N-acetyltransferase 2 (NAT2) genotypes, cigarette smoking, and the risk of breast cancer

Health effects associated with exposure to secondhand smoke: a Burden of Proof study

Despite a gradual decline in smoking rates over time, exposure to secondhand smoke (SHS) continues to cause harm to nonsmokers, who are disproportionately children and women living in low- and middle-income countries. We comprehensively reviewed the literature published by July 2022 concerning the adverse impacts of SHS exposure on nine health outcomes. Following, we quantified each exposure-response association accounting for various sources of uncertainty and evaluated the strength of the evidence supporting our analyses using the Burden of Proof Risk Function methodology. We found all nine health outcomes to be associated with SHS exposure. We conservatively estimated that SHS increases the risk of ischemic heart disease, stroke, type 2 diabetes and lung cancer by at least around 8%, 5%, 1% and 1%, respectively, with the evidence supporting these harmful associations rated as weak (two stars). The evidence supporting the harmful associations between SHS and otitis media, asthma, lower respiratory infections, breast cancer and chronic obstructive pulmonary disease was weaker (one star). Despite the weak underlying evidence for these associations, our results reinforce the harmful effects of SHS on health and the need to prioritize advancing efforts to reduce active and passive smoking through a combination of public health policies and education initiatives.

The impact of IDH and NAT2 gene polymorphisms in acute myeloid leukemia risk and overall survival in an Arab population: A case-control study

Acute myeloid leukemia (AML) is a malignancy of the myeloid cells due to the clonal and malignant proliferation of blast cells. The etiology of AML is complex and involves environmental and genetic factors. Such genetic aberrations include FLT3, DNMT3, IDH1, IDH2, NAT2, and WT. In this study, we analyzed the relationship between five, not previously studied in any Arab population, single nucleotide polymorphisms (SNPs) and the risk and overall survival of AML in Jordanian patients. The SNPs are NAT2 (rs1799930 and rs1799931), IDH1 (rs121913500), and IDH2 (rs121913502 and rs1057519736). A total number of 30 AML patients and 225 healthy controls were included in this study. Females comprised 50% (n = 15) and 65.3% (n = 147) of patients and controls, respectively. For AML patients (case group) Genomic DNA was extracted from formalin-fixed paraffin-embedded tissues and from peripheral blood samples for the control subjects group. Genotyping of the genetic polymorphisms was conducted using a sequencing protocol. Our study indicates that NAT2 rs1799930 SNP had a statistically significant difference in genotype frequency between cases and controls (p = 0.023) while IDH mutations did not correlate with the risk and survival of AML in the Jordanian population. These results were also similar in the TCGA-LAML cohorts with the notable exception of the rare NAT2 mutation. A larger cohort study is needed to further investigate our results.

The relationship between tobacco and breast cancer incidence: A systematic review and meta-analysis of observational studies

Background

The effect of tobacco on breast cancer (BC) is controversial. The purpose of this study was to investigate the relationship between tobacco and BC.

Methods

A search was conducted in PubMed, EBSCO, Web of Science and Cochrane Library databases before February 2022. The adjusted odd ratio (OR) and corresponding 95% confidence interval (CI) were used to examine the relationship between active or passive smoking and BC risk.

Results

A total of 77 articles composed of 2,326,987 participants were included for this meta-analysis. Active (OR=1.15, 95% CI=1.11-1.20, p<0.001) and passive (OR=1.17, 95% CI=1.09-1.24, p<0.001) smoking increased the risk of BC in the female population, especially premenopausal BC (active smoking: OR=1.24, p<0.001; passive smoking: OR=1.29, p<0.001), but had no effect on postmenopausal BC (active smoking: OR=1.03, p=0.314; passive smoking: OR=1.13, p=0.218). Active smoking increased the risk of estrogen receptor-positive (ER+) BC risk (OR=1.13, p<0.001), but had no effect on estrogen receptor-negative (ER-) BC (OR=1.08, p=0.155). The risk of BC was positively associated with the duration and intensity of smoking, negatively associated with the duration of smoking cessation. Active smoking increased the risk of BC in the multiparous population (OR=1.13, p<0.001), but had no effect on the nulliparous population (OR=1.05, p=0.432), and smoking before the first birth (OR=1.22, 95% CI=1.17-1.27) had a greater impact on the risk of BC than smoking after the first birth (OR=1.08, 95% CI=1.04-1.12).

