Abstract

The complexity of tobacco smoke leads to some confusion about the mechanisms by which it causes lung cancer. Among the multiple components of tobacco smoke, 20 carcinogens convincingly cause lung tumors in laboratory animals or humans and are, therefore, likely to be involved in lung cancer induction. Of these, polycyclic aromatic hydrocarbons and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone are likely to play major roles. This review focuses on carcinogens in tobacco smoke as a means of simplifying and clarifying the relevant information that provides a mechanistic framework linking nicotine addiction with lung cancer through exposure to such compounds. Included is a discussion of the mechanisms by which tobacco smoke carcinogens interact with DNA and cause genetic changes—mechanisms that are reasonably well understood—and the less well defined relationship between exposure to specific tobacco smoke carcinogens and mutations in oncogenes and tumor suppressor genes. Molecular epidemiologic studies of gene-carcinogen interactions and lung cancer—an approach that has not yet reached its full potential—are also discussed, as are inhalation studies of tobacco smoke in laboratory animals and the potential role of free radicals and oxidative damage in tobacco-associated carcinogenesis. By focusing in this review on several important carcinogens in tobacco smoke, the complexities in understanding tobacco-induced cancer can be reduced, and new approaches for lung cancer prevention can be envisioned.

Lung cancer continues to be the leading cause of cancer death in both men and women in the United States, with more than 158 900 deaths expected in 1999 ( 1 ). Worldwide, lung cancer kills over one million people each year ( 2 ). Extensive prospective epidemiologic data clearly establish cigarette smoking as the major cause of lung cancer ( 3 ). It is estimated that about 90% of male lung cancer deaths and 75%-80% of female lung cancer deaths in the United States each year are caused by smoking ( 4 , 5 ). The risk of lung cancer diminishes after smoking cessation, but not during the first 5 years, and the relative risk never returns to that of a nonsmoker ( 3 ). In spite of the rising anti-tobacco sentiment in the United States and improvements in smoking cessation methods, approximately 25% of the U.S. adult population, about 47 million people, continues to smoke cigarettes ( 6 ). Although the percentage of adult smokers decreased following the first Surgeon General's report ( 7 ), from 42% in 1965 to 25% in 1990, there has been virtually no change since then, suggesting that we may have reached a hard-core population of smokers ( 8 ). Approximately five hundred billion cigarettes were sold in the United States in 1995 ( 9 ). There are one billion cigarette smokers worldwide, one third of whom live in China, where a major epidemic of lung cancer is predicted ( 10 , 11 ). Although the argument for further tobacco control and improved cessation strategies is powerful, the numbers tell us that the utopian goal of a smoke-free society is still distant ( 6 ). Moreover, exposure to environmental tobacco smoke (ETS) is widely accepted as a cause of lung cancer, although the risk is far lower than that of smoking and can be difficult to demonstrate, even in large studies ( 12 - 16 ). An understanding of mechanisms of tobacco-induced lung cancer will lead to new strategies for decreasing lung cancer risk, for identifying highly susceptible individuals, and for developing innovative techniques for early detection.

Even in the writings of distinguished scientists with great expertise in cancer causes and mechanisms, one can read statements such as: “The carcinogenic mechanisms of tobacco smoking are not well understood” ( 17 ). This review will attempt to provide the generally informed cancer scientist with a distillation of mechanistic information on the subject of tobacco smoke carcinogens and lung cancer and to convince the reader that we know a great deal about the mechanisms by which these carcinogens cause lung cancer. While it is true that we may never be able to map each detail of the complex process by which cigarette smoking causes lung cancer and that there is unlikely to be a single mechanism of tobacco carcinogenesis, there are general principles that have emerged from intensive research in the past four to five decades. The overall framework for discussing this information is illustrated in Fig. 1. Carcinogens form the link between nicotine addiction and lung cancer. Nicotine addiction is the reason that people continue to smoke ( 18 ). While nicotine itself is not considered to be carcinogenic, each cigarette contains a mixture of carcinogens, including a small dose of polycyclic aromatic hydrocarbons (PAHs) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) among other lung carcinogens, tumor promoters, and co-carcinogens ( 19 , 20 ). Carcinogens such as NNK and PAHs require metabolic activation to exert their carcinogenic effects; there are competing detoxification pathways, and the balance between metabolic activation and detoxification differs among individuals and will affect cancer risk.

We know a great deal about mechanisms of carcinogen metabolic activation and detoxification ( 21 - 25 ). The metabolic activation process leads to the formation of DNA adducts, which are carcinogen metabolites bound covalently to DNA, usually at guanine or adenine. There have been major advances in our understanding of DNA adduct structure and its consequences in the past two decades, and we now have a large amount of mechanistic information ( 26 , 27 ). If DNA adducts escape cellular repair mechanisms and persist, they may lead to miscoding, resulting in a permanent mutation. As a result of clever strategies that combine DNA adduct chemistry with the tools of molecular biology ( 28 ), we know a great deal about the ways in which carcinogen DNA adducts cause mutations. Cells with damaged DNA may be removed by apoptosis, or programmed cell death ( 29 , 30 ). If a permanent mutation occurs in a critical region of an oncogene or tumor suppressor gene, it can lead to activation of the oncogene or deactivation of the tumor suppressor gene. Multiple events of this type lead to aberrant cells with loss of normal growth control and, ultimately, to lung cancer. While the sequence of events has not been as well defined as in colon cancer, there can be little doubt that these molecular changes are important ( 29 , 30 ). There is now a large amount of data on mutations in the human KRAS and p53 (also known as TP53) genes in lung tumors from smokers, and attempts have been made to link these mutations to specific carcinogens in tobacco smoke ( 30 - 36 ). Blocking any of the horizontal steps in Fig. 1 may lead to decreased lung cancer, even in people who continue to smoke.

This review will focus on tobacco smoke carcinogens and will consider certain aspects of the mechanistic pathway illustrated in Fig. 1 . It will discuss pulmonary carcinogens in cigarette smoke, inhalation studies, and investigations of lung carcinogen uptake, metabolism, and DNA adduct formation in humans. It will also consider other mechanisms of DNA damage via free radicals and reactive oxygen species. It will discuss mutations in oncogenes and tumor suppressor genes and their possible relationship to specific carcinogens and molecular epidemiologic investigations of carcinogen-gene interactions. On the basis of these data, it will evaluate the role of specific cigarette smoke carcinogens and other factors as causes of lung cancer. A detailed account of other aspects of the molecular pathogenesis of lung cancer has recently been published ( 30 ).

The goal of this review is to be illustrative rather than inclusive. Any of the topics mentioned in the previous paragraph would exceed the space limitations of this Journal if presented completely. This review used MEDLINE®, the International Agency for Research on Cancer Monographs on the Evaluation of Carcinogenic Risks to Humans, the Survey of Compounds Which Have Been Tested for Carcinogenic Activity, and selected previous reviews and key references to identify references on specific topics.

P ulmonary C arcinogens in C igarette S moke

The mainstream smoke emerging from the mouthpiece of a cigarette is an aerosol containing about 10 10 particles/mL ( 20 ). About 95% of the smoke is made up of gases, chiefly nitrogen, oxygen, and carbon dioxide. In experiments, these vapor-phase components are separated from the particulate phase by a glass-fiber filter. The particulate phase contains at least 3500 compounds and most of the carcinogens ( 20 ). The components of cigarette smoke and how they have changed over time have been reviewed previously ( 19,20,37,38 ).

There are 55 carcinogens (Table 1, A ) in cigarette smoke that have been evaluated by the International Agency for Research on Cancer (IARC) and for which there is “sufficient evidence for carcinogenicity” in either laboratory animals or humans ( 19 ). Other carcinogens not evaluated by the IARC may also be present. For example, among the PAHs, multiple alkylated and high-molecular-weight compounds have been detected but are incompletely characterized with respect to their carcinogenicity ( 39 , 40 ). Individual pulmonary carcinogens in cigarette smoke, selected from the classes of carcinogens in Table 1 , A , are listed in Table 1 , B . The 20 compounds included in this list have been found convincingly to induce lung tumors in at least one animal species and have been positively identified in cigarette smoke. The structures of the organic compounds are shown in. Fig. 2

Among the PAHs, benzo[ a ]pyrene (BaP) is the most extensively studied compound, and its ability to induce lung tumors upon local administration or inhalation is well documented ( 41,42,62,63 ). When administered systemically, it causes lung tumors in mice, but not in rats ( 41,42,64 ). In studies of lung tumor induction by implantation in rats, BaP is more carcinogenic than the benzofluoranthenes or indeno[1,2,3- cd ]pyrene ( 43 ). In analytic studies, it has often been used as a surrogate for other PAHs, and extensive data on its occurrence in cigarette smoke are available ( 19 , 38 ). Thus, BaP is a potent lung carcinogen, the occurrence of which is well documented. The vast literature on BaP tends to distract attention from other PAHs. However, PAHs such as dibenz[ a,h ]anthracene, 5-methylchrysene, and dibenzo[ a,i ]pyrene are substantially stronger lung tumorigens than BaP in mice or hamsters, although the levels of these compounds in cigarette smoke are lower than those of BaP ( 44 , 45 ). The presence in cigarette smoke of dibenzo[ a,l ]pyrene, a highly carcinogenic PAH, has not been confirmed.

Two aza-arenes, dibenz[ a,h ]acridine and 7H-dibenzo[ c,g ]carbazole, are pulmonary tumorigens when tested by implantation in the rat lung and instillation in the hamster trachea, respectively ( 46 , 47 ). The activity of dibenz[ a,h ]acridine is significantly less than that of BaP, while the activity of 7H-dibenzo[ c,g ]carbazole is greater than that of BaP. The levels of both compounds in cigarette smoke are relatively low.

Among the N -nitrosamines, N -nitrosodiethylamine is an effective pulmonary carcinogen in the hamster, but not in the rat ( 48 , 49 ). Its levels in cigarette smoke are low compared with those of other carcinogens. The tobacco-specific N -nitrosamine NNK is a potent lung carcinogen in rats, mice, and hamsters ( 22 ). It is the only compound in Table 1 , B , that induces lung tumors systemically in all three commonly used rodent models. The organospecificity of NNK for the lung is remarkable; it induces tumors of the lung, mainly adenoma and adenocarcinoma, independent of the route of administration and in both susceptible and resistant strains of mice (Table 2 ) ( 22 ). NNK has not been tested by local administration in the respiratory tract. The systemic administration of NNK to rats is a reproducible and robust method for the induction of lung tumors; dose-response data from two laboratories are summarized in Fig. 3 ( 22 ). Cigarette smoke contains substantial amounts of NNK ( 19,38,65-67 ), and the total dose experienced by a smoker in a lifetime of smoking is remarkably close to the lowest total dose shown to induce lung tumors in rats ( 22 ). Levels of NNK and total PAHs in cigarette smoke are similar ( 20 ).

The lung is one of the multiple sites of tumorigenesis by 1,3-butadiene in mice, but it is not a target in the rat ( 51 ). 1,3-Butadiene is a component of the vapor phase of cigarette smoke, but in most inhalation studies the particulate phase shows more overall carcinogenic activity. Ethyl carbamate is a well-established pulmonary carcinogen in mice, but not in other species ( 52 ). Nickel, chromium, cadmium, and arsenic are all present in tobacco, and a percentage of each is transferred to mainstream smoke; arsenic levels are substantially lower since discontinuation of its use as a pesticide in 1952 ( 20,37,38 ). Metal carcinogenicity depends on the valence state and anion; these are poorly defined in many analytical studies of tobacco smoke. Thus, although some metals are effective pulmonary carcinogens, the role of metals in tobacco-induced lung cancer is murky. Levels of polonium-210 in tobacco smoke are not believed to be great enough to significantly impact lung cancer in smokers ( 68 ). Hydrazine is an effective lung carcinogen in mice and has been detected in cigarette smoke in limited studies ( 38 , 60 ).

The carcinogens listed in Table 1 , B , are also found in ETS ( 61 ). Sidestream smoke, the material released directly into the air from the burning tip of a cigarette plus that which diffuses through the cigarette paper, constitutes the major portion of ETS ( 61 ). Some sidestream-mainstream ratios are presented in Table 1 , B . While these ratios are generally greater than 1, dilution with ambient air is such that passive uptake will be far less than uptake in a smoker, and the risk for lung cancer is accordingly less ( 69 ).

Cigarette smoke is also a tumor promoter ( 38 , 70 ). The majority of the activity seems to be due to uncharacterized weakly acidic compounds. Substantial levels of cocarcinogens such as catechol are present in cigarette smoke ( 70 ). Other co-carcinogens include methylcatechols, pyrogallol, decane, undecane, pyrene, benzo[ e ]pyrene, and fluoranthene. In addition, cigarette smoke contains high levels of acrolein, which is toxic to the pulmonary cilia, and other agents, such as nitrogen oxides, acetaldehyde, and formaldehyde, that could contribute indirectly to pulmonary carcinogenicity ( 38 ).

I nhalation S tudies of C igarette S moke

While extensive studies clearly document the carcinogenicity of certain cigarette smoke constituents, the results of inhalation studies of whole-cigarette smoke or its vapor and particulate phases have been less consistent. Cigarette smoke inhalation studies through 1985 have been reviewed elsewhere ( 38 ). There are a number of operational problems inherent in these experiments. The smoke must be delivered in a standardized fashion that has been accomplished with a variety of designs. Both whole-body exposure and nose-only designs have been used. Generally, a 2-second puff from a burning cigarette is diluted with air and forced into the chamber. Animals will undergo avoidance reactions and will not inhale the smoke the way humans do. Thus, the dose to the lung in animals will be less than that in humans. It will also be considerably less than in most experiments that examine the carcinogenicity of individual components of smoke. Other problems arise from the fact that rodents are obligatory nose breathers and their nasal passages are more complex than those of humans, thereby affecting the dynamics of particle deposition in the respiratory tract. The irritating and toxic properties of tobacco smoke create further difficulties.

Nevertheless, in experiments with Syrian golden hamsters, whole-cigarette smoke and its particulate phase consistently induce preneoplastic lesions and benign and malignant tumors of the larynx ( 38 ). This model system has been widely applied and is the most reliable one for induction of tumors by inhalation of cigarette smoke. Tumors are observed in hamsters exposed to the particulate phase of smoke only. Results of experiments in rats and mice are inconsistent, while those of experiments in rabbits and dogs are equivocal. Studies published since 1985 describe inhalation experiments with mice ( 71 - 74 ). Two studies are negative, but two others evaluating the activity of ETS in A/J mice show moderately positive results. In these studies ( 73 , 74 ), increased lung tumor multiplicity is observed in mice exposed to ETS and then allowed a recovery period. It was concluded that the vapor phase of ETS is as tumorigenic as is full ETS and that the responsible agents are not NNK or BaP. These studies require confirmation. Further research is needed to identify the putative tumorigenic components of the vapor phase.

