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Wu J, Wu J, Clabaugh G, Wang Y. Replication Studies of Alkyl Phosphotriester Lesions in Human Cells. Chem Res Toxicol 2024; 37:451-454. [PMID: 38417054 PMCID: PMC10947855 DOI: 10.1021/acs.chemrestox.3c00366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2024]
Abstract
Alkyl phosphotriester (alkyl-PTE) lesions in DNA are shown to be poorly repaired; however, little is known about how these lesions impact DNA replication in human cells. Here, we investigated how the SP and RP diastereomers of four alkyl-PTE lesions (alkyl = Me, Et, nPr, or nBu) at the TT site perturb DNA replication in HEK293T cells. We found that these lesions moderately impede DNA replication and that their replicative bypass is accurate. Moreover, CRISPR-Cas9-mediated depletion of Pol η or Pol ζ resulted in significantly attenuated bypass efficiencies for both diastereomers of nPr- and nBu-PTE adducts, and the SP diastereomer of Et-PTE. Diminished bypass efficiencies were also detected for the Rp diastereomer of nPr- and nBu-PTE lesions upon ablation of Pol κ. Together, our study uncovered the impact of the alkyl-PTE lesions on DNA replication in human cells and revealed the roles of individual translesion synthesis DNA polymerases in bypassing these lesions.
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Affiliation(s)
- Jun Wu
- Department of Chemistry, University of California Riverside, Riverside, California 92521-0403, United States
| | - Jiabin Wu
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, California 92521-0403, United States
| | - Garrit Clabaugh
- Department of Chemistry, University of California Riverside, Riverside, California 92521-0403, United States
| | - Yinsheng Wang
- Department of Chemistry, University of California Riverside, Riverside, California 92521-0403, United States
- Environmental Toxicology Graduate Program, University of California Riverside, Riverside, California 92521-0403, United States
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2
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Size- and Stereochemistry-Dependent Transcriptional Bypass of DNA Alkyl Phosphotriester Adducts in Mammalian Cells. DNA 2022; 2:221-230. [PMID: 36911626 PMCID: PMC9997456 DOI: 10.3390/dna2040016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Environmental, endogenous and therapeutic alkylating agents can react with internucleotide phosphate groups in DNA to yield alkyl phosphotriester (PTE) adducts. Alkyl-PTEs are induced at relatively high frequencies and are persistent in mammalian tissues; however, their biological consequences in mammalian cells have not been examined. Herein, we assessed how alkyl-PTEs with different alkyl group sizes and stereochemical configurations (S P and R P diastereomers of Me and nPr) affect the efficiency and fidelity of transcription in mammalian cells. We found that, while the R P diastereomer of Me- and nPr-PTEs constituted moderate and strong blockages to transcription, respectively, the S P diastereomer of the two lesions did not appreciably perturb transcription efficiency. In addition, none of the four alkyl-PTEs induced mutant transcripts. Furthermore, polymerase η assumed an important role in promoting transcription across the S P-Me-PTE, but not any of other three lesions. Loss of other translesion synthesis (TLS) polymerases tested, including Pol κ, Pol ι, Pol ξ and REV1, did not alter the transcription bypass efficiency or mutation frequency for any of the alkyl-PTE lesions. Together, our study provided important new knowledge about the impact of alkyl-PTE lesions on transcription and expanded the substrate pool of Pol η in transcriptional bypass.
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3
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Ma B, Villalta PW, Hochalter JB, Stepanov I, Hecht SS. Methyl DNA phosphate adduct formation in lung tumor tissue and adjacent normal tissue of lung cancer patients. Carcinogenesis 2020; 40:1387-1394. [PMID: 30873516 DOI: 10.1093/carcin/bgz053] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 02/25/2019] [Accepted: 03/08/2019] [Indexed: 11/14/2022] Open
Abstract
The formation of methyl DNA adducts is a critical step in carcinogenesis initiated by the exposure to methylating carcinogens. Methyl DNA phosphate adducts, formed by methylation of the oxygen atoms of the DNA phosphate backbone, have been detected in animals treated with methylating carcinogens. However, detection of these adducts in human tissues has not been reported. We developed an ultrasensitive liquid chromatography-nanoelectrospray ionization-high resolution tandem mass spectrometry method for detecting methyl DNA phosphate adducts. Using 50 μg of human lung DNA, a limit of quantitation of two adducts/1010 nucleobases was achieved. Twenty-two structurally unique methyl DNA phosphate adducts were detected in human lung DNA. The adduct levels were measured in both tumor and adjacent normal tissues from 30 patients with lung cancer, including 13 current smokers and 17 current non-smokers, as confirmed by measurements of urinary cotinine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol. Levels of total methyl DNA phosphate adducts in normal lung tissues were higher in smokers than non-smokers, with an average of 13 and 8 adducts/109 nucleobases, respectively. Methyl DNA phosphate adducts were also detected in lung tissues from untreated rats with steady-state levels of 5-7 adducts/109 nucleobases over a period of 70 weeks. This is the first study to report the detection of methyl DNA phosphate adducts in human lung tissues. The results provide new insights toward using these DNA adducts as potential biomarkers to study human exposure to environmental methylating carcinogens.
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Affiliation(s)
- Bin Ma
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Peter W Villalta
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | | | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Stephen S Hecht
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
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4
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Wu J, Wang P, Wang Y. Cytotoxic and mutagenic properties of alkyl phosphotriester lesions in Escherichia coli cells. Nucleic Acids Res 2019. [PMID: 29514270 PMCID: PMC5934668 DOI: 10.1093/nar/gky140] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Exposure to many endogenous and exogenous agents can give rise to DNA alkylation, which constitutes a major type of DNA damage. Among the DNA alkylation products, alkyl phosphotriesters have relatively high frequencies of occurrence and are resistant to repair in mammalian tissues. However, little is known about how these lesions affect the efficiency and fidelity of DNA replication in cells or how the replicative bypass of these lesions is modulated by translesion synthesis DNA polymerases. In this study, we synthesized oligodeoxyribonucleotides containing four pairs (Sp and Rp) of alkyl phosphotriester lesions at a defined site, and examined how these lesions are recognized by DNA replication machinery in Escherichia coli cells. We found that the Sp diastereomer of the alkyl phosphotriester lesions could be efficiently bypassed, whereas the Rp counterparts moderately blocked DNA replication. Moreover, the Sp-methyl phosphotriester induced TT→GT and TT→GC mutations at the flanking TT dinucleotide site, and the induction of these mutations required Ada protein, which is known to remove efficiently the methyl group from the Sp-methyl phosphotriester. Together, our study provided a comprehensive understanding about the recognition of alkyl phosphotriester lesions by DNA replication machinery in cells, and revealed for the first time the Ada-dependent induction of mutations at the Sp-methyl phosphotriester site.
