Dose Of Carcinogen Research Articles

Quantitative analysis of mutagenicity and carcinogenicity of 2-amino-3-methylimidazo[4,5-f]quinoline in F344 gpt delta transgenic rats.

Quantitative analysis of the mutagenicity and carcinogenicity of the low doses of genotoxic carcinogens present in food is of pressing concern. The purpose of the present study was to determine the mutagenicity and carcinogenicity of low doses of the dietary genotoxic carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). Male F344 gpt delta transgenic rats were fed diets supplemented with 0, 0.1, 1, 10 or 100 ppm IQ for 4 weeks. The frequencies of gpt transgene mutations in the liver were significantly increased in the 10 and 100 ppm groups. In addition, the mutation spectra was altered in the 1, 10 and 100 ppm groups: frequencies of G:C to T:A transversion were significantly increased in groups administered 1, 10 and 100 ppm IQ in a dose-dependent manner, and the frequencies of G:C to A:T transitions, A:T to T:A transversions and A:T to C:G transversions were significantly increased in the 100 ppm group. Increased frequencies of single base pair deletions and Spi- mutants in the liver, and an increase in glutathione S-transferase placental form (GST-P)-positive foci, a preneoplastic lesion of the liver in rats, was also observed in the 100 ppm group. In contrast, neither mutations nor mutation spectra or GST-P-positive foci were statistically altered by administration of IQ at 0.1 ppm. We estimated the point of departure for the mutagenicity and carcinogenicity of IQ using the no-observed-effect level approach and the Benchmark dose approach to characterise the dose-response relationship of low doses of IQ. Our findings demonstrate the existence of no effect levels of IQ for both in vivo mutagenicity and hepatocarcinogenicity. The findings of the present study will facilitate an understanding of the carcinogenic effects of low doses of IQ and help to determine a margin of exposure that may be useful for practical human risk assessment.

Inflammation as a Cancer Co-Initiator: New Mechanistic Model Predicts Low/Negligible Risk at Noninflammatory Carcinogen Doses.

Linear-no-threshold (LNT) risk extrapolation has long been applied to estimate risks posed by low-level environmental carcinogen exposures, based on the 60-year-old multistage somatic mutation/clonal expansion (MSM) cancer theory. Recent evidence supports an alternative theory: Malignant tumors arise most efficiently from a stem cell that incurs requisite mutations and also is activated by inflammation to an epigenetically mediated and maintained state of adaptive hyperplasia (AH). This new inflammation-MSM (ISM) theory posits that inflammation-activated stem cells normally restricted to sites of injury-induced inflammation and tissue repair become uniquely susceptible to efficient carcinogenesis if normal post-inflammation AH termination is blocked by mutation. This theory posits that inflammation generally thus co-initiates cancer and transiently amplifies activated stem cells, implying that MSM theory (eg, the 2-stage stochastic “Moolgavkar, Venzon, Knudson [MVK]” model) is incomplete. Because inflammation dose–response typically is not LNT, the ISM theory predicts this is also true for most (perhaps all) carcinogens. The ISM (but not the MVK) model is shown to be consistent with recent data showing ∼100% carcinoma incidence (but not DNA adducts) in livers of rats exposed to aflatoxin B1 and was eliminated when that dose was co-administered with a highly potent anti-inflammatory agent. Experimental approaches to test ISM theory more robustly are discussed.

Dose-dependent spatiotemporal responses of mammalian cells to an alkylating agent.

