Environmental tobacco smoke, genetic susceptibility, and risk of lung cancer in never-smoking women

Women, environments and chronic disease: shifting the gaze from individual level to structural factors

INTRODUCTION

Chronic heart and respiratory diseases are two of the leading causes of morbidity and mortality affecting women. Patterns of and disparities in chronic diseases between sub-populations of women suggest that there are social as well as individual level factors which enhance or impede the prevention or development of chronic respiratory and cardiovascular diseases. By examining the sex, gender and diversity based dimensions of women's lung and heart health and how these overlap with environmental factors we extend analysis of preventive health beyond the individual level. We demonstrate how biological, environmental and social factors interact and operate in women's lives, structuring their opportunities for health and abilities to prevent or manage chronic cardiovascular and respiratory diseases.

METHODS

This commentary is based on the findings from two evidence reviews, one conducted on women's heart health, and another on women's lung health. Additional literature was also reviewed which assessed the relationship between environmental factors and chronic heart and lung diseases. This paper explores how obesogenic environments, exposure to tobacco smoke, and the experience of living in deprived areas can affect women's heart and respiratory health. We discuss the barriers which impede women's ability to engage in physical activity, consume healthy foods, or avoid smoking, tobacco smoke, and other airborne contaminants.

RESULTS

Sex, gender and diversity clearly interact with environmental factors and shape women's promotion of health and prevention of chronic respiratory and cardiovascular diseases. The environments women live in structure their opportunities for health, and women navigate these environments in unique ways based on gender, socioeconomic status, race/ethnicity and other social factors.

DISCUSSION

Future research, policy and programs relating to the prevention of chronic disease need to move beyond linear individually-oriented models and address these complexities by developing frameworks and interventions which improve environmental conditions for all groups of women. Indeed, in order to improve women's health, broad social and economic policies and initiatives are required to eliminate negative environmental impacts on women's opportunities for health.

C/EBPbeta-mediated transcriptional regulation of bcl-xl gene expression in human breast epithelial cells in response to cigarette smoke condensate

In previous studies, we have shown that cigarette smoke condensate (CSC), a surrogate for cigarette smoke, is capable of transforming the spontaneously immortalized human breast epithelial cell line, MCF10A. These transformed cells displayed upregulation of the anti-apoptotic gene, bcl-xl. Upregulation of this gene may impede the apoptotic pathway and allow the accumulation of DNA damage that can lead to cell transformation and carcinogenesis. In the present study, we have determined the mechanism of CSC-mediated transcriptional upregulation of bcl-xl gene expression in MCF10A cells. We cloned the human bcl-xl promoter (pBcl-xLP) and identified putative transcription factor binding sites. Sequential deletion constructs that removed the putative cis-elements were constructed and transfected into MCF10A cells to determine the CSC-responsive cis-element(s) on the pBcl-xLP. Gel-shift, supershift, and chromatin immunoprecipitation (ChIP) analysis confirmed that C/EBPβ specifically bound to a C/EBP-binding site on the pBcl-xLP in vitro and in vivo. Additionally, overexpression of C/EBPβ-LAP2 stimulated pBcl-xLP activity and Bcl-xL protein levels, which mimicked the conditions of CSC treatment. Our results indicate that C/EBPβ regulates bcl-xl gene expression in MCF10A cells in response to CSC treatment, therefore making it a potential target for chemotherapeutic intervention of cigarette smoke-induced breast carcinogenesis.

Women and lung cancer: clinical and molecular profiling as a determinate for treatment decisions: a literature review

In the past decade the incidence of lung cancer among women has risen, whereas among men it has slightly declined. Important differences in lung cancer have been demonstrated between men and women, although many areas still remain controversial. Some biologic differences may justify the increase in response of women to therapy for lung cancer and can partially explain the improved survival of women compared with men. We extensively reviewed the published scientific literature on this topic in order to investigate the clinical and genetic profiling underlying lung cancer in women and to use this information as a tool for medical therapy.

Assessment of interactions between PAH exposure and genetic polymorphisms on PAH-DNA adducts in African American, Dominican, and Caucasian mothers and newborns

Polycyclic aromatic hydrocarbons (PAH) are widespread pollutants commonly found in air, food, and drinking water. Benzo[a]pyrene is a well-studied representative PAH found in air from fossil fuel combustion and a transplacental carcinogen experimentally. PAHs bind covalently to DNA to form DNA adducts, an indicator of DNA damage, and an informative biomarker of potential cancer risk. Associations between PAH-DNA adduct levels and both cancer risk and developmental deficits have been seen in previous experimental and epidemiologic studies. Several genes have been shown to play an important role in the metabolic activation or detoxification of PAHs, including the cytochrome P450 genes CYP1A1 and CYP1B1 and the glutathione S-transferase (GST) genes GSTM1, and GSTT2. Genetic variation in these genes could influence susceptibility to adverse effects of PAHs in polluted air. Here, we have explored interactions between prenatal PAH exposure and 17 polymorphisms in these genes (rs2198843, rs1456432, rs4646903, rs4646421, rs2606345, rs7495708, rs2472299, rs162549, rs1056837, rs1056836, rs162560, rs10012, rs2617266, rs2719, rs1622002, rs140194, and gene deletion GSTM1-02) and haplotypes on PAH-DNA adducts in cord blood of 547 newborns and in maternal blood of 806 mothers from three different self-described ethnic groups: African Americans, Dominicans, and Caucasians. PAHs were measured by personal air monitoring of mothers during pregnancy. Significant interactions (p < 0.05) were observed between certain genetic polymorphisms and CYP1A1 haplotype and PAHs in mothers and their newborns in the three ethnic groups. However, with our limited sample size, the current findings are suggestive only, warranting further study.

Second hand smoke, age of exposure and lung cancer risk

BACKGROUND

Exposure to second hand smoke (SHS) has been identified as a risk factor for lung cancer for three decades. It is also known that the lung continues to grow from birth to adulthood, when lung growth stops. We hypothesize that after adjusting for active cigarette smoking, if SHS exposure took place during the period of growth, i.e. in the earlier part of life (0-25 years of age) the risk of lung cancer is greater compared to an exposure occurring after age 25.

METHOD

Second hand smoke exposure was self-reported for three different activities (leisure, work and at home) for this study population of 1669 cases and 1263 controls. We created variables that captured location of exposure and timing of first exposure with respect to a study participant's age (0-25, >25 years of age). Multiple logistic regressions were used to study the association between SHS exposure and lung cancer, adjusting for age, gender and active smoking variables.

RESULT

For study participants that were exposed to SHS at both activities (work and leisure) and compared to one or no activity, the adjusted odds ratio (AOR) for lung cancer was 1.30 (1.08-1.57) when exposure occurred between birth and age 25 and 0.66 (0.21-1.57) if exposure occurred after age 25 years. Respective results for non-smokers were 1.29 (0.82-2.02) and 0.87 (0.22-3.38), and current and ex-smokers combined 1.28 (1.04-1.58) and 0.66 (0.15-2.85).

CONCLUSION

All individuals exposed to SHS have a higher risk of lung cancer. Furthermore, this study suggests that subjects first exposed before age 25 have a higher lung cancer risk compared to those for whom first exposure occurred after age 25 years.