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Affiliation(s)
- Jiabin Wu
- Environmental Toxicology Graduate Program and Department of Chemistry, University of California Riverside, Riverside, CA 92521-0403, USA
| | - Pengcheng Wang
- Environmental Toxicology Graduate Program and Department of Chemistry, University of California Riverside, Riverside, CA 92521-0403, USA
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program and Department of Chemistry, University of California Riverside, Riverside, CA 92521-0403, USA
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5
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Wang H, Li X, Zhao G, Xu L, Wang S, Nie M, Hua C, Shang P, Pan L, Zhao J, Qiao L, Liu K, Hu K, Su J, Cai J, Xie F. Analysis of methyl DNA adducts and metabolites in BEAS-2B cells induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. Toxicol Mech Methods 2019; 29:499-510. [DOI: 10.1080/15376516.2019.1611982] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Huiting Wang
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Xiang Li
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Ge Zhao
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Liangtao Xu
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Sheng Wang
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Mingxuan Nie
- Zhengzhou Foreign Language School, Zhengzhou, China
| | - Chenfeng Hua
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Pingping Shang
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Lining Pan
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Junwei Zhao
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Liangjun Qiao
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Kejian Liu
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
| | - Kai Hu
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
- Henan University of Chinese Medicine, Zhengzhou, China
| | - Jiakun Su
- China Tobacco Jiangxi Industrial LLC, Nanchang, China
| | - Jibao Cai
- China Tobacco Jiangxi Industrial LLC, Nanchang, China
| | - Fuwei Xie
- Key Laboratory of Tobacco Chemistry, Zhengzhou Tobacco Research Institute of CNTC, Zhengzhou, China
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Ma B, Stepanov I, Hecht SS. Recent Studies on DNA Adducts Resulting from Human Exposure to Tobacco Smoke. TOXICS 2019; 7:E16. [PMID: 30893918 PMCID: PMC6468371 DOI: 10.3390/toxics7010016] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 03/09/2019] [Accepted: 03/13/2019] [Indexed: 12/22/2022]
Abstract
DNA adducts are believed to play a central role in the induction of cancer in cigarette smokers and are proposed as being potential biomarkers of cancer risk. We have summarized research conducted since 2012 on DNA adduct formation in smokers. A variety of DNA adducts derived from various classes of carcinogens, including aromatic amines, polycyclic aromatic hydrocarbons, tobacco-specific nitrosamines, alkylating agents, aldehydes, volatile carcinogens, as well as oxidative damage have been reported. The results are discussed with particular attention to the analytical methods used in those studies. Mass spectrometry-based methods that have higher selectivity and specificity compared to 32P-postlabeling or immunochemical approaches are preferred. Multiple DNA adducts specific to tobacco constituents have also been characterized for the first time in vitro or detected in vivo since 2012, and descriptions of those adducts are included. We also discuss common issues related to measuring DNA adducts in humans, including the development and validation of analytical methods and prevention of artifact formation.
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Affiliation(s)
- Bin Ma
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Stephen S Hecht
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA.
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Li Y, Ma B, Cao Q, Balbo S, Zhao L, Upadhyaya P, Hecht SS. Mass Spectrometric Quantitation of Pyridyloxobutyl DNA Phosphate Adducts in Rats Chronically Treated with N'-Nitrosonornicotine. Chem Res Toxicol 2019; 32:773-783. [PMID: 30740971 DOI: 10.1021/acs.chemrestox.9b00007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The tobacco-specific carcinogens N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) require metabolic activation to exert their carcinogenicity. NNN and NNK are metabolized to the same reactive diazonium ions, which alkylate DNA forming pyridyloxobutyl (POB) DNA base and phosphate adducts. We have characterized the formation of both POB DNA base and phosphate adducts in NNK-treated rats and the formation of POB DNA base adducts in NNN-treated rats. However, POB DNA phosphate adducts in NNN-treated rats are still uncharacterized. In this study, we quantified the levels of POB DNA phosphate adducts in tissues of rats chronically treated with ( S)-NNN or ( R)-NNN for 10, 30, 50, and 70 weeks during a carcinogenicity study. The highest amounts of POB DNA phosphate adducts were observed in the esophagus of the ( S)-NNN-treated rats, with a maximum level of 5400 ± 317 fmol/mg DNA at 50 weeks. The abundance of POB DNA phosphate adducts in the esophagus was consistent with the results of the carcinogenicity study showing that the esophagus was the primary site of tumor formation from treatment with ( S)-NNN. Compared to the ( R)-NNN group, the levels of POB DNA phosphate adducts were higher in the oral mucosa, esophagus, and liver, while lower in the nasal mucosa of the ( S)-NNN-treated rats. Among 10 combinations of all isomers of POB DNA phosphate adducts, Ap(POB)C and combinations with thymidine predominated across all the rat tissues examined. In the primary target tissue, esophageal mucosa, Ap(POB)C accounted for ∼20% of total phosphate adducts in the ( S)-NNN treatment group throughout the 70 weeks, with levels ranging from 780 ± 194 to 1010 ± 700 fmol/mg DNA. The results of this study showed that POB DNA phosphate adducts were present in high levels and persisted in target tissues of rats chronically treated with ( S)- or ( R)-NNN. These results improve our understanding of DNA damage during NNN-induced carcinogenesis. The predominant POB DNA phosphate isomers observed, such as Ap(POB)C, may serve as biomarkers for monitoring chronic exposure of tobacco-specific nitrosamines in humans.
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Affiliation(s)
- Yupeng Li
- Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Bin Ma
- Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Qing Cao
- Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Silvia Balbo
- Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Lijiao Zhao
- Beijing Key Laboratory of Environmental and Virus Oncology, College of Life Science and Bioengineering , Beijing University of Technology , Beijing 100124 , China
| | - Pramod Upadhyaya
- Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States
| | - Stephen S Hecht
- Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States
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8
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Ma B, Zarth AT, Carlson ES, Villalta PW, Upadhyaya P, Stepanov I, Hecht SS. 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. Carcinogenesis 2018; 39:232-241. [PMID: 29194532 PMCID: PMC5862267 DOI: 10.1093/carcin/bgx135] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 10/25/2017] [Accepted: 11/25/2017] [Indexed: 02/01/2023] Open
Abstract
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.
