Induction of pulmonary neoplasia in the smoke-exposed ferret by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK): A model for human lung cancer

Care, management, and use of ferrets in biomedical research

The ferret (Mustela putorius furo) is a small domesticated species of the family Mustelidae within the order Carnivora. The present article reviews and discusses the current state of knowledge about housing, care, breeding, and biomedical uses of ferrets. The management and breeding procedures of ferrets resemble those used for other carnivores. Understanding its behavior helps in the use of environmental enrichment and social housing, which promote behaviors typical of the species. Ferrets have been used in research since the beginning of the twentieth century. It is a suitable non-rodent model in biomedical research because of its hardy nature, social behavior, diet and other habits, small size, and thus the requirement of a relatively low amount of test compounds and early sexual maturity compared with dogs and non-human primates. Ferrets and humans have numerous similar anatomical, metabolic, and physiological characteristics, including the endocrine, respiratory, auditory, gastrointestinal, and immunological systems. It is one of the emerging animal models used in studies such as influenza and other infectious respiratory diseases, cystic fibrosis, lung cancer, cardiac research, gastrointestinal disorders, neuroscience, and toxicological studies. Ferrets are vulnerable to many human pathogenic organisms, like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), because air transmission of this virus between them has been observed in the laboratory. Ferrets draw the attention of the medical community compared to rodents because they occupy a distinct niche in biomedical studies, although they possess a small representation in laboratory research.

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

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

Respiratory Disorders in Ferrets

Ferrets are susceptible to many disorders affecting the respiratory tract including both primary diseases and diseases of other body systems secondarily affecting the respiratory tract. Some primary respiratory diseases are shared with other mammal species including humans; potentially zoonotic diseases include important pathogens such as influenza and SARS-CoV-2. Other diseases include infections (bacterial, parasitic, and fungal) and neoplasia. A thorough workup is important to identify exact causes in order to formulate a treatment plan. Infectious diseases include bacterial, fungal, parasitic, and viral.

Dietary lycopene attenuates cigarette smoke-promoted nonalcoholic steatohepatitis by preventing suppression of antioxidant enzymes in ferrets

Cigarette smoke (CS) is an independent risk factor in development of nonalcoholic steatohepatitis (NASH) and fibrosis. Lycopene, a carotenoid naturally occurring in tomatoes, has been shown to be a protective agent against tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced NASH. In the present study using a ferret model we investigated whether CS promotes NASH and whether dietary lycopene can inhibit CS-promoted NASH development, and if so, what potential mechanisms were involved. Ferrets were divided into 4 groups (n=12-16/group): control, NNK/CS exposed, NNK/CS plus low-dose lycopene (2.2 mg/kg BW/day), and NNK/CS plus high-dose lycopene (6.6 mg/kg BW/day) groups, for 26 weeks. Results showed that hepatic steatosis, infiltrates of inflammatory cells, and the number and size of inflammatory foci in liver, together with key genes involved in hepatic fibrogenesis were higher in the NNK/CS group compared to the control group; a lycopene diet reversed these changes to the levels of the control group. Interestingly, a major lycopene cleavage enzyme, beta-carotene 9',10'-oxygenase (BCO2), which recently has been recognized to play metabolic roles beyond cleavage function, was down-regulated by NNK/CS exposure, but this decrease was prevented by lycopene feeding. NNK/CS exposure also downregulated liver expression of antioxidant enzymes and upregulated oxidative stress marker, which were all prevented by lycopene. In conclusion, our results suggest that CS can promote development of NASH and liver fibrosis in ferrets, which is associated with downregulation of BCO2 and impairment of antioxidant system in liver; dietary lycopene may inhibit CS-promoted NASH by preventing suppression of BCO2 and decline in antioxidant network.

