Urinary levels of cigarette smoke constituent metabolites are prospectively associated with lung cancer development in smokers

Characterization of cigarette smokeomics by in situ solid-phase microextraction and confined-space direct analysis in real time mass spectrometry

Characterization of chemical composition in cigarette smoke is essential for establishing smoke-related exposure estimates. Currently used methods require complex sample preparation with limited capability for obtaining accurate chemical information. We have developed an in situ solid-phase microextraction (SPME) method for online processing of smoke aerosols and directly coupling the SPME probes with confined-space direct analysis in real time (cDART) ion source for high-resolution mass spectrometry (MS) analysis. In a confined space, the substances from SPME probes can be efficiently desorbed and ionized using the DART ion source, and the diffusion and evaporation of volatile species into the open air can be largely avoided. Using SPME-cDART-MS, mainstream smoke (MSS) and side-stream smoke (SSS) can be investigated and the whole analytical protocol can be accomplished in a few min. More than five hundred substances and several classes of compounds were detected and identified. The relative contents of 13 tobacco alkaloids were compared between MSS and SSS. Multivariate data analysis unveiled differences between different types of cigarette smoke and also discovered the characteristic ions. The method is reliable with good reproducibility and repeatability, and has the potential to be quantitative. This study provides a simple and high-efficiency method for smokeomics profiling of complex aerosol samples with in situ online extraction of volatile samples, and direct integration of extracted probes with a modified ambient ionization technique.

Association of Urinary Biomarkers of Tobacco Exposure with Lung Cancer Risk in African American and White Cigarette Smokers in the Southern Community Cohort Study

BACKGROUND

After accounting for smoking history, lung cancer incidence is greater in African Americans than Whites. In the multiethnic cohort, total nicotine equivalents (TNE) are higher in African Americans than Whites at similar reported cigarettes per day. Greater toxicant uptake per cigarette may contribute to the greater lung cancer risk of African Americans.

METHODS

In a nested case-control lung cancer study within the Southern Community Cohort, smoking-related biomarkers were measured in 259 cases and 503 controls (40% White; 56% African American). TNE, the trans-3-hydroxycotinine/cotinine ratio, 4-(methylnitrosamino)-1-3-(pyridyl)-1-butanol (NNAL), mercapturic acid metabolites of volatile organic compounds, phenanthrene metabolites, cadmium (Cd), and (Z)-7-(1R,2R,3R,5S)-3,5-dihydroxy-2-[(E,3S)-3-hydroxyoct-1-enyl]cyclopenyl]hept-5-enoic acid were quantified in urine. Unconditional logistic regression was used to estimate the ORs and 95% confidence intervals (CI) for each biomarker and lung cancer risk.

RESULTS

TNE, NNAL, and Cd were higher in cases than controls (adjusted for age, race, sex, body mass index, and cigarettes per day). Among cases, these levels were higher in African Americans compared with Whites. After accounting for age, sex, body mass index, and pack-years, a one-SD increase in log-TNE (OR = 1.30; 95% CI, 1.10-1.54) and log-NNAL (OR = 1.27; 95% CI, 1.03-1.58 with TNE adjustment) was associated with lung cancer risk. In this study, in which NNAL concentration is relatively high, the association for log-TNE was attenuated after adjustment for log-NNAL.

CONCLUSIONS

Smoking-related biomarkers provide additional information for lung cancer risk in smokers beyond smoking pack-years.

IMPACT

Urinary NNAL, TNE, and Cd concentrations in current smokers, particularly African American smokers, may be useful for predicting lung cancer risk.

Human cancer genomes harbor the mutational signature of tobacco-specific nitrosamines NNN and NNK

Tobacco usage is linked to multiple cancer types and accounts for a quarter of all cancer-related deaths. Tobacco smoke contains various carcinogenic compounds, including polycyclic aromatic hydrocarbons (PAH), though the mutagenic potential of many tobacco-related chemicals remains largely unexplored. In particular, the highly carcinogenic tobacco-specific nitrosamines NNN and NNK form pre-mutagenic pyridyloxobutyl (POB) DNA adducts. In the study presented here, we identified genome-scale POB-induced mutational signatures in cell lines and rat tumors, while also investigating their role in human cancer. These signatures are characterized by T>N and C>T mutations forming from specific POB adducts damaging dT and dC residues. Analysis of 2,780 cancer genomes uncovered POB signatures in ∼180 tumors; from cancer types distinct from the ones linked to smoking-related signatures SBS4 and SBS92. This suggests that, unlike PAH compounds, the POB pathway may contribute uniquely to the mutational landscapes of certain hematological malignancies and cancers of the kidney, breast, prostate and pancreas.

IDSL.GOA: gene ontology analysis for interpreting metabolomic datasets

Biological interpretation of metabolomic datasets often ends at a pathway analysis step to find the over-represented metabolic pathways in the list of statistically significant metabolites. However, definitions of biochemical pathways and metabolite coverage vary among different curated databases, leading to missed interpretations. For the lists of genes, transcripts and proteins, Gene Ontology (GO) terms over-presentation analysis has become a standardized approach for biological interpretation. But, GO analysis has not been achieved for metabolomic datasets. We present a new knowledgebase (KB) and the online tool, Gene Ontology Analysis by the Integrated Data Science Laboratory for Metabolomics and Exposomics (IDSL.GOA) to conduct GO over-representation analysis for a metabolite list. The IDSL.GOA KB covers 2393 metabolic GO terms and associated 3144 genes, 1,492 EC annotations, and 2621 metabolites. IDSL.GOA analysis of a case study of older versus young female brain cortex metabolome highlighted 82 GO terms being significantly overrepresented (FDR < 0.05). We showed how IDSL.GOA identified key and relevant GO metabolic processes that were not yet covered in other pathway databases. Overall, we suggest that interpretation of metabolite lists should not be limited to only pathway maps and can also leverage GO terms as well. IDSL.GOA provides a useful tool for this purpose, allowing for a more comprehensive and accurate analysis of metabolite pathway data. IDSL.GOA tool can be accessed at https://goa.idsl.me/ .

IDSL.GOA: Gene Ontology Analysis for Interpreting Metabolomic datasets

Biological interpretation of metabolomic datasets often ends at a pathway analysis step to find the over-represented metabolic pathways in the list of statistically significant metabolites. However, definitions of biochemical pathways and metabolite coverage vary among different curated databases, leading to missed interpretations. For the lists of genes, transcripts and proteins, Gene Ontology (GO) terms over-presentation analysis has become a standardized approach for biological interpretation. But, GO analysis has not been achieved for metabolomic datasets. We present a new knowledgebase (KB) and the online tool, Gene Ontology Analysis by the Integrated Data Science Laboratory for Metabolomics and Exposomics (IDSL.GOA) to conduct GO over-representation analysis for a metabolite list. The IDSL.GOA KB covers 2,393 metabolic GO terms and associated 3,144 genes, 1,492 EC annotations, and 2,621 metabolites. IDSL.GOA analysis of a case study of older vs young female brain cortex metabolome highlighted 82 GO terms being significantly overrepresented (FDR <0.05). We showed how IDSL.GOA identified key and relevant GO metabolic processes that were not yet covered in other pathway databases. Overall, we suggest that interpretation of metabolite lists should not be limited to only pathway maps and can also leverage GO terms as well. IDSL.GOA provides a useful tool for this purpose, allowing for a more comprehensive and accurate analysis of metabolite pathway data. IDSL.GOA tool can be accessed at https://goa.idsl.me/.

Assessing how lung cancer screening guidelines contribute to racial disparities in screening access

Background

Lung cancer (LC) is the leading cause of cancer-related deaths in the United States (U.S.), with non-White people who smoke often bearing the burden of the highest rate of LC mortality. This is often due to later stage diagnoses, leading to poor prognosis and outcomes. We assess here how the eligibility criteria for LC screening set by the U.S. Preventive Services Task Force (USPSTF) and the Centers for Medicare and Medicaid Services (CMS) could contribute to racial disparities in screening access.

Methods

This paper analyzes data from the National Health and Nutrition Examination Survey (NHANES), an annual survey conducted by the Centers for Disease Control and Prevention (CDC) that gathers health and nutrition data from a representative sample of the U.S. population. After excluding those who were ineligible for LC screening, the final cohort of participants was 5,001, which consisted of 2,669 people who formerly smoked and 2,332 people who currently smoke.

Results

Out of 608 participants who were eligible for LC screening, 77.5% were non-Hispanic White (NHW) and 8.7% were non-Hispanic Black (NHB) participants versus 69.4% and 10.8% among 4,393 ineligible participants. Age, pack-years, and age along with pack-years were the most frequent reasons for ineligibility. LC screening ineligible NHW participants were statistically significantly older and had higher mean pack-years than the other racial and ethnic groups. NHB participants among the ineligible group had higher urinary cotinine levels compared to NHW participants.

Conclusions

This paper underscores the need for more individualized risk estimates when determining eligibility for LC screening, which could include biomarkers of smoking exposure. The analysis shows that current screening criteria, which rely solely on factors such as age and pack years, contribute to LC racial disparities.

Association of Urinary Biomarkers of Smoking-Related Toxicants with Lung Cancer Incidence in Smokers: The Multiethnic Cohort Study

BACKGROUND

While cigarette smoking is the leading cause of lung cancer, the majority of smokers do not develop the disease over their lifetime. The inter-individual differences in risk among smokers may in part be due to variations in exposure to smoking-related toxicants.