Cultured cell populations are composed of heterogeneous cells, and previous single-cell lineage tracking analysis of individual HeLa cells provided empirical evidence for significant heterogeneity of the rate of cell proliferation and induction of cell death. Nevertheless, such cell lines have been used for investigations of cellular responses to various substances, resulting in incomplete characterizations. This problem caused by heterogeneity within cell lines could be overcome by investigating the spatiotemporal responses of individual cells to a substance. However, no approach to investigate the responses by analyzing spatiotemporal data is currently available. Thus, this study aimed to analyze the spatiotemporal responses of individual HeLa cells to cytotoxic, sub-cytotoxic, and non-cytotoxic doses of the well-characterized carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Although cytotoxic doses of MNNG are known to induce cell death, the single-cell tracking approach revealed that cell death occurred following at least four different cellular events, suggesting that cell death is induced via multiple processes. We also found that HeLa cells exposed to a sub-cytotoxic dose of MNNG were in a state of equilibrium between cell proliferation and cell death, with cell death again induced through different processes. However, exposure of cells to a non-cytotoxic dose of MNNG promoted growth by reducing the cell doubling time, thus promoting the growth of a sub-population of cells. A single-cell lineage tracking approach could dissect processes leading to cell death in a spatiotemporal manner and the results suggest that spatiotemporal data obtained by tracking individual cells can be used as a new type of bioinformatics data resource that enables the examination of cellular responses to various external substances.

Chemoprevention of Lung Carcinogenesis by Dietary Nicotinamide and Inhaled Budesonide.

Nicotinamide, the amide form of vitamin B3, and budesonide, a synthetic glucocorticoid used in the treatment of asthma, were evaluated to determine their individual and combinational chemopreventive efficacy on benzo(a)pyrene-induced lung tumors in female A/J mice. Nicotinamide fed at a dietary concentration of 0.75% significantly inhibited tumor multiplicity. Nicotinamide by aerosol inhalation at doses up to 15 mg/kg/day did not result in a statistically significant reduction in tumor multiplicity. Finally, dietary nicotinamide was administered with aerosol budesonide and tumor multiplicity reduced by 90% at 1 week and 49% at 8 weeks post last carcinogen dose. We conclude nicotinamide is an effective and safe agent for lung cancer dietary prevention at both early- and late-stage carcinogenesis and that efficacy is increased with aerosol budesonide. Combination chemoprevention with these agents is a well-tolerated and effective strategy which could be clinically advanced to human studies.

Differential response of T cells to an immunogen, a mitogen and a chemical carcinogen in a mouse model system.

In this study, we examined the relative immune response of T-lymphocytes and its intracellular cholesterol homeostasis, in a mouse model system, after treatment with immunogen, mitogen, and carcinogen. We studied the T-lymphocyte percentage, their LDL-receptor expression, along with the levels of serum interleukins (IL-2, IFNγ, IL-4, and IL-10) and intracellular cholesterol concentration (cytoplasmic and nuclear). The mitogen was found to be a better stimulator of T-cell marker expressions than the immunogen; though the immunogen was more effective on immunogenic response as was marked from interleukin levels. The chemical carcinogen benzo-α-pyrene at low concentration acted potentially like a mitogen but a reduced immune response was apparent at a carcinogenic dose. The findings in our study focus on the effect of carcinogenic dose of benzo-α-pyrene (BaP) on T-cell immunity. Benzo-α-pyrene causes immunosuppression through restriction of the T-cell population by targeting intracellular cholesterol.

Human health risk assessment from exposure of heavy metals in soil samples of Jammu district of Jammu and Kashmir, India

Contamination in soil can directly pose significant health risks through oral ingestion, particle inhalation, and dermal contact. Here, we studied the contamination level of heavy metals in soil samples to assess the carcinogenic and non-carcinogenic doses through multi-pathway exposures for health hazard point of view. The concentration of metals viz. zinc, iron, chromium, cadmium, copper, and manganese were measured in the collected soil samples of Jammu district, Jammu and Kashmir, India by using atomic absorption spectrometry (AAS). The average contents of the metals studied were as follows: Zn, 112 mg kg−1; Fe, 7403 mg kg−1; Cr, 92 mg kg−1; Cu, 37 mg kg−1; Cd, 0.4 mg kg−1; and Mn, 350 mg kg−1, respectively and metal decreased in the order Fe > Mn > Zn > Cr > Cu > Cd. The contamination factor, pollution load index, and index of geo-accumulation were also calculated to assess the quality of soil. Carcinogenic risk also has been calculated for Cr and Cd and carcinogenic doses for different exposure routes follow the order doses for ingestion (CDIing-ca) > > doses for inhalation (CDIinh-ca) > > doses for dermal absorption (CDIdermal-ca). Our results showed that the average values of Zn and Cd in the soil were within the acceptable limits, whereas the average values of Fe, Cr, Cu, and Mn in the soil samples were higher than the USEPA (1999) guidelines. The hazard index for both children and adults is less than unity, indicating no non-carcinogenic risk for both children and adults.

