Carcinogenicity and DNA adduct formation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and enantiomers of its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in F-344 rats

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is metabolized to enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), found in the urine of virtually all people exposed to tobacco products. We assessed the carcinogenicity in male F-344 rats of (R)-NNAL (5 ppm in drinking water), (S)-NNAL (5 ppm), NNK (5 ppm) and racemic NNAL (10 ppm) and analyzed DNA adduct formation in lung and pancreas of these rats after 10, 30, 50 and 70 weeks of treatment. All test compounds induced a high incidence of lung tumors, both adenomas and carcinomas. NNK and racemic NNAL were most potent; (R)-NNAL and (S)-NNAL had equivalent activity. Metastasis was observed from primary pulmonary carcinomas to the pancreas, particularly in the racemic NNAL group. DNA adducts analyzed were O (2)-[4-(3-pyridyl)-4-oxobut-1-yl]thymidine (O (2)-POB-dThd), 7-[4-(3-pyridyl)-4-oxobut-1-yl]guanine(7-POB-Gua),O (6)-[4-(3-pyridyl)-4-oxobut-1-yl]deoxyguanosine(O (6)-POB-dGuo),the 4-(3-pyridyl)-4-hydroxybut-1-yl(PHB)adductsO (2)-PHB-dThd and 7-PHB-Gua, O (6)-methylguanine (O (6)-Me-Gua) and 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB)-releasing adducts. Adduct levels significantly decreased with time in the lungs of rats treated with NNK. Pulmonary POB-DNA adducts and O (6)-Me-Gua were similar in rats treated with NNK and (S)-NNAL; both were significantly greater than in the (R)-NNAL rats. In contrast, pulmonary PHB-DNA adduct levels were greatest in the rats treated with (R)-NNAL. Total pulmonary DNA adduct levels were similar in (S)-NNAL and (R)-NNAL rats. Similar trends were observed for DNA adducts in the pancreas, but adduct levels were significantly lower than in the lung. The results of this study clearly demonstrate the potent pulmonary carcinogenicity of both enantiomers of NNAL in rats and provide important new information regarding DNA damage by these compounds in lung and pancreas.

Intranasal delivery of liposomal indole-3-carbinol improves its pulmonary bioavailability

Indole-3-carbinol (I3C), a constituent of commonly consumed Brassica vegetables, has been shown to have anticancer effects in a variety of preclinical models of lung cancer. However, it has shown only limited efficacy in clinical trials, likely due to its poor oral bioavailability. Intranasal administration of I3C has the potential to enhance the pulmonary accumulation of the drug, thereby improving its availability at the target site of action. In this study, we developed a liposomal formulation of I3C and evaluated its lung delivery and chemopreventive potential in tobacco smoke carcinogen [4-(methylnitro-samino)-1-(3-pyridyl)-1-butanone (NNK)]-treated mice. Intranasal administration of I3C liposomes led to a ∼100-fold higher lung exposure of I3C than the oral route of administration. Further, intranasal delivery of liposomal I3C led to a significant reduction (37%; p<0.05) in the levels of the DNA adduct formation induced by NNK treatment. Liposomal I3C also significantly increased (by 10-fold) the expression of CYP1A1, a cytochrome P450 enzyme known to increase the detoxification of chemical carcinogens by enhancing their metabolism. Overall, our findings demonstrate that intranasal administration of liposomal I3C has the potential to significantly improve the efficacy of I3C for lung cancer chemoprevention.

Dihydromethysticin from kava blocks tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis and differentially reduces DNA damage in A/J mice

We have previously shown that kava and its flavokavain-free Fraction B completely blocked 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice with a preferential reduction in NNK-induced O (6)-methylguanine (O (6)-mG). In this study, we first identified natural (+)-dihydromethysticin (DHM) as a lead compound through evaluating the in vivo efficacy of five major compounds in Fraction B on reducing O (6)-mG in lung tissues. (+)-DHM demonstrated outstanding chemopreventive activity against NNK-induced lung tumorigenesis in A/J mice with 97% reduction of adenoma multiplicity at a dose of 0.05mg/g of diet (50 ppm). Synthetic (±)-DHM was equally effective as the natural (+)-DHM in these bioassays while a structurally similar analog, (+)-dihydrokavain (DHK), was completely inactive, revealing a sharp in vivo structure-activity relationship. Analyses of an expanded panel of NNK-induced DNA adducts revealed that DHM reduced a subset of DNA adducts in lung tissues derived from 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL, the active metabolite of NNK). Preliminary 17-week safety studies of DHM in A/J mice at a dose of 0.5mg/g of diet (at least 10× its minimum effective dose) revealed no adverse effects, suggesting that DHM is likely free of kava's hepatotoxic risk. These results demonstrate the outstanding efficacy and promising safety margin of DHM in preventing NNK-induced lung tumorigenesis in A/J mice, with a unique mechanism of action and high target specificity.