Meta-analysis of studies of passive smoking and lung cancer: effects of study type and continent

BACKGROUND

To calculate a pooled estimate of relative risk (RR) of lung cancer associated with exposure to passive smoking in never smoking women exposed to smoking spouses. This study is an updated meta-analysis that also assesses the differences between estimated risks according to continent and study type using meta-regression.

METHODS

From a total of 101 primary studies, 55 studies are included in this meta-analysis, of which, 7 are cohort studies, 25 population-based case-control and 23 non-population-based case-control studies. Twenty previously published meta-analyses are also reviewed. Fixed and random effect models and meta-regression are used to obtain pooled estimates of RR and P-value functions are used to demonstrate consistency of results.

RESULTS

The pooled RR for never-smoking women exposed to passive smoking from spouses is 1.27 (95% CI 1.17-1.37). The RR for North America is 1.15 (95% CI 1.03-1.28), Asia, 1.31 (95% CI 1.16-1.48) and Europe, 1.31 (1.24-1.52). Sequential cumulative meta-analysis shows no trend. There is no strong evidence of publication bias.

CONCLUSIONS

The abundance of evidence, consistency of finding across continent and study type, dose-response relationship and biological plausibility, overwhelmingly support the existence of a causal relationship between passive smoking and lung cancer.

The relationship between biomarkers of oxidative DNA damage, polycyclic aromatic hydrocarbon DNA adducts, antioxidant status and genetic susceptibility following exposure to environmental air pollution in humans

Polycyclic aromatic hydrocarbons (PAHs) appear to be significant contributors to the genotoxicity and carcinogenicity of air pollution present in the urban environment for humans. Populations exposed to environmental air pollution show increased levels of PAH DNA adducts and it has been postulated that another contributing cause of carcinogenicity by environmental air pollution may be the production of reactive oxygen species following oxidative stress leading to oxidative DNA damage. The antioxidant status as well as the genetic profile of an individual should in theory govern the amount of protection afforded against the deleterious effects associated with exposure to environmental air pollution. In this study we investigated the formation of total PAH (bulky) and B[a]P DNA adducts following exposure of individuals to environmental air pollution in three metropolitan cities and the effect on endogenously derived oxidative DNA damage. Furthermore, the influence of antioxidant status (vitamin levels) and genetic susceptibility of individuals with regard to DNA damage was also investigated. There was no significant correlation for individuals between the levels of vitamin A, vitamin E, vitamin C and folate with M(1)dG and 8-oxodG adducts as well as M(1)dG adducts with total PAH (bulky) or B[a]P DNA adducts. The interesting finding from this study was the significant negative correlation between the level of 8-oxodG adducts and the level of total PAH (bulky) and B[a]P DNA adducts implying that the repair of oxidative DNA damage may be enhanced. This correlation was most significant for those individuals that were non smokers or those unexposed to environmental air pollution. Furthermore the significant inverse correlation between 8-oxodG and B[a]P DNA adducts was confined to individuals carrying the wild type genotype for both the GSTM1 and the GSTT1 gene (separately and interacting). This effect was not observed for individuals carrying the null variant.

Lung Cancer in Never Smokers: A Review

Lung cancer is the leading cause of cancer-related death in the United States. Although tobacco smoking accounts for the majority of lung cancer, approximately 10% of patients with lung cancer in the United States are lifelong never smokers. Lung cancer in the never smokers (LCINS) affects women disproportionately more often than men. Only limited data are available on the etiopathogenesis, molecular abnormalities, and prognosis of LCINS. Several etiologic factors have been proposed for the development of LCINS, including exposure to radon, cooking fumes, asbestos, heavy metals, and environmental tobacco smoke, human papillomavirus infection, and inherited genetic susceptibility. However, the relative significance of these individual factors among different ethnic populations in the development of LCINS has not been well-characterized. Adenocarcinoma is the predominant histologic subtype reported with LCINS. Striking differences in response rates and outcomes are seen when patients with advanced non–small-cell lung cancer (NSCLC) who are lifelong never smokers are treated with epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors such as gefitinib or erlotinib compared with the outcomes with these agents in patients with tobacco-associated lung cancer. Interestingly, the activating mutations in the EGFR-TK inhibitors have been reported significantly more frequently in LCINS than in patients with tobacco-related NSCLC. This review will summarize available data on the epidemiology, risk factors, molecular genetics, management options, and outcomes of LCINS.

A mutation in separase causes genome instability and increased susceptibility to epithelial cancer

Proper chromosome segregation is essential for maintenance of genomic integrity and instability resulting from failure of this process may contribute to cancer. Here, we demonstrate that a mutation in the mitotic regulator separase is responsible for the cell cycle defects seen in the zebrafish mutant, cease&desist (cds). Analysis of cds homozygous mutant embryos reveals high levels of polyploidy and aneuploidy, spindle defects, and a mitotic exit delay. Carcinogenesis studies demonstrated that cds heterozygous adults have a shift in tumor spectrum with an eightfold increase in the percentage of fish bearing epithelial tumors, indicating that separase is a tumor suppressor gene in vertebrates. These data strongly support a conserved cross-species role for mitotic checkpoint genes in genetic stability and epithelial carcinogenesis.

New approach to environmental tobacco smoke exposure and its relation to reemission processes

Indoor air quality is one of the factors that determine human well-being and health. Being aware of this fact, it is essential to identify the origin, kind, mechanism, and effects of harmful substances contained in the air. The issue concerning the contents and primary emission of these substances from building materials and interior furnishings is well known. Adverse effects of environmental tobacco smoke (ETS), including exposure of passive smokers, are also very well documented. To the contrary, reports on secondary and indirect emissions, especially those focused on mechanisms by which pollution is "transferred" by materials used in interior furnishings are very rare. Textiles are used in a great variety of ways as functional and decorative materials. These materials in general, and textile floor coverings in particular, are extensively utilized in fitting apartments, public buildings, and transport means. Studies on this aspect of the role played by textile materials in ETS exposure have been only fragmentary documented.

[Lung cancer in women: a different entity?]

Lung cancer is becoming a real epidemic in developed countries and one of the main causes of cancer death in women. Although it is controversial to state, it is probable that women are more susceptible to lung cancer than men. Molecular and genetic epidemiology studies are underway to prove this statement. Several biological factors, such as family history, histopathology, response to treatment and the prognosis for lung cancer in women have a bearing on the case. While these are not completely clear or consensual, there is a need for wide-ranging prospective studies which compare the differences between males and females. Until now, there has only been one area in which gender could impact on the therapeutic management of lung cancer: the role of gefitinib and erlotinib in inhibiting the epidermal growth factor receptors, since these products are clearly of more benefit to female non-smokers. Given that women have a better lung cancer prognosis, it is recommended that future research protocols include stratification on gender. Prevention of lung cancer in both women and men is a priority public health concern. A mandatory aim of this is the fight against smoking, the largest aetiological factor of lung cancer.