METHODS

Using data from a subcohort of 2,309 current smokers at the time of urine collection from the Multiethnic Cohort Study, we prospectively evaluated the association of ten urinary biomarkers of smoking-related toxicants [total nicotine equivalents (TNE), a ratio of total trans-3'-hydroxycotinine (3-HCOT)/cotinine (a phenotypic measure of CYP2A6 enzymatic activity), 4-(methylnitrosamino)-1-3-(pyridyl)-1-butanol (NNAL), S-phenylmercapturic acid (SPMA), 3-hydroxypropyl mercapturic acid (3-HPMA), phenanthrene tetraol (PheT), 3-hydroxyphenanthrene (PheOH), the ratio of PheT/PheOH, cadmium (Cd), and (Z)-7-(1R,2R,3R,5S)-3,5-dihydroxy-2-[(E,3S)-3-hydroxyoct-1-enyl]cyclopenyl]hept-5-enoic acid (8-iso-PGF2α)] with lung cancer risk (n = 140 incident lung cancer cases over an average of 13.4 years of follow-up). Lung cancer risk was estimated using Cox proportional hazards models.

RESULTS

After adjusting for decade of birth, sex, race/ethnicity, body mass index, self-reported pack-years, creatinine, and urinary TNE (a biomarker of internal smoking dose), a one SD increase in log total 3-HCOT/cotinine (HR, 1.33; 95% CI, 1.06-1.66), 3-HPMA (HR, 1.41; 95% CI, 1.07-1.85), and Cd (HR, 1.45; 95% CI, 1.18-1.79) were each associated with increased lung cancer risk.

CONCLUSIONS

Our study demonstrates that urinary total 3-HCOT/cotinine, 3-HPMA, and Cd are positively associated with lung cancer risk. These findings warrant replication and consideration as potential biomarkers for smoking-related lung cancer risk.

IMPACT

These biomarkers may provide additional information on lung cancer risk that is not captured by self-reported smoking history or TNE. See related commentary by Etemadi et al., p. 289.

Characterization of adductomic totality of NNK, (R)-NNAL and (S)-NNAL in A/J mice, and their correlations with distinct lung carcinogenicity

Lung cancer is the leading cause of cancer-related deaths. While tobacco use is the main cause, only 10-20% of smokers eventually develop clinical lung cancer. Thus, the ability of lung cancer risk prediction among smokers could transform lung cancer management with early preventive interventions. Given that DNA damage by tobacco carcinogens is the potential root cause of lung carcinogenesis, we characterized the adductomic totality of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (a potent lung carcinogen in tobacco, commonly known as NNK) in the target lung tissues, the liver tissues and the peripheral serum samples in a single-dose NNK-induced lung carcinogenesis A/J mouse model. We also characterized these adductomic totalities from the two enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL, the major in vivo metabolite of NNK) given their distinct carcinogenicity in A/J mice. With these adductomic data, we demonstrated that tissue protein adductomics have the highest abundance. We also identified that the adductomic levels at the 8 h time point after carcinogen exposure were among the highest. More importantly, the relationships among these adductomics were characterized with overall strong positive linear correlations, demonstrating the potential of using peripheral serum protein adductomics to reflect DNA adductomics in the target lung tissues. Lastly, we explored the relationships of these adductomics with lung tumor status in A/J mice, providing preliminary but promising evidence of the feasibility of lung cancer risk prediction using peripheral adductomic profiling.

OUP accepted manuscript

Our earlier work demonstrated varying potency of dihydromethysticin (DHM) as the active kava phytochemical for prophylaxis of tobacco carcinogen nicotine-derived nitrosamine ketone (NNK)-induced mouse lung carcinogenesis. Efficacy was dependent on timing of DHM gavage ahead of NNK insult. In addition to DNA adducts in the lung tissues mitigated by DHM in a time-dependent manner, our in vivo data strongly implicated the existence of DNA damage-independent mechanism(s) in NNK-induced lung carcinogenesis targeted by DHM to fully exert its anti-initiation efficacy. In the present work, RNA seq transcriptomic profiling of NNK-exposed (2 h) lung tissues with/without a DHM (8 h) pretreatment revealed a snap shot of canonical acute phase tissue damage and stress response signaling pathways as well as an activation of protein kinase A (PKA) pathway induced by NNK and the restraining effects of DHM. The activation of the PKA pathway by NNK active metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) at a concentration incapable of promoting DNA adduct was confirmed in a lung cancer cell culture model, potentially through NNAL binding to and activation of the β-adrenergic receptor. Our in vitro and in vivo data overall support the hypothesis that DHM suppresses PKA activation as a key DNA damage-independent mechanistic lead, contributing to its effective prophylaxis of NNK-induced lung carcinogenesis. Systems biology approaches with a detailed temporal dissection of timing of DHM intake versus NNK exposure are warranted to fill the knowledge gaps concerning the DNA damage-driven mechanisms and DNA damage-independent mechanisms to optimize the implementation strategy for DHM to achieve maximal lung cancer chemoprevention.

Associations of polycyclic aromatic hydrocarbons exposure and its interaction with XRCC1 genetic polymorphism with lung cancer: A case-control study

Humans are extensively exposed to polycyclic aromatic hydrocarbons (PAHs) daily via multiple pathways. Epidemiological studies have demonstrated that occupational exposure to PAHs increases the risk of lung cancer, but related studies in the general population are limited. Hence, we conducted a case-control study among the Chinese general population to investigate the associations between PAHs exposure and lung cancer risk and analyze the modifications of genetic polymorphisms in DNA repair genes. In this study, we enrolled 122 lung cancer cases and 244 healthy controls in Wuhan, China. Urinary PAHs metabolites were determined by gas chromatography-mass spectrometry, and rs25487 in X-ray repair cross-complementation 1 (XRCC1) gene was genotyped by the Agena Bioscience MassARRAY System. Then, multivariable logistic regression models were performed to estimate the potential associations. We found that urinary hydroxynaphthalene (OH-Nap), hydroxyphenanthrene (OH-Phe) and the sum of hydroxy PAHs (∑OH-PAHs) levels were significantly higher in lung cancer cases than those in controls. After adjusting for gender, age, BMI, smoking status, smoking pack-years, drinking status and family history, urinary ∑OH-Nap and ∑OH-Phe levels were positively associated with lung cancer risk, with dose-response relationships. Compared with those in the lowest tertiles, individuals in the highest tertiles of ∑OH-Nap and ∑OH-Phe had a 2.13-fold (95% CI: 1.10, 4.09) and 2.45-fold (95% CI: 1.23, 4.87) increased risk of lung cancer, respectively. Effects of gender, age, smoking status and smoking pack-years on the associations of PAHs exposure with lung cancer risk were shown in the subgroup analysis. Furthermore, associations of urinary ∑OH-Nap and ∑OH-PAHs levels with lung cancer risk were modified by XRCC1 rs25487 (P_interaction ≤ 0.025), and were more pronounced in wild-types of rs25487. These findings suggest that environmental exposure to naphthalene and phenanthrene is associated with increased lung cancer risk, and polymorphism of XRCC1 rs25487 might modify the naphthalene exposure-related lung cancer effect.

Sexual identity differences in biomarkers of tobacco exposure among women in a national sample

BACKGROUND

Sexual minority women are consistently at increased risk for tobacco use compared to heterosexual women. Neither biomarkers of nicotine exposure nor biomarkers of tobacco toxicant exposure have been examined by sexual identity.

METHODS

This study used interview and biomarker data from women in the biomarker core sample of Wave 1 of the Population Assessment of Tobacco and Health (PATH) study (2013-2014; n = 4930). We examined associations of sexual identity with nicotine exposure (measured with urinary cotinine and TNE-2) and with tobacco-specific nitrosamines (measured with urinary NNAL). Multivariable regression modeling was used to examine these associations among the full biomarker core sample, among past 30-day tobacco users, and among exclusive established cigarette users before and after controlling for tobacco use quantity and intensity.

RESULTS

In the full biomarker sample of women, prior to adjusting for tobacco use quantity and intensity, bisexual women had significantly higher cotinine, TNE-2, and NNAL levels compared to heterosexual women. Among exclusive established cigarette users, gay/lesbian women had significantly higher NNAL compared to heterosexual women prior to adjusting for tobacco quantity and intensity. No differences by sexual identity were found after adjusting for tobacco use quantity and intensity.

CONCLUSIONS

This is the first study to demonstrate differences in biological markers of tobacco exposure by sexual identity among women in the U.S. This has important public health implications as greater exposure to both nicotine and to tobacco-specific nitrosamines are strongly linked to cancer risk.

Metabolomic Profiling in Lung Cancer: A Systematic Review

Lung cancer continues to be a significant burden worldwide and remains the leading cause of cancer-associated mortality. Two considerable challenges posed by this disease are the diagnosis of 61% of patients in advanced stages and the reduced five-year survival rate of around 4%. Noninvasively collected samples are gaining significant interest as new areas of knowledge are being sought and opened up. Metabolomics is one of these growing areas. In recent years, the use of metabolomics as a resource for the study of lung cancer has been growing. We conducted a systematic review of the literature from the past 10 years in order to identify some metabolites associated with lung cancer. More than 150 metabolites have been associated with lung cancer-altered metabolism. These were detected in different biological samples by different metabolomic analytical platforms. Some of the published results have been consistent, showing the presence/alteration of specific metabolites. However, there is a clear variability due to lack of a full clinical characterization of patients or standardized patients selection. In addition, few published studies have focused on the added value of the metabolomic profile as a means of predicting treatment response for lung cancer. This review reinforces the need for consistent and systematized studies, which will help make it possible to identify metabolic biomarkers and metabolic pathways responsible for the mechanisms that promote tumor progression, relapse and eventually resistance to therapy.