Lycopene Inhibits Smoke-Induced Chronic Obstructive Pulmonary Disease and Lung Carcinogenesis by Modulating Reverse Cholesterol Transport in Ferrets

Chronic obstructive pulmonary disease (COPD) and lung cancer share the same etiologic factor, cigarette smoking. Higher consumption of dietary lycopene has been associated with lower risks of COPD and lung cancer in smokers. We investigated whether lycopene feeding protects against COPD and lung cancer in ferrets, a nonrodent model that closely mimics cigarette smoke (CS)-induced chronic bronchitis, emphysema, and lung tumorigenesis in human. We also explored whether the protective effect of lycopene is associated with restoring reverse cholesterol transport (RCT), a key driver in persistent inflammation with CS exposure. Ferrets (4 groups, n = 12-16/group) were exposed to a combination of tobacco carcinogen (NNK) and CS with or without consuming lycopene at low and high doses (equivalent to ∼30 and ∼90 mg lycopene/day in human, respectively) for 22 weeks. Results showed that dietary lycopene at a high dose significantly inhibited NNK/CS-induced chronic bronchitis, emphysema, and preneoplastic lesions, including squamous metaplasia and atypical adenomatous hyperplasia, as compared with the NNK/CS alone (P < 0.05). Lycopene feeding also tended to decrease the lung neoplastic lesions. Furthermore, lycopene feeding significantly inhibited NNK/CS-induced accumulation of total cholesterol, and increased mRNA expression of critical genes related to the RCT (PPARα, LXRα, and ATP-binding cassette transporters ABCA1 and ABCG1) in the lungs, which were downregulated by the NNK/CS exposure. The present study has provided the first evidence linking a protective role of dietary lycopene against COPD and preneoplastic lesions to RCT-mediated cholesterol accumulation in lungs.

Antitumoral effect of maintained neutrophilia induced by rhG-CSF in a murine model of pancreatic cancer

Although the protumoral functions of polymorphonuclear neutrophils are well known, some now-forgotten studies report antitumoral roles for these cells. The present work examines the antitumoral effect of maintained neutrophilia induced via the injection of recombinant human granulocyte colony stimulating factor (rhG-CSF, 100 μg/kg/day) in a Panc-1 subcutaneous xenograft murine model of pancreatic cancer. This treatment was compared with gemcitabine administration (120 mg/kg every two days) and a saline control (n = 6–7 mice per group). Compared to the controls, both the rhG-CSF- and gemcitabine-treated mice showed significantly suppressed tumor growth by day 4 (p < 0.001 and p = 0.013 respectively). From a mean starting volume of 106.9 ± 3.1 mm³ for all treatment groups, the final mean tumor volumes reached were 282.0 ± 30.7 mm³ for the rhG-CSF-treated mice, 202.6 ± 18.1 mm³ for the gemcitabine-treated mice and 519.4 ± 62.9 mm³ for the control mice (p < 0.004 and p < 0.01, respectively, vs. control). The rhG-CSF-treated tumors showed higher percentage necrosis than those treated with gemcitabine (37.4 ± 4.6 vs. 7.5 ± 3.0; p < 0.001). This is the first report of a clear anti-tumoral effect of rhG-CSF when used in monotherapy against pancreatic cancer. Since rhG-CSF administration is known to be associated with very few adverse events, it may offer an attractive alternative in the clinical treatment of pancreatic cancer.

An Updated Review of Inhalation Studies with Cigarette Smoke in Laboratory Animals

Until recently, the published literature on inhalation studies with laboratory animals and cigarette smoke consisted entirely of negative findings, as far as neoplastic disease is concerned. This paper brings readers up to date, with analyses of recent studies that do indeed appear to report success after so many years of failure. The paper consists of a brief analysis of the literature up until a couple of years ago, giving brief, representative examples of inhalation studies with the five main species of laboratory animals that have been used: rat, mouse, hamster, dog, and nonhuman primate. A brief examination of the various technologies used to expose laboratory animals is given, along with an analysis of the histopathology and related toxicology data (specifically, biomarkers of exposure) that have been reported. The paper concludes by briefly mentioning the most recent studies, where positive results have been reported.

Tobacco carcinogen NNK-induced lung cancer animal models and associated carcinogenic mechanisms

Tobacco usage is a major risk factor in the development, progression, and outcomes for lung cancer. Of the carcinogens associated with lung cancer, tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is among the most potent ones. The oncogenic mechanisms of NNK are not entirely understood, hindering the development of effective strategies for preventing and treating smoking-associated lung cancers. Here, we introduce the NNK-induced lung cancer animal models in different species and its potential mechanisms. Finally, we summarize several chemopreventive agents developed from these animal models.