A study on mast cell variation in neoplastic and non neoplastic disease of uterine cervix

Background: Mast cells are heterogeneous group of immune cells involved in multiple biological events. The significance of mast cells in uterine tumor surveillance has been studied with conflicting results. The presence of mast cell in tumor has been described as evidence of a host immunologic anti tumor response and if they are abundant the prognosis is good. However in other studies, with the help of different granules of mast cell, it is said to be very closely related with angiogenesis and tumor invasion. The study aims to analyze the histomorphologic changes with special reference to mast cells in different neoplastic and non neoplastic disease of uterine cervix, and also the relationship of the mast cell population with degree of anaplasia and mitotic figures.Materials and methods: Cervical biopsies received in the department of Pathology for HPE were stained with H& E stain and toludine blue for the identification of mast cellResult: Out of a total of 100 cases, 82 were non neoplastic cases with the mean mast cell count of 83.73 and mean age of patient being 44.30 year. Eighteen neoplastic cases were included which had mean mast cell count of 13.5 and mean age of 49.5 year.Conclusion: Mast cell was found to be highest in non Neoplastic lesion with increase count in polypoidal cervicitis. There was a statistical significance variation between mast cell count in neoplastic and non Neoplastic disease of the cervix. However,role of age in mast cell count was least significant.DOI: http://dx.doi.org/10.3126/jpn.v4i8.11594 Journal of Pathology of Nepal; Vol.4,No. 8 (2014) 658-662

Liquid chromatography-electrospray ionization-tandem mass spectrometry quantitation of urinary [pyridine-D4]4-hydroxy-4-(3-pyridyl)butanoic acid, a biomarker of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone metabolic activation in smokers

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 1) is a potent tobacco-specific lung carcinogen believed to play a key role in the development of lung cancer in smokers. Metabolic activation of NNK to DNA damaging reactive intermediates proceeds via α-hydroxylation pathways. The end products of these pathways are excreted in the urine of smokers as 4-oxo-4-(3-pyridyl)butanoic acid (keto acid, 3) and 4-hydroxy-4-(3-pyridyl)butanoic acid (hydroxy acid, 4). The sum of these biomarkers (after NaBH4 treatment), referred to as total hydroxy acid, could potentially be used to measure the extent of NNK metabolic activation in smokers. However, the same metabolites are formed from nicotine; therefore, there is a need to distinguish the NNK- and nicotine-derived keto and hydroxy acid in smokers' urine. We previously developed a unique methodology based on the use of [pyridine-D4]NNK ([D4]1), which metabolizes to the correspondingly labeled biomarkers. In this study, we developed a sensitive and reproducible assay for the detection and quantitation of total [pyridine-D4]hydroxy acid ([D4]4) in human urine. A two-step derivatization approach was used to convert [D4]4 to [pyridine-D4]methyl 4-hexanoyl-4-(3-pyridyl)butanoate ([D4]6), and an LC-ESI-MS/MS method was developed for the analysis of this derivative with excellent sensitivity, accuracy, and precision. The robustness and reproducibility of the assay was further confirmed by its application for the analysis of urine samples from 87 smokers who smoked [D4]1-containing cigarettes for 1 week. The measured level averaged 130 fmol/mL urine. The developed assay can be used in future studies that may require evaluation of the relative efficiency of NNK metabolic activation in humans.

Kava blocks 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in association with reducing O6-methylguanine DNA adduct in A/J mice

We previously reported the chemopreventive potential of kava against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)- and benzo(a)pyrene (BaP)-induced lung tumorigenesis in A/J mice during the initiation and postinitiation stages. In this study, we investigated the tumorigenesis-stage specificity of kava, the potential active compounds, and the underlying mechanisms in NNK-induced lung tumorigenesis in A/J mice. In the first experiment, NNK-treated mice were given diets containing kava at a dose of 5 mg/g of diet during different periods. Kava treatments covering the initiation stage reduced the multiplicity of lung adenomas by approximately 99%. A minimum effective dose is yet to be defined because kava at two lower dosages (2.5 and 1.25 mg/g of diet) were equally effective as 5 mg/g of diet in completely inhibiting lung adenoma formation. Daily gavage of kava (one before, during, and after NNK treatment) completely blocked lung adenoma formation as well. Kavalactone-enriched fraction B fully recapitulated kava's chemopreventive efficacy, whereas kavalactone-free fractions A and C were much less effective. Mechanistically, kava and fraction B reduced NNK-induced DNA damage in lung tissues with a unique and preferential reduction in O(6)-methylguanine (O(6)-mG), the highly tumorigenic DNA damage by NNK, correlating and predictive of efficacy on blocking lung adenoma formation. Taken together, these results demonstrate the outstanding efficacy of kava in preventing NNK-induced lung tumorigenesis in A/J mice with high selectivity for the initiation stage in association with the reduction of O(6)-mG adduct in DNA. They also establish the knowledge basis for the identification of the active compound(s) in kava.

Application of a high-resolution mass-spectrometry-based DNA adductomics approach for identification of DNA adducts in complex mixtures

Liquid chromatography coupled with mass spectrometry (LC-MS) is the method of choice for analysis of covalent modification of DNA. DNA adductomics is an extension of this approach allowing for the screening for both known and unknown DNA adducts. In the research reported here, a new high-resolution/accurate mass MS(n) methodology has been developed representing an important advance for the investigation of in vivo biological samples and for the assessment of DNA damage from various human exposures. The methodology was tested and optimized using a mixture of 18 DNA adducts representing a range of biologically relevant modifications on all four bases and using DNA from liver tissue of mice exposed to the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). In the latter experiment, previously characterized adducts, both expected and unexpected, were observed.

Urinary 3,3'-diindolylmethane: a biomarker of glucobrassicin exposure and indole-3-carbinol uptake in humans

BACKGROUND

Brassica vegetable consumption may confer a protective effect against cancer, possibly attributable to their glucosinolates. Glucobrassicin is a predominant glucosinolate and is the precursor of indole-3-carbinol (I3C), a compound with anticancer effects. However, objective assessments of I3C uptake from Brassica vegetables have not been successful.