Associations between Biomarkers of Exposure and Lung Cancer Risk among Exclusive Cigarette Smokers in the Golestan Cohort Study

Biomarkers of tobacco exposure are known to be associated with disease risk but previous studies are limited in number and restricted to certain regions. We conducted a nested case-control study examining baseline levels and subsequent lung cancer incidence among current male exclusive cigarette smokers in the Golestan Cohort Study in Iran. We calculated geometric mean biomarker concentrations for 28 matched cases and 52 controls for the correlation of biomarker levels among controls and for adjusted odds' ratios (ORs) for lung cancer incidence by biomarker concentration, accounting for demographic characteristics, smoking quantity and duration, and opium use. Lung cancer cases had higher average levels of most biomarkers including total nicotine equivalents (TNE-2), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), and 3-hydroxyfluorene (3-FLU). Many biomarkers correlated highly with one another including TNE-2 with NNAL and N-Acetyl-S-(2-cyanoethyl)-L-cysteine (2CYEMA), and N-Acetyl-S-(4-hydroxy-2-buten-1-yl)-L-cysteine (t4HBEMA) with N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-cysteine (3HMPMA) and N-Acetyl-S-(4-hydroxy-2-methyl-2-buten-1-yl)-L-cysteine (4HMBEMA). Lung cancer risk increased with concentration for several biomarkers, including TNE-2 (OR = 2.22, 95% CI = 1.03, 4.78) and NNN (OR = 2.44, 95% CI = 1.13, 5.27), and estimates were significant after further adjustment for demographic and smoking characteristics for 2CYEMA (OR = 2.17, 95% CI = 1.03, 4.55), N-Acetyl-S-(2-carbamoylethyl)-L-cysteine (2CAEMA) (OR = 2.14, 95% CI = 1.01, 4.55), and N-Acetyl-S-(2-hydroxypropyl)-L-cysteine (2HPMA) (OR = 2.85, 95% CI = 1.04, 7.81). Estimates were not significant with adjustment for opium use. Concentrations of many biomarkers were higher at the baseline for participants who subsequently developed lung cancer than among the matched controls. Odds of lung cancer were higher for several biomarkers including with adjustment for smoking exposure for some but not with adjustment for opium use.

Biochemistry of nicotine metabolism and its relevance to lung cancer

Nicotine is the key addictive constituent of tobacco. It is not a carcinogen, but it drives smoking and the continued exposure to the many carcinogens present in tobacco. The investigation into nicotine biotransformation has been ongoing for more than 60 years. The dominant pathway of nicotine metabolism in humans is the formation of cotinine, which occurs in two steps. The first step is cytochrome P450 (P450, CYP) 2A6–catalyzed 5′-oxidation to an iminium ion, and the second step is oxidation of the iminium ion to cotinine. The half-life of nicotine is longer in individuals with low P450 2A6 activity, and smokers with low activity often decrease either the intensity of their smoking or the number of cigarettes they use compared with those with “normal” activity. The effect of P450 2A6 activity on smoking may influence one's tobacco-related disease risk. This review provides an overview of nicotine metabolism and a summary of the use of nicotine metabolite biomarkers to define smoking dose. Some more recent findings, for example, the identification of uridine 5′-diphosphoglucuronosyltransferase 2B10 as the catalyst of nicotine N-glucuronidation, are discussed. We also describe epidemiology studies that establish the contribution of nicotine metabolism and CYP2A6 genotype to lung cancer risk, particularly with respect to specific racial/ethnic groups, such as those with Japanese, African, or European ancestry. We conclude that a model of nicotine metabolism and smoking dose could be combined with other lung cancer risk variables to more accurately identify former smokers at the highest risk of lung cancer and to intervene accordingly.

Relationship Between Urinary 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanol and Lung Cancer Risk in the General Population: A Community-Based Prospective Cohort Study

No published studies have prospectively evaluated the association between urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) levels and lung cancer risk in the general population. Here, we conducted a prospective community-based cohort study in the Republic of Korea to evaluate the relationship between urinary NNAL levels and lung cancer risk using prediagnostic urine samples. This prospective cohort study was based on the Korean National Cancer Center Community Cohort. During the follow-up period, 173 primary lung cancer cases were identified. Total urinary NNAL levels were measured by liquid chromatography-tandem mass spectrometry, and data were analyzed using multivariable Cox proportional hazards regression models. The risk of lung cancer was significantly increased per unit of natural log-transformed urinary NNAL (HR, 1.27; 95% CI, 1.09-1.48), after adjusting for age, region, entry year into the cohort, education achievement, alcohol consumption status, BMI, smoking status, and urinary cotinine levels. Cox proportional-hazards models with NNAL quartiles also showed positive dose-response relationships with risk of lung cancer. A significantly increased risk of lung cancer was found in the fourth quartile of urinary NNAL levels (HR, 3.27; 95% CI, 1.37-7.79, P for trend < 0.01). After stratification with sex, the significant association remained in only men. Urinary NNAL levels are associated with the risk of lung cancer in the general population, and this association is independent from the quantification of cigarette smoking and nicotine uptake.

Tobacco-Specific Nitrosamines (NNAL, NNN, NAT, and NAB) Exposures in the US Population Assessment of Tobacco and Health (PATH) Study Wave 1 (2013-2014)

INTRODUCTION

The tobacco-specific nitrosamines (TSNAs) are an important group of carcinogens found in tobacco and tobacco smoke. To describe and characterize the levels of TSNAs in the Population Assessment of Tobacco and Health (PATH) Study Wave 1 (2013-2014), we present four biomarkers of TSNA exposure: N'-nitrosonornicotine, N'-nitrosoanabasine, N'-nitrosoanatabine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) which is the primary urinary metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

METHODS

We measured total TSNAs in 11 522 adults who provided urine using automated solid-phase extraction coupled to isotope dilution liquid chromatography-tandem mass spectrometry. After exclusions in this current analysis, we selected 11 004 NNAL results, 10 753 N'-nitrosonornicotine results, 10 919 N'-nitrosoanatabine results, and 10 996 N'-nitrosoanabasine results for data analysis. Geometric means and correlations were calculated using SAS and SUDAAN.

RESULTS

TSNA concentrations were associated with choice of tobacco product and frequency of use. Among established, every day, exclusive tobacco product users, the geometric mean urinary NNAL concentration was highest for smokeless tobacco users (993.3; 95% confidence interval [CI: 839.2, 1147.3] ng/g creatinine), followed by all types of combustible tobacco product users (285.4; 95% CI: [267.9, 303.0] ng/g creatinine), poly tobacco users (278.6; 95% CI: [254.9, 302.2] ng/g creatinine), and e-cigarette product users (6.3; 95% CI: [4.7, 7.9] ng/g creatinine). TSNA concentrations were higher in every day users than in intermittent users for all the tobacco product groups. Among single product users, exposure to TSNAs differed by sex, age, race/ethnicity, and education. Urinary TSNAs and nicotine metabolite biomarkers were also highly correlated.

CONCLUSIONS

We have provided PATH Study estimates of TSNA exposure among US adult users of a variety of tobacco products. These data can inform future tobacco product and human exposure evaluations and related regulatory activities.

Syngeneic tobacco carcinogen-induced mouse lung adenocarcinoma model exhibits PD-L1 expression and high tumor mutational burden

Human lung adenocarcinoma (LUAD) in current or former smokers exhibits a high tumor mutational burden (TMB) and distinct mutational signatures. Syngeneic mouse models of clinically relevant smoking-related LUAD are lacking. We established and characterized a tobacco-associated, transplantable murine LUAD cell line, designated FVBW-17, from a LUAD induced by the tobacco carcinogen 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone in the FVB/N mouse strain. Whole-exome sequencing of FVBW-17 cells identified tobacco-associated KrasG12D and Trp53 mutations and a similar mutation profile to that of classic alkylating agents with a TMB greater than 500. FVBW-17 cells transplanted subcutaneously, via tail vein, and orthotopically generated tumors that were histologically similar to human LUAD in FVB/N mice. FVBW-17 tumors expressed programmed death ligand 1 (PD-L1), were infiltrated with CD8+ T cells, and were responsive to anti-PD-L1 therapy. FVBW-17 cells were also engineered to express green fluorescent protein and luciferase to facilitate detection and quantification of tumor growth. Distant metastases to lung, spleen, liver, and kidney were observed from subcutaneously transplanted tumors. This potentially novel cell line is a robust representation of human smoking-related LUAD biology and provides a much needed preclinical model in which to test promising new agents and combinations, including immune-based therapies.

Can the Public Be Educated About Constituents in Smokeless Tobacco? A Three-Wave Randomized Controlled Trial

INTRODUCTION

The U.S. Food and Drug Administration (FDA) is required by law to inform the public about levels of harmful and potentially harmful tobacco constituents in a format that is "understandable and not misleading to a lay person." Our study addresses a critical gap in research on communicating such information for smokeless tobacco (SLT) products.