Beneficial effect of synbiotics on experimental colon cancer in rats.

The aim of this study was to investigate the influence of a synbiotic preparation (a mixture of six probiotics and a prebiotic) on aberrant crypt foci (ACF) formation, dysplasia, inflammation, and colitis-like lesions in experimental colon cancer in rats. Sixty male rats were categorized into three groups of 20 animals each. Group A was administered 1,2-dimethylydrazine, 15 mg/kg body weight (BW), once a week for 2 weeks. Group B was administered 1,2-dimethylydrazine at the same dose plus synbiotic, started after the second dose of carcinogen and lasted for 5 weeks. Group C was administered synbiotic plus carcinogen from the beginning of the experiment and lasted for 7 weeks. Animals were killed at the end of week 7. At the end of the experiment, the animals that received carcinogen plus the synbiotic had 100%, whereas the animals that received only carcinogen has 70% survival. Animals of groups B and C had significantly lower percentage of inflammation, colitis-like lesions, and ACF dysplasia than animals of group A, whereas those of group C had the least pathological lesions. Synbiotics seem to protect against the appearance of preneoplastic colon lesions in rats. The results of this experimental study suggest that treatment with a synbiotic preparation exerts significant antimutagenic properties against the development of preneoplastic lesions in rats.

RETRACTED ARTICLE: Computer electromagnetic radiation carcinogenic doses based on Monte Carlo algorithm

RETRACTED ARTICLE: Computer electromagnetic radiation carcinogenic doses based on Monte Carlo algorithm

Differential Response of B Cells to an Immunogen, a Mitogen and a Chemical Carcinogen in a Mouse Model System

Background:B cells are specific antibody generating cells which respond to foreign intruders in the circulation. The purpose of this study was to compare the relative immunogenic potentials of three well established agent types viz. an immunogen, a mitogen and a carcinogen, by following B cell responses to their presence in a mouse model system.Methods:Mice were treated with tetanus toxoid (immunogen), poke weed mitogen (typical mitogen), and benzo-α-pyrene (carcinogen) and generated B cell populations were determined in isolated splenic lymphocytes (splenocytes) by flow cytometry using specific anti-B cell marker antibodies. Flow cytometric estimation of LDL receptor (LDLR) expression, along with associated B cell markers, was also conducted. Kit based estimation of serum IgG, western blotting for LDLR estimation on total splenocytes and spectrometry for cholesterol and serum protein estimation were further undertaken. Student’s T-tests and one way ANOVA followed by the Bonferroni method were employed for statistical analysis.Results:The mitogen was found to better stimulate B cell marker expression than the immunogen, although the latter was more effective at inducing antibody production. The chemical carcinogen benzo-α-pyrene at low concentration acted potentially like a mitogen but almost zero immunity was apparent at a carcinogenic dose, with a low profile for LDLR expression and intracellular cholesterol.Conclusion:The findings in our study demonstrate an impact of concentration of BaP on generation of humoral immunity. Probably by immunosuppression through restriction of B-cell populations and associated antibodies, benzo-α-pyrene may exerts carcinogenicity. The level of cholesterol was found to be a pivotal target.

What is the meaning of 'A compound is carcinogenic'?

