Progress and challenges in selected areas of tobacco carcinogenesis

Role of Insulin-like Growth Factor-1 Receptor in Tobacco Smoking-Associated Lung Cancer Development

Cancer remains a significant global health concern, with lung cancer consistently leading as one of the most common malignancies. Genetic aberrations involving receptor tyrosine kinases (RTKs) are known to be associated with cancer initiation and development, but RTK involvement in smoking-associated lung cancer cases is not well understood. The Insulin-like Growth Factor 1 Receptor (IGF-1R) is a receptor that plays a critical role in lung cancer development. Its signaling pathway affects the growth and survival of cancer cells, and high expression is linked to poor prognosis and resistance to treatment. Several reports have shown that by activating IGF-1R, tobacco smoke-related carcinogens promote lung cancer and chemotherapy resistance. However, the relationship between IGF-1R and cancer is complex and can vary depending on the type of cancer. Ongoing investigations are focused on developing therapeutic strategies to target IGF-1R and overcome chemotherapy resistance. Overall, this review explores the intricate connections between tobacco smoke-specific carcinogens and the IGF-1R pathway in lung carcinogenesis. This review further highlights the challenges in using IGF-1R inhibitors as targeted therapy for lung cancer due to structural similarities with insulin receptors. Overcoming these obstacles may require a comprehensive approach combining IGF-1R inhibition with other selective agents for successful cancer treatment.

Impact of smoking status on health-related quality of life (HRQoL) in cancer survivors

Introduction

The Health-Related Quality of Life (HRQoL) often declines among cancer survivors due to many factors. Some cancer patients who smoke before the cancer diagnosis continue this harmful habit, potentially contributing to a more significant decline in their HRQoL. Therefore, this study investigates the association between smoking status and HRQoL in cancer survivors.

Methods

We conducted a cross-sectional study utilizing self-reported cancer history from 39,578 participants of the Behavioral Risk Factor Surveillance System (BRFSS) database, leveraging 2016 and 2020 year questionaries. A multidimensional composite outcome was created to assess HRQoL, integrating four distinct dimensions - general health, mental health, physical health, and activity limitations. After accounting for the complex survey design, logistic regression models were used to analyze the association between smoking status and poor HRQoL, adjusting for demographic, socioeconomic, and health-related confounders.

Results

Our study found that, after adjusting for potential confounders, current smokers exhibited a significantly poorer HRQoL than never smokers (OR 1.65, 95%CI 1.40-1.93). Furthermore, former smokers showed a poorer HRQoL than never smokers; however, this association was not as strong as current smokers (OR 1.22, 95%CI 1.09-1.38).

Conclusion

Our findings highlight the adverse association of smoking with poor HRQoL in cancer survivors, underscoring the importance of healthcare professionals prioritizing smoking cessation and providing tailored interventions to support this goal.

Development of lung cancer risk prediction models based on F-18 FDG PET images

OBJECTIVE

We aimed to evaluate whether the degree of F-18 fluorodeoxyglucose (FDG) uptake in the lungs is associated with an increased risk of lung cancer and to develop lung cancer risk prediction models using metabolic parameters on F-18 FDG positron emission tomography (PET).

METHODS

We retrospectively included 795 healthy individuals who underwent F-18 FDG PET/CT scans for a health check-up. Individuals who developed lung cancer within 5 years of the PET/CT scan were classified into the lung cancer group (n = 136); those who did not were classified into the control group (n = 659). The healthy individuals were then randomly assigned to either the training (n = 585) or validation sets (n = 210). Clinical factors including age, sex, body mass index (BMI), and smoking history were collected. The standardized uptake value ratio (SUVR) and metabolic heterogeneity (MH) index were obtained for the bilateral lungs. Logistic regression models including clinical factors, SUVR, and MH index were generated to quantify the probability of lung cancer development using a training set. The prediction models were validated using a validation set.

RESULTS

The lung SUVR and lung MH index in the lung cancer group were significantly higher than in the control group (p < 0.001 and p < 0.001, respectively). In the combined prediction model 1, age, sex, BMI, smoking history, and lung SUVR were significantly associated with lung cancer development (age: OR 1.07, p < 0.001; male: OR 2.08, p = 0.015; BMI: OR 0.93, p = 0.057; current or past smoker: OR 5.60, p < 0.001; lung SUVR: OR 1.13, p < 0.001). In the combined prediction model 2, age, sex, BMI, smoking history, and lung MH index showed a significant association with lung cancer development (age: OR 1.06, p < 0.001; male: OR 1.87, p = 0.045; BMI: OR 0.93, p = 0.010; current or past smoker: OR 4.78, p < 0.001; lung MH index: OR 1.33, p < 0.001). In the validation data, combined prediction models 1 and 2 exhibited very good discrimination [area under the receiver operator curve (AUC): 0.867 and 0.901, respectively].

CONCLUSIONS

The metabolic parameters on F-18 FDG PET are related to an increased risk of lung cancer. Metabolic parameters can be used as biomarkers to provide information independent of the clinical parameters, related to lung cancer risk.

In Utero and Childhood/Adolescence Exposure to Tobacco Smoke, Genetic Risk, and Cancer Incidence in Adulthood: A Prospective Cohort Study

OBJECTIVE

To evaluate the association of early-life tobacco smoke exposure, especially interacting with cancer genetic variants, with adult cancer.

PARTICIPANTS AND METHODS

We examined the associations of in utero tobacco smoke exposure, age of smoking initiation, and their interaction with genetic risk levels with cancer incidence in 393,081 participants from the UK Biobank. Information on tobacco exposure was obtained by self-reported questionnaires. A cancer polygenic risk score was constructed by weighting and integrating 702 genome-wide association studies-identified risk variants. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) for overall cancer and organ-specific cancer incidence.

RESULTS

During 11.8 years of follow-up, 23,450 (5.97%) and 23,413 (6.03%) incident cancers were included in the analyses of in utero exposure and age of smoking initiation, respectively. The HR (95% CI) for incident cancer in participants with in utero exposure to tobacco smoke was 1.04 (1.01-1.07) for overall cancer, 1.59 (1.44-1.75) for respiratory cancer, and 1.09 (1.03-1.17) for gastrointestinal cancer. The relative risk of incident cancer increased with earlier smoking initiation (Ptrend<.001), with the HR (95% CI) of 1.44 (1.36-1.51) for overall cancer, 13.28 (11.39-15.48) for respiratory cancer, and 1.72 (1.54-1.91) for gastrointestinal cancer in smokers with initiation in childhood compared with never smokers. Importantly, a positive additive interaction between age of smoking initiation and genetic risk was observed for overall cancer (Padditive=.04) and respiratory cancer (Padditive=.003) incidence.

CONCLUSION

In utero exposure and earlier smoking initiation are associated with overall and organ-specific cancer, and age of smoking initiation interaction with genetic risk is associated with respiratory cancer.

DNA Alkylation Damage by Nitrosamines and Relevant DNA Repair Pathways

Nitrosamines occur widespread in food, drinking water, cosmetics, as well as tobacco smoke and can arise endogenously. More recently, nitrosamines have been detected as impurities in various drugs. This is of particular concern as nitrosamines are alkylating agents that are genotoxic and carcinogenic. We first summarize the current knowledge on the different sources and chemical nature of alkylating agents with a focus on relevant nitrosamines. Subsequently, we present the major DNA alkylation adducts induced by nitrosamines upon their metabolic activation by CYP450 monooxygenases. We then describe the DNA repair pathways engaged by the various DNA alkylation adducts, which include base excision repair, direct damage reversal by MGMT and ALKBH, as well as nucleotide excision repair. Their roles in the protection against the genotoxic and carcinogenic effects of nitrosamines are highlighted. Finally, we address DNA translesion synthesis as a DNA damage tolerance mechanism relevant to DNA alkylation adducts.

Dual inhibition of EGFR‑VEGF: An effective approach to the treatment of advanced non‑small cell lung cancer with EGFR mutation (Review)

On a global scale, the incidence and mortality rates of lung cancer are gradually increasing year by year. A number of bad habits and environmental factors are associated with lung cancer, including smoking, second‑hand smoke exposure, occupational exposure, respiratory diseases and genetics. At present, low‑dose spiral computed tomography is routinely the first choice in the diagnosis of lung cancer. However, pathological examination is still the gold standard for the diagnosis of lung cancer. Based on the classification and stage of the cancer, treatment options such as surgery, radiotherapy, chemotherapy, targeted therapy and immunotherapy are available. The activation of the EGFR pathway can promote the survival and proliferation of tumor cells, and the VEGF pathway can promote the formation of blood vessels, thereby promoting tumor growth. In non‑small cell lung cancer (NSCLC) with EGFR mutation, EGFR activation can promote tumor growth by promoting VEGF upregulation through a hypoxia‑independent mechanism. The upregulation of VEGF can make tumor cells resistant to EGFR inhibitors. In addition, the expression of the VEGF signal is also affected by other factors. Therefore, the use of a single EGFR inhibitor cannot completely inhibit the expression of the VEGF signal. In order to overcome this problem, the combination of VEGF inhibitors and EGFR inhibitors has become the method of choice. Dual inhibition can not only overcome the resistance of tumor cells to EGFR inhibitors, but also significantly increase the progression‑free survival time of patients with NSCLC. The present review discusses the associations between the EGFR and VEGF pathways, and the characteristics of dual inhibition of the EGFR‑VEGF pathway.

