Prevention of cigarette smoke-induced lung tumors in mice by budesonide, phenethyl isothiocyanate, and N-acetylcysteine

Inhaled Medicines for Targeting Non-Small Cell Lung Cancer

Throughout the years, considerable progress has been made in methods for delivering drugs directly to the lungs, which offers enhanced precision in targeting specific lung regions. Currently, for treatment of lung cancer, the prevalent routes for drug administration are oral and parenteral. These methods, while effective, often come with side effects including hair loss, nausea, vomiting, susceptibility to infections, and bleeding. Direct drug delivery to the lungs presents a range of advantages. Notably, it can significantly reduce or even eliminate these side effects and provide more accurate targeting of malignancies. This approach is especially beneficial for treating conditions like lung cancer and various respiratory diseases. However, the journey towards perfecting inhaled drug delivery systems has not been without its challenges, primarily due to the complex structure and functions of the respiratory tract. This comprehensive review will investigate delivery strategies that target lung cancer, specifically focusing on non-small-cell lung cancer (NSCLC)-a predominant variant of lung cancer. Within the scope of this review, active and passive targeting techniques are covered which highlight the roles of advanced tools like nanoparticles and lipid carriers. Furthermore, this review will shed light on the potential synergies of combining inhalation therapy with other treatment approaches, such as chemotherapy and immunotherapy. The goal is to determine how these combinations might amplify therapeutic results, optimizing patient outcomes and overall well-being.

Mechanisms behind context-dependent role of glucocorticoids in breast cancer progression

Glucocorticoids (GCs), mostly dexamethasone (dex), are routinely administered as adjuvant therapy to manage side effects in breast cancer. However, recently, it has been revealed that dex triggers different effects and correlates with opposite outcomes depending on the breast cancer molecular subtype. This has raised new concerns regarding the generalized use of GC and suggested that the context-dependent effects of GCs can be taken into potential consideration during treatment design. Based on this, attention has recently been drawn to the role of the glucocorticoid receptor (GR) in development and progression of breast cancer. Therefore, in this comprehensive review, we aimed to summarize the different mechanisms behind different context-dependent GC actions in breast cancer by applying a multilevel examination, starting from the association of variants of the GR-encoding gene to expression at the mRNA and protein level of the receptor, and its interactions with other factors influencing GC action in breast cancer. The role of GCs in chemosensitivity and chemoresistance observed during breast cancer therapy is discussed. In addition, experiences using GC targeting therapeutic options (already used and investigated in preclinical and clinical trials), such as classic GC dexamethasone, selective glucocorticoid receptor agonists and modulators, the GC antagonist mifepristone, and GR coregulators, are also summarized. Evidence presented can aid a better understanding of the biology of context-dependent GC action that can lead to further advances in the personalized therapy of breast cancer by the evaluation of GR along with the conventional estrogen receptor (ER) and progesterone receptor (PR) in the routine diagnostic procedure.

Glucocorticoid receptor triggers a reversible drug-tolerant dormancy state with acquired therapeutic vulnerabilities in lung cancer

The glucocorticoid receptor (GR) regulates gene expression, governing aspects of homeostasis, but is also involved in cancer. Pharmacological GR activation is frequently used to alleviate therapy-related side-effects. While prior studies have shown GR activation might also have anti-proliferative action on tumours, the underpinnings of glucocorticoid action and its direct effectors in non-lymphoid solid cancers remain elusive. Here, we study the mechanisms of glucocorticoid response, focusing on lung cancer. We show that GR activation induces reversible cancer cell dormancy characterised by anticancer drug tolerance, and activation of growth factor survival signalling accompanied by vulnerability to inhibitors. GR-induced dormancy is dependent on a single GR-target gene, CDKN1C, regulated through chromatin looping of a GR-occupied upstream distal enhancer in a SWI/SNF-dependent fashion. These insights illustrate the importance of GR signalling in non-lymphoid solid cancer biology, particularly in lung cancer, and warrant caution for use of glucocorticoids in treatment of anticancer therapy related side-effects.

