1
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Adjei D, Reyes Y, Kumar A, Ward S, Denisov SA, Alahmadi M, Sevilla MD, Wnuk SF, Mostafavi M, Adhikary A. Pathways of the Dissociative Electron Attachment Observed in 5- and 6-Azidomethyluracil Nucleosides: Nitrogen (N 2) Elimination vs Azide Anion (N 3-) Elimination. J Phys Chem B 2023; 127:1563-1571. [PMID: 36780335 PMCID: PMC9984991 DOI: 10.1021/acs.jpcb.2c08257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
5-Azidomethyl-2'-deoxyuridine (5-AmdU, 1) has been successfully employed for the metabolic labeling of DNA and fluorescent imaging of live cells. 5-AmdU also demonstrated significant radiosensitization in breast cancer cells via site-specific nitrogen-centered radical (π-aminyl (U-5-CH2-NH•), 2, and σ-iminyl (U-5-CH═N•), 3) formation. This work shows that these nitrogen-centered radicals are not formed via the reduction of the azido group in 6-azidomethyluridine (6-AmU, 4). Radical assignments were performed using electron spin resonance (ESR) in supercooled solutions, pulse radiolysis in aqueous solutions, and theoretical (DFT) calculations. Radiation-produced electron addition to 4 leads to the facile N3- loss, forming a stable neutral C-centered allylic radical (U-6-CH2•, 5) through dissociative electron attachment (DEA) via the transient negative ion, TNI (U-6-CH2-N3•-), in agreement with DFT calculations. In contrast, TNI (U-5-CH2-N3•-) of 1, via facile N2 loss (DEA) and protonation from the surrounding water, forms radical 2. Subsequently, 2 undergoes rapid H-atom abstraction from 1 and produces the metastable intermediate α-azidoalkyl radical (U-5-CH•-N3). U-5-CH•-N3 converts facilely to radical 3. N3- loss from U-6-CH2-N3•- is thermodynamically controlled, whereas N2 loss from U-5-CH2-N3•- is dictated by protonation from the surrounding waters and resonance conjugation of the azidomethyl side chain at C5 with the pyrimidine ring.
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Affiliation(s)
- Daniel Adjei
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Yahaira Reyes
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA
| | - Anil Kumar
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Samuel Ward
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Sergey A. Denisov
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Moaadh Alahmadi
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Michael D. Sevilla
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
| | - Stanislaw F. Wnuk
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA
| | - Mehran Mostafavi
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Amitava Adhikary
- Department of Chemistry, 146 Library Drive, Oakland University, Rochester, Michigan 48309, USA
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2
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Zdrowowicz M, Datta M, Rychłowski M, Rak J. Radiosensitization of PC3 Prostate Cancer Cells by 5-Thiocyanato-2'-deoxyuridine. Cancers (Basel) 2022; 14:cancers14082035. [PMID: 35454941 PMCID: PMC9025292 DOI: 10.3390/cancers14082035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 04/14/2022] [Accepted: 04/15/2022] [Indexed: 11/23/2022] Open
Abstract
Simple Summary Radiation therapy is one of the main treatments for cancer. However, the success of treatment by radiation therapy is largely dependent on tumor radiosensitivity. To improve therapeutic outcomes, radiation therapy should be combined with the use of a radiosensitizer which enables irradiation at lower doses with higher efficacies. 5-Thiocyanato-2′-deoxyuridine has been reported as a potential radiosensitizer of DNA damage based on advanced radiation chemical studies. In this paper, for the first time, we demonstrate the radiosensitizing properties of this modified nucleoside at the cellular level. The tested analogue increases the sensitivity of prostate cancer cells to ionizing radiation which is, at least partially, related to an increase in the number of DNA double-strand breaks and cell cycle regulation. Abstract Purpose: The radiosensitizing properties of uracil analogs modified in the C5 position are very interesting in the context of their effectiveness and safety in radiation therapy. Recently, radiation chemical studies have confirmed that 5-thiocyanato-2′-deoxyuridine (SCNdU) undergoes dissociation induced by an excess electron attachment and established this nucleoside as a potential radiosensitizer. In this paper, we verify the sensitizing properties of SCNdU at the cellular level and prove that it can effectively enhance ionizing radiation-induced cellular death. Methods and Materials: Prostate cancer cells were treated with SCNdU and irradiated with X rays. The cytotoxicity of SCNdU was determined by MTT test. Cell proliferation was assessed using a clonogenic assay. Cell cycle analyses, DNA damage, and cell death analyses were performed by flow cytometry. Results: SCNdU treatment significantly suppressed the proliferation and increased the radiosensitivity of prostate cancer cells. The radiosensitizing effect expressed by the dose enhancement factor is equal to 1.69. Simultaneous exposure of cells to SCNdU and radiation causes an increase in the fraction of the most radiosensitive G2/M phase, enhancement of the histone H2A.X phosphorylation level, and apoptosis induction. Finally, SCNdU turned out to be marginally cytotoxic in the absence of ionizing radiation. Conclusions: Our findings indicate that SCNdU treatment enhances the radiosensitivity of prostate cancer cells in a manner associated with the cell cycle regulation, double strand formation, and a slight induction of apoptosis.
