Tobacco-induced Carcinogenesis Research Articles

Reducing tobacco-associated lung cancer risk: a study protocol for a randomized clinical trial of AB-free kava

BackgroundTobacco use is the leading cause of many preventable diseases, resulting in premature death or disease. Given that the majority of adult who smoke want to stop, this health burden could be significantly reduced if the success rate of tobacco cessation can be improved. In addition, most adults planning to quit were interested in trying complementary approaches to facilitating tobacco cessation, which is currently lacking. Therefore, there is an unmet and urgent need for novel interventions to improve the success of tobacco cessation. If such an intervention can reduce tobacco-associated lung carcinogenesis, that will be more desirable. The goal of this project is to develop a safe and effective kava-based intervention to enable tobacco cessation and reduce lung cancer risk, which will improve the health of smokers.MethodsA randomized controlled trial will enroll 80 adults who currently smoke at least 10 cigarettes daily and randomize 1:1 into the placebo and AB-free kava arms, being exposed for 4 weeks, with a total of six visits (weeks 0, 1, 2, 4, 8, and 12) to evaluate the compliance and potential issues of AB-free kava use among the participants, explore the potential effect of the AB-free kava intervention on tobacco dependence, tobacco use, and lung carcinogenesis biomarkers. Participants will be enrolled during their primary care clinic visit.DiscussionPrimary care settings play a critical role in tobacco-related disease screening, counseling, and early intervention, as the majority of adults who smoke visit their physicians annually. Building upon our promising pilot human trial results in conjunction with ample compelling lab animal results, and consistent with evidence of kava’s benefits from epidemiological data, this trial will evaluate the compliance of AB-free kava among adults who currently smoke with no intention to quit. The other exploratory aims include (1) whether AB-free kava intervention can reduce tobacco use and tobacco dependence; (2) whether AB-free kava use suppresses tobacco-induced carcinogenesis; and (3) the potential of the mechanism-based noninvasive biomarkers in precision AB-free kava intervention. The positive results from this study are expected to provide a great opportunity to effectively reduce smoking rates and tobacco-related diseases.Trial registrationClinicalTrials.gov with the identifier: NCT05081882. Registered on October 18, 2021.

Tobacco-induced carcinogenesis and chemoprevention by some natural products

Tobacco habit is one of the main etiological factors responsible for cancer in body's multiple organs due to the presence of numerous carcinogens. In different animal models, it was evident that the carcinogens could induce carcinogenesis in multiple organs depending on its route of exposure site (e.g., skin, oral cavity, and lung), metabolism (e.g., liver and lung), and excretion (e.g., lung and kidney). It was evident that the active carcinogen metabolites could induce cellular reactive oxygen species (ROS) level, bind to DNA/RNA/proteins, thereby transforming the stem cell of the specific organs toward neoplasm. Different epidemiological studies including our own showed few natural compounds might reduce the risk of tobacco-induced carcinogenesis. The anticarcinogenic roles of crude extract as well as active compounds of such natural dietary ingredients were also evaluated by several in vivo animal models. Most of the active components have potential antioxidative, anti-inflammatory, and anticarcinogenic roles. For better understanding, the roles of three different types of compounds were selected for this review 1. Tea polyphenols from Camellia sinensis: epigallocatechin gallate and theaflavin; 2. amarogentin from Swertia chirata; and 3. Eugenol from Syzygium aromaticum. Studies showed that three types of compounds could restrict the carcinogenesis in different organs at premalignant stages. This might be due to antioxidation and activation of detoxification system, inhibition of cancer initiating stem cell population, modulation of multiple cellular pathways associated with cell cycle, cell proliferation, and survival which ultimately lead to restrict tumor development at initiation/promotion stage.

