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Jaruga P, Tomar R, Kant M, Vartanian V, Sexton B, Rizzo CJ, Turesky RJ, Stone MP, Lloyd RS, Dizdaroglu M. Synthesis and Characterization of 15N 5-Labeled Aflatoxin B 1-Formamidopyrimidines and Aflatoxin B 1-N7-Guanine from a Partial Double-Stranded Oligodeoxynucleotide as Internal Standards for Mass Spectrometric Measurements. ACS OMEGA 2023; 8:14841-14854. [PMID: 37125130 PMCID: PMC10134230 DOI: 10.1021/acsomega.3c01328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 03/20/2023] [Indexed: 05/03/2023]
Abstract
Aflatoxin B1 (AFB1) exposure through contaminated food is a primary contributor to hepatocellular carcinogenesis worldwide. Hepatitis B viral infections in livers dramatically increase the carcinogenic potency of AFB1 exposures. Liver cytochrome P450 oxidizes AFB1 to the epoxide, which in turn reacts with N7-guanine in DNA, producing the cationic trans-8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 adduct (AFB1-N7-Gua). The opening of the imidazole ring of AFB1-N7-Gua under physiological conditions causes the formation of the cis- and trans-diastereomers of 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1 (AFB1-FapyGua). These adducts primarily lead to G → T mutations, with AFB1-FapyGua being significantly more mutagenic than AFB1-N7-Gua. The unequivocal identification and accurate quantification of these AFB1-Gua adducts as biomarkers are essential for a fundamental understanding and prevention of AFB1-induced hepatocellular carcinogenesis. Among a variety of analytical techniques used for this purpose, liquid chromatography-tandem mass spectrometry, with the use of the stable isotope-labeled analogues of AFB1-FapyGua and AFB1-N7-Gua as internal standards, provides the greatest accuracy and sensitivity. cis-AFB1-FapyGua-15N5, trans-AFB1-FapyGua-15N5, and AFB1-N7-Gua-15N5 have been synthesized and used successfully as internal standards. However, the availability of these standards from either academic institutions or commercial sources ceased to exist. Thus, quantitative genomic data regarding AFB1-induced DNA damage in animal models and humans remain challenging to obtain. Previously, AFB1-N7-Gua-15N5 was prepared by reacting AFB1-exo-8,9-epoxide with the uniformly 15N5-labeled DNA isolated from algae grown in a pure 15N-environment, followed by alkali treatment, resulting in the conversion of AFB1-N7-Gua-15N5 to AFB1-FapyGua-15N5. In the present work, we used a different and simpler approach to synthesize cis-AFB1-FapyGua-15N5, trans-AFB1-FapyGua-15N5, and AFB1-N7-Gua-15N5 from a partial double-stranded 11-mer Gua-15N5-labeled oligodeoxynucleotide, followed by isolation and purification. We also show the validation of these 15N5-labeled standards for the measurement of cis-AFB1-FapyGua, trans-AFB1-FapyGua, and AFB1-N7-Gua in DNA of livers of AFB1-treated mice.
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Affiliation(s)
- Pawel Jaruga
- Biomolecular
Measurement Division, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Rachana Tomar
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Melis Kant
- Biomolecular
Measurement Division, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Vladimir Vartanian
- Oregon
Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Benjamin Sexton
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Carmelo J. Rizzo
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Robert J. Turesky
- Masonic
Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Michael P. Stone
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - R. Stephen Lloyd
- Oregon
Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Miral Dizdaroglu
- Biomolecular
Measurement Division, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899, United States
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Kang L, Guo N, Liu X, Wang X, Guo W, Xie SM, Liu C, Lv P, Xing L, Zhang X, Shen H. High mobility group box-1 protects against Aflatoxin G 1-induced pulmonary epithelial cell damage in the lung inflammatory environment. Toxicol Lett 2020; 331:92-101. [PMID: 32446815 DOI: 10.1016/j.toxlet.2020.05.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Revised: 05/08/2020] [Accepted: 05/11/2020] [Indexed: 12/20/2022]
Abstract
Aflatoxin G1 (AFG1) is a member of the carcinogenic aflatoxin family. Our previous studies indicated that oral administration of AFG1 caused tumor necrosis factor (TNF)-α-dependent inflammation that enhanced oxidative DNA damage in alveolar epithelial cells, which may be related to AFG1-induced lung carcinogenesis. High mobility group box-1 (HMGB1) is a nuclear DNA-binding protein; the intracellular and extracellular roles of HMGB1 have been shown to contribute to DNA repair and sterile inflammation. The role of HMGB1 in DNA damage in an aflatoxin-induced lung inflammatory environment was investigated in this study. Upregulation of HMGB1, TLR2, and RAGE was observed in AFG1-induced lung inflamed tissues and adenocarcinoma. Blocking AFG1-induced inflammation by neutralization of TNF-α inhibited the upregulation of HMGB1 in mouse lung tissues, suggesting that AFG1-induced TNF-α-dependent inflammation regulated HMGB1 expression. In the in vitro human pulmonary epithelial cell line model, Beas-2b, AFG1 directly enhanced the cytosolic translocation of HMGB1 and its extracellular secretion. The addition of extracellular soluble HMGB1 protected AFG1-induced DNA damage through the TLR2/NF-κB pathway in Beas-2b cells. In addition, blockade of endogenous HMGB1 by siRNA significantly enhanced AFG1-induced damage. Thus, our findings showed that both extracellularly-released and nuclear and cytosolic HMGB1 could protect the cell from AFG1-induced cell damage in a TNF-α-dependent lung inflammatory environment.
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Affiliation(s)
- Lifei Kang
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China; Department of Pathology, Hebei Chest Hospital, Shijiazhuang, China
| | - Ningfei Guo
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Xiaoyi Liu
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Xiuqing Wang
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Wenli Guo
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Shelly M Xie
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Chunping Liu
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Ping Lv
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Lingxiao Xing
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Xianghong Zhang
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China; Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.