METHODS

We conducted a randomized, crossover trial to test whether 3,3'-diindolylmethane (DIM, a metabolite of I3C) excreted in the urine after consumption of raw Brassica vegetables with divergent glucobrassicin concentrations is a marker of I3C uptake from such foods. Twenty-five subjects were fed 50 g of either raw "Jade Cross" Brussels sprouts (high glucobrassicin concentration) or "Blue Dynasty" cabbage (low glucobrassicin concentration) once daily for 3 days. All urine was collected for 24 hours after vegetable consumption each day. After a washout period, subjects crossed over to the alternate vegetable. Urinary DIM was measured using a novel liquid chromatography-electrospray ionization-tandem mass spectrometry-selected reaction monitoring (LC-ESI-MS/MS-SRM) method with [(2)H2]DIM as internal standard.

RESULTS

Urinary DIM was consistently and significantly higher after Brussels sprouts feeding than after cabbage feeding, as evidenced by an average difference of 8.73 pmol/mg creatinine (95% confidence interval, 5.36-12.10; P = 0.00002).

CONCLUSION

We have successfully quantified urinary DIM after uptake of I3C from food, and demonstrated that differences in glucobrassicin exposure are reflected in urinary DIM levels.

IMPACT

Our LC-ESI-MS/MS-SRM method and the results of our study indicate urinary DIM is a measure of I3C uptake from Brassica vegetables, a finding that can be utilized in prospective epidemiologic and chemoprevention studies.

Abstract A01: Lung and pancreatic carcinogenicity and DNA binding of the enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in F344 rats

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent pulmonary carcinogen in laboratory animals and is believed to play an important role as a cause of tobacco related cancers. NNK is metabolically converted to NNAL in virtually all biological systems. All tobacco users as well as people exposed to secondhand tobacco smoke have NNAL in their urine. NNAL has a chiral center at its 1-position, thus consequently exists in enantiomeric forms. Previous studies have shown differing amounts of (R)- or (S)-NNAL in human tissues and urine after exposure to NNK, depending on the conditions and the system studied. However, little is known about the carcinogenic activity of (R)- or (S)-NNAL. Only one previous study has been reported demonstrating higher lung tumorigenicity of (S)-NNAL than (R)-NNAL in an A/J mouse model. Understanding mechanisms of carcinogenesis by these compounds can provide critical insights relevant for cancer prevention in people exposed to tobacco products. Therefore, in the study reported here, we have evaluated the carcinogenicity and DNA binding of the NNAL enantiomers in F-344 rats chronically treated with these compounds in the drinking water.

Groups of 24 male F-344 rats, 7 weeks of age, were treated chronically with NNK, (R)-NNAL or (S)-NNAL (5 ppm in drinking water). Controls received tap water or racemic NNAL (15 rats, 10 ppm in drinking water). The chronic treatment lasted 90 weeks. The number of animals per group which came to necropsy at the end of the study were: NNK, 23; (R)-NNAL, 23; (S)-NNAL, 22; control, 22; racemic NNAL, 15. Nearly all animals in the (R)-NNAL, (S)-NNAL, racemic NNAL, and NNK-treated groups had lung tumors. In the (R)-NNAL-treated group, there were 22 animals with lung adenoma and 3 with lung carcinoma while in the (S)-NNAL group there were 20 rats with lung adenoma and 5 with lung carcinoma. In the racemic NNAL group there were 15 rats with lung adenoma and 13 with lung carcinoma while in the NNK group there were 23 rats with lung adenoma and 14 with lung carcinoma. There were no lung tumors in the control animals. These results demonstrate that both enantiomers of NNAL are pulmonary carcinogens in the F-344 rat, but less carcinogenic to the lung than NNK (P&lt;0.001). Tumors of the pancreas, predominantly exocrine adenocarcinomas, were also observed in this study: (R)-NNAL, 1 rat with 2 tumors; (S)-NNAL 2 rats with 3 tumors; racemic NNAL, 4 rats with 14 tumors; NNK 3 rats with 3 tumors.

DNA binding studies were performed using tissues harvested at various time-points throughout the experiment. Rats (9 per group) from the NNK, (R)-NNAL, (S)-NNAL, and control groups were euthanized at 10, 30, 50 and 70 weeks. DNA was isolated from the lung and pancreas tissues. The DNA samples were analyzed by LC-ESI-MS/MS with selected reaction monitoring (SRM) analysis for various DNA adducts. O6-Methyl-Gua, POB-DNA adducts, including 7-POB-Gua, O2-POB-dThd and O6-POB-dG and PHB-DNA adducts, including 7-PHB-Gua, O2-PHB-dThd and O6-PHB-dG were measured in lung DNA samples. POB-DNA adducts were measured in pancreas DNA. The preliminary results from these analyses indicate that O6-Methyl-Gua and POB-DNA adducts levels (both in lung and pancreas DNA) were similar in NNK and (S)-NNAL treated rats and significantly higher than in (R)-NNAL treated rats, while PHB-DNA adducts levels were significantly higher in (R)-NNAL treated animals compared to NNK and (S)-NNAL treated groups. The results of this study demonstrate that both (R)-NNAL and (S)-NNAL, at 5 ppm in the drinking water, are effective pulmonary carcinogens in the F-344 rat and are metabolically activated to DNA binding metabolites in the lung. Furthermore, the results presented here confirm the previously observed pancreatic carcinogenicity of racemic NNAL in the F-344 rat. Collectively, these results provide important new insights relevant to mechanisms of carcinogenesis by NNK and NNAL, and to lung and pancreatic cancer in people exposed to tobacco products.