MTE10.01 Unique Biologic Aspects of Tobacco-Induced Lung Cancer

MTE10.01 Unique Biologic Aspects of Tobacco-Induced Lung Cancer

Abstract 4074: Cancer stem cells in tobacco-induced carcinogenesis and subsequent effect of ATRA-based chemoprevention

Abstract Introduction Chemoprevention is potentially the most effective method to lower the prevalence of head and neck squamous cell carcinomas (HNSCC), the sixth most common type of malignancy worldwide. The chemopreventive effects of retinoids against HNSCC have been previously reported. Retinoids however; relapse following cessation of medication is a critical problem that prevents its clinical use. The objective of this study was to determine the possible mechanism of retinoid resistance by exploring cancer stem cell mediated pathways. Experimental Procedures. In vitro cell line models of normal (NOK) and dysplastic oral keratinocytes (DOK) are being exposed to tobacco to assess the process of carcinogenic progression. The progression in the DOK and HOK cell lines will be assessed by proliferation, migration and invasion assays. The expression of stem cell markers/pathways (CD44/Hyaluronan, Wnt, Notch1, ALDH1A1) during the process of progression will be evaluated using QPCR and FACS. These cell lines will then be treated with ATRA and the subsequent effects on transformation and CSC-specific pathways further evaluated. Summary To this end, immunostaining of normal oral mucosa, potentially malignant lesions (n = 93) and malignant lesions (n = 48) for the stem cell marker CD44 was performed. CD44+ cells were found at a density of 58.57/hpf in normal mucosa, 61.56/hpf in mild dysplasia, 119.44/hpf in moderate dysplasia, and 107.6/hpf in severe dysplasia. The density of CD44+ cells in WDSCC, MDSCC and PDSCC were 183.4, 105 and 160/hpf respectively, indicates CSC cells may represent a marker of malignant progression The cell lines are currently under exposure to tobacco and the transformational changes being documented. Apart from the studies on the changes specific to CSCs, high throughput secretome and proteomic studies are also being planned to evaluate the global changes effected due to tobacco as well as due to subsequent treatment with ATRA. Conclusion This study hence attempts to provide novel insight into tobacco-induced carcinogenesis and mechanism of resistance to retinoid-based chemoprevention. Note: This abstract was not presented at the meeting. Citation Format: Subin Surendran, Christina Mimikos, Amritha Suresh, Wesley L. Hicks, Mukund Seshadri, Moni A. Kuriakose. Cancer stem cells in tobacco-induced carcinogenesis and subsequent effect of ATRA-based chemoprevention. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4074. doi:10.1158/1538-7445.AM2015-4074

Abstract 2721: Induction of aberrant crypt foci in the colon of mice exposed to tobacco carcinogen 2-amino-9H-pyrido[2,3-b]indole