Chemical Carcinogens are compounds which can cause cancer in humans and experimental animals. This property is attributed to many chemicals in the public discussion, resulting in a widespread perception of danger and threat. In contrast, a scientific analysis of the wide and non-critical use of the term ‚carcinogenic’ is warranted. First, it has to be clarified if the compound acts in a genotoxic or non-genotoxic manner. In the latter case, an ineffective (safe) threshold dose without cancer risk can be assumed. In addition, it needs to be investigated if the mode-of-action causing tumors in laboratory animals is relevant at all for humans.In case the compound is clearly directly genotoxic, an ineffective threshold dose cannot be assumed. However, also in this case it is evident that high doses of the compound are generally associated with a high cancer risk, low doses with a lower one. Based on dose-response data from animal experiments, quantification of the cancer risk is carried out by mathematical modeling. If the safety margin between the lowest carcinogenic dose in animals and the relevant level of exposure in humans exceeds 10,000, the degree of concern is classified as low. Cases, where the compound turns out to be genotoxic in one study or one test only but not in others or only in vitro but not in vivo, are particularly difficult to explain and cause controversial discussions. Also for indirectly genotoxic agents, an ineffective (threshold) dose must be assumed. The situation is aggravated by the use of doubtful epidemiological studies in humans such as in the case of glyphosate, where data from mixed exposure to various chemicals were used. If such considerations are mixed with pure hazard classifications such as ‘probably carcinogenic in humans’ ignoring dose-response behavior and mode-of-action, the misinformation and public confusion are complete. It appears more urgent but also more difficult than ever to return to a scientifically based perception of these issues.

Identification of more than 100 structurally unique DNA-phosphate adducts formed during rat lung carcinogenesis by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a powerful lung carcinogen in animal models and is considered a causative factor for lung cancer in people who use tobacco products. NNK undergoes metabolic activation-a critical step in its mechanism of carcinogenesis-to an intermediate which reacts with DNA to form pyridyloxobutyl DNA base and phosphate adducts. Another important metabolic pathway of NNK is its conversion to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which similarly forms pyridylhydroxybutyl DNA base adducts that have been characterized previously. In this study, we investigated the potential formation of pyridylhydroxybutyl DNA phosphate adducts. We report the characterization and quantitation of 107 structurally unique pyridylhydroxybutyl DNA phosphate adducts in the lungs of rats treated chronically with a carcinogenic dose of 5 ppm of NNK in their drinking water for up to 70 weeks, by using a novel liquid chromatography-nanoelectrospray ionization-high-resolution tandem mass spectrometry method. Our findings demonstrate that pyridylhydroxybutyl phosphate adducts account for 38-55 and 34-40% of all the measured pyridine-containing DNA adducts in rat lung and liver, respectively, upon treatment with NNK. Some of the pyridylhydroxybutyl DNA phosphate adducts persisted in both tissues for over 70 weeks, suggesting that they could be potential biomarkers of chronic exposure to NNK and NNAL. This study provides comprehensive characterization and relative quantitation of a panel of NNK/NNAL-derived DNA phosphate adducts, thus identifying NNK as the source of the most structurally diverse set of DNA adducts identified to date from any carcinogen.

Abstract 5267: Chemoprevention of lung carcinogenesis by dietary nicotinamide and inhaled budesonide