Citation Format: Silvia Balbo, Charles S. Johnson, Lijiao Zhao, M Gerard O'Sullivan, Irina Stepanov, Mingyao Wang, Fekadu Kassie, Steven Carmella, Pramod Upadhyaya, Chap T. Le, Stephen S. Hecht. Lung and pancreatic carcinogenicity and DNA binding of the enantiomers of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in F344 rats. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr A01.

Quantitation of pyridyloxobutyl-DNA adducts in tissues of rats treated chronically with (R)- or (S)-N'-nitrosonornicotine (NNN) in a carcinogenicity study

We quantified DNA adducts resulting from 2'-hydroxylation of enantiomers of the tobacco-specific nitrosamine N'-nitrosonornicotine (NNN) in tissues of male F-344 rats after 10, 30, 50, and 70 weeks of treatment with 14 ppm in the drinking water. These rats were in subgroups of a carcinogenicity study in which (S)-NNN was highly tumorigenic in the oral cavity and esophagus, while (R)-NNN was relatively weakly active. DNA adducts were quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry in six tissues: oral mucosa, esophageal mucosa, nasal respiratory mucosa, nasal olfactory mucosa, liver, and lung. O²-[4-(3-Pyridyl)-4-oxobut-1-yl]thymidine (O²-POB-dThd, 7) and 7-[4-(3-pyridyl)-4-oxobut-1-yl]-2'-deoxyguanosine (7-POB-dGuo, 8), the latter as 7-[4-(3-pyridyl)-4-oxobut-1-yl]guanine (7-POB-Gua, 11), were detected at each time point in each tissue. In the target tissues for carcinogenicity, oral mucosa and esophageal mucosa, levels of 7-POB-Gua (11) and O²-POB-dThd (7) were similar, or 11 predominated, while in all other tissues at all time points for both enantiomers, 7 was clearly present in greater amounts than 11. Total measured DNA adduct levels in esophageal mucosa and oral mucosa were higher in rats treated with (S)-NNN than (R)-NNN. The highest adduct levels were found in the nasal respiratory mucosa. DNA adducts generally persisted in all tissues without any sign of substantial decreases throughout the 70 week time course. The results of this study suggest that inefficient repair of 7-POB-dGuo (8) in the rat oral cavity and esophagus may be important in carcinogenesis by NNN and support the development of these DNA adducts as potential biomarkers of NNN metabolic activation in people who use tobacco products.

Contamination of deconjugation enzymes derived from Helix pomatia with the plant bioactive compounds 3,3'-diindolylmethane, 5-methoxypsoralen, and 8-methoxypsoralen

Bioactive compounds from plant foods are intensely investigated for effects on disease prevention. β-Glucuronidase/arylsulfatase from Helix pomatia (snail) is commonly used when quantifying exposure to metabolized dietary components. However, we describe here the contamination of multiple formulations of this enzyme preparation with 3,3'-diindolylmethane (DIM), 8-methoxypsoralen (8-MOP), and 5-methoxypsoralen (5-MOP), bioactives from cruciferous and apiaceous vegetables under investigation as putative cancer chemopreventive agents. We identified an Escherichia coli preparation of β-glucuronidase as free from contamination with any of the compounds tested. These results demonstrate the importance of selecting appropriate enzyme preparations when quantifying naturally occurring, trace level compounds in biological fluids.

Levels of (S)-N'-nitrosonornicotine in U.S. tobacco products

INTRODUCTION

N'-nitrosonornicotine (NNN), an esophageal and oral carcinogen present in tobacco products, has a chiral center in its structure. Of its two enantiomers, (S)-NNN exhibits higher tumorigenic potency than (R)-NNN. There is no information available on the levels of (S)-NNN in various tobacco products currently marketed in the United States.

METHODS

We used chiral gas chromatography analysis to determine (S)-NNN levels in a convenience sample of 37 tobacco products currently marketed in the United States: conventional smokeless tobacco, novel smokeless tobacco products, and cigarette tobacco filler.

RESULTS

Among all products analyzed here, (S)-NNN averaged 62.9 ± 6.3% (SD) of NNN. The absolute amount of (S)-NNN in conventional moist snuff averaged 1.26 ± 0.5 µg/g tobacco; in novel smokeless products 0.70 ± 0.2 µg/g tobacco; and in cigarette filler 1.36 ± 0.6 µg/g tobacco (all values are per wet weight). For each cigarette brand, the enantiomeric composition of NNN in cigarette smoke was similar to that of the corresponding tobacco filler.

CONCLUSIONS

Our results demonstrate that (S)-NNN is the predominant NNN enantiomer in moist snuff, novel smokeless tobacco products, and cigarettes currently marketed in the United States. Efforts toward the reduction of NNN in U.S. tobacco products should take into account its enantiomeric composition, with particular focus on (S)-NNN as a causative agent for esophageal and oral cancers associated with tobacco use.