P ulmonary C arcinogens : U ptake , M etabolism , and A dduct F ormation in S mokers

Carcinogens are enyzmatically transformed to a series of metabolites as the exposed organism attempts to convert them to forms that are more readily excreted. The initial steps are usually carried out by cytochrome P450 (P450) enzymes, encoded by the CYP family of genes, which oxygenate the substrate ( 75 ). Other enzymes, such as lipoxygenases, cyclooxygenases, myeloperoxidase, and monoamine oxidases, may also be involved, but less frequently. The oxygenated intermediates formed in these initial reactions may undergo further transformations by glutathione S -transferases, uridine-5′-diphosphate-glucuronosyltransferases, sulfatases, and other enzymes ( 76 - 78 ). Some of the metabolites produced by the P450s react with DNA or other macromolecules to form covalent binding products known as adducts. This is referred to as metabolic activation; other reactions are considered as detoxification pathways with respect to carcinogenesis. Metabolic pathways of BaP and NNK, representative pulmonary carcinogens in cigarette smoke, are outlined in Fig. 4 ( 21,22,42,79-100 ). These have been extensively studied in rodent and human tissues. Multiple enzymes participate in many steps; some of the human forms involved are indicated in Fig. 4 . The major metabolic activation pathway of BaP is conversion to its 7,8-diol-9,10-epoxides (BPDE); one of the four enantiomers is highly carcinogenic and reacts with DNA to form adducts with N2 of deoxyguanosine. The major metabolic activation pathways of NNK and its main metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), occur by hydroxylation of the carbons adjacent to the N -nitroso group (α-hydroxylation), which leads to the formation of two types of DNA adducts: methyl adducts, such as 7-methyguanine or O6 -methylguanine, and pyridyloxobutyl adducts. O6 -Methylguanine plays a critical role in mouse lung tumorigenesis by NNK, while this adduct as well as pyridyloxobutyl DNA adducts are important in lung tumor induction by NNK in rats ( 22 ).

Considerable information is available on pulmonary carcinogen metabolism in vitro, both in animal and in human tissues, but fewer studies have been carried out on uptake, metabolism, and adduct formation of cigarette smoke lung carcinogens in smokers. Various measures of cigarette smoke uptake in humans have been used, including exhaled carbon monoxide, carboxyhemoglobin, thiocyanate, and urinary mutagenicity ( 38 ). However, the most specific and widely used biochemical marker is the nicotine metabolite cotinine ( 38 , 101 ). While cotinine and other nicotine metabolites are excellent indicators of tobacco smoke constituent uptake by smokers, the NNK metabolites NNAL and its O -glucuronide (NNAL-Gluc) are excellent biomarkers of tobacco smoke lung carcinogen uptake ( 22 ). NNAL is a potent pulmonary carcinogen like NNK, while NNAL-Gluc is a detoxified metabolite of NNK ( 22 ). Since NNK is a tobacco-specific carcinogen, its metabolites NNAL and NNAL-Gluc are found only in the urine of individuals exposed to tobacco products. Urinary NNAL and NNAL-Gluc have been quantified in several studies of smokers and in nonsmokers exposed to ETS ( 22,102-107 ). The ETS results demonstrate that uptake of NNAL-Gluc by nonsmokers is 1%-3% of that in smokers, consistent with the weaker epidemiologic evidence for a role of ETS, compared with mainstream cigarette smoke, as a cause of lung cancer ( 69 , 107 ). Levels of cotinine plus cotinine- N -glucuronide in smokers' urine are correlated with urinary NNAL plus NNAL-Gluc (Fig. 5 ). Similar correlations are observed in passively exposed nonsmokers ( 103 , 107 ).

Since NNAL is a potent lung carcinogen, but NNAL-Gluc is not carcinogenic, the ratio of NNAL-Gluc to NNAL has been suggested as a potential biomarker of susceptibility to lung cancer ( 104 ). This ratio varies widely in smokers ( 104 ). It is interesting that the NNAL-Gluc : NNAL ratio was significantly lower in black smokers than in white smokers, which suggests that poor detoxification potential may be one factor contributing to the higher incidence and mortality rates of lung cancer in blacks than in whites ( 109 , 110 ) have clearly demonstrated that serum cotinine levels are higher in blacks than in whites. This is postulated to result from higher nicotine intake per cigarette and slower clearance of cotinine in blacks.

BaP and benzo[ k ]fluoranthene have been detected in human lung; no differences between smokers and nonsmokers were noted ( 111 , 112 ). 1-Hydroxypyrene and its glucuronide, urinary metabolites of the noncarcinogen pyrene, have been widely used as indicators of PAH uptake. 1-Hydroxypyrene levels in smokers are generally higher than those in nonsmokers ( 113 - 115 ). Other studies ( 116 - 122 ) have examined PAHs in urine by reconversion of metabolites to the parent compounds or have detected specific PAH metabolites, including 3-hydroxy BaP and tetraols resulting from hydrolysis of BPDE. No firm conclusions on the effects of smoking can be drawn from these latter studies because the number of subjects is too small. Uptake of polonium-210 has been examined in bronchial tissues of smokers and nonsmokers; some studies [ reviewed in ( 38 )] have shown higher concentrations in smokers. Overall, there is considerable evidence that pulmonary carcinogens in cigarette smoke are taken up and metabolized by smokers (as well as by nonsmokers exposed to ETS), but there are still large gaps.

Fewer than 20% of smokers will get lung cancer ( 38 ). Susceptibility will depend in part on the balance between carcinogen metabolic activation and detoxification in the smokers. This is an important area requiring intense further study. Most investigations have focused on the activation pathways by quantifying DNA or hemoglobin adducts. Other molecular epidemiologic studies have used genotyping approaches, as discussed later. A series of reports by Bartsch et al. ( 123 ) provides considerable support for the activation of BaP to form DNA adducts in the lungs of smokers. Earlier investigations [reviewed in ( 38 )] demonstrated that cigarette smoke induces aryl hydrocarbon hydroxylase (AHH) activity and proposed a relationship between AHH activity and lung cancer. The AHH assay measures conversion of BaP to 3-hydroxy BaP, which is mediated mainly by P4501A1 in human lung ( 88 - 90 ). Therefore, cigarette smoking induces CYP1A1 gene expression. Cancer patients who stopped smoking within 30 days of surgery had elevated levels of AHH activity compared with nonsmoking cancer patients ( 124 , 125 ). Lung tissue from recent smokers with elevated AHH activity also converted BaP-7,8-diol to tetraols to a greater extent than lung tissue from nonsmokers or ex-smokers ( 126 ). Subsequently ( 127 ), BPDE-DNA adducts were quantified in human lung tissue by high-pressure liquid chromatography-fluorescence of released tetraols; adduct levels were found to be associated with AHH activity in the same samples. In an additional study ( 128 ), tetraols released from BPDE-DNA adducts were detected only in lung tissue of individuals null for the glutathione S -transferase M1 (GSTM1) gene; among these, a group of subjects with mutated CYP1A1 showed the highest adduct levels. Collectively, these results support the existence of a cigarette smoke-inducible pathway leading to BPDE-DNA adducts in smokers' lungs, as illustrated in Fig. 1 and 4 ; however, larger studies are necessary to confirm these results. Epidemiologic studies on polymorphisms in carcinogen-metabolizing enzymes, such as CYP1A1 and GSTM1, are discussed in more detail below.

Fluorescence and phosphorescence techniques have also been used to identify tetraols released from BPDE-DNA adducts in human lung ( 129 , 130 ). Many studies ( 131 - 137 ) have used immunoassays and 32 P-postlabeling to estimate levels of “PAH-DNA adducts” or “hydrophobic DNA adducts” in white blood cells and other human tissues including the lung. Many of these have shown elevated adduct levels in smokers. One series of studies ( 138 , 139 ) demonstrated higher levels of adducts and p53 mutations in lung DNA of women than men, consistent with the higher risk for lung cancer observed in some epidemiologic studies ( 140 ). However, none of the studies using immunoassays and 32 P-postlabeling has identified the structures of the compounds leading to adduct formation. Probably some are PAHs, but individual PAHs differ widely in carcinogenic activity; thus, the results are difficult to interpret. PAH diol epoxides such as BPDE form adducts with hemoglobin and albumin ( 141 - 148 ). Tetraols released by hydrolysis of these adducts have been quantified by gas chromatography-mass spectrometry (GC-MS) and are higher in smokers than in nonsmokers ( 146 - 148 ).

Several studies ( 149 - 154 ) have detected 7-methyldeoxyguanosine in human lung. Levels were higher in smokers than in nonsmokers in two of these ( 151 , 154 ), suggesting that NNK may be one source of these adducts. Another likely source is N -nitrosodimethylamine. 7-Ethyldeoxyguanosine has also been detected ( 149 , 153 ). While 7-methylguanine is not generally considered as a miscoding adduct, other methyl adducts which do have miscoding properties, such as O6 -methylguanine, are formed at the same time, but at lower levels. One study ( 155 ) did report the presence of O6 -methylguanine and O6 -ethylguanine in the lung. Pyridyloxobutylated DNA has been detected by GC-MS analysis of lung tissue from smokers in one study, reflecting metabolic activation of NNK or a related nitrosamine, N ′-nitrosonornicotine; a second study was negative ( 153 , 156 ). The detection of methyl and pyridyloxobutyl adducts in DNA from smokers' lungs is consistent with the ability of human lung tissue to metabolically activate NNK, but the quantitative aspects of the relationship of metabolism to DNA adduct levels are unclear ( 22 ). Pyridyloxobutylated globin has also been detected in smokers ( 22,157-160 ). Adduct levels in smokers were lower than BPDE globin adduct levels, probably reflecting the lower stability of the diazonium ion intermediates formed from NNK or N ′-nitrosonornicotine compared with BPDE ( 22 ). Levels of 3-ethyladenine in urine were higher in smokers than in nonsmokers; some of the excreted 3-ethyladenine could be formed as a result of metabolic activation of N -nitrosodiethylamine ( 161 , 162 ).

DNA repair processes are important in determining whether DNA adducts persist. Because smoking is a chronic habit, one would expect a steady-state DNA adduct level to be achieved by the opposing effects of damage and repair. There are three mechanisms of DNA repair: direct repair, base excision repair, and nucleotide excision repair. These topics have been reviewed elsewhere ( 163 - 165 ). With respect to smoking and lung cancer, direct repair of O6 -methyldeoxyguanosine by O6 -methylguanine-DNA alkyltransferase (AGT) and nucleotide excision repair of PAH-DNA adducts would appear to be the most relevant processes. AGT removes the methyl group from the O6 -position of deoxyguanosine in a stoichiometric reaction, reconverting it to deoxyguanosine ( 164 ). Several studies have examined levels of this repair enzyme in tissues from smokers and nonsmokers. In broncho-alveolar lavage cells and peripheral blood mononuclear cells, there was a wide interindividual variation in activity but no effect of smoking ( 166 ). In human lung tissue and in human placenta, small but statistically significant increases in AGT activity were observed in smokers compared with nonsmokers ( 167 , 168 ). Expression of AGT was higher in non-small-cell lung carcinomas from smokers than from nonsmokers ( 169 ). In smokers, AGT would repair O6 -alkylguanines formed from NNK, N -nitrosodimethylamine, or N -nitrosodiethylamine. In rats treated with NNK, AGT activity decreases in Clara cells, the nonciliated cells in the epithelial lining of the bronchioles ( 171 - 173 ) show that pyridyloxobutylated DNA inhibits the activity of AGT in mice. BPDE-DNA adducts and other PAH-DNA adducts are repaired by nucleotide excision repair ( 174 ). In human cells, repair of BPDE adducts in the hypoxanthine phosphoribosyltransferase gene occurs preferentially in the transcribed strand ( 175 ). Repair of the BPDE-DNA adducts is highly dependent on adduct conformation ( 176 ). Thus, cis -adducts of BPDE with N2 of deoxyguanosine are repaired more rapidly than trans -adducts; rates of repair are also highly dependent on the nature of the base opposite the adduct ( 176 ). DNA repair capacity has been studied with respect to lung cancer susceptibility ( 177 ); this is discussed further below. The effects of smoking on nucleotide excision repair in the human lung do not seem to have been examined.

F ree R adicals in C igarette S moke and O xidative DNA D amage

Cigarette smoke contains free radicals and induces oxidative damage in humans. The gas phase of freshly generated cigarette smoke contains up to 600 μg of nitric oxide ( 38 ). The particulate phase contains free radicals that are stable enough to be detected by electron spin resonance and spin trapping ( 178 , 179 ). The major free radical species was postulated to be a quinone-hydroquinone complex “held in a tar matrix” ( 180 ). Further investigation ( 181 ) led to the hypothesis that the tar radical system is an equilibrium mixture of semiquinones, hydroquinones, and quinones. It is suggested that this free radical complex causes redox cycling that generates superoxide anion from molecular oxygen and leads to the formation of hydrogen peroxide and hydroxyl radical ( 181 ). The reactive species generated in this cascade cause DNA nicking ( 181 ). Other studies ( 182 - 187 ) demonstrate that cigarette smoke causes single-strand breaks in DNA of cultured rodent and human cells. Quinone-associated redox cycling may also be involved in these effects; hydroquinone and catechol are believed to play major roles. It has been shown that nitric oxide in the gas phase acts synergistically with cigarette “tar” to cause DNA single-strand breakage in pBR322 plasmid DNA ( 188 ). It was suggested that peroxynitrite, generated from nitric oxide and superoxide anion, might be involved in this effect ( 188 ). Another study ( 189 ) also suggests a role for peroxynitrite in oxidative stress induced by aqueous cigarette smoke fractions.

Experiments in vitro demonstrate that the gas phase of cigarette smoke causes lipid peroxidation of human blood plasma; this is prevented by the addition of ascorbic acid ( 190 ). Both whole-cigarette smoke and gas-phase cigarette smoke cause formation of carbonyls in human plasma ( 191 ). Ascorbic acid levels are lower in smokers than in nonsmokers; only smokers consuming more than 200 mg of ascorbic acid per day had serum ascorbate concentrations equivalent to those in nonsmokers who meet the recommended dietary allowance of ascorbic acid ( 192 ). Convincing evidence of oxidative damage by cigarette smoke was provided by measurements of increased circulating products of lipid peroxidation (F 2 -isoprostanes) in smokers ( 193 ). Consistent with these findings and the possible role of reactive oxygen species in DNA damage as discussed above, several studies ( 194 - 196 ) have demonstrated moderately increased levels of 8-oxodeoxyguanosine, a miscoding adduct, in DNA from smokers' lungs, leukocytes, and sperm. Increased urinary excretion of 8-hydroxydeoxyguanosine has also been noted ( 197 , 198 ).

E ffects of T obacco S moke C arcinogens on T umor S uppressor G enes and O ncogenes

As indicated in Fig. 1 , the direct interaction of metabolically activated carcinogens with critical genes, such as the p53 tumor suppressor gene and the Kirsten-ras (KRAS) oncogene, is central to the hypothesis that specific carcinogens form the link between nicotine addiction and lung cancer. In this section, evidence for that link will be considered. By far, the most extensive studies of this type have concerned the p53 tumor suppressor gene. These have been reviewed previously ( 34 , 35 ). The p53 gene plays a central role in the delicate balance of cellular proliferation and death. It is mutated in about half of all cancer types, including more than 50% of lung cancers ( 34 , 35 ). Point mutations at G are common ( 34 , 35 ). In a sample of 550 p53 mutations in lung tumors, 33% were G→T transversions, while 26% were G→A transitions ( 36 ). (A purine→pyrimidine or pyrimidine→purine mutation is referred to as a transversion, while a purine→purine or pyrimidine→pyrimidine mutation is called a transition.) A positive relationship between lifetime cigarette consumption and the frequency of p53 mutations and of G→T transversions on the nontranscribed DNA strand also has been noted ( 34,35,199 ). These observations are generally consistent with the fact that most activated carcinogens react predominantly at G and that repair of the resulting adducts would be slower on the nontranscribed strand, and thus support the hypothesis outlined in Fig. 1 .

