Tobacco smoke carcinogens and breast cancer

Association between polycyclic aromatic hydrocarbons and periodontitis: Results from a large population-based study

AIM

To explore the association between polycyclic aromatic hydrocarbons (PAHs) (measured using urinary metabolites) and periodontitis using data from the National Health and Nutrition Examination Survey 2009-2014.

MATERIALS AND METHODS

Weighted binary logistic regression, Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS) regression were used to evaluate independent and joint associations between the six urinary monohydroxylated metabolites of PAHs (OH-PAHs) and periodontitis.

RESULTS

In all, 3413 participants were included in this study. All six urinary OH-PAHs were present at higher levels in the periodontitis group compared with the non-periodontitis group (p < .001). Fully adjusted multivariable logistic regressions showed positive associations between the six urinary OH-PAHs and periodontitis (p < .05). Higher concentrations of OH-PAHs were also positively associated with attachment loss, periodontal pocket depth (PPD) and the number of tooth loss. BKMR and WQS regression yielded similar positive associations between OH-PAH mixtures and periodontitis.

CONCLUSIONS

PAHs and their mixture are positively associated with periodontitis, which may provide novel insights into periodontitis prevention from an environmental exposure perspective.

Cancer Prevention and Treatment Based on Lifestyles

Cancer morbidity and mortality incidence are rapidly increasing over the period of time. Cancer prevention, alongside innovative therapies and earlier detection, is considered a key strategy for reducing the overall cancer burden. Substantial evidence indicates a clear correlation between lifestyle factors and changes in nutrient metabolism. Approximately 5-10% of all cancer cases are attributed to genetic factors, whereas 90-95% are due to environmental and lifestyle factors, suggesting that lifestyle interventions have significant prospects for preventing various cancers. Healthy lifestyle changes, in particular healthy diets, physical activity, staying at a healthy weight, reduction or elimination of tobacco/alcohol consumption, and avoiding exposure to radiation and other carcinogens, are significant factors to be considered to tackle the challenges associated with cancer in modern society. This chapter aims to provide lifestyle intervention strategies to improve cancer prevention and risk reduction while promoting the health of cancer patients. The therapeutic role of some dietary regimens and supplements, as well as complementary and alternative health approaches, in cancer treatment is also discussed.

The impact of endocrine disrupting compounds and carcinogens in wastewater: Implications for breast cancer

The incidence of breast cancer is often associated with geographic variation which indicates that a person's surrounding environment can be an important etiological factor in cancer development. Environmental risk factors can include exposure to sewage- or wastewater, which consist of a complex mixture of pathogens, mutagens and carcinogens. Wastewater contains primarily carbonaceous, nitrogenous and phosphorus compounds, however it can also contain trace amounts of chemical pollutants including toxic metal cations, hydrocarbons and pesticides. More importantly, the contamination of drinking water by wastewater is a potential source of exposure to mammary carcinogens and endocrine disrupting compounds. Organic solvents and other pollutants often found in wastewater have been detected in various tissues, including breast and adipose tissues. Furthermore, these pollutants such as phenolic compounds in some detergents and plastics, as well as parabens and pesticides can mimic estrogen. High estrogen levels are a well-established risk factor for estrogen-receptor (ER) positive breast cancer. Therefore, exposure to wastewater is a risk factor for the initiation, progression and metastasis of breast cancer. Carcinogens present in wastewater can promote tumourigenesis through various mechanisms, including the formation of DNA adducts, gene mutations and oxidative stress. Lastly, the presence of endocrine disrupting compounds in wastewater can have negative implications for ER-positive breast cancers, where these molecules can activate ERα to promote cell proliferation, survival and metastasis. As such, strategies should be implemented to limit exposure, such as providing funding into treatment technologies and implementation of regulations that limit the production and use of these potentially harmful chemicals.

The Association between Smoking and Mortality in Women with Breast Cancer: A Real-World Database Analysis

Smoking increases the cancer-specific and overall mortality risk in women with breast cancer (BC). However, the effect of smoking cessation remains controversial, and detailed research is lacking in Asia. We aimed to investigate the association between smoking status and mortality in women with BC using the population-based cancer registry. The Taiwan Cancer Registry was used to identify women with BC from 2011 to 2017. A total of 54,614 women with BC were enrolled, including 1687 smokers and 52,927 non-smokers. The outcome, mortality, was identified using Taiwan’s cause-of-death database. The association between smoking status and mortality was estimated using Cox proportional regression. Women with BC who smoked had a 1.25-fold higher (95% C.I.: 1.08–1.45; p = 0.0022) risk of overall mortality and a 1.22-fold higher (95% C.I.: 1.04–1.44; p = 0.0168) risk of cancer-specific mortality compared with non-smokers. The stratified analysis also indicated that women with BC who smoked showed a significantly higher overall mortality risk (HR: 1.20; 95% CI: 1.01–1.43; p = 0.0408) than women with BC who did not smoke among women without comorbidities. Additionally, current smokers had a 1.57-fold higher risk (95% CI: 1.02–2.42; p = 0.0407) of overall mortality compared with ever smokers among women with BC who smoked. It was shown that a current smoking status is significantly associated with an increase in overall and cancer-specific mortality risk in women with BC. Quitting smoking could reduce one’s mortality risk. Our results underscore the importance of smoking cessation for women with BC.

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&lt;0.001) and passive (OR=1.17, 95% CI=1.09-1.24, p&lt;0.001) smoking increased the risk of BC in the female population, especially premenopausal BC (active smoking: OR=1.24, p&lt;0.001; passive smoking: OR=1.29, p&lt;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&lt;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&lt;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.

Hexavalent chromium increases the metabolism and genotoxicity of aromatic amine carcinogens 4-aminobiphenyl and β-naphthylamine in immortalized human lung epithelial cells

Humans are exposed to carcinogenic chemicals via occupational and environmental exposures. Common chemicals of concern that can occur in exposures together are aromatic amines (e.g., 4-aminobiphenyl [4-ABP] and β-naphthylamine [BNA]) and hexavalent chromium (Cr[VI]). Arylamine N-acetyltransferases 1 and 2 (NAT1 and NAT2) are key to the metabolism of aromatic amines and their genotoxicity. The effects of Cr(VI) on the metabolism of aromatic amines remains unknown as well as how it may affect their ensuing toxicity. The objective of the research presented here is to investigate the effects of Cr(VI) on the metabolism and genotoxicity of 4-ABP and BNA in immortalized human lung epithelial cells (BEP2D) expressing NAT1 and NAT2. Exposure to Cr(VI) for 48 h increased NAT1 activity (linear regression analysis: P < 0.0001) as measured by N-acetylation of para-aminobenzoic acid (PABA) in BEP2D cells but not NAT2 N-acetylation of sulfamethazine, which are prototypic NAT1 and NAT2 substrates respectively. Cr(VI) also increased the N-acetylation of 4-ABP and BNA. In BEP2D cells the N-acetylation of 4-ABP (1-3 μM) exhibited a dose-dependent increase (linear regression analysis: P < 0.05) following co-incubation with 0-3 μM Cr(VI). In BEP2D cells, incubation with Cr(VI) caused dose-dependent increases (linear regression analysis: P < 0.01) in expression of CYP1A1 protein and catalytic activity. For genotoxicity, BEP2D cells were exposed to 4-ABP or BNA with/without Cr(VI) for 48 h. We observed dose-dependent increases (linear regression analysis: P < 0.01) in phospho-γH2AX protein expression for combined treatment of 4-ABP or BNA with Cr(VI). Further using a CYP1A1 inhibitor (α-naphthoflavone) and NAT1 siRNA, we found that CYP1A1 inhibition did not reduce the increased N-acetylation or genotoxicity of BNA by Cr(VI), while NAT1 inhibition did reduce increases in BNA N-acetylation and genotoxicity by Cr(VI). We conclude that during co-exposure of aromatic amines and Cr(VI) in human lung cells, Cr(VI) increased NAT1 activity contributing to increased 4-ABP and BNA genotoxicity.

Epigenetic Determinants of Racial Disparity in Breast Cancer: Looking beyond Genetic Alterations

Simple Summary

A substantial disparity in breast cancer incidence and mortality exists between African American (AA) and European American (EA) women. However, the basis for these disparities is poorly understood. In this article, we describe that gene–environment interactions mediated through epigenetic modifications may play a significant role in racial disparities in BC incidence and outcomes. Our in silico analyses and an in-depth literature survey suggest that there exists a significant difference in epigenetic patterns between AA and EA women with breast cancer. Herein, we describe the environmental factors that contribute to these epigenetic changes, which may underlie the disparate racial burden in patients with breast cancer. We suggest that AA women with higher basal epigenetic changes, may have higher pre-disposition to cancer onset, and an aggressive disease course. Pre-existing racial differences in epigenetic profiles of breast tissues raises the possibility of examining these profiles for early diagnosis.