Dual NGS Comparative Analysis of Liquid Biopsy (LB) and Formalin-Fixed Paraffin-Embedded (FFPE) Samples of Non-Small Cell Lung Carcinoma (NSCLC)

Lung cancer ranks second worldwide after breast cancer and third in Europe after breast and colorectal cancers when both sexes and all ages are considered. In this context, the aim of this study was to emphasize the power of dual analysis of the molecular profile both in tumor tissue and plasma by NGS assay as a liquid biopsy approach with impact on prognosis and therapy modulation in NSCLC patients. NGS analysis was performed both from tissue biopsies and from cfNAs isolated from peripheral blood samples. Out of all 29 different mutations detectable by both NGS panels (plasma and tumor tissue), seven different variants (24.13%; EGFR L858R in two patients, KRAS G13D and Q61H and TP53 G244D, V197M, R213P, and R273H) were detected only in plasma and not in the tumor itself. These mutations were detected in seven different patients, two of them having known distant organ metastasis. Our data show that NGS analysis of cfDNA could identify actionable mutations in advanced NSCLC and, therefore, this analysis could be used to monitor the disease progression and the treatment response and even to modulate the therapy in real time.

Comparison of Carcinogen Biomarkers in Smokers of Menthol and Nonmenthol Cigarettes: The 2015-2016 National Health and Nutrition Examination Survey Special Sample

BACKGROUND

The US FDA announced its commitment to prohibiting menthol as a characterizing flavor in tobacco. The relationship between cigarette menthol and exposure to toxic substances in mainstream tobacco smoke is not well characterized.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) 2015 to 2016 special sample were used to study markers of 26 harmful and potentially harmful constituents (HPHC) in tobacco smoke. These include urine metabolites of polycyclic aromatic hydrocarbons (PAH), volatile organic compounds (VOC), and heavy metals in exclusive menthol (n = 162) and nonmenthol (n = 189) cigarette smokers. Urine metabolites of 7 PAHs, 15 VOCs, and 4 heavy metal biomarkers were compared by menthol status. Multivariable analyses were conducted on creatinine-adjusted concentrations.

RESULTS

There were no significant differences in cotinine levels or in 22 of 26 HPHCs. Among the urine metabolites of PAHs, the levels of 1-hydroxyphenanthrene were about 16% lower in menthol smokers. Among the urine metabolites of VOCs, menthol cigarette smokers presented significantly lower concentrations of acrylamide, N,N-dimethylformamide, and acrylonitrile. Menthol and nonmenthol smokers presented similar levels of heavy metals. Menthol did not affect the levels of cotinine and the nicotine metabolite ratio in urine.

CONCLUSIONS

Menthol and nonmenthol cigarettes deliver similar levels of most HPHCs.

IMPACT

Findings on toxicity are similar for menthol and nonmenthol cigarettes.

Maternal steroids during pregnancy and their associations with ambient air pollution and temperature during preconception and early gestational periods

Hormones play critical roles in facilitating pregnancy progression and the onset of parturition. Several classes of environmental contaminants, including fine particulate matter (PM_2.5) and ambient temperature, have been shown to alter hormone biosynthesis or activity. However, epidemiologic research has not considered PM_2.5 in relation to a broader range of steroid hormones, particularly in pregnant women. Using metabolomics data collected within 20-40 weeks of gestation in an ethnically diverse pregnancy cohort study, we identified 42 steroid hormones that we grouped into five classes (pregnenolone, androgens, estrogens, progestin, and corticosteroids) based on their biosynthesis type. We found that exposure to PM_2.5 during the pre-conception and early prenatal periods was associated with higher maternal androgen concentrations in late pregnancy. We also detected a positive association between early pregnancy PM_2.5 exposure and maternal pregnenolone levels and a marginal positive association between early pregnancy PM_2.5 exposure and progestin levels. When considering each hormone metabolite individually, we found positive associations between early pregnancy PM_2.5 exposure and five steroids, two of which survived multiple comparison testing: 11beta-hydroxyandrosterone glucuronide (a pregnenolone steroid) and adrosteroneglucuronide (a progestin steroid). None of the steroid classes were statistically significant associated with ambient temperature. In sex-stratified analyses, we did not detect any sex differences in our associations. This is the first study showing that exposure to fine particulate matter during the pre-conception and early prenatal periods can lead to altered steroid adaptation during the state of pregnancy, which has been shown to have potential consequences on maternal and child health.

Structure-based study to identify alkaloids as promising cytochrome P450 (CYP1A1) inhibitors: An in silico approach using virtual screening, molecular dynamic simulations, and binding free energy calculation

Carcinogens present in smokeless tobacco (SLT) like tobacco-specific nitrosamines can be metabolized by the cytochrome P450 (CYP450) enzyme. Functionally, the CYP450 enzyme resides in a heme pigment to perform the catalytic activity. The CYP1A1 is one of the main extrahepatic CYP450 enzymes known to detoxify toxic substances and activate carcinogens. The CYP1A1 inhibition by potential inhibitors reduce the chance of oral cancer. The current study aimed to explore more about the inhibitor binding site and identification of lead alkaloids, that could work as putative inhibitors against target CYP1A1. In respect, we have performed docking studies, virtual screening of alkaloids, and natural product libraries against CYP1A1 followed by molecular dynamic simulations and binding free energy calculations. Docking studies of tobacco-specific nitrosamine (TSNA) products and their similar carcinogen analogs revealed that the heme group is bound to the floor of the bowl-shaped cavity whereas carcinogens are bound to the roof of the rounded shape cavity. Furthermore, virtual screening and binding free energy calculations revealed Tomatidine as a putative inhibitor against CYP1A1. On the basis of altogether outcomes of the current study, we have concluded that the addition of lead-hit alkaloid Tomatidine and others in SLT products may be working as a supplement that could be able to reduce the expression of human CYP1A1 and suppresses carcinogenic by-products formations.

Identification of Cigarette Smoking-Related Novel Biomarkers in Lung Adenocarcinoma

Objective

The aims of this study were to screen the gene mutations that are able to predict the risk of cigarette smoking-related lung adenocarcinoma (LUAD) and to evaluate its prognostic significance.

Methods

Clinical data and genetic information were retrieved from the TCGA database, and the patients with LUAD were divided into three groups including never smoking, light smoking, and heavy smoking according to cigarette smoking dose. Differentially mutated genes (DMGs) of each group were analyzed. At the same time, the function of DMGs in three smoking groups was evaluated by GO function and KEGG pathway analysis. The driver genes and protein variation effect of DMGs were performed to further screen key genes. The survival characteristics of the gene expression and mutation of those genes were analyzed and plotted to visualize by the Kaplan-Meier model.

Result

The DMGs for different smoking doses were identified. The driver and deleterious mutation in the DMGs were screened and gene interaction network was constructed. The DMGs with driver mutations and deleterious mutations that were associated with the overall survival in the heavy smoking patients were considered as the candidate genes for novel markers of smoking-related LUAD. The final novel risk factor gene was identified as MYH7 and the high express of MYH7 in LUAD correlation with patients' gender, lymph node metastasis, T stage, and clinical stage.

Conclusions

In summary, it can be concluded that MYH7 is a novel biomarker for heavy smoking-related LUAD and it is significantly correlated with the prognosis of lung cancer and is related to the clinical characteristics of lung cancer.

Multiscale computational investigations of the translesion synthesis bypass of tobacco-derived DNA adducts: critical insights that complement experimental biochemical studies

Among the numerous agents that damage DNA, tobacco products remain one of the most lethal and result in the most diverse set of DNA lesions. This perspective aims to provide an overview of computational work conducted to complement experimental biochemical studies on the mutagenicity of adducts derived from the most potent tobacco carcinogen, namely 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (nicotine-derived nitrosaminoketone or NNK). Lesions ranging from the smallest methylated thymine derivatives to the larger, flexible pyridyloxobutyl (POB) guanine adducts are considered. Insights are obtained from density functional theory (DFT) calculations and molecular dynamics (MD) simulations into the damaged nucleobase and nucleoside structures, the accommodation of the lesions in the active site of key human polymerases, the intrinsic base pairing potentials of the adducts, and dNTP incorporation opposite the lesions. Overall, the computational data provide atomic level information that can rationalize the differential mutagenic properties of tobacco-derived lesions and uncover important insights into the impact of adduct size, nucleobase, position, and chemical composition of the bulky moiety.

The Association Between Cyclooxygenase-2 -1195G/A (rs689466) Gene Polymorphism and the Clinicopathology of Lung Cancer in the Japanese Population: A Case-Controlled Study

The single nucleotide polymorphisms of COX-2 gene, also known as PTGS2, which encodes a pro-inflammatory factor cyclooxygenase-2, alter the risk of developing multiple tumors, but these findings are not consistent for lung cancer. We previously reported that the homozygous COX-2 –1195A genotype is associated with an increased risk for chronic obstructive pulmonary disease (COPD) in Japanese individuals. COPD is a significant risk factor for lung cancer due to genetic susceptibility to cigarette smoke. In this study, we investigated the association between COX-2 –1195G/A polymorphism and lung cancer susceptibility in the Japanese population. We evaluated the genotype distribution of COX-2 –1195G/A using a polymerase chain reaction-restriction fragment length polymorphism assay for 330 newly diagnosed patients with lung cancer and 162 healthy controls. Our results show that no relationship exists between the COX-2 –1195G/A polymorphism and the risk of developing lung cancer. However, compared to the control group, the homozygous COX-2 –1195A genotype increased the risk for lung squamous cell carcinoma (odds ratio = 2.902; 95% confidence interval, 1.171–7.195; p = 0.021), whereas no association is observed with the risk for adenocarcinoma. In addition, Kaplan-Meier analysis shows that the genotype distribution of homozygous COX-2 –1195A does not correlate with the overall survival of patients with lung squamous cell carcinoma. Thus, we conclude that the homozygous COX-2 –1195A genotype confers an increased risk for lung squamous cell carcinoma in Japanese individuals and could be used as a predictive factor for early detection of lung squamous cell carcinoma.