However, attempts to link p53 mutations to specific carcinogens or to endogenous processes are more speculative. Many factors will influence the type of mutation. These include the type of DNA adduct formed, the extent to which it is repaired, its sequence context, and the DNA polymerases involved. It is widely stated that G→A transitions at CpG sites in the p53 gene result from deamination of 5-methylC, and although this is a plausible result of endogenous processes that would cause this change, definitive evidence that this occurs in vivo, or in the lung, is lacking. Indeed, a recent study ( 200 ) demonstrates that cytosine methylation greatly enhances guanine alkylation at all CpG sites in the p53 gene by a variety of carcinogens. O6 -Alkylguanines, such as those formed from nitrosamines, are another likely cause of G→A transitions ( 28 ). With respect to the origin of G→T transversions in the p53 gene, a study by Denissenko et al. ( 201 ) is widely quoted as having provided definitive evidence that BPDE is responsible. These investigators did demonstrate that BPDE selectively forms adducts at CpG sites in codons 157, 248, and 273 similar to three major sites of mutation in the p53 gene in lung cancer. However, their studies ( 200 , 202 ) also clearly show that methylated CpG sites are targets of a variety of activated carcinogens, as mentioned above. Thus, the results strongly suggest that other DNA-reactive compounds and DNA adducts derived from tobacco smoke would have similar effects. These include diol epoxides of other PAHs, pyridyloxobutylating intermediates derived from NNK and N ′-nitrosonornicotine, hydroxylamines derived from aromatic amines, as well as acrolein, crotonaldehyde, and 8-oxodeoxyguanosine ( 203 - 208 ). All of these reactive compounds or adducts can cause G→T transversions, although the results may vary depending on other factors such as sequence context as noted above. In summary, while it is likely that cigarette smoke carcinogens are responsible for a substantial percentage of the G mutations observed in the p53 gene from human lung cancers, the assignment of these mutations to specific carcinogens is at best speculative.

Mutations in codon 12 of the KRAS gene are found in 24%-50% of human primary adenocarcinomas but are rarely seen in other lung tumor types ( 31 - 33 ). These mutations are more common in smokers and exsmokers than in nonsmokers, which suggests that they may be induced by direct reaction with the gene of an activated tobacco smoke carcinogen ( 33 ). The most commonly observed mutation is GGT→TGT, which typically accounts for about 60% of the codon 12 mutations, followed by GGT→GAT (20%) and GGT→GTT (15%). This is quite similar to the pattern observed in lung tumors from mice treated with BaP, 5-methylchrysene, and benzo[ b ]fluoranthene, three pulmonary carcinogens found in tobacco smoke ( 209 ). However, caution is again required because numerous constituents of tobacco smoke, as discussed above, can induce G→T transversions. Moreover, whereas Kras mutations are commonly observed in mouse lung tumors, they are rarely found in rat lung tumors, such as those induced by NNK; rodent lung tumors also rarely contain mutated p53 genes ( 22 , 210 ). In the mouse, the O 6 -methylguanine pathway of NNK metabolic activation is dominant, resulting in a high percentage of GGT→GAT mutations in codon 12 of Kras ( 22 ). But pyridyloxobutylation leads to more G→T than G→A mutations in codon 12 ( 207 ). In the rat, both pyridyloxobutylation and methylation pathways are critical in lung tumorigenesis by NNK ( 22 ). We do not know the relative importance of these pathways in human lung. If pyridyloxobutylation is critical, as in the rat, a higher percentage of G→T transversions would be expected as a result of NNK exposure than is observed in mice.

The p16 INK4a tumor suppressor gene is inactivated in more than 70% of human non-small-cell lung cancers, via homozygous deletion or in association with aberrant hypermethylation of the promoter region ( 211 - 213 ). In the rat, 94% of adenocarcinomas induced by NNK were hypermethylated at the p16 gene promoter ( 213 ). This change was frequently detected in hyperplastic lesions and adenomas, which are precursors to the adenocarcinomas induced by NNK. Similar results were found in human squamous cell carcinomas of the lung ( 213 ). The p16 gene was coordinately methylated in 75% of carcinoma in situ lesions adjacent to squamous cell carcinomas that had this change. Methylation of p16 was associated with loss of expression in tumors and precursor lesions, indicating functional inactivation of both alleles. Aberrant methylation of p16 has been suggested as an early marker for lung cancer ( 213 ). The expression of cell cycle proteins is related to the p16 and retinoblastoma (RB) genes; NNK-induced mouse lung tumors appear to resemble human non-small-cell lung cancer in the expression of cell cycle proteins ( 214 ). The estrogen receptor gene is also inactivated through promoter methylation. There was concordance between the incidence of promoter methylation in this gene in lung tumors from smokers and from NNK-treated rodents ( 215 ).

Loss of heterozygosity and exon deletions within the fragile histidine triad (FHIT) gene are associated with smoking habits in lung cancer patients and have been proposed as a target for tobacco smoke carcinogens ( 216 ). However, point mutations within the coding region of the FHIT gene were not found in primary lung tumors. Data are insufficient at present to attempt to relate these changes to specific carcinogens.

M olecular E pidemiologic S tudies I nvolving P ossible G ene -C arcinogen I nteractions and R elated F actors

Molecular epidemiology attempts to integrate biomarkers into epidemiologic investigations, thus providing mechanistic insights into cancer susceptibility with the ultimate goal of identifying individuals at high risk. This has been the subject of recent reviews ( 217 - 220 ). Lung cancer, in particular, has been studied quite extensively with respect to potential interactions between carcinogen metabolizing enzymes and tobacco smoke carcinogens, with the aim of identifying smokers at high risk for this disease. These studies ( 218 - 220 ) have been reviewed by a number of authors. Among genes for carcinogen-metabolizing enzymes, polymorphisms [variants occurring in more than 1% of the population ( 217 )] in the cytochrome P450 genes CYP1A1, CYP2D6, CYP2E1 and in mu-class glutathione S -transferase (GSTM1) have received the most attention.

The CYP1A1 gene product, P4501A1 or AHH, is inducible by cigarette smoke in human lung and is involved in the metabolism of PAHs. Polymorphisms in this gene and their relationship to lung cancer risk have been discussed elsewhere ( 221 - 224 ). While there is some evidence that a CYP1A1 polymorphism may confer higher lung cancer risk in Japanese people, this has not been generalizable to other populations ( 220 , 221 ). Limited data are available on the functional significance of such polymorphisms with respect to PAH metabolism and carcinogenesis ( 222 - 224 ). There is no doubt that P4501A1 is important in the metabolism of PAHs, as illustrated for BaP in Fig. 4 . However, P4501A1 is involved both in the metabolic activation of BaP to BPDE and in its detoxification (via formation of 3-hydroxy BaP and other metabolites). Therefore, it is not clear what the meaning of a variant CYP1A1 genotype would be with respect to lung cancer risk.

The CYP2D6 gene product metabolizes drugs such as the antihypertensive drug debrisoquine. The role of this gene as a risk factor for lung cancer has been extensively studied since the original report demonstrating under-representation of the poor-metabolizing phenotype in smokers diagnosed with lung cancer ( 220,225-227 ). Numerous subsequent studies have examined this relationship using various approaches; the literature has been reviewed elsewhere ( 220 , 226 ). P450 2D6 is expressed primarily in the liver; enzyme activity, protein expression, and gene expression have not been reported in human lung ( 220 ). A recent case-control study ( 227 ) identified inactivating mutations at the CYP2D6 locus as well as mutations that impair but do not abolish enzyme activity. Compared with subjects with homozygous-inactivating mutations, no association with lung cancer was observed for those individuals with homozygous or heterozygous functional alleles ( 227 ). Overall, evidence for a role of CYP2D6 polymorphisms as a risk factor for lung cancer is weak, conflicting, and inconclusive ( 220,226,227 ). On the basis of two studies that showed that P4502D6 can activate NNK ( 228 , 229 ), this carcinogen is frequently mentioned as the substrate for P4502D6 that would be relevant to the proposed lung cancer risk. However, other studies [reviewed in ( 22 )] definitively show that P4502D6 is at most a minor contributor to NNK metabolism. Therefore, there is little theoretical basis for a role of CYP2D6 in lung cancer, which is consistent with the inconclusive molecular epidemiologic studies discussed above.

The CYP2E1 gene product is involved in the metabolism of low-molecular-weight compounds, such as ethanol, 1,3-butadiene, N -nitrosodimethylamine, N -nitrosodiethylamine, and, to a minor extent, NNK. It is expressed in human liver, kidney, brain, and lung ( 220 ). The possible association of CYP2E1 polymorphisms with lung cancer has been reviewed elsewhere ( 220 ). The evidence up until that time was generally inconclusive, but a recent study ( 230 ) showed a 10-fold decrease in risk for overall lung cancer and adenocarcinoma with variant genotypes of CYP2E1, consistent with a role for N -nitrosamines in adenocarcinoma of the lung.

The GSTM1 gene codes for M or mu class glutathione S -transferases that are involved in the detoxification of various carcinogens including PAH diol epoxides. Other human glutathione S -transferases fall into the alpha, pi, and theta classes, and these are named GSTA, GSTP, or GSTT, respectively ( 76 ). Approximately 40%-50% of the human population has the GSTM1 null genotype ( 220 ). A large number of studies have examined the relationship between GSTM1 null and lung cancer risk, testing the hypothesis that risk would be elevated in GSTM1 null individuals. These studies have been reviewed elsewhere ( 220 ). Collectively, the data suggest that there may be a modest association of GSTM1 null with lung cancer ( 220,231,232 ). A recent study ( 233 ) indicates a higher risk for lung cancer in females than in males with GSTM1 null. GSTP1-1 and GSTA1-1 also are important catalysts of glutathione conjugation of BPDE (Fig. 4 ) and other PAH diol epoxides ( 87 ). Moreover, the content of GSTP1 in the human lung significantly exceeds that of GSTM1 ( 85 ). These facts indicate that detoxification of PAH diol epoxides is a complex process, which is unlikely to be controlled by the absence or presence of a single gene product.

In summary, the hypothesis that lung cancer risk depends in part on carcinogen activation and detoxification is attractive, but it cannot be adequately tested by single genotyping approaches. Carcinogen metabolism is simply too complex (Fig. 4 ). Some studies ( 220 , 234 ) have also examined multiple genotypes, and several have found increased risk associated with variants of CYP1A1 in combination with GSTM1 null genotype. Further studies of this type are required and will be aided by the emerging DNA microarray technology, which will allow rapid, multiple genotyping. Carcinogen metabolite phenotyping, which would give a composite view of activation and detoxification reactions in humans, is likely to be an even more useful approach, although potentially more technically demanding than genotyping.

Another approach for assessing individual susceptibility to carcinogenic agents is the mutagen sensitivity assay, in which the frequency of in vitro bleomycin-induced chromatid breaks is quantified [reviewed in ( 177 , 235 )]. In a case-control study, mutagen sensitivity was significantly associated with lung cancer risk. This methodology has been extended, using BPDE for induction of chromosomal aberrations in human lymphocytes. Mutagen sensitivity was found to be greater in lung cancer case patients than in control subjects ( 177 ). In other studies [reviewed in ( 177 )], reduced DNA repair capacity was associated with increased lung cancer risk. The results of these studies are generally consistent with the scheme shown in Fig. 1 , although they lack specificity with respect to the particular carcinogens or enzymes involved.

E valuation of the R oles of S pecific C arcinogens in H uman L ung C ancer I nduced by C igarette S moke

Table 3 summarizes the data discussed above and estimates the role of various groups of carcinogens found in cigarette smoke as contributors to human lung cancer. The criteria used for evaluation are the presence of the compounds in cigarette smoke; their pulmonary carcinogenicity in laboratory animals; their human uptake, metabolism, and adduct formation; and their possible role in causing molecular changes in oncogenes or suppressor genes. The evaluation focuses on data for specific compounds and uses a weight-of-the-evidence approach.

The strongest evidence is for PAHs and NNK. There is no question that these compounds are present in mainstream and sidestream smoke of both nonfilter and filter cigarettes; extensive studies on their concentrations have been reported ( 38,65-67 ). There is also no doubt that NNK and some PAHs are very effective pulmonary carcinogens in rodents. Their uptake by smokers has been clearly demonstrated. Human liver metabolizes PAHs and NNK; one study ( 100 ) demonstrated that the relative rates of oxidative metabolism to electrophiles or their precursors were NNK>BaP>NNAL. Human lung metabolically activates BaP, in part by P4501A1, which is induced by cigarette smoking. Human lung converts NNK to NNAL; however, the activation of NNK in this tissue occurs less extensively than in rodent lung ( 22 ). Human bronchial epithelial cells are transformed by NNK ( 236 ). BPDE-DNA adducts have been detected in human lung, as have methyl and pyridyloxobutyl adducts, but these adduct studies are limited to date. Mutations in the p53 and KRAS genes could be caused by activated metabolites of PAHs, NNK, and many other carcinogens. Collectively, these data provide strong evidence for a role of PAHs and NNK as causes of lung cancer in smokers according to the overall mechanism outlined in Fig. 1 , although there are some important gaps. The relative roles of BaP and NNK have been discussed previously ( 22 ). On the basis of decreases in concentrations of BaP and increases in levels of NNK in cigarette smoke as well as on biologic and pharmacokinetic considerations, it is plausible that NNK is partially responsible for the dramatic increase in adenocarcinoma of the lung, which has now surpassed squamous cell carcinoma as the leading type of lung cancer in the United States; other factors, such as changes in puff volume and genetic influences, have been discussed elsewhere ( 22,230,237,238 ).

Studies on aza-arenes are quite limited. Two aza-arene pulmonary carcinogens listed in Table 1 , B , occur in extremely small quantities in cigarette smoke, and nothing is known about their disposition and metabolism in human systems. Metals are clearly present in cigarette smoke, and some are potent pulmonary carcinogens. But the role of these compounds is clouded by our limited knowledge of their valence state in cigarette smoke or after inhalation. Among miscellaneous organic compounds, the concentrations of 1,3-butadiene and aldehydes, such as formaldehyde and acetaldehyde, in cigarette smoke are substantial ( 38 ), but their role as pulmonary carcinogens is not clear. There is little doubt that cigarette smoke can cause oxidative damage, and it contains substantial quantities of free radicals such as nitric oxide; other radical species seem to be present but are poorly characterized. There is presently no evidence that the oxidative damage caused by cigarette smoke is specifically implicated in lung cancer. The lack of a protective effect against lung cancer of β-carotene, an antioxidant, in three human chemoprevention trials ( 239 - 241 ) and the lack of a protective effect of α-tocophenol in one of them ( 241 ) may indicate that oxidative damage is unimportant as a cause of cigarette smoke-induced lung cancer, although other explanations for the failure of these trials are plausible.

C onclusions

The complexity of tobacco smoke causes confusion in the literature about the mechanisms by which it induces lung cancer. Some authors oversimplify by referring to this complex mixture as “tar” or by attempting to implicate only one substance—such as BPDE—in cancer causation, while others maintain that the level of complexity is such that the mechanism is unknown. The reality lies between these extremes. A theme of this review is that mechanistic insight can be gained by focusing on specific pulmonary carcinogens in cigarette smoke.

Cigarette smoke carcinogens form the link between nicotine addiction and lung cancer (Fig. 1 ). Collectively, the evidence favoring the sequence of steps illustrated in Fig. 1 is extremely strong, although there are important aspects of each step that require further study. These include carcinogen metabolism and DNA binding in human lung, the effects of cigarette smoke on DNA repair and adduct persistence, the relationship between specific carcinogens and mutations in critical genes, and the sequence of gene changes leading to lung cancer.