Radon, secondhand smoke, glutathione-S-transferase M1 and lung cancer among women

Tobacco smoke and ionizing radiation induce oxidative stress by transmitting or generating reactive oxygen species (ROS). We hypothesized that glutathione-S-transferase M1 (GSTM1) null homozygotes would have decreased ability to neutralize ROS that might increase their susceptibility to lung cancer. A case-only design was used with lung cancer cases pooled from 3 previously completed case-control studies using archival tissue samples from 270 lung cancer cases to genotype GSTM1. Radon concentrations were measured with long-term alpha-track radon detectors. Secondhand smoke (SHS) was measured with questionnaires and interviews. Unconditional logistic regression was used to calculate the interaction odds ratios (OR) and 95% confidence intervals (95% CI). Radon concentrations >121 Bq m(-3) were associated with a >3-fold interaction OR (OR = 3.41; 95% CI = 1.10, 10.61) for GSTM1 null homozygotes compared to GSTM1 carriers; the linear trend was significant (p trend = 0.03). The SHS and GSTM1 interaction OR was also elevated (OR = 2.28; 95% CI = 1.15-4.51) among never-smokers. This may be the first study to provide evidence of a GSTM1 and radon interaction in risk of lung cancer. Additionally, these findings support the hypothesis that radon and SHS promote neoplasia through shared elements of a common pathway.

Lung cancer in women

Lung cancer is the most common cancer in both men and women; however, there are some clear gender-based differences. As the incidence of lung cancer is declining in men, the incidence of lung cancer is increasing in women. Women are more likely than men to have adenocarcinoma, a histologic subtype that correlates with worsened prognosis, but women have improved survival compared with men. Genetic predisposition and the presence of estrogen receptors in lung cancer cells may predispose women to developing lung cancer. Further studies are needed to understand the mechanism and significance of these findings.

An overview of the North American residential radon and lung cancer case-control studies

Lung cancer has held the distinction as the most common cancer type worldwide since 1985 (Parkin et al., 1993). Recent estimates suggest that lung cancer accounted for 1.2 million deaths worldwide in 2002, which represents 17.6% of the global cancer deaths (Parkin et al., 2005). During 2002, the highest lung cancer rates for men worldwide reportedly occurred in North America and Eastern Europe, whereas the highest rates in females occurred in North America and Northern Europe (Parkin et al., 2005). While tobacco smoking is the leading risk factor for lung cancer, because of the magnitude of lung cancer mortality, even secondary causes of lung cancer present a major public health concern (Field, 2001). Extrapolations from epidemiologic studies of radon-exposed miners project that approximately 18,600 lung cancer deaths per year (range 3000 to 41,000) in the United States alone are attributable to residential radon progeny exposure (National Research Council, 1999). Because of differences between the mines and the home environment, as well as differences (such as breathing rates) between miners and the general public, there was a need to directly evaluate effects of radon in homes. Seven major residential case-control radon studies have been conducted in North America to directly examine the association between prolonged radon progeny (radon) exposure and lung cancer. Six of the studies were performed in the United States including studies in New Jersey, Missouri (two studies), Iowa, and the combined states study (Connecticut, Utah, and southern Idaho). The seventh study was performed in Winnipeg, Manitoba, Canada. The residential case-control studies performed in the United States were previously reviewed elsewhere (Field, 2001). The goal of this review is to provide additional details regarding the methodologies and findings for the individual studies. Radon concentration units presented in this review adhere to the types (pCi/L or Bq/m3) presented in the individual studies. One picocurie per liter is equivalent to 37 Bq/m3. Because the Iowa study calculated actual measures of exposure (concentration x time), its exposures estimates are presented in the form WLM(5-19) (Field et al., 2000a). WLM(5-19) represents the working level months for exposures that occurred 5-19 yr prior to diagnosis for cases or time of interview for control. Eleven WLM(5-19) is approximately equivalent to an average residential radon exposure of 4 pCi/L for 15 yr, assuming a 70% home occupancy.

Secondhand smoke exposure in early life and the risk of breast cancer among never smokers (United States)

Evidence is increasing that some early life exposures affect breast cancer risk. Exposure to secondhand smoke (SHS) during childhood may be one such exposure. As part of the WEB Study (Western New York Exposures and Breast Cancer Study), we conducted a population-based, case-control study with 1166 women aged 35 to 79 diagnosed with histologically confirmed, primary, incident breast cancer. Controls (n = 2105) were randomly selected from the Department of Motor Vehicles driver's license list (< or =age 65) and the Center for Medicare & Medicaid Services rolls (> age 65). Participants were queried regarding household and workplace SHS exposure. Person-years of lifetime cumulative SHS exposure were computed as well as cumulative exposure up to 21 years of age. Unconditional logistic regression adjusting for potential confounders was used to calculate odds ratios (OR) and 95% confidence intervals (95% CI). Lifetime cumulative exposure to household SHS was not associated with an increase in breast cancer risk for premenopausal (OR = 1.17, 95% CI = 0.54-2.56) or postmenopausal (OR = 1.29; 95% CI = 0.82-2.01) women. Neither was risk increased among women exposed to SHS before the age of 21 or at the time of birth, menarche, or a women's first birth. In this study, exposure to SHS either in adult or early life does not appear to be associated with the risk of breast cancer.

Lung cancer in women: emerging differences in epidemiology, biology, and therapy

Lung cancer is the major cause of cancer-related death in both men and women in the United States. Emerging evidence indicates that there are differences in the pathogenesis and possibly increased susceptibility to lung cancer in women. In addition, considerable data support small, but important differences favoring women in terms of response to therapy and long-term survival after the diagnosis of lung cancer, regardless of histology or stage. These differences in both biology and outcome will be important considerations in the design of future trials of screening and therapy for lung cancer.

Use of a transgenic mouse model to identify markers of human lung tumors

Lung cancer remains the leading cause of cancer related deaths worldwide. Despite advances in detection technologies, most patients diagnosed with lung cancer already harbor metastatic lesions. Because early detection is one of the primary determinants of patient outcome, a transgenic mouse model of lung cancer was utilized to identify markers of early lung tumors in humans. DNA microarray analysis of lung tumors arising in MMTV-IGF-II transgenic mice showed 9 genes consistently elevated in the murine lung tumors. Western blot analyses confirmed that several of these proteins were elevated in the lung tumors and immunohistochemical analyses identified 3 proteins, microsomal glutathione-S-transferase 1 (Mgst1), cathepsin H and syndecan 1 as being consistently elevated in the murine lung tumors compared to non-tumor bearing transgenic lung tissue and normal lung tissue surrounding the tumor. These 3 proteins were also elevated in human lung adenocarcinoma and squamous cell carcinomas. Importantly, the proteins were elevated in early stage, node negative tumors indicating their ability to detect early lung lesions that would be amenable to surgical resection. Therefore, our findings indicate that Mgst1, cathepsin H and syndecan 1 should be further evaluated as markers capable of identifying patients with early stage lung tumors.

CYP1A1 polymorphisms and risk of lung cancer in non-smoking Chinese women: influence of environmental tobacco smoke exposure and GSTM1/T1 genetic variation

OBJECTIVE

We examined whether polymorphisms of CYP1A1, which plays a role in the metabolic activation of polycyclic aromatic hydrocarbons (PAHs), confer an increased risk of lung cancer in lifetime non-smoking Chinese women.