Abstract

Breast cancer (BC) is the most commonly diagnosed cancer in women. Despite advancements in BC screening, prevention, and treatment, BC incidence and mortality remain high among African American (AA) women. Compared with European American (EA) women, AA women tend to be diagnosed with more advanced and aggressive tumors and exhibit worse survival outcomes. Most studies investigating the determinants of racial disparities in BC have focused on genetic factors associated with African ancestry. However, various environmental and social stressors over an individual’s life course can also shape racial stratification in BC. These social and environmental exposures result in long-term changes in gene expression mediated by epigenetic mechanisms. Epigenetics is often portrayed as an intersection of socially patterned stress and genetic expression. The enduring nature of epigenetic changes makes them suitable for studying the effects of different environmental exposures over an individual’s life course on gene expression. The role of differential social and environmental exposures in racial disparities in BC suggests varied epigenetic profiles or signatures associated with specific BC subtypes in AA and EA women. These epigenetic profiles in EA and AA women could be used as biomarkers for early BC diagnosis and disease prognosis and may prove valuable for the development of targeted therapies for BC. This review article discusses the current state of knowledge regarding epigenetic differences between AA and EA women with BC. We also discuss the role of socio-environmental factors, including psychosocial stress, environmental toxicants, and dietary factors, in delineating the different epigenetic profiles in AA and EA patients with BC.

Relationship between Cigarette Smoking and Cancer Characteristics and Survival among Breast Cancer Patients

Carcinogenic effects of tobacco smoke may affect breast tumorigenesis. To assess whether cigarette smoking is associated with breast cancer characteristics, we investigated the relationships between smoking, pathological characteristics, and outcomes in 2153 women diagnosed with breast cancer 2001-2016. Patients were classified as never, former, or current smokers at the time of diagnosis. Logistic regression and multivariable Cox proportional hazards analysis were performed to determine whether smoking was associated with tumor characteristics. Multivariable Cox proportional hazards analysis was conducted to compare former or current smokers to never smokers in survival with adjustment for the potential confounders. The majority of women (61.8%) never smoked, followed by former smokers (26.2%) and current smokers (12.0%). After adjustment for demographic variables, body mass index, and comorbidities, tumor characteristics were not significantly associated with smoking status or pack-years smoked. Ten-year overall survival was significantly lower for former and current smokers compared to never smokers (p = 0.0105). However, breast cancer specific survival did not differ significantly between groups (p = 0.1606). Although cigarette smoking did not alter the underlying biology of breast tumors or breast cancer-specific survival, overall survival was significantly worse in smokers, highlighting the importance of smoking cessation in the recently diagnosed breast cancer patient.

The Parallel Transformations of Polycyclic Aromatic Hydrocarbons in the Body and in the Atmosphere

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) emitted from combustion sources are known to be mutagenic, with more potent species also being carcinogenic. Previous studies show that PAHs can undergo complex transformations both in the body and in the atmosphere, yet these transformation processes are generally investigated separately.

OBJECTIVES

Drawing from the literature in atmospheric chemistry and toxicology, we highlight the parallel transformations of PAHs that occur in the atmosphere and the body and discuss implications for public health. We also examine key uncertainties related to the toxicity of atmospheric oxidation products of PAHs and explore critical areas for future research.

DISCUSSION

We focus on a key mode of toxicity for PAHs, in which metabolic processes (driven by cytochrome P450 enzymes), leads to the formation of oxidized PAHs that can damage DNA. Such species can also be formed abiotically in the atmosphere from natural oxidation processes, potentially augmenting PAH toxicity by skipping the necessary metabolic steps that activate their mutagenicity. Despite the large body of literature related to these two general pathways, the extent to which atmospheric oxidation affects a PAH's overall toxicity remains highly uncertain. Combining knowledge and promoting collaboration across both fields can help identify key oxidation pathways and the resulting products that impact public health.

CONCLUSIONS

Cross-disciplinary research, in which toxicology studies evaluate atmospheric oxidation products and their mixtures, and atmospheric measurements examine the formation of compounds that are known to be most toxic. Close collaboration between research communities can help narrow down which PAHs, and which PAH degradation products, should be targeted when assessing public health risks. https://doi.org/10.1289/EHP9984.

Joint effect of particulate matter and cigarette smoke on women's sex hormones

BACKGROUND

Although relationships between exposure to air pollution and reproductive health are broadly studied, mechanisms behind these phenomena are still unknown. The aim of the study was to assess whether exposure to particulate matter (PM10) and tobacco smoking have an impact on menstrual profiles of 17β-estradiol (E2) and progesterone (P) and the E2/P ratio.

METHODS

Levels of sex hormones were measured daily in saliva during the entire menstrual cycle among 132 healthy, urban women. Exposure to smoking (active or passive) was assessed by questionnaire, whilst exposure to PM10 with municipal monitoring data.

RESULTS

During the early luteal phase, profiles of E2 were elevated among women with higher versus lower exposure to PM10 (p = 0.02, post-hoc tests). Among those who were exposed versus unexposed to tobacco smoking, the levels of mean E2 measured during the entire cycle were higher (p = 0.02). The difference in mean E2 levels between the group of joint exposure (i.e. to high PM10 and passive or active smoking) versus the reference group (low PM10, no smoking) was statistically significant at p = 0.03 (18.4 vs. 12.4 pmol/l, respectively). The E2/P ratios were higher among women with higher versus lower exposure to PM10 and this difference was seen only in the early luteal phase (p = 0.01, exploratory post-hoc tests).

CONCLUSIONS

We found that PM10 and tobacco smoking affect ovarian hormones independently and do not interact with each other. Both exposures appear to have estrogenic effects even though women's susceptibility to these effects differs across the menstrual cycle. We propose that the hormonal mechanisms are involved in observed relationships between air pollution and smoking with women's reproductive health.

A Meta-Analysis of Induced Abortion, Alcohol Consumption, and Smoking Triggering Breast Cancer Risk among Women from Developed and Least Developed Countries

BACKGROUND

The most prominent form of cancer in women is breast cancer, and modifiable lifestyle risk factors, including smoking, alcohol consumption, and induced abortion, can all contribute significantly to this disease.

OBJECTIVES

This study's primary purpose was to assess the prevalence of breast cancer among women in developed and developing countries and the association between three modifiable hazard factors (induced abortion, smoking behavior, and alcohol use) and breast cancer.

METHODS

This study performed a systematic literature database review up to September 21, 2021. We employed meta-analytic tools such as the random effects model, forest plot, and subgroup analysis to conduct the research. Additionally, we conducted a sensitivity analysis to assess the influence of outliers.

RESULTS

According to the random effects model, smoker women have a higher risk of developing breast cancer from different countries (OR = 1.46; 95% CI: 1.08-1.97). In the case of induced abortion, the pooled estimate (OR = 1.25; 95% CI: 1.01-1.53) indicated a significant link between abortion and breast cancer. Subgroup analysis revealed that smoking substantially influences breast cancer in developing and developed countries. Breast cancer was more common among women who smoked in developed countries than in developing nations.

CONCLUSION

The observed findings give sufficient support for the hypothesis that smoking and abortion have a significant influence on breast cancer in different nations. Health organizations should individually design comprehensive scientific plans to raise awareness about the risks of abortion and smoking in developed and developing countries.

Can harmful lifestyle, obesity and weight changes increase the risk of breast cancer in BRCA 1 and BRCA 2 mutation carriers? A Mini review

Background and aim

The BRCA 1 and BRCA 2 genes are associated with an inherited susceptibility to breast cancer with a cumulative risk of 60% in BRCA 1 mutation carriers and of 30% in BRCA 2 mutation carriers. Several lifestyle factors could play a role in determining an individual’s risk of breast cancer. Obesity, changes in body size or unhealthy lifestyle habits such as smoking, alcohol consumption and physical inactivity have been evaluated as possible determinants of breast cancer risk. The aim of this study was to explore the current understanding of the role of harmful lifestyle and obesity or weight change in the development of breast cancer in female carriers of BRCA 1/2 mutations.

Methods

Articles were identified from MEDLINE in October 2020 utilizing related keywords; they were then read and notes, study participants, measures, data analysis and results were used to write this review.

Results

Studies with very large case series have been carried out but only few of them have shown consistent results. Additional research would be beneficial to better determine the actual role and impact of such factors.

