Recent studies on mechanisms of bioactivation and detoxification of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific lung carcinogen

Long Noncoding RNA PSMB8-AS1 Mediates the Tobacco-Carcinogen-Induced Transformation of a Human Bronchial Epithelial Cell Line by Regulating Cell Cycle

Lung cancer is the main cause of cancer deaths around the world. Nitrosamine 4-(methyl nitrosamine)-1-(3-pyridyl)-1-butanone (NNK) is a tobacco-specific carcinogen of lung cancer. Abundant evidence implicates long noncoding RNAs (lncRNAs) in tumorigenesis. Yet, the effects and mechanisms of lncRNAs in NNK-induced carcinogenesis are still unclear. In this study, we discovered that NNK-induced transformed Beas-2B cells (Beas-2B-NNK) showed increased cell migration and proliferation while decreasing rates of apoptosis. RNA sequencing and differentially expressed lncRNAs analyses showed that lncRNA PSMB8-AS1 was obviously upregulated. Interestingly, silencing the lncRNA PSMB8-AS1 in Beas-2B-NNK cells reduced cell proliferation and migration and produced cell cycle arrest in the G2/M phase along with a decrease in CDK1 expression. Conclusively, our results demonstrate that lncRNA PSMB8-AS1 could promote the malignant characteristics of Beas-2B-NNK cells by regulating CDK1 and affecting the cell cycle, suggesting that it may supply a new prospective epigenetic mechanism for lung cancer.

The ADAM17 protease promotes tobacco smoke carcinogen-induced lung tumorigenesis

Lung cancer is the leading cause of cancer-related mortality, with most cases attributed to tobacco smoking, in which nicotine-derived nitrosamine ketone (NNK) is the most potent lung carcinogen. The ADAM17 protease is responsible for the ectodomain shedding of many pro-tumorigenic cytokines, growth factors and receptors, and therefore is an attractive target in cancer. However, the role of ADAM17 in promoting tobacco smoke carcinogen-induced lung carcinogenesis is unknown. The hypomorphic Adam17ex/ex mice-characterized by reduced global ADAM17 expression-were backcrossed onto the NNK-sensitive pseudo-A/J background. CRISPR-driven and inhibitor-based (GW280264X, and ADAM17 prodomain) ADAM17 targeting was employed in the human lung adenocarcinoma cell lines A549 and NCI-H23. Human lung cancer biopsies were also used for analyses. The Adam17ex/ex mice displayed marked protection against NNK-induced lung adenocarcinoma. Specifically, the number and size of lung lesions in NNK-treated pseudo-A/J Adam17ex/ex mice were significantly reduced compared with wild-type littermate controls. This was associated with lower proliferative index throughout the lung epithelium. ADAM17 targeting in A549 and NCI-H23 cells led to reduced proliferative and colony-forming capacities. Notably, among select ADAM17 substrates, ADAM17 deficiency abrogated shedding of the soluble IL-6 receptor (sIL-6R), which coincided with the blockade of sIL-6R-mediated trans-signaling via ERK MAPK cascade. Furthermore, NNK upregulated phosphorylation of p38 MAPK, whose pharmacological inhibition suppressed ADAM17 threonine phosphorylation. Importantly, ADAM17 threonine phosphorylation was significantly upregulated in human lung adenocarcinoma with smoking history compared with their cancer-free controls. Our study identifies the ADAM17/sIL-6R/ERK MAPK axis as a candidate therapeutic strategy against tobacco smoke-associated lung carcinogenesis.

ADAM17: An Emerging Therapeutic Target for Lung Cancer

Lung cancer is the leading cause of cancer-related mortality, which histologically is classified into small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC accounts for approximately 85% of all lung cancer diagnoses, with the majority of patients presenting with lung adenocarcinoma (LAC). KRAS mutations are a major driver of LAC, and are closely related to cigarette smoking, unlike mutations in the epidermal growth factor receptor (EGFR) which arise in never-smokers. Although the past two decades have seen fundamental progress in the treatment and diagnosis of NSCLC, NSCLC still is predominantly diagnosed at an advanced stage when therapeutic interventions are mostly palliative. A disintegrin and metalloproteinase 17 (ADAM17), also known as tumour necrosis factor-α (TNFα)-converting enzyme (TACE), is responsible for the protease-driven shedding of more than 70 membrane-tethered cytokines, growth factors and cell surface receptors. Among these, the soluble interleukin-6 receptor (sIL-6R), which drives pro-inflammatory and pro-tumourigenic IL-6 trans-signaling, along with several EGFR family ligands, are the best characterised. This large repertoire of substrates processed by ADAM17 places it as a pivotal orchestrator of a myriad of physiological and pathological processes associated with the initiation and/or progression of cancer, such as cell proliferation, survival, regeneration, differentiation and inflammation. In this review, we discuss recent research implicating ADAM17 as a key player in the development of LAC, and highlight the potential of ADAM17 inhibition as a promising therapeutic strategy to tackle this deadly malignancy.

Comparison of Chemicals in Mainstream Smoke in Heat-not-burn Tobacco and Combustion Cigarettes

Because of the health effects of secondhand smoke, the Japanese government is trying to establish an effective law for total avoidance of secondhand smoke in indoor environments for tobacco-free Tokyo Olympic and Paralympic games 2020, as requested by the International Olympic Committee (IOC) and the World Health Organization (WHO). Meanwhile, Philip Morris International has begun selling a new heat-not-burn tobacco, iQOS, which it claims is designed not to produce secondhand smoke. There is little scientific data, however, of the hazards and toxicity of iQOS. In this study, we evaluated several harmful compounds (nicotine, tar, carbon monoxide (CO) and tobacco-specific nitrosamines (TSNAs)) in the mainstream smoke and fillers of iQOS, and compared their concentrations with those from conventional combustion cigarettes. The concentrations of nicotine in tobacco fillers and the mainstream smoke of iQOS were almost the same as those of conventional combustion cigarettes, while the concentration of TSNAs was one fifth and CO was one hundredth of those of conventional combustion cigarettes. These toxic compounds are not completely removed from the mainstream smoke of iQOS, making it necessary to consider the health effects and regulation of iQOS.

β2-adrenogenic signaling regulates NNK-induced pancreatic cancer progression via upregulation of HIF-1α

Cigarette smoking is a risk factor for pancreatic cancer. It is suggested that 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific nitrosamine, mediates the carcinogenic action of cigarette smoking by promoting cancer growth. In the present study, we show that smoking, HIF-1α expression and β2-adrenogenic receptor (β2-AR) expression are negatively correlated with the overall survival of pancreatic cancer patients. Moreover, HIF-1α expression and β2-AR expression are positively correlated with smoking status, different histological differentiation and among the tumor node metastasis (TNM) stages in pancreatic cancer patients. NNK increases HIF-1α expression in pancreatic cancer in vitro and in vivo. Furthermore, knockdown of HIF-1α and ICI118, 551 (a β2-AR selective antagonist) abrogates NNK-induced pancreatic cancer proliferation and invasion in vitro and inhibits NNK-induced pancreatic cancer growth in vivo. However, using CoCl2 (a HIF-1α stabilizing agent which decreases HIF-1α degradation under normoxia conditions) reverses ICI118, 551 induced effects under NNK exposure. Thus, our data indicate that β2-AR signaling regulates NNK-induced pancreatic cancer progression via upregulation of HIF-1α. Taken together, β2-AR signaling and HIF-1α may represent promising therapeutic targets for preventing smoking induced pancreatic cancer progression.