| | - Haitao Shen
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
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3
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Adhikari A, Jacob NK, Hansen AR, Wei Y, Snook K, Liu F, Zhang J. Pet ownership and the risk of dying from lung cancer, findings from an 18 year follow-up of a US national cohort. ENVIRONMENTAL RESEARCH 2019; 173:379-386. [PMID: 30954911 DOI: 10.1016/j.envres.2019.01.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/16/2019] [Accepted: 01/19/2019] [Indexed: 06/09/2023]
Abstract
PURPOSE In contrast to the popularity of pets, research on the health effects of living with pets, particularly, on the risk of cancer, is minimal and inconclusive. We longitudinally examined relationships between pet ownership and the risk of dying from lung cancer. METHODS We analyzed nationally representative data of 13,725 adults aged ≥ 19 who answered the question about pet ownership in the Third National Health and Nutrition Examination Survey, 1988-1994, as the baseline survey. Vital status was followed through December 31st, 2010. RESULTS About 43% of the study population owned pets, with 20.4% having cats and 4.6% having birds. A total of 213 lung cancer deaths were recorded by the end of 183,094 unweighted person-years of follow-up with a lung-cancer specific death rate of 1.00 per 1000 person-years. After adjustment for cigarette smoking, alcohol drinking, physical activity, body mass index, history of atopic conditions, and serum cotinine, owning a pet (any) was associated with a doubled mortality rate among women for lung cancer [hazard ratio (HR)= 2.31 (1.41-3.79)] over non-owners. This association was largely attributed to having a cat or a bird. The HR was 2.85 (1.62-5.01) for cats, and 2.67 (0.68-10.5) for birds. The HR for dogs was 1.01 (0.57-1.77). No significant patterns of association were observed among men either for any pets or for a subtype of pet. CONCLUSIONS Living with a pet, especially, a cat or a bird, was significantly associated with elevated hazard of dying from lung cancer among women. The detrimental effect that pets conferred was not explained by confounding from cigarette smoking or atopic conditions.
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Affiliation(s)
- Atin Adhikari
- Department of Environmental Health Sciences, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, GA, USA
| | - Naduparambil K Jacob
- Department of Radiation Oncology, Ohio State University Comprehensive Cancer Center, Columbus, OH, USA
| | - Andrew R Hansen
- Department of Community Health, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, GA, USA
| | - Yudan Wei
- Department of Community Medicine, Mercer University School of Medicine, Macon, GA 31027, USA
| | - Kassandra Snook
- Department of Epidemiology, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, GA, USA
| | - Fengqi Liu
- Charlie Norwood VA Medical Center, Augusta, GA, USA
| | - Jian Zhang
- Department of Epidemiology, Jiann-Ping Hsu College of Public Health, Georgia Southern University, Statesboro, GA, USA.
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4
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Abstract
The three RAS genes - HRAS, NRAS and KRAS - are collectively mutated in one-third of human cancers, where they act as prototypic oncogenes. Interestingly, there are rather distinct patterns to RAS mutations; the isoform mutated as well as the position and type of substitution vary between different cancers. As RAS genes are among the earliest, if not the first, genes mutated in a variety of cancers, understanding how these mutation patterns arise could inform on not only how cancer begins but also the factors influencing this event, which has implications for cancer prevention. To this end, we suggest that there is a narrow window or 'sweet spot' by which oncogenic RAS signalling can promote tumour initiation in normal cells. As a consequence, RAS mutation patterns in each normal cell are a product of the specific RAS isoform mutated, as well as the position of the mutation and type of substitution to achieve an ideal level of signalling.
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Affiliation(s)
- Siqi Li
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
| | - Allan Balmain
- Helen Diller Family Comprehensive Cancer Center and Department of Biochemistry and Biophysics, University of California, San Francisco, CA, USA
| | - Christopher M Counter
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
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5
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Calabrese EJ. The additive to background assumption in cancer risk assessment: A reappraisal. ENVIRONMENTAL RESEARCH 2018; 166:175-204. [PMID: 29890424 DOI: 10.1016/j.envres.2018.05.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/08/2018] [Accepted: 05/11/2018] [Indexed: 05/21/2023]
Abstract
The assumption that chemical and radiation induced cancers act in a manner that is additive to background was proposed in the mid-1970s. It was adopted by the U.S. Environmental Protection Agency (EPA) in 1986 and then subsequently by other regulatory agencies worldwide for cancer risk assessment. It ensured that cancer risks at low doses act in a linear fashion. The additive to background process assumes that the mechanism(s) resulting in induced (i.e., treatment related) and spontaneous (i.e., control group) cancers are identical. This assumption could not be properly evaluated due to inadequate mechanistic data when it was proposed in the 1970s. Using the findings of modern molecular toxicology, including oncogene activation/mutation, gene regulation, and molecular pathway analyses, the additive to background assumption was evaluated in the present paper. Based on published studies with 45 carcinogens over 13 diverse mammalian models and for a broad range of tumor types compelling evidence indicates that carcinogen-induced tumors are mediated in general via mechanisms that are not identical to those affecting the occurrence of the same type of spontaneous tumors in appropriate control groups. These findings, which challenge a fundamental assumption of the additive to background concept, have significant implications for cancer risk assessment policy, regulatory agency practices, as well as fundamental concepts of cancer biology.
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Affiliation(s)
- Edward J Calabrese
- Department of Environmental Health Sciences, University of Massachusetts, Morrill I, N344, Amherst, MA 01003, United States.
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6
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Yi L, Shen H, Zhao M, Shao P, Liu C, Cui J, Wang J, Wang C, Guo N, Kang L, Lv P, Xing L, Zhang X. Inflammation-mediated SOD-2 upregulation contributes to epithelial-mesenchymal transition and migration of tumor cells in aflatoxin G 1-induced lung adenocarcinoma. Sci Rep 2017; 7:7953. [PMID: 28801561 PMCID: PMC5554181 DOI: 10.1038/s41598-017-08537-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 07/11/2017] [Indexed: 11/09/2022] Open
Abstract
Tumor-associated inflammation plays a critical role in facilitating tumor growth, invasion and metastasis. Our previous study showed Aflatoxin G1 (AFG1) could induce lung adenocarcinoma in mice. Chronic lung inflammation associated with superoxide dismutase (SOD)-2 upregulation was found in the lung carcinogenesis. However, it is unclear whether tumor-associated inflammation mediates SOD-2 to contribute to cell invasion in AFG1-induced lung adenocarcinoma. Here, we found increased SOD-2 expression associated with vimentin, α-SMA, Twist1, and MMP upregulation in AFG1-induced lung adenocarcinoma. Tumor-associated inflammatory microenvironment was also elicited, which may be related to SOD-2 upregulation and EMT in cancer cells. To mimic an AFG1-induced tumor-associated inflammatory microenvironment in vitro, we treated A549 cells and human macrophage THP-1 (MΦ-THP-1) cells with AFG1, TNF-α and/or IL-6 respectively. We found AFG1 did not promote SOD-2 expression and EMT in cancer cells, but enhanced TNF-α and SOD-2 expression in MΦ-THP-1 cells. Furthermore, TNF-α could upregulate SOD-2 expression in A549 cells through NF-κB pathway. Blocking of SOD-2 by siRNA partly inhibited TNF-α-mediated E-cadherin and vimentin alteration, and reversed EMT and cell migration in A549 cells. Thus, we suggest that tumor-associated inflammation mediates SOD-2 upregulation through NF-κB pathway, which may contribute to EMT and cell migration in AFG1-induced lung adenocarcinoma. INTRODUCTION
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Affiliation(s)
- Li Yi
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.,Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Haitao Shen
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China
| | - Mei Zhao
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Peilu Shao
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.,Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Chunping Liu
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China.,Department of Dermatology,The Third Hospital, Hebei Medical University, Shijiazhuang, China
| | - Jinfeng Cui
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.,Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Juan Wang
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.,Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Can Wang
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.,Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Ningfei Guo
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Lifei Kang
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Ping Lv
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Lingxiao Xing
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Xianghong Zhang
- Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China. .,Lab of Pathology, Hebei Medical University, Shijiazhuang, China.