Although there are at least 55 carcinogens in cigarette smoke (Table 1 , A ), presently available data allow us to focus on 20 substances that are probably involved in lung cancer induction because of their presence in cigarette smoke and their pulmonary carcinogenicity in laboratory animals (Table 1 , B ). By use of a weight-of-the-evidence approach, specific PAHs and the tobacco-specific nitrosamine NNK can be identified as probable causes of lung cancer in smokers, but the contribution of other agents cannot be excluded (Table 3 ). The long-term exposure of smokers to the genotoxic intermediates formed from these carcinogens is consistent with our present understanding of cancer induction as a process which requires multiple genetic changes. Thus, it is completely plausible that the continual barrage of DNA damage produced by tobacco smoke carcinogens causes the multiple genetic changes that are associated with lung cancer. While each dose of carcinogen from a cigarette is extremely small, the cumulative damage produced in years of smoking will be substantial.

Aspects of the scheme illustrated in Fig. 1 are well understood for PAHs and NNK. A great deal is known about the metabolic activation and detoxification of these compounds, although there are still parts of these complex pathways (Fig. 4 ) that require clarification. There is a good general understanding of the mechanisms by which these tobacco smoke carcinogens interact with DNA to form adducts, and considerable information is available about the repair, persistence, and miscoding properties of these adducts. There are many aspects of these processes that require further study, however. In particular, little is known about the levels, persistence, and repair of specific carcinogen DNA adducts in the lungs of smokers or the effects of chronic smoking on these factors. The location of carcinogen adducts at specific sites in human DNA has not been studied, mainly because of limitations in sensitivity. Nevertheless, one can reasonably conclude that metabolically activated tobacco smoke carcinogens directly cause mutations observed in tumor suppressor genes and oncogenes, although details remain elusive since numerous DNA-damaging agents in tobacco smoke cause similar mutations.

Many molecular epidemiologic studies attempting to identify gene-carcinogen interactions and other mechanistic aspects of the lung cancer process have focused on smokers. It is very important to elucidate those factors that determine which smokers will be susceptible to lung cancer development and to find natural protective mechanisms. Although the results to date are of great interest, these studies have not yet reached their full potential. Most have focused on individual genotypes which may be expected to affect particular reactions involved in metabolic activation or detoxification. Some of this research has been driven by the availability of relatively simple genotyping techniques. As this field evolves, it is becoming increasingly clear that this approach will yield only limited information. A more comprehensive integration of genotype and phenotype biomarkers into epidemiologic studies is required. This will be enhanced by the rapidly developing DNA microarray technology (DNA chips) that will allow rapid multiple genotyping. Ultimately, it should also be possible to monitor the metabolic pathways illustrated in Fig. 1 in smokers and in other people exposed to tobacco carcinogens by a combined genotyping-phenotyping approach. This would lead to methods for identification of susceptible individuals and early detection of lung cancer.

Blocking any of the horizontal pathways in Fig. 1 should lead to reduced lung cancer incidence and mortality. Preventing nicotine addiction and improving smoking cessation strategies are clearly priorities, but these are only partially successful ( 242 - 244 ). An important approach for addicted smokers and ex-smokers is chemoprevention. Many agents that can block carcinogen activation or enhance detoxification are now known ( 245 ). Other chemopreventive compounds inhibit events downstream from DNA adduct formation ( 246 - 249 ). The further development of effective chemopreventive agents should be a major priority for reducing lung cancer incidence.

Table 1, A.

Summary of carcinogens in cigarette smoke *

Table 1, B. Pulmonary carcinogens in cigarette smoke

Table 1, A. Summary of carcinogens in cigarette smoke *
 
Type
 
No. of compounds
 
Polycyclic aromatic hydrocarbons 10 
Aza-arenes 
N -Nitrosamines  
Aromatic amines 
Heterocyclic aromatic amines 
Aldehydes 
Miscellaneous organic compounds 15 
Inorganic compounds 
  Total 55 
Table 1, A. Summary of carcinogens in cigarette smoke *
 
Type
 
No. of compounds
 
Polycyclic aromatic hydrocarbons 10 
Aza-arenes 
N -Nitrosamines  
Aromatic amines 
Heterocyclic aromatic amines 
Aldehydes 
Miscellaneous organic compounds 15 
Inorganic compounds 
  Total 55 
Table 1, B. Pulmonary carcinogens in cigarette smoke
 
Carcinogen class
 
Compound
 
Amount in mainstream cigarette smoke, ng/cigarette
 
Sidestream/ mainstream ratio §
 
Representative lung tumorigenicity in species
 
Reference No.
 
Polycyclic aromatic hydrocarbons  Benzo[ a ]pyrene  20-40 2.5-3.5 Mouse, rat, hamster  ( 41 , 42 )  
  Benzo[ b ]fluoranthane  4-22  Rat  ( 41 - 43 )  
  Benzo[ j ]fluoranthane  6-21  Rat  ( 41 - 43 )  
  Benzo[ k ]fluoranthane  6-12  Rat  ( 41 - 43 )  
  Dibenzo[ a,i ]pyrene  1.7-3.2  Hamster  ( 41,42,44 )  
  Indeno[1,2,3- cd ]pyrene  4-20  Rat  ( 41 - 43 )  
  Dibenz[ a,h ]anthracene   Mouse  ( 41,42,45 )  
 5-Methylchrysene 0.6  Mouse  ( 42 , 45 )  
Asz-arenes  Dibenz[ a,h ]acridine  0.1  Rat  ( 41,42,46 )  
  7H-Dibenzo[ c,g ]carbazole  0.7  Hamster  ( 41,42,47 )  
N -Nitrosamines  N -Nitrosodiethylamine  ND-2.8 <40 Hamster  ( 48 , 49 )  
 4-(Methylnitrosamino)-1- (3-pyridyl)-1-butanone (NNK) 80-770 1-4 Mouse, rat, hamster  ( 22 , 50 )  
Miscellaneous organic compounds 1,3-Butadiene  20-70 × 10 3  Mouse  ( 51 )  
 Ethyl carbamate 20-38  Mouse  ( 52 )  
Inorganic compounds Nickel 0-510 13-30 Rat  ( 53 )  
 Chromium 0.2-500  Rat  ( 53 )  
 Cadmium 0-6670 7.2 Rat  ( 54 )  
 Polonium-210 0.03-1.0 pCi 1.0-4.0 Hamster  ( 55 - 58 )  
 Arsenic 0-1400   None   ( 59 )  
 Hydrazine 24-43  Mouse  ( 60 )  
Table 1, B. Pulmonary carcinogens in cigarette smoke
 
Carcinogen class
 
Compound
 
Amount in mainstream cigarette smoke, ng/cigarette
 
Sidestream/ mainstream ratio §
 
Representative lung tumorigenicity in species
 
Reference No.
 
Polycyclic aromatic hydrocarbons  Benzo[ a ]pyrene  20-40 2.5-3.5 Mouse, rat, hamster  ( 41 , 42 )  
  Benzo[ b ]fluoranthane  4-22  Rat  ( 41 - 43 )  
  Benzo[ j ]fluoranthane  6-21  Rat  ( 41 - 43 )  
  Benzo[ k ]fluoranthane  6-12  Rat  ( 41 - 43 )  
  Dibenzo[ a,i ]pyrene  1.7-3.2  Hamster  ( 41,42,44 )  
  Indeno[1,2,3- cd ]pyrene  4-20  Rat  ( 41 - 43 )  
  Dibenz[ a,h ]anthracene   Mouse  ( 41,42,45 )  
 5-Methylchrysene 0.6  Mouse  ( 42 , 45 )  
Asz-arenes  Dibenz[ a,h ]acridine  0.1  Rat  ( 41,42,46 )  
  7H-Dibenzo[ c,g ]carbazole  0.7  Hamster  ( 41,42,47 )  
N -Nitrosamines  N -Nitrosodiethylamine  ND-2.8 <40 Hamster  ( 48 , 49 )  
 4-(Methylnitrosamino)-1- (3-pyridyl)-1-butanone (NNK) 80-770 1-4 Mouse, rat, hamster  ( 22 , 50 )  
Miscellaneous organic compounds 1,3-Butadiene  20-70 × 10 3  Mouse  ( 51 )  
 Ethyl carbamate 20-38  Mouse  ( 52 )  
Inorganic compounds Nickel 0-510 13-30 Rat  ( 53 )  
 Chromium 0.2-500  Rat  ( 53 )  
 Cadmium 0-6670 7.2 Rat  ( 54 )  
 Polonium-210 0.03-1.0 pCi 1.0-4.0 Hamster  ( 55 - 58 )  
 Arsenic 0-1400   None   ( 59 )  
 Hydrazine 24-43  Mouse  ( 60 )  
*

Adapted from ( 19 , 20 ) . Compounds for which there is “ sufficient evidence for carcinogenicity” in either laboratory animals or humans, according to evaluations by the International Agency for Research on Cancer.

Data from ( 19 , 37 ) ; all values in ng/cigarette except polonium-210; ND = not detectable.

§

Data from ( 61 ) .

Studies in laboratory animals.

Epidemiologic studies indicate that inorganic arsenic compounds are skin or lung carcinogens in humans.

Table 2.

Induction of lung tumors by NNK [ 4-(methylnitrosamino)-1-[3-pyridyl)-1-butanone] *

Species and strain
 
Route
 
Mouse 
 A/J i.p. gavage, p.o. 
 Sencar Skin 
 BALB/c Oral 
 Swiss Oral, i.p. 
 C3B6F 1 i.p. 
 C3H/HeJ i.p. 
 C57BL/6 i.p. 
 (A/J × TSG-p53) F 2 i.p. 
F344 rat s.c., p.o., oral swab, gavage, intravesicular 
Syrian golden hamster s.c., application to cheek pouch 
Mink s.c. 
Species and strain
 
Route
 
Mouse 
 A/J i.p. gavage, p.o. 
 Sencar Skin 
 BALB/c Oral 
 Swiss Oral, i.p. 
 C3B6F 1 i.p. 
 C3H/HeJ i.p. 
 C57BL/6 i.p. 
 (A/J × TSG-p53) F 2 i.p. 
F344 rat s.c., p.o., oral swab, gavage, intravesicular 
Syrian golden hamster s.c., application to cheek pouch 
Mink s.c. 
*

Adapted from ( 22 ) .

i.p. = intraperitoneal; p.o. = per os (i.e., orally via drinking water); and s.c. = subcutaneous.

Table 3.

Evaluation of roles of specific carcinogens in human lung cancer induced by cigarette smoke

  Evaluation of evidence for a role in lung cancer *
 
Compound(s)
 
Presence in cigarette smoke
 
Pulmonary carcinogenicity in rodents
 
Human uptake
 
Human metabolism and adduct formation
 
Molecular changes in human genes
 
Overall score
 
Specific PAHs  18 
Aza-arenes 10 
NNK, N -nitrosodiethylamine  18 
Metals § 11 
Miscellaneous organic compounds  10 
Free radicals/oxidative damage 11 
  Evaluation of evidence for a role in lung cancer *
 
Compound(s)
 
Presence in cigarette smoke
 
Pulmonary carcinogenicity in rodents
 
Human uptake
 
Human metabolism and adduct formation
 
Molecular changes in human genes
 
Overall score
 
Specific PAHs  18 
Aza-arenes 10 
NNK, N -nitrosodiethylamine  18 
Metals § 11 
Miscellaneous organic compounds  10 
Free radicals/oxidative damage 11 
*

Scores: 1 = Inadequate data; 2 = weak or equivocal evidence; 3 = some evidence; limited studies; and 4 = clear evidence; strong, reproducible studies.

Polycyclic aromatic hydrocarbons (PAHs) including benzo[ a ]pyrene, benzofluoranthenes, dibenzo[ a,i ]pyrene, dibenz[ a,h ]anthracene, and 5-methylchrysene. Does not include studies of “PAH-DNA adducts” or “hydrophobic DNA adducts” as determined by immunoassay and 32 P-postlabeling ( see text).

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone.

§

Nickel, chromium, cadmium, polonium-210, and arsenic.

Including 1,3-butadiene, ethyl carbamate, and aldehydes.

Fig. 1.

Scheme linking nicotine addiction and lung cancer via tobacco smoke carcinogens and their induction of multiple mutations in critical genes. PAH = polycyclic aromatic hydrocarbons; NNK = 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

Fig. 1.

Scheme linking nicotine addiction and lung cancer via tobacco smoke carcinogens and their induction of multiple mutations in critical genes. PAH = polycyclic aromatic hydrocarbons; NNK = 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

Fig. 2.

Structures of organic pulmonary carcinogens in tobacco smoke.

Fig. 2.

Structures of organic pulmonary carcinogens in tobacco smoke.

Fig. 3.

Relationship between dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and lung tumor incidence in male F344 rats. Data were combined from protocols using subcutaneous (s.c.) injection, three times weekly for 20 weeks, in studies carried out by investigators at the National Institute of Environmental Health Sciences (□) or the American Health Foundation (○), or by administration in the drinking water (•) (American Health Foundation). Upper x -axis, single s.c. dose refers to the magnitude of one of the 60 doses used. Each symbol represents a group of 20-80 rats. From ( 22 ) .

Fig. 3.

Relationship between dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and lung tumor incidence in male F344 rats. Data were combined from protocols using subcutaneous (s.c.) injection, three times weekly for 20 weeks, in studies carried out by investigators at the National Institute of Environmental Health Sciences (□) or the American Health Foundation (○), or by administration in the drinking water (•) (American Health Foundation). Upper x -axis, single s.c. dose refers to the magnitude of one of the 60 doses used. Each symbol represents a group of 20-80 rats. From ( 22 ) .

Fig. 4.

Metabolic pathways of benzo[ a ]pyrene (BaP) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), modified from ( 22,80,83 ). Some human enzymes involved in the various reactions are indicated ( 79 - 100 ). EH = epoxide hydrolase; DHD = dihydrodiol dehydrogenase; UGT = UDP-glucuronosyl transferase; GST = glutathione S -transferase; P450 = cytochrome P450; NNAL = 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol; 1-OH, 3-OH = 1-hydroxy BaP, 3-hydroxy BaP, etc. Other abbreviations are defined in the text.

Fig. 4.

Metabolic pathways of benzo[ a ]pyrene (BaP) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), modified from ( 22,80,83 ). Some human enzymes involved in the various reactions are indicated ( 79 - 100 ). EH = epoxide hydrolase; DHD = dihydrodiol dehydrogenase; UGT = UDP-glucuronosyl transferase; GST = glutathione S -transferase; P450 = cytochrome P450; NNAL = 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol; 1-OH, 3-OH = 1-hydroxy BaP, 3-hydroxy BaP, etc. Other abbreviations are defined in the text.

Fig. 5.

Correlation between cotinine plus cotinine- N -glucuronide (cotinine-Gluc) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) plus its glucuronide (NNAL-Gluc) in smokers' urine ( r = .68, two-sided P <.01). Unpublished observations from S. G. Carmella and S. S. Hecht for 223 smokers from whom cotinine and cotinine- N -glucuronide were determined by gas chromatography-mass spectrometry, and NNAL and NNAL-Gluc were determined by gas chromatography-nitrosamine selective detection.

Fig. 5.