Mendelian randomisation study of smoking exposure in relation to breast cancer risk

BACKGROUND

Despite a modest association between tobacco smoking and breast cancer risk reported by recent epidemiological studies, it is still equivocal whether smoking is causally related to breast cancer risk.

METHODS

We applied Mendelian randomisation (MR) to evaluate a potential causal effect of cigarette smoking on breast cancer risk. Both individual-level data as well as summary statistics for 164 single-nucleotide polymorphisms (SNPs) reported in genome-wide association studies of lifetime smoking index (LSI) or cigarette per day (CPD) were used to obtain MR effect estimates. Data from 108,420 invasive breast cancer cases and 87,681 controls were used for the LSI analysis and for the CPD analysis conducted among ever-smokers from 26,147 cancer cases and 26,072 controls. Sensitivity analyses were conducted to address pleiotropy.

RESULTS

Genetically predicted LSI was associated with increased breast cancer risk (OR 1.18 per SD, 95% CI: 1.07-1.30, P = 0.11 × 10-2), but there was no evidence of association for genetically predicted CPD (OR 1.02, 95% CI: 0.78-1.19, P = 0.85). The sensitivity analyses yielded similar results and showed no strong evidence of pleiotropic effect.

CONCLUSION

Our MR study provides supportive evidence for a potential causal association with breast cancer risk for lifetime smoking exposure but not cigarettes per day among smokers.

Different properties of mammary carcinogenesis induced by two chemical carcinogens, DMBA and PhIP, in heterozygous BALB/c Trp53 knockout mice

Chemical carcinogens, such as 7,12-dimethylbenz[a]anthracene (DMBA) and 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP), are known to induce mammary carcinomas in mice and rats. In the present study, the phenotypic and genotypic characteristics of carcinogen-induced mammary carcinogenesis in heterozygous BALB/c tumor protein p53 (Trp53) knockout mice were examined with reference to published data surrounding human breast cancer. A significantly accelerated induction of mammary carcinomas was observed following a single dose of DMBA (50 mg/kg of body weight at 7 weeks of age), and a modest acceleration was induced by PhIP (50 mg/kg of body weight) administered by gavage 6 times/2 weeks from 7 weeks of age. DMBA-induced mammary carcinomas were histopathologically characterized by distinct biphasic structures with luminal and myoepithelial cells, as well as a frequent estrogen receptor expression, and PhIP-induced carcinomas with solid/microacinar structures consisted of pleomorphic cells. Of note, DMBA-induced mammary carcinomas were characterized by a HRas proto-oncogene (Hras) mutation at codon 61, and gene/protein expression indicating MAPK stimulation. PhIP-induced lesions were suspected to be caused by different molecular mechanisms, including Wnt/β-catenin signaling and/or gene mutation-independent PI3K/AKT signaling activation. In conclusion, the present mouse mammary carcinogenesis models, induced by a combination of genetic and exogenous factors, may be utilized (such as the DMBA-induced model with Trp53 gene function deficiency as a model of adenomyoepithelioma, characterized by distinct biphasic cell constituents and Hras mutations), but PhIP-induced models are required to further analyze the genetic/epigenetic mechanisms promoting mammary carcinomas.

The use of tocofersolan as a rescue agent in larval zebrafish exposed to benzo[a]pyrene in early development

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants created by incomplete combustion. Benzo(a)pyrene (BaP), the prototypic PAH, is known to exert toxicity through oxidative stress which is thought to occur through inhibition of antioxidant scavenging systems. The use of agents that reduce oxidative stress may be a valuable route for ameliorating the adverse effects of PAHs on neural development and behavior. This study was conducted to determine if tocofersolan (a synthetic water-soluble analog of vitamin E) supplementation can prevent or reduce neurobehavioral deficits in zebrafish embryos exposed to BaP during early development. Newly hatched zebrafish were assessed on locomotor activity and light responsivity. Zebrafish embryos were exposed to vehicle (DMSO), tocofersolan (0.3 μM-3 μM), and/or BaP (5 μM) from 5-120 hours post-fertilization. This concentration range was below the threshold for producing overt dysmorphogenesis or decreased survival. One day after the end of exposure the larval fish were tested for locomotor activity under alternating light and dark 10 min periods, BaP (5 μM) was found to cause locomotor hypoactivity in larval fish. Co-exposure of tocofersolan (1 μM) restored control-like locomotor function. Based on the findings of this study, this model can be expanded to assess the outcome of vitamin E supplementation on other potential environmental neurotoxicants, and lead to determination if this rescue persists into adulthood.

Cigarette Smoking and Estrogen-Related Cancer

Cigarette smoking is a known cause of many cancers, yet epidemiologic studies have found protective associations with the risk of four "estrogen-related" malignancies: endometrial cancer, endometrioid and clear cell ovarian cancers, and thyroid cancer. This review considers epidemiologic and biological aspects of these associations, focusing particularly on estrogen signaling, and contrasts them with those for breast cancer, another estrogen-related malignancy. The observational findings regarding the inverse associations are consistent and remain after adjustment for possible confounding factors. In general, women who smoke do not have lower circulating estrogen levels than nonsmokers, eliminating one possible explanation for reduced risks of these malignancies. For endometrial and endometrioid ovarian cancer, the negative associations could plausibly be explained by interference with signaling through the estrogen receptor α. However, this is unlikely to explain the lower risks of thyroid and clear cell ovarian cancers. For thyroid cancer, an anti-inflammatory effect of nicotine and reduced TSH levels from smoking have been proposed explanations for the inverse association, but both lack convincing evidence. While the overall impact of cigarette smoking is overwhelmingly negative, protective associations such as those discussed here can provide potential clues to disease etiology, treatment, and prevention.

Causal Effects of Lifetime Smoking on Breast and Colorectal Cancer Risk: Mendelian Randomization Study

BACKGROUND

Observational evidence has shown that smoking is a risk factor for breast and colorectal cancer. We used Mendelian randomization (MR) to examine causal associations between smoking and risks of breast and colorectal cancer.

METHODS

Genome-Wide Association Study summary data were used to identify genetic variants associated with lifetime amount of smoking (n = 126 variants) and ever having smoked regularly (n = 112 variants). Using two-sample MR, we examined these variants in relation to incident breast (122,977 cases/105,974 controls) and colorectal cancer (52,775 cases/45,940 controls).

RESULTS

In inverse-variance weighted models, a genetic predisposition to higher lifetime amount of smoking was positively associated with breast cancer risk [OR per 1-SD increment: 1.13; 95% confidence interval (CI): 1.00-1.26; P = 0.04]; although heterogeneity was observed. Similar associations were found for estrogen receptor-positive and estrogen receptor-negative tumors. Higher lifetime amount of smoking was positively associated with colorectal cancer (OR per 1-SD increment, 1.21; 95% CI, 1.04-1.40; P = 0.01), colon cancer (OR, 1.31; 95% CI, 1.11-1.55; P < 0.01), and rectal cancer (OR, 1.36; 95% CI, 1.07-1.73; P = 0.01). Ever having smoked regularly was not associated with risks of breast (OR, 1.01; 95% CI, 0.90-1.14; P = 0.85) or colorectal cancer (OR, 0.97; 95% CI, 0.86-1.10; P = 0.68).

CONCLUSIONS

These findings are consistent with prior observational evidence and support a causal role of higher lifetime smoking amount in the development of breast and colorectal cancer.

IMPACT

The results from this comprehensive MR analysis indicate that lifetime smoking is a causal risk factor for these common malignancies.

Epidemiology of Triple-Negative Breast Cancer: A Review

ABSTRACT

Triple-negative breast cancer accounted for 12% of breast cancers diagnosed in the United States from 2012 to 2016, with a 5-year survival 8% to 16% lower than hormone receptor-positive disease. However, preventive and screening strategies remain tailored to the demographics of less lethal luminal cancers. This review examines the ethnic, genetic, and modifiable risk factors associated with triple-negative breast cancer, which providers must recognize to address the societal disparities of this deadly disease. Most notable is that triple-negative cancers disproportionately affect African American women and carriers of germline BRCA and PALB2 mutations. Even controlling for treatment delays, stage, and socioeconomic factors, African Americans with triple-negative breast cancer remain nearly twice as likely to die of their disease. To level the playing field, we must integrate genomic predictors of disease and epidemiologic characteristics of molecular breast cancer subtypes to provide personalized risk assessment, screening, and treatment for each patient.