Abstract Epidemiological studies indicate that tobacco smoking is a risk factor for colon cancer. However, the etiological agents in tobacco smoke remain uncertain. Heterocyclic aromatic amines (HAAs) that are produced during high-temperature cooking of the proteinaceous food are associated with the elevated risk of colon cancer. Tobacco smoking also produces HAAs, the most abundant one being 2-amino-9H-pyrido[2,3-b]indole (AαC). The carcinogenic potency of AαC is unknown in humans, but AαC forms DNA adducts in multiple organs, including liver and colon, as well as being carcinogenic in rodents. In this study, AαC-induced colon cancer risk was assessed by determining DNA adducts and putative colonic precancerous lesions, aberrant crypt foci (ACF) and dysplastic ACF. For comparison, the HAA, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), a liver and colon carcinogen in mice, and azoxymethane (AOM), a potent colon carcinogen in rodents, were also administered. AαC (400 ppm) or MeIQ (300 ppm) were fed in a high-fat diet to A/J mice (n = 12 per group) for 4 weeks. AOM was injected intraperitoneally to another 12 mice at 5 mg/kg body weight weekly for 6 weeks. At the end of carcinogen treatment, liver and colon were harvested from 4 mice from each group for DNA adduct measurement. dG-C8-AαC, dG-C8-MeIQ, and O6-methyl-dG DNA adducts were measured by liquid chromatography/mass spectrometry. The remaining 8 mice from each group were then fed a carcinogen-free diet for additional 8 weeks, and then colons harvested. Colonic total and dysplastic ACF were counted by light microscopy after appropriate staining. AαC feeding induced the greatest number of DNA adducts in liver, followed by AOM and MeIQ. AOM administration and AαC feeding induced similar numbers of DNA adducts in the colon, both of which were significantly greater than MeIQ. However, AOM administration induced a significantly greater number of total and dysplastic ACF in the colons than did feeding either AαC or MeIQ, which had similar numbers of ACF and dysplastic ACF. The high levels of AαC DNA adducts and induced dysplastic ACF in this animal model, provide biological plausibility for a causal role for AαC in tobacco-induced colorectal carcinogenesis. However, DNA adduct numbers induced by these three carcinogens was not proportional to the colonic ACF or dysplastic ACF number, suggesting that different types of DNA adducts differ in their ability to promote colonic precancerous lesions. Citation Format: Sangyub Kim, Jingshu Guo, Sabrina P. Trudo, Daniel D. Gallaher, Robert J. Turesky. Induction of aberrant crypt foci in the colon of mice exposed to tobacco carcinogen 2-amino-9H-pyrido[2,3-b]indole. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2721. doi:10.1158/1538-7445.AM2015-2721

Abstract 610: Prospective genomic characterization of small cell lung cancer by targeted next generation sequencing

Abstract INTRODUCTION: Recent studies using next generation sequencing (NGS) technologies have provided insights into the molecular landscape of small cell lung cancer (SCLC), including frequent inactivation of TP53 and RB1. However, molecular profiling of SCLC has been impeded by lack of tissue. We performed prospective genomic profiling of patients with advanced SCLC, demonstrating the ability to test small biopsy specimens, and we report trends associated with clinical characteristics. METHODS: Formalin fixed paraffin embedded surgical resections, core biopsies, and fine needle aspirates from 50 patients with SCLC were subjected to FGFR1 FISH testing, PTEN immunohistochemistry (IHC), and deep-coverage targeted NGS (median 420x) to identify single nucleotide variants, indels, and copy number alterations in a common set of 222 cancer-associated genes. Demographic and clinical data were collected. Genotyping data were stratified by smoking status, stage, and response to therapy. RESULTS: Of the 50 patients with SCLC, 58% had extensive stage disease, and 30% were resistant to first line therapy. We observed diverse genetic profiles in SCLC, with alterations occurring in 202 of 222 targeted genes. The median number of non-synonymous somatic mutations was 7. Of 526 total non-synonymous mutations, 5% were hotspot COSMIC mutations, 25% were loss-of-function, and 47% were G-to-T transversions indicative of tobacco-induced carcinogenesis. Recurrent loss-of-function mutations in RB1 (96%) and TP53 (92%) were observed. Other frequent genomic events included alterations in SOX2 (26%), EPHA5 (22%), CDKN2C (20%), MYCL1 (20%), and PIK3CA (18%). Actionable point mutations in PIK3CA, amplifications of FGFR1, amplifications of MYC, and loss of PTEN were confirmed by independent clinically validated assays. The genotyping data showed differences based on disease stage, response to therapy, and smoking status. Patients with limited disease had a higher median number of mutations detected (9 mut/tumor) than patients with extensive disease (5 mut/tumor). Tumors refractory to chemotherapy were more likely to harbor homozygous deletions including on chromosome 3p, while tumors sensitive to chemotherapy had more diversified amplifications, deletions, and mutations. The median number of mutations detected for never smokers (0 pack years), moderate smokers (<20 pack years), and heavy smokers (20+ pack years) were 3, 4.5, and 8 mut/tumor, respectively (P<0.05). None of the mutations detected in tumors from never smokers were G-to-T transversions. CONCLUSION: Comprehensive molecular profiling is feasible on clinical SCLC specimens. Our study illustrates the molecular diversity and mutational patterns in SCLC. We confirmed previously reported recurring events, and further identified associations between genomic profiles and clinical features including stage, response, and smoking status. Citation Format: Helen H. Won, M. Catherine Pietanza, Lee M. Krug, Anna M. Varghese, Natasha Rekhtman, Lu Wang, William Travis, Paul K. Paik, Gregory J. Riely, Maureen F. Zakowski, Marc Ladanyi, Mark G. Kris, Charles M. Rudin, Michael F. Berger. Prospective genomic characterization of small cell lung cancer by targeted next generation sequencing. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 610. doi:10.1158/1538-7445.AM2015-610