Rationale for the use of N-acetylcysteine in both prevention and adjuvant therapy of COVID-19

COVID‐19 may cause pneumonia, acute respiratory distress syndrome, cardiovascular alterations, and multiple organ failure, which have been ascribed to a cytokine storm, a systemic inflammatory response, and an attack by the immune system. Moreover, an oxidative stress imbalance has been demonstrated to occur in COVID‐19 patients. N‐ Acetyl‐L‐cysteine (NAC) is a precursor of reduced glutathione (GSH). Due to its tolerability, this pleiotropic drug has been proposed not only as a mucolytic agent, but also as a preventive/therapeutic agent in a variety of disorders involving GSH depletion and oxidative stress. At very high doses, NAC is also used as an antidote against paracetamol intoxication. Thiols block the angiotensin‐converting enzyme 2 thereby hampering penetration of SARS‐CoV‐2 into cells. Based on a broad range of antioxidant and anti‐inflammatory mechanisms, which are herein reviewed, the oral administration of NAC is likely to attenuate the risk of developing COVID‐19, as it was previously demonstrated for influenza and influenza‐like illnesses. Moreover, high‐dose intravenous NAC may be expected to play an adjuvant role in the treatment of severe COVID‐19 cases and in the control of its lethal complications, also including pulmonary and cardiovascular adverse events.

Role of Oxidative Stress in the Suppression of Immune Responses in Peripheral Blood Mononuclear Cells Exposed to Combustible Tobacco Product Preparation

Cigarette smoking is a major risk factor for several human diseases. Chronic inflammation, resulting from increased oxidative stress, has been suggested as a mechanism that contributes to the increased susceptibility of smokers to cancer and microbial infections. We have previously shown that whole-smoke conditioned medium (WS-CM) and total particulate matter (TPM) prepared from Kentucky 3R4F reference cigarettes [collectively called as combustible tobacco product preparations (TPPs)] potently suppressed agonist-stimulated cytokine secretion and target cell killing in peripheral blood mononuclear cells (PBMCs). Here we have investigated the role of oxidative stress from TPPs, which alters inflammatory responses in vitro. Particularly, we investigated the mechanisms of WS-CM-induced suppression of select cytokine secretions in Toll-like receptor (TLR) agonist-stimulated cells and target cell killing by effector cells in PBMCs. Pretreatment with N-acetyl cysteine (NAC), a precursor of reduced glutathione and an established anti-oxidant, protected against DNA damage and cytotoxicity caused by exposure to WS-CM. Similarly, secretion of tumor necrosis factor (TNF), interleukin (IL)-6, and IL-8 in response to TLR-4 stimulation was restored by pretreatment with NAC. Target cell killing, a functional measure of cytolytic cells in PBMCs, is suppressed by WS-CM. Pretreatment with NAC restored the target cell killing in WS-CM treated PBMCs. This was accompanied by higher perforin levels in the effector cell populations. Collectively, these data suggest that reducing oxidative stress caused by cigarette smoke components restores select immune responses in this ex vivo model.

Inhaled corticosteroids may prevent lung cancer in asthma patients

BACKGROUND

It is unclear whether inhaled corticosteroids (ICS) have chemopreventive effect on lung cancer (LC) development in humans. We investigated the association between the ICS use in asthma patients and the risk of LC.

METHODS

We conducted a nationwide, population-based retrospective cohort study using the National Health Insurance database. We identified 4210 asthmatics who were initially free of LC and regularly used ICS between 2001 and 2005 and 37,228 asthmatics without regular ICS use. Patients with documented history of tobacco use were excluded from the analyses. Asthmatics were categorized into a mild and a severe asthma group. Each patient was tracked until the end of 2010 to identify incident cases of LC. Cox proportional hazards models were used to evaluate the effect of ICS on the risk of LC, further stratifying by asthma severity and comorbidities.

RESULTS

During follow-up, we identified 747 incident cases of LC diagnosed in the asthma cohort. Compared with severe asthmatics without regular ICS use, the risk of LC for those with mild asthma with regular ICS use was lower (adjusted hazard ratio = 0.42, 95% confidence interval = 0.31-0.56, P < 0.0001). The risk of LC was calculated among the following rankings of risk severe asthma without regular ICS use, low severity without regular ICS, high severity with regular ICS, and low severity with regular ICS group showed a decreasing trend of LC incidence (P = 0.041). Analyses stratified by comorbidities revealed that the protective effect of ICS was assessed with better precision and more pronounced in those with renal diseases, stroke, and hyperlipidemia.