Association between Secondhand Smoke in Hospitality Venues and Urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol Concentrations in Non-Smoking Staff

The purpose of this study was to determine the relationship between urinary cotinine and total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) concentrations in non-smoking staff and the indoor levels of fine particles (PM_2.5) in hospitality venues that allow smoking, with respect to demographic and indoor environmental factors. We evaluated 62 hospitality venues that allowed smoking in Seoul, Korea. A real-time aerosol monitor was used to measure indoor PM_2.5 concentrations. Field technicians recorded indoor environmental characteristics. One non-smoking staff member in each hospitality venue was tested for urinary cotinine and total NNAL concentrations. Demographic characteristics were obtained from self-reported staff questionnaires. Natural-log (ln)-transformed PM_2.5 concentrations were significantly correlated with the ln-transformed cotinine (r = 0.31) and the total NNAL concentrations (r = 0.32). In multivariable regression analysis, the urinary cotinine concentrations of the staff members were significantly correlated with indoor PM_2.5 concentrations; those with the highest concentrations were more likely to be women or staff members that worked in venues with a volume <375 m³. Total NNAL concentrations were significantly correlated only with indoor PM_2.5 concentrations. Indoor PM_2.5 may be used as an indicator for urinary cotinine and total NNAL concentrations in non-smoking staff members in hospitality venues that allow smoking.

Air Quality, Biomarker Levels, and Health Effects on Staff in Korean Restaurants and Pubs Before and After a Smoking Ban

INTRODUCTION

The Korean government implemented a smoking ban at square floor area of ≥150 m(2), rather than <150 m(2), restaurants and pubs from July 2013. This study examined the effects of the smoking regulations in restaurants and pubs in terms of the air quality, biomarker levels and health effects on staff.

METHODS

Particulate matter smaller than 2.5 µm (PM2.5) was measured in 146 facilities before and 1 month after the ban. The urinary cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanol (NNAL) levels were measured in 101 staff members at 77 facilities before and 1 month after the ban. We also measured self-reported respiratory and sensory symptoms on both phases.

RESULTS

Of the 146 facilities, 121 facilities were included in the PM2.5 analysis. In ≥150 m(2) pubs, the indoor PM2.5 concentration was significantly reduced after the ban (p < .05). While the urinary cotinine concentrations of the staff in all facilities were not changed after the ban, the total NNAL concentrations of the staff in ≥150 m(2) pubs were significantly reduced after the ban (p < .05). The health effects on staff show that only sensory symptoms significantly improved in ≥150 m(2) facilities after the ban (p < .05).

CONCLUSIONS

The smoking ban significantly reduced the levels of PM2.5 and total NNAL concentrations in ≥150 m(2) pubs and improved sensory health among staff in ≥150 m(2) facilities. The results of this study can be useful in supporting an expansion of the smoking ban in all indoor places, including <150 m(2) restaurants and pubs.

Breath analysis as a potential and non-invasive frontier in disease diagnosis: an overview

Currently, a small number of diseases, particularly cardiovascular (CVDs), oncologic (ODs), neurodegenerative (NDDs), chronic respiratory diseases, as well as diabetes, form a severe burden to most of the countries worldwide. Hence, there is an urgent need for development of efficient diagnostic tools, particularly those enabling reliable detection of diseases, at their early stages, preferably using non-invasive approaches. Breath analysis is a non-invasive approach relying only on the characterisation of volatile composition of the exhaled breath (EB) that in turn reflects the volatile composition of the bloodstream and airways and therefore the status and condition of the whole organism metabolism. Advanced sampling procedures (solid-phase and needle traps microextraction) coupled with modern analytical technologies (proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry, ion mobility spectrometry, e-noses, etc.) allow the characterisation of EB composition to an unprecedented level. However, a key challenge in EB analysis is the proper statistical analysis and interpretation of the large and heterogeneous datasets obtained from EB research. There is no standard statistical framework/protocol yet available in literature that can be used for EB data analysis towards discovery of biomarkers for use in a typical clinical setup. Nevertheless, EB analysis has immense potential towards development of biomarkers for the early disease diagnosis of diseases.

Chronic exposure to combined carcinogens enhances breast cell carcinogenesis with mesenchymal and stem-like cell properties

Breast cancer is the most common type of cancer affecting women in North America and Europe. More than 85% of breast cancers are sporadic and attributable to long-term exposure to small quantities of multiple carcinogens. To understand how multiple carcinogens act together to induce cellular carcinogenesis, we studied the activity of environmental carcinogens 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), and dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using our breast cell carcinogenesis model. Our study revealed, for the first time, that combined NNK and B[a]P enhanced breast cell carcinogenesis chronically induced by PhIP in both non-cancerous and cancerous breast cells. Co-exposure was more potent than sequential exposure to combined NNK and B[a]P followed by PhIP in inducing carcinogenesis. Initiation of carcinogenesis was measured by transient endpoints induced in a single exposure, while progression of carcinogenesis was measured by acquisition of constitutive endpoints in cumulative exposures. Transient endpoints included DNA damage, Ras-Erk-Nox pathway activation, reactive oxygen species elevation, and increased cellular proliferation. Constitutive endpoints included various cancer-associated properties and signaling modulators, as well as enrichment of cancer stem-like cell population and activation of the epithelial-to-mesenchymal transition program. Using transient and constitutive endpoints as targets, we detected that a combination of the green tea catechins ECG and EGCG, at non-cytotoxic levels, was more effective than individual agents in intervention of cellular carcinogenesis induced by combined NNK, B[a]P, and PhIP. Thus, use of combined ECG and EGCG should be seriously considered for early intervention of breast cell carcinogenesis associated with long-term exposure to environmental and dietary carcinogens.

Cigarette smoking and gastrointestinal diseases: the causal relationship and underlying molecular mechanisms (review)

Cigarette smoking is an important risk factor for gastrointestinal (GI) disorders, including peptic ulcers, inflammatory bowel diseases, such as Crohn's disease and cancer. In this review, the relationship between smoking and GI disorders and the underlying mechanisms are discussed. It has been demonstrated that cigarette smoking is positively associated with the pathogenesis of peptic ulcers and the delay of ulcer healing. Mechanistic studies have shown that cigarette smoke and its active ingredients can cause mucosal cell death, inhibit cell renewal, decrease blood flow in the GI mucosa and interfere with the mucosal immune system. Cigarette smoking is also an independent risk factor for various types of cancer of the GI tract. In this review, we also summarize the mechanisms through which cigarette smoking induces tumorigenesis and promotes the development of cancer in various sections of the GI tract. These mechanisms include the activation of nicotinic acetylcholine receptors, the formation of DNA adducts, the stimulation of tumor angiogenesis and the modulation of immune responses in the GI mucosa. A full understanding of these pathogenic mechanisms may help us to develop more effective therapies for GI disorders in the future.

Mesenchymal and stem-like cell properties targeted in suppression of chronically-induced breast cell carcinogenesis

Stem-like cells and the epithelial-to-mesenchymal transition (EMT) program are postulated to play important roles in various stages of cancer development, but their roles in breast cell carcinogenesis and intervention remain to be clarified. We investigated stem-like cell- and EMT-associated properties and markers in breast epithelial cells chronically exposed to low-dose 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and benzo[a]pyrene in the presence and absence of the preventive agents green tea catechins and grape seed extract. Our results indicate that stem-like cell- and EMT-associated properties and markers should be seriously considered as new cancer-associated indicators for detecting breast cell carcinogenesis and as endpoints for intervention of carcinogenesis.

Exposure to secondhand smoke outside of a bar and a restaurant and tobacco exposure biomarkers in nonsmokers

BACKGROUND

With an increase in indoor smoking bans, many smokers smoke outside establishments and near their entrances, which has become a public health concern.

OBJECTIVES

We characterized the exposure of nonsmokers to secondhand smoke (SHS) outside a restaurant and bar in Athens, Georgia, where indoor smoking is banned, using salivary cotinine and urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL).

METHODS

In a crossover study, we assigned 28 participants to outdoor patios of a restaurant and a bar and an open-air site with no smokers on three weekend days; participants visited each site once and stayed for 3 hr. We collected saliva and urine samples immediately before and after the visits (postexposure) and on the following morning and analyzed samples for cotinine and total NNAL, respectively. Regression models were fitted and changes in biomarkers were contrasted between locations.