Study on the AhR signaling pathway and phase II detoxification metabolic enzymes isoforms in scallop Chlamys farreri exposed to single and mixtures of PAHs

This study aimed to investigate the detoxification metabolism responses in scallop Chlamys farreri exposed to phenanthrene (PHE), chrysene (CHR), benzo[a]pyrene (B[a]P) and PHE + CHR + B[a]P for 15 days under laboratory conditions. The mRNA expression levels of AhR signaling pathway (AhR, HSP90, XAP2 and ARNT), detoxification system (phase I: CYP1A1 and CYP1B1; phase II: SULTs, UGT and GSTs) and ATP-binding cassette transporters (phase 0: ABCB1 and phase III: ABCC1, ABCG2) in digestive glands of scallops exposed to PHE (0.7, 2.1 μg/L), CHR (0.7, 2.1 μg/L), B[a]P (0.7, 2.1 μg/L), and PHE + CHR + B[a]P (0.7 + 0.7 +0.7, 2.1 + 2.1 + 2.1 μg/L) were detected. In present study, key genes (AhR, HSP90, XAP2 and ARNT) of the AhR signaling pathway can be significantly induced by pollutants, suggesting that the AhR/ARNT signaling pathway plays a role directly or indirectly. AhR, HSP90 and ARNT reached the maximum value on day 6, which can be preliminarily understood as the synchronization of their functions. Besides, the results also indicated that different genes had specific response to different pollution exposure. CYP1B1, GST-2, GST-omega and GST-microsomal could be potional indexes to PHE, ARNT, GST-sigma 2 and GST-3 were sensitive to CHR exposure, HSP90, GST-theta and ABCG2 were considered as potional indexes to BaP while CYP1A1 and UGT were possible to be indexes for monitoring the mix exposure of these three PAHs. These findings in C. farreri suggested that phase II detoxification metabolic enzymes isoforms played an essential role in detoxification mechanisms and mRNA expression levels of specific SULTs, UGTs and GSTs were potentially to be ideal indexes in PAHs pollution research. In summary, this study provides more valuable information for the risk assessments of different rings of PAHs.

The association between cigarette smoking, cancer screening, and cancer stage: a prospective study of the women's health initiative observational cohort

OBJECTIVE

To assess the dose-dependent relationship between smoking history and cancer screening rates or staging of cancer diagnoses.

DESIGN

Prospective, population-based cohort study.

SETTING

Questionnaire responses from the Women's Health Initiative (WHI) Observational Study.

PARTICIPANTS

89 058 postmenopausal women.

OUTCOME MEASURES

Logistic regression models were used to assess the odds of obtaining breast, cervical, and colorectal cancer screening as stratified by smoking status. The odds of late-stage cancer diagnoses among patients with adequate vs inadequate screening as stratified by smoking status were also calculated.

RESULTS

Of the 89 058 women who participated, 52.8% were never smokers, 40.8% were former smokers, and 6.37% were current smokers. Over an average of 8.8 years of follow-up, current smokers had lower odds of obtaining breast (OR 0.55; 95% CI 0.51 to 0.59), cervical (OR 0.53; 95% CI 0.47 to 0.59), and colorectal cancer (OR 0.71; 95% CI 0.66 to 0.76) screening compared with never smokers. Former smokers were more likely than never smokers to receive regular screening services. Failure to adhere to screening guidelines resulted in diagnoses at higher cancer stages among current smokers for breast cancer (OR 2.78; 95% CI 1.64 to 4.70) and colorectal cancer (OR 2.26; 95% CI 1.01 to 5.05).

CONCLUSIONS

Active smoking is strongly associated with decreased use of cancer screening services and more advanced cancer stage at the time of diagnosis. Clinicians should emphasise the promotion of both smoking cessation and cancer screening for this high-risk group.

Long-Term Exposure of Early-Transformed Human Mammary Cells to Low Doses of Benzo[a]pyrene and/or Bisphenol A Enhances Their Cancerous Phenotype via an AhR/GPR30 Interplay

It is of utmost importance to decipher the role of chronic exposure to low doses of environmental carcinogens on breast cancer progression. The early-transformed triple-negative human mammary MCF10AT1 cells were chronically (60 days) exposed to low doses (10⁻¹⁰ M) of Benzo[a]pyrene (B[a]P), a genotoxic agent, and/or Bisphenol A (BPA), an endocrine disruptor. Our study revealed that exposed MCF10AT1 cells developed, in a time-dependent manner, an acquired phenotype characterized by an increase in cancerous properties (anchorage independent growth and stem-like phenotype). Co-exposure of MCF10AT1 cells to B[a]P and BPA led to a significantly greater aggressive phenotype compared to B[a]P or BPA alone. This study provided new insights into the existence of a functional interplay between the aryl hydrocarbon receptor (AhR) and the G protein-coupled receptor 30 (GPR30) by which chronic and low-dose exposure of B[a]P and/or BPA fosters the progression of MCF10AT1 cells into a more aggressive substage. Experiments using AhR or GPR30 antagonists, siRNA strategies, and RNAseq analysis led us to propose a model in which AhR signaling plays a “driver role” in the AhR/GPR30 cross-talk in mediating long-term and low-dose exposure of B[a]P and/or BPA. Retrospective analysis of two independent breast cancer cohorts revealed that the AhR/GPR30 mRNA expression signature resulted in poor breast cancer prognosis, in particular in the ER-negative and the triple-negative subtypes. Finally, the study identified targeting AhR and/or GPR30 with specific antagonists as a strategy capable of inhibiting carcinogenesis associated with chronic exposure to low doses of B[a]P and BPA in MCF10AT1 cells. Altogether, our results indicate that the engagement of both AhR and GPR30 functions, in particular in an ER-negative/triple-negative context of breast cells, favors tumor progression and leads to poor prognosis.

The effect of smoking on biological change of recurrent breast cancer

BACKGROUND

The selection of treatment for a patient with breast cancer largely relies on the cancer subtype. However, this process is complicated by changes in tumor biology at relapse. Smoking has been identified as a risk factor for breast cancer. The direct effect of a tobacco component delivered via blood circulation on the mammary gland tissue and subsequent DNA damage have been proposed to explain the association between cigarette smoking and breast cancer carcinogenesis. This postulation is supported by both tissue culture and animal studies demonstrating that the associated DNA damage further alters breast cancer cells, as indicated by an increased proliferative capacity and malignant transformation. In this study, we aimed to explore the relationship between changes in Estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2) each receptor at recurrence, and smoking and the prognosis after recurrence.

METHODS

This retrospective study included 989 patients with primary breast cancer who developed relapse after surgery and 50 patients who underwent regenerative biopsy or surgery from December 2007 to March 2018. ER, PgR, and HER2 expression in the primary and recurrent lesions was evaluated using immunohistochemistry, and the correlations of these expression patterns with smoking history (pack-years) were examined.

RESULTS

When ER was evaluated in recurrent tumors, negative and positive conversions were recognized in 3 (6.0%) and 1 patient (2.0%), respectively. When PgR was evaluated, negative conversion was recognized in 15 patients (30.0%). When HER2 was evaluated, positive conversion was recognized in 6 patients (12.0%). Consequently, we observed a change in the intrinsic subtype in in 5 patients with recurrent tumors (10.0%). Although most clinical factors were not correlated with smoking, a positive conversion of HER2 in recurrence was significantly more frequent among smokers than among non-smokers (p = 0.024).

CONCLUSIONS

Biological changes during breast cancer recurrence should be given careful clinical consideration because they affect treatment after recurrence. Our results suggest that smoking may induce increased HER2 expression in recurrent breast tumors.

Investigation of Precise Molecular Mechanistic Action of Tobacco-Associated Carcinogen `NNK´ Induced Carcinogenesis: A System Biology Approach

Cancer is the second deadliest disease listed by the WHO. One of the major causes of cancer disease is tobacco and consumption possibly due to its main component, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). A plethora of studies have been conducted in the past aiming to decipher the association of NNK with other diseases. However, it is strongly linked with cancer development. Despite these studies, a clear molecular mechanism and the impact of NNK on various system-level networks is not known. In the present study, system biology tools were employed to understand the key regulatory mechanisms and the perturbations that will happen in the cellular processes due to NNK. To investigate the system level influence of the carcinogen, NNK rewired protein–protein interaction network (PPIN) was generated from 544 reported proteins drawn out from 1317 articles retrieved from PubMed. The noise was removed from PPIN by the method of modulation. Gene ontology (GO) enrichment was performed on the seed proteins extracted from various modules to find the most affected pathways by the genes/proteins. For the modulation, Molecular COmplex DEtection (MCODE) was used to generate 19 modules containing 115 seed proteins. Further, scrutiny of the targeted biomolecules was done by the graph theory and molecular docking. GO enrichment analysis revealed that mostly cell cycle regulatory proteins were affected by NNK.