Biology and Diseases of Ferrets

Ferrets (Mustela putorius furo) belong to the ancient family Mustelidae, which is believed to date back to the Eocene period, some 40 million years ago. The taxonomic groups in the family Mustelidae, as recognized by Nowak (1999), include 67 species in 25 genera from North, Central, and South America; Eurasia; and Africa. No other carnivore shows such diversity of adaptation, being found in a wide variety of ecosystems ranging from arctic tundra to tropical rainforests. Mustelids have retained many primitive characteristics, which include relatively small size, short stocky legs, five toes per foot, elongated braincase, and short rostrum (Anderson, 1989). The Mustelinae is the central subfamily of the Mustelidae. The best-known members of the Mustelinae are the weasels, mink, ferrets (genus Mustela), and the martens (genus Martes) (Anderson, 1989). The genus Mustela is divided into five subgenera: Mustela (weasels), Lutreola (European mink), Vison (American mink), Putorius (ferrets), and Grammogale (South American weasels). The smallest member of the Mustelidae family is the least weasel (Mustela nivalis), which weighs as little as 25 g, and the largest member is the sea otter (Enhydra lutris), which can weigh as much as 45 kg (Nowak, 1999).

Isolation, characterization, and functional analysis of ferret lymphatic endothelial cells

The lymphatic endothelium (LE) serves as a conduit for transport of immune cells and soluble antigens from peripheral tissues to draining lymph nodes (LNs), contributing to development of host immune responses and possibly dissemination of microbes. Lymphatic endothelial cells (LECs) are major constituents of the lymphatic endothelium. These specialized cells could play important roles in initiation of host innate immune responses through sensing of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs), including toll-like receptors (TLRs). LECs secrete pro-inflammatory cytokines and chemokines to create local inflammatory conditions for recruitment of naïve antigen presenting cells (APCs) such as dendritic cells (DCs) to sites of infection and/or vaccine administration. In this study, we examined the innate immune potential of primary LEC populations derived from multiple tissues of an animal model for human infectious diseases - the ferret. We generated a total of six primary LEC populations from lung, tracheal, and mesenteric LN tissues from three different ferrets. Standard RT-PCR characterization of these primary LECs showed that they varied in their expression of LEC markers. The ferret LECs were examined for their ability to respond to poly I:C (TLR3 and RIG-I ligand) and other known TLR ligands as measured by production of proinflammatory cytokine (IFNα, IL6, IL10, Mx1, and TNFα) and chemokine (CCL5, CCL20, and CXCL10) mRNAs using real time RT-PCR. Poly I:C exposure induced robust proinflammatory responses by all of the primary ferret LECs. Chemotaxis was performed to determine the functional activity of CCL20 produced by the primary lung LECs and showed that the LEC-derived CCL20 was abundant and functional. Taken together, our results continue to reveal the innate immune potential of primary LECs during pathogen-host interactions and expand our understanding of the roles LECs might play in health and disease in animal models.

Development of ferret as a human lung cancer model by injecting 4-(Nmethyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

OBJECTIVE

Development of new animal lung cancer models that are relevant to human lung carcino-genesis is important for lung cancer research. Previously we have shown the induction of lung tumor in ferrets (Mustela putorius furo) exposed to both tobacco smoke and a tobacco carcinogen (4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone, NNK). In the present study, we investigated whether NNK treatment alone induces both preneoplastic and neoplastic lesions in the lungs of ferrets.

METHODS

We exposed ferrets to NNK by i.p. injection of NNK (50 mg/kg BW) once a month for four consecutive months and then followed up for 24, 26 and 32 weeks. The incidences of pulmonary pre-neoplastic and neoplastic lesions were assessed by histopathological examination. The expressions of 7 nicotinic acetylcholine receptor ( 7 nAChR, which has been shown to promote lung carcinogenesis)and its related molecular biomarkers in lungs were examined by immunohistochemistry and/or Western blotting analysis.