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Affiliation(s)
- Bin Ma
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Adam T Zarth
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Erik S Carlson
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Peter W Villalta
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Pramod Upadhyaya
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Stephen S Hecht
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
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Ma B, Zarth AT, Carlson ES, Villalta PW, Upadhyaya P, Stepanov I, Hecht SS. Methyl DNA Phosphate Adduct Formation in Rats Treated Chronically with 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone and Enantiomers of Its Metabolite 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol. Chem Res Toxicol 2018; 31:48-57. [PMID: 29131934 PMCID: PMC5770887 DOI: 10.1021/acs.chemrestox.7b00281] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Indexed: 11/29/2022]
Abstract
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 tobacco users. NNK is stereoselectively and reversibly metabolized to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), which is also a lung carcinogen. Both NNK and NNAL undergo metabolic activation by α-hydroxylation on their methyl groups to form pyridyloxobutyl and pyridylhydroxybutyl DNA base and phosphate adducts, respectively. α-Hydroxylation also occurs on the α-methylene carbons of NNK and NNAL to produce methane diazohydroxide, which reacts with DNA to form methyl DNA base adducts. DNA adducts of NNK and NNAL are important in their mechanisms of carcinogenesis. In this study, we characterized and quantified methyl DNA phosphate adducts in the lung of rats treated with 5 ppm of NNK, (S)-NNAL, or (R)-NNAL in drinking water for 10, 30, 50, and 70 weeks, by using a novel liquid chromatography-nanoelectrospray ionization-high resolution tandem mass spectrometry method. A total of 23, 21, and 22 out of 32 possible methyl DNA phosphate adducts were detected in the lung tissues of rats treated with NNK, (S)-NNAL, and (R)-NNAL, respectively. Levels of the methyl DNA phosphate adducts were 2290-4510, 872-1120, and 763-1430 fmol/mg DNA, accounting for 15-38%, 8%, and 5-9% of the total measured DNA adducts in rats treated with NNK, (S)-NNAL, and (R)-NNAL, respectively. The methyl DNA phosphate adducts characterized in this study further enriched the diversity of DNA adducts formed by NNK and NNAL. These results provide important new data regarding NNK- and NNAL-derived DNA damage and new insights pertinent to future mechanistic and biomonitoring studies of NNK, NNAL, and other chemical methylating agents.
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Affiliation(s)
- Bin Ma
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
| | - Adam T. Zarth
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
| | - Erik S. Carlson
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
| | - Peter W. Villalta
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
| | - Pramod Upadhyaya
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
| | - Stephen S. Hecht
- Masonic Cancer Center, University of Minnesota, 2231 Sixth Street SE, 2-152 CCRB, Minneapolis, Minnesota 55455, United States
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Ma B, Zarth AT, Carlson ES, Villalta PW, Stepanov I, Hecht SS. Pyridylhydroxybutyl and pyridyloxobutyl DNA phosphate adduct formation in rats treated chronically with enantiomers of the tobacco-specific nitrosamine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol. Mutagenesis 2017; 32:561-570. [PMID: 29186507 PMCID: PMC5907908 DOI: 10.1093/mutage/gex031] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 10/17/2017] [Indexed: 01/24/2023] Open
Abstract
The tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is metabolically converted to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in a reaction which is both stereoselective and reversible. NNAL is also a lung carcinogen, with both (R)-NNAL and (S)-NNAL inducing a high incidence of lung tumours in rats. Both NNAL and NNK undergo metabolic activation to intermediates which react with DNA to form pyridylhydroxybutyl and pyridyloxobutyl DNA adducts, respectively. DNA adduct formation by NNAL and NNK is an important step in their mechanisms of carcinogenesis. In this study, we quantified both pyridylhydroxybutyl and pyridyloxobutyl DNA phosphate adducts in the lung of rats treated with 5 ppm of (R)-NNAL or (S)-NNAL in drinking water for 10, 30, 50 and 70 weeks. In (R)-NNAL-treated rats, the pyridylhydroxybutyl and pyridyloxobutyl phosphate adducts were 4530-6920 fmol/mg DNA and 46-175 fmol/mg DNA, accounting for 45-51% and 0.3-1% of the total measured DNA phosphate and base adducts, respectively. In (S)-NNAL-treated rats, the two types of phosphate adducts were 3480-4180 fmol/mg DNA and 1180-4650 fmol/mg DNA, accounting for 30-36% and 11-38% of the total adducts, respectively. Distinct patterns of adduct formation were observed, with higher levels of NNAL-derived pyridylhydroxybutyl phosphate adducts and lower levels of NNK-derived pyridyloxobutyl phosphate adducts in the (R)-NNAL treatment group than the (S)-NNAL group. The persistence and increase over time of certain pyridylhydroxybutyl phosphate adducts over the course of the study suggest that these adducts could be useful biomarkers of chronic exposure to NNAL and NNK. The results of this study provide important new information regarding DNA damage by NNAL and NNK, and contribute to understanding mechanisms of tobacco-related carcinogenesis.
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Affiliation(s)
- Bin Ma
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Adam T Zarth
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Erik S Carlson
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Peter W Villalta
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Stephen S Hecht
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
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11
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Ma B, Villalta PW, Zarth AT, Kotandeniya D, Upadhyaya P, Stepanov I, Hecht SS. Comprehensive High-Resolution Mass Spectrometric Analysis of DNA Phosphate Adducts Formed by the Tobacco-Specific Lung Carcinogen 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone. Chem Res Toxicol 2015; 28:2151-9. [PMID: 26398225 PMCID: PMC4652278 DOI: 10.1021/acs.chemrestox.5b00318] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Indexed: 11/28/2022]
Abstract
The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 1) is a potent lung carcinogen in laboratory animals and is believed to play a key role in the development of lung cancer in smokers. Metabolic activation of NNK leads to the formation of pyridyloxobutyl DNA adducts, a critical step in its mechanism of carcinogenesis. In addition to DNA nucleobase adducts, DNA phosphate adducts can be formed by pyridyloxobutylation of the oxygen atoms of the internucleotidic phosphodiester linkages. We report the use of a liquid chromatography-nanoelectrospray ionization-high-resolution tandem mass spectrometry technique to characterize 30 novel pyridyloxobutyl DNA phosphate adducts in calf thymus DNA (CT-DNA) treated with 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone (NNKOAc, 2), a regiochemically activated form of NNK. A (15)N3-labeled internal standard was synthesized for one of the most abundant phosphate adducts, dCp[4-oxo-4-(3-pyridyl)butyl]dC (CpopC), and this standard was used to quantify CpopC and to estimate the levels of other adducts in the NNKOAc-treated CT-DNA. Formation of DNA phosphate adducts by NNK in vivo was further investigated in rats treated with NNK acutely (0.1 mmol/kg once daily for 4 days by subcutaneous injection) and chronically (5 ppm in drinking water for 10, 30, 50, and 70 weeks). This study provides the first comprehensive structural identification and quantitation of a panel of DNA phosphate adducts of a structurally complex carcinogen and chemical support for future mechanistic studies of tobacco carcinogenesis in humans.