CONCLUSIONS

For patients with asthma, regular ICS use might have a protective effect against LC. Further studies are required to assess this potential association from both immunohistopathological and clinical aspects.

Exposure of Human Lung Cells to Tobacco Smoke Condensate Inhibits the Nucleotide Excision Repair Pathway

Exposure to tobacco smoke is the number one risk factor for lung cancer. Although the DNA damaging properties of tobacco smoke have been well documented, relatively few studies have examined its effect on DNA repair pathways. This is especially true for the nucleotide excision repair (NER) pathway which recognizes and removes many structurally diverse DNA lesions, including those introduced by chemical carcinogens present in tobacco smoke. The aim of the present study was to investigate the effect of tobacco smoke on NER in human lung cells. We studied the effect of cigarette smoke condensate (CSC), a surrogate for tobacco smoke, on the NER pathway in two different human lung cell lines; IMR-90 lung fibroblasts and BEAS-2B bronchial epithelial cells. To measure NER, we employed a slot-blot assay to quantify the introduction and removal of UV light-induced 6–4 photoproducts and cyclobutane pyrimidine dimers. We find a dose-dependent inhibition of 6–4 photoproduct repair in both cell lines treated with CSC. Additionally, the impact of CSC on the abundance of various NER proteins and their respective RNAs was investigated. The abundance of XPC protein, which is required for functional NER, is significantly reduced by treatment with CSC while the abundance of XPA protein, also required for NER, is unaffected. Both XPC and XPA RNA levels are modestly reduced by CSC treatment. Finally, treatment of cells with MG-132 abrogates the reduction in the abundance of XPC protein produced by treatment with CSC, suggesting that CSC enhances proteasome-dependent turnover of the protein that is mediated by ubiquitination. Together, these findings indicate that tobacco smoke can inhibit the same DNA repair pathway that is also essential for the removal of some of the carcinogenic DNA damage introduced by smoke itself, increasing the DNA damage burden of cells exposed to tobacco smoke.

Pharmacological Modulation of Lung Carcinogenesis in Smokers: Preclinical and Clinical Evidence

Many drugs in common use possess pleiotropic properties that make them capable of interfering with carcinogenesis mechanisms. We discuss here the ability of pharmacological agents to mitigate the pulmonary carcinogenicity of mainstream cigarette smoke. The evaluated agents include anti-inflammatory drugs (budesonide, celecoxib, aspirin, naproxen, licofelone), antidiabetic drugs (metformin, pioglitazone), antineoplastic agents (lapatinib, bexarotene, vorinostat), and other drugs and supplements (phenethyl isothiocyanate, myo-inositol, N-acetylcysteine, ascorbic acid, berry extracts). These drugs have been evaluated in mouse models mimicking interventions either in current smokers or in ex-smokers, or in prenatal chemoprevention. They display a broad spectrum of activities by attenuating either smoke-induced preneoplastic lesions or benign tumors and/or malignant tumors. Together with epidemiological data, these findings provide useful information to predict the potential effects of pharmacological agents in smokers.

N-acetylcysteine protects against liver injure induced by carbon tetrachloride via activation of the Nrf2/HO-1 pathway

Chronic liver injury is an important clinical problem which eventually leads to cirrhosis, hepatocellular carcinoma and end-stage liver failure. It is well known that cell damage induced by reactive oxygen species (ROS) is an important mechanism of hepatocyte injure. N-acetylcysteine (NAC), a precursor of glutathione (GSH), is well-known role as the antidote to acetaminophen toxicity in clinic. NAC is now being utilized more widely in the clinical setting for non-acetaminophen (APAP) related causes of liver injure. However, the mechanisms underlying its beneficial effects are poorly defined. Thus, Aim of the present study was to investigate potential hepatic protective role of NAC and to delineate its mechanism of action against carbon tetrachloride (CCl4)-induced liver injury in models of rat. Our results showed that the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities as well as malondialdehyde (MDA) contents decreased significantly in CCl4-induced rats with NAC treatment. GSH content and superoxide dismutase (SOD) activities remarkably increased in the NAC groups compared with those in CCl4-induced group. Treatment with NAC had been shown to an increase in nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) mRNA levels. In conclusion, these results suggested that NAC upregulated HO-1 through the activation of Nrf2 pathway and protected rat against CCl4-induced liver injure. The results of this study provided pharmacological evidence to support the clinical application of NAC.