Abstract Nicotinamide, the amide form of vitamin B3, and budesonide, a synthetic glucocorticoid used in the treatment of asthma, were evaluated for efficacy of chemoprevention of lung adenoma formation in a benzo(a)pyrene murine carcinogenesis model. Female A/J mice were given three doses of 3 mg benzo[a]pyrene three days apart and started on experimental diets either 1 week (early stage intervention) or 8 weeks (late stage) after last carcinogen dose. Aerosol treatments were delivered 5 days per week starting 1 or 8 weeks post carcinogen. Nicotinamide, fed at a dietary concentration of 0.75% starting 1 week after last carcinogen administration, inhibited adenoma formation by 54%, and by 39% when begun 8 weeks post final carcinogen. Nicotinamide fed at 0.25% of the diet was not found to effect adenoma formation . Dietary nicotinamide under the same conditions with budesonide administered via aerosol administration at 25μg/kg, reduced lung adenoma formation by 90% at early stage intervention and 49% at late stage intervention. Budesonide alone administered at the same dose level gave 77% inhibition at early stage and 41% inhibition at late stage. Decreases in adenoma formation were statistically significant via ANOVA analysis at both early and late interventions. Combination therapy decreased adenoma formation significantly over either individual therapy at the early stage and significantly compared to nicotinamide alone at the late stage. However, administration of nicotinamide by aerosol inhalation at doses up to 15 mg/kg/day did not result in a statistically significant reduction in tumor multiplicity at 1 or 8 weeks post last carcinogen administration . There is a high level of clinical interest in minimal toxicity lung cancer chemoprevention strategies. We feel administration of a safe dietary agent such as nicotinamide when combined with direct epithelial delivery of a glucocorticoid such as budesonide, commonly used for asthma therapy, is a promising approach for aerodigestive chemoprevention. Citation Format: Donna Seabloom, Beverly Wuertz, Art Galbraith, Jenny Antonides, Vernon Steele, Lee Wattenberg, Frank G. Ondrey. Chemoprevention of lung carcinogenesis by dietary nicotinamide and inhaled budesonide [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5267. doi:10.1158/1538-7445.AM2017-5267

Abstract B65: Alteration in cholesterol homeostasis and antibody synthesis in B cells an in-vivo effect of carcinogen (polyaromatic)

Abstract Introduction: Cholesterol, a major ingredient of cellular growth, is maintained in the cells by either intracellular biosynthesis or LDL receptor mediated endocytosis. Various studies have shown increased LDLR and SREBP2 (transcription factor) expressions as well as intracellular saturation of cholesterol in malignant and proliferating cells. Objectives: Citation of immune suppression is common in malignancy. B cells are antibody forming immune cells. Fate of Benzo-alpha-pyrene (mitogenic and carcinogenic doses) on B-cells has been aimed by exploring the role of cellular cholesterol homeostasis. Methods: Intraperitoneal injection of carcinogen, classical mitogen and immunogen to Swiss Albino mice in groups for optimally effective dose, B-cell (CD19 & CD79a) counts by flowcytometry, ELISA for IgG estimation, western blot for protein expressions and spectrophotometry for cholesterol estimation were among the parameters studied. Results: At immunosuppressive dose of Benzo-alphapyrene a significant decrease in serum IgG level, no significant change in number of B lymphocytes as compared with other agents, depressed expressions for LDLR / SREBP2 and significant decrease of cellular cholesterol (cytosolic and nuclear) were observed in mice model system. Conclusion: Benzo-alphapyrene leads to decrease in LDLR and SREBP2 expression resulting insufficient total intracellular cholesterol level and thus affects B-cell to proliferate. Immunosupression becomes apparent, which allows carcinogen to stay in the system and generation of tumor elsewhere. Citation Format: Nimisha Saxena, Sr., Amar Preet Kaur, Sr., Nimai Chand Chandra. Alteration in cholesterol homeostasis and antibody synthesis in B cells an in-vivo effect of carcinogen (polyaromatic). [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B65.