RESULTS

Ferrets exposed to NNK alone developed both preneoplastic lesions (squamous metaplasia, dysplasia and atypical adenomatous hyperplasia) and tumors (squamous cell carcinoma, adenocarcinoma and adenosquamous carcinoma), which are commonly seen in humans. The incidence of tumor induced by NNK was time-dependent in the ferrets (16.7%, 40.0% and 66.7% for 24, 26 and 32 weeks, respectively). 7 nAChR is highly expressed in the ferret bronchial/bronchiolar epithelial cells, and alveolar macrophages in ferrets exposed to NNK, and in both squamous cell carcinoma and adenocarcinoma of the ferrets. In addition, we observed the tendency for an increase in phospho-ERK and cyclin D1 protein levels (p = 0.081 and 0.080, respectively) in the lungs of ferrets exposed to NNK.

CONCLUSION

The development of both preneoplastic and neoplastic lesions in ferret lungs by injecting NNK alone provides a simple and highly relevant non-rodent model for studying biomarkers/molecular targets for the prevention, detection and treatment of lung carcinogenesis in humans.

Polymorphonuclear neutrophils and cancer: intense and sustained neutrophilia as a treatment against solid tumors

Polymorphonuclear neutrophils (PMN) are the most abundant circulating immune cells and represent the first line of immune defense against infection. This review of the biomedical literature of the last 40 years shows that they also have a powerful antitumoral effect under certain circumstances. Typically, the microenvironment surrounding a solid tumor possesses many of the characteristics of chronic inflammation, a condition considered very favorable for tumor growth and spread. However, there are many circumstances that shift the chronic inflammatory state toward an acute inflammatory response around a tumor. This shift seems to convert PMN into very efficient anticancer effector cells. Clinical reports of unexpected antitumoral effects linked to the prolonged use of granulocyte colony-stimulating factor, which stimulates an intense and sustained neutrophilia, suggest that an easy way to fight solid tumors would be to encourage the development of intense peritumoral PMN infiltrates. Specifically designed clinical trials are urgently needed to evaluate the safety and efficacy of such drug-induced neutrophilia in patients with solid tumors. This antitumoral role of neutrophils may provide new avenues for the clinical treatment of cancer.

Animal models in carotenoids research and lung cancer prevention

Numerous epidemiological studies have consistently demonstrated that individuals who eat more fruits and vegetables (which are rich in carotenoids) and who have higher serum β-carotene levels have a lower risk of cancer, especially lung cancer. However, two human intervention trials conducted in Finland and in the United States have reported contrasting results with high doses of β-carotene supplementation increasing the risk of lung cancer among smokers. The failure of these trials to demonstrate actual efficacy has resulted in the initiation of animal studies to reproduce the findings of these two studies and to elucidate the mechanisms responsible for the harmful or protective effects of carotenoids in lung carcinogenesis. Although these studies have been limited by a lack of animal models that appropriately represent human lung cancer induced by cigarette smoke, ferrets and A/J mice are currently the most widely used models for these types of studies. There are several proposed mechanisms for the protective effects of carotenoids on cigarette smoke-induced lung carcinogenesis, and these include antioxidant/prooxidant effects, modulation of retinoic acid signaling pathway and metabolism, induction of cytochrome P450, and molecular signaling involved in cell proliferation and/or apoptosis. The technical challenges associated with animal models include strain-specific and diet-specific effects, differences in the absorption and distribution of carotenoids, and differences in the interactions of carotenoids with other antioxidants. Despite the problems associated with extrapolating from animal models to humans, the understanding and development of various animal models may provide useful information regarding the protective effects of carotenoids against lung carcinogenesis.

A further review of inhalation studies with cigarette smoke and lung cancer in experimental animals, including transgenic mice

CONTEXT

The lack of an effective animal model for pulmonary carcinogenesis in smokers is a continuing problem for researchers trying to design Potentially Reduced Risk Products for those smokers who are either unwilling or unable to quit smoking. The major failing of inhalation assays with cigarette smoke in laboratory animals is that these assays produce only small percentages of animals with pulmonary tumors (e.g. adenomas, with the occasional adenocarcinoma), as opposed to the highly invasive carcinomas (e.g. small cell and squamous cell) seen in smokers.

OBJECTIVE

To update previous reviews on animal models, and to add different types of transgenic (Tg) mice to the review.

METHODS

Reviews were made of articles retrieved from PubMed and elsewhere.

RESULTS

The addition of Tg mice to the arsenal of tests used for the evaluation of the carcinogenic potential of cigarettes did not result in any better understanding of the inability of such testing to reflect the epidemiological evidence for lung cancer in smokers.