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7
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Hong HHL, Hoenerhoff MJ, Ton TV, Herbert RA, Kissling GE, Hooth MJ, Behl M, Witt KL, Smith-Roe SL, Sills RC, Pandiri AR. Kras, Egfr, and Tp53 Mutations in B6C3F1/N Mouse and F344/NTac Rat Alveolar/Bronchiolar Carcinomas Resulting from Chronic Inhalation Exposure to Cobalt Metal. Toxicol Pathol 2015; 43:872-82. [PMID: 26059825 DOI: 10.1177/0192623315581192] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Rodent lung tumors are morphologically similar to a subtype of human lung adenocarcinomas. The objective of this study was to evaluate Kirsten rat sarcoma oncogene homolog (Kras), epidermal growth factor receptor (Egfr), and tumor protein 53 (Tp53) mutations, which are relevant to human lung cancer, in cobalt metal dust (CMD)-induced alveolar/bronchiolar tumors of B6C3F1/N mice and F344/NTac rats. Kras mutations were detected in 67% (mice) and 31% (rats) of CMD-induced lung tumors and were predominantly exon 1 codon 12 G to T transversions (80% in mice and 57% in rats). Egfr mutations were detected in 17% (both mice and rats) of CMD-induced lung tumors and were predominantly in exon 20 with 50% G to A transitions (mice and rats). Tp53 mutations were detected in 19% (mice) and 23% (rats) of CMD-induced lung tumors and were predominant in exon 5 (mice, 69% transversions) and exon 6 (rats, all transitions). No mutations were observed for these genes in spontaneous lung tumors or normal lungs from untreated controls. Ames assay indicated that CMD is mutagenic in the absence but not in the presence of S9 mix. Thus, the mutation data (G to T transversions) and Ames assay results suggest that oxidative damage to DNA may be a contributing factor in CMD-induced pulmonary carcinogenesis in rodents.
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Affiliation(s)
- Hue-Hua L Hong
- Cellular and Molecular Pathology Branch, Division of the National Toxicology Program (NTP), National Institute of Environmental Health Science (NIEHS), Research Triangle Park, North Carolina, USA
| | - Mark J Hoenerhoff
- Cellular and Molecular Pathology Branch, Division of the National Toxicology Program (NTP), National Institute of Environmental Health Science (NIEHS), Research Triangle Park, North Carolina, USA Current address: University of Michigan, Ann Arbor, Michigan, USA
| | - Thai-Vu Ton
- Cellular and Molecular Pathology Branch, Division of the National Toxicology Program (NTP), National Institute of Environmental Health Science (NIEHS), Research Triangle Park, North Carolina, USA
| | - Ronald A Herbert
- Cellular and Molecular Pathology Branch, Division of the National Toxicology Program (NTP), National Institute of Environmental Health Science (NIEHS), Research Triangle Park, North Carolina, USA
| | - Grace E Kissling
- Biostatistics Branch, NTP, NIEHS, Research Triangle Park, North Carolina, USA
| | - Michelle J Hooth
- Program Operations Branch, DNTP, NIEHS, Research Triangle Park, North Carolina, USA
| | - Mamta Behl
- Toxicology Branch, NTP, NIEHS, Research Triangle Park, North Carolina, USA
| | - Kristine L Witt
- Biomolecular Screening Branch, NTP, NIEHS, Research Triangle Park, North Carolina, USA
| | - Stephanie L Smith-Roe
- Biomolecular Screening Branch, NTP, NIEHS, Research Triangle Park, North Carolina, USA
| | - Robert C Sills
- Cellular and Molecular Pathology Branch, Division of the National Toxicology Program (NTP), National Institute of Environmental Health Science (NIEHS), Research Triangle Park, North Carolina, USA
| | - Arun R Pandiri
- Cellular and Molecular Pathology Branch, Division of the National Toxicology Program (NTP), National Institute of Environmental Health Science (NIEHS), Research Triangle Park, North Carolina, USA Experimental Pathology Laboratories, Inc., Durham, North Carolina, USA
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8
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Mo X, Lai H, Yang Y, Xiao J, He K, Liu C, Chen J, Lin Y. How does airway exposure of aflatoxin B1 affect serum albumin adduct concentrations? Evidence based on epidemiological study and animal experimentation. J Toxicol Sci 2015; 39:645-53. [PMID: 25056789 DOI: 10.2131/jts.39.645] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Aflatoxin B1 (AFB1) airway inhalation represents an additional route of exposure to this toxin. However, the association between AFB1 inhalation and serum AFB1 albumin adducts remains unclear. The aim of this study was to explore the association between airway exposure to AFB1 and serum AFB1 albumin adduct concentrations via an epidemiological study, as well as in an AFB1 airway exposure animal model. Our epidemiological study was conducted in a sugar factory in the Guangxi Autonomous Region of China. In order to examine fungal contamination, air samples were obtained in the workshop and areas outside the workshop, such as the office and nearby store. Dust samples were also collected from the bagasse warehouse and presser workshop, and were analyzed using an indirect competitive enzyme-linked immunosorbent assay (ELISA). Additionally, blood samples were collected from a total of 121 workshop workers, and a control group (n = 80) was comprised of workers who undertook administrative tasks or other work outside the workshop. The animal experiment was conducted in the laboratory animal center of Guangxi Medical University, where a total of 60 adult male rabbits were involved in this study. By intubation, AFB1 was administered in three groups of rabbits daily, at dose rates of 0.075, 0.05 and 0.025 mg/kg/day for a period of 7 days. Blood samples were collected on day 1, day 3, day 7 and day 21, and the measurements of the AFB1 albumin adducts in the serum were performed by a double antibody sandwich ELISA. The epidemiological study showed that serum albumin adducts were detected in 67 workshop workers (55.37%), and the values ranged 6.4 pg/mg albumin to 212 pg/mg albumin (mean value: 51 ± 4.62 pg/mg albumin). In contrast, serum albumin adducts were detected in only 7 control group participants, with the values ranging from 9 pg AFB1/mg albumin to 59 pg/mg albumin (mean value: 20 ± 13.72 pg/mg albumin). The animal experiment revealed that the rabbits had detectable levels of AFB1 in their serum with a minimum effective dose of 0.05 mg/kg/day; while 11 of 17 (64.71%) rabbits had detectable levels of AFB1 albumin adducts in the high exposure group (0.075 mg/kg/day), and only 5 rabbits (26.32%) had detectable levels of AFB1 albumin adducts in the moderate exposure group (0.05 mg/kg/day). No rabbits had detectable levels of AFB1 albumin adducts in the low exposure group (0.025 mg/kg/day). Our results demonstrated that only exposure to a certain level of AFB1 would result in detectable levels of serum AFB1 albumin adducts. Interventional programs aimed at reducing exposure to AFB1 by inhalation are urgently needed in high-risk populations. Additional large-sample, well-designed randomized controlled trials are needed to further confirm our results.