Conclusion

Smoking (active and passive) increased the risk of BC in women. The effect of smoking on BC was influenced by smoking-related factors (duration, intensity, years of quitting), population-related factors (fertility status), and BC subtypes.

Systematic Review Registration

identifier CRD42022322699.

Passive smoking, NAT2 polymorphism, and breast cancer risk in Israeli Arab women: a case-control study

BACKGROUND

The effect of passive smoking (PS) on breast cancer (BC) is controversial, and may be modified by polymorphism of the N-Acetyl-transferase (NAT) 2 enzyme which is involved in tobacco carcinogen metabolism. We aimed to evaluate the relationship between PS and BC by NAT2 variants in Arab-Israeli women, a unique population with low active smoking rates, and high exposure to PS.

METHODS

A population-based case-control study was carried out on non-smoking 137 prevalent breast cancer patients and 274 population-based controls, aged 30-70 years. Data on past and current PS, sociodemographic, and other characteristics were retrieved through interviews, and buccal smears were provided for NAT2 analyses. Logistic regression models adjusting for potential confounders assessed the odds ratios (ORs) and 95% confidence intervals (95% CI) of the association between PS and BC.

RESULTS

Ever PS was associated with increased BC risk: OR = 2.22, 95% CI 1.28-3.87. Higher lifetime PS exposure was associated with higher BC risk: Compared to never exposed women, women exposed to PS most of their lives had a threefold higher BC risk (OR = 3.16, 95% CI 1.70-5.87, P _trend < 0.001). NAT2 polymorphism did not modify these associations.

CONCLUSIONS

PS exposure in non-smoking Israeli Arab women is significantly associated with increased risk for BC, potentially allowing for specific intervention; NAT2 polymorphism does not modify this association.

Environmental tobacco smoke exposure and risk of breast cancer in nonsmoking women. An updated review and meta-analysis

CONTEXT

In 2006, we reviewed the evidence on environmental tobacco smoke (ETS) and breast cancer in nonsmoking women. Since then various studies and reviews have been published but opinion remains divided.

OBJECTIVE

To provide an updated review.

METHODS

We extracted study details, derived relative risk (RR) estimates with confidence intervals (CIs) for various ETS exposure indices, and conducted meta-analyses.

RESULTS

The update increased the number of studies from 22 to 47. Using an index for each study most closely equivalent to "spouse ever smoked", a weak but significant association was seen (random-effects RR = 1.15, 95% CI = 1.07-1.23). However, the estimates were heterogeneous: higher for Asian studies than for North American or European studies, higher for studies adjusting for fewer potential confounding variables, and close to 1.0 for prospective studies, regardless of whether or not they asked detailed questions on ETS exposure. The RR for eight prospective studies asking detailed questions was 1.003, 95% CI = 0.96-1.05. Risk was increased in premenopausal women (RR = 1.36, 95% CI = 1.15-1.60), but not postmenopausal women. Dose-response findings were similarly heterogeneous. No significant increase was seen for childhood or workplace exposure, but an increase was seen for total exposure (RR = 1.22, 95% CI = 1.09-1.37).

CONCLUSIONS

Increases mainly derived from case-control studies are prone to recall bias. Study weaknesses and possible publication bias limit interpretation. Considering also the weak association of smoking with breast cancer, and the much lower exposures from ETS than from smoking, our analyses do not clearly demonstrate that ETS exposure increases risk of breast cancer in nonsmokers. More research is needed.