METHODS

The design included random assignment to one of the experimental (online interactive) conditions differing in presentation format or a control condition (receiving no information). Experimental respondents viewed information on levels and health risks of 5 harmful constituents in up to 79 products. Outcome measures included knowledge of health risks of constituents, perception of constituent variability in SLT products, disease risk ratings, self-reported SLT use, and side-by-side product comparisons. The sample of 333 SLT users, 535 cigarette smokers, and 663 nontobacco users participated at baseline, time of intervention, and 6 weeks postintervention.

RESULTS

Presentation formats showed few systematic differences so were combined in analyses. Experimental condition respondents increased their knowledge about constituent health effects and their perceptions of constituent variability in SLT products, from baseline to postintervention, and relative to the control condition. Changes in respondents' ratings of disease risk and their estimates of constituent exposure from specific products were observed, but not in self-reported SLT use.

CONCLUSIONS

Interactive online graphic and numeric presentation formats can be efficient in increasing people's knowledge of health effects and perceived variation of constituents in SLT products. Further research on longer-term behavioral assessment, and usefulness of this approach for regulatory agencies, is needed.

IMPLICATIONS

Research on communicating the information about harmful constituents in SLT products to lay persons is critically lacking. This study proposes novel formats for effective communication about the levels and the health effects of SLT constituents to multiple user groups. The lack of misperceptions among study participants that some tobacco products are safe suggests that such formats can potentially be used for public display of SLT constituent data by the FDA and regulatory agencies in other countries.

Comparing cotinine and NNAL verification of self-reported smoking status among lung cancer screening eligible population from the 2007-2014 National Health and Nutrition Examination Survey (NHANES)

Background: Biochemical verification of self-reported smoking status is not common among the population eligible for lung cancer screening (LCS). Methods: We used urinary NNAL (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides) and serum cotinine as the gold standard to determine the validity and reliability of self-reported smoking status from the 2007-2014 National Health and Nutrition Examination Survey (NHANES). Results: We found 2.3% (n = 652, equivalent to 5.3 million weighted population) of adults eligible for LCS according to the current United States Preventive Services Task Force guideline. Self-reported current smoking status performed similarly against NNAL and cotinine: sensitivity [89.7% (95%CI: 84.9%-94.5%) vs. 89.5% (95%CI: 84.8%-94.3%)]; specificity [99.7% (95%CI: 99.2%-100.0%) vs. 100% (95%CI:100%-100%)]; positive predictive value (PPV) and negative predictive value (NPV) were 99.8% (95%CI:99.4%-100.0%) versus 100% (95%CI:100%-100%) and 85.3% (95%CI: 79.1%-91.5%) versus 85.1% (95%CI: 79.1%-1.0%), respectively; and Kappa [86.5% (95%CI:80.5%-92.5%) vs. 86.5% (95%CI:80.6%-92.3%)]. Performance measures were better among females than males; worst among the non-Hispanic white and best among other race/ethnicity group. The validity and reliability of self-reported smoking status increased with increasing cutpoint levels of both NNAL and cotinine. Conclusions: Self-reported smoking status among people who are at high risk of lung cancer is reasonably reliable. The difference between using NNAL and cotinine appears to be minimal.

Urinary Biomarkers and Their Potential for the Non-Invasive Detection of Endometrial Cancer

Endometrial cancer is the most common malignancy of the female genital tract and its incidence is rising in parallel with the mounting prevalence of obesity. Early diagnosis has great potential to improve outcomes as treatment can be curative, especially for early stage disease. Current tests and procedures for diagnosis are limited by insufficient accuracy in some and unacceptable levels of invasiveness and discomfort in others. There has, therefore, been a growing interest in the search for sensitive and specific biomarkers for endometrial cancer detection based on non-invasive sampling methodologies. Urine, the prototype non-invasive sample, is attractive for biomarker discovery as it is easily accessible and can be collected repeatedly and in quantity. Identification of urinary biomarkers for endometrial cancer detection relies on the excretion of systemic biomarkers by the kidneys or urinary contamination by biomarkers shed from the uterus. In this review, we present the current standing of the search for endometrial cancer urinary biomarkers based on cytology, genomic, transcriptomic, proteomic, and metabolomic platforms. We summarize the biomarker candidates and highlight the challenges inherent in urinary biomarker discovery. We review the various technologies with promise for biomarker detection and assess these novel approaches for endometrial cancer biomarker research.

Applying Tobacco, Environmental, and Dietary-Related Biomarkers to Understand Cancer Etiology and Evaluate Prevention Strategies

Many human cancers are caused by environmental and lifestyle factors. Biomarkers of exposure and risk developed by our team have provided critical data on internal exposure to toxic and genotoxic chemicals and their connection to cancer in humans. This review highlights our research using biomarkers to identify key factors influencing cancer risk as well as their application to assess the effectiveness of exposure intervention and chemoprevention protocols. The use of these biomarkers to understand individual susceptibility to the harmful effects of tobacco products is a powerful example of the value of this type of research and has provided key data confirming the link between tobacco smoke exposure and cancer risk. Furthermore, this information has led to policy changes that have reduced tobacco use and consequently, the tobacco-related cancer burden. Recent technological advances in mass spectrometry led to the ability to detect DNA damage in human tissues as well as the development of adductomic approaches. These new methods allowed for the detection of DNA adducts in tissues from patients with cancer, providing key evidence that exposure to carcinogens leads to DNA damage in the target tissue. These advances will provide valuable insights into the etiologic causes of cancer that are not tobacco-related.See all articles in this CEBP Focus section, "Environmental Carcinogenesis: Pathways to Prevention."

A review of the analysis of biomarkers of exposure to tobacco and vaping products

Quantification of exposure to different chemicals from both combustible cigarettes and vaping products is important in providing information on the potential health risks of these products. To assess the exposure to tobacco products, biomarkers of exposure (BOEs) are measured in a variety of biological matrices. In this review paper, current knowledge on analytical methods applied to the analysis of biomarkers of exposure to tobacco products is discussed. Numerous sample preparation techniques are available for the extraction and sample clean up for the analysis of BOEs to tobacco and nicotine delivery products. Many tobacco products-related exposure biomarkers have been analyzed using different instrumental techniques, the most common techniques being gas and liquid chromatography coupled with mass spectrometry (GC-MS, GC-MS/MS and LC-MS/MS). To assess exposure to emerging tobacco products and study exposure in dual tobacco users, the list of biomarkers analyzed in urine samples has been expanded. Therefore, the current state of the literature can be used in preparing a preferred list of biomarkers based on the aim of each study. The information summarized in this review is expected to be a handy tool for researchers involved in studying exposures to tobacco products, as well as in risk assessment of biomarkers of exposure to vaping products.

Association between Metabolites and the Risk of Lung Cancer: A Systematic Literature Review and Meta-Analysis of Observational Studies

Globally, lung cancer is the most prevalent cancer type. However, screening and early detection is challenging. Previous studies have identified metabolites as promising lung cancer biomarkers. This systematic literature review and meta-analysis aimed to identify metabolites associated with lung cancer risk in observational studies. The literature search was performed in PubMed and EMBASE databases, up to 31 December 2019, for observational studies on the association between metabolites and lung cancer risk. Heterogeneity was assessed using the I2 statistic and Cochran's Q test. Meta-analyses were performed using either a fixed-effects or random-effects model, depending on study heterogeneity. Fifty-three studies with 297 metabolites were included. Most identified metabolites (252 metabolites) were reported in individual studies. Meta-analyses were conducted on 45 metabolites. Five metabolites (cotinine, creatinine riboside, N-acetylneuraminic acid, proline and r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene) and five metabolite groups (total 3-hydroxycotinine, total cotinine, total nicotine, total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (sum of concentrations of the metabolite and its glucuronides), and total nicotine equivalent (sum of total 3-hydroxycotinine, total cotinine and total nicotine)) were associated with higher lung cancer risk, while three others (folate, methionine and tryptophan) were associated with lower lung cancer risk. Significant heterogeneity was detected across most studies. These significant metabolites should be further evaluated as potential biomarkers for lung cancer.

Counseling alone or in combination with nicotine replacement therapy for treatment of black non-daily smokers: a randomized trial

BACKGROUND AND AIMS

One-third of US tobacco users are non-daily smokers (NDS). Black NDS have strikingly high levels of nicotine and carcinogen exposure. No smoking cessation studies have been conducted with this high-risk group. This study compared the effectiveness in black NDS of smoking cessation counseling alone or in combination with the participant's choice of nicotine replacement therapy.

DESIGN

Two-arm parallel-group individually randomized clinical trial (allocation ratio of 2 : 1 intervention to control) SETTING: Academic medical and federally qualified health centers in three US cities.

PARTICIPANTS

Non-Hispanic black adult NDS receiving counseling with nicotine replacement therapy (C + NRT, n = 185) or counseling alone (C, n = 93).

INTERVENTIONS

Twelve weeks of in-person and telephone smoking cessation counseling in combination with nicotine replacement therapy (NRT; C + NRT) or counseling alone (C). All participants received five sessions of counseling; those randomized to C + NRT received their choice of nicotine gum, patch and/or lozenge after a 9-day product trial period. The target quit day was set at 2 weeks post-baseline for both groups.

MEASUREMENTS

Primary outcome was biochemically verified 30-day abstinence at week 12. Secondary outcomes were change in nicotine and carcinogen exposure [4-(methynitrosamino)-1-(3) pyridyle-1-butanol; NNAL] and tobacco consumption patterns.