RESULTS

Postexposure and preexposure geometric mean salivary cotinine concentrations differed by 0.115 ng/mL [95% confidence interval (CI): 0.105, 0.126)] and by 0.030 ng/mL (95% CI: 0.028, 0.031) for bar and restaurant visits, respectively. There were no significant post- and preexposure differences in cotinine levels after control site visits, and changes after bar and restaurant site visits were significantly different from changes after control site visits (p < 0.001). Results comparing next-day and preexposure salivary cotinine levels were similar. Next-day creatinine-corrected urinary NNAL concentrations also were higher than preexposure levels following bar and restaurant visits [1.858 pg/mg creatinine higher (95% CI: 0.897, 3.758) and 0.615 pg/mg creatinine higher (95% CI: 0.210, 1.761), respectively], and were significantly different from changes after the control visits (p = 0.005).

CONCLUSION

Salivary cotinine and urinary NNAL increased significantly in nonsmokers after outdoor SHS exposure. Our findings indicate that such exposures may increase risks of health effects associated with tobacco carcinogens.

Green tea catechin intervention of reactive oxygen species-mediated ERK pathway activation and chronically induced breast cell carcinogenesis

Long-term exposure to low doses of environmental carcinogens contributes to sporadic human breast cancers. Epidemiologic and experimental studies indicate that green tea catechins (GTCs) may intervene with breast cancer development. We have been developing a chronically induced breast cell carcinogenesis model wherein we repeatedly expose non-cancerous, human breast epithelial MCF10A cells to bioachievable picomolar concentrations of environmental carcinogens, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P), to progressively induce cellular acquisition of cancer-associated properties, as measurable end points. The model is then used as a target to identify non-cytotoxic preventive agents effective in suppression of cellular carcinogenesis. Here, we demonstrate, for the first time, a two-step strategy that initially used end points that were transiently induced by short-term exposure to NNK and B[a]P as targets to detect GTCs capable of blocking the acquisition of cancer-associated properties and subsequently used end points constantly induced by long-term exposure to carcinogens as targets to verify GTCs capable of suppressing carcinogenesis. We detected that short-term exposure to NNK and B[a]P resulted in elevation of reactive oxygen species (ROS), leading to Raf-independent extracellular signal-regulated kinase (ERK) pathway activation and subsequent induction of cell proliferation and DNA damage. These GTCs, at non-cytotoxic levels, were able to suppress chronically induced cellular carcinogenesis by blocking carcinogen-induced ROS elevation, ERK activation, cell proliferation and DNA damage in each exposure cycle. Our model may help accelerate the identification of preventive agents to intervene in carcinogenesis induced by long-term exposure to environmental carcinogens, thereby safely and effectively reducing the health risk of sporadic breast cancer.

Green tea catechin extract in intervention of chronic breast cell carcinogenesis induced by environmental carcinogens

Sporadic breast cancers are mainly attributable to long-term exposure to environmental factors, via a multi-year, multi-step, and multi-path process of tumorigenesis involving cumulative genetic and epigenetic alterations in the chronic carcinogenesis of breast cells from a non-cancerous stage to precancerous and cancerous stages. Epidemiologic and experimental studies have suggested that green tea components may be used as preventive agents for breast cancer control. In our research, we have developed a cellular model that mimics breast cell carcinogenesis chronically induced by cumulative exposures to low doses of environmental carcinogens. In this study, we used our chronic carcinogenesis model as a target system to investigate the activity of green tea catechin extract (GTC) at non-cytotoxic levels in intervention of cellular carcinogenesis induced by cumulative exposures to pico-molar 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (B[a]P). We identified that GTC, at a non-cytotoxic, physiologically achievable concentration of 2.5 µg/mL, was effective in suppressing NNK- and B[a]P-induced cellular carcinogenesis, as measured by reduction of the acquired cancer-associated properties of reduced dependence on growth factors, anchorage-independent growth, increased cell mobility, and acinar-conformational disruption. We also detected that intervention of carcinogen-induced elevation of reactive oxygen species (ROS), increase of cell proliferation, activation of the ERK pathway, DNA damage, and changes in gene expression may account for the mechanisms of GTC's preventive activity. Thus, GTC may be used in dietary and chemoprevention of breast cell carcinogenesis associated with long-term exposure to low doses of environmental carcinogens.

GABA (γ-aminobutyric acid), a non-protein amino acid counters the β-adrenergic cascade-activated oncogenic signaling in pancreatic cancer: a review of experimental evidence

GABA is a bioactive constituent of fruits, vegetables, cereals and is believed to play a role in defense against stress in plants. In animals, it acts as an inhibitory neurotransmitter in brain while also expressed in non-neuronal cells. Studies have implicated the regulator of fight or flight stress responses, β-AR signaling cascade, as mediators of cancer growth and progression in in vitro and in vivo models of pancreatic malignancies. Pancreatic cancer is the fourth leading cause of cancer mortality in western countries. This malignancy is generally unresponsive to conventional radio- and chemotherapy, resulting in mortality rate near 100% within 6 months of diagnosis. We review a series of experiments from our laboratory and those of others examining the contribution of this signaling network to pancreatic and other human malignancies. Stimulation of the β-adrenergic receptor by lifestyle and environmental factors, as well as a pre-existing risk of neoplasm, activates downstream effector molecules that lead to pro-oncogenic signaling and thereby aid cancer growth. GABAergic signaling mediated by the serpentine receptor GABA(B) acts as an antagonist to β-adrenergic cascade by intercepting adenylyl cyclase. These evidences enhance the pharmacological value of human diets rich in GABA for use as an adjuvant to standard therapies.

Effects of antibodies induced by a conjugate vaccine on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone absorptive transport, metabolism, and proliferation of human lung cells

One of the most abundant and potent lung carcinogen is the nicotine-derived tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The monoclonal antibody P9D5 induced with a NNK-conjugate vaccine was used to investigate the ability of NNK-specific antibodies to modulate NNK-induced adverse effects as well as its absorptive transport and metabolism in two lung cancer cell lines (Calu-3 and NCI-H82). Transport experiments in Calu-3 cells with a 50-fold molar excess of apical P9D5 increased the recovery of coadministered apical NNK, with a concomitant decrease in NNK transepithelial transport of more than 50% compared to controls. In contrast, basolateral P9D5 did neither influence transepithelial transport of NNK nor its disappearance from the apical compartment. Calu-3 cells were also found to reduce NNK to NNAL and a 65-fold molar excess of NNK-specific antibody inhibited this metabolic conversion by 46 and 54% compared to irrelevant control antibody after 48 and 72 hr, respectively. The biological relevance of NNK redistribution by antibody was demonstrated by reversion of NNK-induced cell proliferation in NCI-H82 cells. Repartitioning of tobacco carcinogens by antibody may reduce their early effective peak concentrations in susceptible target organs and thus relieve overloaded local DNA repair mechanisms and diminish carcinogen-induced cell proliferation. These in vitro data therefore suggest that a prophylactic antibody response may be associated with a reduced risk of cancer.

4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone [corrected] induces CRM1-dependent p53 nuclear accumulation in human bronchial epithelial cells

4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone [corrected] (NNK), a known tobacco-specific human lung carcinogen, is notorious for causing DNA damage. The tumor suppressor gene p53 has multiple functions in response to DNA damage. Besides being regulated by posttranslational modifications (PTMs), p53 function is modulated by nucleocytoplasmic shuttling factors (NSFs). In this study, the alterations of p53 protein after NNK exposure and the molecular mechanisms involved p53 PTMs and NSFs in human bronchial epithelial cells BEAS-2B were investigated. NNK induced p53 nuclear accumulation and upregulated the expression of p21, a p53 target gene. Among the five NSFs examined, chromosomal region maintenance 1 (CRM1), interacting with p53 and exporting p53 from nucleus to cytoplasm, was significantly downregulated after NNK exposure. Increases of p53 phosphorylation and poly(ADP-ribosyl)ation were found in NNK-treated cells as compared with the controls. The upregulation of p53 poly(ADP-ribosyl)ation was induced by the enhanced expression of poly(ADP-ribose) polymerase 1 after NNK exposure. Collectively, p53 went through PTMs in response to DNA damage, and the modified p53 had a tendency for nuclear accumulation, which could result from CRM1 downregulation. Consequently, the activation of p53 led to subsequent induction of its downstream targets. These data could facilitate the better understanding of chemical carcinogenesis induced by NNK.