Dietary agents for prevention and treatment of lung cancer

Lung cancer is a prominent cause of cancer-associated mortality worldwide. The main reason for high mortality due to lung cancer is attributable to the fact that the diagnosis is generally made when it has spread beyond a curable stage and cannot be treated surgically or with radiation therapy. Therefore, new approaches like dietary modifications could be extremely useful in reducing lung cancer incidences. Several fruits and vegetables offer a variety of bioactive compounds to afford protection against several diseases, including lung cancer. A number of research studies involving dietary agents provide strong evidence for their role in the prevention and treatment of lung cancer, and have identified their molecular mechanisms of action and potential targets. In this review article, we summarize data from in-vitro and in-vivo studies and where available, in clinical trials, on the effects of some of the most promising dietary agents against lung cancer.

Protective effects of N-acetylcysteine on cisplatin-induced oxidative stress and DNA damage in HepG2 cells

Hepatocyte injury is a common pathological effect of cisplatin (CDDP) in various solid tumor therapies. Thus, strategies for minimizing CDDP toxicity are of great clinical interest. N-acetylcysteine (NAC), a known antioxidant, is often used as an antidote for acetaminophen overdose in the clinic due to its ability to increase the levels of glutathione (GSH). In the present study, the aim was to investigate the protective effects of NAC against CDDP-induced apoptosis in human-derived HepG2 cells. The results showed that upon exposure of the cells to CDDP, oxidative stress was significantly induced. DNA damage caused by CDDP was associated with cell apoptosis. NAC pre-treatment significantly reduced the malondialdehyde (MDA) levels and ameliorated the GSH modulation induced by CDDP. NAC also protected against DNA damage and cell apoptosis. These data suggest the protective role of NAC against hepatocyte apoptosis induced by CDDP was achieved through the inhibition of DNA damage and alterations of the redox status in human derived HepG2 cells. These results indicate that NAC administration may protect against CDDP-induced damage.

Phenethyl isothiocyanate: a comprehensive review of anti-cancer mechanisms

The epidemiological evidence suggests a strong inverse relationship between dietary intake of cruciferous vegetables and the incidence of cancer. Among other constituents of cruciferous vegetables, isothiocyanates (ITC) are the main bioactive chemicals present. Phenethyl isothiocyanate (PEITC) is present as gluconasturtiin in many cruciferous vegetables with remarkable anti-cancer effects. PEITC is known to not only prevent the initiation phase of carcinogenesis process but also to inhibit the progression of tumorigenesis. PEITC targets multiple proteins to suppress various cancer-promoting mechanisms such as cell proliferation, progression and metastasis. Pre-clinical evidence suggests that combination of PEITC with conventional anti-cancer agents is also highly effective in improving overall efficacy. Based on accumulating evidence, PEITC appears to be a promising agent for cancer therapy and is already under clinical trials for leukemia and lung cancer. This is the first review which provides a comprehensive analysis of known targets and mechanisms along with a critical evaluation of PEITC as a future anti-cancer agent.