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Affiliation(s)
- Magdalena Zdrowowicz
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (M.D.); (J.R.)
- Correspondence:
| | - Magdalena Datta
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (M.D.); (J.R.)
| | - Michał Rychłowski
- Laboratory of Virus Molecular Biology, Intercollegiate Faculty of Biotechnology of University of Gdańsk and Medical University of Gdańsk, Abrahama 58, 80-307 Gdańsk, Poland;
| | - Janusz Rak
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (M.D.); (J.R.)
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3
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Ma J, Bahry T, Denisov SA, Adhikary A, Mostafavi M. Quasi-Free Electron-Mediated Radiation Sensitization by C5-Halopyrimidines. J Phys Chem A 2021; 125:7967-7975. [PMID: 34470211 PMCID: PMC8448956 DOI: 10.1021/acs.jpca.1c05974] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Substitution of the thymidine moiety in DNA by C5-substituted halogenated thymidine analogues causes significant augmentation of radiation damage in living cells. However, the molecular pathway involved in such radiosensitization process has not been clearly elucidated to date in solution at room temperature. So far, low-energy electrons (LEEs; 0-20 eV) under vacuum condition and solvated electrons (esol-) in solution are shown to produce the σ-type C5-centered pyrimidine base radical through dissociative electron attachment involving carbon-halogen bond breakage. Formation of this σ-type radical and its subsequent reactions are proposed to cause cellular radiosensitization. Here, we report time-resolved measurements at room temperature, showing that a radiation-produced quasi-free electron (eqf-) in solution promptly breaks the C5-halogen bond in halopyrimidines forming the σ-type C5 radical via an excited transient anion radical. These results demonstrate the importance of ultrafast reactions of eqf-, which are extremely important in chemistry, physics, and biology, including tumor radiochemotherapy.
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Affiliation(s)
- Jun Ma
- Department of Nuclear Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, P. R. China
| | - Teseer Bahry
- Department of Nuclear Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, P. R. China
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Sergey A. Denisov
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
| | - Amitava Adhikary
- Department of Chemistry, Oakland University, 146 Library Drive, Rochester, MI - 48309, United States
| | - Mehran Mostafavi
- Institut de Chimie Physique, UMR 8000 CNRS, Bât. 349, Université Paris-Saclay; 91405, Orsay, Cedex, France
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4
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Cruz-Vallejo V, Ortíz-Muñiz R, Vallarino-Kelly T, Cervantes-Ríos E, Morales-Ramírez P. In vivo Characterization of the Radiosensitizing Effect of a Very Low Dose of BrdU in Murine Cells Exposed to Low-Dose Radiation. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2019; 60:534-545. [PMID: 30851126 DOI: 10.1002/em.22284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 02/24/2019] [Accepted: 03/02/2019] [Indexed: 06/09/2023]
Abstract