(S)-N'-Nitrosonornicotine, a constituent of smokeless tobacco, is a powerful oral cavity carcinogen in rats

Currently, smokeless tobacco products are being proposed as an alternative mode of tobacco use associated with less harm. All of these products contain the tobacco-specific carcinogen N'-nitrosonornicotine (NNN). The major form of NNN in tobacco products is (S)-NNN, shown in this study to induce a total of 89 benign and malignant oral cavity tumors in a group of 20 male F-344 rats treated chronically with 14 p.p.m. in the drinking water. The opposite enantiomer (R)-NNN was weakly active, but synergistically enhanced the carcinogenicity of (S)-NNN. Thus, (S)-NNN is identified for the first time as a strong oral cavity carcinogen in smokeless tobacco products and should be significantly reduced or removed from these products without delay in order to prevent debilitating and deadly oral cavity cancer in people who use them.

DNA adducts in aldehyde dehydrogenase-positive lung stem cells of A/J mice treated with the tobacco specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

Lung cancer is the leading cause of cancer death in the world. Evidence suggests that lung cancer could originate from mutations accumulating in a subpopulation of self-renewing cells, lung stem cells. Aldehyde dehydrogenase (ALDH) is a marker of stem cells. To investigate the presence of DNA modifications in these cells, we isolated ALDH-positive lung cells from A/J mice exposed to the lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. Using LC-NSI-HRMS/MS-PRM, O(6)-methyl-G, 7-POB-G, and O(2)-POB-dT were positively identified in ALDH-positive cell DNA. This is the first example of detection of carcinogen-DNA adducts in lung stem cells, supporting the hypothesis of their role in lung carcinogenesis.

Lipopolysaccharide enhances mouse lung tumorigenesis: a model for inflammation-driven lung cancer

The association between pulmonary inflammation and lung cancer is well established. However, currently there are no appropriate models that recapitulate inflammation-related lung cancer in humans. In the present study, we examined, in 2 tumor bioassays, enhancement by bacterial lipopolysaccharide (LPS) of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice. Mice that were treated with NNK alone developed 29.6 ± 9.8 and 36.2 ± 4.1 lung tumors per mouse in experiments 1 and 2, respectively. Chronic intranasal instillation of LPS to NNK-treated mice increased the multiplicity of lung tumors to 47.3 ± 16.1 and 51.2 ± 4.8 lung tumors per mouse in experiments 1 and 2, corresponding to a significant increase by 60% and 41%, respectively. Moreover, administration of LPS to NNK-pretreated mice significantly increased the multiplicity of larger tumors and histopathologically more advanced lesions (adenoma with dysplasia and adenocarcinoma), macrophage recruitment to the peritumoral area, and expression of inflammation-, cell proliferation-, and survival-related proteins. Overall, our findings demonstrated the promise of the NNK-LPS-A/J mice model to better understand inflammation-driven lung cancer, dissect the molecular pathways involved, and identify more effective preventive and therapeutic agents against lung cancer.

Chemoprevention of lung tumorigenesis by intranasally administered diindolylmethane in A/J mice

The main reasons for the failure of most chemopreventive agents during clinical trials are poor in vivo bioavailability and dose-limiting side effects. One potential approach to surmount these problems in lung cancer chemoprevention trials could be direct delivery of agents into the pulmonary tissue. In this study, we assessed the efficacy of intranasally delivered bio-response diindolylmethane (BRD) against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in mice. Mice treated with NNK (two doses of 50mg/kg at an interval of a week, intraperitoneal) developed 16.3±2.9 lung tumors per mouse. Post-carcinogen administration of BRD, via intranasal instillation, for 24 weeks, twice a week, at a dose of 2mg per mouse (0.6mg pure diindolylmethane per mouse) reduced the lung tumor multiplicity to 4.6±2.2 tumors per mouse (72% reduction). Likewise, large tumors (>1mm) were almost completely abolished and multiplicities of tumors with a size of 0.5-1mm were reduced by 74%. Tumor volume was also reduced by 82%. Further studies using an in vitro model of lung tumorigenesis showed that BRD exhibited pronounced antiproliferative and apoptotic effects in premalignant and malignant bronchial cells but only minimal effects in parental immortalized cells through, at least in part, suppression of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. These results showed the potent lung tumor inhibitory activities of low doses of BRD given via intranasal instillation and, therefore, intranasal delivery of BRD holds a great promise for lung cancer chemoprevention in subjects at high risk to develop lung cancer.

Abstract CN06-01: Induction of oral cavity cancer in rats by (S)-N'-nitrosonornicotine, a constituent of smokeless tobacco

Smokeless tobacco products such as moist oral snuff are being promoted by the tobacco industry with a half billion dollars per year in advertising. It is likely that the prevalence of smokeless tobacco use will continue to increase in the U.S. Smokeless tobacco products are widely used in other parts of the world and are considered by the International Agency for Research on Cancer as causes of cancer of the oral cavity, esophagus and pancreas in humans. However, no previous study has reported the presence of a strong oral cavity carcinogen in these products.

N'-Nitrosonornicotine (NNN) occurs in significant amounts in smokeless tobacco products, generally being found at levels of 1 - 10 μg/g tobacco. Since NNN has a chiral center, it exists as (S)- and (R)- enantiomers. (S)-NNN is the major enantiomer in smokeless tobacco products. While racemic NNN (a 50:50 mixture of (S)- and (R)-NNN) has been previously shown to cause esophageal tumors in rats, the carcinogenicity of the individual enantiomers has not been reported. Based on our published metabolism and DNA binding studies of (S)-NNN, we hypothesized that it might be a more powerful carcinogen than (R)-NNN and, furthermore, that it might cause oral cancer.