Assay of lapatinib in murine models of cigarette smoke carcinogenesis

Lapatinib, a dual tyrosine kinase inhibitor targeting the epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER-2), is prescribed for the treatment of patients with metastatic breast cancer overexpressing HER-2. Involvement of this drug in pulmonary carcinogenesis has been poorly investigated. We used murine models suitable to evaluate cigarette smoke-related molecular and histopathological alterations. A total of 481 Swiss H mice were used. The mice were exposed to mainstream cigarette smoke (MCS) during the first four months of life. After 10 weeks, MCS caused an elevation of bulky DNA adducts, oxidative DNA damage and an extensive downregulation of microRNAs in lung. After four months, an increase in micronucleus frequency was observed in peripheral blood erythrocytes. After 7.5 months, histopathological alterations were detected in the lung, also including benign tumors and malignant tumors, and in the urinary tract. A subchronic toxicity study assessed the non-toxic doses of lapatinib, administered daily with the diet after weaning. After 10 weeks, lapatinib significantly attenuated the MCS-related nucleotide changes and upregulated several low-intensity microRNAs in lung. The drug poorly affected the MCS systemic genotoxicity and had modest protective effects on MCS-induced preneoplastic lesions in lung and kidney, when administered under conditions that temporarily mimicked interventions either in current smokers or ex-smokers. On the other hand, it caused some toxicity to the liver. Thus, on the whole, lapatinib appears to have a low impact in the smoke-related lung carcinogenesis models used, especially in terms of tumorigenic response.

Modulation by metformin of molecular and histopathological alterations in the lung of cigarette smoke-exposed mice

The anti-diabetic drug metformin is endowed with anti-cancer properties. Epidemiological and experimental studies, however, did not provide univocal results regarding its role in pulmonary carcinogenesis. We used Swiss H mice of both genders in order to detect early molecular alterations and tumors induced by mainstream cigarette smoke. Based on a subchronic toxicity study, oral metformin was used at a dose of 800 mg/kg diet, which is 3.2 times higher than the therapeutic dose in humans. Exposure of mice to smoke for 4 months, starting at birth, induced a systemic clastogenic damage, formation of DNA adducts, oxidative DNA damage, and extensive downregulation of microRNAs in lung after 10 weeks. Preneoplastic lesions were detectable after 7.5 months in both lung and urinary tract along with lung tumors, both benign and malignant. Modulation by metformin of 42 of 1281 pulmonary microRNAs in smoke-free mice highlighted a variety of mechanisms, including modulation of AMPK, stress response, inflammation, NFκB, Tlr9, Tgf, p53, cell cycle, apoptosis, antioxidant pathways, Ras, Myc, Dicer, angiogenesis, stem cell recruitment, and angiogenesis. In smoke-exposed mice, metformin considerably decreased DNA adduct levels and oxidative DNA damage, and normalized the expression of several microRNAs. It did not prevent smoke-induced lung tumors but inhibited preneoplastic lesions in both lung and kidney. In conclusion, metformin was able to protect the mouse lung from smoke-induced DNA and microRNA alterations and to inhibit preneoplastic lesions in lung and kidney but failed to prevent lung adenomas and malignant tumors induced by this complex mixture.

Relationships between pulmonary micro-RNA and proteome profiles, systemic cytogenetic damage and lung tumors in cigarette smoke-exposed mice treated with chemopreventive agents

Assessing the correlation between molecular endpoints and cancer induction or prevention aims at validating the use of intermediate biomarkers. We previously developed murine models that are suitable to detect both the carcinogenicity of mainstream cigarette smoke (MCS) and the induction of molecular alterations. In this study, we used 931 Swiss mice in two parallel experiments and in a preliminary toxicity study. The chemopreventive agents included vorinostat, myo-inositol, bexarotene, pioglitazone and a combination of bexarotene and pioglitazone. Pulmonary micro-RNAs and proteins were evaluated by microarray analyses at 10 weeks of age in male and female mice, either unexposed or exposed to MCS since birth, and either untreated or receiving each one of the five chemopreventive regimens with the diet after weaning. At 4 months of age, the frequency of micronucleated normochromatic erythrocytes was evaluated. At 7 months, the lungs were subjected to standard histopathological analysis. The results showed that exposure to MCS significantly downregulated the expression of 79 of 694 lung micro-RNAs (11.4%) and upregulated 66 of 1164 proteins (5.7%). Administration of chemopreventive agents modulated the baseline micro-RNA and proteome profiles and reversed several MCS-induced alterations, with some intergender differences. The stronger protective effects were produced by the combination of bexarotene and pioglitazone, which also inhibited the MCS-induced clastogenic damage and the yield of malignant tumors. Pioglitazone alone increased the yield of lung adenomas. Thus, micro-RNAs, proteins, cytogenetic damage and lung tumors were closely related. The molecular biomarkers contributed to evaluate both protective and adverse effects of chemopreventive agents and highlighted the mechanisms involved.