In vivo reporter gene mutation and micronucleus assays in gpt delta mice treated with a flame retardant decabromodiphenyl ether

Polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants, have been widely used as additive flame retardants. Recently, the use of brominated flame retardants has been restricted or prohibited under various legislative acts because of the persistence, bioaccumulation potential, and toxicity of these compounds. However, there are also additional concerns regarding environmental contamination and human exposure to PBDEs resulting from informal recycling technology. Decabromodiphenyl ether (decaBDE), one type of PBDE, has carcinogenic potential in the livers of rodents. Although one study has shown that decaBDE exerts genotoxic effects, the other in vitro and in vivo studies were negative for such effects. Thus, it remains unknown whether genotoxic mechanisms are involved in decaBDE-induced hepatocarcinogenesis in rodents. In this study, to explore the genotoxicity of decaBDE in mice, particularly in the context of carcinogenesis, we performed micronucleus assays in the bone marrow and reporter gene mutation assays in the liver using gpt delta mice treated with decaBDE at carcinogenic doses for 28days. Our results demonstrated negative results in micronucleus tests and reporter gene mutation assays. Thus, decaBDE did not exert genotoxic effects at carcinogenic target sites and did not show positive results in conventional in vivo genotoxicity tests in mice for 4-week treatment. Overall, comprehensive evaluation using in vivo genotoxicity data in rats and our data indicated that nongenotoxic mechanisms may be responsible for decaBDE-induced hepatocarcinogenesis.

Toxaphene-induced mouse liver tumorigenesis is mediated by the constitutive androstane receptor.

Toxaphene was shown to increase liver tumor incidence in B6C3F1 mice following chronic dietary exposure. Preliminary evidence supported a role for the constitutive androstane receptor (CAR) in the mode of action of toxaphene-induced mouse liver tumors. However, these results could not rule out a role for the pregnane X receptor (PXR) in liver tumor formation. To define further the nuclear receptors involved in this study, we utilized CAR, PXR and PXR/CAR knockout mice (CAR-/- , PXR-/- and PXR-/- /CAR-/- ) along with the wild-type C57BL/6. In this study CAR-responsive genes Cyp3a11 and Cyp2b10 were induced in the liver of C57BL/6 (wild-type) mice by toxaphene (30-570-fold) (at the carcinogenic dose 320 ppm) and phenobarbital (positive control) (16-420-fold) following 14 days' dietary treatment. In contrast, in CAR-/- mice, no induction of these genes was seen following treatment with either chemical. Cyp3a11 and Cyp2b10 were also induced in PXR-/- mice with toxaphene and phenobarbital but were not changed in treated PXR-/- /CAR-/- mice. Similarly, induction of liver pentoxyresorufin-O-deethylase (CAR activation) activity by toxaphene and phenobarbital was absent in CAR-/- and PXR-/- /CAR-/- mice treated with phenobarbital or toxaphene. Ethoxyresorufin-O-deethylase (EROD, represents aryl hydrocarbon receptor activation) activity in CAR-/- mice treated with toxaphene or phenobarbital was increased compared with untreated control, but lower overall in activity in comparison to the wild-type mouse. Liver EROD activity was also induced by both phenobarbital and toxaphene in the PXR-/- mice but not in the PXR-/- /CAR-/- mice. Toxaphene treatment increased 7-benzyloxyquinoline activity (a marker for PXR activation) in a similar pattern to that seen with pentoxyresorufin-O-deethylase. These observations indicate that EROD and PXR activation are evidence, as expected, of secondary overlap to primary CAR receptor activation. Together, these results definitively show that activation of the CAR nuclear receptor is the mode of action of toxaphene-induced mouse liver tumors. Copyright © 2017 John Wiley & Sons, Ltd.

Analysis of Carcinogenic Heavy Metals in Gallstones and its Role in Gallbladder Carcinogenesis.