N-acetyltransferase 2 polymorphism and breast cancer risk with smoking: a case control study in Japanese women

BACKGROUND

Recent studies have suggested that the association between smoking and breast cancer risk might be modified by polymorphisms in the N-acetyltransferase 2 gene (NAT2). Most of these studies were conducted in Western countries, with few reports from East Asia.

METHODS

We conducted a case-control study of 511 breast cancer cases and 527 unmatched healthy controls from December 2010 to November 2011 in Japan. Unconditional logistic regression was used to analyze the association of smoking with breast cancer risk stratified by NAT2 phenotype.

RESULTS

In this population, 11 % of the cases and 10 % of the controls were classified as a slow acetylator phenotype. Compared to never smokers, current smokers had an increased breast cancer risk in multivariate analysis [odds ratio (OR) = 2.27, 95 % confidence interval (95 %CI) = 1.38-3.82]. Subgroup analyses of menopausal status indicated the same tendency. Subgroup analyses of NAT2 phenotype, the ORs in both of rapid and slow acetylator phenotype subgroups were comparable, and no interactions were observed between smoking status and NAT2 phenotype (p = 0.97). A dose-dependent effect of smoking on breast cancer risk was seen for the rapid acetylator phenotype, but not for the slow acetylator phenotype.

CONCLUSION

Given the high frequency of the rapid acetylator phenotype, these results show that smoking is a risk factor for breast cancer among most Japanese women. It may be of little significance to identify the NAT2 phenotype in the Japanese population.

Landscape of NAT2 polymorphisms among breast cancer

PURPOSE

The prevalence of phenotypes of Arylamine N-acetyltransferase-2(NAT2) gene (i.e. fast, intermediate and slow acetylators) among ethnic groups, as well as the association studies regarding NAT2 polymorphisms and risk of breast cancer produced inconsistent results. This meta-analysis aimed to clarify whether the selected NAT2 phenotypes have an effect on the susceptibility to breast cancer.

METHODS

After aggregating the frequencies of fast, intermediate and slow phenotypes of NAT2 in breast cancer subjects, the odds ratio and relevant 95% confidence intervals were examined using combined data from all published 36 articles.

RESULTS

Overall, our results did not produce statistical significance for the proposed association, suggesting that there is no association between the selected phenotypes of NAT2 polymorphisms and breast cancer. In subgroup analyses, it was revealed that, as compared with the fast phenotype, intermediate acetylator is protective of the vulnerable White population to breast cancer. In addition, an obvious ethnic/geographic difference was found in the prevalence of fast, intermediate and slow acetylators among world-wide populations.

CONCLUSIONS

Although ethnic and geographic differences in NAT2 polymorphisms were present, this was not associated with the risk of breast cancer in general. Intermediate acetylator is protective for particular ethnic groups, a finding which should be carefully viewed and confirmed in the future studies.

Passive cigarette smoke exposure during various periods of life, genetic variants, and breast cancer risk among never smokers

The association between passive cigarette smoke exposure and breast cancer risk is inconclusive and may be modified by genotype. The authors investigated lifetime passive cigarette smoke exposures, 36 variants in 12 carcinogen-metabolizing genes, and breast cancer risk among Ontario, Canada, women who had never smoked (2003-2004). DNA (saliva) was available for 920 breast cancer cases and 960 controls. Detailed information about passive smoke exposure was collected for multiple age periods (childhood, teenage years, and adulthood) and environments (home, work, and social). Adjusted odds ratios and 95% confidence intervals were estimated by multivariable logistic regression, and statistical interactions were assessed using the likelihood ratio test. Among postmenopausal women, most associations between passive smoke and breast cancer risk were null, whereas among premenopausal women, nonsignificant positive associations were observed. Significant interactions were observed between certain types of passive smoke exposure and genetic variants in CYP2E1, NAT2, and UGT1A7. While these interactions were statistically significant, the magnitudes of the effect estimates were not consistent or easily interpretable, suggesting that they were perhaps due to chance. Although the results of this study were largely null, it is possible that premenopausal women exposed to passive smoke or carrying certain genetic variants may be at higher risk of breast cancer.