The aim of the present study was to characterize the in vivo radiosensitizing effect of a very low dose of bromodeoxyuridine (BrdU) in mice exposed to low-dose radiation by establishing the following: (1) the radiosensitizing effect during DNA synthesis using single-cell gel electrophoresis (SCGE) in murine bone marrow cells, and (2) the number and timing of the mechanisms of genotoxicity and cytotoxicity, as well as the correlation of both end points, using flow cytometry analysis of the kinetics of micronucleus induction in reticulocytes. Groups of mice received intraperitoneal injections of 0.125 mg/g of BrdU 24 h prior to irradiation with 0.5 Gy of 60 Co gamma rays. DNA breaks measured using SCGE were determined at 30 min after exposure to radiation. The kinetics of micronucleated reticulocyte (MN-RET) induction was determined every 8 h after irradiation up to 72 h. The results from both experimental models indicated that low-level BrdU incorporation into DNA increased the sensitivity to 0.5 Gy of radiation, particularly in the S phase. The formation of micronuclei by gamma rays was produced at three different times using two main mechanisms. In the BrdU-substituted cells, the second mechanism was associated with a high cytotoxic effect that was absent in the irradiated BrdU-unsubstituted cells. The third mechanism, in which micronucleus formation was increased in irradiated substituted cells compared with the irradiated nonsubstituted control cells, was also related to an increase in cytotoxicity. Environ. Mol. Mutagen. 60:534-545, 2019. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Virginia Cruz-Vallejo
- Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, La Marquesa, Ocoyoacac, Estado de México C. P., 52750, Mexico
- Doctorado en Biología Experimental, Universidad Autónoma Metropolitana, Avenida San Rafael Atlixco 186 CP, 09340, Ciudad de México, Mexico
| | - Rocío Ortíz-Muñiz
- Departamento de Ciencias de la Salud, Universidad Autónoma Metropolitana-Iztapalapa, Avenida San Rafael Atlixco 186 CP, 09340, Ciudad de México, Mexico
| | - Teresita Vallarino-Kelly
- Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, La Marquesa, Ocoyoacac, Estado de México C. P., 52750, Mexico
| | - Elsa Cervantes-Ríos
- Departamento de Ciencias de la Salud, Universidad Autónoma Metropolitana-Iztapalapa, Avenida San Rafael Atlixco 186 CP, 09340, Ciudad de México, Mexico
| | - Pedro Morales-Ramírez
- Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, La Marquesa, Ocoyoacac, Estado de México C. P., 52750, Mexico
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5
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Meißner R, Makurat S, Kozak W, Limão-Vieira P, Rak J, Denifl S. Electron-Induced Dissociation of the Potential Radiosensitizer 5-Selenocyanato-2'-deoxyuridine. J Phys Chem B 2019; 123:1274-1282. [PMID: 30657689 DOI: 10.1021/acs.jpcb.8b11523] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
5-Selenocyanato-2'-deoxyuridine (SeCNdU) is a recently proposed radiosensitizer based on 2'-deoxyuridine (dU) with the electron-affinic selenocyanato (-SeCN) side group attached at the C5 position of uracil. Since electron interaction processes may be an important source of DNA damage by ionizing radiation, we have studied low-energy dissociative electron attachment to SeCNdU in the gas phase. Negative ion formation has been obtained by means of mass spectrometry, where a rich fragmentation pattern is observed even at ∼0 eV. The reaction pathways exhibiting the highest ion yields are C4N2O2H2Se•- and CN-, both involving a cleavage of the Se-CN bond. The heaviest fragment anion observed is C9N2O5H10Se•-, where besides the charged species, the hydrogen and cyano radicals are also formed. Further decomposition channels also yield the highly reactive hydroxyl radical, which possesses a high DNA damage potential. All observed channels have experimentally determined onsets at 0 eV, which are supported by calculations performed at the M06-2X/aug-cc-pVTZ level. The calculations comprise the thermochemical thresholds at standard and experimental (428.15 K, 3 × 10-11 atm) conditions together with the adiabatic electron affinities. The present study shows that low-energy electrons very effectively decompose SeCNdU upon attachment of thermal electrons, producing a large variety of charged fragments and radicals.