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Affiliation(s)
- Xianwei Mo
- Department of Gastrointestinal Surgery, Affiliated Cancer Hospital of Guangxi Medical University
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9
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Hrycay EG, Bandiera SM. Involvement of Cytochrome P450 in Reactive Oxygen Species Formation and Cancer. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 74:35-84. [PMID: 26233903 DOI: 10.1016/bs.apha.2015.03.003] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review examines the involvement of cytochrome P450 (CYP) enzymes in the formation of reactive oxygen species in biological systems and discusses the possible involvement of reactive oxygen species and CYP enzymes in cancer. Reactive oxygen species are formed in biological systems as byproducts of the reduction of molecular oxygen and include the superoxide radical anion (∙O2-), hydrogen peroxide (H2O2), hydroxyl radical (∙OH), hydroperoxyl radical (HOO∙), singlet oxygen ((1)O2), and peroxyl radical (ROO∙). Two endogenous sources of reactive oxygen species are the mammalian CYP-dependent microsomal electron transport system and the mitochondrial electron transport chain. CYP enzymes catalyze the oxygenation of an organic substrate and the simultaneous reduction of molecular oxygen. If the transfer of oxygen to a substrate is not tightly controlled, uncoupling occurs and leads to the formation of reactive oxygen species. Reactive oxygen species are capable of causing oxidative damage to cellular membranes and macromolecules that can lead to the development of human diseases such as cancer. In normal cells, intracellular levels of reactive oxygen species are maintained in balance with intracellular biochemical antioxidants to prevent cellular damage. Oxidative stress occurs when this critical balance is disrupted. Topics covered in this review include the role of reactive oxygen species in intracellular cell signaling and the relationship between CYP enzymes and cancer. Outlines of CYP expression in neoplastic tissues, CYP enzyme polymorphism and cancer risk, CYP enzymes in cancer therapy and the metabolic activation of chemical procarcinogens by CYP enzymes are also provided.
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Affiliation(s)
- Eugene G Hrycay
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.
| | - Stelvio M Bandiera
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia, Canada
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10
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Mulder JE, Turner PV, Massey TE. Effect of 8-oxoguanine glycosylase deficiency on aflatoxin B1 tumourigenicity in mice. Mutagenesis 2015; 30:401-9. [PMID: 25583175 DOI: 10.1093/mutage/geu087] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The mycotoxin aflatoxin B1 (AFB1) may initiate cancer by causing oxidatively damaged DNA, specifically by causing 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) lesions. Base excision repair removes these lesions, with 8-oxoguanine glycosylase (OGG1) being the rate-limiting enzyme. The aim of this study was to determine the effect of ogg1 deficiency on AFB1-induced oxidatively damaged DNA and tumourigenesis. Female wild-type, heterozygous and homozygous ogg1 null mice were given a single dose of 50mg/kg AFB1 or 40 µl dimethyl sulfoxide (DMSO) ip. Neither ogg1 genotype nor AFB1 treatment affected levels of oxidised guanine in lung or liver 2h post-treatment. AFB1-treated ogg1 null mice showed exacerbated weight loss and mortality relative to DMSO-treated ogg1 null mice, but AFB1 treatment did not significantly increase lung or liver tumour incidence compared with controls, regardless of ogg1 genotype. Suspect lung masses from three of the AFB1-treated mice were adenomas, and masses from two of the mice were osteosarcomas. No osteosarcomas were observed in DMSO-treated mice. All liver masses from AFB1-treated mice were adenomas, and one also contained a hepatocellular carcinoma. In DNA from the lung tumours, the K-ras mutation pattern was inconsistent with initiation by AFB1. In conclusion, ogg1 status did not have a significant effect on AFB1-induced oxidatively damaged DNA or tumourigenesis, but deletion of one or both alleles of ogg1 did increase susceptibility to other aspects of AFB1 toxicity.
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Affiliation(s)
- Jeanne E Mulder
- Department of Biomedical and Molecular Sciences, Pharmacology and Toxicology Graduate Program, Queen's University, Rm 556, Botterell Hall, Kingston, Ontario K7L 3N6, Canada, Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Patricia V Turner
- Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Thomas E Massey
- Department of Biomedical and Molecular Sciences, Pharmacology and Toxicology Graduate Program, Queen's University, Rm 556, Botterell Hall, Kingston, Ontario K7L 3N6, Canada, Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Liu C, Shen H, Yi L, Shao P, Soulika AM, Meng X, Xing L, Yan X, Zhang X. Oral administration of aflatoxin G₁ induces chronic alveolar inflammation associated with lung tumorigenesis. Toxicol Lett 2014; 232:547-56. [PMID: 25445582 DOI: 10.1016/j.toxlet.2014.11.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 10/26/2014] [Accepted: 11/02/2014] [Indexed: 01/05/2023]
Abstract
Our previous studies showed oral gavage of aflatoxin G₁ (AFG₁) induced lung adenocarcinoma in NIH mice. We recently found that a single intratracheal administration of AFG₁ caused chronic inflammatory changes in rat alveolar septum. Here, we examine whether oral gavage of AFG₁ induces chronic lung inflammation and how it contributes to carcinogenesis. We evaluated chronic lung inflammatory responses in Balb/c mice after oral gavage of AFG₁ for 1, 3 and 6 months. Inflammatory responses were heightened in the lung alveolar septum, 3 and 6 months after AFG₁ treatment, evidenced by increased macrophages and lymphocytes infiltration, up-regulation of NF-κB and p-STAT3, and cytokines production. High expression levels of superoxide dismutase (SOD-2) and hemoxygenase-1 (HO-1), two established markers of oxidative stress, were detected in alveolar epithelium of AFG₁-treated mice. Promoted alveolar type II cell (AT-II) proliferation in alveolar epithelium and angiogenesis, as well as increased COX-2 expression were also observed in lung tissues of AFG₁-treated mice. Furthermore, we prolonged survival of the mice in the above model for another 6 months to examine the contribution of AFG₁-induced chronic inflammation to lung tumorigenesis. Twelve months later, we observed that AFG₁ induced alveolar epithelial hyperplasia and adenocarcinoma in Balb/c mice. Up-regulation of NF-κB, p-STAT3, and COX-2 was also induced in lung adenocarcinoma, thus establishing a link between AFG₁-induced chronic inflammation and lung tumorigenesis. This is the first study to show that oral administration of AFG₁ could induce chronic lung inflammation, which may provide a pro-tumor microenvironment to contribute to lung tumorigenesis.