METHODS

A total of 126 incident lung cancer cases, of which 87.7 were pathologically confirmed, and 162 age-matched hospital controls were included. CYP1A1 MspI and Ile(462)Val polymorphisms were genotyped and tested for association with this disease.

RESULTS

An elevated risk of lung cancer was observed among individuals with the MspI CC (OR=1.7, 95 CI=0.9-3.3) and Ile(462)Val ValVal genotypes (OR=2.8, 95 CI=1.1-7.6). After stratifying by environmental tobacco smoke (ETS) exposure, the risk of lung cancer associated with both polymorphisms was higher among individuals with lower exposure to ETS, compared with those who reported at least weekly exposure. Individuals with the MspI CC genotype showed a two-fold higher risk of lung cancer if they were also null for either GSTM1 or T1 (OR=2.3, 95CI=1.0-5.0 and OR=2.7, 95 CI=1.1-6.9, respectively, compared to other genotype combinations combined).

CONCLUSIONS

CYP1A1 is a susceptibility gene for lung cancer among non-smoking Asian women and this association can be influenced by ETS exposure and genetic variation at GST genes.

Cancer incidence patterns among adolescents and young adults in the United States

OBJECTIVE

The purpose of this study was to examine age-specific cancer incidence patterns among adolescents and young adults (ages 15--49).

METHOD

Cancer incidence data for 1995--1999 from 22 population-based central cancer registries, covering about 47% of the US population, were used. Relative frequencies and average annual age-specific incidence rates per 100,000 person-year were computed for the five-year age groups from age 15--19 years through 45--49 years. Tests of significance for comparison were at a level of p<0.05.

RESULTS

The age at crossover from a predominance of non-epithelial cancers to a predominance of epithelial cancers during adolescence and young adulthood varied by gender and race. Epithelial cancer became the predominant type of tumor after age 40 years among males while it was the predominant type after age 25 years among females. There was also a shift in the top five cancer types with increasing age, which varied by race and gender. Epithelial cancers of the thyroid, breast, ovary, and cervix uteri started to increase sharply among young women in their 20s while among males epithelial cancers rarely occurred until the early 30s (ages 30--34). Cancers of the female breast, colon and rectum, and lung began to occur at an earlier age and increased more sharply among blacks than among whites. However, the incidence rates of epithelial thyroid and ovarian cancers rose more quickly among whites than blacks. Non-Hodgkin lymphoma and soft tissue sarcoma (excluded Kaposi's sarcoma) increased with age among both whites and blacks but the rates were significantly higher among blacks than among whites. Both Kaposi's sarcoma and testicular cancer incidence increased with age and peaked in the early 30s (ages 30--34). The former was significantly higher among blacks than whites while the latter was significantly higher among whites than blacks. Cervical cancer incidence leveled off when white women reached their 30s, but for black women the rate continued to rise with advancing age. Cutaneous melanoma rates were significantly higher among females than among males between the ages of 15 and 39. Conclusion Cancer incidence patterns among adolescents and young adults are distinctive. Specific cancer prevention and control strategies should be targeted accordingly and tailored to their specific needs.

Environmental tobacco smoke and risk of respiratory cancer and chronic obstructive pulmonary disease in former smokers and never smokers in the EPIC prospective study

OBJECTIVES

To investigate the association between environmental tobacco smoke, plasma cotinine concentration, and respiratory cancer or death.

DESIGN

Nested case-control study within the European prospective investigation into cancer and nutrition (EPIC).

PARTICIPANTS

303,020 people from the EPIC cohort (total 500,000) who had never smoked or who had stopped smoking for at least 10 years, 123,479 of whom provided information on exposure to environmental tobacco smoke. Cases were people who developed respiratory cancers or died from respiratory conditions. Controls were matched for sex, age (plus or minus 5 years), smoking status, country of recruitment, and time elapsed since recruitment.

MAIN OUTCOME MEASURES

Newly diagnosed cancer of lung, pharynx, and larynx; deaths from chronic obstructive pulmonary disease or emphysema. Plasma cotinine concentration was measured in 1574 people.

RESULTS

Over seven years of follow up, 97 people had newly diagnosed lung cancer, 20 had upper respiratory cancers (pharynx, larynx), and 14 died from chronic obstructive pulmonary disease or emphysema. In the whole cohort exposure to environmental tobacco smoke was associated with increased risks (hazard ratio 1.30, 95% confidence interval 0.87 to 1.95, for all respiratory diseases; 1.34, 0.85 to 2.13, for lung cancer alone). Higher results were found in the nested case-control study (odds ratio 1.70, 1.02 to 2.82, for respiratory diseases; 1.76, 0.96 to 3.23, for lung cancer alone). Odds ratios were consistently higher in former smokers than in those who had never smoked; the association was limited to exposure related to work. Cotinine concentration was clearly associated with self reported exposure (3.30, 2.07 to 5.23, for detectable/non-detectable cotinine), but it was not associated with the risk of respiratory diseases or lung cancer. Frequent exposure to environmental tobacco smoke during childhood was associated with lung cancer in adulthood (hazard ratio 3.63, 1.19 to 11.11, for daily exposure for many hours).

CONCLUSIONS

This large prospective study, in which the smoking status was supported by cotinine measurements, confirms that environmental tobacco smoke is a risk factor for lung cancer and other respiratory diseases, particularly in ex-smokers.

Genotoxicity of environmental tobacco smoke: a review

Environmental tobacco smoke (ETS), or second-hand smoke, is a widespread contaminant of indoor air in environments where smoking is not prohibited. It is a significant source of exposure to a large number of substances known to be hazardous to human health. Numerous expert panels have concluded that there is sufficient evidence to classify involuntary smoking (or passive smoking) as carcinogenic to humans. According to the recent evaluation by the International Agency for Research on Cancer, involuntary smoking causes lung cancer in never-smokers with an excess risk in the order of 20% for women and 30% for men. The present paper reviews studies on genotoxicity and related endpoints carried out on ETS since the mid-1980s. The evidence from in vitro studies demonstrates induction of DNA strand breaks, formation of DNA adducts, mutagenicity in bacterial assays and cytogenetic effects. In vivo experiments in rodents have shown that exposure to tobacco smoke, whole-body exposure to mainstream smoke (MS), sidestream smoke (SS), or their mixture, causes DNA single strand breaks, aromatic adducts and oxidative damage to DNA, chromosome aberrations and micronuclei. Genotoxicity of transplacental exposure to ETS has also been reported. Review of human biomarker studies conducted among non-smokers with involuntary exposure to tobacco smoke indicates presence of DNA adducts, urinary metabolites of carcinogens, urinary mutagenicity, SCEs and hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene mutations (in newborns exposed through involuntary smoking of the mother). Studies on human lung cancer from smokers and never-smokers involuntarily exposed to tobacco smoke suggest occurrence of similar kinds of genetic alterations in both groups. In conclusion, these overwhelming data are compatible with the current knowledge on the mechanisms of carcinogenesis of tobacco-related cancers, occurring not only in smokers but with a high biological plausibility also in involuntary smokers.