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Affiliation(s)
- Rebecca Meißner
- Institut für Ionenphysik und Angewandte Physik and Center for Biomolecular Sciences Innsbruck , Leopold-Franzens Universität Innsbruck , Technikerstrasse 25 , A-6020 Innsbruck , Austria.,Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics , Universidade NOVA de Lisboa , 2829-516 Caparica , Portugal
| | - Samanta Makurat
- Laboratory of Biological Sensitizers, Physical Chemistry Department, Faculty of Chemistry , University of Gdańsk , 80-308 Gdańsk , Poland
| | - Witold Kozak
- Laboratory of Biological Sensitizers, Physical Chemistry Department, Faculty of Chemistry , University of Gdańsk , 80-308 Gdańsk , Poland
| | - Paulo Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics , Universidade NOVA de Lisboa , 2829-516 Caparica , Portugal
| | - Janusz Rak
- Laboratory of Biological Sensitizers, Physical Chemistry Department, Faculty of Chemistry , University of Gdańsk , 80-308 Gdańsk , Poland
| | - Stephan Denifl
- Institut für Ionenphysik und Angewandte Physik and Center for Biomolecular Sciences Innsbruck , Leopold-Franzens Universität Innsbruck , Technikerstrasse 25 , A-6020 Innsbruck , Austria
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6
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Tauraitė D, Jakubovska J, Dabužinskaitė J, Bratchikov M, Meškys R. Modified Nucleotides as Substrates of Terminal Deoxynucleotidyl Transferase. Molecules 2017; 22:molecules22040672. [PMID: 28441732 PMCID: PMC6154577 DOI: 10.3390/molecules22040672] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Revised: 04/10/2017] [Accepted: 04/19/2017] [Indexed: 11/30/2022] Open
Abstract
The synthesis of novel modified nucleotides and their incorporation into DNA sequences opens many possibilities to change the chemical properties of oligonucleotides (ONs), and, therefore, broaden the field of practical applications of modified DNA. The chemical synthesis of nucleotide derivatives, including ones bearing thio-, hydrazino-, cyano- and carboxy groups as well as 2-pyridone nucleobase-containing nucleotides was carried out. The prepared compounds were tested as substrates of terminal deoxynucleotidyl transferase (TdT). The nucleotides containing N4-aminocytosine, 4-thiouracil as well as 2-pyridone, 4-chloro- and 4-bromo-2-pyridone as a nucleobase were accepted by TdT, thus allowing enzymatic synthesis of 3’-terminally modified ONs. The successful UV-induced cross-linking of 4-thiouracil-containing ONs to TdT was carried out. Enzymatic post-synthetic 3’-modification of ONs with various photo- and chemically-reactive groups opens novel possibilities for future applications, especially in analysis of the mechanisms of polymerases and the development of photo-labels, sensors, and self-assembling structures.
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Affiliation(s)
- Daiva Tauraitė
- Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Life Sciences Center, Vilnius University, Sauletekio al. 7, Vilnius LT-10257, Lithuania.
| | - Jevgenija Jakubovska
- Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Life Sciences Center, Vilnius University, Sauletekio al. 7, Vilnius LT-10257, Lithuania.
| | - Julija Dabužinskaitė
- Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Life Sciences Center, Vilnius University, Sauletekio al. 7, Vilnius LT-10257, Lithuania.
| | - Maksim Bratchikov
- Department of Physiology, Biochemistry, Microbiology and Laboratory Medicine, Faculty of Medicine, Vilnius University, M. K. Čiurlionio g. 21, Vilnius LT-03101, Lithuania.
| | - Rolandas Meškys
- Department of Molecular Microbiology and Biotechnology, Institute of Biochemistry, Life Sciences Center, Vilnius University, Sauletekio al. 7, Vilnius LT-10257, Lithuania.