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Affiliation(s)
- Chunping Liu
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China; Department of Dermatology, The Third Hospital, Hebei Medical University, Shijiazhuang, China
| | - Haitao Shen
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Li Yi
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Peilu Shao
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Athena M Soulika
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, CA, USA
| | - Xinxing Meng
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Lingxiao Xing
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Xia Yan
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Xianghong Zhang
- Lab of Pathology, Hebei Medical University, Shijiazhuang, China; Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.
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12
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Viegas S, Veiga L, Figueiredo P, Almeida A, Carolino E, Viegas C. Assessment of workers' exposure to aflatoxin B1 in a Portuguese waste industry. ACTA ACUST UNITED AC 2014; 59:173-81. [PMID: 25324565 DOI: 10.1093/annhyg/meu082] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Aflatoxin B1 (AFB1) is considered by different International Agencies as a genotoxic and potent hepatocarcinogen. However, despite the fact that the fungi producing this compound are detected in some work environments, AFB1 is rarely monitored in occupational settings. The aim of the present investigation was to assess exposure to AFB1 of workers from one Portuguese waste company located in the outskirt of Lisbon. Occupational exposure assessment to AFB1 was done with a biomarker of internal dose that measures AFB1 in the serum by enzyme-linked immunosorbent assay. Forty-one workers from the waste company were enrolled in this study (26 from sorting; 9 from composting; 6 from incineration). A control group (n = 30) was also considered in order to know the AFB1 background levels for the Portuguese population. All the workers showed detectable levels of AFB1 with values ranging from 2.5ng ml(-1) to 25.9ng ml(-1) with a median value of 9.9±5.4ng ml(-1). All of the controls showed values below the method's detection limit. Results obtained showed much higher (8-fold higher) values when compared with other Portuguese settings already studied, such as poultry and swine production. Besides this mycotoxin, other mycotoxins are probably present in this occupational setting and this aspect should be taken into consideration for the risk assessment process due to possible synergistic reactions. The data obtained suggests that exposure to AFB1 occurs in a waste management setting and claims attention for the need of appliance of preventive and protective safety measures.
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Affiliation(s)
- Susana Viegas
- 1.Environment and Health RG, Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Av. D. João II, lote 4.69.01, Parque das Nações, 1990-096 Lisbon, Portugal 2.Center for Malaria & Tropical Diseases (CMDT), Public Health and Policy, Escola Nacional de Saúde Pública, Universidade Nova de Lisboa, Avenida Padre Cruz, 1600-560 Lisboa, Portugal
| | - Luisa Veiga
- 3.Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Lisbon, Portugal
| | - Paula Figueiredo
- 3.Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Lisbon, Portugal
| | - Ana Almeida
- 3.Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Lisbon, Portugal
| | - Elisabete Carolino
- 1.Environment and Health RG, Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Av. D. João II, lote 4.69.01, Parque das Nações, 1990-096 Lisbon, Portugal
| | - Carla Viegas
- 1.Environment and Health RG, Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Av. D. João II, lote 4.69.01, Parque das Nações, 1990-096 Lisbon, Portugal
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13
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Guindon-Kezis KA, Mulder JE, Massey TE. In vivo treatment with aflatoxin B1 increases DNA oxidation, base excision repair activity and 8-oxoguanine DNA glycosylase 1 levels in mouse lung. Toxicology 2014; 321:21-6. [DOI: 10.1016/j.tox.2014.03.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 02/03/2014] [Accepted: 03/16/2014] [Indexed: 11/24/2022]
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Shen H, Liu J, Wang Y, Lian H, Wang J, Xing L, Yan X, Wang J, Zhang X. Aflatoxin G1-induced oxidative stress causes DNA damage and triggers apoptosis through MAPK signaling pathway in A549 cells. Food Chem Toxicol 2013; 62:661-9. [DOI: 10.1016/j.fct.2013.09.030] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 08/30/2013] [Accepted: 09/24/2013] [Indexed: 11/16/2022]
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Bahari A, Mehrzad J, Mahmoudi M, Bassami MR, Dehghani H. Cytochrome P450 isoforms are differently up-regulated in aflatoxin B₁-exposed human lymphocytes and monocytes. Immunopharmacol Immunotoxicol 2013; 36:1-10. [PMID: 24168324 DOI: 10.3109/08923973.2013.850506] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
CONTEXT Aflatoxins (AFs) are highly hazardous mycotoxins with potent carcinogenic, mutagenic and immune disregulatory properties. Cytochrome P450 (CYP) isoforms are central for enhanced AFB₁ toxicity in situ. It remains to be seen whether and how these AFB₁ activators work in human leukocytes. OBJECTIVE To investigate the involvement of CYP isoforms in AFB₁ toxicity of circulating mononuclear cells, we examined the impact of environmentally relevant levels of AFB1 on lymphocytes and monocytes. MATERIALS AND METHODS Very low and moderate doses of AFB₁ with/without CYP inducers on transcription of key CYP isoforms and toll-like receptor 4 (TLR4) were examined in human lymphocytes, monocytes and HepG2 cells; cell cycle distribution and viability were also analyzed in AFB₁-exposed lymphocytes and monocytes. RESULTS Only CYP1A1, CYP1B1, CYP3A4, CYP3A5 and CYP3A7 expressed in lymphocytes and monocytes. TLR4 much more expressed in monocytes than in lymphocytes, but HepG2 showed little TLR4 transcription. While CYP1A1, CYP1B1 and CYP3A4 were highly induced by AFB₁ in monocytes, in lymphocytes only CYP1A1 was induced. Among CYP1A1, CYP1B1 and CYP3A4 only CYP1A1 responded to low and moderate levels of AFB₁. Enhanced transcripts of CYPs by AFB₁ yielded little synergies on TLR4 transcription in lymphocytes and monocytes. Cell cycle arrest and necrosis were also detected in AFB₁-exposed lymphocytes and monocytes. CONCLUSIONS Our novel findings indicate that AFB₁ more intensively stimulates CYP genes expression in monocytes than in lymphocytes. Mechanistically, this could explain a more pronounced immunotoxicity of AFB₁ in myeloid than in lymphoid lineage cells in vitro/situ/vivo.