Women and tobacco dependence

Millions of American girls and women have been drawn to smoking by an industry that has been clearly and systematically targeting women of all ages and life circumstances. Tobacco marketing strategies skillfully link cigarette use to typical female values. Biologically speaking, women are especially vulnerable to the legion of health problems of tobacco use. Smoking is a critical hazard for women in their reproductive years, particularly when they are pregnant.

Respiratory health consequences of environmental tobacco smoke

Over the last several decades there has been a growing interest in examining the health consequences of environmental tobacco smoke (ETS). As a result of a wide body of research, ETS is now considered an unacceptable and entirely preventable public health hazard, and public policy increasingly discourages the presence of tobacco smoke in the public domain. This article provides an overview of the composition of ETS and the major diseases and disorders strongly linked to ETS, emphasizing the effects of ETS on pulmonary function, asthma, and lung cancer.

Lung cancer among women in France

As the incidence of primary lung cancer in women seems to be increasing in parallel with that of smoking, we conducted an exhaustive epidemiological study in 137 hospitals in 2000. We identified 904 women with proven primary lung cancer (mean age 63.9 years), many of whom have never smoked (32.3%), particularly in cases of adenocarcinoma (43.4%). Small cell cancer accounted for 16.1% of cases. Adenocarcinomas were the most frequent (45.3%) of the non-small cell lung cancer (NSCLC), followed by squamous cell (23.4%), large cell (11.6%) and bronchoalveolar (1.9%) carcinomas. About one third (32.2%) of NSCLC were stage III and 48.1% were stage IV. Over half of all adenocarcinomas were stage IV. According to multivariate analysis, adenocarcinoma is related to less smoking and younger age. In conclusion, many women affected by lung cancer have never smoked. Adenocarcinoma appears to be the most frequent form and more often at a metastatic stage.

Risk modification by CYP1A1 and GSTM1 polymorphisms in the association of environmental tobacco smoke and lung cancer: a case-control study in Japanese nonsmoking women

Genetic backgrounds may modify the association of environmental tobacco smoke (ETS) with lung cancer risk. Polymorphisms of both the activating and detoxifying enzymes, cytochrome P4501A1 (CYP1A1) and glutathione-S-transferase M1 (GSTM1), may be important as genetic factors. We conducted a multicenter case-control study in Japanese nonsmoking women. Cases were women aged 30-89 years and newly diagnosed as having lung cancer from November 1997 to March 2001 in 4 study areas. We also recruited age-matched (5-year strata) and hospital-matched nonsmoking controls. A total of 158 cases and 259 hospital controls supplied blood for genotyping. Detailed information on ETS exposure from husbands and that in other situations and on potential confounders was collected by interview. Odds ratios (ORs) were estimated by using conditional logistic models. We found no increase in the risk of lung cancer for CYP1A1 Msp I genotypes. For the GSTM1 null genotype vs. nonnull genotype, the OR was 1.37 [95% confidence interval (CI) 0.90-2.09], which indicated a somewhat increased risk for the GSTM1 null genotype. A gene-environment interaction was suggested, with combined GSTM1 null genotype and high-dose ETS exposure (>/=40 pack-years by husbands) conferring significantly higher risk (OR = 2.27, 95% CI 1.13-4.57) compared to the GSTM1 nonnull genotype and low-dose ETS exposure (<40 pack-years). Our results do not support a major role of Msp I polymorphism of the CYP1A1 gene as a risk factor for lung cancer among nonsmoking women. In contrast, the GSTM1 null genotype posed an increased, although not significant, risk among them. Additional studies are warranted to confirm the ETS-GSTM1 polymorphism interaction suggested in our present study.

Genetic alterations of lung adenocarcinoma in relation to smoking and ethnicity

Adenocarcinoma of the lung is now the most common histologic subtype of non-small-cell lung cancer (NSCLC) worldwide. In Chinese populations, the incidence of lung adenocarcinoma is amongst the highest worldwide and its development in non-smoking females is particularly striking. Information on the associated underlying genetic changes has been, however, minimal to date. The present study represents the first systematic analysis on the overall genetic changes in lung adenocarcinoma of Chinese female non-smokers. We undertook a genome-wide investigation into the abnormalities in lung adenocarcinomas of 18 life-long non-smoking Chinese females using the technique of comparative genomic hybridization (CGH). With a view to isolating the relative roles of gender, ethnicity and tobacco consumption, we recruited control groups of 10 Caucasian female non-smokers and 22 male Chinese smokers. Although gains on 1q, 5p, 7p and 8q, and regional losses on 8p, 17p, 13q and 18q were commonly seen, there were no significant differences between the Caucasian and Chinese non-smoking women. The observation suggests that lung adenocarcinomas, regardless of ethnic origin, adopt similar pathologic pathways during the accumulation of genetic events. Besides, genomic imbalances, particularly gains per tumor, were significantly more common among the tobacco-related tumors (P=0.006). In particular, regional over-representations of 13q21-q34 (P=0.044), 17q25 (P=0.015), 19q13.1 (P=0.044) and 22q (P=0.044) may have implications for the pathologic pathways associated with the tobacco-related lung adenocarcinoma.

Progress in lung cancer chemoprevention

BACKGROUND

Lung cancer is one of the major causes of cancer-related deaths. Lung cancer mortality figures argue powerfully for new approaches to control this disease. The term chemoprevention can be defined as the use of specific natural or synthetic chemical agents to reverse, suppress, or prevent premalignancy from progressing to invasive cancer.

METHODS

Issues related to lung cancer chemoprevention are reviewed, including risk factors and identification of high-risk cohorts, endpoint biomarkers, and current and new chemopreventive agents. Also, important findings from chemoprevention randomized, controlled trials are summarized.

RESULTS

Trials in lung cancer chemoprevention have so far produced either neutral or harmful primary endpoint results, whether in the primary, secondary, or tertiary settings. Lung cancer was not prevented by beta-carotene, alpha-tocopherol, retinol, retinyl palmitate, N-acetylcysteine, or isotretinoin in smokers. Secondary results from the phase III trials involving selenium and vitamin E, as well as results from the US Intergroup NCI I91-0001 trial supporting treatment with isotretinoin in never and former smokers, are promising and may help define new avenues for chemoprevention.

CONCLUSIONS

The concept of chemoprevention in lung cancer is still in its infancy but one day may have a significant impact on the incidence and mortality of this leading cancer threat. Molecular markets of risk, drug activity and targeting, improved imaging techniques, and new drug delivery systems are being evaluated.