Abstract 3071: Epigenetic repression of miR-217 contributes to tobacco-induced esophageal carcinogenesis.

Abstract Although alterations in microRNA (miRNA; miR) expression have been implicated in the pathogenesis of a variety of human malignancies, limited information is available regarding mechanisms by which these noncoding RNAs contribute to initiation and progression of tobacco-induced esophageal cancers. In order to examine this issue, array and RT-PCR techniques were used to examine miRNA expression profiles in immortalized esophageal epithelial cells (Het-1A), as well as NCI-SB-EsC1 (EsC1), NCI-SB-EsC2 (EsC-2), OE19, and OE33 esophageal cancer cells cultured in normal media (NM) with or without cigarette smoke condensate (CSC). Under relevant exposure conditions, CSC significantly decreased miR-217 expression (1.5-9.2 fold) in esophageal cancer cells and Het-1A cells. Endogenous miR-217 expression levels in cultured esophageal cancer cells were significantly lower than those observed in Het-1A cells. Consistent with these findings, miR-217 was significantly down-regulated (3.5-23.5 fold) in resected esophageal cancers relative to adjacent normal esophageal tissues. Software-guided analysis revealed that miR-217 potentially targeted KLK7, encoding a kallikrein family member implicated in invasion and metastasis of several cancers. Constitutive over-expression of miR-217 inhibited expression, whereas depletion of endogenous miR-217 enhanced expression of KLK7 in Het-1A, EsC1 and EsC2 cells. RNA cross-link immunoprecipitation (CLIP) experiments confirmed direct interaction of miR-217 with KLK7 transcripts. Methylated DNA Immunoprecipitation (MeDIP) and chromatin immunoprecipitation (ChIP) experiments demonstrated that CSC increased DNA methylation and decreased H3K4me3 levels within the miR-217 genomic locus in Het-1A, EsC1 and EsC2 cells. Deoxyazacytidine (DAC) induced miR-217 expression in EsC1 and EsC2 cells but not Het-1A cells, and markedly attenuated CSC-mediated miR-217 repression in these cells. Over-expression of miR-217 significantly decreased proliferation of esophageal cancer and Het-1A cells, as well as invasion of esophageal cancer cells. Depletion of miR-217 increased growth of Het-1A cells, but not EsC1 and EsC2 cells presumably due to lower endogenous miR-217 expression in these cancer cells. Experiments are currently in progress to examine the effects of miR-217 and KLK7 expression on tumorigenicity of esophageal cancer cells. Collectively, these data demonstrate that epigenetic repression of miR-217 contributes to the pathogenesis of esophageal carcinomas, and suggest that restoration of miR-217 expression may be a novel strategy for therapy of these malignancies. Citation Format: Sichuan Xi, Suzanne Inchauste, Zuoxiang Xiao, Jigui Shan, Mary Zhang, Julie A. Hong, Manish T Raiji, David G. Beer, David S. Schrump. Epigenetic repression of miR-217 contributes to tobacco-induced esophageal carcinogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3071. doi:10.1158/1538-7445.AM2013-3071 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Chemoprevention of lung cancer: prospects and disappointments in human clinical trials.