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Affiliation(s)
- Bin Ma
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
| | - Peter W. Villalta
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
| | - Adam T. Zarth
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
| | - Delshanee Kotandeniya
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
| | - Pramod Upadhyaya
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
| | - Irina Stepanov
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
| | - Stephen S. Hecht
- Masonic
Cancer Center, University of Minnesota, 2231 6th St SE, Minneapolis, Minnesota 55455, United States
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12
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Jones GDD, Le Pla RC, Farmer PB. Phosphotriester adducts (PTEs): DNA's overlooked lesion. Mutagenesis 2009; 25:3-16. [DOI: 10.1093/mutage/gep038] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Gaskell M, Kaur B, Farmer PB, Singh R. Detection of phosphodiester adducts formed by the reaction of benzo[a]pyrene diol epoxide with 2'-deoxynucleotides using collision-induced dissociation electrospray ionization tandem mass spectrometry. Nucleic Acids Res 2007; 35:5014-27. [PMID: 17636312 PMCID: PMC1976470 DOI: 10.1093/nar/gkm526] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this study, we investigated the products formed following the reaction of benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (B[a]PDE) with 2'-deoxynucleoside 3'-monophosphates. The B[a]PDE plus 2'-deoxynucleotide reaction mixtures were purified using solid phase extraction (SPE) and subjected to HPLC with fluorescence detection. Fractions corresponding to reaction product peaks were collected and desalted using SPE prior to analysis for the presence of molecular ions corresponding to m/z 648, 632, 608 and 623 [M-H]- consistent with B[a]PDE adducted (either on the base or phosphate group) 2'-deoxynucleotides of guanine, adenine, cytosine and thymine, respectively, using LC-ESI-MS/MS collision-induced dissociation (CID). Reaction products were identified having CID product ion spectra containing product ions at m/z 452, 436 and 412 [(B[a]Ptriol+base)-H]-, resulting from cleavage of the glycosidic bond between the 2'-deoxyribose and base, corresponding to B[a]PDE adducts of guanine, adenine and cytosine, respectively. Further reaction products were identified having unique CID product ion spectra characteristic of B[a]PDE adduct formation with the phosphate group of the 2'-deoxynucleotide. The presence of product ions at m/z 399 and 497 were observed for all four 2'-deoxynucleotides, corresponding to [(B[a]Ptriol+phosphate)-H]- and [(2'-deoxyribose+phosphate+B[a]Ptriol)-H]-, respectively. In conclusion, this investigation provides the first direct evidence for the formation of phosphodiester adducts by B[a]PDE following reaction with 2'-deoxynucleotides.
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MESH Headings
- 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide/analysis
- 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide/chemistry
- 7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide/isolation & purification
- Carcinogens/chemistry
- Chromatography, High Pressure Liquid
- DNA Adducts/analysis
- DNA Adducts/chemistry
- DNA Adducts/isolation & purification
- Deoxyribonucleotides/chemistry
- Fluorescence
- Phosphates/chemistry
- Spectrometry, Mass, Electrospray Ionization/methods
- Tandem Mass Spectrometry
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Affiliation(s)
| | | | | | - Rajinder Singh
- *To whom correspondence should be addressed:+44 0 116 2231827 +44 0 116 2231840
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14
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Lee DH, Jin SG, Cai S, Chen Y, Pfeifer GP, O'Connor TR. Repair of methylation damage in DNA and RNA by mammalian AlkB homologues. J Biol Chem 2005; 280:39448-59. [PMID: 16174769 DOI: 10.1074/jbc.m509881200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human and Escherichia coli derivatives of AlkB enzymes remove methyl groups from 1-methyladenine and 3-methylcytosine in nucleic acids via an oxidative mechanism that releases the methyl group as formaldehyde. In this report, we demonstrate that the mouse homologues of the alpha-ketoglutarate Fe(II) oxygen-dependent enzymes mAbh2 and Abh3 have activities comparable to those of their human counterparts. The mAbh2 and mAbh3 release modified bases from both DNA and RNA. Comparison of the activities of the homogenous ABH2 and ABH3 enzymes demonstrate that these activities are shared by both sets of enzymes. An assay for the detection of alpha-ketoglutarate Fe(II) dioxygenase activity using an oligodeoxyribonucleotide with a unique modification shows activity for all four enzymes studied and a loss of activity for eight mutant proteins. Steady-state kinetics for removal of methyl groups from DNA substrates indicates that the reactions of the proteins are close to the diffusion limit. Moreover, mAbh2 or mAbh3 activity increases survival in a strain defective in alkB. The mRNAs of AHB2 and ABH3 are expressed most in testis for ABH2 and ABH3, whereas expression of the homologous mouse genes is different. The mAbh3 is strongly expressed in testis, whereas highest expression of mAbh2 is in heart. Other purified human AlkB homologue proteins ABH4, ABH6, and ABH7 do not manifest activity. The demonstration of mAbh2 and mAbh3 activities and their distributions provide data on these mammalian homologues of AlkB that can be used in animal studies.