Association between self-reported environmental tobacco smoke exposure and lung cancer: modification by GSTP1 polymorphism

Environmental Tobacco Smoke (ETS) exposure has been associated with lung cancer risk. ETS is composed of emissions from cigarette smoke and contains a higher concentration of tobacco smoke carcinogens than mainstream smoke. Polymorphisms in genes that metabolize tobacco smoke carcinogens have been studied as effect modifiers of the association between active smoking and lung cancer risk. GSTP1 is a polymorphic gene that encodes for GST pi, a detoxification enzyme and has a high expression in the lung. We investigated the association between ETS and lung cancer risk and the modification of this association by the GSTP1 polymorphism. Using a case-control design, individuals were genotyped for GSTP1 using PCR-RFLP techniques. All analyses were carried out using multiple logistic regression. The association between ETS exposure and lung cancer risk was evaluated in different strata based on smoking habits to evaluate the consistency of results. The effect of the GSTP1 polymorphisms on lung cancer risk was evaluated by considering the joint effect of having both an ETS exposure and the GSTP1 GG genotype compared to the absence of ETS exposure and the GSTP1 AA genotype as a reference group as well as doing stratified analysis by genotype. ETS exposure was associated consistently with higher lung cancer risk in all the strata considered. The adjusted odds ratios (AOR) evaluating the association between ETS and lung cancer risk for the different strata were: nonsmokers (Cases/Controls 66/413; AOR = 1.38; 95% CI = 0.78-2.43), ex-smokers (Cases/Controls 560/527; AOR = 1.66; 95% CI = 1.22-2.25), current smokers (Cases/Controls 415/219; AOR = 1.56; 95% CI = 1.00-2.41). The AORs for ex-smokers and light smoking subgroups were: ex-smokers who quit for 19 years or more (Cases/Controls 144/244; AOR = 2.64; 95% CI = 1.55-4.50), ex-smokers who quit for 10-19 years (Cases/Controls 141/128; AOR = 1.16; 95% CI = 0.66-2.04), ex-smokers who quit for 10 years or less (Cases/Controls 247/122; AOR = 1.45; 95% CI = 0.83-2.55) and participants who had <15 packyears and nonsmokers combined (Cases/Controls 143/640; AOR = 1.52; 95% CI = 1.02-2.28). Among those with the GSTP1 GG genotype the ETS-lung cancer risk association was greater than those with the GSTP1 AA genotype: nonsmokers (GSTP1 GG AOR = 7.84; 95% CI = 0.80-76.68; GSTP1 AA AOR = 1.15; 95% CI = 0.46-2.90), ex-smokers (GSTP1 GG AOR = 2.32; 95% CI = 0.90-5.96; GSTP1 AA AOR = 2.15; 95% CI = 1.34-3.44), current smokers (GSTP1 GG AOR = 1.75; 95% CI = 0.42-7.32; GSTP1 AA AOR = 1.32; 95% CI = 0.67-2.58) and participants who had <15 packyears and nonsmokers (GSTP1 GG AOR = 1.93; 95% CI = 0.54-6.97; GSTP1 AA AOR = 1.58; 95% CI = 0.83-3.01). We found that ETS exposure is associated with higher lung cancer risk. Furthermore, the presence of the GSTP1 GG genotype appears to enhance the magnitude of the association between ETS exposure and lung cancer. Larger studies will be needed to confirm these preliminary findings.

Gene Polymorphisms in Detoxification Enzymes as Susceptibility Factor for Head and Neck Cancer?

OBJECTIVE: Impaired detoxification of carcinogens found in tobacco smoke appears to increase the risk for tobacco associated cancer. The objective of this study was to investigate concomitant polymorphisms in genes encoding for various detoxification enzymes in patients with head and neck squamous cell carcinoma (HNSCC).

METHODS: In 187 patients with HNSCC and in 139 healthy control subjects, the polymorphisms of cytochrome P450 1A1 ( CYP1A1), cytochrome P450 2D6 ( CYP2D6), and glutathione S-transferase μ1 and θ ( GSTM1, GSTT1) were detected by polymerase chain reaction.

RESULTS: No significant association were identified between CYP1A1 and CYP2D6 gene polymorphisms and HNSCC. Patients with laryngeal cancer revealed the GSTM1 null genotype more frequently than did the control subjects ( P < 0.05). The coincidence of GSTM1 and GSTT1 null genotype was found twice as great in patients as in control subjects ( P < 0.05).

CONCLUSIONS: It is assumed that detoxification enzymes are functionally redundant and only the simultaneous deficiency of several detoxification enzymes increase the risk for HNSCC in alcohol- and tobacco-exposed individuals.

Genetic influence on cigarette-induced cardiovascular disease

Cigarette smoking as an addictive habit has accompanied human beings for more than 4 centuries. It is also one of the most potent and prevalent environmental health risks human beings are exposed to, and it is responsible for more than 1000 deaths each day in the United States. With recent research progress, it becomes clear that cigarette smoking can cause almost all major diseases prevalent today, such as cancer or heart disease. These detrimental effects are not only present in active smokers who choose the risk, but also to innocent bystanders, as passive smokers, who are exposed to cigarettes not-by-choice. While the cigarette-induced harm to human health is indiscriminate and severe, the degree of damage also varies from individual to individual. This intersubject variability in cigarette-induced pathologies is partly mediated by genetic variants of genes that may participate in detoxification process, eg, cytochrome P450 (CYP), cellular susceptibility to toxins, such as p53, or disease development. Through population studies, we have learned that certain CYP1A1 variants, such as Mspl polymorphism, may render the carriers more susceptible to cigarette-induced lung cancer or severe coronary atherosclerosis. The endothelial nitric oxide synthase intron 4 rare allele homozygotes are more likely to have myocardial infarction if they also smoke. In vitro experimental approach has further demonstrated that cigarettes may specifically regulate these genes in genotype-dependent fashion. While we still know little about genetic basis and molecular pathways for cigarette-induced pathological changes, understanding these mechanisms will be of great value in designing strategies to further reduce smoking in targeted populations, and to implement more effective measures in prevention and treatment of cigarette-induced diseases.

Patterns of allelic loss differ in lung adenocarcinomas of smokers and nonsmokers

Cigarette smoking is the most important cause of lung cancer, however approximately 10% of patients with lung cancer have no history of smoking. While the molecular pathogenesis of smoking associated lung carcinogenesis is becoming well characterized, the pathogenesis of lung cancer in nonsmokers is not. We designed a study to examine the pathogenesis of adenocarcinoma in nonsmokers by determining if loss of heterozygosity (LOH) in tumors of nonsmokers differs from those of smokers. We evaluated six cases of primary adenocarcinoma in never smokers and six selected cases in smokers, matched by clinical and histological criteria. LOH in tumor DNA relative to nonmalignant lung DNA was determined at 52 microsatellites located on ten chromosomal loci. The extent of allelic loss in smokers, as measured by fractional allelic loss (FAL), was compared with nonsmokers. LOH was more frequent in the tumors of nonsmokers than of smokers with mean FAL of 46% in nonsmokers and 28% in smokers (P<0.05). Increased LOH in nonsmokers was most pronounced at chromosomes: 3p, 8p, 9p, 10p, and 18q. Since this study compared allelic loss between lung and tumor-bearing lung, less frequent LOH in smokers' tumors can be interpreted to suggest LOH was already present in the nonmalignant lung of smokers and fewer additional instances of allelic loss were present in the tumors of smokers. Our results suggest that the early steps of lung carcinogenesis differ in nonsmokers compared with smokers. In addition, the chromosomal sites of LOH may identify genes important for lung carcinogenesis in nonsmokers.