Correlation of Internal Exposure Levels of Polycyclic Aromatic Hydrocarbons to Methylation of Imprinting Genes of Sperm DNA

Human exposure to polycyclic aromatic hydrocarbons (PAHs) results in adverse health implications. However, the specific impact of paternal preconception PAHs exposure has not been fully studied. In this study, a total of 219 men aged 24-53 were recruited and an investigation was conducted using a questionnaire requesting information about age, occupation, education, family history, lifestyle, and dietary preferences. Urine and semen samples were examined for the levels of the hydroxyl metabolites of PAHs (OH-PAHs) using ultra-high-performance liquid chromatography-tandem mass spectrometry and sperm DNA methylation by pyrosequencing. The results from the correlation analysis using seven OH-PAHs and the average methylation levels of the imprinting genes H19, PEG3, and MEG3 indicated that 1-OHPH is positively correlated with H19/PEG3 methylation levels. We further examined the correlation between each OH-PAH and the methylation levels at the individual CpGs. The results showed 1-OHPH is specifically correlated with CpG4 and CpG6 of the imprinted gene H19, CpG1 and CpG2 of PEG3, and CpG2 of MEG3; whereas 1-OHP is positively correlated with PEG3 at CpG1. Multivariate regression model analysis confirmed that 1-OHPH and 1-OHP are independent risk factors for the methylation of H19. These data show that sperm DNA imprinting genes are sensitive to adverse environmental perturbations.

Active and secondhand smoke exposure throughout life and DNA methylation in breast tumors

PURPOSE

Tobacco smoke exposure has been associated with altered DNA methylation. However, there is a paucity of information regarding tobacco smoke exposure and DNA methylation of breast tumors.

METHODS

We conducted a case-only analysis using breast tumor tissue from 493 postmenopausal and 225 premenopausal cases in the Western New York Exposures and Breast Cancer (WEB) study. Methylation of nine genes (SFN, SCGB3A1, RARB, GSTP1, CDKN2A, CCND2, BRCA1, FHIT, and SYK) was measured with pyrosequencing. Participants reported their secondhand smoke (SHS) and active smoking exposure for seven time periods. Unconditional logistic regression was used to estimate odds ratios (OR) of having methylation higher than the median.

RESULTS

SHS exposure was associated with tumor DNA methylation among postmenopausal but not premenopausal women. Active smoking at certain ages was associated with increased methylation of GSTP1, FHIT, and CDKN2A and decreased methylation of SCGB3A1 and BRCA1 among both pre- and postmenopausal women.

CONCLUSION

Exposure to tobacco smoke may contribute to breast carcinogenesis via alterations in DNA methylation. Further studies in a larger panel of genes are warranted.

Clinical verification of the relationship between smoking and the immune microenvironment of breast cancer

Background

The immune tumor microenvironment (iTME) is thought to affect the response to chemotherapy, and tumor-infiltrating lymphocytes (TILs) are often used as an indicator to evaluate the iTME. Smoking is involved in carcinogenesis, the relationship between smoking and the iTME of lung cancer has been reported. We hypothesized that smoking would affect the iTME of breast cancer and aimed to examine this relationship based on the amount of pre-diagnosis smoking and the subsequent effects on treatment response and prognosis.

Methods

This retrospective study evaluated data from 149 patients who underwent preoperative chemotherapy for triple-negative or HER2-enriched breast cancer. TILs were assessed in biopsy specimens at diagnosis. The data of all patients were used to calculate each patient’s smoking amount based on pack-years.

Results

Relative to the low smoking group, the high smoking group had a significant greater TILs density (p = 0.043) and a significantly better pathological complete response (pCR) rate (p = 0.042). However, there was no significant difference according to smoking amount in disease-free survival (p = 0.114) or overall survival (p = 0.347).

Conclusions

Smoking may influence the iTME, with an activated iTME being associated with pCR rate. Therefore, controlled activation of the microenvironment in this setting may help improve patients’ prognosis.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1773-y) contains supplementary material, which is available to authorized users.

Bioinformatics analysis of microarray profiling identifies the mechanism of focal adhesion kinase signalling pathway in proliferation and apoptosis of breast cancer cells modulated by green tea polyphenol epigallocatechin 3-gallate

OBJECTIVES

This study aimed to investigate potential gene and signal pathway associated with tumour progression.

METHODS

Related microarray data set of breast cancer was obtained from Gene Expression Omnibus database, and differential-expressed genes (DEGs) between two control samples and two treated samples were analysed using statistical software R. We collected 50 epigallocatechin-3-gallate(EGCG)-related genes and 119 breast cancer-related genes to create a knowledge base for following pathway analysis.

KEY FINDINGS

A total of 502 mRNAs were identified as DEGs based on microarray analysis. Upregulated DEGs mainly enriched in nuclear nucleosome, cell adhesion, DNA packaging complex, Wnt-activated receptor activity, etc., while the downregulated DEGs significantly enriched in ncRNA processing, mitotic nuclear division, DNA helicase activity, etc. DEGs mostly enriched in gap junction, cell cycle, oxidative phosphorylation, focal adhesion, etc. EGCG suppressed FAK signalling pathway. Furthermore, EGCG could inhibit breast cancer cell proliferation and promote apoptosis by modulating CCND1.

CONCLUSIONS

Epigallocatechin 3-gallate might exert influence on breast cancer progression through inhibiting focal adhesion kinase (FAK) signalling pathway.

Differential Expression of RAGE, EGFR and Ki-67 in Primary Tumors and Lymph Node Deposits of Breast Carcinoma

Background:

Breast cancer is a complex disease that results from the inheritance of a number of susceptible genes. Intensive search wok was conducted world-wide on molecular bases of breast cancer in order to achieve the best therapeutic modalities; however, breast cancer still remains a challengeable task. It is very important to determine if the biological parameters in metastatic regional lymph nodes are similar to that in the primary breast cancer because therapy is indicated for patients with synchronous metastatic regional lymph nodes of breast cancer. Difference in therapeutic response in cases of breast cancer may be assumed partially to variability in the biological behavior of tumor tissue in primary breast cancer and lymph node metastasis.

Aim:

Our aim is to evaluate any variability in the expression of three types of tissue markers in both the primary breast tumors and corresponding axillary lymph nodes in order to expect the targeted therapeutic effect on both sites.

Material and Methods:

Three markers from different categories; RAGE, EGFR and Ki-67 were immunohistochemicalyl studied for their expression in biopsy specimens from primary breast tumors and their corresponding axillary lymph nodes.

Results:

There was a statistically significant difference in the expression of these markers between benign and malignant breast lesions. Although we found some differences in the expression of the three studied markers between primary breast cancer and corresponding axillary lymph nodes, yet these variations were mostly not statistically significant.

Conclusion:

Our findings support the validity of anti-RAGE and anti-EGFR therapy for treatment of both primary and nodal metastatic breast cancer in immunopositive cases.

Loss of HIF-1α in macrophages attenuates AhR/ARNT-mediated tumorigenesis in a PAH-driven tumor model

Activation of hypoxia-inducible factor (HIF) and macrophage infiltration of solid tumors independently promote tumor progression. As little is known how myeloid HIF affects tumor development, we injected the polycyclic aromatic hydrocarbon (PAH) and procarcinogen 3-methylcholanthrene (MCA; 100 μg/100 μl) subcutaneously into myeloid-specific Hif-1α and Hif-2α knockout mice (C57BL/6J) to induce fibrosarcomas (n = 16). Deletion of Hif-1α but not Hif-2α in macrophages diminished tumor outgrowth in the MCA-model. While analysis of the tumor initiation phase showed comparable inflammation after MCA-injection, metabolism of MCA was impaired in the absence of Hif-1α. An ex vivo macrophage/fibroblast coculture recapitulated reduced DNA damage after MCA-stimulation in fibroblasts of cocultures with Hif-1α^LysM−/− macrophages compared to wild type macrophages. A loss of myeloid Hif-1α decreased RNA levels of arylhydrocarbon receptor (AhR)/arylhydrocarbon receptor nuclear translocator (ARNT) targets such as Cyp1a1 because of reduced Arnt but unchanged Ahr expression. Cocultures using Hif-1α^LysM−/− macrophages stimulated with the carcinogen 7,12-dimethylbenz[a]anthracene (DMBA; 2 μg/ml) also attenuated a DNA damage response in fibroblasts, while the DNA damage-inducing metabolite DMBA-trans-3,4-dihydrodiol remained effective in the absence of Hif-1α. In chemical-induced carcinogenesis, HIF-1α in macrophages maintains ARNT expression to facilitate PAH-biotransformation. This implies a metabolic activation of PAHs in stromal cells, i.e. myeloid-derived cells, to be crucial for tumor initiation.