Effect of allyl isothiocyanate (AITC) in both nitrite- and nitrosamine-induced cell death, production of reactive oxygen species, and DNA damage by the single-cell gel electrophoresis (SCGE): does it have any protective effect on HepG2 cells?

The current study was designed to investigate possible protective effect of allyl isothiocyanate (AITC) in nitrite- and nitrosamine-treated human hepatoma cells (HepG2) with the evaluation by cytotoxic effects and genotoxic effects determined by the single-cell gel electrophoresis (SCGE). Allyl isothiocyanate treatment enhanced cell viability and reduced intracellular reactive oxygen species (ROS) production in both nitrite- and nitrosamine-treated cells significantly. In SCGE, when compared to untreated control cells, all of the treated groups caused increases in the tail intensity (%) such as nitrite at 17%, N-nitrosodimethylamine (NDMA) at 279%, N-nitrosodiethylamine (NDEA) at 324%, and N-nitrosomorpholine (NMOR) at 288%. Allyl isothiocyanate reduced the tail intensity caused by nitrite 36%, by NDMA 36%, by NDEA 49%, and by NMOR 32%, respectively, when compared to each individual toxic compound-treated group. In conclusion, AITC protected HepG2 cells against cytotoxic and genotoxic effects caused by nitrite and the nitrosamines.

Arsenite promotes centrosome abnormalities under a p53 compromised status induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

Epidemiological evidence indicated that residents, especially cigarette smokers, in arseniasis areas had significantly higher lung cancer risk than those living in non-arseniasis areas. Thus an interaction between arsenite and cigarette smoking in lung carcinogenesis was suspected. In the present study, we investigated the interactions of a tobacco-specific carcinogen 4- (methylnitrosamino)-1-(3-pyridyl)-1-butanone (nicotine-derived nitrosamine ketone, NNK) and arsenite on lung cell transformation. BEAS-2B, an immortalized human lung epithelial cell line, was selected to test the centrosomal abnormalities and colony formation by NNK and arsenite. We found that NNK, alone, could enhance BEAS-2B cell growth at 1-5 microM. Under NNK exposure, arsenite was able to increase centrosomal abnormality as compared with NNK or arsenite treatment alone. NNK treatment could also reduce arsenite-induced G2/M cell cycle arrest and apoptosis, these cellular effects were found to be correlated with p53 dysfunction. Increased anchorage-independent growth (colony formation) of BEAS-2B cells cotreated with NNK and arsenite was also observed in soft agar. Our present investigation demonstrated that NNK could provide a p53 compromised status. Arsenite would act specifically on this p53 compromised status to induce centrosomal abnormality and colony formation. These findings provided strong evidence on the carcinogenic promotional role of arsenite under tobacco-specific carcinogen co-exposure.

Nicotinic receptor-associated modulation of stimulatory and inhibitory neurotransmitters in NNK-induced adenocarcinoma of the lungs and pancreas

Small airway-derived pulmonary adenocarcinoma (PAC) and pancreatic ductal adenocarcinoma (PDAC) are among the most common human cancers and smoking is a risk factor for both. Emerging research has identified cAMP signalling stimulated by the stress neurotransmitters adrenaline and noradrenaline as an important stimulator of adenocarcinomas, including PAC and PDAC. The nicotine-derived nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent mutagen and the most powerful tobacco carcinogen. NNK is also an agonist for nicotinic acetylcholine receptors (nAChRs). Using hamster models of NNK-induced PAC and PDAC, we have tested the hypothesis that in analogy to chronic effects of nicotine in the brain, NNK may modulate the alpha(7)- and alpha(4)beta(2)nAChRs, causing an increase in stress neurotransmitters and a decrease in the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Immunoassays showed a significant increase in serum adrenaline/noradrenaline and increased intracellular cAMP in the cellular fraction of blood of NNK-treated hamsters. Western blots on microdissected control small airway epithelia, alveolar epithelia, pancreatic islet and pancreatic duct epithelia, and from NNK-induced PACs and PDACs showed that the GABA-synthesizing enzyme glutamate decarboxylase 65 (GAD65) and GABA were suppressed in NNK-induced PACs and PDACs. In contrast, protein expression of the alpha(7)nAChR, alpha(4)nAChR as well as p-CREB and p-ERK1/2 were up-regulated. These findings suggest that NNK-induced alterations in regulatory nAChRs may contribute to the development of smoking-associated PAC and PDAC by disturbing the balance between cancer-stimulating and -inhibiting neurotransmitters.

A modified method for the determination of tobacco specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in human urine by solid phase extraction using a molecularly imprinted polymer and liquid chromatography tandem mass spectrometry

The work described in this paper represents an improvement over a previously published method for the determination of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in human urine by solid phase extraction on a molecularly imprinted polymer column coupled with HPLC and -MS/MS detection. The influence of ion suppression due to sample matrix effect was evaluated, and found to influence the response of NNAL. By changing the liquid chromatography conditions, the response for this method was enhanced approximately 25-fold through avoidance of ionization suppression that was found with a previously published method and sample throughput has been improved. The dynamic range of the assay extends from 20 to 2500 pg/mL with a mean r(2)>0.998. The lower limit of quantitation for the assay was 20 pg/mL despite the use of an inherently lower sensitivity instrument. The method was validated according to current FDA guidelines for bioanalytical method validations.

Genetic polymorphism in cytochrome P450 2D6 (CYP2D6): Population distribution of CYP2D6 activity

Cytochrome P-450 2D6 (CYP2D6) is involved in the metabolism of many therapeutic drugs even though the enzyme represents a small proportion of the total CYP content of human liver. In vivo phenotyping with probe drug substrates such as debrisoquine and dextromethorphan showed a clear separation between poor metabolizers (PM) and extensive metabolizers (EM). This polymorphism may affect susceptibility to environmental disease, as suggested by molecular epidemiologic studies that found an association between CYP2D6 metabolizer phenotype and cancer risk; however, this association is not consistent. There are only a few examples of CYP2D6 involvement in toxicant mechanism of action, but this has not been extensively studied. Gene probe studies documented a number of genetic polymorphisms that underlie CYP2D6 metabolizer phenotypes. The EM group carries the wild-type (*1) or active (*2) variant alleles, while the PM group carries the *3, *4, *5, or *6 alleles, all of which code for a protein that has lower or null CYP2D6 activity. The current analysis characterizes (a) influence of genotype on phenotype based upon in vivo metabolism studies of probe drugs and (b) frequency of the major genotypes in different population groups is also characterized. These data were then incorporated into Monte Carlo modeling to simulate population distributions of CYP2D6 activity. This analysis reproduced the bimodal distributions commonly seen in phenotyping studies of Caucasians and found extensive population variability in enzyme activity, as indicated by the 9- to 56-fold difference between the PM modal median and the total population median CYP2D6 activity. This substantial degree of interindividual variability in CYP function indicates that assessments involving CYP2D6 substrates need to consider the full distribution of enzyme activity in refining estimates of internal dose in health assessments of xenobiotics.

Carbonyl Reductases and Pluripotent Hydroxysteroid Dehydrogenases of the Short-chain Dehydrogenase/reductase Superfamily

Carbonyl reduction of aldehydes, ketones, and quinones to their corresponding hydroxy derivatives plays an important role in the phase I metabolism of many endogenous (biogenic aldehydes, steroids, prostaglandins, reactive lipid peroxidation products) and xenobiotic (pharmacologic drugs, carcinogens, toxicants) compounds. Carbonyl-reducing enzymes are grouped into two large protein superfamilies: the aldo-keto reductases (AKR) and the short-chain dehydrogenases/reductases (SDR). Whereas aldehyde reductase and aldose reductase are AKRs, several forms of carbonyl reductase belong to the SDRs. In addition, there exist a variety of pluripotent hydroxysteroid dehydrogenases (HSDs) of both superfamilies that specifically catalyze the oxidoreduction at different positions of the steroid nucleus and also catalyze, rather nonspecifically, the reductive metabolism of a great number of nonsteroidal carbonyl compounds. The present review summarizes recent findings on carbonyl reductases and pluripotent HSDs of the SDR protein superfamily.