Risk factors for lung cancer among Canadian women who have never smoked

Risk factors for lung cancer among women who had never smoked were assessed in a case-control study of 161 newly diagnosed histologically confirmed cases and 483 population controls between 1994 and 1997 in eight Canadian provinces. Measurement included socio-economic status, smoking habits, alcohol use, diet, residential and occupational histories and exposure to environmental tobacco smoke (ETS). Dose-response associations were observed for consumption of tea, adjusted odds ratios (ORs) 0.6 (95% confidence interval (CI) = 0.3-0.9) for 1-7 cups per week and 0.4 (95% CI = 0.2-0.7) for > or = 8 cups per week (P = 0.0008), and smoked meat, adjusted ORs 1.3 (95% CI = 0.8-2.3) for 0.5 slice per week and 2.1 (95% CI = 1.1-4.0) for >0.5 slice per week (P = 0.02). Regular use of shortening in cooking was also related to lung cancer. Increased ORs with borderline significance were found for total consumption of meat, eggs or French fries and fried potatoes. Passive exposure to ETS at home (or at work) may be associated with lung cancer risk among never-smoker women; the adjusted ORs were 0.7 (95% CI = 0.2-2.3), 1.2 (95% CI = 0.4-3.2), 1.5 (95% CI = 0.5-4.0) for 1-16, 17-30, and 31 or more years of combined residential and/or occupational ETS exposure, respectively, with a similar pattern for smoker-years of ETS exposure.

Tobacco use and cancer: an epidemiologic perspective for geneticists

Much of what is known about the deleterious effects of tobacco use on health was learned from epidemiologic studies over the last half century. These studies establish unequivocally that tobacco use, particularly manufactured cigarette smoking, causes most cancers of the lung, oropharynx, larynx, and esophagus in the USA, and approximately one-third of all cancers of the pancreas, kidney, urinary bladder and uterine cervix. More recent evidence also implicates smoking with cancers of the stomach, liver and colorectum. While over half of the estimated 440 000 smoking-attributable deaths that occur annually in the USA involve non-malignant cardiovascular and respiratory conditions, smoking-attributable cancers are more recognized and feared. Geneticists increasingly study tobacco use as a model for environmental carcinogenicity. Tobacco-exposed populations provide opportunities to characterize the somatic mutations that give rise to specific cancers and to identify the inherited genetic traits that confer susceptibility or resistance. Studies to identify the genetic determinants of addiction may be particularly important. Future research to identify other susceptibility factors, such as genes that modify carcinogen metabolism or DNA repair, will need to be substantially larger and to quantify lifetime tobacco exposure with more precision than have past studies in order to distinguish gradations in risk due to exposure from those caused by genetic susceptibility. This review considers: (a) the epidemiology of tobacco use; (b) cancers presently classified as smoking-attributable by the US Surgeon General; (c) the magnitude of the epidemic of cancers and other diseases caused by tobacco use; (d) selected issues in the epidemiology of lung cancer; and (e) the interface of genetics and epidemiology in understanding, preventing, and treating tobacco-attributable disease.

Epidemiology of environmental tobacco smoke exposure

The health hazards due to exposure to environmental tobacco smoke (ETS) are increasingly established. ETS contains thousands of chemicals including 43 known carcinogens. One of the most important known health effects of ETS exposure is lung cancer in non-smokers, based on epidemiologic evidence and knowledge of the uptake and metabolism of ETS. Epidemiologic studies need to carefully take into account confounding and potential errors in exposure assessment. More research is needed to understand the genetic factors that influence ETS-induced lung cancer. Studies of the patterns of ETS exposure suggest higher rates of exposure in people employed as blue collar workers, in service occupations, earning lower incomes, and among the less educated. Certain racial/ethnic groups (e.g. Blacks, American Indians) may be at higher risk of ETS exposure. Despite substantial progress in protecting individuals from ETS exposure, additional efforts are needed in improving and enforcing policies to reduce exposure.

Characteristics of women exposed and unexposed to environmental tobacco smoke (ETS) in a general population sample of North Italy (Po River Delta epidemiological study)

To define qualitative and quantitative categories of exposure to environmental tobacco smoke (ETS) and to assess possible differences for life-style factors between exposed and unexposed women, we studied 867 nonsmoking women (8-73 aged), selected from a general population sample living in the Po Delta area (near Venice, North Italy). Information was collected by a standardized questionnaire. ETS exposure at home, at work or elsewhere was considered. There was a prevalence of ETS exposure of 46% in the whole sample; the rate had a negative association with age. Exposure to ETS occurred more frequently at home, either singly (56%) or in combination with school/work and other places (75%). Exposed women were significantly younger, taller and lighter than those unexposed. Logistic regression on 20+ aged women showed that single-separated-widowed, workers, women living in a rental house, and women with a central forced air heating were significantly more exposed to ETS. Crowding index (n inhabitants/n rooms of the house) was significantly higher in those exposed. These results indicate that ETS exposure is quite frequent in Italian women and that some life-style factors (e.g. marital status or occupational status or some home characteristics), should be considered in the study of relationship between passive smoking and respiratory health.

Lung tumors in A/J mice exposed to environmental tobacco smoke: estimated potency and implied human risk

Directly inhaled tobacco smoke is a recognized human lung carcinogen, and epidemiological studies suggest relative risks of about 1.2-1.4 for nonsmoking spouses of smokers typically exposed to environmental tobacco smoke (ETS). While many individual ETS components have been shown experimentally to induce lung tumors, ETS itself was only recently shown to induce lung tumors in a series of studies in which strain A/J mice were exposed to well-defined ETS atmospheres. Data from these studies indicate that ETS exposure clearly can increase combined malignant and benign lung tumors in multiple experiments involving male and female A/J mice, and thus provide convincing evidence that ETS is a positive mouse carcinogen. Tumorigenic potencies estimated from these A/J mouse bioassay data predict a corresponding range of increased human risk (0.2-0.5%) that overlaps that implied by case-control studies showing increased lung cancer risks in lifelong nonsmokers married to smokers. In A/J mice exposed to a significantly tumorigenic ETS concentration, lung tumors were found to be significantly smaller than those in corresponding control mice, and mice so exposed for 9 months had significantly fewer tumors/animal than mice exposed for 5 months followed by 4 months in filtered ETS-free air. These findings support hypotheses that ETS does not promote growth of spontaneous neoplastic foci in A/J mice, and that ETS-induced lung-tumor risk in A/J mice occurs predominantly by genotoxic effects that can be suppressed by reduced cell proliferation associated with chronic, high-level ETS exposure. The results obtained add to evidence that A/J mouse lung tumors induced by ETS provide a relevant biological model of ETS-induced human lung tumors.

Gene-environment interaction and aetiology of cancer: what does it mean and how can we measure it?