Racial Disparities in Cigarette Smoking Behaviors and Differences Stratified by Metropolitan Area of Residence

Background: Black cigarette smokers experience a disproportionate burden of non-small cell lung cancer (NSCLC) compared to other racial and ethnic groups, despite starting to smoke later in life, smoking less frequently, and smoking fewer cigarettes per day compared with White smokers. Research has shown that these disparities in NSCLC are wider in rural areas. Objective: To examine differences in smoking behaviors between Black and White individuals living in non-metropolitan areas and metropolitan areas. Methods: Using harmonized data from the Tobacco Use Supplement to the Current Population Survey (TUS-CPS) years 2010–2011, 2014–2015, and 2018–2019, we compared smoking behaviors between Black and White current and former smokers by metropolitan status (i.e., whether an individual lives in a densely populated area or not) and by both metropolitan status and sex. Results: Smoking prevalence was higher among White participants living in non-metropolitan versus Black participants. Further, in non-metropolitan areas, Black individuals reported smoking fewer cigarettes per day, fewer years of smoking, and a later age of initiation compared to White individuals. Additionally, Black individuals, especially men, were more likely than White individuals to be current non-daily smokers. Conclusions: Our findings show that Black individuals living in non-metropolitan areas do not, in aggregate, have more cigarette smoking exposure relative to White individuals. Additional research is needed to further understand smoking-related exposures and other factors that may contribute to lung cancer disparities, especially in non-metropolitan areas.

Secondhand smoke exposure in school children in Malta assessed through urinary biomarkers

School children may be exposed to secondhand smoke (SHS) either at home, in transit or in social gatherings permitting smoking in their presence. Questionnaires about SHS often underestimate prevalence and extent of exposure. A more accurate tool is the use of biomarkers such as cotinine (COT) and trans-3'-hydrocycotinine (3HC) as biomarkers of SHS exposure, alongside 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a reduction product in the body of the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), both potent carcinogens. We measured urinary COT, 3HC and total NNAL using sensitive and specific high-performance LC-MS/MS methods. The limit of quantification (LOQ) for each assay were 0.05 ng/mL, 0.1 ng/mL and 0.25 pg/mL respectively. The aim of this study was to evaluate the exposure to SHS of school children (9-11 years), from five public schools in the island of Malta, from questionnaire information about smoking at home and verify it by urinary biomarker data of COT, 3HC and NNAL. These biomarkers were measurable in 99.4%, 95.4% and 98.3% of the participating children respectively. From the children reporting smoking at home, 11% had a history of asthma and had COT, 3HC and NNAL geometric mean concentrations double compared to the non-asthmatic group. In has been confirmed that non-smokers exposed to SHS and THS have a higher NNAL/COT ratio than the group identified as smokers according to specific and defined COT threshold levels (despite the fact that a priori, the entire study group was composed of non-smokers). The implication of high measured levels of urinary NNAL in children should be of concern given its potency. A main effects multifactor ANOVA model was developed and the children's house and school locations and the smoking frequency were statistically significant to predict the levels of the three metabolites. For 3HC only, the status of the employment of the mother was also an important predictor.

90-day nose-only inhalation toxicity study of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in Sprague-Dawley rats

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the key tobacco-specific nitrosamines that plays an important role in human lung carcinogenesis. Repeated dose inhalation toxicity data on NNK, particularly relevant to cigarette smoking, however, is surprisingly limited. Hence, there is a lack of direct information available on the carcinogenic and potential non-carcinogenic effects of NNK via inhalational route exposure. In the present study, the subchronic inhalation toxicity of NNK was evaluated in Sprague Dawley rats. Both sexes (9-10 weeks age; 23 rats/sex/group) were exposed by nose-only inhalation to air, vehicle control (75% propylene glycol), or 0.2, 0.8, 3.2, or 7.8 mg/kg body weight (BW)/day of NNK (NNK aerosol concentrations: 0, 0, 0.0066, 0.026, 0.11, or 0.26 mg/L air) for 1 h/day for 90 consecutive days. Toxicity was evaluated by assessing body weights; food consumption; clinical pathology; histopathology; organ weights; blood, urine, and tissue levels of NNK, its major metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), and their glucuronides (reported as total NNK, tNNK, and total NNAL, tNNAL, respectively); tissue levels of the DNA adduct O6-methylguanine; blood and bone marrow micronucleus (MN) frequency; and bone marrow DNA strand breaks (comet assay). The results showed that NNK exposure caused multiple significant adverse effects, with the most sensitive endpoint being non-neoplastic lesions in the nose. Although the genotoxic biomarker O6-methylguanine was detected, genotoxicity from NNK exposure was negative in the MN and comet assays. The Lowest-Observed-Adverse-Effect-Level (LOAEL) was 0.8 mg/kg BW/day or 0.026 mg/L air of NNK for 1 h/day for both sexes. The No-Observed-Adverse-Effect-Level (NOAEL) was 0.2 mg/kg BW/day or 0.0066 mg/L air of NNK for 1 h/day for both sexes. The results of this study provide new information relevant to assessing the human exposure hazard of NNK.

Wonder or evil?: Multifaceted health hazards and health benefits of Cannabis sativa and its phytochemicals

Cannabis sativa, widely known as 'Marijuana' poses a dilemma for being a blend of both good and bad medicinal effects. The historical use of Cannabis for both medicinal and recreational purposes suggests it to be a friendly plant. However, whether the misuse of Cannabis and the cannabinoids derived from it can hamper normal body physiology is a focus of ongoing research. On the one hand, there is enough evidence to suggest that misuse of marijuana can cause deleterious effects on various organs like the lungs, immune system, cardiovascular system, etc. and also influence fertility and cause teratogenic effects. However, on the other hand, marijuana has been found to offer a magical cure for anorexia, chronic pain, muscle spasticity, nausea, and disturbed sleep. Indeed, most recently, the United Nations has given its verdict in favour of Cannabis declaring it as a non-dangerous narcotic. This review provides insights into the various health effects of Cannabis and its specialized metabolites and indicates how wise steps can be taken to promote good use and prevent misuse of the metabolites derived from this plant.

14-Day Nose-Only Inhalation Toxicity and Haber's Rule Study of NNK in Sprague-Dawley Rats

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the key tobacco-specific nitrosamines that plays an important role in human lung carcinogenesis. However, repeated inhalation toxicity data on NNK, which is more directly relevant to cigarette smoking, are currently limited. In the present study, the subacute inhalation toxicity of NNK was evaluated in Sprague Dawley rats. Both sexes (9-10 weeks age; 16 rats/sex/group) were exposed by nose-only inhalation to air, vehicle control (75% propylene glycol), or 0.8, 3.2, 12.5, or 50 mg/kg body weight (BW)/day of NNK (NNK aerosol concentrations: 0, 0, 0.03, 0.11, 0.41, or 1.65 mg/L air) for 1 hour/day for 14 consecutive days. Toxicity was evaluated by assessing body and organ weights; food consumption; clinical pathology; histopathology observations; blood, urine, and tissue levels of NNK, its major metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), and their glucuronides (reported as total NNK, tNNK, and total NNAL, tNNAL, respectively); O6-methylguanine DNA adduct formation; and blood and bone marrow micronucleus frequency. Whether the subacute inhalation toxicity of NNK followed Haber's Rule was also determined using additional animals exposed 4 hours/day. The results showed that NNK exposure caused multiple significant adverse effects, with the most sensitive endpoint being non-neoplastic histopathological lesions in the nose. The lowest-observed-adverse-effect level (LOAEL) was 0.8 mg/kg BW/day or 0.03 mg/L air for 1 hour/day for both sexes. An assessment of Haber's Rule indicated that 14-day inhalation exposure to the same dose at a lower concentration of NNK aerosol for a longer time (4 hours daily) resulted in greater adverse effects than exposure to a higher concentration of NNK aerosol for a shorter time (1 hour daily).