CONCLUSION

As in previous reviews on the subject, the best assay providing support for the epidemiology data is still the 5-month whole-body exposure of male A/J mice to a combination of mainstream/sidestream smoke, followed by a 4-month recovery.

Beta-carotene and lung cancer in smokers: review of hypotheses and status of research

A number of epidemiological studies have reported associations of beta-carotene plasma levels or intake with decreased lung cancer risk. However, intervention studies in smokers have unexpectedly reported increased lung tumor rates after high, long-term, beta-carotene supplementation. Recently, detailed analyses by stratification for smoking habits of several large, long-term intervention or epidemiological trials are now available. The ATBC study, the CARET study, the Antioxidant Polyp Prevention trial, and the E3N study provide evidence that the adverse effects of beta-carotene supplementation are correlated with the smoking status of the study participants. In contrast, the Physician Health Study, the Linxian trial, and a pooled analysis of 7 epidemiological cohort studies have not supported this evidence. The ferret and A/J mouse lung cancer model have been used to investigate the mechanism of interaction of beta-carotene with carcinogens in the lung. Both models have specific advantages and disadvantages. There are a number of hypotheses concerning the beta-carotene/tobacco smoke interaction including alterations of retinoid metabolism and signaling pathways and interaction with CYP enzymes and pro-oxidation/DNA oxidation. The animal models consistently demonstrate negative effects only in the ferret, and following dosing with beta-carotene in corn oil at pharmacological dosages. No effects or even protective effects against smoke or carcinogen exposure were observed when beta-carotene was applied at physiological dosages or in combination with vitamins C and E, either as a mixture or in a stable formulation. In conclusion, human and animal studies have shown that specific circumstances, among them heavy smoking, seem to influence the effect of high beta-carotene intakes. In normal, healthy, nonsmoking populations, there is evidence of beneficial effects.

Tumorigenesis in B6C3F1 mice exposed to ozone in combination with 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone and dietary dibutyl phthalate

Although ozone exposure has been suspected as a risk factor for the development of lung cancer, data are still inconclusive. Studies in the literature infrequently recognize that the potential toxicity of ozone could be influenced by the combined exposure with other environmental carcinogens. To evaluate the carcinogenic potential of ozone alone or in combination with other toxicants, male and female B6C3F1 mice were exposed through inhalation and diet, to 0.5 ppm of ozone, 1.0 mg/kg of 4-( N-methyl- N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), 5000 ppm of dibutyl phthalate (DBP), individually and in combination for 1 year. No treatment-related death was seen, but significant differences in body and organ weights between control and treated mice were observed during the study. No tumor incidence was found in mice of either gender exposed to ozone alone. Pulmonary neoplasms were found in both, male and female mice exposed to NNK alone and in combination, ozone with NNK only or NNK plus DBP. Oviductal carcinomas were observed in females exposed to DBP alone and together with ozone plus NNK. These results indicate that ozone alone is not a lung carcinogen and in conjunction with NNK and/or DBP have no effect on tumor development in B6C3F1 mice under our experimental conditions.

A prospectively measured serum biomarker for a tobacco-specific carcinogen and lung cancer in smokers

BACKGROUND

No prior studies have related a tobacco-specific carcinogen to the risk of lung cancer in smokers. Of the over 60 known carcinogens in cigarette smoke, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is specific to tobacco and causes lung cancer in laboratory animals. Its metabolites, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL), have been studied as biomarkers of exposure to NNK. We studied the relation of prospectively measured NNK biomarkers to lung cancer risk.

METHODS

In a case-control study nested in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we randomly selected 100 lung cancer cases and 100 controls who smoked at baseline and analyzed their baseline serum for total NNAL, cotinine, and r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT), a biomarker of polycyclic aromatic hydrocarbon exposure and metabolic activation. To examine the association of the biomarkers with all lung cancers and for histologic subtypes, we computed odds ratios for total NNAL, PheT, and cotinine using logistic regression to adjust for potential confounders.