Correlation between cotinine plus cotinine- N -glucuronide (cotinine-Gluc) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) plus its glucuronide (NNAL-Gluc) in smokers' urine ( r = .68, two-sided P <.01). Unpublished observations from S. G. Carmella and S. S. Hecht for 223 smokers from whom cotinine and cotinine- N -glucuronide were determined by gas chromatography-mass spectrometry, and NNAL and NNAL-Gluc were determined by gas chromatography-nitrosamine selective detection.

Supported by Public Health Service grants CA44377, CA46535, and CA81301 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services.

I thank Chap Le for his help with the statistical analyses of data in Fig. 3 and Steven Carmella for compiling the data in Fig. 5 .

References

(1)
Landis SH, Murray T, Bolden S, Wingo PA. Cancer statistics, 1999.
CA Cancer J Clin;
 
1999
;
49
:
8
-31.
(2)
World Cancer Research Fund/American Institute for Cancer Research. Food, nutrition and the prevention of cancer: a global perspective. Washington (DC): American Instiute for Cancer Research; 1997. p. 37
(3)
Blot WJ, Fraumeni JF Jr. Cancers of the lung and pleura. In: Schottenfeld, D, Fraumeni J Jr, editors. Cancer Epidemiology and Prevention. New York (NY): Oxford University Press; 1996. p. 637-65.
(4)
Surgeon General. Reducing the health consequences of smoking: 25 years of progress. Washington (DC): U.S. Gov Print Off; 1989.
(5)
Shopland DR. Tobacco use and its contribution to early cancer mortality with a special emphasis on cigarette smoking.
Environ Health Perspect
 
1995
;
103 Suppl 8
:
131
-42.
(6)
Anonymous. Cigarette smoking among adults—United States 1995.
Morb Mortal Wkly Rep
 
1995
;
46
:
1217
-20.
(7)
Surgeon General. Smoking and health. Report of the Advisory Committee to the Surgeon General of the Public Health Service. Washington (DC): U.S. Gov Print Off; 1964.
(8)
American Cancer Society. Cancer Facts and Figures—1996. Atlanta (GA): American Cancer Society; 1996. p. 24.
(9)
National Cancer Institute. Changes in cigarette-related disease risks and their implication for prevention and control. In: Smoking and Tobacco Control Monograph 8. Bethesda (MD): National Institutes of Health Publ No. 97-4213; 1996. p. 13-112.
(10)
Wald NJ, Hackshaw AK. Cigarette smoking: an epidemiological overview.
Br Med Bull
 
1996
;
52
:
3
-11.
(11)
Peto R, Lopez AD, Boreham J, Thun M, Heath C Jr, Doll R. Mortality from smoking worldwide.
Br Med Bull
 
1996
;
52
:
12
-21.
(12)
Environmental Health Hazard Assessment, California Environmental Protection Agency. Health effects of exposure to environmental tobacco smoke. Sacramento (CA): California Environmental Protection Agency; 1997.
(13)
Dockery DW, Trichopoulos D. Risk of lung cancer from environmental exposures to tobacco smoke.
Cancer Causes Control
 
1997
;
8
:
333
-45.
(14)
Environmental Protection Agency (EPA). Respiratory health effects of passive smoking: lung cancer and other disorders. Report No. EPA/600/6-90/006F. Office of Health and Environmental Assessment, Office of Research and Development. Washington (DC): EPA; 1992.
(15)
United States Department of Health and Human Services. The health consequences of involuntary smoking: a report of the Surgeon General. Washington (DC): Department of Health and Human Services; 1986.
(16)
Boffetta P, Agudo A, Ahrens W, Benhamou E, Benhamou S, Darby SC, et al. Multicenter case-control study of exposure to environmental tobacco smoke and lung cancer in Europe.
J Natl Cancer Inst
 
1998
;
90
:
1440
-50.
(17)
Ames BN, Gold LS, Willett WC. The causes and prevention of cancer.
Proc Natl Acad Sci U S A
 
1995
;
92
:
5258
-65.
(18)
Surgeon General. The health consequences of smoking: nicotine addiction. Washington (DC): U.S. Gov Print; 1988.
(19)
Hoffmann D, Hoffmann I. The changing cigarette, 1950-1995.
J Toxicol Environ Health
 
1997
;
50
:
307
-64.
(20)
Hoffmann D, Hecht SS. Advances in tobacco carcinogenesis. In: Cooper CS, Grover PL, editors. Handbook of experimental pharmacology. Vol 94/I. Heidelberg (Germany): Springer-Verlag; 1990. p. 63-102.
(21)
Hecht SS. Cigarette smoking and cancer. In: Rom WN, editor. Environmental and occupational medicine. New York (NY): Lippincott-Raven; 1998. p. 1479-99.
(22)
Hecht SS. Biochemistry, biology, and carcinogenicity of tobacco-specific N- nitrosamines.
Chem Res Toxicol
 
1998
;
11
:
559
-603.
(23)
Conney AH. Induction of microsomal enzymes by foreign chemicals and carcinogenesis by polycyclic aromatic hydrocarbons: G. H. A. Clowes Memorial Lecture.
Cancer Res
 
1982
;
42
:
4875
-917.
(24)
Miller JA. Research in chemical carcinogenesis with Elizabeth Miller—a trail of discovery with our associates.
Drug Metab Dispos
 
1994
;
26
:
1
-36.
(25)
Miller EC, Miller JA. Searches for the ultimate chemical carcinogens and their reactions with cellular macromolecules.
Cancer
 
1981
;
47
:
2327
-45.
(26)
Hemminki K, Dipple A, Shuker DEG, Kadlubar FF, Segerback D, Bartsch H. DNA adducts: identification and biological significance. IARC Sci Publ No. 125. Lyon (France): IARC; 1994.
(27)
Geacintov NE, Cosman M, Hingerty BE, Amin S, Broyde S, Patel DJ. NMR solution structures of stereoisomeric covalent polycyclic aromatic carcinogen-DNA adducts: principles, patterns, and diversity.
Chem Res Toxicol
 
1997
;
10
:
111
-46.
(28)
Singer B, Essigmann JM. Site-specific mutagenesis: retrospective and prospective.
Carcinogenesis
 
1991
;
12
:
949
-55.
(29)
Wistuba II, Lam S, Behrens C, Virmani AK, Fong KM, LeRiche J, et al. Molecular damage in the bronchial epithelium of current and former smokers.
J Natl Cancer Inst
 
1997
;
89
:
1366
-73.
(30)
Sekido Y, Fong KM, Minna JD. Progress in understanding the molecular pathogenesis of human lung cancer.
Biochim Biophys Acta
 
1998
;
1378
:
F21
-59.
(31)
Mills NE, Fishman CL, Rom WN, Dubin N, Jacobson DR. Increased prevalence of K-ras oncogene mutations in lung adenocarcinoma.
Cancer Res
 
1995
;
55
:
1444
-7.
(32)
Westra WH, Baas IO, Hruban RH, Askin FB, Wilson K, Offerhaus GJ, et al. K-ras oncogene activation in atypical alveolar hyperplasias of the human lung.
Cancer Res
 
1996
;
56
:
2224
-8.
(33)
Westra WH, Slebos RJ, Offerhaus GJ, Goodman SN, Evers SG, Kensler TW, et al. K-ras oncogene activation in lung adenocarcinomas from former smokers. Evidence that K-ras mutations are an early and irreversible event in the development of adenocarcinoma of the lung.
Cancer
 
1993
;
72
:
432
-8.
(34)
Greenblatt MS, Bennett WP, Hollstein M, Harris CC. Mutations in the p53 tumor suppressor gene: clues to cancer etiology and molecular pathogenesis.
Cancer Res
 
1994
;
54
:
4855
-78.
(35)
Hussain SP, Harris CC. Molecular epidemiology of human cancer: contribution of mutation spectra studies of tumor suppressor genes.
Cancer Res
 
1998
;
85
:
4023
-37.
(36)
Olshan AF, Weissler MC, Pei H, Conway K. p53 mutations in head and neck cancer: new data and evaluation of mutational spectra.
Cancer Epidemiol Biomarkers Prev
 
1997
;
6
:
499
-504.
(37)
Smith TJ, Livingston SD, Doolittle OJ. An international literature survey of “IARC group I carcinogens” reported in mainstream cigarette smoke.
Food Chem Toxicol
 
1997
;
35
:
1107
-30.
(38)
International Agency for Research on Cancer (IARC). Tobacco smoking. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 38. Lyon (France): IARC; 1986. p. 37-375.
(39)
Snook ME, Severson RF, Arrendale RF, Higman HC, Chortyk OT. Multi-alkylated polynuclear aromatic hydrocarbons of tobacco smoke: separation and identification.
Beitr Tabakforsch
 
1978
;
9
:
222
-47.
(40)
Snook ME, Severson RF, Arrendale RF, Higman HC, Chortyk OT. The identification of high molecular weight polynuclear aromatic hydrocarbons in a biologically active fraction of cigarette smoke condensate.
Beitr Tabakforsch
 
1977
;
9
:
79
-101.
(41)
International Agency for Research on Cancer (IARC). Certain polycyclic aromatic hydrocarbons and heterocyclic compounds. IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man. Vol 3. Lyon (France): IARC; 1972. p. 45-268.
(42)
International Agency for Research on Cancer (IARC). Polynuclear aromatic compounds, part 1, chemical, environmental, and experimental data. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 32. Lyon (France): IARC; 1983. p. 33-451.
(43)
Deutsch-Wenzel RP, Brune H, Grimmer G, Dettbarn G, Misfeld J. Experimental studies in rat lungs on the carcinogenicity and dose-response relationships of eight frequently occurring environmental polycyclic aromatic hydrocarbons.
J Natl Cancer Inst
 
1983
;
71
:
539
-44.
(44)
Sellakumar A, Shubik P. Carcinogenicity of different polycyclic hydrocarbons in the respiratory tract of hamsters.
J Natl Cancer Inst
 
1974
;
53
:
1713
-9.
(45)
Nesnow S, Ross JA, Stoner GD, Mass MJ. Mechanistic linkage between DNA adducts, mutations in oncogenes and tumorigenesis of carcinogenic environmental polycyclic aromatic hydrocarbons in strain A/J mice.
Toxicology
 
1995
;
105
:
403
-13.
(46)
Deutsch-Wenzel RP, Brune H, Grimmer G. Experimental studies on the carcinogenicity of five nitrogen containing polycyclic aromatic compounds directly injected into rat lungs.
Cancer Lett
 
1983
;
20
:
97
-101.
(47)
Sellakumar A, Starback F, Rowland J, Shubik P. Tumor induction by 7H-dibenzo[ c,g ]carbazole in the respiratory tract of Syrian hamsters.
J Toxicol Environ Health
 
1977
;
3
:
935
-9.
(48)
International Agency for Research on Cancer (IARC). Some N -nitroso Compounds. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 17. Lyon (France): IARC; 1983. p. 83-124.
(49)
Reznik-Shuller HM. Cancer induced in the respiratory tract of rodents by N- nitroso compounds. In: Reznik-Shuller HM, editor. Comparative respiratory tract carcinogens. Vol II. Boca Raton (FL): CRC Press, Inc.; 1983. p. 109-59.
(50)
International Agency for Research on Cancer (IARC). Tobacco habits other than smoking: betel quid and areca nut chewing, and some related nitrosamines. In: IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans. Vol 37. Lyon (France): IARC; 1983. p. 205-8.
(51)
International Agency for Research on Cancer (IARC). Occupational exposures to mists and vapours from strong inorganic acids; and some other industrial chemicals. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 54. Lyon (France): IARC; 1992. p. 237-85.
(52)
International Agency for Research on Cancer (IARC). Some antithyroid and related substances, nitrofurans and industrial chemicals. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Vol 7. Lyon (France): IARC; 1974. p. 111-40.
(53)
International Agency for Research on Cancer (IARC). Chromium, nickel and welding. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 49. Lyon (France): IARC; 1990. p. 49-245.
(54)
International Agency for Research on Cancer (IARC). Beryllium, cadmium, mercury, and exposures in the glass manufacturing industry. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 58. Lyon (France): IARC; 1993. p. 119-237.
(55)
International Agency for Research on Cancer (IARC). Man-made mineral fibers and radon. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 43. Lyon (France): IARC; 1988. p. 173-259.
(56)
Little JB, McGandy RB, Kennedy AR. Interactions between polonium-210 alpha-radiation, benzo( a )pyrene, and 0.9% NaCl solution instillations in the induction of experimental lung cancer.
Cancer Res
 
1978
;
38
:
1929
-35.
(57)
Little JB, O'Toole WF. Respiratory tract tumors in hamsters induced by benzo( a )pyrene and 210Po alpha-radiation.
Cancer Res
 
1974
;
34
:
3026
-39.
(58)
Yuile CL, Berke HL, Hull T. Lung cancer following polonium-210 inhalation in rats.
Rad Res
 
1967
;
31
:
760
-3.
(59)
International Agency for Research on Cancer (IARC). Some metals and metallic compounds. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Vol 23. Lyon (France): IARC; 1980. p. 39-141.
(60)
International Agency for Research on Cancer (IARC). Some aromatic amines, hydrazine and related substances, N -nitroso compounds and miscellaneous alkylating agents. In: IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Vol 4. Lyon (France): IARC; 1973. p.127-36.
(61)
Guerin MR, Jenkins RA, Tomkins BA. the chemistry of environmental tobacco smoke: composition and management. Chelsea (MA): Lewis Publishers; 1992.
(62)
Thyssen J, Althoff J, Kimmerle G, Mohr U. Inhalation studies with benzo[ a ]pyrene in Syrian golden hamsters.
J Natl Cancer Inst
 
1981
;
66
:
575
-7.
(63)
Wolterbeek AP, Schoevers EJ, Rutten AA, Feron VJ. A critical appraisal of intratracheal instillation of benzo[ a ]pyrene to Syrian golden hamsters as a model in respiratory tract carcinogenesis.
Cancer Lett
 
1995
;
89
:
107
-16.
(64)
Culp SJ, Gaylor DW, Sheldon WG, Goldstein LS, Beland FA. A comparison of the tumors induced by coal tar and benzo[ a ]pyrene in a 2-year bioassay.
Carcinogenesis
 
1998
;
19
:
117
-24.
(65)
Hecht SS, Hoffmann D. Tobacco-specific nitrosamines, an important group of carcinogens in tobacco and tobacco smoke.
Carcinogenesis
 
1988
;
9
:
875
-84.
(66)
Hoffmann D, Brunnemann KD, Prokopczyk B, Djordjevic MV. Tobacco-specific N- nitrosamines and Areca -derived N -nitrosamines: chemistry, biochemistry, carcinogenicity, and relevance to humans.
J Toxicol Environ Health
 
1994
;
41
:
1
-52.
(67)
Spiegelhalder B, Bartsch H. Tobacco-specific nitrosamines.
Eur J Cancer Prev
 
1996
;
5 Suppl 1
:
33
-8.
(68)
Harley NB, Cohen BS, Tso TC. Polonium-210: a questionable risk factor in smoking related carcinogenesis. Banbury Report 3: a safe cigarette? Cold Spring Harbor (NY): Cold Spring Harbor Laboratory; 1980. p. 93-104.
(69)
Blot WJ, McLaughlin JK. Passive smoking and lung cancer risk: what is the story now? [editorial].
J Natl Cancer Inst
 
1998
;
90
:
1416
-7.
(70)
Hecht SS. Carcinogenic effects of cigarette smoke on the respiratory tract. In: Roth RA, editor. Comprehensive toxicology: toxicology of the respiratory system. Vol 8. Oxford (U.K.): Elsevier Science; 1997. p. 437-51.
(71)
Henry CJ, Kouri RE. Chronic inhalation studies in mice. II. Effects of long-term exposure to 2R1 cigarette smoke on (C57BL/Cum × C3H/AnfCum)F 1 mice.
J Natl Cancer Inst
 