Effects of single nucleotide polymorphisms on human N-acetyltransferase 2 structure and dynamics by molecular dynamics simulation

Background

Arylamine N-acetyltransferase 2 (NAT2) is an important catalytic enzyme that metabolizes the carcinogenic arylamines, hydrazine drugs and chemicals. This enzyme is highly polymorphic in different human populations. Several polymorphisms of NAT2, including the single amino acid substitutions R64Q, I114T, D122N, L137F, Q145P, R197Q, and G286E, are classified as slow acetylators, whereas the wild-type NAT2 is classified as a fast acetylator. The slow acetylators are often associated with drug toxicity and efficacy as well as cancer susceptibility. The biological functions of these 7 mutations have previously been characterized, but the structural basis behind the reduced catalytic activity and reduced protein level is not clear.

Methodology/Principal Findings

We performed multiple molecular dynamics simulations of these mutants as well as NAT2 to investigate the structural and dynamical effects throughout the protein structure, specifically the catalytic triad, cofactor binding site, and the substrate binding pocket. None of these mutations induced unfolding; instead, their effects were confined to the inter-domain, domain 3 and 17-residue insert region, where the flexibility was significantly reduced relative to the wild-type. Structural effects of these mutations propagate through space and cause a change in catalytic triad conformation, cofactor binding site, substrate binding pocket size/shape and electrostatic potential.

Conclusions/Significance

Our results showed that the dynamical properties of all the mutant structures, especially in inter-domain, domain 3 and 17-residue insert region were affected in the same manner. Similarly, the electrostatic potential of all the mutants were altered and also the functionally important regions such as catalytic triad, cofactor binding site, and substrate binding pocket adopted different orientation and/or conformation relative to the wild-type that may affect the functions of the mutants. Overall, our study may provide the structural basis for reduced catalytic activity and protein level, as was experimentally observed for these polymorphisms.

NAT2 polymorphisms combining with smoking associated with breast cancer susceptibility: a meta-analysis

To derive a more precise estimation of the relationship between the slow or rapid acetylation resulting from N-acetyltransferase 2 (NAT2) polymorphisms and breast cancer risk, a meta-analysis was performed. PubMed, Medline, Embase, and Web of Science were searched. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess strength of association. The pooled ORs were performed for slow versus rapid acetylation genotypes. A total of 26 studies including 9,215 cases and 10,443 controls were included in the meta-analysis. Overall, no significantly elevated breast cancer risk was associated with NAT2 slow genotypes when all studies were pooled into the meta-analysis (OR = 1.026, 95% CI = 0.968-1.087). In the subgroup analysis by ethnicity, increased risks were not found for either Caucasians (OR = 1.001, 95% CI = 0.938-1.068) or Asians (OR = 1.155, 95% CI = 0.886-1.506). When stratified by study design, statistically significantly elevated risk associated with NAT2 slow genotypes was only found among hospital-based studies (OR = 1.178, 95% CI = 1.037-1.339). In the subgroup analysis by menopausal status, no statistically significantly increased risk was found in either premenopausal (OR = 1.053, 95% CI = 0.886-1.252) or postmenopausal women (OR = 0.965, 95% CI = 0.844-1.104). When stratified by cumulative smoking exposure, in the subgroup of smokers with high pack-years, NAT2 slow genotypes were significantly associated with increased breast cancer risk (OR = 1.400, 95% CI = 1.099-1.784). In conclusion, this meta-analysis suggested that there is overall lack of association between NAT2 genotypes and breast cancer risk, however, NAT2 polymorphisms when combining with heavy smoking history may contribute to breast cancer susceptibility.