Decreasing the risk of lung cancer, or preventing its development in high-risk individuals, would have a huge impact on public health. The most effective means to decrease lung cancer incidence is to eliminate exposure to carcinogens. However, with recent advances in the understanding of pulmonary carcinogenesis and the identification of intermediate biomarkers, the prospects for the field of chemoprevention research have improved dramatically. Here we review the most recent research in lung cancer chemoprevention—focusing on those agents that have been investigated in human clinical trials. These agents fall into three major categories. First, oxidative stress plays an important role in pulmonary carcinogenesis; and therefore, antioxidants (including vitamins, selenium, green tea extracts, and isothiocyanates) may be particularly effective in preventing the development of lung cancer. Second, inflammation is increasingly accepted as a crucial factor in carcinogenesis, and many investigators have focused on anti-inflammatory agents, such as glucocorticoids, NSAIDs, statins, and PPARγ agonists. Finally, the PI3K/AKT/mTOR pathway is recognized to play a central role in tobacco-induced carcinogenesis, and inhibitors of this pathway, including myoinositol and metformin, are promising agents for lung cancer prevention. Successful chemoprevention will likely require targeting of multiple pathways to carcinogenesis—both to minimize toxicity and maximize efficacy.

Aryl Hydrocarbon Receptor-Induced Adrenomedullin Mediates Cigarette Smoke Carcinogenicity in Humans and Mice

Cigarette smoking (CS) is a leading cause of death worldwide. The aryl hydrocarbon receptor (AHR) is partially responsible for tobacco-induced carcinogenesis although the underlying mechanisms involving early effector genes have yet to be determined. Here, we report that adrenomedullin (ADM) significantly contributes to the carcinogenicity of tobacco-activated AHR. CS and AHR activating ligands induced ADM in vitro and in vivo but not in AHR-deficient fibroblasts and mice. Ectopic transfection of AHR rescued ADM expression in AHR(-/-) fibroblasts whereas AHR blockage with siRNA in wild type cells significantly decreased ADM expression. AHR regulates ADM expression through two intronic xenobiotic response elements located close to the start codon in the ADM gene. Using tissue microarrays we showed that ADM and AHR were coupregulated in lung tumor biopsies from smoker patients. Microarray meta-analysis of 304 independent microarray experiments showed that ADM is elevated in smokers and smokers with cancer. In addition, ADM coassociated with a subset of AHR responsive genes and efficiently differentiated patients with lung cancer from nonsmokers. In a novel preclinical model of CS-induced tumor progression, host exposure to CS extracts significantly elevated tumor ADM although systemic treatment with the ADM antagonist NSC16311 efficiently blocked tobacco-induced tumor growth. In conclusion, ADM significantly contributes the carcinogenic effect of AHR and tobacco combustion products. We suggest that therapeutics targeting the AHR/ADM axis may be of clinical relevance in the treatment of tobacco-induced pulmonary malignancies.

Methylation patterns in sentinel genes in peripheral blood cells of heavy smokers: Influence of cruciferous vegetables in an intervention study

Changes in DNA methylation patterns are a hallmark of tobacco-induced carcinogenesis. We have conducted a randomized 4-week intervention trial to investigate the effects of three dietary regimens to modify DNA methylation patterns in peripheral white blood cells of heavy smokers. A group of 88 smokers were randomly assigned to and distributed among three diets, including (1) normal isocaloric diet (balanced in fruits and vegetables), according to international guidelines; (2) a diet enriched in flavonoids and isothiocyanates (particularly cruciferous vegetables); (3) a regimen consisting of diet 1 supplemented with flavonoids (green tea and soy products). Methylation patterns were analyzed by pyrosequencing in LINE1 (Long Interspersed DNA Elements), RASSF1A, ARF and CDKN2a (tumor suppressor genes), MLH1 (mismatch DNA repair) and MTHFR (folate metabolism). Three distinct patterns of methylation were observed. In LINE1, methylation showed a small but reproducible increase with all three regimens. MTHFR was constitutively methylated with no significant modulation by diets. The four other loci showed low basal levels of methylation with no substantial change after intervention. These data suggest that the isocaloric diet may stabilize global epigenetic (LINE1 DNA methylation) patterns in peripheral white blood cells but does not provide evidence for methylation changes in specific genes associated with this short-term dietary intervention.