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Affiliation(s)
- Dong-Hyun Lee
- Biology Division, Beckman Research Institute, City of Hope National Medical Center, Duarte, California 91010, USA
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15
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González-Beltrán F, Morales-Ramírez P. In vivo repair during G1 of DNA lesions eliciting sister chromatid exchanges induced by methylnitrosourea or ethylnitrosourea in BrdU substituted or unsubstituted DNA in murine salivary gland cells. Mutat Res 1999; 425:239-47. [PMID: 10216217 DOI: 10.1016/s0027-5107(99)00043-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The difference in efficiency of methylnitrosourea (MNU) and ethylnitrosourea (ENU) to induce SCE in early or late G1 was determined in synchronized murine salivary gland cells in vivo, as a measure of the capacity of this tissue to repair the lesions involved in SCE formation during G1. The repair during G1 was determined by treating the cells in early or late G1. Treatment was in the first cycle (G1 before incorporation of 5-bromodeoxyuridine (BrdU)) or in G1 of the second cycle (after a single round of BrdU incorporation). It was observed that 50% of the lesions induced by MNU that elicit SCE are repaired during G1. BrdU incorporation into DNA increases the sensitivity of the cell to SCE induction by MNU nearly 40%; however under this circumstance a slightly lower SCE frequency was observed in the cells exposed to MNU at early G1, indicating that during G1 only few lesions are repaired. The ENU-induced DNA-lesions involved in SCE production are nearly 100% persistent along G1; besides, a slight but significantly higher SCE frequency was observed in cells exposed at early G1, suggesting the formation of SCE-inducing lesions during G1. BrdU incorporation to DNA sensitizes the cell to SCE induction by ENU, increasing the SCE frequency to nearly to a 40%, although these additional lesions involved in SCE induction seem to be susceptible to repair during G1.
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Affiliation(s)
- F González-Beltrán
- Departamento de Genética Instituto Nacional de Investigaciones Nucleares, Mexico, D.F. Mexico
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16
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Sotomayor RE, Ehling UH, Sega GA. Differential sensitivities of spermatogonial and postspermatogonial cell stages of the mouse to induction of unscheduled DNA synthesis by ethyl- and methyl-nitrosourea,. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1520-6866(1999)19:5<339::aid-tcm4>3.0.co;2-o] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Wilson GL, Leiter EH. Streptozotocin interactions with pancreatic beta cells and the induction of insulin-dependent diabetes. Curr Top Microbiol Immunol 1990; 156:27-54. [PMID: 2143132 DOI: 10.1007/978-3-642-75239-1_3] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The MSZ diabetic male mouse represents one of the most useful tools available to researchers interested in analyzing the consequences of insulin dependent diabetes in male mice. In contrast to the high mortality induced by single high doses of SZ, protracted administration of smaller SZ dosages yields a more stable diabetic condition. Moreover, in insulitis prone strains such as BKs, the model allows "synchronization" of beta cell destruction such that the inflammatory events occur on a predictable timescale. The MSZ-diabetic mouse represents a diabetic condition in which the primary etiopathologic effect is produced by an environmental toxin, and not by a genetically programmed loss of tolerance to beta cell specific antigens. In this regard, etiopathogenesis in the MSZ model is quite distinct from that underlying autoimmune type I diabetes in humans, NOD mice, and BB rats, and it is probably not appropriate to refer to pathogenesis in the MSZ model as one of "autoimmune insulitis" as has sometimes been done. The fact that insulitis in the MSZ model may not be "autoimmune," but may actually be a normal response to either tissue damage or to beta cells that have been structurally modified by a chemical, makes the model of special interest. Clearly, there is no single cause of insulin dependent diabetes, with disease induction representing a genetic susceptibility interacting with environmental triggers, such as toxins in the diet (including nitrosamines and fungal metabolites) as well as pathogenic viruses. The MSZ model will continue to be actively investigated because of insights it will afford regarding the genetic bases for susceptibility and resistance to diabetogenic environmental toxins. The model will be of further value by contributing to knowledge of the complicated interactions between pancreatic islet cells, other endocrine cells, and leukocytes in maintenance of glucose homeostasis.
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Affiliation(s)
- G L Wilson
- Department of Structural and Cellular Biology University of South Alabama, Mobile 36688
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18
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Tisdale MJ. Antitumour imidazotetrazines--XVIII. Modification of the level of 5-methylcytosine in DNA by 3-substituted imidazotetrazinones. Biochem Pharmacol 1989; 38:1097-101. [PMID: 2706009 DOI: 10.1016/0006-2952(89)90254-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effect of 3-methyl(temozolomide) and 3-ethyl (CCRG 82019) substituted imidazotetrazinones on cytosine methylation has been studied in the human lymphoblastoid cell line GM892. There was a decrease in the 5-methylcytosine content of newly synthesized DNA in cells treated with the 3-methyl and a small increase in cells treated with the 3-ethyl analogue, which was maximal 4 days after drug treatment. There was a progressive decrease in nuclear DNA methyltransferase after treatment with temozolomide with complete inhibition at 11-12 hr after drug addition, followed by a re-establishment of enzyme levels towards control values. While the free drugs had no effect on DNA methyltransferase activity in vitro, DNA isolated from GM892 cells previously treated with temozolomide inhibited the transfer of methyl groups from S-adenosyl-L-methionine to M. lysodeiktious DNA. The maximum effect was observed at 6 hr after drug addition and was proportional to the concentration of temozolomide to which the cells had previously been exposed. These results suggest that temozolomide may induce a block in cellular replication as a result of an indirect inhibition of DNA methylation and cells which escape this block progress with hypomethylated DNA.
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Affiliation(s)
- M J Tisdale
- Pharmaceutical Sciences Institute, Aston University, Birmingham, U.K
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19
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Brent TP, Dolan ME, Fraenkel-Conrat H, Hall J, Karran P, Laval L, Margison GP, Montesano R, Pegg AE, Potter PM. Repair of O-alkylpyrimidines in mammalian cells: a present consensus. Proc Natl Acad Sci U S A 1988; 85:1759-62. [PMID: 3162305 PMCID: PMC279858 DOI: 10.1073/pnas.85.6.1759] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Enzymatic repair of the O-alkylpyrimidines (O2- and O4-alkylthymine, O2-alkylcytosine) and alkyl phosphotriesters has been studied in Escherichia coli, and the two proteins involved, a glycosylase (DNA-3-methyladenine glycosylase) and a methyltransferase (DNA-O6-methylguanine:protein-L-cysteine S-methyltransferase, EC 2.1.1.63), have been well characterized. In mammals or mammalian cells treated with carcinogenic alkylating agents, loss of these derivatives has been demonstrated repeatedly. Nevertheless, mammalian repair proteins that are analogous to those from E. coli do not detectably act on these alkyl derivatives. A variety of techniques has been used by many investigators in the United States and Europe, who conclude here that the mode of O-alkylpyrimidine and alkyl phosphotriester repair in mammalian cells differs from that in E. coli. New approaches and methods are needed to characterize these processes at the biochemical and molecular level.