Chemical changes in thirdhand smoke associated with remediation using an ozone generator

Ozonation is a common remediation approach to eliminate odors from mold, tobacco and fire damage in buildings. Little information exists to: 1) assess its effectiveness; 2) provide guidance on operation conditions; and 3) identify potential risks associated with the presence of indoor ozone and ozonation byproducts. The goal of this study is to evaluate chemical changes in thirdhand smoke (THS) aerosols induced by high levels of ozone, in comparison with THS aerosols aged under similar conditions in the absence of ozone. Samples representing different stages of smoke aging in the absence of ozone, including freshly emitted secondhand smoke (SHS) and THS, were collected inside an 18-m3 room-sized chamber over a period of 42 h after six cigarettes were consumed. The experiments involved collection and analysis of gas phase species including volatile organic compounds (VOCs), volatile carbonyls, semivolatile organic compounds (SVOCs), and particulate matter. VOC analysis was carried out by gas chromatography/mass spectrometry with a thermal desorption inlet (TD-GC/MS), and volatile carbonyls were analyzed by on-line derivatization with dinitrophenylhydrazine (DNPH), followed by liquid chromatography with UV/VIS detection. SVOCs were extracted from XAD-coated denuders and Teflon-coated fiberglass filters in the absence of ozone. In those extracts, tobacco-specific nitrosamines (TSNAs) and other SVOCs were analyzed by gas chromatography with positive chemical ionization-triple quadrupole mass spectrometric detection (GC/PCI-QQQ-MS), and polycyclic aromatic hydrocarbons (PAHs) were quantified by gas chromatography with ion trap mass spectrometric detection (GC/IT-MS) in selected ion monitoring mode. Particulate matter concentration was determined gravimetrically. In a second experiment, a 300 mg h-1 commercial ozone generator was operated during 1 h, one day after smoke was generated, to evaluate the remediation of THS by ozonation. VOCs and volatile carbonyls were analyzed before and after ozonation. Extracts from fabrics that were exposed in the chamber before and after ozonation as surrogates for indoor furnishings were analyzed by GC/IT-MS, and aerosol size distribution was studied with a scanning mobility particle sizer. Ozone concentration was measured with a photometric detector. An estimated 175 mg ozone reacted with THS after 1 h of treatment, corresponding to 58% of the total O3 released during that period. Fabric-bound nicotine was depleted after ozonation, and the surface concentration of PAHs adsorbed to fabric specimens decreased by an order of magnitude due to reaction with ozone, reaching pre-smoking levels. These results suggest that ozonation has the potential to remove harmful THS chemicals from indoor surfaces. However, gas phase concentrations of volatile carbonyls, including formaldehyde, acetaldehyde and acetone were higher immediately after ozonation. Ultrafine particles (UFP, in most cases with size <60 nm) were a major ozonation byproduct. UFP number concentrations peaked shortly after ozonation ended, and remained at higher-than background levels for several hours. Based on these results, minimum re-entry times after ozone treatment were predicted for different indoor scenarios. Clearly defining re-entry times can serve as a practical measure to prevent acute exposures to ozone and harmful ozonation byproducts after treatment. This study evaluated potential benefits and risks associated with THS remediation using ozone, providing insights into this technology.

Repair of O6-carboxymethylguanine adducts by O6-methylguanine-DNA methyltransferase in human colon epithelial cells

The protein O6-methylguanine-DNA methyltransferase (MGMT) is able to repair the mutagenic O6-methylguanine adduct back to guanine. In this context, it may protect against colorectal cancer (CRC) formation associated with N-nitroso compounds. Such compounds may be endogenously formed by nitrosylation of amino acids, which can give rise to mutagenic O6-methylguanine (O6-MeG) and O6-carboxymethylguanine (O6-CMG) adducts. It is well-established that O6-MeG is repaired by MGMT. However, up to now, whether O6-CMG is repaired by this enzyme remains unresolved. Therefore, the aim of the present study was to analyze the fate of both types of O6-guanine adducts in the presence and absence of MGMT activity. To this end, MGMT activity was efficiently blocked by its chemical inhibitor O6-benzylguanine in human colon epithelial cells (HCEC). Exposure of cells to azaserine (AZA) caused significantly higher levels of both O6-MeG and O6-CMG adducts in MGMT-inhibited cells, with O6-CMG as the more abundant DNA lesion. Interestingly, MGMT inhibition did not result in higher levels of AZA-induced DNA strand breaks in spite of elevated DNA adduct levels. In contrast, MGMT inhibition significantly increased DNA strand break formation after exposure to temozolomide (TMZ), a drug that exclusively generates O6-MeG adducts. In line with this finding, the viability of the cells was moderately reduced by TMZ upon MGMT inhibition, whereas no clear effect was observed in cells treated with AZA. In conclusion, our study clearly shows that O6-CMG is repaired by MGMT in HCEC, thereby suggesting that MGMT might play an important role as a tumor suppressor in diet-mediated CRC.

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.

Coexposure to Inhaled Aldehydes or Carbon Dioxide Enhances the Carcinogenic Properties of the Tobacco-Specific Nitrosamine 4-Methylnitrosamino-1-(3-pyridyl)-1-butanone in the A/J Mouse Lung

Tobacco smoke is a complex mixture of chemicals, many of which are toxic and carcinogenic. Hazard assessments of tobacco smoke exposure have predominantly focused on either single chemical exposures or the more complex mixtures of tobacco smoke or its fractions. There are fewer studies exploring interactions between specific tobacco smoke chemicals. Aldehydes such as formaldehyde and acetaldehyde were hypothesized to enhance the carcinogenic properties of the human carcinogen, 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) through a variety of mechanisms. This hypothesis was tested in the established NNK-induced A/J mouse lung tumor model. A/J mice were exposed to NNK (intraperitoneal injection, 0, 2.5, or 7.5 μmol in saline) in the presence or absence of acetaldehyde (0 or 360 ppmv) or formaldehyde (0 or 17 ppmv) for 3 h in a nose-only inhalation chamber, and lung tumors were counted 16 weeks later. Neither aldehyde by itself induced lung tumors. However, mice receiving both NNK and acetaldehyde or formaldehyde had more adenomas with dysplasia or progression than those receiving only NNK, suggesting that aldehydes may increase the severity of NNK-induced lung adenomas. The aldehyde coexposure did not affect the levels of NNK-derived DNA adduct levels. Similar studies tested the ability of a 3 h nose-only carbon dioxide (0, 5, 10, or 15%) coexposure to influence lung adenoma formation by NNK. While carbon dioxide alone was not carcinogenic, it significantly increased the number of NNK-derived lung adenomas without affecting NNK-derived DNA damage. These studies indicate that the chemicals in tobacco smoke work together to form a potent lung carcinogenic mixture.

Constitutive activation of nitrate reductase in tobacco alters flowering time and plant biomass

Pyridine alkaloids produced in tobacco can react with nitrosating agents such as nitrite to form tobacco-specific nitrosamines (TSNA), which are among the most notable toxicants present in tobacco smoke. The market type known as burley tobacco is particularly susceptible to TSNA formation because its corresponding cultivars exhibit a nitrogen-use-deficiency phenotype which results in high accumulation of nitrate, which, in turn, is converted to nitrite by leaf surface microbes. We have previously shown that expression of a constitutively activated nitrate reductase (NR) enzyme dramatically decreases leaf nitrate levels in burley tobacco, resulting in substantial TSNA reductions without altering the alkaloid profile. Here, we show that plants expressing a constitutively active NR construct, designated 35S:S523D-NR, display an early-flowering phenotype that is also associated with a substantial reduction in plant biomass. We hypothesized that crossing 35S:S523D-NR tobaccos with burley cultivars that flower later than normal would help mitigate the undesirable early-flowering/reduced-biomass traits while maintaining the desirable low-nitrate/TSNA phenotype. To test this, 35S:S523D-NR plants were crossed with two late-flowering cultivars, NC 775 and NC 645WZ. In both cases, the plant biomass at harvest was restored to levels similar to those in the original cultivar used for transformation while the low-nitrate/TSNA trait was maintained. Interestingly, the mechanism by which yield was restored differed markedly between the two crosses. Biomass restoration in F1 hybrids using NC 645WZ as a parent was associated with delayed flowering, as originally hypothesized. Unexpectedly, however, crosses with NC 775 displayed enhanced biomass despite maintaining the early-flowering trait of the 35S:S523D-NR parent.

Mitochondrial Transcription Factor A Binds to and Promotes Mutagenic Transcriptional Bypass of O4-Alkylthymidine Lesions

O2- and O4-alkylated thymidine lesions are known to be poorly repaired and persist in mammalian tissues. To understand how mammalian cells sense the presence and regulate the repair of these lesions, we employed a quantitative proteomic method to discover regioisomeric O2- and O4-n-butylthymidine (O2- and O4-nBudT)-binding proteins. We were able to identify 21 and 74 candidate DNA damage recognition proteins for O2-nBudT- and O4-nBudT-bearing DNA probes, respectively. Among these proteins, DDB1 and DDB2 selectively bind to O2-nBudT-containing DNA, whereas three high-mobility group (HMG) proteins (i.e., HMGB1, HMGB2, and mitochondrial transcription factor A (TFAM)) exhibit preferential binding to O4-nBudT-bearing DNA. We further demonstrated that TFAM binds directly and selectively with O4-alkyldT-harboring DNA, and the binding capacity depends mainly on the HMG box-A domain of TFAM. We also found that TFAM promotes transcriptional mutagenesis of O4-nBudT and O4-pyridyloxobutylthymidine, which is a DNA adduct induced by tobacco-specific N-nitrosamines, in vitro and in human cells. Together, we explored, for the first time, the interaction proteomes of O-alkyldT lesions, and our study expanded the functions of TFAM by revealing its capability in the recognition of O4-alkyldT-bearing DNA and uncovering its modulation of transcriptional mutagenesis of these lesions in human cells.