Precancerous model of human breast epithelial cells induced by NNK for prevention

Epidemiological investigations have suggested that exposure to tobacco and environmental carcinogens increase the risk of developing human breast cancer. In light of the chronic exposure of human breast tissues to tobacco and environmental carcinogens, we have taken an approach of analyzing cellular changes of immortalized non-cancerous human breast epithelial MCF10A cells during the acquisition of cancerous properties induced by repeated exposure to the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) at a low concentration of 100 pM. We found that accumulated exposures of MCF10A cells to NNK result in progressive development of cellular carcinogenesis from a stage of immortalization to precancerous sub-stages of acquiring a reduced dependence on growth factors and acquiring anchorage-independent growth. Using Matrigel for MCF10A cells to form size-restricted acini, we detected that exposures to NNK resulted in altered acinar conformation. Analysis of gene expression profiles by cDNA microarrays revealed up- and down-regulated genes associated with NNK-induced carcinogenesis. Using this cellular carcinogenesis model as a target system to identify anticancer agents, we detected that grape seed proanthocyanadin extract significantly suppressed NNK-induced carcinogenesis of MCF10A cells. Our studies provide a carcinogenesis-cellular model mimicking the accumulative exposure to carcinogens in the progression of human breast epithelial cells to increasingly acquire cancerous properties, as likely occurs in the development of precancerous human breast cells. Our cellular model also serves as a cost-efficient, in vitro system to identify preventive agents that inhibit human breast cell carcinogenesis induced by chronic exposures to carcinogens.

[Tobacco and morphology: pulmonary diseases]

Tobacco is implicated in multisystemic carcinogenesis through more than fifty identified carcinogenic metabolites that produce mutations responsible for alterations in cell cycle, immune response and endocrine regulation. Is one of nine risk factors identified in one third of cancer deaths together with obesity, sedentary, alcohol consumption, sexual promiscuity, drug addiction, and open and closed air contamination. Answering for cardiovascular diseases as the first cause of death in civilized world, tobacco is also pointed as the major factor implicated in the development of COPD (chronic obstructive pulmonary disease), RB-ILD (respiratory bronchiolitis and interstitial lung disease), DIP (desquamative interstitial pneumonia), bronchiolitis and bronchiolocentric interstitial fibrosis, Langerhans cells histiocytosis, eosinophilic pneumonia, sarcoidosis, epidermoid metaplasia in respiratory epithelium and lung cancer. The chronic tobacco induced inflammatory state is the basis for the acquisition of genetic alterations dependent on the tobacco contaminants.

Nitrosamines as nicotinic receptor ligands

Nitrosamines are carcinogens formed in the mammalian organism from amine precursors contained in food, beverages, cosmetics and drugs. The potent carcinogen, NNK, and the weaker carcinogen, NNN, are nitrosamines formed from nicotine. Metabolites of the nitrosamines react with DNA to form adducts responsible for genotoxic effects. We have identified NNK as a high affinity agonist for the alpha7 nicotinic acetylcholine receptor (alpha7nAChR) whereas NNN bound with high affinity to epibatidine-sensitive nAChRs. Diethylnitrosamine (DEN) bound to both receptors but with lower affinity. High levels of the alpha7nAChR were expressed in human small cell lung cancer (SCLC) cell lines and in hamster pulmonary neuroendocrine cells (PNECs), which serve as a model for the cell of origin of human SCLC. Exposure of SCLC or PNECs to NNK or nicotine increased expression of the alpha7nAChR and caused influx of Ca(2+), activation of PKC, Raf-1, ERK1/2, and c-myc, resulting in the stimulation of cell proliferation. Signaling via the alpha7nAChR was enhanced when cells were maintained in an environment of 10-15% CO(2) similar to that in the diseased lung. Hamsters with hyperoxia-induced pulmonary fibrosis developed neuroendocrine lung carcinomas similar to human SCLC when treated with NNK, DEN, or nicotine. The development of the NNK-induced tumors was prevented by green tea or theophylline. The beta-adrenergic receptor agonist, isoproterenol or theophylline blocked NNK-induced cell proliferation in vitro. NNK and nicotine-induced hyperactivity of the alpha7nAChR/RAF/ERK1/2 pathway thus appears to play a crucial role in the development of SCLC in smokers and could be targeted for cancer prevention.

NNK activates ERK1/2 and CREB/ATF-1 via beta-1-AR and EGFR signaling in human lung adenocarcinoma and small airway epithelial cells

We have shown that the tobacco nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is an agonist for -adrenergic receptors (beta-ARs) and increased DNA synthesis of human lung adenocarcinoma cells with features of bronchiolar Clara cells by binding to these receptors. Using a cell line derived from a human pulmonary adenocarcinoma with Clara cell phenotype (PACC) and immortalized human small airway epithelial cells (HPLD1), the putative cells of origin of this cancer type, our current studies have analyzed signaling initiated by binding of NNK to the beta 1-AR. NNK upregulated ERK1/2 and CREB/ATF-1 phosphorylation in a PKA-dependent manner in both cell lines. This response was further increased by transient overexpression of the beta 1-AR. Pre-exposure of cells to the selective beta 1-AR antagonist, atenolol, attenuated the stimulatory effects of NNK, suggesting the latter upregulated ERK1/2 and CREB/ATF-1 via this receptor. In vivo labeling and immunoprecipitation assays revealed that NNK phosphorylated the epidermal growth factor receptor (EGFR) at tyrosine residues, 991, 1068 and 1173, an effect inhibited by atenolol. The inhibitor of EGFR-specific tyrosine kinases, AG1478, reduced NNK ability to stimulate ERK1/2 and CREB/ATF-1. Genomic analysis of the exons 18-21 of the EGFR genes showed that no mutations were present in either gene. Collectively, our data provide evidence, for the first time, that NNK targets ERK1/2 and CREB/ATF-1 proteins via dual signaling involving beta 1-AR and EGFR pathways in PACCs and their putative cells of origin.

De minimus non curat lex--virtual thresholds for cancer initiation by tobacco specific nitrosamines--prospects for harm reduction by smokeless tobacco

Whereas the impact of tobacco specific nitrosamines in smokers is obscured by the presence of numerous other carcinogens and promoters, for smokeless tobacco virtually all the carcinogenic potential is associated with 4-(nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). In some countries exposure to smokeless tobacco with extremely high nitrosamine concentrations have been found to induce cancers in the head-neck region, whereas three recent large epidemiological studies failed to detect any such risk with respect to Swedish low-nitrosamine snuff. This review deals with quantitative aspects of DNA adduct formation from NNN and NNK in relation to the background levels ubiquitously found in healthy humans without known exposures to either tobacco or alkylating agents. The lack of significant increases of pro-mutagenic O6-methylations and DNA pyridyloxobutylations seen in smokers, as well as the negative outcome of the Swedish epidemiological studies, can be expected on basis of extrapolation of the dose response relationships found in rodents to actual exposures to NNK and NNN in Swedish snuff or from smoking. Sweden has the lowest prevalence of male smokers and smoking related diseases in the Western World, which has been ascribed to the fact that more than 20% of the grown up male population uses snuff. Smokeless tobacco represents an inexpensive and effective alternative to nicotine delivering products like nicotine patch, spray or gum. Considering that all other tobacco products are freely marketed, the ban on low-nitrosamine snuff in all countries in EU except Sweden is difficult to defend on either medical or ethical grounds.

Chemopreventive effect of saponins derived from roots ofPlatycodon grandiflorum on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in A/J mice

This study examined the chemopreventive effect of saponins that were isolated from the roots of Platycodon grandiflorum A. DC (Campanulaceae), Changkil saponins (CKS), against the tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), -on lung tumorigenesis in A/J mice. The mice were treated with a single NNK dose (100 mg/kg b.w., i.p.). CKS (0.5, 1,4 mg/kg body wt.) was administered orally daily for 3 days/week beginning 1 day after the NNK treatment and was maintained throughout the experiment. The administration of CKS suppressed the NNK-induced increase in the level of proliferating cell nuclear antigen, which are a marker of cell proliferation, in the lungs of the mice 4 weeks after the NNK injection. Twenty-five weeks after the NNK treatment, the mice were sacrificed and the number of surface lung tumors was measured. CKS significantly reduced the number of lung tumors induced by NNK in a dose dependent manner. These results suggest that CKS suppresses the development of lung tumors and has a chemopreventive effect against NNK-induced mouse lung tumorigenesis.