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7
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Rudra A, Hou D, Zhang Y, Coulter J, Zhou H, DeWeese TL, Greenberg MM. Bromopyridone Nucleotide Analogues, Anoxic Selective Radiosensitizing Agents That Are Incorporated in DNA by Polymerases. J Org Chem 2015; 80:10675-85. [PMID: 26509218 DOI: 10.1021/acs.joc.5b01833] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Ionizing radiation is frequently used to kill tumor cells. However, hypoxic solid tumor cells are more resistant to this treatment, providing the impetus to develop molecules that sensitize cells to ionizing radiation. 5-Bromo-2'-deoxyuridine (BrdU) has been investigated as a radiosensitizing agent in the lab and clinic for almost 5 decades. Recent reports that BrdU yields DNA interstrand cross-links (ICLs) in non-base-paired regions motivated us to develop radiosensitizing agents that generate cross-links in duplex DNA selectively under anoxic conditions. 4-Bromo- and 5-bromopyridone analogues of BrdU were synthesized and incorporated into oligonucleotides via solid-phase synthesis. Upon irradiation, these molecules yield DNA interstrand cross-links under anaerobic conditions. The respective nucleotide triphosphates are substrates for some DNA polymerases. ICLs are produced upon irradiation under anoxic conditions when the 4-bromopyridone is present in a PCR product. Because the nucleoside analogue is a poor phosphorylation substrate for human deoxycytidine kinase, a pro-nucleotide form of the 4-bromopyridone was used to incorporate this analogue into cellular DNA. Despite these efforts, the 4-bromopyridone nucleotide was not detected in cellular DNA. Although these molecules are improvements over previously reported nucleotide analogues designed to be hypoxic radiosensitizing agents, additional advances are needed to create molecules that function in cells.
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Affiliation(s)
- Arnab Rudra
- Department of Chemistry, Johns Hopkins University , 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Dianjie Hou
- Department of Chemistry, Johns Hopkins University , 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Yonggang Zhang
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine , 401 N. Broadway, Baltimore, Maryland 21231, United States.,Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine , Baltimore, Maryland 21231, United States
| | - Jonathan Coulter
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine , 401 N. Broadway, Baltimore, Maryland 21231, United States
| | - Haoming Zhou
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine , 401 N. Broadway, Baltimore, Maryland 21231, United States
| | - Theodore L DeWeese
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine , 401 N. Broadway, Baltimore, Maryland 21231, United States.,Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine , Baltimore, Maryland 21231, United States
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University , 3400 N. Charles Street, Baltimore, Maryland 21218, United States
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Li F, Cheng Y, Iliakis G. The contribution of thermally labile sugar lesions to DNA double-strand break formation in cells grown in the presence of BrdU. Int J Radiat Biol 2015; 91:312-20. [PMID: 25510257 DOI: 10.3109/09553002.2014.996260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Radiosensitization by bromodeoxyuridine (BrdU) is commonly attributed to an increase in the yield of double-strand breaks (DSB) in the DNA and an associated decrease in the reparability of these lesions. Radiation chemistry provides a mechanism for the increased yield of DSB through the generation, after bromine loss, of a highly reactive uracilyl radical that attacks the sugar moiety of the nucleotide to produce a single-strand break (SSB). The effects underpinning DSB repair inhibition remain, in contrast, incompletely characterized. A possible source of reduced reparability is a change in the nature or complexity of the DSB in BrdU-substituted DNA. Recent studies show that DSB-complexity or DSB-nature may also be affected by the presence within the cluster of thermally labile sugar lesions (TLSL) that break the DNA backbone only if they chemically evolve to SSB, a process thought to occur within the first hour post-irradiation. Since BrdU radiosensitization might be associated with increased yields and reduced reparability of DSB, we investigated whether BrdU underpins these effects by shifting the balance in the generation of TLSL. METHODS AND MATERIALS We employed asymmetric-field-inversion gel electrophoresis (AFIGE), a pulsed-field gel electrophoresis (PFGE) method to quantitate DSB in a battery of five cells lines grown in the presence of different concentrations of BrdU. We measured specifically the yields of promptly forming DSB (prDSB) using low temperature lysis protocols, and the yields of total DSB (tDSB = prDSB + tlDSB; tlDSB form after evolution to SSB of TLSL) using high temperature lysis protocols. RESULTS We report that incorporation of BrdU generates similar increases in the formation of tlDSB and prDSB, but variations are noted among the different cell lines tested. CONCLUSIONS The similar increase in the yields of tlDSB and prDSB in BrdU substituted DNA showed that shifts in the yields of these forms of lesions could not be invoked to explain BrdU radiosensitization.