Oncogenes and inflammation rewire host energy metabolism in the tumor microenvironment: RAS and NFκB target stromal MCT4

Here, we developed a model system to evaluate the metabolic effects of oncogene(s) on the host microenvironment. A matched set of "normal" and oncogenically transformed epithelial cell lines were co-cultured with human fibroblasts, to determine the "bystander" effects of oncogenes on stromal cells. ROS production and glucose uptake were measured by FACS analysis. In addition, expression of a panel of metabolic protein biomarkers (Caveolin-1, MCT1, and MCT4) was analyzed in parallel. Interestingly, oncogene activation in cancer cells was sufficient to induce the metabolic reprogramming of cancer-associated fibroblasts toward glycolysis, via oxidative stress. Evidence for "metabolic symbiosis" between oxidative cancer cells and glycolytic fibroblasts was provided by MCT1/4 immunostaining. As such, oncogenes drive the establishment of a stromal-epithelial "lactate-shuttle", to fuel the anabolic growth of cancer cells. Similar results were obtained with two divergent oncogenes (RAS and NFκB), indicating that ROS production and inflammation metabolically converge on the tumor stroma, driving glycolysis and upregulation of MCT4. These findings make stromal MCT4 an attractive target for new drug discovery, as MCT4 is a shared endpoint for the metabolic effects of many oncogenic stimuli. Thus, diverse oncogenes stimulate a common metabolic response in the tumor stroma. Conversely, we also show that fibroblasts protect cancer cells against oncogenic stress and senescence by reducing ROS production in tumor cells. Ras-transformed cells were also able to metabolically reprogram normal adjacent epithelia, indicating that cancer cells can use either fibroblasts or epithelial cells as "partners" for metabolic symbiosis. The antioxidant N-acetyl-cysteine (NAC) selectively halted mitochondrial biogenesis in Ras-transformed cells, but not in normal epithelia. NAC also blocked stromal induction of MCT4, indicating that NAC effectively functions as an "MCT4 inhibitor". Taken together, our data provide new strategies for achieving more effective anticancer therapy. We conclude that oncogenes enable cancer cells to behave as selfish "metabolic parasites", like foreign organisms (bacteria, fungi, viruses). Thus, we should consider treating cancer like an infectious disease, with new classes of metabolically targeted "antibiotics" to selectively starve cancer cells. Our results provide new support for the "seed and soil" hypothesis, which was first proposed in 1889 by the English surgeon, Stephen Paget.

Chemoprevention by N-acetylcysteine of low-dose CT-induced murine lung tumorigenesis

Data from the National Lung Screening Trial suggested that annual computed tomography (CT) screening of at-risk patients decreases lung cancer mortality by 20%. We assessed the effects of low-dose CT radiation in mice exposed to 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK) to mimic the effects of annual CT screening in heavy smokers and ex-smokers. A/J mice were treated at 8 weeks with NNK followed 1 week later by 4 weekly doses of 0, 10, 30 or 50 mGy of whole-body CT and euthanized 8 months later. Irradiated mice exhibited significant 1.8- to 2-fold increases in tumor multiplicity in males (16.1 ± 0.8 versus 9.1 ± 1.5 tumors per mouse; P < 0.0001) and females (21.6 ± 0.8 versus 10.5 ± 1.4 tumors per mouse; P < 0.0001), respectively, compared with unirradiated mice with no dose effect observed; female mice exhibited higher sensitivity to radiation exposure than did males (P < 0.0001). Similar results were obtained when tumor area was determined. To assess if the deleterious effects of radiation could be prevented by antioxidants, female mice were fed a diet containing 0.7% N-acetylcysteine (NAC) starting 3 days prior to the first CT exposure and continuing for a total of 5 weeks. NAC prevented CT induced increases in tumor multiplicity (10.5 ± 1.2 versus 20.7 ± 1.5 tumors per mouse; P < 0.0001) back to levels seen in NNK/unirradiated mice (10.5 ± 1.2). Our data suggest that exposure of sensitive populations to CT radiation increases the risk of tumorigenesis, and that antioxidants may prevent the long-term carcinogenic effects of low-dose radiation exposure. This would allow annual screening with CT while preventing the potential long-term toxicity of radiation exposure.

