.EPI-10-0823
PMCID: PMC3003610  PMID: 21056942
23.  Passive Smoking and Breast Cancer Risk among Non-Smoking Women: A Case-Control Study in China 
PLoS ONE  2015;10(4):e0125894.
Background
The role of passive smoking on breast cancer risk was unclear. This study aimed to evaluate the association between passive smoking and breast cancer risk among Chinese women.
Methods/Principal Findings
A hospital-based case-control study, including 877 breast cancer cases and 890 controls, frequency-matched by age and residence, was conducted. A structured questionnaire was used to collect information on passive smoking history through face-to-face interview by trained interviewers. Unconditional logistic regression models were used to estimate the association between passive smoking and breast cancer risk. A positive association between any passive smoking exposure and breast cancer risk was observed. Compared with women who were never exposed to passive smoking, women who were ever exposed had a higher breast cancer risk, with the adjusted odds ratio (OR) and 95% confidence interval (CI) of 1.35 (1.11-1.65). Similar result was found on home passive smoking exposure and breast cancer risk, but not on workplace passive smoking exposure. Women who were ever exposed to tobacco smoke at home had a higher risk of breast cancer compared with never exposed women, with the adjusted OR (95% CI) of 1.30 (1.05-1.61). Home passive smoking exposure showed significant dose-response relationships with breast cancer risk in smoker-years, cigarettes/day and total pack-years (Ptrend=0.003, 0.006 and 0.009, respectively). An increased total smoker-years of any passive exposure significantly elevated the risk of breast cancer (Ptrend<0.001). Positive associations and dose-response relationships were found among postmenopausal women and all subtypes of estrogen receptor (ER) and progesterone receptor (PR) status of breast cancer.
Conclusions
Passive smoking was associated with an increased risk of breast cancer among non-smoking Chinese women. A stronger positive association with breast cancer risk was seen mainly among postmenopausal women.
doi:10.1371/journal.pone.0125894
PMCID: PMC4411087  PMID: 25915759
24.  Variation in xenobiotic transport and metabolism genes, household chemical exposures, and risk of childhood acute lymphoblastic leukemia 
Cancer Causes & Control  2012;23(8):1367-1375.
Background
Recent studies suggest that environmental exposures to pesticides, tobacco, and other xenobiotic chemicals may increase risk of childhood acute lymphoblastic leukemia (ALL). We sought to evaluate the role of genes involved in xenobiotic transport and metabolism in childhood ALL risk, both alone and in conjunction with household chemical exposures previously found to be associated with childhood ALL risk.
Methods
We conducted a population-based epidemiologic study of 377 cases and 448 controls in California, utilizing a haplotype-based approach to evaluate 42 xenobiotic transport and metabolism genes in conjunction with data on self-reported household chemical exposures.
Results
We identified significant associations of childhood ALL risk with haplotypes of ABCB1, ARNT, CYP2C8, CYP1A2, CYP1B1, and IDH1. In addition, certain haplotypes showed significant joint effects with self-reported household chemical exposures on risk of childhood ALL. Specifically, elevated risks associated with use of paints in the home (ever) and indoor insecticides (pre-birth) were limited to subjects carrying specific haplotypes of CYP2C8 and ABCB1, respectively.
Conclusions
Our results provide support for a role of xenobiotic transport and metabolism pathways in risk of childhood ALL and indicate that genes in these pathways may modulate the risk of disease associated with use of common household chemicals. Additional studies are needed to confirm these findings and localize specific causal variants.
Electronic supplementary material
The online version of this article (doi:10.1007/s10552-012-9947-4) contains supplementary material, which is available to authorized users.
doi:10.1007/s10552-012-9947-4
PMCID: PMC3390694  PMID: 22674224
Xenobiotic; Chemicals; California; Childhood cancer; Epidemiology
25.  Genetic polymorphisms in metabolizing enzymes modify the association between Smoking and Inflammatory Bowel Diseases 
Inflammatory bowel diseases  2014;20(5):783-789.
Introduction
Cigarette smoking is a well established environmental risk factor for Crohn's disease (CD) and ulcerative colitis (UC). The exact mechanism of its effect remains unexplained. Genetic polymorphisms in metabolizing enzymes may influence susceptibility to the effect of smoking and shed light on its mechanism of action.
Methods
We utilized a prospective cohort of patients with CD, UC, and healthy controls. Smoking status was defined as current, former, or never smoking. Patients were genotyped for polymorphisms in CYP2A6, glutathione transferase enzymes (GSTP1 and GSTM1), NAD(P)H quinone oxidoreductase (NQO), and Heme Oxygenase 1 using a Sequenom platform. Multivariate logistic regression models with CD or UC as the outcome, stratified by genotype were developed and interaction p-values calculated.
Results
Our study included 634 patients with CD, 401 with UC, and 337 healthy controls. Ever smokers had an increased risk of CD (OR 3.88, 95% CI 2.35 – 6.39) compared to non-smokers among patients with AG/AA genotypes at CYP2A6. However, ever smoking was not associated with CD among patients with the AA genotype (pinteraction 0.001). Former smoking was associated with an increased risk for UC only in the presence of GG/AG genotypes for GSTP1, but not in those with the AA genotype (Pinteraction 0.012). Polymorphisms at the NQO and HMOX loci did not demonstrate a statistically significant interaction with smoking and risk of CD or UC.
Conclusion
Genetic polymorphisms in metabolizing enzymes may influence the association between smoking and CD and UC. Further studies of gene-environment interaction in IBD are warranted.
doi:10.1097/MIB.0000000000000014
PMCID: PMC4113010  PMID: 24651583
ulcerative colitis; crohn's disease; smoking; genetics

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