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Affiliation(s)
- Fanghua Li
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School , Essen , Germany
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9
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Hou D, Greenberg MM. DNA interstrand cross-linking upon irradiation of aryl halide C-nucleotides. J Org Chem 2014; 79:1877-84. [PMID: 24559326 DOI: 10.1021/jo4028227] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
γ-Radiolysis kills cells by damaging DNA via radical processes. Many of the radical pathways are O2 dependent, which results in a reduction in the cytotoxicity of ionizing radiation in hypoxic tumor cells. Consequently, there is a need for chemical agents that increase DNA damage by ionizing radiation under O2-deficient conditions. Modified nucleotides that are incorporated in DNA and produce highly reactive σ-radicals are useful as radiosensitizing agents. Aryl halide C-nucleotides (4-6) were incorporated into oligonucleotides by solid-phase synthesis. Duplex DNA containing 4-6 forms interstrand cross-links upon γ-radiolysis under anaerobic conditions or UV irradiation. Deep Vent (exo(-)) DNA polymerase accepted the nucleotide triphosphate of C-nucleotide 6 as a substrate and preferentially incorporated it opposite pyrimidines, but no further extension was detected. Incorporation of 6 in extended products by Deep Vent (exo(-)) during PCR or by Sequenase during copying of single stranded DNA plasmid was undetectable. Aryl halide nucleotide analogues that produce DNA interstrand cross-links under anaerobic conditions upon irradiation are potentially useful as radiosensitizing agents, but further research is needed to identify molecules that are incorporated by DNA polymerases and do not block further polymerization for this approach to be useful in cells.
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Affiliation(s)
- Dianjie Hou
- Department of Chemistry Johns Hopkins University 3400 North Charles Street, Baltimore, Maryland 21218, United States
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10
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Fujii Y, Genet MD, Roybal EJ, Kubota N, Okayasu R, Miyagawa K, Fujimori A, Kato TA. Comparison of the bromodeoxyuridine-mediated sensitization effects between low-LET and high-LET ionizing radiation on DNA double-strand breaks. Oncol Rep 2013; 29:2133-9. [PMID: 23525528 DOI: 10.3892/or.2013.2354] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 12/17/2012] [Indexed: 11/06/2022] Open
Abstract
The incorporation of halogenated pyrmidines such as bromo- and iodo-deoxyuridines (BrdU, IdU) into DNA as thymidine analogs enhances cellular radiosensitivity when high-linear energy transfer (LET) radiation is not used. Although it is known that high-LET ionizing radiation confers fewer biological effects resulting from halogenated pyrimidine incorporation, the exact mechanisms of reduced radiosensitivity with high-LET radiation are not clear. We investigated the radiosensitization effects of halogenated pyrimidines with high-LET radiation using accelerated carbon and iron ions. Cells synchronized into the G1 phase after unifilar (1 cell cycle) and bifilar (2 cell cycles) substitution with 10 µM BrdU were exposed to various degrees of LET with heavy ions and X-rays. We then carried out a colony formation assay to measure cell survival. The γ-H2AX focus formation assay provided a measure of DNA double-strand break (DSB) formation and repair kinetics. Chromosomal aberration formations for the first post-irradiation metaphase were also scored. For both low-LET X-rays and carbon ions (13 keV/µm), BrdU incorporation led to impaired DNA repair kinetics, a larger initial number of DNA DSBs more frequent chromosomal aberrations at the first post-irradiated metaphase, and increased radiosensitivity for cell lethality. The enhancement ratio was higher after bifilar substitution. In contrast, no such synergistic enhancements were observed after high-LET irradiation with carbon and iron ions (70 and 200 keV/µm, respectively), even after bifilar substitution. Our results suggest that BrdU substitution did not modify the number and quality of DNA DSBs produced by high-LET radiation. The incorporation of halogenated pyrimidines may produce more complex/clustered DNA damage along with radicals formed by low-LET ionizing radiation. In contrast, the severity of damage produced by high-LET radiation may undermine the effects of BrdU and account for the observed minimal radiosensitization effects.
