Tobacco Smoke Carcinogens and Lung Cancer

Hecht, Stephen S.

doi:10.1093/jnci/91.14.1194

Cited by 1,700 publications

(1,007 citation statements)

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“…[22][23][24] The presence of CYP1A2 and CYP3A4 in intestinal metaplasia suggests that CYP1A2 and CYP3A4 may play a role in the early stages of gastric carcinogenesis by activating nitrosamines to mutagenic products. 25 It has been postulated that gastric cancer is the end result of a pre-cancerous sequence of events: superficial gastritis, chronic atrophic gastritis, intestinal metaplasia and dysplasia. 26 These lesions are prevalent in populations at a high risk for gastric cancer.…”

Section: Discussionmentioning

confidence: 99%

Effects of cytochrome P450 (CYP) 2A6 gene deletion and CYP2E1 genotypes on gastric adenocarcinoma

Tsukino

Kuroda

Qiu

et al. 2002

Intl Journal of Cancer

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Cytochrome P450 (CYP) 2A6 and CYP2E1 are enzymes with a high ability to activate a nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), to its potent and ultimate carcinogens. The polymorphic CYP2A6 and CYP2E1 have been implicated in increased susceptibility to certain malignancies. In our study, 120 Japanese patients with gastric adenocarcinoma and 158 healthy controls were compared for frequencies of CYP2A6 and CYP2E1 genotypes. The frequency with which the subjects carried homozygotes of the CYP2A6 gene deletion allele, which causes lack of the enzyme activity, was significantly higher in the gastric cancer patients than in the healthy control subjects (OR ‫؍‬ 3.14, 95% confidence interval (95% CI) ‫؍‬ 1.05-9.41). Subdividing gastric adenocarcinoma according to tumor differentiation, patients with the well-differentiated type were 4. Although gastric cancer incidence has fallen markedly over the past 50 years in industrialized nations, it remains the second leading cause of cancer death in Japan. Epidemiological and experimental evidence have indicated that excess salt intake, which promotes cell replication, increases gastric cancer risk. 1,2 There is considerable evidence to support the view that carcinogenic N-nitrosamine derivatives are important factors in human cancer, including gastric cancer. The chemical mechanisms of carcinogenesis by these nitrosamines in humans are therefore of considerable interest. 3,4 Numerous studies have shown that several cytochrome P450 (CYP) enzymes, particularly cytochrome P4502A6 (CYP2A6) and cytochrome P4502E1 (CYP2E1), catalyze metabolic activation of nitrosamine derivatives, including N-nitroso-dialkyiamines and tobacco-smoke-related nitrosamine. [5][6][7][8] Genetic polymorphisms for CYP2A6 have been described and 2 variant alleles associated with reduced activity have been identified. Variant 1 (CYP2A6*2) and Variant 2 (CYP2A6*3) are the results of amino acid exchanged for wildtype (CYP2A6*1). Recently, Kitagawa et al. 9 revealed that a novel deletion genotype variant of the CYP2A6 gene was one of the major polymorphic genes in Japanese lacking CYP2A6 activity.In addition, CYP2E1 represents a major CYP isoform in the human liver and is also expressed in extrahepatic tissue. This enzyme can be induced by certain chemicals, such as ethanol and large interindividual variations have been observed, suggesting that the variation may be due to genetic polymorphism. It was reported that RsaI polymorphism, which is located in the 5Ј-flanking region of CYP2E1 gene, has been shown to be associated with the transcriptional regulation of gene expression, resulting in different expression levels of the CYP2E1 mRNA. 6 CYP2E1 participated in the metabolic activation of various N-nitrosamines, including a potent tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. 8,10 Several recent reports have investigated the role of CYP2A6 genetic polymorphisms in tobacco dependence and lung cancer risk, with conflicting results. [11][12][13][14][15] Less ...