FINDINGS

Abstinence was 11.4% in C + NRT and 8.6% in C [odds ratio (OR) = 1.4, 95% confidence interval (CI) = 0.6, 3.2, P = 0.48]. Both groups experienced significant reduction in NNAL (C + NRT: 53% reduction, C: 50% reduction, within-group P < 0.0001) but non-significant changes in cotinine (P = 0.69). C + NRT reported more days abstinent (P < 0.001) and fewer total cigarettes (P = 0.002) compared with C. There was no evidence of compensation with other tobacco products.

CONCLUSIONS

Among black non-daily smokers in the United States, there was no difference in abstinence between nicotine replacement therapy (NRT) and counseling alone. NRT led to greater increase in days abstinent and reduction in cigarettes, with no evidence of compensation from other sources of nicotine.

Objective secondhand smoke exposure in chronic obstructive pulmonary disease patients without active smoking: the U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2012

Background

Secondhand smoke (SHS) may be related to worse outcomes in chronic obstructive pulmonary disease (COPD), but the reported SHS prevalence in different studies varied from 27% to 65% and the effects of SHS are still questionable among these patients. The study aims were to estimate the objective SHS prevalence and explore the SHS impact on outcomes among COPD patients without active smoking.

Methods

A cross-sectional design combined with longitudinal death outcome. We selected COPD patients over 40 years old based on the spirometry from National Health and Nutrition Examination Survey (2007–2012), and used the tobacco-specific biomarkers [cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanonol] to determine exposure statuses (active smoking, SHS exposure, or no smoke exposure). Then we estimated the short-term (past 2–4 days) and medium-term (past 6–12 weeks) SHS prevalence among 334 patients without active smoking. Weighted multiple regressions were performed to assess the associations between medium-term SHS exposure and outcomes (symptoms, health status, medical institution visits, and death).

Results

Among the patients without active smoking, the objective prevalence rates of short-term and medium-term SHS were 66.65% [95% confidence interval (CI), 59.63–73.67%] and 34.91% (95% CI, 28.86%–40.96%), respectively. Medium-term SHS exposure showed a significant effect (odds ratio, 3.57; 95% CI, 1.22–10.40) on more chronic coughing after adjusting for the covariates and indicated a trend of unadjusted increasing death risk (log-rank test, P=0.01).

Conclusions

Among COPD patients without active smoking, both short-term and medium-term SHS exposure are prevalent. Chronic cough may be the most susceptible patient-centred outcome related to medium-term SHS exposure. The crude longitudinal trend of elevated death risk associated with medium-term SHS exposure deserves further study.

The Impact of One-week Dietary Supplementation with Kava on Biomarkers of Tobacco Use and Nitrosamine-based Carcinogenesis Risk among Active Smokers

Tobacco smoking is the primary risk factor for lung cancer, driven by the addictive nature of nicotine and the indisputable carcinogenicity of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) as well as other compounds. The integration of lung cancer chemoprevention with smoking cessation is one potential approach to reduce this risk and mitigate lung cancer mortality. Experimental data from our group suggest that kava, commonly consumed in the South Pacific Islands as a beverage to promote relaxation, may reduce lung cancer risk by enhancing NNK detoxification and reducing NNK-derived DNA damage. Building upon these observations, we conducted a pilot clinical trial to evaluate the effects of a 7-day course of kava on NNK metabolism in active smokers. The primary objective was to compare urinary total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL plus its glucuronides, major metabolites of NNK) before and after kava administration as an indicator of NNK detoxification. Secondary objectives included determining kava's safety, its effects on DNA damage, tobacco use, and cortisol (a biomarker of stress). Kava increased urinary excretion of total NNAL and reduced urinary 3-methyladenine in participants, suggestive of its ability to reduce the carcinogenicity of NNK. Kava also reduced urinary total nicotine equivalents, indicative of its potential to facilitate tobacco cessation. Plasma cortisol and urinary total cortisol equivalents were reduced upon kava use, which may contribute to reductions in tobacco use. These results demonstrate the potential of kava intake to reduce lung cancer risk among smokers.

Biomarkers of Potential Harm: Summary of an FDA-Sponsored Public Workshop

Introduction

Since 2009, the United States (US) Food and Drug Administration (FDA) Center for Tobacco Products (CTP) has had the authority to regulate the manufacture, distribution, and marketing of tobacco products in order to reduce the death and disease caused by tobacco use. Biomarkers could play an important role across a number of FDA regulatory activities, including assessing new and modified risk tobacco products and identifying and evaluating potential product standards.

Methods

On April 4-5, 2016, FDA/CTP hosted a public workshop focused on biomarkers of potential harm (BOPH) with participants from government, industry, academia, and other organizations. The workshop was divided into five sessions focused on: (1) overview of BOPH; (2) cardiovascular disease (CVD); (3) chronic obstructive pulmonary disease (COPD); (4) cancer; and (5) new areas of research.

Results and Conclusions

The deliberations from the workshop noted some promising BOPH but also highlighted the lack of systematic effort to identify BOPH that would have utility and validity for evaluating tobacco products. Research areas that could further strengthen the applicability of BOPH to tobacco regulatory science include the exploration of composite biomarkers as predictors of disease risk, "omics" biomarkers, and examining biomarkers using existing cohorts, surveys, and experimental studies.

Implications

This paper synthesizes the main findings from the 2016 FDA-sponsored workshop focused on BOPH and highlights research areas that could further strengthen the science around BOPH and their applicability to tobacco regulatory science.

Urinary Cotinine Is as Good a Biomarker as Serum Cotinine for Cigarette Smoking Exposure and Lung Cancer Risk Prediction

BACKGROUND

Cotinine is a metabolite of nicotine. Serum and urinary cotinine are validated biomarkers for cigarette exposure. Their performance for lung cancer risk prediction has not been simultaneously examined in epidemiologic studies.

METHODS

A nested case-control study, including 452 incident lung cancer cases and 452 smoking-matched controls in the Shanghai cohort study, was conducted. Mass spectrometry-based methods were used to quantify cotinine in serum and urine samples collected from current smokers at baseline, on average 10 years before cancer diagnosis of cases. Logistic regression was used to estimate ORs, 95% confidence intervals (CI), and AUC ROC for lung cancer associated with higher levels of cotinine.

RESULTS

Serum and urinary cotinine levels were significantly higher in lung cancer cases than controls. Compared with the lowest quartile serum cotinine (≤0.40 nmol/mL), the OR of lung cancer for smokers in the highest quartiles (>1.39 nmol/mL) was 5.46 (95% CI, 3.38-8.81). Similarly, the OR was 5.49 (95% CI, 3.39-8.87) for highest (>16.38 nmol/mg creatinine) relative to the lowest quartile of urinary total cotinine (≤4.11 nmol/mg creatinine). A risk prediction model yielded an AUC of 0.72 (95% CI, 0.69-0.75) for serum cotinine and 0.72 (95% CI, 0.69-0.75) for urinary total cotinine combined with smoking history.

CONCLUSIONS

Urinary and serum cotinine have the same performance in prediction of lung cancer risk for current smokers.

IMPACT

Urinary cotinine is a noninvasive biomarker that can replace serum cotinine in risk prediction of future lung cancer risk for current smokers.

Biomarkers of Exposure and Potential Harm among Natural American Spirit Smokers

OBJECTIVES

We compared biomarkers of exposure and potential harm in smokers of American Spirit (AS) to smokers of Marlboro, Newport, Camel, and Pall Mall.

METHODS

We conducted secondary analysis on: (1) data from a randomized clinical trial (RCT); and (2) the Population Assessment of Tobacco Use and Health (PATH) Study. Biomarkers analyzed included: total nicotine equivalents (TNE); 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL); N'-nitrosonornicotine and its N-glucuronide (total NNN);3-hydroxypropylmercapturic acid(3-HPMA); 2-hydroxypropylmercapturic acid (2-HPMA), 3-hydroxy-1 methylpropylmercapturic acid (HMPMA); S-phenylmercapturic acid(SPMA); 2-cyanoethylmercapturic acid (CEMA); phenanthrene tetraol(PheT);1-hydroxypyrene (1-HOP);8-iso-PGF2α; white blood count(WBC); prostaglandin E metabolite(PGEM); and high sensitivity C-reactive protein(hsCRP).

RESULTS

AS smokers did not differ in TNE but had higher TNE per cigarette compared to other brands. Total NNAL, total NNN, CEMA, and 3-HPMA were lower in AS smokers. All other biomarkers were no different in AS smokers compared to all or the majority of the other brands.

CONCLUSIONS

Levels of total NNAL, total NNN, acrylonitrile, and acrolein were reduced in AS smokers; however, it is not known whether reductions in exposure to these toxicants contribute to reduced harm. Higher TNE per cigarette smoked in AS smokers suggests a greater addictive potential compared to other brands. Regulatory action to ensure that consumers are not misled about the risks of the AS brand are recommended.

Comparison of TSNAs concentration in saliva according to type of tobacco smoked

OBJECTIVE

To compare tobacco-specific nitrosamines (TSNAs) measured in saliva according to different types of tobacco smoked in a sample of smokers of the city of Barcelona (Spain).