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Affiliation(s)
- T P Brent
- St. Jude Children's Research Hospital, Memphis, TN 38101
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20
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Affiliation(s)
- A E Pegg
- Department of Physiology, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033
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21
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Swenson DH, Petzold GL, Harbach PR. The binding of 1-(2-hydroxyethyl)-1-nitrosourea to DNA in vitro and to DNA of thymus and marrow in C57BL mice in vivo. Cancer Lett 1986; 33:75-81. [PMID: 3768862 DOI: 10.1016/0304-3835(86)90103-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To investigate the hypothesis that the similarity of dose-response curves for induction of thymic lymphoma in C57BL mice was due to similar DNA alkylation profiles for 1-ethyl-1-nitrosourea (ENU) and 1-(2-hydroxyethyl)-1-nitrosourea (HNU), we measured the reaction of the two agents with DNA in vitro and in target tissues in vivo. At equimolar doses, alkylation of DNA by HNU was about 20% greater than that by ENU in vitro. As a percentage of total DNA-bound alkyl groups, relative reaction at a minor groove site (3 of adenine) was similar for the two agents, but HNU caused greater relative alkylation at the major groove sites, O6 and N-7 of guanine. At equi-oncogenic doses, alkylation at the O6 of guanine in liver and thymus was similar for both agents, but O6-alkylguanine formation in bone marrow by HNU was almost twice that by ENU. Because alkylation at O6 of guanine has previously been shown to be a key procarcinogenic lesion in this system, these findings suggest the thymus, rather than the marrow as a primary target for tumor induction by these agents, although involvement of marrow alkylation cannot be ruled out.
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22
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Singer B. In vivo formation and persistence of modified nucleosides resulting from alkylating agents. ENVIRONMENTAL HEALTH PERSPECTIVES 1985; 62:41-8. [PMID: 4085444 PMCID: PMC1568687 DOI: 10.1289/ehp.856241] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Alkylating agents are ubiquitous in the human environment and are continuously synthesized in vivo. Although many classes exist, interest has been focused on the N-nitroso compounds, since many are mutagens for bacteria, phage, and cells, and carcinogens for mammals. In contrast to aromatic amines and polyaromatic hydrocarbons which can react at carbons, simple alkylating agents react with nitrogens and oxygens: 13 sites are possible, including the internucleotide phosphodiester. However, only the N-nitroso compounds react extensively with oxygens. In vivo, most possible derivatives have been found after administration of methyl and ethyl nitroso compounds. The ethylating agents are more reactive toward oxygens than are the methylating agents and are more carcinogenic in terms of total alkylation. This is true regardless of whether or not the compounds require metabolic activation. It has been hypothesized that the level and persistence of specific derivatives in a "target" cell correlates with oncogenesis. However, no single derivative can be solely responsible for this complex process, since correlations cannot be made for even a single carcinogen acting on various species or cell types. Some derivatives are chemically unstable, and the glycosyl bond is broken (3- and 7-alkylpurines), leaving apurinic sites which may be mutagenic. These, as well as most adducts, are recognized by different enzymatic activities which remove/repair at various rates and efficiencies depending on the number of alkyl derivatives, as well as enzyme content in the cell and recognition of the enzyme. Evaluation of human exposure requires early and sensitive methods to detect the initial damage and the extent of repair of each of the many promutagenic adducts.
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23
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McCarthy TV, Lindahl T. Methyl phosphotriesters in alkylated DNA are repaired by the Ada regulatory protein of E. coli. Nucleic Acids Res 1985; 13:2683-98. [PMID: 2987862 PMCID: PMC341187 DOI: 10.1093/nar/13.8.2683] [Citation(s) in RCA: 116] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The E. coli ada+ gene product that controls the adaptive response to alkylating agents has been purified to apparent homogeneity using an overproducing expression vector system. This 39 kDa protein repairs 0(6)-methylguanine and 0(4)-methylthymine residues in alkylated DNA by transfer of the methyl group from the base to a cysteine residue in the protein itself. The Ada protein also corrects one of the stereoisomers of methyl phosphotriesters in DNA by the same mechanism, while the other isomer is left unrepaired. Different cysteine residues in the Ada protein are used as acceptors in the repair of methyl groups derived from phosphotriesters and base residues.
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24
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Yarosh DB. The role of O6-methylguanine-DNA methyltransferase in cell survival, mutagenesis and carcinogenesis. Mutat Res 1985; 145:1-16. [PMID: 3883145 DOI: 10.1016/0167-8817(85)90034-3] [Citation(s) in RCA: 119] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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25
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Jirakulsomchok S, Yielding KL. DNA damage and repair in mouse embryos following treatment transplacentally with methylnitrosourea and methylmethanesulfonate. TERATOGENESIS, CARCINOGENESIS, AND MUTAGENESIS 1984; 4:523-36. [PMID: 6151263 DOI: 10.1002/tcm.1770040607] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Mouse embryos were labeled in vivo at 10 1/2-12 1/2 days of gestation with [3H]-thymidine and subjected to DNA damage using x-ray, methylmethanesulfonate, or methylnitrosourea. DNA damage and its repair were assessed in specific cell preparations from embryos isolated at intervals thereafter using the highly sensitive method of nucleoid sedimentation, which evaluates the supercoiled state of the DNA. Repair of x-ray damage was demonstrated using trypsin-dispersed cells from whole embryos and from homogenized embryonic liver to show the validity of the analytical approach. The effects of the highly teratogenic methylnitrosourea and the much less teratogenic methylmethanesulfonate were compared in the targeted limb buds using equitoxic doses of the two alkylating agents. DNA supercoiling was fully restored after 24 hr in limb bud cells damaged with methylmethanesulfonate, while as much as 48 hr were required for full repair of methylnitrosourea damage. These results demonstrated the feasibility of studying DNA repair in embryonic tissues after damage in vivo and suggest that the potency of methylnitrosourea as a teratogen may be correlated with a prolonged period required for complete repair of DNA.