Ethanol and the tobacco-specific carcinogen, NNK, contribute to signaling in immortalized human pancreatic duct epithelial cells

OBJECTIVES

Smoking is a well-documented risk factor for pancreatic cancer. The tobacco-specific nitrosamine, NNK (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanone), significantly induces pancreatic ductal adenocarcinomas in laboratory rodents. Recent observations suggest that ethanol enhances the tumorigenic effects of smoking. Ethanol consumption is associated with the development of chronic pancreatitis, also considered a predisposing factor for pancreatic ductal adenocarcinoma. Because the precise role of ethanol in pancreatic carcinogenesis is not known, this study sought to elucidate the cumulative effects of ethanol and NNK on particular signal transduction pathways that might play a role in cell proliferation in immortalized human pancreatic duct epithelial cells.

METHODS

The HPDE6-c7 cells are developed from pancreatic duct epithelial cells, which are the putative cells of origin of pancreatic ductal adenocarcinoma. Cell proliferation assays, Western blot, and cyclic adenosine monophosphate assays were used to demonstrate the effects of ethanol and NNK treatments on these cells.

RESULTS

Ethanol cotreatments enhanced the NNK-induced proliferation of these cells. This response was inhibited by the adenylyl cyclase, protein kinase A, mitogen-activated protein kinase (p42/p44), and epidermal growth factor receptor-specific tyrosine kinase inhibitors. Cotreatments of NNK and ethanol also increased cyclic adenosine monophosphate accumulation, cAMP response element-binding family of proteins and mitogen-activated protein kinase phosphorylation, and protein kinase A activation.

CONCLUSIONS

These findings suggest a potential role for these pathways contributing to the development of smoking- and alcohol-related pancreatic carcinogenesis.

Flavonoids suppresses the enhancing effect of beta-carotene on DNA damage induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A549 cells

This study investigated the individual and combined effects of beta-carotene with a common flavonoid (naringin, quercetin or rutin) on DNA damage induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a potent tobacco-related carcinogen in human. A human lung cancer cell line, A549, was pre-incubated with beta-carotene, a flavonoid, or both for 1h followed by incubation with NNK for 4 h. Then, we determined DNA strand breaks and the level of 7-methylguanine (7-mGua), a product of NNK metabolism by cytochrome P450 (CYP). We showed that beta-carotene at 20 microM significantly enhanced NNK-induced DNA strand breaks and 7-mGua levels by 90% (p < 0.05) and 70% (p < 0.05), respectively, and that the effect of beta-carotene was associated with an increased metabolism of NNK by CYP because the concomitant addition of 1-aminobenzotriazole, a CYP inhibitor, with beta-carotene to cells strongly inhibited NNK-induced DNA strand breaks. In contrast to beta-carotene, incubation of cells with naringin, quercetin or rutin added at 23 microM led to significant inhibition of NNK-induced DNA strand breaks, and the effect was in the order of quercetin > naringin > rutin. However, these flavonoids did not significantly affect the level of 7-mGua induced by NNK. Co-incubation of beta-carotene with any of these flavonoids significantly inhibited the enhancing effect of beta-carotene on NNK-induced DNA strand breaks; the effects of flavonoids were dose-dependent and were also in the order of quercetin > naringin > rutin. Co-incubation of beta-carotene with any of these flavonoids also significantly inhibited the loss of beta-carotene incorporated into the cells, and the effects of the flavonoids were also in the order of quercetin > naringin > rutin. The protective effects of these flavonoids may be attributed to their antioxidant activities because they significantly decreased intracellular ROS, and the effects were also in the order of quercetin > naringin > rutin. These in vitro results suggest that a combination of beta-carotene with naringin, rutin, or quercetin may increase the safety of beta-carotene.

The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone stimulates proliferation of immortalized human pancreatic duct epithelia through beta-adrenergic transactivation of EGF receptors

PURPOSE

Pancreatic ductal adenocarcinoma is an aggressive smoking-associated human cancer in both men and women. The nicotine-derived 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is thought to contribute to the development of these neoplasms in smokers through genotoxic effects. However, NNK has been recently identified as an agonist for both beta(1)- and beta(2)-adrenergic receptors. Binding of NNK to these receptors stimulates proliferation of pulmonary and pancreatic adenocarcinomas cells in vitro and in hamster models. The goal of this study was to elucidate the NNK effects on the signal transduction pathways downstream of both beta(1)- and beta(2)-adrenergic receptors in immortalized human pancreatic HPDE6-c7 cells.

METHODS

The HPDE6-c7 cells are developed from normal pancreatic duct epithelial cells which are the putative cells of origin of pancreatic ductal adenocarcinoma. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cell proliferation assays, Western blot and cyclic AMP assays were employed to demonstrate the effects of NNK and other beta(1)- and beta(2)-adrenergic agonists and antagonist treatments on these cells.

RESULTS

MTT cell proliferation assays demonstrated that NNK and the classic beta-adrenergic agonist, isoproterenol, increased cell proliferation in HPDE6-c7 cells. Western blot and cyclic AMP assays demonstrated that NNK treatments also resulted in: (1) transactivation of the epidermal growth factor receptor, EGFR, (2) an increase in intracellular cyclic AMP accumulation, and (3) phosphorylation of mitogen-activated protein kinase, Erk1/2. The proliferative response to NNK and isoproterenol were inhibited by the use of beta-blockers (propranolol), and the inhibitors of adenylyl cyclase (SQ 22536), EGFR-specific tyrosine kinase (AG 1478) and Erk (PD 98059).

CONCLUSION

These findings suggest that the NNK -mediated beta-adrenergic receptor transactivation of the EGFR and phosphorylation of Erk1/2 in immortalized human pancreatic duct epithelial cells as a novel mechanism might contribute to the development of tobacco-associated pancreatic carcinogenesis.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone, a component of tobacco smoke, modulates mediator release from human bronchial and alveolar epithelial cells

Respiratory epithelial cells are known to contribute to immune responses through the release of mediators. The aim of this study was to characterize the immunomodulatory effects of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco carcinogen, on respiratory epithelial cells and to compare two metabolic pathways, alpha-methylhydroxylation and alpha-methylenehydroxylation, involved in these effects using selective precursors, 4-(acetoxy-methylnitrosamino)-1-(3-pyridil)-1-butanone (NNKOAc) and N-nitroso (acetoxymethyl) methylamine (NDMAOAc), respectively. Human bronchial and alveolar epithelial cell lines, BEAS-2B and A549, respectively, were treated with NNK, NNKOAc and NDMAOAc for 24 h with and without tumour necrosis factor (TNF) and mediators released in cell-free supernatants were measured by enzyme-linked immunosorbent assay (ELISA). NNK significantly inhibited interleukin (IL)-8, IL-6 and monocyte chemoattractant protein-1 (MCP-1) production in both cell types. Similar results were observed with primary bronchial and alveolar epithelial cells. Although NNK increased prostaglandin E(2) (PGE(2)) production by A549 cells, its immunomodulatory effects were not mediated by PGE(2) according to the results with cyclo-oxygenase inhibitors. NNKOAc mimicked NNK effects, whereas NDMAOAc significantly inhibited IL-8 production in BEAS-2B cells and MCP-1 in both cell types. These results demonstrate that NNK and its reactive metabolites have immunosuppressive effects on respiratory epithelial cells, which could contribute to the increased respiratory infections observed in smokers and the development and/or the progression of lung cancer.

Tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone promotes functional cooperation of Bcl2 and c-Myc through phosphorylation in regulating cell survival and proliferation

Nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is formed by nitrosation of nicotine and has been identified as the most potent carcinogen contained in cigarette smoke. NNK significantly contributes to smoking-related lung cancer, but the molecular mechanism remains enigmatic. Bcl2 and c-Myc are two major oncogenic proteins that cooperatively promote tumor development. We report here that NNK simultaneously stimulates Bcl2 phosphorylation exclusively at Ser(70) and c-Myc at Thr(58) and Ser(62) through activation of both ERK1/2 and PKCalpha, which is required for NNK-induced survival and proliferation of human lung cancer cells. Treatment of cells with staurosporine or PD98059 blocks both Bcl2 and c-Myc phosphorylation and results in suppression of NNK-induced proliferation. Specific depletion of c-Myc expression by RNA interference retards G(1)/S cell cycle transition and blocks NNK-induced cell proliferation. Phosphorylation of Bcl2 at Ser(70) promotes a direct interaction between Bcl2 and c-Myc in the nucleus and on the outer mitochondrial membrane that significantly enhances the half-life of the c-Myc protein. Thus, NNK-induced functional cooperation of Bcl2 and c-Myc in promoting cell survival and proliferation may occur in a novel mechanism involving their phosphorylation, which may lead to development of human lung cancer and/or chemoresistance.

Mitochondrial volume densities in the smokeless tobacco-treated hamster cheek pouch epithelium

OBJECTIVES

To compare the morphological changes and quantitative distribution of mitochondria in the hamster cheek pouch (HCP) epithelium treated with smokeless tobacco (ST).

MATERIALS AND METHODS

Archives of experimental material from previously published studies (Ashrafi et al., 1992) were utilized. Animals in experimental group received moist ST (snuff) in their right pouch, 5 days weekly for 24 months, while no snuff was given to control group. After 24 months, the epithelial tissues were processed for electron microscopy study. Volume densities of mitochondria were assessed by morphometry.

MAIN OUTCOME MEASURES

Mitochondrial volume densities in the two groups, experimental vs control.

RESULTS

In both control and experimental groups mitochondria were concentrated between the nucleus and basal cell plasma membrane. A decrease in the mean mitochondrial volume density (Vvmit) was observed from the basal layer to the more superficial layers in both groups. The experimental HCP displayed more mitochondria than control, and the granular epithelial cell layer in experimental group showed significantly a higher mean Vvmit than the control group (P = 0.03). It was concluded that greater numbers of mitochondria were retained in ST-treated granular cells of the hyperplastic epithelia than in the normal epithelium.

Transformation of non-cancerous human breast epithelial cell line MCF10A by the tobacco-specific carcinogen NNK

Repeated treatments of non-cancerous human breast epithelial cells MCF10A with a low dose of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induced the development of cancerous cells. NNK-transformed MCF10A cells acquired cancerous properties including anchorage-independent cell growth and increased cell motility. Cellular transformation of MCF10A cells was accompanied by a loss of responsiveness to 17beta-estradiol and decreased rate of cell proliferation. NNK-transformed MCF10A cells were also tumorigenic in immunodifficient mice. Studies of changes in the regulation of intracellular signaling pathways revealed that the upstream Erk pathway was down-regulated in the NNK-transformed cells. Our data provide the first evidence suggesting that the tobacco carcinogen NNK is competent to induce malignant transformation of non-cancerous human breast epithelial cells. Our findings suggest that the tobacco carcinogen NNK may contribute to early events in human breast carcinogenesis.

Receptor-mediated effects of nicotine and its nitrosated derivative NNK on pulmonary neuroendocrine cells

Pulmonary neuroendocrine cells (PNECs) have been implicated in the development of small cell lung carcinoma (SCLC) and pediatric asthma, and smoking is a risk factor for both diseases. We as well as others have shown that the alpha(7) nicotinic acetylcholine receptor (alpha(7) nAChR) regulates the release of 5-hydroxytryptamine (5-HT, serotonin) in PNECs and SCLC. Serotonin is an autocrine growth factor for PNECs and SCLC and acts as broncho-constrictor. We found that nicotine and its nitrosated carcinogenic derivative 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) bind to the alpha(7) nAChR in SCLC and PNECs, resulting in the influx of Ca(2+), release of 5-HT, and activation of a mitogenic pathway mediated by protein kinase C (PKC), Raf-1, mitogen activated protein kinase (MAPK) and c-myc. Exposure to 10% CO(2) acted synergistically. Unstimulated SCLC cells from smokers demonstrated high base levels of 5-HT release and of individual downstream signaling components in comparison to PNECs. Subchronic exposure of PNECs to NNK up-regulated the alpha(7) nAChR and its associated serotonergic mitogenic pathway in PNECs, an effect that may contribute to the development of SCLC in smokers and pediatric asthma in children of mothers who smoke.

Investigation of the role of lipoxygenase in bioactivation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in human lung

4-Methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) is a potent tobacco-specific carcinogen believed to play a role in human lung cancer. Bioactivation of NNK involves alpha-carbon hydroxylation that could be catalyzed by cytochrome P450, hemoglobin, and lipoxygenases (LOX). In the present study, the role of LOX in NNK bioactivation was investigated. Formation of keto acid, the endpoint metabolite of alpha-methylene NNK hydroxylation, was observed in human lung cytosols incubated with 4.2 microM [5-(3)H]NNK (N = 6). Following concanavalin A affinity chromatography to enrich human lung lipoxygenase (HLLO), the fraction containing cytosolic components less LOX (fraction 1) retained the ability to bioactivate NNK. Although enriched HLLO exhibited the characteristic dioxygenase and hydroperoxidase activities, it did not bioactivate NNK. The LOX inhibitor nordihydroguaiaretic acid inhibited dioxygenase activity of HLLO by 83 +/- 19% (P < 0.05, N = 6), but did not inhibit keto acid formation in the crude cytosols (N = 6, P > 0.05). Failure of soybean LOX to catalyze NNK bioactivation supported the results observed in human lung cytosols, and failure of chemically generated alkylperoxyl radicals to bioactivate NNK further suggested that the dioxygenase activity of LOX is not likely to be involved in NNK bioactivation. Horseradish peroxidase and myeloperoxidase catalyzed NNK bioactivation were also nondetectable. Our results demonstrate that, although human lung cytosols can bioactivate NNK to form keto acid, LOX is not involved. We have attributed the ability of crude human lung cytosols to bioactivate NNK to hemoglobin. The inhibitory effect of 1-aminobenzotriazole and arachidonic acid on keto acid formation in the crude cytosols and in fraction 1, respectively (P < 0.05, N = 6), is consistent with hemoglobin-catalyzed NNK bioactivation.

Identification of tobacco-derived compounds in human pancreatic juice

Cancer of the pancreas is the fourth leading cause of cancer mortality in the USA with an estimated 28 900 deaths in 2001. Several factors have been implicated in the etiology of this disease. However, at present, only cigarette smoking has been positively associated with pancreatic cancer. It is our working hypothesis that tobacco-derived compounds can be delivered to the pancreas where, upon metabolic activation, they can initiate carcinogenesis. Our current investigation was conducted to determine whether cotinine and tobacco-specific nitrosamines (TSNA) are present in human pancreatic juice. Smoking status was assessed by the determination of levels of urinary cotinine and was further supported by quantifying nicotine in hair. The TSNA were extracted from the pancreatic juice of 18 smokers and 9 nonsmokers by supercritical carbon dioxide that contained 10% methanol. The extracts were analyzed for TSNA, namely, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN), by gas chromatography with mass spectrometric detection using a selected ion monitoring technique (GC-SIM-MS). Twenty-three extracts of human pancreatic juice were also analyzed for the presence of the NNK metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) by GC-SIM-MS and by gas chromatography interfaced wit a thermal energy analyzer (GC-TEA; TEA, a nitrosamine-specific detector). Cotinine was detected in all analyzed samples of pancreatic juice from smokers (129 +/- 150 ng/mL juice; mean +/- standard deviation) and was present in only two of the nine samples of pancreatic juice from nonsmokers. Its levels in these two samples were 7 and 9 ng/mL juice. NNK was detected in 15 of 18 samples (83%) from smokers at levels from 1.37 to 604 ng/mL pancreatic juice. In nine samples of pancreatic juice from nonsmokers, NNK ranged from not detected (in three samples) to 96.8 ng/mL juice. In pancreatic juice from smokers the mean level of NNK (88.7 +/- 161 ng/mL juice) was significantly higher (p < 0.04) than in that from nonsmokers (12.4 +/- 31.7 ng/mL juice). In addition to NNK, NNN was found in two samples of pancreatic juice of smokers at levels of 68.1 and 242 ng/mL juice; NNN was not detected in any other sample. NNAL was present in 8 of 14 pancreatic juice samples (57%) from smokers and in three of nine samples (33%) from nonsmokers. This research presents preliminary data that supports the hypothesis that pancreatic tissue is exposed to TSNA and that they may be important contributors to pancreatic carcinogenesis in humans.