Cigarette Smoke and Cancer

Cigarette Smoke and Cancer

Abstract 1698: Characterization of the activity and expression of UDP-Glucuronosyltransferase 2A1 variants and potential role in tobacco carcinogenesis

Abstract UDP-glucuronosyltransferases (UGTs) play an important role in the metabolism and excretion of various endogenous and xenobiotic compounds including several carcinogens and chemotherapeutic agents. UGT2A1 is an extra-hepatic member of the UGT2A sub-family that was shown to be expressed in the lung in previous studies. The goal of the present study was to examine UGT2A1 expression in human tissues, assess its glucuronidation activity against exogenous substrates including lung carcinogens, and determine the potential functional role of UGT2A1 polymorphisms on UGT2A1 enzyme activity. Cell homogenates were prepared from HEK293 cells transfected with wild type or variant UGT2A1. Enzyme activity against carcinogens was determined through reverse-phase UPLC. Expression of UGT2A1 was determined by RT-PCR/sequencing, real time PCR (ABI), and western blot using a UGT2A1-specific antibody. In addition to the wild-type UGT2A1*1, two prevalent variants of UGT2A1 were investigated: a variant that causes a lysine to arginine amino acid change at codon 75 (UGT2A1*2), and a variant that causes a glycine to arginine amino acid change at codon 308 (UGT2A1*3). In addition, a newly-identified splice variant isoform lacking exon 3 (allele identified as UGT2A1*1a since it was not yet determined whether this variant was due to a genetic polymorphism or to altered splicing) was also investigated. As determined by RT-PCR and direct sequencing, UGT2A1 was expressed in lung, trachea, larynx, tonsil, mouth, and colon; no expression was observed in breast, whole brain, cerebral cortex or esophageal tissues. Reverse transcription-PCR demonstrated that tissues had variable levels of expression of UGT2A1 and the splice variant encoded by UGT2A1*1a; the UGT2A1*1a encoded variant was expressed in 5 of 6 individual lung specimens and a pooled larynx sample from 10 people. Homogenates of HEK293 cells over-expressing UGT2A1*1 or UGT2A1*2 both exhibited significant activity against 1-naphthol, with a Vmax/KM of 4.0 uL.min−1.ug homogenate protein−1 and 3.5 uL.min−1.ug homogenate protein−1 respectively. No activity was observed for cell homogenates over-expressing the UGT2A1*3 variant or the UGT2A1*1a isoform. A similar pattern of activity was observed for a variety of polycyclic aromatic hydrocarbons (PAHs) including 1-hydroxypyrene, dibenzo(a,l)pyrene-11,12-diol, benzo(a)pyrene-7,8-diol, 5-methylchrysene-1,2-diol, 1-hydroxy (OH)-benzo(a)pyrene, 7-OH-benzo(a)pyrene, and 8-OH-benzo(a)pyrene. No activity was observed against substrates that form N-glucuronides such as NNAL, nicotine or N-OH-PhIP. UGT2A1 is expressed in various target organs for tobacco-induced carcinogenesis and exhibits activity against a variety of PAHs abundant in tobacco smoke. The UGT2A1308Arg variant could play an important role in tobacco-related cancer risk due to a lack of enzyme activity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1698.