N-acetyltransferase 2 genotype modification of active cigarette smoking on breast cancer risk among hispanic and non-hispanic white women

While it has been demonstrated that cigarette smoke contains aromatic and heterocyclic amines that initiate carcinogenesis, the association between cigarette smoking and breast cancer remains controversial. N-acetyltransferase 2 (NAT2) catalyzes arylamine carcinogen biotransformation and NAT2 genetic polymorphisms may contribute to differential susceptibility to breast cancer. We tested whether NAT2 modified the association between cigarette smoking and breast cancer risk in a population-based study of Hispanic and non-Hispanic white women in the Southwest United States. Data were available for cigarette smoking and NAT2 polymorphisms for 717 cases (Hispanic, 251 and non-Hispanic white, 466) and 735 controls (Hispanic, 245 and non-Hispanic white, 490). NAT2 genotypes were translated into rapid, intermediate, slow, or very slow acetylator phenotypes. Odds ratios (ORs) and 95% confidence intervals (95% CIs) for the joint association of NAT2 with smoking on breast cancer risk were estimated using logistic regression. Non-Hispanic white women were more likely (p < 0.001) than Hispanic women to have a slow (41.7 vs. 33.5%) or very slow (19.0 vs. 11.1%) acetylator status and less likely to have rapid/intermediate phenotypes (39.2 vs. 54.4%). Breast cancer risk was significantly increased in non-Hispanic white women with a very slow acetylator phenotype who smoked: ever versus never (OR, 2.57; 95% CI, 1.49-4.41), never versus former (OR, 2.69; 95% CI, 1.41-5.17) or current (OR, 2.46; 95% CI, 1.07-5.65), and 16 + pack-years (OR, 2.29; 95% CI, 1.16-4.51). Results for Hispanic women were not statistically significant. These findings support smoking as a risk factor for breast cancer among non-Hispanic white women with very slow NAT2 acetylator phenotype.

Differences between human slow N-acetyltransferase 2 alleles in levels of 4-aminobiphenyl-induced DNA adducts and mutations

Aromatic amines such as 4-aminobiphenyl (ABP) require biotransformation to exert their carcinogenic effects. Genetic polymorphisms in biotransformation enzymes such as N-acetyltransferase 2 (NAT2) may modify cancer risk following exposure. Nucleotide excision repair-deficient Chinese hamster ovary (CHO) cells stably transfected with human cytochrome P4501A1 (CYP1A1) and a single copy of either NAT2*4 (rapid acetylator), NAT2*5B (common Caucasian slow acetylator), or NAT2*7B (common Asian slow acetylator) alleles (haplotypes) were treated with ABP to test the effect of NAT2 polymorphisms on DNA adduct formation and mutagenesis. ABP N-acetyltransferase catalytic activities were detectable only in cell lines transfected with NAT2 and were highest in cells transfected with NAT2*4, lower in cells transfected with NAT2*7B, and lowest in cells transfected with NAT2*5B. Following ABP treatment, N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-ABP) was the primary adduct formed. Cells transfected with both CYP1A1 and NAT2*4 showed the highest concentration-dependent cytotoxicity, hypoxanthine phosphoribosyl transferase (hprt) mutants, and dG-C8-ABP adducts. Cells transfected with CYP1A1 and NAT2*7B showed lower levels of cytotoxicity, hprt mutagenesis, and dG-C8-ABP adducts. Cells transfected with CYP1A1 only or cells transfected with both CYP1A1 and NAT2*5B did not induce cytotoxicity, hprt mutagenesis or dG-C8-ABP adducts. ABP-DNA adduct levels correlated very highly (r>0.96) with ABP-induced hprt mutant levels following each treatment. The results of the present study suggest that investigations of NAT2 genotype or phenotype associations with disease or toxicity could be more precise and reproducible if heterogeneity within the "slow" NAT2 acetylator phenotype is considered and incorporated into the study design.