Multi-Omics Analysis to Characterize Cigarette Smoke Induced Molecular Alterations in Esophageal Cells

Though smoking remains one of the established risk factors of esophageal squamous cell carcinoma, there is limited data on molecular alterations associated with cigarette smoke exposure in esophageal cells. To investigate molecular alterations associated with chronic exposure to cigarette smoke, non-neoplastic human esophageal epithelial cells were treated with cigarette smoke condensate (CSC) for up to 8 months. Chronic treatment with CSC increased cell proliferation and invasive ability of non-neoplastic esophageal cells. Whole exome sequence analysis of CSC treated cells revealed several mutations and copy number variations. This included loss of high mobility group nucleosomal binding domain 2 (HMGN2) and a missense variant in mediator complex subunit 1 (MED1). Both these genes play an important role in DNA repair. Global proteomic and phosphoproteomic profiling of CSC treated cells lead to the identification of 38 differentially expressed and 171 differentially phosphorylated proteins. Bioinformatics analysis of differentially expressed proteins and phosphoproteins revealed that most of these proteins are associated with DNA damage response pathway. Proteomics data revealed decreased expression of HMGN2 and hypophosphorylation of MED1. Exogenous expression of HMGN2 and MED1 lead to decreased proliferative and invasive ability of smoke exposed cells. Immunohistochemical labeling of HMGN2 in primary ESCC tumor tissue sections (from smokers) showed no detectable expression while strong to moderate staining of HMGN2 was observed in normal esophageal tissues. Our data suggests that cigarette smoke perturbs expression of proteins associated with DNA damage response pathways which might play a vital role in development of ESCC.

Predominant DNMT and TET mediate effects of allergen on the human bronchial epithelium in a controlled air pollution exposure study

BACKGROUND

Epidemiological data show that traffic-related air pollution contributes to the increasing prevalence and severity of asthma. DNA methylation (DNAm) changes may elucidate adverse health effects of environmental exposures.

OBJECTIVES

We sought to assess the effects of allergen and diesel exhaust (DE) exposures on global DNAm and its regulation enzymes in human airway epithelium.

METHODS

A total of 11 participants, including 7 with and 4 without airway hyperresponsiveness, were recruited for a randomized, double-blind crossover study. Each participant had 3 exposures: filtered air + saline, filtered air + allergen, and DE + allergen. Forty-eight hours postexposure, endobronchial biopsies and bronchoalveolar lavages were collected. Levels of DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) enzymes, 5-methylcytosine, and 5-hydroxymethylcytosine were determined by immunohistochemistry. Cytokines and chemokines in bronchoalveolar lavages were measured by electrochemiluminescence multiplex assays.

RESULTS

Predominant DNMT (the most abundant among DNMT1, DNMT3A, and DNMT3B) and predominant TET (the most abundant among TET1, TET2, and TET3) were participant-dependent. 5-Methylcytosine and its regulation enzymes differed between participants with and without airway hyperresponsiveness at baseline (filtered air + saline) and in response to allergen challenge (regardless of DE exposure). Predominant DNMT and predominant TET correlated with lung function. Allergen challenge effect on IL-8 in bronchoalveolar lavages was modified by TET2 baseline levels in the epithelium.

CONCLUSIONS

Response to allergen challenge is associated with key DNAm regulation enzymes. This relationship is generally unaltered by DE coexposure but is rather dependent on airway hyperresponsiveness status. These enzymes therefore warranted further inquiry regarding their potential in diagnosis, prognosis, and treatment of asthma.

BRIP1 rs10744996C>A variant increases the risk of chronic obstructive pulmonary disease in the Mongolian population of northern China

NEW FINDINGS

What is the central question of this study? What is the role of breast cancer type 1 interacting protein C-terminal helicase 1 (BRIP1) polymorphism in chronic obstructive pulmonary disease (COPD)? What is the main finding and its importance? Variant rs10744996C>A of BRIP1 increases the susceptibility of the Mongolian population to COPD. The expression of BRIP1 was significantly reduced in cigarette smoke extract-treated airway epithelial cells.

ABSTRACT

Cigarette smoke is a major environmental pollutant that can induce DNA damage in humans. The development and progression of chronic obstructive pulmonary disease (COPD) are known to be related to the impairment of DNA repair. Breast cancer type 1 interacting protein C-terminal helicase 1 (BRIP1) plays an important role in DNA interstrand crosslink repair and double-strand break repair. However, the role of BRIP1 polymorphisms in COPD has not been previously described. In this study, whole genome sequencing was used to identify mutations, and single nucleotide polymorphism (SNP) genotyping was used to verify the selected SNPs. In addition the BRIP1 expression levels in 16HBE and A549 airway epithelial cells treated with or without cigarette smoke extract (CSE) were measured using western blotting and RT-qPCR. Rs10744996C>A in the 3'-untranslated region (3'UTR) of BRIP1 was then genotyped in 1296 COPD cases and 988 healthy control subjects from a Mongolian population in northern China. Significant differences in the distribution of rs10744996C>A variants between COPD and control groups (P = 0.001) were identified. Rs10744996C>A was found to be associated with significantly increased COPD risk (adjusted odds ratio = 1.60, 95% CI = 1.30-1.98, P < 0.0001). Additionally, rs10744996A genotype was found to interact with a family history of cancer and a history of x-ray exposure (P = 0.028 and 0.009, respectively). BRIP1 expression levels in 16HBE and A549 cells treated with CSE were significantly lower compared to the control treated cells. The rs10744996C>A variant of BRIP1 increased the COPD susceptibility of the Mongolian population cohort. BRIP1 mRNA and protein expression levels were significantly reduced in conjunction with CSE-induced DNA damage in 16HBE and A549 cells.

Oral Dosing of Dihydromethysticin Ahead of Tobacco Carcinogen NNK Effectively Prevents Lung Tumorigenesis in A/J Mice

Our early studies demonstrated an impressive chemopreventive efficacy of dihydromethysticin (DHM), unique in kava, against tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice in which DHM was supplemented in the diet. The current work was carried out to validate the efficacy, optimize the dosing schedule, and further elucidate the mechanisms using oral bolus dosing of DHM. The results demonstrated a dose-dependent chemopreventive efficacy of DHM (orally administered 1 h before each of the two NNK intraperitoneal injections, 1 week apart) against NNK-induced lung adenoma formation. Temporally, DHM at 0.8 mg per dose (∼32 mg per kg body weight) exhibited 100% lung adenoma inhibition when given 3 and 8 h before each NNK injection and attained >93% inhibition when dosed at either 1 or 16 h before each NNK injection. The simultaneous treatment (0 h) or 40 h pretreatment (-40 h) decreased lung adenoma burden by 49.8% and 52.1%, respectively. However, post-NNK administration of DHM (1-8 h after each NNK injection) was ineffective against lung tumor formation. In short-term experiments for mechanistic exploration, DHM treatment reduced the formation of NNK-induced O6-methylguanine (O6-mG, a carcinogenic DNA adduct in A/J mice) in the target lung tissue and increased the urinary excretion of NNK detoxification metabolites as judged by the ratio of urinary NNAL-O-gluc to free NNAL, generally in synchrony with the tumor prevention efficacy outcomes in the dose scheduling time-course experiment. Overall, these results suggest DHM as a potential chemopreventive agent against lung tumorigenesis in smokers, with O6-mG and NNAL detoxification as possible surrogate biomarkers.

An Integrated Genomic Strategy to Identify CHRNB4 as a Diagnostic/Prognostic Biomarker for Targeted Therapy in Head and Neck Cancer

Although many studies have shown the association between smoking and the increased incidence and adverse prognosis of head and neck squamous cell carcinoma (HNSCC), the mechanisms and pharmaceutical targets involved remain unclear. Here, we integrated gene expression signatures, genetic alterations, and survival analyses to identify prognostic indicators and therapeutic targets for smoking HNSCC patients, and we discovered that the FDA-approved drug varenicline inhibits the target for cancer cell migration/invasion. We first identified 18 smoking-related and prognostic genes for HNSCC by using RNA-Seq and clinical follow-up data. One of these genes, CHRNB4 (neuronal acetylcholine receptor subunit beta-4), increased the risk of death by approximately threefold in CHRNB4-high expression smokers compared to CHRNB4-low expression smokers (log rank, p = 0.00042; hazard ratio, 2.82; 95% CI, 1.55–5.14), former smokers, and non-smokers. Furthermore, we examined the functional enrichment of co-regulated genes of CHRNB4 and its 246 frequently occurring copy number alterations (CNAs). We found that these genes were involved in promoting angiogenesis, resisting cell death, and sustaining proliferation, and contributed to much worse outcomes for CHRNB4-high patients. Finally, we performed CHRNB4 gene editing and drug inhibition assays, and the results validate these observations. In summary, our study suggests that CHRNB4 is a prognostic indicator for smoking HNSCC patients and provides a potential new therapeutic drug to prevent recurrence or distant metastasis.