Groups of 24 male F-344 rats were treated with either (S)-NNN (15 ppm), (R)-NNN (15 ppm), or racemic NNN (30 ppm) in the drinking water for 15-20 months. Necropsy of 20 rats treated with (S)-NNN demonstrated a 100% incidence of oral cavity tumors. More than 60 oral cavity tumors were observed, including benign and malignant tumors of the buccal mucosa, soft and hard palate, tongue, and pharynx. All rats also had esophageal tumors. (R)-NNN was significantly less carcinogenic than (S)-NNN. Racemic NNN also induced a high incidence of oral cavity and esophageal tumors.

The results of this study demonstrate for the first time the presence of a strong oral cavity carcinogen in smokeless tobacco. (S)-NNN is a prime target for elimination from these products as a positive step toward cancer prevention.

Citation Format: Stephen S. Hecht, Sandra James-Yi, Gerard O'Sullivan, Irina Stepanov, Mingyao Wang, Fekadu Kassie, Steven Carmella, Pramod Upadhyaya, Silvia Balbo. Induction of oral cavity cancer in rats by (S)-N'-nitrosonornicotine, a constituent of smokeless tobacco. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr CN06-01.

Formation and repair of pyridyloxobutyl DNA adducts and their relationship to tumor yield in A/J mice

The nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a known human carcinogen. It generates methyl and pyridyloxobutyl DNA adducts. The role of the methyl DNA adducts has been well-established in the tumorigenic properties of NNK. However, the role of the pyridyloxobutyl DNA adducts is unclear. Four pyridyloxobutyl DNA adducts have been characterized: 7-[4-3-(pyridyl)-4-oxobut-1-yl]guanine (7-pobG), O²-[4-3-(pyridyl)-4-oxobut-1-yl]-cytodine (O²-pobC), O²-[4-3-(pyridyl)-4-oxobut-1yl]thymidine (O²-pobdT), and O⁶-[4-3-(pyridyl)-4-oxobut-1-yl]-2'-deoxyguanosine (O⁶-pobdG). Mutagenic O⁶-pobdG is thought to contribute to the tumorigenic properties of the pyridyloxobutylation pathway. It is repaired by O⁶-alkylguanine-DNA alkyltransferase (AGT). To explore the role of O⁶-pobdG formation and repair in the tumorigenic properties of NNK, A/J mice were given single or multiple doses of the model pyridyloxobutylating agent 4-(acetoxymethyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNKOAc) in the presence or absence of the AGT depletor, O⁶-benzylguanine. Levels of the four pyridyloxobutyl DNA adducts were measured in the lung at 8, 48, or 96 h following treatment and compared to the lung tumorigenic activity of these treatments. AGT depletion had only a modest effect on the levels of O⁶-pobdG and did not increase tumor formation. Three pyridyloxobutyl DNA adducts, 7-pobG, O²-pobdT, and O⁶-pobdG, persisted in lung DNA at significant levels for up to 96 h post-treatment, suggesting that all three adducts may contribute to the tumorigenic properties of NNK.

Phenanthrene metabolism in smokers: use of a two-step diagnostic plot approach to identify subjects with extensive metabolic activation

Polycyclic aromatic hydrocarbons (PAHs) in cigarette smoke are among the most likely causes of lung cancer. PAHs require metabolic activation to initiate the carcinogenic process. Phenanthrene (Phe), a noncarcinogenic PAH, was used as a surrogate of benzo[α]pyrene and related PAHs to study the metabolic activation of PAHs in smokers. A dose of 10 μg of deuterated Phe ([D₁₀]Phe) was administered to 25 healthy smokers in a crossover design, either as an oral solution or by smoking cigarettes containing [D₁₀]Phe. Phe was deuterated to avoid interference from environmental Phe. Intensive blood and urine sampling was performed to quantitate the formation of deuterated r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene ([D₁₀]PheT), a biomarker of the diol epoxide metabolic activation pathway. In both the oral and smoking arms approximately 6% of the dose was metabolically converted to diol epoxides, with a large intersubject variability in the formation of [D₁₀]PheT observed. Two diagnostic plots were developed to identify subjects with large systemic exposure and significant lung contribution to metabolic activation. The combination of the two plots led to the identification of subjects with substantial local exposure. These subjects produced, in one single pass of [D₁₀]Phe through the lung, a [D₁₀]PheT exposure equivalent to the systemic exposure of a typical subject and may be an indicator of lung cancer susceptibility. Polymorphisms in PAH-metabolizing genes of the 25 subjects were also investigated. The integration of phenotyping and genotyping results indicated that GSTM1-null subjects produced approximately 2-fold more [D₁₀]PheT than did GSTM1-positive subjects.