Update on the pharmacogenetics of NATs: structural considerations

The arylamine N-acetyltransferase (NAT) genes encode enzymes that catalyze the N-acetylation of aromatic amines and hydrazines and the O-acetylation of heterocyclic amines. These genes, which play a key role in cellular homeostasis as well as in gene-environment interactions, are subject to marked pharmacogenetic variation, and different combinations of SNPs in the human NAT genes lead to different acetylation phenotypes. Our understanding of the consequences of pharmacogenetic variability in NATs has recently been enhanced by structural studies showing that effects on protein folding, aggregation and turnover, as well as direct changes in active site topology, are involved. These developments pave the way for a better understanding of the role played by NATs in maintaining cellular homeostasis. In addition, the NATs represent a model for studying fundamental processes associated with protein folding and pharmacogenomic effects mediated by inheritance in human populations across a polymorphic region of the genome.

Implication of Xenobiotic Metabolizing Enzyme gene (CYP2E1, CYP2C19, CYP2D6, mEH and NAT2) polymorphisms in breast carcinoma

Background

Xenobiotic Metabolizing Enzymes (XMEs) contribute to the detoxification of numerous cancer therapy-induced products. This study investigated the susceptibility and prognostic implications of the CYP2E1, CYP2C19, CYP2D6, mEH and NAT2 gene polymorphisms in breast carcinoma patients.

Methods

The authors used polymerase chain reaction and restriction enzyme digestion to characterize the variation of the CYP2E1, CYP2C19, CYP2D6, mEH and NAT2 gene in a total of 560 unrelated subjects (246 controls and 314 patients).

Results

The mEH (C/C) mutant and the NAT2 slow acetylator genotypes were significantly associated with breast carcinoma risk (p = 0.02; p = 0.01, respectively). For NAT2 the association was more pronounced among postmenopausal patients (p = 0.006). A significant association was found between CYP2D6 (G/G) wild type and breast carcinoma risk only in postmenopausal patients (p = 0.04). Association studies of genetic markers with the rates of breast carcinoma specific overall survival (OVS) and the disease-free survival (DFS) revealed among all breast carcinoma patients no association to DFS but significant differences in OVS only with the mEH gene polymorphisms (p = 0.02). In addition, the mEH wild genotype showed a significant association with decreased OVS in patients with axillary lymph node-negative patients (p = 0.03) and with decreasesd DFS in patients with axillary lymph node-positive patients (p = 0.001). However, the NAT2 intermediate acetylator genotype was associated with decreased DFS in axillary lymph node-negative patients.

Conclusion

The present study may prove that polymorphisms of some XME genes may predict the onset of breast carcinoma as well as survival after treatment.

A meta-analysis of the association of N-acetyltransferase 2 gene (NAT2) variants with breast cancer

The N-acetyltransferase 2 gene (NAT2) product is an enzyme important in carcinogen metabolism via activation and detoxification pathways. Therefore, NAT2 variants may represent underlying susceptibility to breast cancer. Because a number of studies of the association of NAT2 with breast cancer have been published, the authors performed a meta-analysis. They extracted all relevant data to examine evidence for a main effect (i.e., the effect in a model that does not include any interactions) of NAT2 phenotype and genotype on breast cancer risk. They summarized the evidence for modification by smoking and meat intake, sources of exposure to aromatic and heterocyclic amines, respectively, which are metabolized by NAT2. The authors identified seven studies that measured NAT2 phenotype and 20 studies that deduced phenotype via genotyping. They found no evidence for heterogeneity (Cochran's Q statistic p=0.74) and no statistically significant increased risk from NAT2 acetylation (slow/rapid) for breast cancer (summary odds ratio=1.02, 95% confidence interval: 0.95, 1.08). These results suggest that there is no overall association between the NAT2 slow- or rapid-acetylation phenotype and breast cancer risk. However, some evidence suggests that smoking may modify this association.

Association of CYP2E1 and NAT2 gene polymorphisms with chronic obstructive pulmonary disease

BACKGROUND

Detoxification genes are potential candidates in the susceptibility of patients with chronic obstructive pulmonary disease. Polymorphisms in these genes alter the metabolism of xenobiotics such as present in cigarette smoke.