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Klaude M, von der Decken A. Non-random effect on RNA synthesis in liver chromatin by administration of dimethylnitrosamine to mice. Arch Toxicol 1983; 54:215-25. [PMID: 6197951 DOI: 10.1007/bf01239205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effect of dimethylnitrosamine on functional activities of liver chromatin was studied in mice. After a single dose of dimethylnitrosamine injected i.v. (25 mg/kg body wt, 45 min before sacrifice) liver nuclei were isolated and incubated with micrococcal nuclease (EC 3.1.4.7) to an acid-solubility of 2.5% of total DNA. Chromatin was fractionated into a 1,200 g pellet P1, 102,000 g pellet P2 and supernatant fraction S2. Chromatin-bound RNA polymerase I plus III activity decreased 15% in the P1 and 25% in the P2 fraction. No changes in activity were observed in the S2 fraction. Chromatin-bound RNA polymerase II activity decreased 19% in the P1, 49% in the P2 and 32% in the S2 fraction. Heparin stimulated RNA polymerase II activity decreased 10% in the P1 and 44% in the P2 fraction. Formation of initiation in nuclear lysates with RNA polymerase from Escherichia coli increased after administration of dimethylnitrosamine suggesting an increase in the number of sites available for the start of new RNA chains. The results show that limited digestion of nuclei with endonuclease cleaves chromatin regions which are more affected by dimethylnitrosamine than the total chromatin suggesting a non-random effect of the hepatotoxin on chromatin. Modifications of the DNA template by dimethylnitrosamine is indicated by the change in number of initiation complexes.
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27
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Singer B. Mutagenic effects of nucleic acid modification and repair assessed by in vitro transcription. BASIC LIFE SCIENCES 1983; 23:1-34. [PMID: 6340655 DOI: 10.1007/978-1-4684-4382-0_1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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28
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Abbondandolo A, Dogliotti E, Lohman PH, Berends F. Molecular dosimetry of DNA damage caused by alkylation. I. Single-strand breaks induced by ethylating agents in cultured mammalian cells in relation to survival. Mutat Res 1982; 92:361-77. [PMID: 7201070 DOI: 10.1016/0027-5107(82)90236-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Cultured Chinese hamster ovary cells were treated with ethylating agents. DNA lesions giving rise to single-strand breaks (ssb) or alkali-labile sites were measured by centrifugation in alkaline sucrose gradients after lysis in alkali. 4 agents with different tendencies to ethylate preferentially either at N or O atoms were compared, namely N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), N-ethyl-N-nitrosourea (ENU), ethyl methanesulphonate (EMS) and diethyl sulphonate (DES). The compounds differed greatly in their potency to induce the lesions measured when compared on a molar basis, but comparison at equicytotoxic doses showed relatively small differences. Upon prolonged incubation of the DNA in alkali, the number of ssb increased considerably. DNA from untreated cells showed biphasic kinetics: slow ssb formation for about 10 h, then the rate increased and remained constant for up to 40 h. Treated cells showed an accelerated, dose-dependent linear generation of ssb for 10 h, followed by a short plateau; then ssb were formed again at a constant rate, somewhat higher than that in controls. Ssb formed in the initial phase are ascribed to phosphotriester hydrolysis, those after the plateau to unidentified causes. Zero intercepts appeared to be a measure of apurinic sites generated intracellularly. A 24-h repair period preceding lysis reduced the ENNG intercept, but not that of DES. Rapid degradation of DES during the 1-h treatment occurred, so most "apurinic-site lesions" were induced in the beginning of exposure and possibly were already repaired at the end. The types of lesion distinguished (reparable and non-reparable apurinic sites, phosphotriesters) appeared of little consequence for cell survival.
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Singer B. Mutagenesis from a chemical perspective: nucleic acid reactions, repair, translation, and transcription. BASIC LIFE SCIENCES 1982; 20:1-42. [PMID: 6180726 DOI: 10.1007/978-1-4613-3476-7_1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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30
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Snyder RD, Regan JD. Quantitative estimation of the extent of alkylation of DNA following treatment of mammalian cells with non-radioactive alkylating agents. Mutat Res 1981; 91:307-14. [PMID: 7266573 DOI: 10.1016/0165-7992(81)90006-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Alkaline sucrose sedimentation has been used to quantitate phosphotriester formation following treatment of human cells with the monofunctional alkylating agents methyl and ethyl methanesulfonate. These persistent alkaline-labile lesions are not repaired during short-term culture conditions and thus serve as a useful and precise index of the total alkylation of the DNA. Estimates of alkylation by this procedure compare favorably with direct estimates by use of labeled alkylating agents.
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Shooter KV, Merrifield RK. Analysis of mammalian DNA for the presence of carcinogen-induced phosphotriesters: application of the technique of difference sedimentation. Anal Biochem 1980; 103:110-7. [PMID: 7377536 DOI: 10.1016/0003-2697(80)90244-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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32
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Lutz WK. In vivo covalent binding of organic chemicals to DNA as a quantitative indicator in the process of chemical carcinogenesis. Mutat Res 1979; 65:289-356. [PMID: 390383 DOI: 10.1016/0165-1110(79)90006-x] [Citation(s) in RCA: 340] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The covalent binding of chemical carcinogens to DNA of mammalian organs is expressed per unit dose, and a 'Covalent-Binding Index', CBI, is defined. CBI for various carcinogens span over 6 orders of magnitude. A similar range is observed for the carcinogenic potency in long-term bioassays on carcinogenicity. For the assessment of a risk from exposure to a carcinogen, the total DNA dmaage can be estimated if the actual dose is also accounted for. A detailed description is given for planning and performing a DNA-binding assay. A complete literature survey on DNA binding in vivo (83 compounds) is given with a calculation of CBI, where possible, 153 compounds are listed where a covalent binding to any biological macromolecule has been shown in vivo or in vitro. Recent, so far unpublished findings with aflatoxin M1, macromolecule-bound aflatoxin B1, diethylstilbestrol, and 1,2-epithiobutyronitrile are included. A comparison of CBI for rat-liver DNA with hepatocarcinogenic potency reveals a surprisingly good quantitative correlation. Refinements for a DNA-binding assay are proposed. Possibilites and limitations in the use of DNA binding in chemical carcinogenesis are discussed extensively.
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33
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Warren W, Crathorn AR, Shooter KV. The stability of methylated purines and of methylphosphotriesters in the DNA of V79 cells after treatment with N-methyl-N-nitrosourea. BIOCHIMICA ET BIOPHYSICA ACTA 1979; 563:82-8. [PMID: 497216 DOI: 10.1016/0005-2787(79)90009-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
V79-379A cells growing in suspension culture were treated with N-methyl-N-nitrosourea at concentrations of 0.6 and 1.2 mM. After incubation for periods from 1 to 48 h DNA was isolated from the cells and the concentrations of 7-methylguanine, O6-methylguanine, 3-methyladenine and methyl phosphotriesters were determined. After correction for dilution resulting from DNA synthesis during the incubation it was found that no loss of O6-methylguanine or methylphosphotriesters occurred; 7-methylguanine disappeared with a half-life of 22 h and 3-methyladenine was detectable only immediately after the initial treatment. The results show that these cells eliminate 7-methylguanine and 3-methyladenine from DNA by a repair process but are unable to excise or repair O6-methylguanine or methyl phosphotriesters.