The sphingolipid degradation product trans-2-hexadecenal forms adducts with DNA

Sphingosine 1-phosphate, a bioactive signaling molecule with diverse cellular functions, is irreversibly degraded by the endoplasmic reticulum enzyme sphingosine 1-phosphate lyase, generating trans-2-hexadecenal and phosphoethanolamine. We recently demonstrated that trans-2-hexadecenal causes cytoskeletal reorganization, detachment, and apoptosis in multiple cell types via a JNK-dependent pathway. These findings and the known chemistry of related α,β-unsaturated aldehydes raise the possibility that trans-2-hexadecenal may interact with additional cellular components. In this study, we show that it reacts readily with deoxyguanosine and DNA to produce the diastereomeric cyclic 1,N(2)-deoxyguanosine adducts 3-(2-deoxy-β-d-erythro-pentofuranosyl)-5,6,7,8-tetrahydro-8R-hydroxy-6R-tridecylpyrimido[1,2-a]purine-10(3H)one and 3-(2-deoxy-β-d-erythro-pentofuranosyl)-5,6,7,8-tetrahydro-8S-hydroxy-6S-tridecylpyrimido[1,2-a]purine-10(3H)one. Thus, our findings suggest that trans-2-hexadecenal produced endogenously by sphingosine 1-phosphate lyase can react directly with DNA forming aldehyde-derived DNA adducts with potentially mutagenic consequences.

Lung Tumorigenesis Suppressing Effects of a Commercial Kava Extract and Its Selected Compounds in A/J Mice

Lung cancer is the most deadly malignancy in the US. Chemoprevention is potentially a complementary approach to smoking cessation for lung cancer control. Recently, we reported that a commercially available form of kava extract significantly inhibits 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo(a)pyrene (BaP)-induced lung tumorigenesis in A/J mice at a dose of 10 mg per gram diet. In the present study, we examined the dose-dependent lung tumor inhibitory activities of kava and investigated potential active constituent(s). Mice treated with carcinogen alone contained 12.1±5.8 lung adenomas per mouse 22 weeks after final carcinogen administration. Mice that were fed diets containing kava at dosages of 1.25, 2.5, 5, and 10 mg/g of diet had 8.4±3.5, 6.6±3.5, 4.3±2.4, and 3.8±2.3 lung adenomas per mouse, respectively. This corresponds to a reduction of 31%, 46%, 65% and 69% in tumor multiplicity, which were all statistically significant (p < 0.05). Analyses of lung adenoma tissues derived from kava-treated animals revealed that kava significantly inhibited adenoma cell proliferation while it had no detectable effect on cell death, indicating that kava primarily suppressed lung tumorigenesis in A/J mice via inhibition of cell proliferation. Flavokawains A, B, and C, three chalcone-based components from kava, demonstrated greatly reduced chemopreventive efficacies even at concentrations much higher than their natural abundance, suggesting that they alone were unlikely to be responsible for kava's chemopreventive activity. Kava at all dosages and treatment regimens did not induce detectable adverse effects, particularly with respect to liver. Specifically, kava treatment showed no effect on liver integrity indicator enzymes or liver weight, indicating that kava may be potentially safe for long-term chemopreventive application.

Metabolism of [D10]phenanthrene to tetraols in smokers for potential lung cancer susceptibility assessment: comparison of oral and inhalation routes of administration

Polycyclic aromatic hydrocarbons (PAHs) are believed to be among the causative agents for lung cancer in smokers. PAHs require metabolic activation for carcinogenicity. One pathway produces diol epoxides that react with DNA, causing mutations. Because diol epoxides are converted to tetraols, quantitation of tetraols can potentially be used to identify smokers who may be at higher risk for lung cancer. Our approach uses [D(10)]phenanthrene, a labeled version of phenanthrene, a noncarcinogenic PAH structurally analogous to carcinogenic PAH. Although smokers are exposed to PAH by inhalation, oral dosing would be more practical for phenotyping studies. Therefore, we investigated [D(10)]phenanthrene metabolism in smokers after administration by inhalation in cigarette smoke or orally. Sixteen smokers received 10 μg of [D(10)]phenanthrene in a cigarette or orally. Plasma and urine samples were analyzed for [D(10)]r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene ([D(10)]PheT), the major end product of the diol epoxide pathway, by gas chromatography-negative ion chemical ionization-tandem mass spectrometry. The ratios of [D(10)]PheT (oral dosing/inhalation) in 15 smokers were 1.03 ± 0.32 and 1.02 ± 0.35, based on plasma area under the concentration-time curve (0-∞) and total 48-h urinary excretion, respectively. Overall, there was no significant difference in the extent of [D(10)]PheT formation after the two different routes of exposure in smokers. A large interindividual variation in [D(10)]PheT formation was observed. These results demonstrate that the level of [D(10)]PheT in urine after oral dosing of [D(10)]phenanthrene can be used to assess individual capacity of PAH metabolism by the diol epoxide pathway.

Evolution of research on the DNA adduct chemistry of N-nitrosopyrrolidine and related aldehydes

This perspective reviews our work on the identification of DNA adducts of N-nitrosopyrrolidine and some related aldehydes. The research began as a focused project to investigate mechanisms of cyclic nitrosamine carcinogenesis but expanded into other areas, as aldehyde metabolites of NPYR were shown to have their own diverse DNA adduct chemistry. A total of 69 structurally distinct DNA adducts were identified, and some of these, found in human tissues, have provided intriguing leads for investigating carcinogenesis mechanisms in humans due to exposure to both endogenous and exogenous agents.

Abstract 3167: Comparison of the pharmacokinetics of phenanthrene in smokers after oral ingestion or inhalation through cigarettes for potential lung cancer susceptibility assessment

Polycyclic aromatic hydrocarbons (PAHs) are believed to be among the critical causative agents for lung cancer in smokers. PAHs require metabolic activation to elicit carcinogenic effects. Our hypothesis is that individuals who metabolically activate PAH more effectively will be at higher risk for lung cancer. Many studies investigated PAHs’ metabolism in human tissue in vitro or in animals. However, direct pharmacokinetics data in human are lacking. There are to our knowledge no data on human PAH pharmacokinetics after exposure by inhalation, from a cigarette or from any other source.