1986
;
77
:
203
-12.
(72)
Finch GL, Nikula KJ, Belinsky SA, Barr EB, Stoner GD, Lechner JF. Failure of cigarette smoke to induce or promote lung cancer in the A/J mouse.
Cancer Lett
 
1996
;
99
:
161
-7.
(73)
Witschi H, Espiritu I, Peake JL, Wu K, Maronpot RR, Pinkerton KE. The carcinogenicity of environmental tobacco smoke.
Carcinogenesis
 
1997
;
18
:
575
-86.
(74)
Witschi H, Espiritu I, Maronpot RR, Pinkerton KE, Jones AD. The carcinogenic potential of the gas phase of environmental tobacco smoke.
Carcinogenesis
 
1997
;
18
:
2035
-42.
(75)
Guengerich FP. Cytochrome P450 enzymes. In: Guengerich FP, editor. Comprehensive toxicology: biotransformation. Vol 3. Oxford (U.K.): Elsevier Science; 1997. p. 37-68.
(76)
Armstrong RN. Glutathione- S -transferases. In: Guengerich FP, editor. Comprehensive toxicology: biotransformation. Vol 3. Oxford (U.K.): Elsevier Science; 1997. p. 307-27.
(77)
Burchell B, McGurk K, Brierley CH, Clarke DJ. UDP-glucuronosyltransferases. In: Guengerich FP, editor. Comprehensive toxicology: biotransformation. Vol 3. Oxford (U.K.): Elsevier Science; 1997. p. 401-36.
(78)
Duffel MW. Sulfotransferases. In: Guengerich FP, editor. Comprehensive toxicology: biotransformation. Vol 3. Oxford (U.K.): Elsevier Science; 1997. p. 365-84.
(79)
Gelboin HV. Benzo[ a ]pyrene metabolism, activation and carcinogenesis: role and regulation of mixed-function oxides and related enzymes.
Physiol Rev
 
1980
;
60
:
1107
-66.
(80)
Cooper CS, Grover PL, Sims P. The metabolism and activation of benzo[ a ]pyrene. In: Bridges JW, Chasseaud LF, editors. Progress in drug metabolism. New York (NY): John Wiley & Sons; 1983. p. 295-396.
(81)
Pelkonen O, Nebert DW. Metabolism of polycyclic hydrocarbons: etiologic role in carcinogenesis.
Pharmacol Rev
 
1982
;
34
:
189
-222.
(82)
Conney AH, Chang RL, Jerina DM, Wei SJ. Studies on the metabolism of benzo[ a ]pyrene and dose-dependent differences in the mutagenic profile of its ultimate carcinogenic metabolite.
Drug Metab Rev
 
1994
;
26
:
125
-63.
(83)
Hecht SS. Carcinogenesis due to tobacco: molecular mechanisms. In: Bertino JR, editor. Encyclopedia of cancer. San Diego (CA): Academic Press; 1996. p. 220-32.
(84)
Baird WM, Ralston SL. Carcinogenic polycyclic aromatic hydrocarbons. In: Bowden GT, Fischer SM, editors. Comprehensive toxicology: chemical carcinogens and anticarcinogens. Vol 12. 1997. p. 171-200.
(85)
Ketterer B, Harris JM, Talaska G, Meyer DJ, Pemble SE, Taylor JB, et al. The human glutathione S -transferase supergene family, its polymorphism, and its effects on susceptibility to lung cancer.
Environ Health Perspect
 
1992
;
98
:
87
-94.
(86)
Jernstrom B, Funk M, Frank H, Mannervik B, Seidel A. Glutathione S -transferase A1-1-catalysed conjugation of bay and fjord region diol epoxides of polycyclic hydrocarbons with glutathione.
Carcinogenesis
 
1996
;
17
:
1491
-8.
(87)
Sundberg K, Widersten M, Seidel A, Mannervik B, Jernstrom B. Glutathione conjugation of bay- and fjord-region diol epoxides of polycyclic aromatic hydrocarbons by glutathione transferase M1-1 and P1-1.
Chem Res Toxicol
 
1997
;
10
:
1221
-7.
(88)
Yun CH, Shimada T, Guengerich FP. Roles of human liver cytochrome P4502C and 3A enzymes in the 3-hydroxylation of benzo[ a ]pyrene.
Cancer Res
 
1992
;
52
:
1868
-74.
(89)
Bauer E, Guo Z, Ueng YF, Bell LC, Zeldin D, Guengerich FP. Oxidation of benzo[ a ]pyrene by recombinant human cytochrome P450 enzymes.
Chem Res Toxicol
 
1995
;
8
:
136
-42.
(90)
Shou M, Korzekwa KR, Crespi CL, Gonzalez FJ, Gelboin HV. The role of 12 cDNA-expressed human, rodent, and rabbit cytochromes P450 in the metabolism of benzo[ a ]pyrene and benzo[ a ]pyrene trans -7,8-dihydrodiol.
Mol Carcinog
 
1994
;
10
:
159
-68.
(91)
Shimada T, Hayes CL, Yamazaki H, Amin S, Hecht SS, Guengerich FP, et al. Activation of chemically diverse procarcinogens by human cytochrome P-450 1B1.
Cancer Res
 
1996
;
56
:
2979
-84.
(92)
Kim JH, Stansbury KH, Walker NJ, Trush MA, Strickland PT, Sutter TR. Metabolism of benzo[ a ]pyrene and benzo[ a ]pyrene-7,8-diol by human cytochrome P450 1B1.
Carcinogenesis
 
1998
;
19
:
1847
-53.
(93)
Penning TM, Burczynski ME, Hung CF, McCoull KD, Palackal NT, Tsuruda LS. Dihydrodiol dehydrogenses and polycyclic aromatic hydrocarbon activation: generation of reactive and redox active O -quinones.
Chem Res Toxicol
 
1999
;
12
:
1
-18.
(94)
Friedberg T, Becker R, Oesch F, Glatt H. Studies on the importance of microsomal epoxide hydrolase in the detoxification of arene oxides using the heterologous expression of the enzyme in mammalian cells.
Carcinogenesis
 
1994
;
15
:
171
-5.
(95)
Smith TJ, Guo Z, Gonzalez FJ, Guengerich FP, Stoner GD, Yang CS. Metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in human lung and liver microsomes and cytochromes P-450 expressed in hepatoma cells.
Cancer Res
 
1992
;
52
:
1757
-63.
(96)
Yamazaki H, Inui Y, Yun CH, Guengerich FP, Shimada T. Cytochrome P450 2E1 and 2A6 enzymes as major catalysts for metabolic activation of N -nitrosodialkylamines and tobacco-related nitrosamines in human liver microsomes.
Carcinogenesis
 
1992
;
13
:
1789
-94.
(97)
Tiano HF, Hosokawa M, Chulada PC, Smith PB, Wang RL, Gonzalez FJ, et al. Retroviral mediated expression of human cytochrome P450 2A6 in C3H/10T1/2 cells confers transformability by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).
Carcinogenesis
 
1993
;
14
:
1421
-7.
(98)
Smith TJ, Stoner GD, Yang CS. Activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in human lung microsomes by cytochromes P450, lipoxygenase, and hydroperoxides.
Cancer Res
 
1995
;
55
:
5566
-73.
(99)
Patten CJ, Smith TJ, Murphy SE, Wang MH, Lee J, Tynes RE, et al. Kinetic analysis of the activation of 4-(methylnitrosamino)-1-(3-pyridy)-1-butanone by heterologously expressed human P450 enzymes and the effect of P450-specific chemical inhibitors on this activation in human liver microsomes.
Arch Biochem Biophys
 
1996
;
333
:
127
-8.
(100)
Staretz ME, Murphy SE, Patten CJ, Nunes MG, Koehl W, Amin S, et al. Comparative metabolism of the tobacco-related carcinogens benzo[ a ]pyrene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and N ′-nitrosonornicotine in human hepatic microsomes.
Drug Metab Dispos
 
1997
;
25
:
154
-62.
(101)
Benowitz NL. Cotinine as a biomarker of environmental tobacco smoke exposure.
Epidemiol Rev
 
1996
;
18
:
188
-204.
(102)
Carmella SG, Akerkar S, Hecht SS. Metabolites of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in smokers' urine.
Cancer Res
 
1993
;
53
:
721
-4.
(103)
Hecht SS, Carmella SG, Murphy SE, Akerkar S, Brunnemann KD, Hoffmann D. A tobacco-specific lung carcinogen in the urine of men exposed to cigarette smoke.
N Engl J Med
 
1993
;
329
:
1543
-6.
(104)
Carmella SG, Akerkar SA, Richie JP Jr, Hecht SS. Intraindividual and interindividual differences in metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in smokers' urine.
Cancer Epidemiol Biomarkers Prev
 
1995
;
4
:
635
-42.
(105)
Carmella SG, Borukhova A, Akerkar SA, Hecht SS. Analysis of human urine for pyridine- N -oxide metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, a tobacco-specific lung carcinogen.
Cancer Epidemiol Biomarkers Prev
 
1997
;
6
:
113
-20.
(106)
Meger M, Meger-Kossien I, Dietrich M, Tricker AR, Scherer G, Adlkofer F. Metabolites of 4-( N- methylnitrosamino)-1-(3-pyridyl)-1-butanone in the urine of smokers [published erratum appears in Eur J Cancer Prev 1997;6:99].
Eur J Cancer Prev
 
1996
;
5 Suppl 1
:
121
-4.
(107)
Parsons WD, Carmella SG, Akerkar S, Bonilla LE, Hecht SS. A metabolite of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in the urine of hospital workers exposed to environmental tobacco smoke.
Cancer Epidemiol Biomarkers Prev
 
1998
;
7
:
257
-60.
(108)
Richie JP Jr, Carmella SG, Muscat JE, Scott DG, Akerkar SA, Hecht SS. Differences in the urinary metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in black and white smokers.
Cancer Epidemiol Biomarkers Prev
 
1997
;
6
:
783
-90.
(109)
Caraballo RS, Giovino GA, Pechacek TF, Mowery PD, Richter PA, Strauss WJ, et al. Racial and ethnic differences in serum cotinine levels of cigarette smokers: Third National Health and Nutrition Examination Survey, 1988-1991.
JAMA
 
1998
;
280
:
135
-9.
(110)
Perez-Stable EJ, Herrera B, Jacob P 3rd, Benowitz NL. Nicotine metabolism and intake in black and white smokers.
JAMA
 
1998
;
280
:
152
-56.
(111)
Tokiwa H, Sera N, Horikawa K, Nakanishi Y, Shigematu N. The presence of mutagens/carcinogens in the excised lung and analysis of lung cancer induction.
Carcinogenesis
 
1993
;
14
:
1933
-8.
(112)
Seto H, Ohkubo T, Kanoh T, Koike M, Nakamura K, Kawahara Y. Determination of polycyclic aromatic hydrocarbons in the lung.
Arch Environ Contam Toxicol
 
1993
;
24
:
498
-503.
(113)
Jongeneelen FJ. Methods for routine biological monitoring of carcinogenic PAH-mixtures.
Sci Total Environ
 
1997
;
199
:
141
-9.
(114)
Strickland P, Kang D, Sithisarankul P. Polycyclic aromatic hydrocarbon metabolites in urine as biomarkers of exposure and effect.
Environ Health Perspect
 
1996
;
104 Suppl 5
:
927
-32.
(115)
Sithisarankul P, Vineis P, Kang D, Rothman N, Caporaso N, Strickland P. The association of 1-hydroxypyrene-glucuronide in human urine with cigarette smoking and broiled or roasted meat consumption.
Biomarkers
 
1997
;
2
:
217
-21.
(116)
Ariese F, Verkaik M, Hoornweg GP, van de Nesse RJ, Jukema-Leenstra SR, Hofstraat JW, et al. Trace analysis of 3-hydroxy benzo[ a ]pyrene in urine for the biomonitoring of human exposure to polycyclic aromatic hydrocarbons.
J Anal Toxicol
 
1994
;
18
:
195
-204.
(117)
Grimmer G, Jacob J, Dettbarn G, Naujack KW. Determination of urinary metabolites of polycyclic aromatic hydrocarbons (PAH) for the risk assessment of PAH-exposed workers.
Int Arch Occup Environ Health
 
1997
;
69
:
231
-9.
(118)
Mumford JL, Li X, Hu F, Lu XB, Chuang JC. Human exposure and dosimetry of polycyclic aromatic hydrocarbons in urine from Xuan Wei, China, with high lung cancer mortality associated with exposure to unvented coal smoke.
Carcinogenesis
 
1995
;
16
:
3031
-6.
(119)
Becher G, Bjorseth A. Determination of exposure to polycyclic aromatic hydrocarbons by analysis of human urine.
Cancer Lett
 
1983
;
17
:
301
-11.
(120)
Haugen A, Becher G, Benestad C, Vahakangas K, Trivers GE, Newman MJ, et al. Determination of polycyclic aromatic hydrocarbons in the urine, benzo( a )pyrene diol epoxide-DNA adducts in lymphocyte DNA, and antibodies to the adducts in sera from coke oven workers exposed to measured amounts of polycyclic aromatic hydrocarbons in the work atmosphere.
Cancer Res
 
1986
;
46
:
4178
-83.
(121)
Weston A, Bowman ED, Carr P, Rothman N, Strickland PT. Detection of metabolites of polycyclic aromatic hydrocarbons in human urine.
Carcinogenesis
 
1993
;
14
:
1053
-5.
(122)
Bowman ED, Rothman N, Hackl C, Santella RM, Weston A. Interindividual variation in the levels of certain urinary polycyclic aromatic hydrocarbon metabolites following medicinal exposure to coal tar ointment.
Biomarkers
 
1997
;
2
:
321
-7.
(123)
Bartsch H. DNA adducts in human carcinogenesis: etiological relevance and structure-activity relationship.
Mutat Res
 
1996
;
340
:
67
-79.
(124)
Petruzzelli S, Camus AM, Carrozzi L, Ghelarducci L, Rindi M, Menconi G, et al. Long-lasting effects of tobacco smoking on pulmonary drug-metabolizing enzymes: a case-control study on lung cancer patients.
Cancer Res
 
1988
;
48
:
4695
-700.
(125)
McLemore TL, Adelberg S, Liu MC, McMahon NA, Yu SJ, Hubbard WC, et al. Expression of CYP1A1 gene in patients with lung cancer: evidence for cigarette smoke-induced gene expression in normal lung tissue and for altered gene regulation in primary pulmonary carcinomas.
J Natl Cancer Inst
 
1990
;
82
:
1333
-9.
(126)
Rojas M, Camus AM, Alexandrov K, Husgafvel-Pursiainen K, Anttila S, Vainio H, et al. Stereoselective metabolism of (−)-benzo[ a ]pyrene-7,8-diol by human lung microsomes and peripheral blood lymphocytes: effect of smoking.
Carcinogenesis
 
1992
;
13
:
929
-33.
(127)
Alexandrov K, Rojas M, Geneste O, Castegnaro M, Camus AM, Petruzzelli S, et al. An improved fluorometric assay for dosimetry of benzo[ a ]pyrene diol-epoxide-DNA adducts in smokers' lung: comparisons with total bulky adducts and aryl hydrocarbon hydroxylase activity.
Cancer Res
 