A critical assessment of some biomarker approaches linked with dietary intake

In this review many examples are given of the complexities involved in using some biomarkers in relation to assessing the effects of dietary exposure, when there is frequently a need to determine changes following long-term low level exposure to dietary components. These range from understanding why the biomarker might be valuable and how best it can be measured, to the pitfalls which can occur in the interpretation of data. Analytical technique is considered in relation to folate and selenium, and flavonoid and carotenoid species are used to illustrate how the metabolism of a compound may alter the validity or adequacy of a marker. Vitamin A is discussed in relation to the difficulties which can arise when there are several biomarkers that may be available to assess exposure to one nutrient. Vitamin B12 is discussed in relation to the dietary choices made by individuals. Possible interactions and the role of measuring total antioxidant capacity is considered in some detail. In contrast to most nutrients, there is a marked lack of biomarkers of either exposure or effect for most non-nutrients. The role of biological effect monitoring is considered for dietary contaminants, fumonisins and polyhalogenated aromatic hydrocarbons. Aflatoxins are discussed to exemplify food contaminants for which the biomarker approach has been extensively studied. Finally some compounds which are deliberately added to foods and some which appear as processing contaminants are each considered briefly in relation to the requirement for a biomarker of exposure to be developed.

Effects of vitamins and common drugs on reduction of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in rat microsomes

4-(Methylnitrosamino)-1-(3-pyridyl)-butanone (NNK) is a tobacco-specific nitrosamino that requires metabolic activation by cytochrome P450 enzymes. The activation of NNK by cytochrome P450 enzymes leads to the formation of different metabolites. Detoxification of NNK usually occurs via carbonyl reduction to its hydroxyl product, 4-(methylnitrosamino)-1-(3-pyridyl)-butanol (NNAL). In the present study, the influences of common vitamins and P450 modulators on the reduction of NNK by rat microsomes were studied. The formation of NNAL but not other metabolites was detected by the described HPLC method. Among the vitamins tested, vitamins E, A (retinol), B6 and B5 were found to be marginal effective upon reduction of NNK while vitamins A (cis-acid), A (trans-acid), D2, D3, K1, K3, B1 and A (crocetin) increased the formation of NNAL from 3 to 21%. The effect of vitamin C-palmitate (<10 microM) was most pronounced followed by crocetin upon reduction of NNK. Clonidine, tolbutamide and atropine slightly increased the reduction of NNK while cimetidine showed no effects. The modulation of NNK reduction could reduce the carcinogenic potential of NNK, since the main detoxification pathway of NNK involves carbonyl reduction.

The 399Gln polymorphism in the DNA repair gene XRCC1 modulates the genotoxic response induced in human lymphocytes by the tobacco-specific nitrosamine NNK

DNA repair plays a critical role in protecting the genome of the cell from the insults of cancer-causing agents such as those found in tobacco smoke. Reduced DNA repair capacity would, therefore, constitute a significant risk factor for smoking-related cancers. Recently, a number of polymorphisms in several DNA repair genes have been discovered, and it is possible that these polymorphisms may affect DNA repair capacity and thus modulate cancer susceptibility in exposed populations. In the current study, we explored the relationship between two polymorphisms in the DNA repair gene XRCC1 (polymorphisms in codons 194 and 399) and the genotoxic response induced by the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The sister chromatid exchange (SCE) assay was used as a marker of genetic damage. Our results, using whole blood cultures from 47 volunteers, indicated that treatment of cells with 0.24, 0.72 and 1.44 mM of NNK induced a concentration-dependent increase in the mean number of SCE (P<0.001). There was a significant difference (P<0.05) in response to NNK treatment between cells from individuals with the 399Gln allele (either homozygous or heterozygous) and cells from individuals with the homozygous 399 Arg/Arg genotype. Treatment of cells that have the 399Gln allele with 0.24, 0.72 and 1.44 mM NNK resulted in 22.8, 35.8 and 52.8% increases in NNK-induced SCE, respectively. Treatment of cells with the 399 Arg/Arg genotype using the same NNK concentrations resulted in 16.0, 15.5 and 32.6% increases in NNK-induced SCE, respectively. In contrast, no significant difference in NNK-induced SCE was observed between cells with the codon 194 Arg/Arg genotype and cells with the codon 194 Arg/Trp genotype at all concentrations of NNK tested. These data suggest that the Arg399Gln amino acid change may alter the phenotype of the XRCC1 protein, resulting in deficient DNA repair. Our study underscores the important role of polymorphisms in DNA repair genes in influencing the genotoxic responses to environmental mutagens, and justifies additional studies to investigate their potential role in susceptibility to cancer.

CYP2D6 gene polymorphism in caucasian smokers: lung cancer susceptibility and phenotype-genotype relationships

Individual susceptibility to smoking-related cancers is proposed to partly depend on a genetically determined ability to metabolise tobacco carcinogens. We previously reported on the association between the activity of the xenobiotic-metabolising enzyme CYP2D6 and lung cancer risk in a hospital-based case-control study among French Caucasian smokers. Here we extended the study to address the effect of four gene-inactivating mutations (CYP2D6(*)3, (*)4, (*)5 and (*)16) and the gene duplication of the CYP2D6 gene (CYP2D6(*)2x2 or CYP2D6(*)1x2) on lung cancer risk in the same population (150 patients with primary lung carcinoma of squamous cell or small cell histology and 172 controls). The risk of lung cancer associated with the CYP2D6 poor metaboliser genotype (odds ratio 1.5, 95% confidence interval 0.5-4.3) did not differ from that in the reference category of extensive metaboliser and ultra-rapid metaboliser genotypes combined. Lung cancer risks for the CYP2D6 PM genotype amongst light smokers (tobacco consumption </=20 g/day) or heavy smokers (>20 g/day) were not significantly different. The present findings agree with the discrepancy between the phenotype-based and genotype-based studies indicated by the recent meta-analyses.

Squalene: potential chemopreventive agent

Squalene is a triterpene that is an intermediate of the cholesterol biosynthesis pathway and it can be obtained from the diet. Olive oil contains 0.2-0.7% squalene. The average intake of squalene is 30 mg/day in the United States, however, when consumption of olive oil is high, the intake of squalene can reach 200-400 mg/day as observed in Mediterranean countries. The decreased risk for various cancers associated with high olive oil consumption may be due to the presence of squalene. Experimental studies have shown that squalene can effectively inhibit chemically-induced colon, lung and skin tumourigenesis in rodents. The protective effect is observed when squalene is given before and/or during carcinogen treatment. The mechanisms involved for the chemopreventive activity of squalene may include inhibition of Ras farnesylation, modulation of carcinogen activation and anti-oxidative activities. However, several factors must be taken into consideration when the evidence for the inhibition of carcinogenesis by squalene is examined, these include the effective dose used and the time of exposure. The information obtained is from animal bioassays and the long-term effects from consuming increased levels of squalene are not known. Although animal studies have enhanced our understanding of the possible action of squalene in decreasing carcinogenesis, one must apply caution in extrapolating the information obtained in animal studies to humans, because of possible species differences. In order to evaluate the overall implications of squalene to human cancer prevention, further studies are needed to fully identify its protective effects, as well as possible detrimental effects.