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.

Pooled analysis of active cigarette smoking and invasive breast cancer risk in 14 cohort studies

Background

The 2014 US Surgeon General's report noted research gaps necessary to determine a causal relationship between active cigarette smoking and invasive breast cancer risk, including the role of alcohol consumption, timing of exposure, modification by menopausal status and heterogeneity by oestrogen receptor (ER) status.

Methods

To address these issues, we pooled data from 14 cohort studies contributing 934 681 participants (36 060 invasive breast cancer cases). Cox proportional hazard regression models were used to calculate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

Results

Smoking duration before first birth was positively associated with risk ( P -value for trend = 2 × 10 -7 ) with the highest HR for initiation >10 years before first birth (HR = 1.18, CI 1.12-1.24). Effect modification by current alcohol consumption was evident for the association with smoking duration before first birth ( P -value=2×10 -4 ); compared with never-smoking non-drinkers, initiation >10 years before first birth was associated with risk in every category of alcohol intake, including non-drinkers (HR = 1.15, CI 1.04-1.28) and those who consumed at least three drinks per day (1.85, 1.55-2.21). Associations with smoking before first birth were limited to risk of ER+ breast cancer ( P -value for homogeneity=3×10 -3 ). Other smoking timing and duration characteristics were associated with risk even after controlling for alcohol, but were not associated with risk in non-drinkers. Effect modification by menopause was not evident.

Conclusions

Smoking, particularly if initiated before first birth, was modestly associated with ER+ breast cancer risk that was not confounded by amount of adult alcohol intake. Possible links with breast cancer provide additional motivation for young women to not initiate smoking.

Breast cancer and exposure to tobacco smoke during potential windows of susceptibility

PURPOSE

An association between smoking and breast cancer is unresolved, although a higher risk from exposure during windows of susceptibility has been proposed. The objective of this prospective study was to evaluate the association between tobacco smoke and breast cancer with a focus on timing of exposure, especially during early life.

METHODS

Sister study participants (n = 50,884) aged 35-74 were enrolled from 2003 to 2009. Women in the United States and Puerto Rico were eligible if they were breast cancer-free but had a sister with breast cancer. Participants completed questionnaires on smoking and environmental tobacco smoke (ETS) exposure. Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for breast cancer risk.

RESULTS

During follow-up (mean = 6.4 years), 1,843 invasive breast cancers were diagnosed. Neither active smoking nor adult ETS was associated with breast cancer risk. However, never smoking women exposed to ETS throughout their childhood had a 17% higher risk of breast cancer (95% CI 1.00-1.36) relative to those with no exposure. In utero ETS exposure was also associated with breast cancer (HR = 1.16, 95% CI 1.01-1.32) and the HR was most elevated for women born in earlier birth cohorts (<1940, HR = 1.44, 95% CI 1.02-2.02; 1940-1949, HR = 1.28, 95% CI 1.01-1.62).

CONCLUSION

In utero ETS and ETS exposure during childhood and adolescence were associated with increased risk of breast cancer and associations varied by birth cohort.

Smoking Behavior and Smoke Constituents from Cigarillos and Little Cigars

OBJECTIVE

Although most cigarillos and little cigars smokers also smoke cigarettes (dual use), there are few studies comparing toxicant exposure and smoking behavior in cigars and cigarettes.

METHODS

Two groups of dual users smoked their usual brand of cigarette and either a Winchester unflavored little cigar (N = 21) or a Black & Mild cigarillo (N = 23). Acute exposure of nicotine and exhaled carbon monoxide (CO) and puffing topography parameters were collected. Individual cigar puffing data were used to machine-replicate smoking for analysis of volatile organic compounds (VOC) and semi-volatile organic compounds (SVOC) in mainstream smoke.

RESULTS

There were significant differences in puff topography, plasma nicotine and exhaled CO after cigarettes, little cigars, and cigarillos. Puff topography differences between cigarillos and cigarettes were due to the difference in the size of the article. Mainstream cigar and cigarette smoke was qualitatively similar; the yield was dependent on the smoking behavior. When smoke yield was adjusted for weight of tobacco burned or puff volume, exposure differences decreased.

CONCLUSIONS

There is a wide range of delivery of both SVOC and VOC components of cigar and cigarillo smoke. The difference in exposure is largely dependent on the article size and the amount consumed.

Recent insights into cigarette smoking as a lifestyle risk factor for breast cancer

There have been many cohort studies published reviewing the epidemiological evidence that links breast cancer to cigarette smoking, yet the underlying mechanisms are largely unknown and research studies are few and incomplete. Although cohort studies are important in establishing a connection between breast cancer and cigarette smoking, basic science research is necessary to prove the relationship and to highlight potential interventions and drug targets that can be used to manage the disease. This subject has been controversial for many decades; however, there has been a recent resurgence in interest because of the widespread acknowledgment of the role lifestyle choices play in cancer development and progression. This review will detail the current statistics associated with cigarette smoking and discuss recent cohort and basic research studies that highlight the association of cigarette smoking and breast cancer initiation and progression.

The detoxification responses, damage effects and bioaccumulation in the scallop Chlamys farreri exposed to single and mixtures of benzo[a]pyrene and chrysene

This study aimed to investigate the detoxification responses, damage effects and biotransformation in scallop Chlamys farreri exposed to benzo[a]pyrene (BaP) (0.1, 1μg/L), chrysene (CHR) (0.1, 1μg/L) and BaP+CHR (0.1+0.1, 1+1μg/L) for 15days. Results demonstrated that BaP and CHR concentration (BaP<CHR) in tissues increased rapidly in a time and dose effect. The mRNA expression of aryl hydrocarbon receptor (AhR), cytochrome P450 1A1 (CYP1A1), CYP1B1, multidrug resistance protein 1 (MRP1/ABCC1), breast cancer resistance protein (BCRP/ABCG2) and P-glycoprotein (P-gp) were induced especially in the mixtures of BaP and CHR. Heat shock protein 90 (HSP90) and aryl hydrocarbon receptor nuclear translocator (ARNT) mRNA expression was significantly elevated at days 1, 10 and 15. Detoxification enzymes of 7-ethoxyresorufin O-deethylase (EROD), uridine-diphosphate-glucuronyl-transferase (UGT) and sulfotransferase (SULT) were significantly induced and then became stable gradually while glutathione-S-transferase (GST) was inhibited in the mixtures of BaP and CHR at days 10 and 15. Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH) were all stimulated especially in the mixtures of BaP and CHR. The levels of DNA strand breaks, lipid peroxidation (LPO) and protein carbonyl (PC) contents showed damage effects exposed BaP and CHR. All the results indicated that BaP and CHR have similar induced effect and a majority of the biomarkers pointed to a more toxic effect when BaP and CHR were mixed. These will provide a solid foundation for the study of PAHs detoxification mechanism in bivalves and valuable information for marine pollution monitoring.

Association of MTHFR (C677T) Gene Polymorphism With Breast Cancer in North India

BACKGROUND

Breast cancer is one of the most common malignancies in women and is associated with a variety of risk factors. The functional single-nucleotide polymorphism (SNP) C677T in the gene encoding 5,10-methylenetetrahydrofolate reductase (MTHFR) may lead to decreased enzyme activity and affect the chemosensitivity of tumor cells. This study was designed to investigate the association of MTHFR gene polymorphism (SNP) in the pathogenesis of breast cancer among the North Indian women population.

MATERIALS AND METHODS

Genotyping was performed by polymerase chain reaction (PCR) using genomic DNA, extracted from the peripheral blood of subjects with (275 cases) or without (275 controls) breast cancer. Restriction fragment length polymorphism was used to study C677T polymorphism in the study groups.

RESULTS

The distribution of MTHFR (C677T) genotype frequencies, ie, CC, TT, and CT, among the patients was 64.7%, 2.18%, and 33.09%, respectively. In the healthy control group, the CC, TT, and CT frequencies were 78.91%, 1.09%, and 20.1%, respectively. The frequencies of C and T alleles were 81.2% and 18.7%, respectively, in the patient subjects, while they were 88.9% and 11.09%, respectively, among the healthy control group. Frequencies of the CT genotype and the T allele were significantly different (P = 0.007 and P = 0.005, respectively) between the control and the case subjects.

CONCLUSION

This study shows an association of the CT genotype and the T allele of the MTHFR (C667T) gene with increased genetic risk for breast cancer among Indian women.