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Affiliation(s)
- Abbas Bahari
- Department of Pathobiology, Section Immunology, Faculty of Veterinary Medicine, Ferdowsi University of Mashhad , Mashhad , Iran
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16
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17
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Impairment of alveolar type-II cells involved in the toxicity of Aflatoxin G1 in rat lung. Food Chem Toxicol 2012; 50:3222-8. [DOI: 10.1016/j.fct.2012.06.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 06/06/2012] [Accepted: 06/07/2012] [Indexed: 11/18/2022]
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18
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Hoenerhoff MJ, Hong HH, Ton TV, Lahousse SA, Sills RC. A review of the molecular mechanisms of chemically induced neoplasia in rat and mouse models in National Toxicology Program bioassays and their relevance to human cancer. Toxicol Pathol 2009; 37:835-48. [PMID: 19846892 PMCID: PMC3524969 DOI: 10.1177/0192623309351726] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Tumor response in the B6C3F1 mouse, F344 rat, and other animal models following exposure to various compounds provides evidence that people exposed to these or similar compounds may be at risk for developing cancer. Although tumors in rodents and humans are often morphologically similar, underlying mechanisms of tumorigenesis are often unknown and may be different between the species. Therefore, the relevance of an animal tumor response to human health would be better determined if the molecular pathogenesis were understood. The underlying molecular mechanisms leading to carcinogenesis are complex and involve multiple genetic and epigenetic events and other factors. To address the molecular pathogenesis of environmental carcinogens, the authors examine rodent tumors (e.g., lung, colon, mammary gland, skin, brain, mesothelioma) for alterations in cancer genes and epigenetic events that are associated with human cancer. National Toxicology Program (NTP) studies have identified several genetic alterations in chemically induced rodent neoplasms that are important in human cancer. Identification of such alterations in rodent models of chemical carcinogenesis caused by exposure to environmental contaminants, occupational chemicals, and other compounds lends further support that they are of potential human health risk. These studies also emphasize the importance of molecular evaluation of chemically induced rodent tumors for providing greater public health significance for NTP evaluated compounds.
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Affiliation(s)
- Mark J Hoenerhoff
- Cellular and Molecular Pathology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27519, USA.
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Pereira MA, Tao LH, Wang W, Gunning WT, Lubet R. CHEMOPREVENTION: MOUSE COLON AND LUNG TUMOR BIOASSAY AND MODULATION OF DNA METHYLATION AS A BIOMARKER. Exp Lung Res 2009; 31:145-63. [PMID: 15824018 DOI: 10.1080/01902140490495534] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Lung and colon tumors were induced in A/J, C3H, and A/J X C3H (AC3) mice by administering 16 mg/kg vinyl carbamate followed by 6 weekly doses of 12 mg/kg azoxymethane (AOM). Beginning 1 week after carcinogen treatment, the mice received chemopreventive agents, dexamethasone or piroxicam, at 0.1 and 75 mg/kg in the diet, respectively. Both AOM and vinyl carbamate induces lung tumors, but only AOM induced colon tumors. The strain sensitivity for both colon and lung tumors was A/J > AC3 > C3H mice. Dexamethasone and piroxicam reduced the multiplicity of colon and lung tumors in A/J and AC3 mice, demonstrating the advantage of a combined colon and lung bioassay. The ability of budesonide, a drug that prevents mouse lung tumors, to modulate DNA methylation in vinyl carbamate-induced lung tumors was also determined. Budesonide administered for only 7 days prior to sacrifice caused a dose-dependent (0.6 to 2.4 mg/kg diet) reversal in tumors of DNA hypomethylation and hypomethylation of the insulin-like growth factor (IGF)-II gene in the differentially methylated region (DMR) 2 region of exons 4 to 5. Longer treatment with budesonide reversed hypomethylation when administered up to the time of sacrifice. These results indicate that reversal of the hypomethylation of DNA and of specific genes in lung tumors may be applicable as a surrogate end-point biomarker for chemoprevention.
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Affiliation(s)
- Michael A Pereira
- Department of Pathology, Medical College of Ohio, Toledo, Ohio, USA.
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20
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Paget V, Sichel F, Garon D, Lechevrel M. Aflatoxin B1-induced TP53 mutational pattern in normal human cells using the FASAY (Functional Analysis of Separated Alleles in Yeast). Mutat Res 2008; 656:55-61. [PMID: 18725321 DOI: 10.1016/j.mrgentox.2008.07.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 06/17/2008] [Accepted: 07/12/2008] [Indexed: 11/29/2022]
Abstract
Mutations in the TP53 gene are the most common alterations in human tumours. In hepatocellular carcinoma (HCC) related to exposure to aflatoxin B1, a specific G>T transversion in codon 249 is classically described as a hot spot. However, AFB1 is suspected to be a potent carcinogen in tissues other than the liver. By using the FASAY functional assay in yeast, the present study aimed at depicting the mutational pattern of TP53 in normal human fibroblasts after in vitro exposure to AFB1. Molecular analysis of mutants revealed that codon 245 was the main hot spot, whereas no mutations were found in codon 249. The locations of mutations within GG and GC/CG sequences are well in accordance with AFB1-adduct location data. In our assay with normal human fibroblasts, AFB1 mainly induced G>A transitions, followed by G>T and A>G mutations. This suggests that G>T transversions at codon 249 were likely the result of a selection bias in human HCC rather than a true fingerprint of AFB1 adducts. Indeed, a comparison of the mutation pattern with that found in human HCC excluding codon 249 reveals that the two spectra are quite similar. Furthermore, the similarity between our in vitro spectrum with that identified in AFB1-induced lung tumours in mice suggests that AFB1 may be a potent lung carcinogen in humans.