Inhibition of lung tumor development by berry extracts in mice exposed to cigarette smoke

Cigarette smoke (CS) and dietary factors play a major role in cancer epidemiology. At the same time, however, the diet is the richest source of anticancer agents. Berries possess a broad array of health protective properties and were found to attenuate the yield of tumors induced by individual carcinogens in the rodent digestive tract and mammary gland but failed to prevent lung tumors induced by typical CS components in mice. We exposed whole-body Swiss ICR mice to mainstream CS, starting at birth and continuing daily for 4 months. Aqueous extracts of black chokeberry and strawberry were given as the only source of drinking water, starting after weaning and continuing for 7 months, thus mimicking an intervention in current smokers. In the absence of berries, CS caused a loss of body weight, induced early cytogenetical damage in circulating erythrocytes and histopathological alterations in lung (emphysema, blood vessel proliferation, alveolar epithelial hyperplasia and adenomas), liver (parenchymal degeneration) and urinary bladder (epithelial hyperplasia). Both berry extracts inhibited the CS-related body weight loss, cytogenetical damage, liver degeneration, pulmonary emphysema and lung adenomas. Protective effects were more pronounced in female mice, which may be ascribed to modulation by berry components of the metabolism of estrogens implicated in lung carcinogenesis. Interestingly, both the carcinogen and the chemopreventive agents tested are complex mixtures that contain a multitude of components working through composite mechanisms.

N-acetylcysteine (NAC) diminishes the severity of PCB 126-induced fatty liver in male rodents

Potent aryl hydrocarbon receptor agonists like PCB 126 (3,3',4,4',5-pentachlorobiphenyl) cause oxidative stress and liver pathology, including fatty liver. Our question was whether dietary supplementation with N-acetylcysteine (NAC), an antioxidant, can prevent these adverse changes. Male Sprague-Dawley rats were fed a standard AIN-93G diet (sufficient in cysteine) or a modified diet supplemented with 1.0% NAC. After one week, rats on each diet were exposed to 0, 1, or 5μmol/kg body weight PCB 126 by i.p. injection (6 rats per group) and euthanized two weeks later. PCB-treatment caused a dose-dependent reduction in growth, feed consumption, relative thymus weight, total glutathione and glutathione disulfide (GSSG), while relative liver weight, glutathione transferase activity and hepatic lipid content were dose-dependently increased with PCB dose. Histologic examination of liver tissue showed PCB 126-induced hepatocellular steatosis with dose dependent increase in lipid deposition and distribution. Dietary NAC resulted in a reduction in hepatocellular lipid in both PCB groups. This effect was confirmed by gravimetric analysis of extracted lipids. Expression of CD36, a scavenger receptor involved in regulating hepatic fatty acid uptake, was reduced with high dose PCB treatment but unaltered in PCB-treated rats on NAC-supplemented diet. These results demonstrate that NAC has a protective effect against hepatic lipid accumulation in rats exposed to PCB 126. The mechanism of this protective effect appears to be independent of NAC as a source of cysteine/precursor of glutathione.

Thinking outside the cleft to understand synaptic activity: contribution of the cystine-glutamate antiporter (System xc-) to normal and pathological glutamatergic signaling

System x(c)(-) represents an intriguing target in attempts to understand the pathological states of the central nervous system. Also called a cystine-glutamate antiporter, system x(c)(-) typically functions by exchanging one molecule of extracellular cystine for one molecule of intracellular glutamate. Nonvesicular glutamate released during cystine-glutamate exchange activates extrasynaptic glutamate receptors in a manner that shapes synaptic activity and plasticity. These findings contribute to the intriguing possibility that extracellular glutamate is regulated by a complex network of release and reuptake mechanisms, many of which are unique to glutamate and rarely depicted in models of excitatory signaling. Because system x(c)(-) is often expressed on non-neuronal cells, the study of cystine-glutamate exchange may advance the emerging viewpoint that glia are active contributors to information processing in the brain. It is noteworthy that system x(c)(-) is at the interface between excitatory signaling and oxidative stress, because the uptake of cystine that results from cystine-glutamate exchange is critical in maintaining the levels of glutathione, a critical antioxidant. As a result of these dual functions, system x(c)(-) has been implicated in a wide array of central nervous system diseases ranging from addiction to neurodegenerative disorders to schizophrenia. In the current review, we briefly discuss the major cellular components that regulate glutamate homeostasis, including glutamate release by system x(c)(-). This is followed by an in-depth discussion of system x(c)(-) as it relates to glutamate release, cystine transport, and glutathione synthesis. Finally, the role of system x(c)(-) is surveyed across a number of psychiatric and neurodegenerative disorders.