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Section: Discussionmentioning

confidence: 99%

Effects of cytochrome P450 (CYP) 2A6 gene deletion and CYP2E1 genotypes on gastric adenocarcinoma

Tsukino

Kuroda

Qiu

et al. 2002

Intl Journal of Cancer

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“…Tobacco, a rich resource of pulmonary carcinogens, is known to cause many genetic changes through DNA mutations (Hecht, 1999). It has been also demonstrated that tobacco exposure induces epigenetic changes through promoter methylation of tumor suppressor genes (TSGs) Belinsky et al, 2003;Fujiwara et al, 2005) and proapoptotic genes (Pulling et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Cigarette smoke induces demethylation of prometastatic oncogene synuclein-γ in lung cancer cells by downregulation of DNMT3B

et al. 2007

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The prometastatic oncogene synuclein-c (SNCG) is not expressed in normal lung tissues, but it is highly expressed in lung tumors. Here, we show that cigarette smoke extract (CSE) has strong inducing effects on SNCG gene expression in A549 lung cancer cells through demethylation of SNCG CpG island. CSE treatment also augments the invasive capacity of A549 cells in an SNCG-dependent manner. To elucidate the mechanisms underlying the demethylating effects of CSE, we examined expression levels of DNA methyltransferases (DNMTs), 1, 3A and 3B in CSE-treated cells. We show that the mRNA expression of DNMT3B is specifically downregulated by CSE with a kinetics concurrent to SNCG reexpression. Utilizing siRNA to knockdown DNMT3B expression, we show that inhibition of DNMT3B directly increases SNCG mRNA expression. We further show that exogenous overexpression of DNMT3B in an SNCG-positive lung cancer cell line H292 suppresses SNCG mRNA and protein expression and induces de novo methylation of SNCG CpG island, whereas overexpression of DNMT1 or DNMT3A has no effects. Taken together, these new findings demonstrate that tobacco exposure induces the abnormal expression of SNCG in lung cancer cells through downregulation of DNMT3B. This work sheds light on the molecular understanding of demethylation of this oncogene during cancer progression.

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“…Figure 1 presents a schematic that links nicotine addiction with lung cancer by way of cigarette smoke carcinogens [Hecht, 1999]. Nicotine addiction is the reason that people continue to smoke, in spite of the well-documented health risks.…”

Section: Introductionmentioning

confidence: 99%

Tobacco smoke carcinogens and breast cancer

Hecht

2002

Environ and Mol Mutagen

186

143

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Cigarette smoking is an established cause of a variety of cancer types, but its role in breast cancer etiology is not clear. In this report, the potential role of cigarette smoke carcinogens as causes of human breast cancer is evaluated. Of over 60 known carcinogens in tobacco smoke, several are known to induce mammary tumors in laboratory animals: [4,5-b]pyridine (PhIP), 1,3-butadiene, isoprene, nitromethane, ethylene oxide, and benzene. Studies in humans demonstrate that tobacco constituents can reach breast tissue. The uptake and metabolic activation of mammary carcinogens such as polycyclic aromatic hydrocarbons (PAHs) and 4-aminobiphenyl are frequently higher in smokers than in nonsmokers. Although it is likely that specific mammary carcinogens in tobacco smoke can reach breast tissue, evidence is lacking at the present time. Some PAHs present in cigarette smoke can be metabolized to sterically hindered diol epoxides, which are potent mammary carcinogens. Thus, compounds such as benzo[c]phenanthrene (B[c]P), not classically considered to be a strong carcinogen in rodents, could nevertheless be metabolized in humans to diol epoxides carcinogenic to the breast. Collectively, the link between smoking and breast cancer is plausible but has been difficult to establish, probably because of the low carcinogen dose. Environ. Mol.

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Tobacco Smoke Carcinogens and Lung Cancer

Cited by 1,700 publications

References 139 publications

Effects of cytochrome P450 (CYP) 2A6 gene deletion and CYP2E1 genotypes on gastric adenocarcinoma

Effects of cytochrome P450 (CYP) 2A6 gene deletion and CYP2E1 genotypes on gastric adenocarcinoma

Cigarette smoke induces demethylation of prometastatic oncogene synuclein-γ in lung cancer cells by downregulation of DNMT3B

Tobacco smoke carcinogens and breast cancer

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