FINDINGS

Individual associations of age, smoking duration, and total NNAL with lung cancer risk were statistically significant. After adjustment, total NNAL was the only biomarker significantly associated with risk (odds ratio, 1.57 per unit SD increase; 95% confidence interval, 1.08-2.28). A similar statistically significant result was obtained for adenocarcinoma risk, but not for nonadenocarcinoma.

CONCLUSIONS

This first reporting of the effect of the prospectively measured tobacco-specific biomarker total NNAL, on risk of lung cancer in smokers provides insight into the etiology of smoking-related lung cancer and reinforces targeting NNK for cancer prevention.

Position-dependent expression of GADD45alpha in rat brain tumours

Although the complex and multifactorial process of tumour growth has been extensively studied for decades, our understanding of the fundamental relationship between tumour growth dynamics and genetic expression profile remains incomplete. Recent studies of tumour dynamics indicate that gene expression in solid tumours would depend on the distance from the centre of the tumour. Since tumour proliferative activity is mainly localised to its external zone, and taking into account that generation and expansion of genetic mutations depend on the number of cell divisions, important differences in gene expression between central and peripheral sections of the same tumour are to be expected. Here, we have studied variations in the genetic expression profile between peripheral and internal samples of the same brain tumour. We have carried out microarray analysis of mRNA expression, and found a differential profile of genetic expression between the two cell subsets. In particular, one major nuclear protein that regulates cell responses to DNA-damaging and stress signals, GADD45alpha, was expressed at much lower levels in the peripheral zone, as compared to tumour core samples. These differences in GADD45alpha mRNA transcription levels have been confirmed by quantitative analysis via real time PCR, and protein levels of GADD45alpha also exhibit the same pattern of differential expression. Our findings suggest that GADD45alpha might play a major role in the regulation of brain tumour invasive potential.

The effects of combined antioxidant (beta-carotene, alpha-tocopherol and ascorbic acid) supplementation on antioxidant capacity, DNA single-strand breaks and levels of insulin-like growth factor-1/IGF-binding protein 3 in the ferret model of lung cancer

Insulin-like growth factor 1 (IGF-1) and its major binding protein, IGF binding protein 3 (IGFBP-3) are implicated in lung cancer and other malignancies. We have previously shown that the combination of three major antioxidants [beta-carotene (BC), alpha-tocopherol (AT) and ascorbic acid (AA)] can prevent lung carcinogenesis in a 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-treated and smoke-exposed (SM) ferret model, which is highly analogous to humans. The present study is aimed at determining the effect of the combination of BC, AT and AA on antioxidant capacity, lymphocyte DNA damage, plasma IGF-1 and IGFBP-3 concentrations, as well as on IGF-1/IGFBP-3 mRNA expression in the tissues (lung and liver) of the ferrets. Ferrets were treated with or without combined antioxidant (BC, AT and AA) supplementation (AOX) for 6 months in the following 4 groups: (i) control; (ii) SM+NNK; (iii) AOX; and (iv) SM+NNK+AOX. Combined AOX supplementation significantly attenuated SM+NNK induced lymphocyte DNA damage in the ferret, while increasing resistance to oxidative damage when challenged with H(2)O(2) in vitro. Ferrets treated with SM+NNK had significantly lower IGFBP-3 mRNA expression in lungs, whereas there was significantly higher IGFBP-3 mRNA expression in the liver, as well as higher circulating IGFBP-3 concentrations. Combined AOX supplementation did not affect the plasma or tissue (lung and liver) ratio of IGF-1/IGFBP-3. Combined antioxidant supplementation provides protection against smoke-induced oxidative DNA damage, but does not affect the IGF-1/IGFBP-3 system. Differential expression of IGFBP-3 in different tissues indicates that caution should be taken when using plasma IGFBP-3 as a biomarker of tissue status.

Cigarette smoke impairs NK cell-dependent tumor immune surveillance

In this study, we investigated the impact of cigarette smoke on tumor immune surveillance and its consequences to lung tumor burden in a murine lung metastasis model. Cigarette smoke exposure significantly increased the numbers of lung metastases following B16-MO5 melanoma challenge. This effect was reversible; we observed significantly fewer tumor nodules following smoking cessation. Using RAG2(-/-) and RAG2(-/-)gamma(c)(-/-) mice, we provide strong evidence that increased tumor incidence was NK cell dependent. Furthermore, we show that cigarette smoke suppressed NK activation and attenuated NK CTL activity, without apparent effect on activating or inhibitory receptor expression. Finally, activation of NK cells through bone marrow-derived dendritic cells conferred protection against lung metastases in smoke-exposed mice; however, protection was not as efficacious as in sham-exposed mice. To our knowledge, this is the first experimental evidence showing that cigarette smoke impairs NK cell-dependent tumor immune surveillance and that altered immunity is associated with increased tumor burden. Our findings suggest that altered innate immunity may contribute to the increased risk of cancer in smokers.