The use of animal models for cancer chemoprevention drug development

Animal models currently are used to assess the efficacy of potential chemopreventive agents, including synthetic chemicals, chemical agents obtained from natural products, and natural product mixtures. The observations made in these models as well as other data are then used to prioritize agents to determine which are qualified to progress to clinical chemoprevention trials. Organ-specific animal models are employed to determine which agents or classes of agents are likely to be the most effective at nontoxic doses to prevent organ-specific forms of cancer. These results are then used to target specific organs in high-risk populations in clinical trials. The animal models used are either carcinogen-induced with carcinogens specific for particular organ sites or they are transgenic/mutant animals with insertions, deletions, or mutations at targeted gene sites known to enhance cancers in a specific organ. Animal tumor models with characteristics favorable to chemoprevention studies are available for cancers of the lung, colon, skin, bladder, mammary, prostate, head and neck, esophagus, ovary, and pancreas. In addition to single-agent dose-response testing, such models are frequently used for testing combinations of agents, testing different routes of administration, evaluating surrogate endpoint biomarkers, and generating initial pharmacokinetics and toxicology data. For some of the more standard animal models there is significant correlation with human chemopreventive trial results. There are a growing number of positive human chemoprevention trials that have used agents or combinations that were positive in animal testing. There have been fewer negative human clinical trials, but their results again correlate with negative animal results. Clearly the validation of animal models to predict the efficacy of agents in human clinical trials will await further human data on positive and negative outcomes with chemopreventive agents. Whether validated or not, animal efficacy data remain central to the clinical trial decision-making process.

Comparative functional genomics analysis of NNK tobacco-carcinogen induced lung adenocarcinoma development in Gprc5a-knockout mice

BACKGROUND

Improved understanding of lung cancer development and progression, including insights from studies of animal models, are needed to combat this fatal disease. Previously, we found that mice with a knockout (KO) of G-protein coupled receptor 5A (Gprc5a) develop lung tumors after a long latent period (12 to 24 months).

METHODOLOGY/PRINCIPAL FINDINGS

To determine whether a tobacco carcinogen will enhance tumorigenesis in this model, we administered 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) i.p. to 2-months old Gprc5a-KO mice and sacrificed groups (n=5) of mice at 6, 9, 12, and 18 months later. Compared to control Gprc5a-KO mice, NNK-treated mice developed lung tumors at least 6 months earlier, exhibited 2- to 4-fold increased tumor incidence and multiplicity, and showed a dramatic increase in lesion size. A gene expression signature, NNK-ADC, of differentially expressed genes derived by transcriptome analysis of epithelial cell lines from normal lungs of Gprc5a-KO mice and from NNK-induced adenocarcinoma was highly similar to differential expression patterns observed between normal and tumorigenic human lung cells. The NNK-ADC expression signature also separated both mouse and human adenocarcinomas from adjacent normal lung tissues based on publicly available microarray datasets. A key feature of the signature, up-regulation of Ube2c, Mcm2, and Fen1, was validated in mouse normal lung and adenocarcinoma tissues and cells by immunohistochemistry and western blotting, respectively.

CONCLUSIONS/SIGNIFICANCE

Our findings demonstrate that lung tumorigenesis in the Gprc5a-KO mouse model is augmented by NNK and that gene expression changes induced by tobacco carcinogen(s) may be conserved between mouse and human lung epithelial cells. Further experimentation to prove the reliability of the Gprc5a knockout mouse model for the study of tobacco-induced lung carcinogenesis is warranted.