METHODS

We used data from a cross-sectional study of a sample of the adult smoking population of Barcelona, Spain in 2013-2014 (n = 165). We classified smokers in five groups according to the type of tobacco smoked: a) manufactured cigarettes only, b) roll-your-own (RYO) cigarettes only, c) dual smokers (both manufactured and RYO cigarettes), d) manufactured plus other types of tobacco products different from RYO and e) other types of tobacco products different from manufactured and RYO cigarettes. We calculated the geometric mean (GM) and geometric standard deviation (GSD) of TSNAs concentration in saliva (pg/mL), including N'-nitroaonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) according to the five tobacco groups. We also described all TSNAs concentration in each tobacco group stratified by the number of cigarettes smoked per day.

RESULTS

Smokers from the RYO cigarette group had higher TSNAs concentration than smokers from the manufactured cigarette group: 13 pg/mL vs 4.9 pg/mL of NNN, 1.9 pg/mL vs 1.7 pg/mL in NNK and 1.1 pg/mL vs 0.9 pg/mL of NNAL. There were significant differences in NNN concentrations between smokers of RYO vs manufactured cigarettes. The higher the number of cigarettes smoked, the higher the TSNAs concentrations. After adjusted by number of cigarettes smoked, there were not statistically significant differences in TSNAs between RYO and manufactured cigarettes.

CONCLUSIONS

Our data shows that RYO cigarette is at least as hazardous as manufactured cigarettes. Regulating RYO tobacco prices could be an effective strategy to control tobacco use.

Circulating cotinine concentrations and lung cancer risk in the Lung Cancer Cohort Consortium (LC3)

Background

Self-reported smoking is the principal measure used to assess lung cancer risk in epidemiological studies. We evaluated if circulating cotinine-a nicotine metabolite and biomarker of recent tobacco exposure-provides additional information on lung cancer risk.

Methods

The study was conducted in the Lung Cancer Cohort Consortium (LC3) involving 20 prospective cohort studies. Pre-diagnostic serum cotinine concentrations were measured in one laboratory on 5364 lung cancer cases and 5364 individually matched controls. We used conditional logistic regression to evaluate the association between circulating cotinine and lung cancer, and assessed if cotinine provided additional risk-discriminative information compared with self-reported smoking (smoking status, smoking intensity, smoking duration), using receiver-operating characteristic (ROC) curve analysis.

Results

We observed a strong positive association between cotinine and lung cancer risk for current smokers [odds ratio (OR ) per 500 nmol/L increase in cotinine (OR500): 1.39, 95% confidence interval (CI): 1.32-1.47]. Cotinine concentrations consistent with active smoking (≥115 nmol/L) were common in former smokers (cases: 14.6%; controls: 9.2%) and rare in never smokers (cases: 2.7%; controls: 0.8%). Former and never smokers with cotinine concentrations indicative of active smoking (≥115 nmol/L) also showed increased lung cancer risk. For current smokers, the risk-discriminative performance of cotinine combined with self-reported smoking (AUCintegrated: 0.69, 95% CI: 0.68-0.71) yielded a small improvement over self-reported smoking alone (AUCsmoke: 0.66, 95% CI: 0.64-0.68) (P = 1.5x10-9).

Conclusions

Circulating cotinine concentrations are consistently associated with lung cancer risk for current smokers and provide additional risk-discriminative information compared with self-report smoking alone.

Relationship of the oxidative damage biomarker 8-epi-prostaglandin F2α to risk of lung cancer development in the Shanghai Cohort Study

It has been hypothesized that the pathogenesis of lung cancer induced by cigarette smoking involves oxidative damage by free radicals. Epidemiological data on biomarkers of oxidative damage and risk of lung cancer development are sparse. A nested case-control study of 610 lung cancer cases and 610 matched controls was conducted within a prospective cohort of 18 244 Chinese men in Shanghai, China. The concentrations of 8-epi-prostaglandin F2α (8-epiPGF2α), a biomarker of oxidative stress, were determined in baseline urine samples using a validated mass-spectrometry assay. Current smokers had significantly higher level of 8-epiPGF2α than former smokers or never smokers (P < 0.001). 8-epiPGF2α levels were significantly higher in lung cancer cases than their smoking-matched controls in former and current smokers, but not different in never smokers (P for interaction = 0.019). The relative risks of developing lung cancer for former and current smokers in the highest relative to the lowest quartile of 8-epiPGF2α were 5.25 (Ptrend = 0.035) and 1.99 (Ptrend =0.007), respectively. The effect of 8-epiPGF2α and biomarkers of cigarette smoke exposure on lung cancer risk was additive; the relative risk was 5.33 (95% confidence interval = 2.65-7.51) for current smokers with the highest thirds of 8-epiPGF2α and total cotinine compared with their lowest thirds. Smokers with a heightened state of oxidative stress in response to the insults of cigarette smoking may be more susceptible to smoking-induced lung carcinogenesis.

A review of metabolism-associated biomarkers in lung cancer diagnosis and treatment

INTRODUCTION

Lung cancer continues to be the leading cause of cancer-related mortality worldwide. Early detection has proven essential to extend survival. Genomic and proteomic advances have provided impetus to the effort dedicated to detect and diagnose the disease at an earlier stage. Recently, the study of metabolites associated with tumor formation and progression has inaugurated the era of cancer metabolomics to aid in this effort.

OBJECTIVES

This review summarizes recent work regarding novel metabolites with the potential to serve as biomarkers for early lung tumor detection, evaluation of disease progression, and prediction of patient outcomes.

METHOD

We compare the metabolite profiling of cancer patients with that of healthy individuals, and the metabolites identified in tissue and biofluid samples and their usefulness as lung cancer biomarkers. We discuss metabolite alterations in tumor versus paired non-tumor lung tissues, as well as metabolite alterations in different stages of lung cancers and their usefulness as indicators of disease progression and overall survival. We evaluate metabolite dysregulation in different types of lung cancers, and those associated with lung cancer versus other lung diseases. We also examine metabolite differences between lung cancer patients and smokers/risk-factor individuals.

RESULT

Although an extensive list of metabolites has been evaluated to distinguish between these cases, refinement of methods is further required for adequate patient diagnosis.

CONCLUSION

We conclude that with technological advancement, metabolomics may be able to replace more invasive and costly diagnostic procedures while also providing the means to more effectively tailor treatment to patient-specific tumors.

Mechanisms of toxicity and biomarkers of flavoring and flavor enhancing chemicals in emerging tobacco and non-tobacco products

Tobacco products containing flavorings, such as electronic nicotine delivery devices (ENDS) or e-cigarettes, cigars/cigarillos, waterpipes, and heat-not-burn devices (iQOS) are continuously evolving. In addition to increasing the exposure of teenagers and adults to nicotine containing flavoring products and flavoring enhancers, chances of nicotine addiction through chronic use and abuse also increase. These flavorings are believed to be safe for ingestion, but little information is available about their effects on the lungs. In this review, we have discussed the in vitro and in vivo data on toxicity of flavoring chemicals in lung cells. We have further discussed the common flavoring agents, such as diacetyl and menthol, currently available detection methods, and the toxicological mechanisms associated with oxidative stress, inflammation, mucociliary clearance, and DNA damage in cells, mice, and humans. Finally, we present potential biomarkers that could be utilized for future risk assessment. This review provides crucial parameters important for evaluation of risk associated with flavoring agents and flavoring enhancers used in tobacco products and ENDS. Future studies can be designed to address the potential toxicity of inhaled flavorings and their biomarkers in users as well as in chronic exposure studies.

Analysis and Identification of 2'-Deoxyadenosine-Derived Adducts in Lung and Liver DNA of F-344 Rats Treated with the Tobacco-Specific Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone and Enantiomers of its Metabolite 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are carcinogenic in animal models and are believed to play an important role in human lung carcinogenesis for cigarette smokers. Cytochrome P450-mediated metabolism of these tobacco-specific nitrosamines produces reactive species that alkylate DNA in the form of pyridyloxobutyl (POB)- or pyridylhydroxybutyl (PHB)-DNA adducts. Understanding the formation mechanism and overall levels of these adducts can potentially enhance cancer prevention methods through the identification of particularly susceptible smokers. Previous studies have identified and measured a panel of POB- and PHB-DNA base adducts of dGuo, dCyd, and Thd; however, dAdo adducts have yet to be determined. In this study, we complete this DNA adduct panel by identifying and quantifying levels of NNK- and NNAL-derived dAdo adducts in vitro and in vivo. To accomplish this, we synthesized standards for expected dAdo-derived DNA adducts and used isotope-dilution LC-ESI⁺-MS/MS to identify POB adducts formed in vitro from the reaction of 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone (NNKOAc) with calf thymus DNA. Adduct levels were then quantified in lung and liver DNA of rats chronically treated with NNK or NNAL for 50 weeks using similar LC-MS detection methods. The in vitro studies identified N⁶-POB-dAdo and N¹-POB-dIno as products of the reaction of NNKOAc with DNA, which supports our proposed mechanism of formation. Though both N⁶-dAdo and N¹-dIno adducts were found in vitro, only N⁶-dAdo adducts were found in vivo, implying possible intervention by DNA repair mechanisms. Analogous to previous studies, levels of N⁶-POB-dAdo and N⁶-PHB-dAdo varied both with tissue and treatment type. Despite the adduct levels being relatively modest compared to most other POB- and PHB-DNA adducts, they may play a biological role and could be used in future studies as NNK- and NNAL-specific DNA damage biomarkers.