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Affiliation(s)
- Vincent Paget
- GRECAN EA1772-IFR 146 ICORE, Université de Caen Basse-Normandie et Centre François Baclesse, Av. du Général Harris, 14076 Caen-cedex 05, France
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21
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Guindon KA, Foley JF, Maronpot RR, Massey TE. Failure of catalase to protect against aflatoxin B1-induced mouse lung tumorigenicity. Toxicol Appl Pharmacol 2007; 227:179-83. [PMID: 18155117 DOI: 10.1016/j.taap.2007.10.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Revised: 10/12/2007] [Accepted: 10/16/2007] [Indexed: 10/22/2022]
Abstract
The carcinogenic mycotoxin aflatoxin B(1) (AFB(1)) induces 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation in mouse lung, an effect that can be prevented by treatment with polyethylene glycol-conjugated catalase (PEG-CAT). G-->T transversion mutation in K-ras, an early event in AFB(1)-induced mouse lung carcinogenesis, is thought to result from AFB(1)-8,9-exo-epoxide binding to DNA to form AFB(1)-N(7)-guanine, but may also result from formation of 8-OHdG. Therefore, oxidative DNA damage may be important in AFB(1) carcinogenicity. The objective of this study was to determine whether PEG-CAT would prevent AFB(1) tumorigenicity. Mouse lung tumorigenesis was assessed following treatment of female A/J mice with 300 kU/kg PEG-CAT ip and/or 50 mg/kg AFB(1). Mice were killed 7 months post-treatment and tumors greater than 1 mm in diameter were excised. Unexpectedly, the mean number of tumors per mouse in the PEG-CAT+AFB(1) group (8.81+/-3.64, n=47) was greater than that of the group treated with AFB(1) alone (7.05+/-3.45, n=42) (P<0.05). The tumors obtained from mice treated with PEG-CAT+AFB(1) were larger than those from mice treated with AFB(1) alone (P<0.05). There was no difference in K-ras exon 1 mutation spectrum or in the histological diagnosis of tumors between AFB(1) and PEG-CAT+AFB(1) groups (P>0.05). In vitro incubation with mouse liver catalase (CAT) resulted in conversion of [(3)H]AFB(1) into a DNA-binding species, a possible explanation for the results observed in vivo. These results demonstrate that PEG-CAT is not protective against AFB(1) carcinogenicity in mouse lung despite preventing DNA oxidation.
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Affiliation(s)
- Katherine A Guindon
- Department of Pharmacology and Toxicology, Queen's University, Kingston, Ontario, Canada K7L 3N6
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22
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Wakamatsu N, Devereux TR, Hong HHL, Sills RC. Overview of the molecular carcinogenesis of mouse lung tumor models of human lung cancer. Toxicol Pathol 2007; 35:75-80. [PMID: 17325975 PMCID: PMC2094362 DOI: 10.1080/01926230601059993] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Lung cancer is the leading cause of cancer death worldwide, and the need to develop better diagnostic techniques and therapies is urgent. Mouse models have been utilized for studying carcinogenesis of human lung cancers, and many of the major genetic alterations detected in human lung cancers have also been identified in mouse lung tumors. The importance of mouse models for understanding human lung carcinogenic processes and in developing early diagnostic techniques, preventive measures and therapies cannot be overstated. In this report, the major known molecular alterations in lung tumorigenesis of mice are reviewed and compared to those in humans.
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Affiliation(s)
- Nobuko Wakamatsu
- Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
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23
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Bedard LL, Massey TE. Aflatoxin B1-induced DNA damage and its repair. Cancer Lett 2006; 241:174-83. [PMID: 16458422 DOI: 10.1016/j.canlet.2005.11.018] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2005] [Revised: 11/16/2005] [Accepted: 11/18/2005] [Indexed: 01/09/2023]
Abstract
Aflatoxin B(1) (AFB(1))-N(7)-guanine is the predominant adduct formed upon the reaction of AFB(1)-8,9-exo-epoxide with guanine residues in DNA. AFB(1)-N(7)-guanine can convert to the ring-opened formamidopyrimidine, or the adducted strand can undergo depurination. AFB(1)-N(7)-guanine and AFB(1)-formamidopyrimidine are thought to be predominantly repaired by nucleotide excision repair in bacteria, yeast and mammals. Although AFB(1)-formamidopyrimidine is removed less efficiently than AFB(1)-N(7)-guanine in mammals, both lesions are repaired with equal efficiencies in bacteria, reflecting differences in damage recognition between bacterial and mammalian repair systems. Furthermore, DNA repair activity and modulation of repair by AFB(1) seem to be major determinants of susceptibility to AFB(1)-induced carcinogenesis.
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Affiliation(s)
- Leanne L Bedard
- Department of Pharmacology and Toxicology, Queen's University, Botterell Hall, Kingston, Ont., Canada K7L 3N6
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24
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Zhu LR, Thomas PE, Lu G, Reuhl KR, Yang GY, Wang LD, Wang SL, Yang CS, He XY, Hong JY. CYP2A13 in human respiratory tissues and lung cancers: an immunohistochemical study with a new peptide-specific antibody. Drug Metab Dispos 2006; 34:1672-6. [PMID: 16815959 DOI: 10.1124/dmd.106.011049] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human cytochrome P450 2A13 (CYP2A13) is highly efficient in the metabolic activation of a tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and another potent carcinogen, aflatoxin B1 (AFB1). Although previous studies demonstrated that CYP2A13 mRNA is predominantly expressed in human respiratory tissues, expression of CYP2A13 protein in these tissues and the involved cell types have not been determined because of the lack of CYP2A13-specific antibodies. To explore the toxicological and physiological function of CYP2A13, it is important to understand the tissue/cellular distribution of CYP2A13 protein. In this study, we generated a peptide-specific antibody against human CYP2A13 and demonstrated by immunoblot analysis that this antibody does not cross-react with heterologously expressed human CYP2A6 and mouse CYP2A5 proteins, both sharing a high degree of amino acid sequence similarity with CYP2A13. Nor does the antibody cross-react with heterologously expressed human CYP3A4, CYP2S1, or any of the cytochrome P450 enzymes present in the human liver microsomes. Using this highly specific antibody for immunohistochemical staining, we detected a high level of CYP2A13 protein expression in the epithelial cells of human bronchus and trachea, but a rare distribution in the alveolar cells. There was little expression of CYP2A13 protein in different types of lung cancers. In consideration of the high efficiency of CYP2A13 in NNK metabolic activation, our result is consistent with the reported observations that most smoking-related human lung cancers are bronchogenic and supports that CYP2A13-catalyzed in situ activation may play a critical role in human lung carcinogenesis related to NNK and AFB1 exposure.