A modified host-cell reactivation assay to measure repair of alkylating DNA damage for assessing risk of lung adenocarcinoma

The nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induces lung adenocarcinoma through formation of DNA adducts. Our previous research on susceptibility to tobacco-induced carcinogenesis focused on benzo[a]pyrene diol epoxide (BPDE) as the in vitro mutagen for phenotype measurements of DNA repair capacity (DRC) in mammalian cells. Here, we present a modified host-cell reactivation (HCR) assay to measure lymphocytic DRC for alkylating DNA damage as is induced by the tobacco-specific nitrosamine, NNK. We substituted dimethyl sulfate (DMS) to create alkylating damage in pCMVluc plasmid DNA and established the damage-repair dose-response curves in both normal and nucleotide excision repair-deficient lymphoblastoid cell lines and in phytohemagglutinin (PHA)-stimulated primary lymphocytes. We then successfully measured the DRC in PHA-stimulated lymphocytes from 48 patients with lung adenocarcinoma and 45 cancer-free controls and tested our hypothesis that lower DRC for alkylating damage is associated with an increased risk of lung adenocarcinoma. The cases exhibited a lower mean DRC than did the controls. A >3-fold increased risk (odds ratio = 3.21; 95% confidence interval = 1.25-8.21) was found for those with DRC levels below the control median. There was no correlation between the DRC measured with this DMS-HCR assay and that from the parallel BPDE-HCR assay. Interestingly, risk increased to >10-fold for those with sub-optimal DRC measured by both DMS- and BPDE-HCR assays. We conclude that variability in DRC is a risk factor for lung cancer and our results provide proof of principle for a new assay that can assess DRC for NNK-induced DNA damage.

Estrogen receptor pathways in lung cancer.

Lung cancer is the leading cause of death from neoplasia in men and women in the United States. Some studies suggest that women are more susceptible than men to tobacco-induced carcinogenesis and may show higher risk than men for lung cancer development from smoking. More recently, increasing biochemical and genetic data have supported this male-female difference in response to tobacco. Estrogens may be involved in lung carcinogenesis, and estrogen receptors (ERs), mainly ERb, are present and functional in normal lung and tumor cell lines and tissues. Estrogen can directly stimulate the transcription of estrogen-responsive genes in the nucleus of lung cells, and it can also transactivate growth factor signaling pathways, in particular the epidermal growth factor pathway. Lung cancer patients currently have few effective therapeutic options. An understanding of these new developments in estrogen signaling and cross-talk pathways may pave the way for innovative combinatorial approaches for treatment of lung cancer and possibly chemoprevention.

Mechanisms of smoking-related lung and pancreatic adenocarcinoma development.

Adenocarcinoma of the lungs and pancreas are among the most common and most deadly smoking-associated cancers. Cigarette smoke contains various toxic chemicals, including a carcinogenic nitrosamine, nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). One of the most well-known features of NNK is the ability of its metabolites to bind to DNA and induce activating point mutations in the RAS gene. But NNK is also a β-adrenergic-receptor agonist that stimulates arachidonic acid release, leading to the formation of mitogenic metabolites that stimulate DNA synthesis and cell proliferation. NNK therefore contributes to tobacco-induced carcinogenesis by several mechanisms.

Glutathione-S-transferase polymorphisms and risk of squamous-cell carcinoma of the head and neck.

Differences in genetic susceptibility to tobacco-induced carcinogenesis appear to modulate an individual's risk of squamous-cell carcinoma of the head and neck (SCCHN). Risk for SCCHN may be associated with the null alleles of the carcinogen-metabolizing genes glutathione-S-transferase (GST) T1 and GSTM1. In this study, we evaluated the association between GSTM1 and GSTT1 null genotypes and risk of SCCHN in a matched case-control study of 162 patients with SCCHN and 315 healthy controls. Our results showed that 53.1% of cases and 42.9% of controls were null for GSTM1, whereas 32.7% of cases and 17.5% of controls were null for GSTT1 (p < 0.05 and p < 0.001, respectively). Furthermore, 19.8% of cases but only 7.9% of controls were null for both genes (p < 0.001). Multivariate analysis using logistic regression models, including age, sex, ethnicity, smoking status, alcohol status and GST genotypes, showed that both of these genotypes remained independent risk factors for disease [adjusted odds ratios (ORs) = 1.50 and 2.27, respectively; 95% confidence intervals (CIs) = 1.01-2.23 and 1.43-3.60, respectively). When the genotypes were divided into neither null, either null or both null, there was a dose-response relationship (adjusted OR = 1.50, 95% CI = 0.98-2.30) for the either-null group and (adjusted OR = 3.64, 95% CI = 1.94-6.84) for the both-null group (p < 0.001, trend test). Our findings suggest that the GSTM1 and GSTT1 null genotypes are independent risk factors for SCCHN and markers for genetic susceptibility to tobacco-induced carcinogenesis.