A case-control analysis of smoking and breast cancer in African American women: findings from the AMBER Consortium

Recent population studies suggest a role of smoking in the etiology of breast cancer, but few have been conducted among African American women. In a collaborative project of four large studies, we examined associations between smoking measures and breast cancer risk by menopause and hormone receptor status [estrogen receptor-positive (ER+), ER-negative (ER-) and triple-negative (ER-, PR-, HER2-)]. The study included 5791 African American women with breast cancer and 17376 African American controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated in multivariable logistic regression analysis with adjustment for study and risk factors. Results differed by menopausal status. Among postmenopausal women, positive associations were observed for long duration and greater pack-years of smoking: relative to never smoking, fully adjusted ORs were 1.14 (95% CI: 1.03-1.26) for duration ≥20 years and 1.16 (95% CI: 1.01-1.33) for ≥20 pack-years. By contrast, inverse associations were observed among premenopausal women, with ORs of 0.80 (95% CI: 0.68-95) for current smoking and 0.81 (95% CI: 0.69-0.96) for former smoking, without trends by duration. Associations among postmenopausal women were somewhat stronger for ER+ breast cancer. The findings suggest that the relation of cigarette smoking to breast cancer risk in African American women may vary by menopausal status and breast cancer subtype.

Exposure to multiple sources of polycyclic aromatic hydrocarbons and breast cancer incidence

BACKGROUND

Despite studies having consistently linked exposure to single-source polycyclic aromatic hydrocarbons (PAHs) to breast cancer, it is unclear whether single sources or specific groups of PAH sources should be targeted for breast cancer risk reduction.

OBJECTIVES

This study considers the impact on breast cancer incidence from multiple PAH exposure sources in a single model, which better reflects exposure to these complex mixtures.

METHODS

In a population-based case-control study conducted on Long Island, New York (N=1508 breast cancer cases/1556 controls), a Bayesian hierarchical regression approach was used to estimate adjusted posterior means and credible intervals (CrI) for the adjusted odds ratios (ORs) for PAH exposure sources, considered singly and as groups: active smoking; residential environmental tobacco smoke (ETS); indoor and outdoor air pollution; and grilled/smoked meat intake.

RESULTS

Most women were exposed to PAHs from multiple sources, and the most common included active/passive smoking and grilled/smoked food intake. In multiple-PAH source models, breast cancer incidence was associated with residential ETS from a spouse (OR=1.20, 95%CrI=1.03, 1.40) and synthetic firelog burning (OR=1.29, 95%CrI=1.06, 1.57); these estimates are similar, but slightly attenuated, to those from single-source models. Additionally when we considered PAH exposure groups, the most pronounced significant associations included total indoor sources (active smoking, ETS from spouse, grilled/smoked meat intake, stove/fireplace use, OR=1.45, 95%CrI=1.02, 2.04).

CONCLUSIONS

Groups of PAH sources, particularly indoor sources, were associated with a 30-50% increase in breast cancer incidence. PAH exposure is ubiquitous and a potentially modifiable breast cancer risk factor.

Sources of polycyclic aromatic hydrocarbons are associated with gene-specific promoter methylation in women with breast cancer

BACKGROUND

Tobacco smoke, diet and indoor/outdoor air pollution, all major sources of polycyclic aromatic hydrocarbons (PAHs), have been associated with breast cancer. Aberrant methylation may be an early event in carcinogenesis, but whether PAHs influence the epigenome is unclear, particularly in breast tissue where methylation may be most relevant. We aimed to evaluate the role of methylation in the association between PAHs and breast cancer.

METHODS

In a population-based case-control study, we measured promoter methylation of 13 breast cancer-related genes in breast tumor tissue (n=765-851 cases) and global methylation in peripheral blood (1055 cases/1101 controls). PAH sources (current active smoking, residential environmental tobacco smoke (ETS), vehicular traffic, synthetic log burning, and grilled/smoked meat intake) were evaluated separately. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

When comparing methylated versus unmethylated genes, synthetic log use was associated with increased ORs for CDH1 (OR=2.26, 95%CI=1.06-4.79), HIN1 (OR=2.14, 95%CI=1.34-3.42) and RARβ (OR=1.80, 95%CI=1.16-2.78) and decreased ORs for BRCA1 (OR=0.44, 95%CI=0.30-0.66). Residential ETS was associated with decreased ORs for ESR1 (OR=0.74, 95%CI=0.56-0.99) and CCND2 methylation (OR=0.65, 95%CI=0.44-0.96). Current smoking and vehicular traffic were associated with decreased ORs for DAPK (OR=0.53, 95%CI=0.28-0.99) and increased ORs for TWIST1 methylation (OR=2.79, 95%CI=1.24-6.30), respectively. In controls, synthetic log use was inversely associated with LINE-1 (OR=0.59, 95%CI=0.41-0.86).

DISCUSSION

PAH sources were associated with hypo- and hypermethylation at multiple promoter regions in breast tumors and LINE-1 hypomethylation in blood of controls. Methylation may be a potential biologic mechanism for the associations between PAHs and breast cancer incidence.

Cigarette Smoking and Breast Cancer Risk in Hispanic and Non-Hispanic White Women: The Breast Cancer Health Disparities Study

OBJECTIVE

Few epidemiological studies have included Hispanics with the evaluation of the effects of cigarette smoking and breast cancer. We examined the relationship between cigarette smoking, ethnicity, and breast cancer risk using data from the Breast Cancer Health Disparities Study (BCHDS).

MATERIALS AND METHODS

The BCHDS is a consortium of three population-based case-control studies, including U.S. non-Hispanic whites (NHWs) (1,525 cases; 1,593 controls), U.S. Hispanics/Native Americans (1,265 cases; 1,495 controls), and Mexican women (990 cases; 1,049 controls). Multivariable logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Breast cancer risk was elevated among Mexican former smokers (OR 1.43, 95% CI 1.04-1.96) and among those who smoked ≥ 31 years (OR 1.95, 95% CI 1.13-3.35), compared to never smokers. In addition, Mexican former smokers with a history of alcohol consumption had increased breast cancer risk (OR 2.30, 95% CI 1.01-5.21). Among NHW premenopausal women, breast cancer risk was increased for smoking ≥ 20 cigarettes per day (OR 1.61, 95% CI 1.07-2.41).

CONCLUSION

Our findings suggest the possibility of ethnic differences with the associations between cigarette smoking and breast cancer risk.

Smoking and Risk of Breast Cancer in a Racially/Ethnically Diverse Population of Mainly Women Who Do Not Drink Alcohol: The MEC Study

We prospectively examined the association between smoking and the risk of breast cancer in a racially/ethnically diverse population comprising mainly women who did not drink alcohol. From 1993 to 2010, we followed 83,300 women who were enrolled in the Multiethnic Cohort Study at 45-75 years of age. We identified cancer cases via linkage to the Surveillance, Epidemiology, and End Results Program cancer registries that covered the states of Hawaii and California through December 2010. We used Cox proportional hazards models to estimate hazard ratios and 95% confidence intervals while adjusting for confounders that were decided a priori. During a mean follow-up of 15 years, 4,484 women developed invasive breast cancer. Compared with parous never smokers, women who had smoked for more than 20 pack-years and initiated smoking more than 5 years before their first childbirth had an overall risk of breast cancer that was 35% higher (hazard ratio = 1.35, 95% confidence interval: 1.13, 1.63). Among women who did not drink alcohol, the risk was 40% higher (hazard ratio = 1.40, 95% confidence interval: 1.08, 1.81). This higher risk did not significantly differ among racial/ethnic groups (P(interaction) = 0.82). We found that various measures of smoking exposure were associated with a higher risk of breast cancer, especially smoking initiated many years before first childbirth, and that risk did not differ by alcohol consumption (yes vs. no) or racial/ethnic group.

Cue-reactivity in experienced electronic cigarette users: Novel stimulus videos and a pilot fMRI study

Some individuals who try electronic cigarettes (e-cigarettes) continue to use long-term. Previous research has investigated the safety of e-cigarettes and their potential for use in smoking cessation, but comparatively little research has explored chronic or habitual e-cigarette use. In particular, the relationship between e-cigarette cues and craving is unknown. We sought to bridge this gap by developing a novel set of e-cigarette (salient) and electronic toothbrush (neutral) videos for use in cue-reactivity paradigms. Additionally, we demonstrate the utility of this approach in a pilot fMRI study of 7 experienced e-cigarette users. Participants were scanned while viewing the cue videos before and after 10min use of their own e-cigarettes (producing an 11.7ng/ml increase in plasma nicotine concentration). A significant session (pre- and post-use) by video type (salient and neutral) interaction was exhibited in many sensorimotor areas commonly activated in other cue-reactivity paradigms. We did not detect significant cue-related activity in other brain regions notable in the craving literature. Possible reasons for this discrepancy are discussed, including the importance of matching cue stimuli to participants' experiences.