Wnt and Hedgehog are critical mediators of cigarette smoke-induced lung cancer

Background

Lung cancer is the leading cause of cancer death in the world, and greater than 90% of lung cancers are cigarette smoke-related. Current treatment options are inadequate, because the molecular basis of cigarette-induced lung cancer is poorly understood.

Methodology/Principal Findings

Here, we show that human primary or immortalized bronchial epithelial cells exposed to cigarette smoke for eight days in culture rapidly proliferate, show anchorage-independent growth, and form tumors in nude mice. Using this model of the early stages of smoke-induced tumorigenesis, we examined the molecular changes leading to lung cancer. We observed that the embryonic signaling pathways mediated by Hedgehog and Wnt are activated by smoke. Pharmacological inhibition of these pathways blocked the transformed phenotype.

Conclusions/Significance

These experiments provide a model in which the early stages of smoke-induced tumorigenesis can be elicited, and should permit us to identify molecular changes driving this process. Results obtained so far indicate that smoke-induced lung tumors are driven by activation of two embryonic regulatory pathways, Hedgehog (Hh) and Wnt. Based on the current and emerging availability of drugs to inhibit Hh and Wnt signaling, it is possible that an understanding of the role of Hh and Wnt in lung cancer pathogenesis will lead to the development of new therapies.

The effect of pressure on the growth of tumour cell colonies

This paper describes some experiments on the manner in which external pressure affects cell colony growth in general, and tumour growth in particular. More precisely, our results show that cell colony borders growing under high-pressure conditions have geometrical and dynamical properties that are markedly different from those corresponding to growth under homeostatic, normal pressure conditions. These behaviours are characterized by means of the so-called dynamical exponents of each type of growth. These are shown to correspond to statistical properties of solutions of some stochastic partial differential equations that account for the evolution of the interface between the expanding colony and the surrounding medium.

Combined antioxidant (beta-carotene, alpha-tocopherol and ascorbic acid) supplementation increases the levels of lung retinoic acid and inhibits the activation of mitogen-activated protein kinase in the ferret lung cancer model

Interactions among beta-carotene (BC), alpha-tocopherol (AT) and ascorbic acid (AA) led to the hypothesis that using a combination of these antioxidants could be more beneficial than using a single antioxidant alone, particularly against smoke-related lung cancer. In this investigation, we have conducted an animal study to determine whether combined BC, AT and AA supplementation (AOX) protects against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung carcinogenesis in smoke-exposed (SM) ferrets. Ferrets were treated for 6 months in the following four groups: (i) control, (ii) SM + NNK, (iii) AOX and (iv) SM + NNK + AOX. Results showed that the combined AOX supplementation (i) prevented the SM + NNK-decreased lung concentrations of retinoic acid (RA) and BC; (ii) inhibited the SM + NNK-induced phosphorylation of Jun N-terminal kinase (JNK), extracellular-signal-regulated protein kinase (ERK) and proliferating cellular nuclear antigen proteins in the lungs of ferrets; and (iii) blocked the SM + NNK-induced up-regulation of total p53 and Bax proteins, as well as phosphorylated p53 in the lungs of ferrets. In addition, there were no lesions observed in the lung tissue of ferrets in the control and/or the AOX groups after 6 months of intervention, but combined AOX supplementation resulted in a trend toward lower incidence of both preneoplastic lung lesions and lung tumor formation in SM + NNK + AOX group of ferrets, as compared with the SM + NNK group alone. These data indicate that combined AOX supplementation could be a useful chemopreventive strategy against lung carcinogenesis through maintaining normal tissue levels of RA and inhibiting the activation of mitogen-activated protein kinase pathways, cell proliferation and phosphorylation of p53.