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Floot BG, Philippus EJ, Hart AA, Den Engelse L. Persistence and accumulation of (potential) single strand breaks in liver DNA of rats treated with diethylnitrosamine or dimethylnitrosamine: correlation with hepatocarcinogenicity. Chem Biol Interact 1979; 25:229-42. [PMID: 466734 DOI: 10.1016/0009-2797(79)90048-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Effects of diethylnitrosamine (DEN) and dimethylnitrosamine (DMN) on the sedimentation pattern of [3H]thymidine-labelled Sprague-Dawley female rat liver DNA in alkaline sucrose gradients were studied with regard to time and dose dependency. In experiments at 1--56 days after a single injection it was observed that (potential) single strand breaks induced by DEN were repaired at a low rate. At 56 days the sedimentation pattern was still grossly abnormal. Half-life values of 27 and 46 days were observed after 134 mg/kg DEN (approx. 45% of the LD50) and 13.4 mg/kg DEN, respectively. Identical experiments after DMN (10 mg/kg, corresponding to about 35% of the LD50) showed return to (almost) completely control sedimentation patterns within 56 days after injection (t 1/2 = 8 days). Experiments at 6 or 56 days after the last of a series of 5 or 10 weekly injections of DEN (13.4 mg/kg) showed that a major part of DEN-induced damage (measured as single strand breaks) is of a persistent and accumulating character. No accumulation of DMN-induced rat liver lesions was observed. It is concluded that DNA fragmentation and lack of DNA repair is not a consequence of hepatotoxicity. Since at equimolar doses DEN gives appreciably less DNA alkylation (including O6-alkylguanine) but is much more effective both as an inducer of preneoplastic liver lesions and as a hepatocarcinogen when compared with DMN, we believe that the formation of persistent (and accumulating) DNA damage after DEN administration might be relevant in the process of liver tumour formation.
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Lindahl T. DNA glycosylases, endonucleases for apurinic/apyrimidinic sites, and base excision-repair. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1979; 22:135-92. [PMID: 392601 DOI: 10.1016/s0079-6603(08)60800-4] [Citation(s) in RCA: 378] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Shooter KV, Merrifield RK. The rate of hydrolysis of methyl phosphotriesters in DNA under conditions used in alkaline sucrose gradients. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 521:155-9. [PMID: 718925 DOI: 10.1016/0005-2787(78)90258-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Methyl phosphotriesters have been introduced into DNA, in vitro, by reaction with N-methyl-N-nitrosourea and the rate of degradation in alkali has been followed by measurements of the mean sedimentation coefficient using an analytical ultracentrifuge. In 0.3 M NaOH/0.7 M NaCl, a solution commonly used in alkaline sucrose gradient experiments, hydrolysis of the methyl phosphotriesters present is complete after 15 h at 20 degrees C, or after 2--3 h at 37 degrees C. In addition to breaks formed by the latter reaction there was a continuous background degradation of the DNA giving rise to 6.3 and 63 breaks/10(6) nucleotides per h at 20 degrees and 37 degrees C, respectively. The problem of obtaining quantitative data on phosphotriester concentrations from results of alkaline sucrose gradient experiments has been discussed.
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Frei JV, Swenson DH, Warren W, Lawley PD. Alkylation of deoxyribonucleic acid in vivo in various organs of C57BL mice by the carcinogens N-methyl-N-nitrosourea, N-ethyl-N-nitrosourea and ethyl methanesulphonate in relation to induction of thymic lymphoma. Some applications of high-pressure liquid chromatography. Biochem J 1978; 174:1031-44. [PMID: 728073 PMCID: PMC1186009 DOI: 10.1042/bj1741031] [Citation(s) in RCA: 151] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
1. Methods were developed for analysis of alkylpurines, O2-alkylcytosines, and representative phosphotriesters [alkyl derivatives of thymidylyl(3'-5')thymidine], in DNA alkylated in vivo, using high-pressure liquid chromatography. 2. The patterns of alkylation products in DNA in vivo at short times were closely similar to those found for reactions in vitro. Alkylation by the nitrosoureas was complete in vivo within 1 h, but with ethyl methanesulphonate was maximal at 2--4h. 3. The time course of persistence of alkylation products in vivo was determined for several tissues. In addition to the rapid loss of 3- and 7-alkyladenines reported previously for all tissues, a relatively rapid loss of O6-alkylguanines from DNA of liver was found which was more rapid at lower doses. In brain, lung and kidney, excision of O6-alkylguanine was much less marked, but was not entirely excluded by the data. In thymus, bone marrow and small bowel, all alkylated bases were lost with half-lives of 12--24h, at non-cytotoxic doses of alkylation. 4. No evidence for any marked excision of other minor products from alkylated DNA in vivo was found; thus 1-methyladenine, O2-ethylcytosine (found in appreciable amount only with N-ethyl-N-nitrosourea), 3-methylguanine, and dTp(Alk)dT persisted in alkylated DNA, including DNA of liver. 5. The induction of thymic lymphoma was determined over the range of single doses by intraperitoneal injection up to about 60% of the LD50 values, and related to the extent of alkylation of target tissues thymus and bone marrow. With N-methyl-N-nitrosourea over 90% tumour yield was attained at 60 mg/kg, and with N-ethyl-N-nitrosourea up to 52% at 240 mg/kg, but with ethyl methanesulphonate at up to 400 mg/kg only a few per cent of tumours were obtained. 6. The carcinogenic effectiveness of the agents was positively correlated with the extents of alkylation of guanine in DNA of target tissues at the O-6 atom. On the basis that at doses giving equal carcinogenic response these extents of alkylation would be equal, the chemical analyses showed that the ratio of equipotent doses to that for N-methyl-N-nitrosourea would be, for N-ethyl-N-nitrosourea, 5.3 for ethyl methanesulphonate about 21, and for methyl methanesulphonate [Frei & Lawley (1976) Chem.-Biol. Interact. 13, 215--222] about 144. These predictions were in reasonably good agreement with the observed dose-response data for these agents.
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