We used a unique approach employing a stable isotope labeled phenanthrene (Phe), the simplest PAH with a bay region, a feature closely associated with PAH carcinogenicity. Deuterated Phe ([D10]Phe) was administered to 15 subjects in a within-subject crossover and randomized clinical study, either by oral administration or by incorporation into cigarettes. Serial blood samples were taken at baseline and over 24 h after [D10]Phe administration. Urine was collected during 8 intervals over 48 h after dosing. Deuterated r,1-t-2,3, c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene ([D10]PheT), the metabolic activation end product, in blood and urine samples, was analyzed by GC-MS/MS. Two pharmacokinetic (PK) methods including plasma AUCs and the total amount of [D10]PheT excreted in the urine were used to determine the exposure to [D10]PheT after the two routes of administration.

Levels of [D10]PheT in plasma of all subjects were maximal 15-30 min after smoking a cigarette containing [D10]Phe, and decreased thereafter, which suggested that there was significant pulmonary “first-pass” formation of [D10]PheT. Maximum levels of [D10]PheT in plasma occurred between 30 to 150 min after oral ingestion. The relative exposure to [D10]PheT from oral dosing vs smoking was 0.92 ± 0.24 and 0.83 ± 0.28, based on the ratio of plasma AUCs and the ratio of the amount of PheT excreted in the urine, respectively. There was no statistically significant difference in [D10]PheT after two administration routes. There was large inter-individual variation in the capacity of generating [D10]PheT. The AUC ranged from 6560 to 92200 fmol-min/ml with a terminal elimination half-life of 290-681 min. Total urinary excretion ranged from 0.72% to 20.51% of initial dosing.

This study showed for the first time that the formation of PAH diol epoxides, as monitored by [D10]PheT, occurred with remarkable rapidity in all subjects after smoking. Oral dosing of [D10]Phe with subsequent urine collections will adequately reflect individual capacity to metabolically activate [D10]Phe. The results demonstrate that this approach is feasible for potentially identifying those individuals who have particularly high capacity to metabolic activate bay region-PAH.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3167. doi:10.1158/1538-7445.AM2011-3167

Abstract 4651: Analysis of 3,3′-diindolylmethane in urine after consumption of cruciferous vegetables in the Singapore Cohort Study

Background: Indole-3-carbinol (I3C) may be a chemopreventive agent against cancer. Until recently, there has not been a method to quantitatively assess human dietary I3C exposure or dietary exposure to its specific metabolites in biologic samples collected in a non-invasive manner. We have developed a LC-ESI-MS/MS-SRM analysis to quantify 3,3′-diindolylmethane (DIM), a specific metabolite of I3C in urine. This assay has not been validated as a biomarker of I3C intake in free-living people. Methods: We conducted a small feeding study involving 3 subjects. Subjects consumed approximately 300∼500 g of broccoli and collected 24 h urine samples. The developed LC-ESI-MS/MS-SRM analysis on urinary DIM assay showed the expected m/z 247 → 130 in all 24 h urine samples collected after consumption of broccoli; d2-DIM was used as an internal standard. The assay was then used to quantify urinary DIM in 246 subjects of the Singapore Chinese Health Study, a prospective, population-based cohort of middle aged Chinese men and women residing in Singapore. Random, non-fasting, non-timed urine samples were collected from the cohort between 1994 and 1999. Detailed dietary information and urinary levels of isothiocyanates (ITC) were available for these 246 subjects. The dietary information included intake of 8 cruciferous vegetables that had been previously assayed for glucobrassicins, the precursor of I3C.Estimated dietary intake of glucobrassicins was calculated for each individual based on reported intake of each cruciferous vegetable. Spearman correlation coefficients were calculated to determine the correlation between urinary DIM and reported intake of cruciferous vegetables. Results: Among the 246 subjects, urinary DIM levels ranged from undetectable to 167.8 pmol/mg Cr with a mean (sd) of 14.5 (9.59) pmol/mg Cr. The average intake of total cruciferous vegetables was 40.6 g/day and mean estimated intake of glucobrassicins was 6.5 µmol/day. The Spearman correlation coefficients (p-values) for urinary DIM and dietary intake of total cruciferous vegetables and estimated glucobrassicins were 0.09 (0.18) and 0.10 (0.10) respectively. The coefficients for urinary DIM and intake of each cruciferous vegetable were as follows: kaichoi, 0.01 (0.87); watercress, 0.09 (0.15); choisum, 0.04 (0.52); pakchoi, 0.01 (0.84); kailan, 0.02 (0.74), cabbage/wong nga pak, 0.14 (0.03); broccoli, 0.04 (0.58) and cauliflower, 0.14 (0.03). Urinary DIM also was statistically significantly, albeit weakly, associated with urinary total ITC (coefficient = 0.17, P=0.008), a validated biomarker for consumption of dietary ITC. Conclusion: Although lacking of a significant relationship with intake of total cruciferous vegetables, urinary DIM was statistically significantly associated with intake of cabbage/wong nga pak and cauliflower, two cruciferous vegetables with relatively high contents of I3C precursor.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4651. doi:10.1158/1538-7445.AM2011-4651