Identification of new tetrahydroxylated metabolites of Polycyclic Aromatic Hydrocarbons in hair as biomarkers of exposure and signature of DNA adduct levels

The present study addresses the hypothesis that the concentration of tetrahydroxylated Polycylic Aromatic Hydrocarbons (tetra-OH-PAHs) in hair might be a useful biomarker of human exposure to PAHs, providing quantitative assessment of the internal dose, as well as information on the associated toxicity in relation to individual's specific metabolism. By means of animal models, this work aimed at identifying new tetra-OH-PAHs which can be released from the hydrolysis of DNA-adducts and can also be directly detected in biological matrices usually used in the field of biomonitoring such as hair and urine. Results obtained from a targeted gas chromatography coupled with tandem mass spectrometry (GC-MS/MS) approach, demonstrated the presence of 8 tetrahydroxylated metabolites in DNA and 23 in hairs of rats exposed to mixtures of PAHs, which had never been analyzed before. Ten tetra-OH-PAHs were clearly characterized by using their analytical standards, corresponding to 4 parent PAHs (phenanthrene, chrysene, benz[a]anthracene and benzo[a]pyrene) whereas 13 tetra-OH-PAHs from 3 other parents (anthracene, fluoranthene and benz[k]fluoranthene) were detected but not yet characterized. No tetrahydroxylated metabolite has been clearly identified for naphthalene, fluorene, benzo[b]fluoranthene, benzo[g,h,i]perylene, or dibenzo[a,h]anthracene, which can all potentially form adducts. The relevance of tetra-OH-PAH analysis in hair as biomarkers of PAH exposure was evaluated in a dose-response study conducted on 64 rats (Long Evans females/n = 8 per groups) under repeated exposure (3 times per week) to a mixture of 16 PAHs at low doses (0.01-0.8 mg/kg) for 90 days. Most of the tetra-OH-PAHs targeted in the method were detected in the hairs of the rats, regardless of the dose of exposure. Significant linear relationships (R² ranging from 0.558 to 0.964, p < 0.001) were observed between the administered dose and the tetra-OH-PAH concentrations in the hairs for 20 out of the 23 metabolites. By widening the range of PAH metabolites used as biomarkers of exposure so as to include the analysis of PAH tetrahydroxylated forms (especially those exhibiting more than 5 aromatic rings), the present methodology will enable multi-exposure assessments which are more accurately representative of actual situations of exposure to PAHs.

Tobacco toxicant exposure in cigarette smokers who use or do not use other tobacco products

BACKGROUND

Non-cigarette other tobacco products (OTP; e.g., cigarillos, little cigars) are typically used in combination with cigarettes, but limited data exists on the tobacco toxicant exposure profiles of dual cigarette-OTP (Cig-OTP) users. This study examined biomarkers of nicotine and carcinogen exposure in cigarette smokers who used or did not use OTP.

METHODS

111 Cig-OTP and 111 cigarette only (Cig Only) users who smoked equivalent cigarettes per day were matched on age (< 40, >=40), race (African American, White), and gender. Participants reported past 7-day daily use of cigarettes and OTP and provided urine for nicotine, cotinine, total nicotine equivalents (TNE) and total NNAL concentrations.

RESULTS

Cig-OTP users reported greater past 7-day tobacco use (15.9 versus 13.0 products/day, p<0.01) but had significantly lower creatinine-normalized nicotine (606 versus 1301ng/mg), cotinine (1063 versus 2125ng/mg), TNE (28 versus 57 nmol/mg) and NNAL (251 versus 343pg/mg) than Cig Only users (p<0.001).

CONCLUSIONS

Cig-OTP users had lower levels of nicotine and metabolites of a lung carcinogen relative to Cig-Only users, but concentrations of toxicants among Cig-OTP users were still at levels that place smokers at great risk from the detrimental health effects of smoking.

IMPACT

Our study finds that nicotine and carcinogen exposure in Cig-OTP users are lower compared to cigarette only users, but still likely to be associated with substantial harm. A better understanding of why toxicant levels may be lower in Cig-OTP is an important area for future study.

Cigarette Filter Ventilation and its Relationship to Increasing Rates of Lung Adenocarcinoma

The 2014 Surgeon General's Report on smoking and health concluded that changing cigarette designs have caused an increase in lung adenocarcinomas, implicating cigarette filter ventilation that lowers smoking machine tar yields. The Food and Drug Administration (FDA) now has the authority to regulate cigarette design if doing so would improve public health. To support a potential regulatory action, two weight-of-evidence reviews were applied for causally relating filter ventilation to lung adenocarcinoma. Published scientific literature (3284 citations) and internal tobacco company documents contributed to causation analysis evidence blocks and the identification of research gaps. Filter ventilation was adopted in the mid-1960s and was initially equated with making a cigarette safer. Since then, lung adenocarcinoma rates paradoxically increased relative to other lung cancer subtypes. Filter ventilation 1) alters tobacco combustion, increasing smoke toxicants; 2) allows for elasticity of use so that smokers inhale more smoke to maintain their nicotine intake; and 3) causes a false perception of lower health risk from "lighter" smoke. Seemingly not supportive of a causal relationship is that human exposure biomarker studies indicate no reduction in exposure, but these do not measure exposure in the lung or utilize known biomarkers of harm. Altered puffing and inhalation may make smoke available to lung cells prone to adenocarcinomas. The analysis strongly suggests that filter ventilation has contributed to the rise in lung adenocarcinomas among smokers. Thus, the FDA should consider regulating its use, up to and including a ban. Herein, we propose a research agenda to support such an effort.

Performance of urine cotinine and hypomethylation of AHRR and F2RL3 as biomarkers for smoking exposure in a population-based cohort

There is a growing body of evidence demonstrating an association between smoking and DNA methylation. Accordingly, DNA methylation is now considered a promising biomarker of smoking exposure. We evaluated the relationship between methylation markers (AHRR and F2RL3) and urine cotinine as well as self-reported smoking status. DNA methylation levels of AHRR and F2RL3 in blood as well as urine cotinine were measured in 330 adults (46 to 87 years of age). Pyrosequencing was performed to measure DNA methylation of AHRR and F2RL3 associated with smoking exposure. The lung cancer risk associated with DNA methylation and urine cotinine was analyzed using logistic regression analysis. The AHRR and F2RL3 genes were significantly hypomethylated in current smokers compared to in individuals who have never smoked. An inverse relationship was observed between urine cotinine and methylation levels. Methylation of AHRR and F2RL3 distinguished current smokers from never-smokers with high accuracy. Logistic multivariate analysis showed that AHRR methylation is significantly associated with the risk of lung cancer (OR = 0.96, P = 0.011). Our study validated the smoking-associated DNA methylation markers reported in a Korean population-based cohort. In conclusion, DNA methylation of AHRR and F2RL3 provided accurate measures for smoking exposure. Methylation markers reflecting the long-term effect of smoking on the risk of lung cancer showed better performance in distinguishing former smokers from never-smokers.

CYP2A6 genetic polymorphisms and biomarkers of tobacco smoke constituents in relation to risk of lung cancer in the Singapore Chinese Health Study

Cytochrome P450 2A6 (CYP2A6) catalyzes the metabolism of nicotine and the tobacco-specific lung carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Genetic variation in CYP2A6 may affect smoking behavior and contribute to lung cancer risk. A nested case-control study of 197 lung cancer cases and 197 matched controls was conducted within a prospective cohort of 63 257 Chinese men and women in Singapore. Quantified were five genetic variants of CYP2A6 (*1A, *4, *7, *9 and *12) and urinary metabolites of nicotine [total nicotine, total cotinine, total trans-3'-hydroxycotinine (3HC)] and NNK (total NNAL, free NNAL, NNAL-glucuronide, NNAL-N-glucuronide, and NNAL-O-glucuronide). Higher urinary metabolites of nicotine and NNK were significantly associated with a 2- to 3-fold increased risk of lung cancer after adjustment for smoking intensity and duration. Lower CYP2A6-determined nicotine metabolizer status was significantly associated with a lower ratio of total 3HC over total cotinine, lower total nicotine equivalent and reduced risk of developing lung cancer (all Ptrend < 0.001). Compared with normal metabolizers, odds ratios (95% confidence intervals) of developing lung cancer for intermediate, slow and poor metabolizers determined by CYP2A6 genotypes were 0.85 (0.41-1.77), 0.55 (0.28-1.08) and 0.32 (0.15-0.70), respectively, after adjustment for smoking intensity and duration and urinary total nicotine equivalents. Thus the reduced risk of lung cancer in smokers with lower CYP2A6 activity may be explained by lower consumption of cigarettes, less intense smoking and reduced CYP2A6-catalyzed activation of the tobacco-specific lung carcinogen NNK.

Context Matters: Contribution of Specific DNA Adducts to the Genotoxic Properties of the Tobacco-Specific Nitrosamine NNK

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent pulmonary carcinogen in laboratory animals. It is classified as a Group 1 human carcinogen by the International Agency for Cancer Research. NNK is bioactivated upon cytochrome P450 catalyzed hydroxylation of the carbon atoms adjacent to the nitrosamino group to both methylating and pyridyloxobutylating agents. Both pathways generate a spectrum of DNA damage that contributes to the overall mutagenic and toxic properties of this compound. NNK is also reduced to form 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which is also carcinogenic. Like NNK, NNAL requires metabolic activation to DNA alkylating agents. Methyl hydroxylation of NNAL generates pyridylhydroxybutyl DNA adducts, and methylene hydroxylation leads to DNA methyl adducts. The consequence of this complex metabolism is that NNK generates a vast spectrum of DNA damage, any form of which can contribute to the overall carcinogenic properties of this potent pulmonary carcinogen. This Perspective reviews the chemistry and genotoxic properties of the collection of DNA adducts formed from NNK. In addition, it provides evidence that multiple adducts contribute to the overall carcinogenic properties of this chemical. The adduct that contributes to the genotoxic effects of NNK depends on the context, such as the relative amounts of each DNA alkylating pathway occurring in the model system, the levels and genetic variants of key repair enzymes, and the gene targeted for mutation.