Metabolomics Profiles of Smokers from Two Ethnic Groups with Differing Lung Cancer Risk

African American (AA) smokers are at a higher risk of developing lung cancer compared to whites. The variations in the metabolism of nicotine and tobacco-derived carcinogens in these groups were reported previously with the levels of nicotine metabolites and carcinogen-derived metabolites measured using targeted approaches. While useful, these targeted strategies are not able to detect global metabolic changes for use in predicting the detrimental effects of tobacco use and ultimately lung cancer susceptibility among smokers. To address this limitation, we have performed global untargeted metabolomics profiling in urine of AA and white smokers to characterize the pattern of metabolites, identify differentially regulated pathways, and correlate these profiles with the observed variations in lung cancer risk between these two populations. Urine samples from AA (n = 30) and white (n = 30) smokers were used for metabolomics analysis acquired in both positive and negative electrospray ionization modes. LC-MS data were uploaded onto the cloud-based XCMS online (http://xcmsonline.scripps.edu) platform for retention time correction, alignment, feature detection, annotation, statistical analysis, data visualization, and automated systems biology pathway analysis. The latter identified global differences in the metabolic pathways in the two groups including the metabolism of carbohydrates, amino acids, nucleotides, fatty acids, and nicotine. Significant differences in the nicotine degradation pathway (cotinine glucuronidation) in the two groups were observed and confirmed using a targeted LC-MS/MS approach. These results are consistent with previous studies demonstrating AA smokers with lower glucuronidation capacity compared to whites. Furthermore, the d-glucuronate degradation pathway was found to be significantly different between the two populations, with lower amounts of the putative metabolites detected in AA compared to whites. We hypothesize that the differential regulation of the d-glucuronate degradation pathway is a consequence of the variations in the glucuronidation capacity observed in the two groups. Other pathways including the metabolism of amino acids, nucleic acids, and fatty acids were also identified, however, the biological relevance and implications of these differences across ethnic groups need further investigation. Overall, the applied metabolomics approach revealed global differences in the metabolic networks and endogenous metabolites in AA and whites, which could be used and validated as a new potential panel of biomarkers that could be used to predict lung cancer susceptibility among smokers in population-based studies.

Dose-related effect of secondhand smoke on cardiovascular disease in nonsmokers: Systematic review and meta-analysis

BACKGROUND

Despite the positive association between secondhand smoke (SHS) and cardiovascular diseases (CVD), no comprehensive assessment on the dose-response relationship between SHS and CVD has yet been reported. Therefore, a meta-analysis was conducted to update the binary association, and to elucidate the dose-response relationship of both self-reported and objectively measured SHS exposure with CVD.

METHODS

PubMed and Embase databases were searched for articles published up to November 12, 2019. Random-effects models were used to assess the summary odds ratios (ORs) of CVD with SHS exposure. Restricted cubic splines were used to fit the dose-response relationship.

RESULTS

Fifty-five eligible observational studies were included in this meta-analysis to investigate the association between SHS exposure and CVD. Based on the meta-analysis, the pooled OR of CVD was 1.22 (95% CI 1.17-1.28) for the self-reported SHS individuals as comparing to the non-exposed group. The result of restricted cubic splines showed a risk plateau of SHS exposure at 15 cigarettes per day (P_{non-linearity} = 0.042), while other characteristics s of SHS exposure (amount, daily and cumulative duration, and cotinine) were in linear relationships with CVD (P_{non-linearity} >0.05). In addition, an estimated of 6.77% (95% CI: 5.31%-8.46%) of all CVD cases in men and 7.15% (95% CI: 5.62%-8.93%) in women might be attributed to SHS exposure worldwide.

CONCLUSIONS

Exposure to SHS is associated with an increased risk of CVD regardless of the modes. And thus, well-enforced smoke-free laws could possibly reduce a substantial risk of CVD caused by SHS.

DNA adducts: Formation, biological effects, and new biospecimens for mass spectrometric measurements in humans

Hazardous chemicals in the environment and diet or their electrophilic metabolites can form adducts with genomic DNA, which can lead to mutations and the initiation of cancer. In addition, reactive intermediates can be generated in the body through oxidative stress and damage the genome. The identification and measurement of DNA adducts are required for understanding exposure and the causal role of a genotoxic chemical in cancer risk. Over the past three decades, 32 P-postlabeling, immunoassays, gas chromatography/mass spectrometry, and liquid chromatography/mass spectrometry (LC/MS) methods have been established to assess exposures to chemicals through measurements of DNA adducts. It is now possible to measure some DNA adducts in human biopsy samples, by LC/MS, with as little as several milligrams of tissue. In this review article, we highlight the formation and biological effects of DNA adducts, and highlight our advances in human biomonitoring by mass spectrometric analysis of formalin-fixed paraffin-embedded tissues, untapped biospecimens for carcinogen DNA adduct biomarker research.

Systems biology analysis of publicly available transcriptomic data reveals a critical link between AKR1B10 gene expression, smoking and occurrence of lung cancer

Background

Cigarette smoking is associated with an increased risk of developing respiratory diseases and various types of cancer. Early identification of such unfavorable outcomes in patients who smoke is critical for optimizing personalized medical care.

Methods

Here, we perform a comprehensive analysis using Systems Biology tools of publicly available data from a total of 6 transcriptomic studies, which examined different specimens of lung tissue and/or cells of smokers and nonsmokers to identify potential markers associated with lung cancer.

Results

Expression level of 22 genes was capable of classifying smokers from non-smokers. A machine learning algorithm revealed that AKR1B10 was the most informative gene among the 22 differentially expressed genes (DEGs) accounting for the classification of the clinical groups. AKR1B10 expression was higher in smokers compared to non-smokers in datasets examining small and large airway epithelia, but not in the data from a study of sorted alveolar macrophages. Moreover, AKR1B10 expression was relatively higher in lung cancer specimens compared to matched healthy tissue obtained from nonsmoking individuals. Although the overall accuracy of AKR1B10 expression level in distinction between cancer and healthy lung tissue was 76%, with a specificity of 98%, our results indicated that such marker exhibited low sensitivity, hampering its use for cancer screening such specific setting.

Conclusion

The systematic analysis of transcriptomic studies performed here revealed a potential critical link between AKR1B10 expression, smoking and occurrence of lung cancer.

Metabolic reprogramming by tobacco-specific nitrosamines (TSNAs) in cancer

Metabolic reprogramming is a hallmark of cancer and the link between oncogenes activation, tumor supressors inactivation and bioenergetics modulation is well established. However, numerous carcinogenic environmental factors are responsible for early cancer initiation and their impact on metabolic reprogramming just starts to be deciphered. For instance, it was recently shown that UVB irradiation triggers metabolic reprogramming at the pre-cancer stage with implication for skin cancer detection and therapy. These observations foster the need to study the early changes in tissue metabolism following exposure to other carcinogenic events. According to the International Agency for Research on Cancer (IARC), tobacco smoke is a major class I-carcinogenic environmental factor that contains different carcinogens, but little is known on the impact of tobacco smoke on tissue metabolism and its participation to cancer initiation. In particular, tobacco-specific nitrosamines (TSNAs) play a central role in tobacco-smoke mediated cancer initiation. Here we describe the recent advances that have led to a new hypothesis regarding the link between nitrosamines signaling and metabolic reprogramming in cancer.

Tobacco smoking and somatic mutations in human bronchial epithelium

Tobacco smoking causes lung cancer1-3, a process that is driven by more than 60 carcinogens in cigarette smoke that directly damage and mutate DNA4,5. The profound effects of tobacco on the genome of lung cancer cells are well-documented6-10, but equivalent data for normal bronchial cells are lacking. Here we sequenced whole genomes of 632 colonies derived from single bronchial epithelial cells across 16 subjects. Tobacco smoking was the major influence on mutational burden, typically adding from 1,000 to 10,000 mutations per cell; massively increasing the variance both within and between subjects; and generating several distinct mutational signatures of substitutions and of insertions and deletions. A population of cells in individuals with a history of smoking had mutational burdens that were equivalent to those expected for people who had never smoked: these cells had less damage from tobacco-specific mutational processes, were fourfold more frequent in ex-smokers than current smokers and had considerably longer telomeres than their more-mutated counterparts. Driver mutations increased in frequency with age, affecting 4-14% of cells in middle-aged subjects who had never smoked. In current smokers, at least 25% of cells carried driver mutations and 0-6% of cells had two or even three drivers. Thus, tobacco smoking increases mutational burden, cell-to-cell heterogeneity and driver mutations, but quitting promotes replenishment of the bronchial epithelium from mitotically quiescent cells that have avoided tobacco mutagenesis.

Effects of IL-4-590C/T (rs2243250) Polymorphism on the Susceptibility of Smoking-Related Cancer: A Meta-Analysis Involving 11,407 Subjects

Background

Several previous studies have assessed the relationship between IL-4-590C/T gene polymorphism and smoking-related cancer in recent years; however, the results remain controversial. Based on it, the study intends to clarify whether IL-4-590C/T variant increases the risk of smoking-related cancer through meta-analysis.

Methods

We searched PubMed, EMBASE, Web of Science, Cochrane Library database, China National Knowledge Infrastructure, and Wanfang data information service platform to collect qualified case-control studies in strict accordance with the inclusion and exclusion standards. The 95% confidence interval (95% CI) and its odds ratio (OR) were adopted to access the relation between IL-4-590C/T gene polymorphism and smoking-related cancer; sensitivity analysis and publication bias assessment were carried out after the studies' quality evaluation.

Results

17 studies were included in total, with 5,061 patients and 6,346 control cases. A significant association between IL-4-590C/T variant and smoking-related cancer in total population was revealed in our meta-analysis results, and IL-4-590C/T variant might have a relatively protective effect on smoking-related cancer (CT vs. TT: P=0.026, OR = 0.900, 95% CI: 0.820–0.987). Subgroup analysis by ethnicity showed that the IL-4-590C/T polymorphism was associated with a decreased risk of smoking-related cancer in the Asian population (CT vs. TT: P=0.008, OR = 0.878, 95% CI: 0.798–0.967; CC + CT vs. TT: P=0.030, OR = 0.903, 95% CI: 0.824–0.990). Subgroup analysis based on types of cancer demonstrated the IL-4-590C/T variant achieved a lower risk in renal cell cancer (CC vs. TT: P=0.046, OR = 0.640, 95% CI: 0.412–0.993).