Growth factor-mediated mechanisms of nicotine-dependent carcinogenesis.

The direct effect of nicotine on the expression of receptors for the tumor necrosis factor alpha (TNF alpha) and transforming growth factor beta (TGF beta) and the internalization, intracellular distribution and stability of these growth factors in cervical cancer cell line SiHa was studied. Nicotine at concentrations in the range 0.05-0.25% inhibited cell growth and it exerted strong apoptotic and cytolytic effects at concentrations above 0.5%. Nicotine at 0.1% stabilized and protected from degradation [125I]TNF alpha and [125I]TGF beta internalized by cervical cancer SiHa cell line. In the absence of nicotine, [125I]TNF alpha and [125I]TGF beta were internalized during the first hour of incubation and localized mainly in the cytoplasm and in smaller amounts in the nucleus. After 1 day of cell exposure to growth factors, only traces of radioactivity were detected inside the cells, which indicated that both growth factors were rapidly degraded. In the presence of nicotine, both [125I]TNF alpha and [125I]TGF beta were detected in high quantities and in a non-degraded form in the cytoplasm and chromatin during 5 days of incubation. In addition to the lack of growth factor degradation, the presence of nicotine induced a nuclear accumulation of growth factors, with up to 37% of the internalized [125I]TGF beta being in the chromatin. An increased intracellular accumulation of [125I]TNF alpha and [125I]TGF beta in cells exposed to nicotine occurred without changes in expression of the cell surface receptors. Nuclear accumulation of TGF beta was followed by increased RNA synthesis and a switch from the growth-promoting action of TGF beta to the strong growth inhibitory effect. Inhibition of the lysosomal degradation of growth factors by nicotine is discussed as a potential mechanism of tobacco-induced carcinogenesis.

The genetics of tobacco-induced malignancy.

Several areas of investigation contribute to an increasing understanding of the genetics of malignancies associated with tobacco use. While the strong influence of tobacco exposure on cancer development obscures genetic influences, there are indications that aspects of cancer susceptibility may have a heritable basis. In addition, specific sites within the genome appear to be commonly involved in these malignancies. This review describes research relevant to investigation of the genetics of tobacco-induced malignancy. A review of the pertinent literature covered the past 20 years. References were gleaned from a variety of sources including manual review of the most recent journals, a computerized database (Mini-MEDLINE), references cited in previous works, and our own ongoing research in cancer genetics and molecular biology. Whenever possible, controlled studies from peer-reviewed journals were used. Where studies have shown conflicting results, the possible confounding factors are discussed. From a broad array of research areas, a view of the genetic aspects of tobacco carcinogenesis emerges. This includes syndromic and nonsyndromic susceptibility, genetic determinants of carcinogen metabolism, DNA adduct formation, and site-specific genetic alterations in tobacco-induced malignancy. In addition to specific gene alterations commonly seen in tobacco-induced malignancy, viral infections may contribute to cancer development through pathways related to tobacco carcinogenesis. Further research on many aspects of tobacco-induced carcinogenesis is warranted. Investigation of cancer susceptibility may contribute to understanding DNA surveillance and repair pathways. Carcinogen metabolism investigations have application in cancer detection and prevention schemes. Further understanding of tumor suppressor gene function and the role of gene amplification in carcinogenesis may allow design of gene-specific strategies in cancer treatment.