Oral Cell DNA Adducts as Potential Biomarkers for Lung Cancer Susceptibility in Cigarette Smokers

This perspective considers the use of oral cell DNA adducts, together with exposure and genetic information, to potentially identify those cigarette smokers at highest risk for lung cancer, so that appropriate preventive measures could be initiated at a relatively young age before too much damage has been done. There are now well established and validated analytical methods for the quantitation of urinary and serum metabolites of tobacco smoke toxicants and carcinogens. These metabolites provide a profile of exposure and in some cases lung cancer risk, but they do not yield information on the critical DNA damage parameter that leads to mutations in cancer growth control genes such as KRAS and TP53. Studies demonstrate a correlation between changes in the oral cavity and lung in cigarette smokers, due to the field effect of tobacco smoke. Oral cell DNA is readily obtained in contrast to DNA samples from the lung. Studies in which oral cell DNA and salivary DNA have been analyzed for specific DNA adducts are reviewed; some of the adducts identified have also been previously reported in lung DNA from smokers. The multiple challenges of developing a panel of oral cell DNA adducts that could be routinely quantified by mass spectrometry are discussed.

Context Matters: Contribution of Specific DNA Adducts to the Genotoxic Properties of the Tobacco-Specific Nitrosamine NNK

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent pulmonary carcinogen in laboratory animals. It is classified as a Group 1 human carcinogen by the International Agency for Cancer Research. NNK is bioactivated upon cytochrome P450 catalyzed hydroxylation of the carbon atoms adjacent to the nitrosamino group to both methylating and pyridyloxobutylating agents. Both pathways generate a spectrum of DNA damage that contributes to the overall mutagenic and toxic properties of this compound. NNK is also reduced to form 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which is also carcinogenic. Like NNK, NNAL requires metabolic activation to DNA alkylating agents. Methyl hydroxylation of NNAL generates pyridylhydroxybutyl DNA adducts, and methylene hydroxylation leads to DNA methyl adducts. The consequence of this complex metabolism is that NNK generates a vast spectrum of DNA damage, any form of which can contribute to the overall carcinogenic properties of this potent pulmonary carcinogen. This Perspective reviews the chemistry and genotoxic properties of the collection of DNA adducts formed from NNK. In addition, it provides evidence that multiple adducts contribute to the overall carcinogenic properties of this chemical. The adduct that contributes to the genotoxic effects of NNK depends on the context, such as the relative amounts of each DNA alkylating pathway occurring in the model system, the levels and genetic variants of key repair enzymes, and the gene targeted for mutation.

Biomarkers of Tobacco Exposure: Summary of an FDA-Sponsored Public Workshop

Since 2009, the FDA Center for Tobacco Products (CTP) has had the authority to regulate the manufacturing, distribution, and marketing of tobacco products in order to reduce the death and disease caused by tobacco use. Biomarkers of exposure pertain to actual human exposure to chemicals arising from tobacco use and could play an important role across a number of FDA regulatory activities, including assessing new and modified-risk tobacco products and identifying and evaluating potential product standards. On August 3-4, 2015, FDA/CTP hosted a public workshop focused on biomarkers of exposure with participants from government, industry, academia, and other organizations. The workshop was divided into four sessions focused on: (i) approaches to evaluating and selecting biomarkers; (ii) biomarkers of exposure and relationship to disease risk; (iii) currently used biomarkers of exposure and biomarkers in development; and (iv) biomarkers of exposure and the assessment of smokeless tobacco and electronic nicotine delivery systems. This article synthesizes the main findings from the workshop and highlights research areas that could further strengthen the science around biomarkers of exposure and help determine their application in tobacco product regulation. Cancer Epidemiol Biomarkers Prev; 26(3); 291-302. ©2016 AACR.

Tobacco-specific N-nitrosamines and polycyclic aromatic hydrocarbons in cigarettes smoked by the participants of the Shanghai Cohort Study

Our recent studies on tobacco smoke carcinogen and toxicant biomarkers and cancer risk among male smokers in the Shanghai Cohort Study showed that exposure to tobacco-specific nitrosamines (TSNA) and polycyclic aromatic hydrocarbons (PAH) is prospectively associated with the risk of cancer. These findings support the hypothesis that the smokers' cancer risk is a function of the dose of select tobacco carcinogens and highlight the importance of understanding the factors that affect the intake of these carcinogens by smokers. Given that tobacco constituent exposures are driven, at least in part, by the levels of these constituents in cigarette smoke, we measured mainstream smoke TSNA and PAH levels in 43 Chinese cigarette brands that participants of the Shanghai Cohort Study reported to smoke. In all brands analyzed here, mainstream smoke levels of NNN and NNK, the two carcinogenic TSNA, were generally relatively low, averaging (±SD) 16.8(±25.1) and 14.2(±9.5) ng/cigarette, respectively. The levels of PAH were comparable to those found in U.S. cigarettes, averaging 15(±9) ng/cigarette for benzo[a]pyrene, 119(±66) ng/cigarette for phenanthrene and 37(±19) ng/cigarette for pyrene. Our findings indicate that the generally low levels of NNN and NNK are most likely responsible for the relatively low levels of the corresponding biomarkers in the urine of the Shanghai Cohort Study participants as compared to those found in the U.S. smokers, supporting the role of the levels of these constituents in cigarette smoke in smokers' exposures. Our findings also suggest that, in addition to smoking, other sources contribute to Chinese smokers' exposure to PAH.

Genetic determinants of cytochrome P450 2A6 activity and biomarkers of tobacco smoke exposure in relation to risk of lung cancer development in the Shanghai cohort study

Cytochrome P450 2A6 (CYP2A6) catalyzes nicotine metabolism and contributes to the metabolism of the tobacco-specific lung carcinogen, NNK. Genetic variation in CYP2A6 may affect smoking behavior and contribute to lung cancer risk. A nested case-control study of 325 lung cancer cases and 356 controls was conducted within a prospective cohort of 18,244 Chinese men in Shanghai, China. Quantified were 4 allelic variants of CYP2A6 [*1(+51A), *4, *7, and *9] and urinary total nicotine, total cotinine, total trans-3'-hydroxycotinine (3HC) and total NNAL (an NNK metabolite). Calculated were total nicotine equivalents (TNE), the sum of total nicotine, total cotinine and total 3HC and the total 3HC:total cotinine ratio as a measure of CYP2A6 activity. The nicotine metabolizer status (normal, intermediate, slow and poor) was determined by CYP2A6 genotypes. The smoking-adjusted odds ratios (95% confidence intervals) of lung cancer for the highest vs lowest quartile of total nicotine, total cotinine, total 3HC, TNE and total NNAL were 3.03 (1.80-5.10), 4.70 (2.61-8.46), 4.26 (2.37-7.68), 4.71 (2.61-8.52), and 3.15 (1.86-5.33) (all Ptrend  < 0.001), respectively. Among controls CYP2A6 poor metabolizers had a 78% lower total 3HC:total cotinine ratio and 72% higher total nicotine (Ptrend ≤ 0.002). Poor metabolizers had an odds ratio of 0.64 (95% confidence interval = 0.43-0.97) for lung cancer, which was statistically nonsignificant (odds ratio = 0.74, 95% confidence interval = 0.48-1.15) after adjustment for urinary TNE and smoking intensity and duration. The lower lung cancer risk observed in CYP2A6 poor metabolizers is partially explained by the strong influence of CYP2A6 genetic polymorphisms on nicotine uptake and metabolism.

Analysis of Tobacco-Specific Nitrosamines in the Common Smokeless Tobacco Afzal in Oman

OBJECTIVES

There is a lack of awareness regarding the carcinogenicity of Afzal, an illegal smokeless tobacco product (STP) widely used among the Omani youth. Previous research has shown that certain types of tobacco-specific nitrosamines (TSNAs) are associated with oral and lung cancers. This study therefore aimed to assess levels of four common TSNAs in a randomly selected sample of Afzal.

METHODS

This study was carried out at Sultan Qaboos University in Muscat, Oman, between April and September 2013. A random sample of Afzal was analysed for four types of TSNAs using high-performance liquid chromatography-tandem mass spectrometry. The four types of TSNAs analysed were 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), N-nitrosoanatabine (NAT) and N-nitrosoanabasine (NAB). As a reference product, a sample of laboratory-manufactured American moist snuff (Centers for Disease Control and Prevention, Atlanta, Georgia, USA) was also used to confirm the accuracy and precision of the analysis.

RESULTS

The analysis revealed total TSNA levels of 3.573 μg/g in the Afzal sample. Mean levels of NNN, NNK, NAT and NAB were 1.205, 1.015, 0.809 and 0.545 μg/g, respectively.

CONCLUSION

Levels of the two most abundant TSNAs (NNN and NNK) found in the Afzal sample exceeded international regulatory limits. Afzal users therefore need to be educated regarding the potential health risks associated with their STP use. Stricter implementation of current legislation is recommended to reduce the availability and usage of Afzal in Oman.