Gallstone is a high-risk factor for gallbladder pre-malignancy or malignancy (GB PM-M) but which substances of gallstones definitely assist to turn out in to GB PM-M, remains unclear. This study aimed to find out the presence of carcinogenic heavy metals in gallstones and to explore the aetiopathogenesis of gallbladder pre-malignancy and malignancy. Presence of elements in gallstones was detected by energy dispersive X-ray spectroscopy (EDS) with scanning electron microscopy (SEM) and then level of carcinogenic heavy metals was estimated in gallstones using atomic absorption spectroscopy (AAS). The experiment was carried out in gallstone samples of 46 patients with gallbladder pre-malignant and malignant condition (PM-M group) and 65 sex and age-matched patients with chronic cholecystitis (C-C group). Gallstones were also classified in to three types such as cholesterol stone, mixed stone, and black pigment stone. EDS analysis detected presence of mercury, lead, and cobalt elements in all types of gallstones of both PM-M and C-C groups. AAS analysis revealed significantly higher amount of mercury (p<0.001), lead (p<0.0001), cobalt (p<0.01), and cadmium (p<0.01) in the gallstones of PM-M than C-C groups. The presence of these heavy metals also varied among stone types of both groups. EDS phase analysis showed 'dense deposits' of these metals in gallstones. Presence of significantly higher amount of mercury, lead, cobalt, and cadmium in gallstones may play a pivotal role as risk factors in the development of gallbladder malignancy or pre-malignancy. 'Dense deposits' of these metals in the gallstones which is the first observation, may act as crucial doses of carcinogens.

MiR-196b Is Epigenetically Silenced during the Premalignant Stage of Lung Carcinogenesis.

miRNA silencing by promoter hypermethylation may represent a mechanism by which lung cancer develops and progresses, but the miRNAs involved during malignant transformation are unknown. We previously established a model of premalignant lung cancer wherein we treated human bronchial epithelial cells (HBEC) with low doses of tobacco carcinogens. Here, we demonstrate that next-generation sequencing of carcinogen-transformed HBECs treated with the demethylating agent 5-aza-2'deoxycytidine revealed miR-196b and miR-34c-5p to be epigenetic targets. Bisulfite sequencing confirmed dense promoter hypermethylation indicative of silencing in multiple malignant cell lines and primary tumors. Chromatin immunoprecipitation studies further demonstrated an enrichment in repressive histone marks on the miR-196b promoter during HBEC transformation. Restoration of miR-196b expression by transfecting transformed HBECs with specific mimics led to cell-cycle arrest mediated in part through transcriptional regulation of the FOS oncogene, and miR-196b reexpression also significantly reduced the growth of tumor xenografts. Luciferase assays demonstrated that forced expression of miR-196b inhibited the FOS promoter and AP-1 reporter activity. Finally, a case-control study revealed that methylation of miR-196b in sputum was strongly associated with lung cancer (OR = 4.7, P < 0.001). Collectively, these studies highlight miR-196b as a tumor suppressor whose silencing early in lung carcinogenesis may provide a selective growth advantage to premalignant cells. Targeted delivery of miR-196b could therefore serve as a preventive or therapeutic strategy for the management of lung cancer. Cancer Res; 76(16); 4741-51. ©2016 AACR.

Tobacco-specific N-nitrosamines and polycyclic aromatic hydrocarbons in cigarettes smoked by the participants of the Shanghai Cohort Study.

Our recent studies on tobacco smoke carcinogen and toxicant biomarkers and cancer risk among male smokers in the Shanghai Cohort Study showed that exposure to tobacco-specific nitrosamines (TSNA) and polycyclic aromatic hydrocarbons (PAH) is prospectively associated with the risk of cancer. These findings support the hypothesis that the smokers' cancer risk is a function of the dose of select tobacco carcinogens and highlight the importance of understanding the factors that affect the intake of these carcinogens by smokers. Given that tobacco constituent exposures are driven, at least in part, by the levels of these constituents in cigarette smoke, we measured mainstream smoke TSNA and PAH levels in 43 Chinese cigarette brands that participants of the Shanghai Cohort Study reported to smoke. In all brands analyzed here, mainstream smoke levels of NNN and NNK, the two carcinogenic TSNA, were generally relatively low, averaging (±SD) 16.8(±25.1) and 14.2(±9.5) ng/cigarette, respectively. The levels of PAH were comparable to those found in U.S. cigarettes, averaging 15(±9) ng/cigarette for benzo[a]pyrene, 119(±66) ng/cigarette for phenanthrene and 37(±19) ng/cigarette for pyrene. Our findings indicate that the generally low levels of NNN and NNK are most likely responsible for the relatively low levels of the corresponding biomarkers in the urine of the Shanghai Cohort Study participants as compared to those found in the U.S. smokers, supporting the role of the levels of these constituents in cigarette smoke in smokers' exposures. Our findings also suggest that, in addition to smoking, other sources contribute to Chinese smokers' exposure to PAH.