1992
;
52
:
6248
-53.
(128)
Rojas M, Alexandrov K, Cascarbi I, Brockmoller J, Likhachev A, Pozharisski K, et al. High benzo[ a ]pyrene diol-epoxide DNA adduct levels in lung and blood cells from individuals with combined CYP1A1 MspI/MspI-GSTM1*0/*0 genotypes.
Pharmacogenetics
 
1997
;
8
:
109
-18.
(129)
Weston A, Bowman ED. Fluorescence detection of benzo[ a ]pyrene-DNA adducts in human lung.
Carcinogenesis
 
1991
;
12
:
1445
-9.
(130)
Corley J, Hurtubise RJ, Bowman ED, Weston A. Solid matrix, room temperature phosphorescence identification and quantitation of the tetrahydrotetrols derived from the acid hydrolysis of benzo[ a ]pyrene-DNA adducts from human lung.
Carcinogenesis
 
1995
;
16
:
423
-6.
(131)
Poirier MC, Weston A. Human DNA adduct measurements: state of the art.
Environ Health Perspect
 
1996
;
104 Suppl 5
:
883
-93.
(132)
Phillips DH. DNA adducts in human tissues: biomarkers of exposure to carcinogens in tobacco smoke.
Environ Health Perspect
 
1996
;
104 Suppl 3
:
453
-8.
(133)
Santella RM. DNA adducts in humans as biomarkers of exposure to environmental and occupational carcinogens.
Environ Carcinog Ecotoxicol Rev
 
1991
;
C9
:
57
-81.
(134)
Tang D, Santella RM, Blackwood AM, Young TL, Mayer J, Jaretzki A, et al. A molecular epidemiological case-control of lung cancer.
Cancer Epidemiol Biomarkers Prev
 
1995
;
4
:
341
-6.
(135)
Ryberg D, Hewer A, Phillips DH, Haugen A. Different susceptibility to smoking-induced DNA damage among male and female lung cancer patients.
Cancer Res
 
1994
;
54
:
5801
-3.
(136)
Godschalk RWL, Maas LM, Van Zandwijk N, van't Veer LJ, Breedijk A, Borm PJ, et al. Differences in aromatic-DNA adduct levels between alveolar macrophages and subpopulations of white blood cells from smokers.
Carcinogenesis
 
1998
;
19
:
819
-25.
(137)
Kriek E, Rojas M, Alexandrov K, Bartsch H. Polycyclic aromatic hydrocarbon-DNA adducts in humans: relevance as biomarkers for exposure and cancer risk.
Mutat Res
 
1998
;
400
:
215
-31.
(138)
Ryberg D, Hewer A, Phillips DH, Haugen A. Different susceptibility to smoking-induced DNA damage among male and female lung cancer patients.
Cancer Res
 
1994
;
54
:
5801
-3.
(139)
Kure EH, Ryberg D, Hewer A, Phillips DH, Skaug V, Baera R, Haugen A. p53 mutations in lung tumors: relationship to gender and lung DNA adduct levels.
Carcinogenesis
 
1996
;
17
:
2201
-5.
(140)
Zang EA, Wynder EL. Differences in lung cancer risks between men and women: Examination of the evidence.
J Natl Cancer Inst
 
1996
;
88
:
183
-92.
(141)
Brunmark P, Harriman S, Skipper PL, Wishnok JS, Amin S, Tannenbaum SR. Identification of subdomain IB in human serum albumin as a major binding site for polycyclic aromatic hydrocarbon epoxides.
Chem Res Toxicol
 
1997
;
10
:
880
-6.
(142)
Day BW, Naylor S, Gan LS, Sahali Y, Nguyen TT, Skipper PL, et al. Molecular dosimetry of polycyclic aromatic hydrocarbon epoxides and diol epoxides via hemoglobin adducts.
Cancer Res
 
1990
;
50
:
4611
-8.
(143)
Day BW, Naylor S, Gan LS, Sahali Y, Nguyen TT, Skipper PL, et al. Gas chromatographic-mass spectrometric analysis of diols and tetrols from reactions of polycyclic aromatic hydrocarbon epoxides with hemoglobin.
J Chromatogr
 
1991
;
562
:
563
-71.
(144)
Day BW, Skipper PL, Zaia J, Singh K, Tannenbaum SR. Enantiospecificity of covalent adduct formation by benzo[ a ]pyrene anti-diol epoxide with human serum albumin.
Chem Res Toxicol
 
1994
;
7
:
829
-35.
(145)
Myers SR, Spinnato JA, Pinorini MT. Chromatographic characterization of hemoglobin benzo[ a ]pyrene-7,8-diol-9,10-epoxide adducts.
Fundam Appl Toxicol
 
1996
;
29
:
94
-101.
(146)
Pastorelli R, Restano J, Guanci M, Maramonte M, Magagnotti C, Allevi R, et al. Hemoglobin adducts of benzo[ a ]pyrene diolepoxide in newspaper vendors: association with traffic exhaust.
Carcinogenesis
 
1996
;
17
:
2389
-94.
(147)
Melikian AA, Sun P, Coleman S, Amin S, Hecht SS. Detection of DNA and globin adducts of polynuclear aromatic hydrocarbon diol epoxides by gas chromatography-mass spectrometry and [ 3 H]CH 3 I postlabeling of released tetraols.
Chem Res Toxicol
 
1996
;
9
:
508
-16.
(148)
Melikian AA, Sun P, Pierpont C, Coleman S, Hecht SS. Gas chromatographic-mass spectrometric determination of benzo[ a ]pyrene and chrysene diol epoxide globin adducts in humans.
Cancer Epidemiol Biomarkers Prev
 
1997
;
6
:
833
-9.
(149)
Kato S, Petruzzelli S, Bowman ED, Turteltaub KW, Blomeke B, Weston A, et al. 7-Alkyldeoxyguanosine adduct detection by two-step HPLC and the 32 P-postlabeling assay.
Carcinogenesis
 
1993
;
14
:
545
-50.
(150)
Shields PG, Povey AC, Wilson VL, Weston A, Harris CC. Combined high-performance liquid chromatography/ 32 P-postlabeling assay of N 7 -methyldeoxyguanosine.
Cancer Res
 
1990
;
50
:
6580
-4.
(151)
Mustonen R, Schoket B, Hemminki K. Smoking-related DNA adducts: 32 P-postlabeling analysis of 7-methylguanine in human bronchial and lymphocyte DNA.
Carcinogenesis
 
1993
;
14
:
151
-4.
(152)
Kato S, Bowman ED, Harrington AM, Blomeke B, Shields PG. Human lung carcinogen-DNA adduct levels mediated by genetic polymorphisms in vivo.
J Natl Cancer Inst
 
1995
;
87
:
902
-7.
(153)
Blomeke B, Greenblatt MJ, Doan VD, Bowman ED, Murphy SE, Chen CC, et al. Distribution of 7-alkyl-2′-deoxyguanosine adduct levels in human lung.
Carcinogenesis
 
1996
;
17
:
741
-8.
(154)
Petruzzelli S, Tavanti LM, Celi A, Giuntini C. Detection of N 7 -methyldeoxyguanosine adducts in human pulmonary alveolar cells.
Am J Respir Cell Mol Biol
 
1996
;
15
:
216
-23.
(155)
Wilson VL, Weston A, Manchester DK, Trivers GE, Roberts DW, Kadlubar FF, et al. Alkyl and aryl carcinogen adducts detected in human peripheral lung.
Carcinogenesis
 
1989
;
10
:
2149
-53.
(156)
Foiles PG, Akerkar SA, Carmella SG, Kagan M, Stoner GD, Resau JH, et al. Mass spectrometric analysis of tobacco-specific nitrosamine-DNA adducts in smokers and nonsmokers.
Chem Res Toxicol
 
1991
;
4
:
364
-8.
(157)
Carmella SG, Kagan SS, Kagan M, Foiles PG, Palladino G, Quart AM, et al. Mass spectrometric analysis of tobacco-specific nitrosamine hemoglobin adducts in snuff dippers, smokers, and nonsmokers.
Cancer Res
 
1990
;
50
:
5438
-45.
(158)
Falter B, Kutzer C, Richter E. Biomonitoring of hemoglobin adducts: aromatic amines and tobacco-specific nitrosamines.
Clin Investig
 
1994
;
72
:
364
-71.
(159)
Kutzer C, Branner B, Zwickenpflug W, Richter E. Simultaneous solid-phase extraction and gas chromatographic-mass spectrometric determination of hemoglobin adducts from tobacco-specific nitrosamines and aromatic amines.
J Chromatogr Sci
 
1997
;
35
:
1
-7.
(160)
Atawodi SE, Lea S, Nyberg F, Mukeria A, Constantinescu V, Ahrens W, Brueske-Hohlfield I, et al. 4-Hydroxy-1-(3-pyridyl)-1-butanone-hemoglobin adducts as biomarkers of exposure to tobacco smoke: validation of a method to be used in multicenter studies.
Cancer Epidemiol Biomarkers Prev
 
1998
;
7
:
817
-21.
(161)
Kopplin A, Eberle-Adamkiewicz G, Glusenkamp KH, Nehls P, Kirstein U. Urinary excretion of 3-methyladenine and 3-ethyladenine after controlled exposure to tobacco smoke.
Carcinogenesis
 
1995
;
16
:
2637
-41.
(162)
Prevost V, Shuker DE. Cigarette smoking and urinary 3-alkyladenine excretion in man.
Chem Res Toxicol
 
1996
;
9
:
439
-44.
(163)
Sancar A. DNA excision repair.
Ann Rev Biochem
 
1996
;
65
:
43
-81.
(164)
Pegg AE, Dolan ME, Moschel RC. Structure, function, and inhibition of O 6 -alkylguanine-DNA alkyltransferase.
Prog Nucleic Acid Res Mole Biol
 
1995
;
51
:
167
-223.
(165)
Singer B, Hang B. What structural features determine repair enzyme specificity and mechanism in chemically modified DNA?
Chem Res Toxicol
 
1997
;
10
:
713
-32.
(166)
Vahakangas K, Trivers GE, Plummer S, Hayes RB, Krokan H, Rowe M, et al. O 6 -methylguanine-DNA methyltransferase and uracil DNA glycosylase in human broncho-alveolar lavage cells and peripheral blood mononuclear cells from tobacco smokers and non-smokers.
Carcinogenesis
 
1991
;
12
:
1389
-94.
(167)
Slupphaug G, Lettrem I, Myrnes B, Krokan HE. Expression of O 6 -methylguanine-DNA methyltransferase and uracil-DNA glyosylase in human placentae from smokers and non-smokers.
Carcinogenesis
 
1992
;
13
:
1769
-73.
(168)
Drin I, Schoket B, Kostic S, Vincze I. Smoking-related increase in O 6 -alkylguanine-DNA alkyltransferase activity in human lung tissue.
Carcinogenesis
 
1994
;
15
:
1535
-9.
(169)
Mattern J, Koomagi R, Volm M. Smoking-related increase of O 6 -methylguanine-DNA methyltransferase expression in human lung carcinomas.
Carcinogenesis
 
1998
;
19
:
1247
-50.
(170)
Belinsky SA, Dolan ME, White CM, Maronpot RR, Pegg AE, Anderson MW. Cell specific differences in O 6 -methylguanine-DNA methyltransferase activity and removal of O 6 -methylguanine in rat pulmonary cells.
Carcinogenesis
 
1988
;
9
:
2053
-8.
(171)
Liu XK, Spratt TE, Murphy SE, Peterson LA. Pyridyloxobutylation of guanine residues by 4-[(acetoxymethyl)nitrosamino]-1-(3-pyridyl)-1-butanone generates substrates of O 6 -alkylguanine-DNA alkyltransferase.
Chem Res Toxicol
 
1996
;
9
:
949
-53.
(172)
Wang L, Spratt TE, Liu XK, Hecht SS, Pegg AE, Peterson LA. Pyridyloxobutyl adduct O 6 -[4-oxo-4-(3-pyridyl)butyl]guanine is present in 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone-treated DNA and is a substrate for O 6 -alkylguanine-DNA alkytransferase.
Chem Res Toxicol
 
1997
;
10
:
562
-7.
(173)
Peterson LA, Liu XK, Hecht SS. Pyridyloxobutyl DNA adducts inhibit the repair of O 6 -methylguanine.
Cancer Res
 
1993
;
53
:
2780
-5.
(174)
Tang MS, Pierce JR, Doisy RP, Nazimiec ME, MacLeod MC. Differences and similarities in the repair of two benzo[ a ]pyrene diol isomers induced DNA adducts by uvrA, uvrB, and uvrC gene products.
Biochemistry
 
1992
;
31
:
8429
-36.
(175)
Chen RH, Maher VM, Brouwer J, van de Putte P, McCormick JJ. Preferential repair and strand-specific repair of benzo[ a ]pyrene diol epoxide adducts in the HPRT gene of diploid human fibroblasts.
Proc Natl Acad Sci U S A
 
1992
;
89
:
5413
-7.
(176)
Hess MT, Gunz D, Luneva N, Geacintov NE, Naegeli H. Base pair conformation-dependent excision of benzo[ a ]pyrene diol epoxide-guanine adducts by human nucleotide excision repair enzymes.
Mol Cell Biol
 
1997
;
17
:
7069
-76.
(177)
Wei Q, Spitz MR. The role of DNA repair capacity in susceptibility to lung cancer: a review.
Cancer Metastasis Rev
 
1997
;
16
:
295
-307.
(178)
Pryor WA. Cigarette smoke radicals and the role of free radicals in chemical carcinogenicity.
Environ Health Perspect
 
1997
;
105 Suppl 4
:
875
-82.
(179)
Flicker TM, Green SA. Detection and separation of gas-phase carbon-centered radicals from cigarette smoke and diesel exhaust.
Anal Chem
 
1998
;
70
:
2208
-12.
(180)
Pryor WA, Hales BJ, Premovic PI, Church DF. The radicals in cigarette tar: their nature and suggested physiological implications.
Science
 
1983
;
220
:
425
-7.
(181)
Pryor WA, Stone K, Zang LY, Bermudez E. Fractionation of aqueous cigarette tar extracts: fractions that contain the tar radical cause DNA damage.
Chem Res Toxicol
 
1998
;
11
:
441
-8.
(182)
Nakayama T, Kodama M, Nagata C. Generation of hydrogen peroxide and superoxide anion radical from cigarette smoke.
Gann
 
1984
;
75
:
95
-8.
(183)
Nakayama T, Kaneko M, Kodama M, Nagata C. Cigarette smoke induces DNA single-strand breaks in human cells.
Nature
 
1985
;
314
:
462
-4.
(184)
Nakayama T, Kaneko M, Kodama M. Volatile gas components contribute to cigarette smoke induced DNA single strand breaks in cultured human cells.
Agric Biol Chem
 
1986
;
50
:
3219
-20.
(185)
Fielding S, Short C, Davies K, Wald N, Bridges BA, Waters R. Studies on the ability of smoke from different types of cigarettes to induce DNA single-strand breaks in cultured human cells.
Mutat Res
 
1989
;
214
:
147
-51.
(186)
Leanderson P, Tagesson C. Cigarette smoke-induced DNA-damage: role of hydroquinone and catechol in the formation of the oxidative DNA-adduct, 8-hydroxydeoxyguanosine.
Chem Biol Interact
 
1990
;
75
:
71
-81.
(187)
Leanderson P, Tagesson C. Cigarette smoke-induced DNA damage in cultured human lung cells: role of hydroxyl radicals and endonuclease activation.
Chem Biol Interact
 