METHODS

We conducted a case-control study to investigate total 9 polymorphisms of CYP2E1, CYP2D6 and NAT2 genes by PCR-RFLP.

RESULTS

The -1053C/T and -1293G/C promoter polymorphisms of CYP2E1 were found to be in complete linkage disequilibrium (LD) (D'=1.00, r(2)=1.0, p<0.0001), whereas -1293G/C and 7632T/A polymorphisms of the same gene were also in significant LD (D'=0.5183, r(2)=1.0, p=0.01) in patients. The patients over-represented the -1293GC+CC genotypes of -1293G/C polymorphism of CYP2E1 (p=0.03) and NAT2*4/7, NAT2()5/6, NAT2*5/7, NAT2*6/6 and NAT2*6/7 genotypes of NAT2 (p=0.01, p=0.039, p=0.01, p=0.032, p=0.006, respectively), resulting in to higher frequency of -1293C (OR=7.02, 95% CI=1.63-30.15, p=0.002), NAT2*6 (OR=1.90, 95% CI=1.27-2.83, p=0.001) and NAT2*7 (OR=2.91, 95% CI=1.65-5.12, p=0.0001) alleles. The 7632T/A and 9893C/G polymorphisms of CYP2E1 and 1934G/A polymorphism of CYP2D6 did not associate with the disease (p>0.05). The haplotypes -1293G:9893C and -1293G:7632T:9893C were under-represented (p<0.001), whereas haplotypes -1293C:7632T, -1293C:9893C, -1293C:9893G and -1293C:7632T:9893C of the 4 CYP2E1 polymorphisms were over-represented in patients (p<0.05).

CONCLUSION

The CYP2E1 and NAT2 variants associated with COPD.

Active and passive smoking, IL6, ESR1, and breast cancer risk

We evaluated the association between smoking and risk of breast cancer in non-Hispanic white (NHW) and Hispanic or American Indian (HAI) women living in the Southwestern United States. Data on lifetime exposure to active and passive smoke data were available from 1527 NHW cases and 1601 NHW controls; 798 HAI cases and 924 HAI controls. Interleukin 6 (IL6) and Estrogen Receptor alpha (ESR1) polymorphisms were assessed in conjunction with smoking. Pack-years of smoking (>or=15) were associated with increased risk of pre-menopausal breast cancer among NHW women (OR 1.6, 95% CI 1.1-2. 4). Passive smoke increased risk of pre-menopausal breast cancer for HAI women (OR 1.9, 95% CI 1.1-3.1 everyone; OR 2.3, 95% CI 1.2-4.5 nonsmokers). HAI pre-menopausal women who were exposed to 10+ h of passive smoke per week and had the rs2069832 IL6 GG genotype had over a fourfold increased risk of breast cancer (OR 4.4, 95% CI 1.5-12.8; P for interaction 0.01). Those with the ESR1 Xba1 AA genotype had a threefold increased risk of breast cancer if they smoked>or=15 pack-years relative to non-smokers (P interaction 0.01). These data suggest that breast cancer risk is associated with active and passive smoking.

Is the association between cigarette smoking and breast cancer modified by genotype? A review of epidemiologic studies and meta-analysis