Lack of genotoxic mechanisms in early-stage furan-induced hepatocellular tumorigenesis in gpt delta rats.

Furan has been used as an intermediate in the chemical-manufacturing industry and has been shown to contaminate various foods. Although furan induces hepatocellular tumors in rodents, equivocal results from in vitro and in vivo mutagenicity tests have caused controversy regarding the involvement of genotoxic mechanisms in furan-induced carcinogenesis. In the present study, to elucidate the possible mechanisms underlying furan-induced hepatocarcinogenesis, a comprehensive medium-term analysis was conducted using gpt delta rats treated with furan at carcinogenic doses for 13 weeks. In the liver, the frequencies of gpt and Spi- mutants derived mainly from point and deletion mutations, respectively, were not changed, and there were no furan-specific gpt mutations in furan-treated rats. In contrast, the number and area of glutathione S-transferase placental form (GST-P)- positive foci were significantly increased in the high-dose group. Also, the ratio of PCNA-positive hepatocytes was significantly elevated in the same group, as supported by significant increases in cyclin d1 and cyclin e1 mRNA levels. Thus, it is highly probable that cell proliferation, but not genotoxic mechanisms, contribute to the development of GST-P foci in furan-treated rats. Based on the close relationship between GST-P and neoplastic hepatocytes, these data allowed us to hypothesize that cell proliferation following signal transduction other than the mitogen-activated protein kinase (MAPK)/ERK pathway may play a crucial role in early-stage furan-induced hepatocarcinogenesis. Copyright © 2016 John Wiley & Sons, Ltd.

Postmenopausal Breast Cancer Risk in Relation to Antibodies Specific to Benzo[a]Pyrene, Estradiol and Progesterone.

BackgroundAntibodies might protect against low doses of environmental carcinogens by decreasing systemic uptake, activation of metabolic pathways, and redistribution of carcinogens within the organism. The features of antibody formation in relation to environmental carcinogens and sex steroids under natural conditions should be determined to identify breast cancer risk, then to develop cancer immune prevention strategies.ObjectivesThe purpose of this study was to investigate antibodies specifications to benzo(a)pyrene, estradiol and progesterone in postmenopausal women with invasive breast cancer.Patients and MethodsA semi-quantitative non-competitive immunoassay of IgG antibodies to benzo(a)pyrene (IgG-Bp), estradiol (IgG-Es), and progesterone (IgG-Pg) has conducted. The assay has performed on 322 serum samples from patients with breast cancer and 179 serum samples from healthy postmenopausal women by using low-molecular-weight Bp, Es, and Pg conjugated with bovine serum albumin. ROC analysis has also conducted to determine the odds ratio (OR).ResultsCombination of the high levels of IgG-Bp and IgG-Es without IpG-Pg was more frequent in breast cancer patients than that in healthy women, and the OR has increased to 3.8. Combination of the high levels of IgG-Pg with high levels of both IgG-Bp and IgG-Es were significantly more frequent in breast cancer patients (36.9%) than that in healthy women (5.6%), and the OR increased to 11.7. These differences have peculiarly expressed in breast cancer patients with hormone status ER+/PR- (OR = 26.7). The minimum OR (0.4) has obtained at low levels of the three antibodies.ConclusionsImmunoassay of antibodies against environmental carcinogens and sex steroid hormones could use to detect breast cancer risk. Induction of antibodies against Bp for cancer immunoprevention could lead to antibody formation against steroid hormones, thereby increasing breast cancer risk.