Conclusion

There is a conspicuous association between IL-4-590C/T polymorphism and decreased risk of smoking-related cancer, particularly in Asians. And IL-4-590C/T polymorphism may have a protective effect on renal cell cancer.

Effects of the Tobacco Carcinogens N'-Nitrosonornicotine and Dibenzo[a,l]pyrene Individually and in Combination on DNA Damage in Human Oral Leukoplakia and on Mutagenicity and Mutation Profiles in lacI Mouse Tongue

In previous studies, we showed that the topical application of dibenzo[a,l]pyrene (DB[a,l]P), also known as dibenzo[def,p]chrysene, to the oral cavity of mice induced oral squamous cell carcinoma. We also showed that dA and dG adducts likely account for most of the mutagenic activity of DB[a,l]P in the oral tissues in vivo. Here we report for the first time that the oral treatment of lacI mice with a combination of tobacco smoke carcinogens, DB[a,l]P and N'-nitrosonornicotine (NNN), induces a higher fraction of mutations than expected from a simple sum of their induced individual mutation fractions, and a change in the mutational profile compared with that expected from the sum of the individual agents. The mutational profile of the combination of agents resembled that of the P53 gene in human head and neck cancers more than that of either of the individual agents, in that the percentage of the major class of mutations (GC > AT transitions) is similar to that seen in the P53 gene. A preliminary study was performed to understand the origin of the unexpected mutagenesis observations by measuring specific DNA adducts produced by both NNN and DB[a,l]P in human oral leukoplakia cells. No significant differences in the expected and observed major adduct levels from either agent were observed between individual or combined treatments, suggesting that additional adducts are important in mutagenesis induced by the mixture. Taken together, the above observations support the use of this animal model not only to investigate tobacco smoke-induced oral cancer but also to study chemoprevention.

Genome-wide somatic mutation analysis via Hawk-Seq™ reveals mutation profiles associated with chemical mutagens

It is difficult to identify mutagen-induced genome-wide somatic mutations using next generation sequencing; hence, mutagenic features of each mutagen and their roles in cancer development require further elucidation. We described Hawk-Seq™, a highly accurate genome sequencing method and the optimal conditions, for using it to construct libraries that would enable the accurate (c.a. 1 error/10⁷-10⁸ bp) and efficient survey of genome-wide mutations. Genomic mutations in gpt delta mice or Salmonella typhimurium TA100 exposed to methylnitrosourea (MNU), ethylnitrosourea (ENU), diethylnitrosamine (DEN), benzo[a]pyrene (BP), and aristolochic acid (AA) were profiled using Hawk-Seq™ to analyse positions, substitution patterns, or frequencies. The resultant vast mutation data provided high-resolution mutational signatures, including for minor mutational fractions (e.g. G:C>A:T by AA), which enabled the clarification of the mutagenic features of all mutagens. The 96-type mutational signatures of MNU, AA, and BP indicate their partial similarity to signature 11, 22, and 4 or 29, respectively. Meanwhile, signatures attributable to ENU and DEN were highly similar to each other, but not to signature 11, suggesting that the mechanisms of these agents differed from those of typical alkylating agents. Thus, Hawk-Seq™ can clarify genome-wide chemical mutagenicity profiles at extraordinary resolutions, thereby providing insight into mutagen mechanisms and their roles in cancer development.

The impact of smoking and the influence of other factors on lung cancer

Introduction: Smoking is the main preventable cause of lung cancer. This review summarizes preclinical and clinical data on the mechanisms of smoking-associated cancer development of the major histological lung cancer types small cell lung carcinoma squamous cell carcinoma and pulmonary adenocarcinoma (PAC) and the impact of several factors other than smoking on this process. Areas covered: The role of intracellular signaling induced by nicotinic receptors and beta-adrenergic receptors, the resulting increase in intracellular cyclic adenosine monophosphate (cAMP) as a key driver of PAC and the promoting effects of respiratory tract diseases and their therapeutics, psychological stress and global warming. Expert opinion: Smoking has deleterious effects on the regulation of lung epithelia by neurotransmitter receptors that are further enhanced by gene mutations. Sensitization of the alpha-7 nicotinic receptor (α7nAChR) by COPD enhances the carcinogenic effects of smoking and turns nicotine into a carcinogen. Nicotine vaping may, therefore, cause cancer in individuals with chronic obstructive pulmonary disease. The opposing effects of cAMP on the major lung cancer types indicate that patients with PAC of Clara cell phenotype (PAC-Cl) will benefit from treatment with cAMP reducers and suggest that global warming-induced respiratory tract diseases and their therapeutics cause the global increase in the incidence of PAC.

Smoking History Decreases Survival in Patients with Squamous Cell Carcinoma of the Mouth: A Retrospective Study with 15 Years of Follow-up

Background:

The purpose of this study was to evaluate the influence of smoking history on the clinical-pathological, sociodemographic and prognostic characteristics of patients with oral squamous cell carcinoma (SCC).

Materials and Methods:

A retrospective cohort study was carried out with the records of 136 smokers with SCC and 68 nonsmokers with oral SCC who were diagnosed and treated at Haroldo Juaçaba Hospital (2000-2014). Data on patient sex, age, race, education level, tumor location, tumor size, lymph node involvement, distant metastasis, treatment type, marital status, method of health care access (public or private health systems) and overall survival (15 years) were analyzed by the X² test, Mantel-Cox tests and multinomial and Cox logistic regression models (SPSS 20.0, p <0.05).

Results:

Smoking history was directly associated with male sex (p <0.001), low levels of education (p = 0.001), tumors of the mouth and palate (p = 0.001), stage T3/4 tumors (p = 0.014), lymph node metastasis (N+) (p = 0.024), palliative treatment (p = 0.024) and receiving health care through the public health system (p = 0.006), with education level being the only independently associated factor (p = 0.039). Lower survival was observed in patients who were smokers (p = 0,002), with low levels of education (p = 0.001), who had stage T3/4 tumors (p = 0.004), with N+ (p = 0.021), and had received palliative treatment (p = 0.002). Age (>65 years old, p = 0.015) and T staging (T3/4, p = 0.033) decreased the survival of SCC patients regardless of the other factors.

Conclusions:

Smoking history had an independent association with low education level and a history of alcoholism, and survival was negatively associated with older age and larger tumor size, which were more prevalent in smokers.

The synergistic effect of tobacco and alcohol consumption on oral squamous cell carcinoma: a systematic review and meta-analysis

OBJECTIVES

This systematic review (SR) aimed to summarise and critically appraise available evidence about the association between the synergistic consumption of alcohol and tobacco and the occurrence of oral squamous cell carcinoma (OSCC).

MATERIALS AND METHODS

Observational studies investigating the association between the synergistic consumption of alcohol and tobacco and OSCC occurrence were included. Studies were selected in a two-phase process and searches were conducted on five main electronic databases, complemented by three grey literature databases.

RESULTS

From 3260 records identified, 33 articles were included for qualitative analysis, of which 15 were included in the meta-analyses. Overall, the synergistic consumption was positively associated with the occurrence of OSCC (odds ratio [OR] = 5.37; 95% confidence interval [95%CI] = 3.54-8.14). Increased odds for OSCC occurrence were observed regarding the synergistic consumption of alcohol and smoked tobacco (OR = 4.74; 95%CI = 3.51-6.40), alcohol and smokeless tobacco (OR = 7.78; 95%CI = 2.86-21.14), and alcohol, smoked tobacco, and smokeless tobacco (OR = 16.17; 95%CI = 7.97-32.79).

CONCLUSIONS

According to the results of this SR, the synergistic consumption of alcohol and tobacco (both smoked and smokeless) significantly increased the odds for the occurrence of OSCC.

CLINICAL RELEVANCE

The knowledge provided by this SR may be useful for a better understanding of differences in the effect of synergistic consumption of alcohol and tobacco products in OSCC development. These data might aid healthcare authorities to develop measures for tobacco and alcohol control considering the needs of their population.

The Neuro-Psychological Axis of Smoking-Associated Cancer

This mini-review summarizes current knowledge on similarities and synergism between smoking and psychological stress-induced modulations of growth stimulating and inhibiting regulatory networks in epithelial cells and epithelial cancers with emphasis on cancer stimulating neurotransmitters and their receptors as well as cancer inhibiting γ-aminobutyric acid (GABA) and opioids. Hyperactive cAMP signaling downstream of beta-adrenergic receptors (β-ARs) has been identified as the driving force of most smoking-associated cancers by numerous preclinical studies and psychological stress intensifies these effects while experimental stress reduction inhibits. The integration of cAMP reduction via stress reduction by pharmacological and psychological means such as psychotherapy, relaxation meditation and yoga into any cancer treatment strategy is recommended.