Polycyclic aromatic hydrocarbon (PAH)-DNA adducts and breast cancer: modification by gene promoter methylation in a population-based study

PURPOSE

Polycyclic aromatic hydrocarbon (PAH)-DNA adducts have been associated with breast cancer incidence. Aberrant changes in DNA methylation may be an early event in carcinogenesis. However, possible relations between PAH-DNA adducts, methylation, and breast cancer are unknown. The objectives of this study were to (1) assess associations between PAH-DNA adducts, and breast cancer, stratified by DNA methylation markers and (2) examine interactions between adducts and DNA methylation in association with breast cancer and tumor subtype.

METHODS

In a population-based case-control study, promoter methylation of 13 breast cancer-related genes was measured in tumor tissue (n = 765-851 cases). Blood DNA from breast cancer cases (n = 873) and controls (n = 941) was used to assess PAH-DNA adducts and global methylation. Logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI); and the ratio of the OR (ROR) was used to assess heterogeneity.

RESULTS

Women with detectable PAH-DNA adducts and methylated RARβ (ROR 2.69, 95% CI 1.02-7.12; p for interaction = 0.03) or APC (ROR 1.76, 95% CI 0.87-3.58; p for interaction = 0.09) genes were more likely to have hormone receptor-positive tumors than other subtypes. Interactions with other methylation markers were not apparent (p ≥ 0.10). The association between adducts and breast cancer did not vary by methylation status of the tumor nor did adducts associate with global methylation in the controls.

CONCLUSIONS

Gene-specific methylation of RARβ, and perhaps APC, may interact with PAH-DNA adducts to increase risk of hormone receptor-positive breast cancer. There was little evidence that adducts were associated with or interacted with other methylation markers of interest.

Resveratrol and curcumin synergistically induces apoptosis in cigarette smoke condensate transformed breast epithelial cells through a p21(Waf1/Cip1) mediated inhibition of Hh-Gli signaling

Combination therapy using two or more small molecule inhibitors of aberrant signaling cascade in aggressive breast cancers is a promising therapeutic strategy over traditional monotherapeutic approaches. Here, we have studied the synergistic mechanism of resveratrol and curcumin induced apoptosis using in vitro (cigarette smoke condensate mediated transformed breast epithelial cell, MCF-10A-Tr) and in vivo (tumor xenograft mice) model system. Resveratrol exposure increased the intracellular uptake of curcumin in a dose dependent manner and caused apoptosis in MCF-10A-Tr cells. Approximately, ten fold lower IC50 value was noted in cells treated with the combination of resveratrol (3μM) and curcumin (3μM) in comparison to 30μM of resveratrol or curcumin alone. Resveratrol+curcumin combination caused apoptosis by increasing Bax/Bcl-xL ratio, Cytochrome C release, cleaved product of PARP and caspase 3 in cells. Interestingly, this combination unaltered the protein expressions of WNT-TCF and Notch signaling components, β-catenin and cleaved notch-1 val1744, respectively. Furthermore, the combination also significantly decreased the intermediates of Hedgehog-Gli cascade including SMO, SHH, Gli-1, c-MYC, Cyclin-D1, etc. and increased the level of p21(Waf/Cip1) in vitro and in vivo. A significant reduction of Gli- promoter activity was noted in combinational drug treated cells in comparison to individual drug treatment. Un-alteration of the expressions of the above proteins and Gli1 promoter activity in p21(Waf/Cip1) knockout cells suggests this combination caused apoptosis through p21(Waf/Cip1). Thus, our findings revealed resveratrol and curcumin synergistically caused apoptosis in cigarette smoke induced breast cancer cells through p2(Waf/Cip1) mediated inhibition of Hedgehog-Gli cascade.

Polycyclic Aromatic Hydrocarbons and Breast Cancer: A Review of the Literature

Polycyclic aromatic hydrocarbons (PAHs) exist and persist in the atmosphere due to the incomplete combustion of fossil fuels, and are established human carcinogens. The influence of PAHs on the development of breast cancer, the most commonly diagnosed cancer in women worldwide, remains unclear. As established risk factors only account for approximately 41% of the breast cancer cases in the USA, researchers have sought to uncover environmental factors involved in breast cancer development. The breasts are particularly susceptible to aromatic carcinogenesis, and the implementation of biomarkers has provided promising insights regarding PAH-DNA adducts in breast cancer. The use of biomarkers measuring PAH-DNA adducts assesses exposure to eliminate the bias inherent in self-reporting measures in case-control studies investigating the link between PAHs and cancer. Adduct levels reflect exposure dose as well as how the body responds to this exposure, which is partially attributable to genetic variability. Evidence suggests that exposure to PAHs has a causational effect on breast cancer in humans, yet this interaction is not clearly understood. In vitro and animal-based studies have consistently revealed that exposure to PAHs deleteriously affects breast tissue, but there is no definitive link between these compounds and breast cancer.

Deregulation of NR2E3, an orphan nuclear receptor, by benzo(a)pyrene-induced oxidative stress is associated with histone modification status change of the estrogen receptor gene promoter

We previously reported that NR2E3, an orphan nuclear receptor, plays an important role in maintaining the basal expression of estrogen receptor α (ER) and that the NR2E3 level is highly correlated with the relapse-free survival of breast cancer patients. Here, we investigated the role of NR2E3 in benzo(a)pyrene (BaP)-mediated cell injury. BaP treatment reduced NR2E3 homo-dimer formation and expression and subsequently decreased ER expression. The chromatin immunoprecipitation assay results showed that the treatment of MCF-7 breast cancer cells and the mouse liver with BaP released NR2E3 from the ER promoter to transform the transcriptionally active histone modification status into a repressive state. NR2E3 depletion in MCF-7 cells also induced a similar inactive epigenetic status in the ER promoter region, indicating that NR2E3 is an essential epigenetic player that maintains basal ER expression. Interestingly, these negative effects of BaP on the expression levels of NR2E3 and ER were rescued by antioxidant treatment. Collectively, our study provides novel evidence to show that BaP-induced oxidative stress decreases ER expression, in part by regulating NR2E3 function, which modulates the epigenetic status of the ER promoter. NR2E3 is likely an essential epigenetic player that maintains basal ER expression to protect cells from BaP-induced oxidative injury.

Base-Displaced Intercalated Conformation of the 2-Amino-3-methylimidazo[4,5-f]quinoline N(2)-dG DNA Adduct Positioned at the Nonreiterated G(1) in the NarI Restriction Site

The conformation of an N²-dG adduct arising from the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a potent food mutagen, was determined in 5′-d(C¹T²C³X⁴G⁵C⁶G⁷C⁸C⁹A¹⁰T¹¹C¹²)-3′:5′-d(G¹³A¹⁴T¹⁵G¹⁶G¹⁷C¹⁸G¹⁹C²⁰C²¹G²²A²³G²⁴)-3′; X = N²-dG-IQ, in which the modified nucleotide X⁴ corresponds to G¹ in the 5′-d(G¹G²CG³CC)-3′ NarI restriction endonuclease site. Circular dichroism (CD) revealed blue shifts relative to the unmodified duplex, consistent with adduct-induced twisting, and a hypochromic effect for the IQ absorbance in the near UV region. NMR revealed that the N²-dG-IQ adduct adopted a base-displaced intercalated conformation in which the modified guanine remained in the anti conformation about the glycosidic bond, the IQ moiety intercalated into the duplex, and the complementary base C²¹ was displaced into the major groove. The processing of the N²-dG-IQ lesion by hpol η is sequence-dependent; when placed at the reiterated G³ position, but not at the G¹ position, this lesion exhibits a propensity for frameshift replication [Choi, J. Y., et al. (2006) J. Biol. Chem., 281, 25297–25306]. The structure of the N²-dG-IQ adduct at the nonreiterated G¹ position was compared to that of the same adduct placed at the G³ position [Stavros, K. M., et al. (2014) Nucleic Acids Res., 42, 3450–3463]. CD indicted minimal spectral differences between the G¹ vs G³N²-dG-IQ adducts. NMR indicated that the N²-dG-IQ adduct exhibited similar base-displaced intercalated conformations at both the G¹ and G³ positions. This result differed as compared to the corresponding C8-dG-IQ adducts placed at the same positions. The C8-dG-IQ adduct adopted a minor groove conformation when placed at position G¹ but a base-displaced intercalated conformation when placed at position G³ in the NarI sequence. The present studies suggest that differences in lesion bypass by hpol η may be mediated by differences in the 3′-flanking sequences, perhaps modulating the ability to accommodate transient strand slippage intermediates.