1992
;
81
:
197
-208.
(188)
Yoshie Y, Ohshima H. Synergistic induction of DNA strand breakage by cigarette tar and nitric oxide.
Carcinogenesis
 
1997
;
18
:
1359
-63.
(189)
Muller T, Haussmann HJ, Schepers G. Evidence of peroxynitrite as an oxidative stress-inducing compound of aqueous cigarette smoke fractions.
Carcinogenesis
 
1997
;
18
:
295
-301.
(190)
Frei B, Forte TM, Ames BN, Cross CE. Gas phase oxidants of cigarette smoke induce lipid peroxidation and changes in lipoprotein properties in human blood plasma.
Biochem J
 
1991
;
277
:
133
-8.
(191)
Reznick AZ, Cross CE, Hu ML, Suzuki YJ, Khwaja S, Safadi A, et al. Modification of plasma proteins by cigarette smoke as measured by protein carbonyl formation.
Biochem J
 
1992
;
286
:
607
-11.
(192)
Schechtman G, Byrd JC, Hoffmann R. Ascorbic acid requirements for smokers: analysis of a population survey.
Am J Clin Nutr
 
1991
;
53
:
1466
-70.
(193)
Morrow JD, Frei B, Longmire AW, Gaziano JM, Lynch SM, Shyr Y, et al. Increase in circulating products of lipid peroxidation (F 2 -isoprostanes) in smokers. Smoking as a cause of oxidative damage.
N Engl J Med
 
1995
;
332
:
1198
-203.
(194)
Asami S, Manabe H, Miyake J, Tsurudome Y, Hirano T, Yamaguchi R, et al. Cigarette smoking induces an increase in oxidative DNA damage, 8-hydroxydeoxyguanosine, in a central site of the human lung.
Carcinogenesis
 
1997
;
18
:
1763
-6.
(195)
Asami S, Hirano T, Yamaguchi Y, Tomioka Y, Itoh H, Kasai H. Increase of a type of oxidative DNA damage, 8-hydroxyguanine, and its repair activity in human leukocytes by cigarette smoking.
Cancer Res
 
1996
;
56
:
2546
-9.
(196)
Fraga CG, Motchnik PA, Wyrobek AJ, Rempel DM, Ames BN. Smoking and low antioxidant levels increase oxidative damage to sperm DNA.
Mutat Res
 
1996
;
351
:
199
-203.
(197)
Loft S, Vistisen K, Ewertz M, Tjonneland A, Overvad K, Poulsen HE. Oxidative DNA damage estimated by 8-hydroxydeoxyguanosine excretion in humans: influence of smoking, gender and body mass index.
Carcinogenesis
 
1992
;
13
:
2241
-7.
(198)
Prieme H, Loft S, Klarlund M, Gronbaek K, Tonnesen P, Poulsen HE. Effect of smoking cessation on oxidative DNA modification estimated by 8-oxo-7,8-dihydro-2′-deoxyguanosine excretion.
Carcinogenesis
 
1998
;
19
:
347
-51.
(199)
Takeshima Y, Seyama T, Bennett WP, Akiyama M, Tokuoka S, Inai K, et al. p53 mutations in lung cancer from nonsmoking atomic-bomb survivors.
Lancet
 
1993
;
342
:
1520
-1.
(200)
Chen JX, Zheng Y, West M, Tang M. Carcinogens preferentially bind at methylated CpG in the p53 mutational hot spots.
Cancer Res
 
1998
;
58
:
2070
-5.
(201)
Denissenko MF, Pao A, Tang M, Pfeifer GP. Preferential formation of benzo[ a ]pyrene adducts at lung cancer mutational hotspots in P53.
Science
 
1996
;
274
:
430
-2.
(202)
Denissenko MF, Chen JX, Tang MS, Pfeifer GP. Cytosine methylation determines hot spots of DNA damage in the human P53 gene.
Proc Natl Acad Sci U S A
 
1997
;
94
:
3893
-8.
(203)
Delclos KB, Kadlubar FF. Carcinogenic aromatic amines and amides. In: Guengerich FP, editor. Comprehensive toxicology: chemical carcinogens and anticarcinogens. Vol 12. Oxford (U.K.): Elsevier Science; 1997. p. 141-70.
(204)
Shukla R, Liu T, Geacintov NE, Loechler EL. The major, N 2 -dG adduct of (+)-anti-B[ a ]PDE shows a dramatically different mutagenic specificity (predominantly, G→A) in a 5′-CGT-3′ sequence context.
Biochemistry
 
1997
;
36
:
10256
-61.
(205)
Moriya M, Zhang W, Johnson F, Grollman AP. Mutagenic potency of exocyclic DNA adducts: marked differences between Escherichia coli and simian kidney cells.
Proc Natl Acad Sci U S A
 
1994
;
91
:
11899
-903.
(206)
Moriya M. Single-stranded shuttle phagemid for mutagenesis studies in mammalian cells: 8-oxoguanine in DNA induces targeted G.C→T.A transversions in simian kidney cells.
Proc Natl Acad Sci U S A
 
1993
;
90
:
1122
-6.
(207)
Ronai ZA, Gradia S, Peterson LA, Hecht SS. G to A transitions and G to T transversions in codon 12 of the Ki-ras oncogene isolated from mouse lung tumors induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and related DNA methylating and pyridyloxobutylating agents.
Carcinogenesis
 
1993
;
14
:
2419
-22.
(208)
Burcham PC, Marnett LJ. Site-specific mutagenesis by a propanodeoxyguanosine adduct carried on an M13 genome.
J Biol Chem
 
1994
;
269
:
28844
-50.
(209)
Nesnow S, Ross JA, Mass MJ, Stoner GD. Mechanistic relationships between DNA adducts, oncogene mutations, and lung tumorigenesis in strain A mice.
Exp Lung Res
 
1998
;
24
:
395
-405.
(210)
Belinsky SA, Swafford DS, Finch GL, Mitchell CE, Kelly G, Hahn FF, et al. Alterations in the K-ras and p53 genes in rat lung tumors.
Env Health Perspect
 
1997
;
105 Suppl 4
:
901
-6.
(211)
Merlo A, Herman JG, Mao L, Lee DL, Gabrielson E, Burger PC, et al. 5′ CpG island methylation is associated with transcriptional silencing of the tumour suppressor p16/CDKN2/MTS1 in human cancers.
Nat Med
 
1995
;
1
:
686
-92.
(212)
Otterson GA, Kratzke RA, Coxon A, Kim YW, Kaye FJ. Absence of p16 INK4 protein is restricted to the subset of lung cancer lines that retains wildtype RB.
Oncogene
 
1994
;
9
:
3375
-8.
(213)
Belinsky SA, Nikula KJ, Palmisano WA, Michels R, Saccomanno G, Gabrielson E, et al. Aberrant methylation of p16 INK4a is an early event in lung cancer and a potential biomarker for early diagnosis.
Proc Natl Acad Sci U S A
 
1998
;
95
:
11891
-6.
(214)
Sabourin CL, Wang QS, Ralston SL, Evans J, Coate J, Herzog CR, et al. Expression of cell cycle proteins in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced mouse lung tumors.
Exp Lung Res
 
1998
;
24
:
499
-521.
(215)
Issa JP, Baylin SB, Belinsky SA. Methylation of the estrogen receptor CpG island in lung tumors is related to the specific type of carcinogen exposure.
Cancer Res
 
1996
;
56
:
3655
-8.
(216)
Nelson HH, Wiencke JK, Gunn L, Wain JC, Christiani DC, Kelsey KT. Chromosome 3p14 alterations in lung cancer: evidence that FHIT exon deletion is a target of tobacco carcinogens and asbestos.
Cancer Res
 
1998
;
58
:
1804
-7.
(217)
Rothman N, Stewart WF, Schulte PA. Incorporating biomarkers into cancer epidemiology: a matrix of biomarker and study design categories.
Cancer Epidemiol Biomarkers Prev
 
1995
;
4
:
301
-11.
(218)
Perera FP. Molecular epidemiology: insights into cancer susceptibility, risk assessment, and prevention.
J Natl Cancer Inst
 
1996
;
88
:
496
-509.
(219)
Rannug A, Alexandrie AK, Persson J, Ingelman-Sundberg M. Genetic polymorphism of cytochromes P450 1A1, 2D6 and 2E1: regulation and toxicological significance.
J Occup Environ Med
 
1995
;
37
:
25
-36.
(220)
Spivack SD, Fasco MJ, Walker VE, Kaminsky LS. The molecular epidemiology of lung cancer.
Crit Rev Toxicol
 
1997
;
27
:
319
-65.
(221)
Garte S. The role of ethnicity in cancer susceptibility gene polymorphisms: the example of CYP1A1.
Carcinogenesis
 
1998
;
19
:
1329
-32.
(222)
Zhang ZY, Fasco MJ, Huang L, Guengerich FP, Kaminsky LS. Characterization of purified human recombinant cytochrome P4501A1-Ile462 and -Val462: assessment of a role for the rare allele in carcinogenesis.
Cancer Res
 
1996
;
56
:
3926
-33.
(223)
Crofts F, Taioli E, Trachman J, Cosma GN, Currie D, Toniolo P, et al. Functional significance of different human CYP1A1 genotypes.
Carcinogenesis
 
1994
;
15
:
2961
-3.
(224)
Wu MT, Huang SL, Ho CK, Yeh YF, Christiani DC. Cytochrome P450 1A1 MspI. polymorphism and urinary 1-hydroxypyrene concentrations in coke-oven workers.
Cancer Epidemiol Biomarkers Prev
 
1998
;
7
:
823
-9.
(225)
Ayesh R, Idle JR, Ritchie JC, Crothers MJ, Hetzel MR. Metabolic oxidation phenotypes as markers for susceptibility to lung cancer.
Nature
 
1984
;
312
:
169
-70.
(226)
Caporaso NE, DeBaun MR, Rothman N. Lung cancer and CYP 2D6 (the debrisoquine polymorphism): sources of heterogeneity in the proposed association.
Pharmacogenetics
 
1998
;
5
:
5129
-34.
(227)
Shaw GL, Falk RT, Frame JN, Weiffenbach B, Nesbitt JC, Pass HI, et al. Genetic polymorphism of CYP2D6 and lung cancer risk.
Cancer Epidemiol Biomarkers Prev
 
1998
;
7
:
215
-9.
(228)
Crespi CL, Penman BW, Gelboin HV, Gonzalez F. A tobacco smoke-derived nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, is activated by multiple human cytochrome P450s including the polymorphic human cytochrome P4502D6.
Carcinogenesis
 
1991
;
12
:
1197
-201.
(229)
Penman BW, Reece J, Smith T, Yang CS, Gelboin HV, Gonzalez FJ, et al. Characterization of a human cell line expressing high levels of cDNA-derived CYP2D6.
Pharmacogenetics
 
1993
;
3
:
28
-9.
(230)
Le Marchand L, Sivaraman L, Pierce L, Seifried A, Lum A, Wilkens LR, et al. Associations of CYP1A1, GSTM1, and CYP2E1 polymorphisms with lung cancer suggest cell type specificities to tobacco carcinogens.
Cancer Res
 
1998
;
58
:
4858
-63.
(231)
McWilliams JE, Sanderson BJ, Harris EL, Richert-Boe KE, Henner WD. Glutathione S -transferase M1 (GSTM1) deficiency and lung cancer risk.
Cancer Epidemiol Biomarkers Prev
 
1995
;
4
:
589
-94.
(232)
Rebbeck TR. Molecular epidemiology of the human glutathione S -transferase genotypes GSTM1 and GSTT1 in cancer susceptibility.
Cancer Epidemiol Biomarkers Prev
 
1997
;
6
:
733
-43.
(233)
Tang DL, Rundle A, Warburton D, Santella RM, Tsai WY, Chiamprasert S, et al. Associations between both genetic and environmental biomarkers and lung cancer: evidence of a greater risk of lung cancer in women smokers.
Carcinogenesis
 
1998
;
19
:
1949
-53.
(234)
el-Zein R, Zwischenberger JB, Wood TG, Abdel-Rahman SZ, Brekelbaum C, Au WW. Combined genetic polymorphism and risk for development of lung cancer.
Mutat Res
 
1997
;
381
:
189
-200.
(235)
Hsu TC, Spitz MR, Schantz SP. Mutagen sensitivity: a biological marker of cancer susceptibility.
Cancer Epidemiol Biomarkers Prev
 
1991
;
1
:
83
-9.
(236)
Klein-Szanto AJ, Iizasa T, Momiki S, Garcia-Palazzo I, Caamano J, Metcalf R, et al. A tobacco-specific N -nitrosamine or cigarette smoke condensate causes neoplastic transformation of xenotransplanted human bronchial epithelial cells.
Proc Natl Acad Sci U S A
 
1992
;
89
:
6693
-7.
(237)
Hoffmann D, Rivenson A, Murphy SE, Chung FL, Amin S, Hecht SS. Cigarette smoking and adenocarcinoma of the lung: the relevance of nicotine-derived N- nitrosamines.
J Smoking-Related Disorders
 
1993
;
4
:
165
-89.
(238)
Wynder EL, Hoffmann D. Re: Cigarette smoking and the histopathology of lung cancer.
J Natl Cancer Inst
 
1998
;
90
:
1486
-8.
(239)
Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, et al. Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial.
J Natl Cancer Inst
 
1996
;
88
:
1550
-9.
(240)
Hennekens CH, Buring JE, Manson JE, Stampfer M, Rosner B, Cook NR, et al. Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease.
N Engl J Med
 
1996
;
334
:
1145
-9.
(241)
The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. The Alpha-Tocopherol Beta Carotene Cancer Prevention Study Group.
N Engl J Med
 
1994
;
330
:
1029
-35.
(242)
Hurt RD, Dale LC, Fredrickson PA, Caldwell CC, Lee GA, Offord KP, et al. Nicotine patch therapy for smoking cessation combined with physician advice and nurse follow-up. One-year outcome and percentage of nicotine replacement.
JAMA
 
1994
;
271
:
595
-607.
(243)
Hughes JR. The future of smoking cessation therapy in the United States.
Addiction
 
1996
;
91
:
1797
-802.
(244)
Emmons KM, Kawachi I, Barclay G. Tobacco control—a brief review of its history and progress for the future.
Hematol Oncol Clin North Am
 
1997
;
11
:
177
-95.
(245)
Hecht SS. Approaches to chemoprevention of lung cancer based on carcinogens in tobacco smoke.
Environ Health Perspect
 
1997
;
105 Suppl 4
:
955
-63.
(246)
Kelloff GJ, Boone CW, Crowell JA, Steele VE, Lubet RA, Doody LA, et al. New agents for cancer chemoprevention.
J Cell Biochem Suppl
 
1996
;
26
:
1
-28.
(247)
Wattenberg LW, Wiedmann TS, Estensen RD, Zimmerman CL, Steele VE, Kelloff GJ. Chemoprevention of pulmonary carcinogenesis by aerosolized budesonide in female A/J mice.
Cancer Res
 
1997
;
57
:
5489
-92.
(248)
Hecht SS, Kenney PM, Wang M, Trushin N, Agarwal S, Rao AV, et al. Evaluation of butylated hydroxyanisole, myo -inositol, curcumin, esculetin, resveratrol, and lycopene as inhibitors of benzo[ a ]pyrene plus 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in A/J mice.
Cancer Lett
  . In press
1998
.
(249)
You M, Bergman G. Preclinical and clinical models of lung cancer chemoprevention.
Hematol Oncol Clin North Am
 
1998
;
12
:
1037
-53.