The effect of malondialdehyde is modified by simian virus 40 transformation in human lung fibroblast cells

The effects of malondialdehyde (MDA), a product of oxidative stress, on normal lung fibroblast cells (MRC5) and transformed cells (MRC5 SV2) showed differing responses between the two cell lines. MRC5 cells showed lower viability at low MDA concentrations (<250 μM) but had better viability at higher concentrations than the transformed cells. Both cell lines showed an increase in the number of micronuclei, nuclear size and a relocation of p53 to the nucleus with increasing MDA. The expression of p53 was higher in the MRC5 cells at 24 h; 2-8 fold induction vs 1-2.5 fold in the MRC5 SV2 cells, but reduced to almost zero at 48 h in the MRC5 cells. Mutation sequencing of the PCR products of a 689 bp region (residues 4640-5328) of the TP53 gene revealed MRC5 had more mutations than MRC5 SV2 cells (n = 21 and 11 respectively) and that they were predominantly insertions (MRC5 81%, MRC5 SV2 100%). A common mutation was observed in both cell lines; a G insertion at residue 4724 (n = 7) which could prove to be a mutational hotspot. These results indicate that the transformed cells are slower to respond to oxidative stress and/or mutagenic compounds. The mutation spectrum of predominantly frameshift mutations (insertions) suggests that oxidative stress plays a minimal role in smoking related lung cancer, but could be of greater importance to other lung diseases and cancer caused by exposures such as passive smokers, passive vapers and atmospheric pollutants.

Uncovering a unique approach for damaged DNA replication: A computational investigation of a mutagenic tobacco-derived thymine lesion

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone is a potent nicotine carcinogen that leads to many DNA lesions, the most persistent being the O2-[4-oxo-4-(3-pyridyl)butyl]thymine adduct (POB-T). Although the experimental mutagenic profile for the minor groove POB-T lesion has been previously reported, the findings are puzzling in terms of the human polymerases involved. Specifically, while pol κ typically replicates minor groove adducts, in vivo studies indicate pol η replicates POB-T despite being known for processing major groove adducts. Our multiscale modeling approach reveals that the canonical (anti) glycosidic orientation of POB-T can fit in the pol κ active site, but only a unique (syn) POB-T conformation is accommodated by pol η. These distinct binding orientations rationalize the differential in vitro mutagenic spectra based on the preferential stabilization of dGTP and dTTP opposite the lesion for pol κ and η, respectively. Overall, by uncovering the first evidence for the replication of a damaged pyrimidine in the syn glycosidic orientation, the current work provides the insight necessary to clarify a discrepancy in the DNA replication literature, expand the biological role of the critical human pol η, and understand the mutational signature in human cancers associated with tobacco exposure.

Microbial metabolites of proanthocyanidins reduce chemical carcinogen-induced DNA damage in human lung epithelial and fetal hepatic cells in vitro

Seven selected microbial metabolites of proanthocyanidins (MMP), 3-phenylpropionic, 4-hydroxyphenyl acetic, 3-(4-hydroxyphenyl) propionic, p-coumaric, benzoic acid, pyrogallol (PG), and pyrocatechol (PC) were evaluated for their ability to reduce chemical carcinogen-induced toxicity in human lung epithelial cells (BEAS-2B) and human fetal hepatic cells (WRL-68). Cells pre-treated with MMP were exposed to a known chemical carcinogen, 4-[(acetoxymethyl) nitrosamino]-1-(3-pyridyl)-1-butanone (NNKOAc) to assess MMP-mediated cytoprotection and reduction of DNA damage. PG in BEAS-2B and PC in WRL-68 cells mitigated the NNKOAc-induced cytotoxicity. Pre-incubation of PG depicted significant protection against NNKOAc-induced DNA damage in BEAS-2B cells. PC in WRL-68 cells showed similar activity. To understand the mechanisms of PG- and PC-mediated DNA damage reduction, the effect on DNA damage response (DDR) proteins, cellular reactive oxygen species (ROS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and caspase activity were studied. PG and PC alter the DDR and may promote ATR-Chk1 and ATM-Chk2 pathways, respectively. Cellular oxidative stress induced by NNKOAc was mitigated by PG and PC through enhanced GPx expression and TAC. PG and PC suppressed the activation of the extrinsic apoptotic pathway (caspase 3 and 8) provoked by NNKOAc. MMP are beneficial in chemoprevention by reducing cellular DNA damage.

Urinary Biomarkers of Carcinogenic Exposure among Cigarette, Waterpipe, and Smokeless Tobacco Users and Never Users of Tobacco in the Golestan Cohort Study

BACKGROUND

How carcinogen exposure varies across users of different, particularly noncigarette, tobacco products remains poorly understood.

METHODS

We randomly selected 165 participants of the Golestan Cohort Study from northeastern Iran: 60 never users of any tobacco, 35 exclusive cigarette, 40 exclusive (78% daily) waterpipe, and 30 exclusive smokeless tobacco (nass) users. We measured concentrations of 39 biomarkers of exposure in 4 chemical classes in baseline urine samples: tobacco alkaloids, tobacco-specific nitrosamines (TSNA), polycyclic aromatic hydrocarbons (PAH), and volatile organic compounds (VOC). We also quantified the same biomarkers in a second urine sample, obtained 5 years later, among continuing cigarette smokers and never tobacco users.

RESULTS

Nass users had the highest concentrations of tobacco alkaloids. All tobacco users had elevated TSNA concentrations, which correlated with nicotine dose. In both cigarette and waterpipe smokers, PAH and VOC biomarkers were higher than never tobacco users and nass users, and highly correlated with nicotine dose. PAH biomarkers of phenanthrene and pyrene and two VOC metabolites (phenylmercapturic acid and phenylglyoxylic acid) were higher in waterpipe smokers than in all other groups. PAH biomarkers among Golestan never tobacco users were comparable to those in U.S. cigarette smokers. All biomarkers had moderate to good correlations over 5 years, particularly in continuing cigarette smokers.

CONCLUSIONS

We observed two patterns of exposure biomarkers that differentiated the use of the combustible products (cigarettes and waterpipe) from the smokeless product. Environmental exposure from nontobacco sources appeared to contribute to the presence of high levels of PAH metabolites in the Golestan Cohort.

IMPACT

Most of these biomarkers would be useful for exposure assessment in a longitudinal study.

Computational insights into the mutagenicity of two tobacco-derived carcinogenic DNA lesions

4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone is a potent carcinogen found in all tobacco products that leads to a variety of DNA lesions in cells, including O6-[4-oxo-4-(3-pyridyl)butyl]guanine (POB-G) and O6-[4-hydroxy-4-(3-pyridyl)butyl]guanine (PHB-G), which differ by only a single substituent in the bulky moiety. This work uses a multiscale computational approach to shed light on the intrinsic conformational and base-pairing preferences of POB-G and PHB-G, and the corresponding properties in DNA and the polymerase η active site. Our calculations reveal that both lesions form stable pairs with C and T, with the T pairs being the least distorted relative to canonical DNA. This rationalizes the experimentally reported mutational profile for POB-G and validates our computational model. The same approach predicts that PHB-G is more mutagenic than POB-G due to a difference in the bulky moiety hydrogen-bonding pattern, which increases the stability of the PHB-G:T pair. The mutagenicity of PHB-G is likely further increased by stabilization of an intercalated DNA conformation that is associated with deletion mutations. This work thereby uncovers structural explanations for the reported mutagenicity of POB-G, provides the first clues regarding the mutagenicity of PHB-G and complements a growing body of literature highlighting that subtle chemical changes can affect the biological outcomes of DNA adducts.

Development and validation of a method for quantification of two tobacco-specific nitrosamines in indoor air

A sensitive and accurate method for the quantification of 1'-Demethyl-1'-nitrosonicotine (NNN) and 4-(methylnitrosamino)-1-(3-Pyridyl)-1-butanone (NNK) in indoor air was developed and validated. To this aim, a novel approach for the collection of two tobacco-specific nitrosamines, using silica sorbent cartridges followed by simplified sample preparation and isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry, was applied. This procedure led to a substantial improvement in terms of sensitivity and sample throughput as compared with methods using conventional trapping. For the validation, a matrix-based approach using an accuracy profile procedure was selected. The evaluated matrices were background air samples, environmental aerosols of a heat-not-burn tobacco product (Tobacco Heating System [THS] 2.2, commercialized under the brand IQOS®), a rechargeable electronic cigarette (Solaris®), and the environmental tobacco smoke (ETS) of a conventional cigarette (Marlboro Gold®). The method showed excellent recoveries, sensitivity, and precision. The limits of detection of the method for NNN and NNK were 0.0108 ng/m3 and 0.0136 ng/m3, respectively. The calibration range of the instrument spanned 0.2-60 ng/mL. The calculated lower working range limit (LWRL) of the method for NNN was 0.126 ng/m3, and the LWRL for NNK was 0.195 ng/m3. The method was applied to evaluate surrogate environmental aerosols generated using smoking machines. This model is reliable but gives a large overestimation of the possible impact of THS 2.2 and e-cigarettes on indoor air, because the retention of NNN and NNK in the body of the consumers is not taken into account. As a consequence, the values reported do not reflect a real-life setting. The contents of the two target compounds in the surrogate environmental aerosols were 0.0830 ± 0.0153 ng/m3 of NNN and 0.0653 ± 0.0138 ng/m3 of NNK for THS 2.2, 0.0561 ± 0.0296 ng/m3 of NNN for e-cigarettes, and 0.816 ± 0.109 ng/m3 of NNN and 4.13 ± 1.04 ng/m3 NNK for cigarettes. These values correspond to 10% of the measured ETS concentration for NNN in environmental aerosols of THS 2.2 and 7% for those of e-cigarettes. For NNK, the value for the environmental aerosol of THS 2.2 was 2% of the ETS value.