One form of defence against cancer development involves a series of genes whose role is to metabolize and excrete potentially toxic compounds and to repair subtle mistakes in DNA. Much laboratory and epidemiological research over the past decade has concentrated on the identification of these genes and an assessment of their role in cancer aetiology. Of particular interest has been whether the risk of cancer associated with a particular environmental exposure differs with respect to functionally different polymorphisms of these genes, i.e. gene-environment interaction. A large number of studies have been conducted for numerous genes and also for all common cancer sites, although results have been very inconsistent and therefore inconclusive. This is partially due to the inadequate sample size of most studies to detect modest effects and the over-reporting of positive associations identified in subgroups of the dataset. There is also much confusion about the meaning of "gene-environment interaction", what type of studies should be conducted to study it and also how it should be measured. Furthermore, the very purpose of these studies is not clear; are they attempting to identify high-risk individuals, or are they simply trying to further understand the cancer process? This review will explore these questions and provide some recommendations to help ensure that the next phase of gene-environment interaction studies, which are likely to be much larger and based on many more genes, also provide some clearer answers.

Epidemiology, etiology, and prevention of lung cancer

Over the past century, lung cancer has gone from an obscure disease to the leading cause of cancer death worldwide. Initially an epidemic disease among men in industrialized nations, lung cancer now has become the leading cancer killer in both sexes in the United States and an increasingly common disease of both sexes in developing countries. Lung cancer incidence largely mirrors smoking prevalence, with a latency period of several decades. Other important risk factors for the development of lung cancer include environmental exposure to tobacco smoke, radon, occupational carcinogens, and pre-existing nonmalignant lung disease. Studies in molecular biology have elucidated the role that genetic factors play in modifying an individual's risk for lung cancer. Although chemopreventive agents may be developed to prevent lung cancer, prevention of smoking initiation and promotion of smoking cessation are currently the best weapons to fight lung cancer. No other malignancy has been shown to have such a strong epidemiologic relation between a preventable behavior and incidence of disease. Despite this knowledge, more than 20% of all Americans smoke, and tobacco use is exploding in developing countries. Based on current and projected smoking patterns, it is anticipated that lung cancer will remain the leading cause of cancer death in the world for decades to come.

Alterations of plasma antioxidants and mitochondrial DNA mutation in hair follicles of smokers

The effects of long-term smoking on mitochondrial DNA (mtDNA) deletions in hair follicles were investigated in subjects with different antioxidant capacity. Twenty-two male smokers with a smoking index of greater than 5 pack-years and without any known systemic diseases were recruited for this study. Forty healthy nonsmoking males were included as controls. We found that the concentrations of ascorbate and alpha-tocopherol and the activities of glutathione S-transferase (GST) and glutathione peroxidase in blood plasma were significantly decreased in smokers. The levels of glutathione and protein thiols in whole blood and the incidence of a 4,977 bp deletion of mtDNA (dmtDNA) in hair follicles were significantly increased in smokers. A significantly higher incidence of the 4,977 bp dmtDNA was found in smokers with plasma GST activity less than 5.66 U/l (OR = 7.2, P = 0.020). Using multiple covariate ANOVA and logistic regression, we found that age and low plasma GST activity were the only two risk factors for the 4,977 bp dmtDNA. These results suggest that smoking depletes antioxidants and causes mtDNA deletions and that plasma GST may play an important role in the preservation of the mitochondrial genome in tissue cells of smokers.

Neoplastic transformation of human breast epithelial cells by estrogens and chemical carcinogens

Sporadic breast cancer, the most common cancer diagnosed in American and Northern European women, is gradually increasing in incidence in most Western countries. Prevention would be the most efficient way of eradicating this disease. This goal, however, cannot be accomplished until the specific agent(s) or mechanisms that initiate the neoplastic process are identified. Experimental studies have demonstrated that mammary cancer is a hormone-dependent multistep process that can be induced by a variety of compounds and mechanisms, that is, hormones, chemicals, radiation, and viruses, in addition to or in combination with genetic factors. Although estrogens have been shown to play a central role in breast cancer development, their carcinogenicity on human breast epithelial cells (HBECs) has not yet been clearly demonstrated. Breast cancer initiates in the undifferentiated lobules type 1, which are composed of three cell types: highly proliferating cells that are estrogen-receptor negative (ER-), nonproliferating cells that are ER positive (ER+), and very few (<1%) ER+ cells that proliferate. Interestingly, endogenous 17beta-estradiol (E(2)) is metabolized by the cytochrome P450 enzyme isoforms CYP1A1 and CYP1B1, which also activate benzo[a]pyrene (B[a]P), a carcinogen contained in cigarette smoke. We postulate that if estrogens are carcinogenic in HBECs, they should induce the same transformation phenotypes induced by chemical carcinogens and ultimately genomic changes observed in spontaneously developing primary breast cancers. To test this hypothesis we compared the transforming potential of E(2) on the HBEC MCF-10F with that of B[a]P. Both E(2) and B[a]P induced anchorage-independent growth, colony formation in agar methocel, and loss of ductulogenic capacity in collagen gel, all parameters indicative of cell transformation. In addition, the DNA of E(2)-transformed cells expressed LOH in chromosome 11 at 11q23.3, 11q24.2-q25, and LOH at 13q12-q13. B[a]P-induced cell transformation was also associated with LOH at 13q12-q13 and at 17p13.2. The relevance of these findings is highlighted by the observation that E(2)- and B[a]P-induced genomic alterations in the same loci found in ductal hyperplasia, ductal carcinoma in situ, and invasive ductal carcinoma of the breast.

Glutathione-S-transferase M1, M3, T1 and P1 polymorphisms and susceptibility to non-small-cell lung cancer subtypes and hamartomas

Polymorphic glutathione-S-transferase (GST) genes causing variations in enzyme activity may influence individual susceptibility to lung cancer. In this case-control study (consisting of 389 Caucasian lung cancer patients, including 151 adenocarcinomas (ACs) and 172 squamous cell carcinomas (SCCs), and 353 hospital control subjects without malignant disease, genotype frequencies for GSTM1, GSTM3, GSTP1 and GSTT1 were determined by polymerase chain reaction (PCR)/ restriction fragment length polymorphism (RFLP)-based methods. While adjusted odds ratios (ORs) indicated no significantly increased risk for lung cancer overall due to any single GST genotype, the risk alleles for GSTM1, GSTM3 and GSTP1 conferring reduced enzyme activity were present at higher frequency in SCC than in AC patients. This is consistent with a reduced detoxification of carcinogenic polycyclic aromatic hydrocarbons (PAHs) from cigarette smoke that are more important for the development of SCC than for AC. An explorative data analysis also identified statistically significantly increased ORs for the combinations GSTT1 non-null and GSTP1 GG or AG for lung cancer overall (OR 2.23, CI 1.11-4.45), and for SCC (OR 2.69, CI 1.03-6.99). For lung cancer overall, and especially among SCC patients, the GSTT1 null genotype was underrepresented (SCC 11.2% v. control subjects 19%, P = 0.026, OR 0.57, CI 0.30-1.06). Additionally, in 28 patients with hamartomas, the GSTT1 null genotype was also protective (P = 0.013), while GSTP1 variant allele carriers were overrepresented (OR 2.48, CI 1.06-6.51). In conclusion, GST genotypes may act differently, either by detoxifying harmful tobacco carcinogens and/or by eliminating lung cancer chemopreventive agents. The latter role for GSTT1 would explain the observed lower risk of SCC and hamartoma associated with GSTT1 null. Further confirmatory studies are required.