Epidemiologic studies have examined the association between cigarette smoking and breast cancer risk according to genotype with increasing frequency, commensurate with the growing awareness of the roles genes play in detoxifying or activating chemicals found in cigarette smoke and in preventing or repairing the damage caused by those compounds. To date, approximately 50 epidemiologic studies have examined the association between smoking and breast cancer risk according to variation in genes related to carcinogen metabolism, modulation of oxidative damage, and DNA repair. Some of the findings presented here suggest possible effect modification by genotype. In particular, 14 epidemiologic studies have tended to show positive associations with long-term smoking among NAT2 slow acetylators, especially among postmenopausal women. Summary analyses produced overall meta-relative risk (RR) estimates for smoking of 1.2 [95% confidence interval (95% CI), 1.0-1.5] for rapid acetylators and 1.5 (95% CI, 1.2-1.8) for slow acetylators. After stratification by menopausal status, the meta-RR for postmenopausal slow acetylators was 2.4 (95% CI, 1.7-3.3), whereas similar analyses for the other categories showed no association. In addition, summary analyses produced meta-RRs for smoking of 1.1 (95% CI, 0.8-1.4) when GSTM1 was present and 1.5 (95% CI, 1.1-2.1) when the gene was deleted. Overall, however, interpretation of the available literature is complicated by methodologic limitations, including small sample sizes, varying definitions of smoking, and difficulties involving single nucleotide polymorphism selection, which likely have contributed to the inconsistent findings. These methodologic issues should be addressed in future studies to help clarify the association between smoking and breast cancer.

Tobacco smoking, NAT2 acetylation genotype and breast cancer risk

The role of active and passive cigarette smoking in breast cancer etiology remains controversial. Using data from a large population-based case-control study in Poland (2386 cases, 2502 controls) conducted during 2000-2003, we examined the associations between active and passive smoking overall and for different age categories. We also evaluated differences in risk by estrogen receptor (ER) and progesterone receptor (PR) status in tumors, and the potential modification of the smoking association by N-acetyl transferase 2 (NAT2) genotype. Women ever exposed to passive smoking at home or at work had a risk of breast cancer similar to those never exposed to active or passive smoking (OR (95%CI) = 1.11 (0.85-1.46), and no trends were observed with increasing hours/day-years of passive smoking exposure. Active smoking was associated with a significant increase in risk only among women younger than 45 years of age (OR (95%CI) = 1.95 (1.38-2.76); 1.15 (0.93-1.40); 0.91 (0.77-1.09) for < 45, 45-55 and > 55 years of age, respectively; p-heterogeneity < 0.001 for < 45 vs. > 55 years) and prevailed for both ER+ and ER- tumors. The smoking association among women < 45 years was stronger for current than former smokers, and a significant trend was observed with duration of smoking (p = 0.04). NAT2 slow vs. rapid/intermediate acetylation genotype was not related to breast cancer risk (0.99 (0.87-1.13)), and did not significantly modify the smoking relationships. In conclusion, our data indicate that passive smoking is not associated with breast cancer risk; however, active smoking might be associated with an increased risk for early onset breast cancers.

Flame-broiled food, NAT2acetylator phenotype, and breast cancer risk among women with benign breast disease

PURPOSE

The objective of this study was to examine the association between flame-broiled food consumption, a source of heterocyclic amine exposure, and the development of breast cancer among cohort of women with benign breast disease (BBD). The variation of the association by acetylation phenotype, as determined by the genotypes of selected N-acetyltransferase 2 (NAT2) enzymes, was also examined.

METHODS

Among participants in an ongoing cohort study, 1187 women reported having a breast biopsy for BBD and completed a food frequency questionnaire. NAT2 G857A, NAT2 T341C, and NAT2 G590A genotypes were determined using DNA extracted from blood specimens collected in 1989. Incident cases of breast cancer were identified through linkage of the cohort participants with the Washington County Cancer Registry and the Maryland State Cancer Registry. Follow-up for the BBD cohort began at study entry in 1989 and ended on April 28, 2003.

RESULTS

Of the women in this study, 77 subsequently developed breast cancer. Results showed that, among rapid acetylators, flame-broiled food intake was associated with a statistically significant increase in the risk of breast cancer (odds ratio (OR) 2.62; 95% confidence interval (CI) 1.06, 6.46). No association was observed between flame-broiled food intake and breast cancer among slow acetylators (OR 0.75; 95% CI 0.39, 1.43).

CONCLUSIONS

These findings suggest that flame-broiled food may be a modifiable risk factor for the progression of BBD to invasive breast cancer among women who have genotypes consistent with rapid acetylation.