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Affiliation(s)
- Liang-Ru Zhu
- School of Public Health, Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Room 385, 683 Hoes Lane West, Piscataway, NJ 08854, USA
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25
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He XY, Tang L, Wang SL, Cai QS, Wang JS, Hong JY. Efficient activation of aflatoxin B1 by cytochrome P450 2A13, an enzyme predominantly expressed in human respiratory tract. Int J Cancer 2006; 118:2665-71. [PMID: 16385575 DOI: 10.1002/ijc.21665] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The worldwide human exposure to aflatoxin B1 (AFB1), particularly in developing countries, remains to be a serious public health concern. Although AFB1 is best known as a hepatocarcinogen, epidemiological studies have shown a positive association between human lung cancer occurrence and inhalation exposure to AFB1. Cytochrome P450 (CYP)-catalyzed metabolic activation is required for AFB1 to exert its carcinogenicity. Previous studies have identified CYP1A2 and CYP3A4 as the major enzymes for AFB1 activation in human liver. However, the key CYP enzymes in human lung that can efficiently activate AFB1 in situ are unknown. In the present study, we demonstrate that CYP2A13, an enzyme predominantly expressed in human respiratory tract, has a significant activity in metabolizing AFB1 to its carcinogenic/toxic AFB1-8,9-epoxide and AFM1-8,9-epoxide at both low (15 microM) and high (150 microM) substrate concentrations. Under the same conditions, there was no detectable AFB1 epoxide formation by CYP2A6, which was also reported to be involved in the metabolic activation of AFB1. Consistent with the activity data, there was an approximately 800-fold difference in LC50 values of AFB1 (48-hr treatment) between Chinese hamster ovary (CHO) cells expressing CYP2A13 and CYP2A6 (50 nM versus 39 microM). We further demonstrate that amino acid residues Ala117 and His372 in CYP2A13 protein are important for AFB1 epoxidation and its related cytotoxicity. Our results suggest that CYP2A13-catalyzed metabolic activation in situ may play a critical role in human lung carcinogenesis related to inhalation exposure to AFB1.
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Affiliation(s)
- Xiao-Yang He
- School of Public Health/Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA
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Ton TVT, Hong HHL, Anna CH, Dunnick JK, Devereux TR, Sills RC, Kim Y. Predominant K-ras codon 12 G --> A transition in chemically induced lung neoplasms in B6C3F1 mice. Toxicol Pathol 2004; 32:16-21. [PMID: 14713543 DOI: 10.1080/01926230490260682] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Based on long-term toxicity and carcinogenicity studies in B6C3F1 mice conducted by the National Toxicology Program, 2,2-Bis(bromomethyl)-1,3-propanediol (BMP) and tetranitromethane (TNM) have been identified as carcinogens. Following 2 yr of exposure to 312, 625, or 1,250 ppm BMP in feed, or exposure to 0.5 or 2 ppm TNM by inhalation, increased incidences of lung neoplasms were observed in B6C3F1 mice at all exposure concentrations compared to unexposed mice. The present study characterizes genetic alterations in the K-ras protooncogene in BMP- and TNM-induced lung neoplasms, respectively, and compares the findings to spontaneous lung neoplasms from corresponding control mice. The frequencies of the K-ras mutations were 57% (29/51) in BMP-induced lung neoplasms compared to 15% (3/20) in lung neoplasms from dosed feed control mice, and 54% (14/26) in TNM-induced lung neoplasms compared to 60% (3/5) in lung neoplasms from inhalation control mice. G --> A transitions at the second base of the K-ras codon 12 (GGT --> GAT) were the most frequent pattern of K-ras mutations identified in BMP-induced (20/29) and TNM-induced lung neoplasms (13/14), which differed from the mutational patterns identified in the lung neoplasms from unexposed control mice. These results indicate that mutations in the K-ras gene are involved in B6C3F1 lung carcinogenesis following BMP- and TNM-exposure, and the high frequency and specificity of the ras mutation profile in lung neoplasms (G --> A transition) may be due to in vivo genotoxicity by the parent compounds or their metabolites.
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Affiliation(s)
- Thai-Vu T Ton
- National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
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Lorico A, Nesland J, Emilsen E, Fodstad O, Rappa G. Role of the multidrug resistance protein 1 gene in the carcinogenicity of aflatoxin B1: investigations using mrp1-null mice. Toxicology 2002; 171:201-5. [PMID: 11836025 DOI: 10.1016/s0300-483x(01)00584-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The multidrug resistance protein 1 (MRP1) protects cells from xenobiotics by extruding from the intracellular compartment glutathione (GSH)-S-conjugates, glucuronyl conjugates and sulfate conjugates and by the co-export of xenobiotic(s) and GSH. An ATP-dependent transport of aflatoxin B1 (AFB1) and its GSH conjugates by MRP1 has been previously demonstrated in vitro. In the present study, we have sought to investigate the in vivo role of MRP1 in AFB1 carcinogenicity, by comparing the incidence of tumors occurring in mrp1 (+/+) and mrp1 (-/-) mice 12 months after an 8 weeks exposure to AFB1. The carcinogen induced a similar number of lung and liver tumors in both strains. Most lung tumors were of the solid type and showed a moderate degree of differentiation in both mrp1 (+/+) and mrp1 (-/-) mice. These data provide direct evidence that in vivo MRP1 does not protect from AFB1 carcinogenicity. Due to the redundancy of transmembrane export pumps, other pump(s) may effectively vicariate for MRP1-mediated transport of AFB1 and its glutathione conjugates.
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Affiliation(s)
- Aurelio Lorico
- Department of Tumor Biology, The Norwegian Radium Hospital, University of Oslo, Montebello, N-0310, Oslo, Norway.
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Abstract
Lung cells isolated from AC3F1 (A/J x C3H/HeJ) mice 7 wk after treatment with the carcinogenic mycotoxin aflatoxin B1 (AFB1) were examined for point mutations in the Ki-ras oncogene. Ki-ras mutant allele frequencies in fractions enriched with nonciliated bronchiolar epithelial (Clara) cells were consistently higher than in alveolar type II cell fractions. Mutant alleles were undetectable or minimal in macrophage- and polymorphonuclear leukocyte-enriched fractions. In cells from vehicle (dimethyl sulfoxide)-treated mice, small proportions of mutant Ki-ras alleles were found in the Clara cell-enriched fraction but not in other cell fractions. The results indicated that Clara cells are particularly susceptible to AFB1-induced Ki-ras mutation, an early event in AFB1-induced mouse lung tumorigenesis.
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Affiliation(s)
- P J Donnelly
- Department of Pharmacology and Toxicology, Queen's University, Kingston, Ontario, Canada
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