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Affiliation(s)
- Yoshihiro Fujii
- Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Inashiki, Ibaraki 300-0394, Japan
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FRANKEN NICOLAASA, OEI ARLENEL, KOK HPETRA, RODERMOND HANSM, SMINIA PETER, CREZEE JOHANNES, STALPERS LUKASJ, BARENDSEN GERRITW. Cell survival and radiosensitisation: Modulation of the linear and quadratic parameters of the LQ model. Int J Oncol 2013; 42:1501-15. [DOI: 10.3892/ijo.2013.1857] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Accepted: 12/21/2012] [Indexed: 11/05/2022] Open
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Park Y, Polska K, Rak J, Wagner JR, Sanche L. Fundamental mechanisms of DNA radiosensitization: damage induced by low-energy electrons in brominated oligonucleotide trimers. J Phys Chem B 2012; 116:9676-82. [PMID: 22812492 DOI: 10.1021/jp304964r] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The replacement of nucleobases with brominated analogs enhances DNA radiosensitivity. We examine the chemistry of low-energy electrons (LEEs) in this sensitization process by experiments with thin films of the oligonucleotide trimers TBrXT, where BrX = 5-BrU (5-bromouracil), 5-BrC (5-bromocytosine), 8-BrA (8-bromoadenine), or 8-BrG (8-bromoguanine). The products induced from irradiation of thin (∼ 2.5 nm) oligonucleotide films, with 10 eV electrons, under ultrahigh vacuum (UHV) are analyzed by HPLC-UV. The number of damaged brominated trimers ranges from about 12 to 15 × 10(-3) molecules per incident electron, whereas under the identical conditions, these numbers drop to 4-7 × 10(-3) for the same, but nonbrominated oligonucleotides. The results of HPLC analysis show that the main degradation pathway of trinucleotides containing brominated bases involve debromination (i.e., loss of the bromine atom and its replacement with a hydrogen atom). The electron-induced sum of products upon bromination increases by factors of 2.1 for the pyrimidines and 3.2 for the purines. Thus, substitution of any native nucleobase with a brominated one in simple models of DNA increases LEE-induced damage to DNA and hence its radiosensitivity. Furthermore, besides the brominated pyrimidines that have already been tested in clinical trials, brominated purines not only appear to be promising sensitizers for radiotherapy, but could provide a higher degree of radiosensitization.
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Affiliation(s)
- Yeunsoo Park
- Center for Radiobiology and Radiotherapy, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
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13
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Konigsfeld KM, Lee M, Urata SM, Aguilera JA, Milligan JR. Free terminal amines in DNA-binding peptides alter the product distribution from guanine radicals produced by single electron oxidation. Int J Radiat Biol 2011; 88:230-8. [PMID: 22124251 DOI: 10.3109/09553002.2012.643853] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Electron deficient guanine radical species are major intermediates produced in DNA by the direct effect of ionizing irradiation. There is evidence that they react with amine groups in closely bound ligands to form covalent crosslinks. Crosslink formation is very poorly characterized in terms of quantitative rate and yield data. We sought to address this issue by using oligo-arginine ligands to model the close association of DNA and its binding proteins in chromatin. MATERIALS AND METHODS Guanine radicals were prepared in plasmid DNA by single electron oxidation. The product distribution derived from them was assayed by strand break formation after four different post-irradiation incubations. RESULTS We compared the yields of DNA damage produced in the presence of four ligands in which neither, one, or both of the amino and carboxylate termini were blocked with amides. Free carboxylate groups were unreactive. Significantly higher yields of heat labile sites were observed when the amino terminus was unblocked. The rate of the reaction was characterized by diluting the unblocked amino group with its amide blocked derivative. CONCLUSION These observations provide a means to develop quantitative estimates for the yields in which these labile sites are formed in chromatin by exposure to ionizing irradiation.
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Affiliation(s)
- Katie M Konigsfeld
- Department of Radiology, University of California at San Diego, La Jolla, California 92093-0610, USA
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14
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Zainol M, Stoute J, Almeida GM, Rapp A, Bowman KJ, Jones GDD. Introducing a true internal standard for the Comet assay to minimize intra- and inter-experiment variability in measures of DNA damage and repair. Nucleic Acids Res 2010; 37:e150. [PMID: 19828597 PMCID: PMC2794182 DOI: 10.1093/nar/gkp826] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Comet assay (CA) is a sensitive/simple measure of genotoxicity. However, many features of CA contribute variability. To minimize these, we have introduced internal standard materials consisting of 'reference' cells which have their DNA substituted with BrdU. Using a fluorescent anti-BrdU antibody, plus an additional barrier filter, comets derived from these cells could be readily distinguished from the 'test'-cell comets, present in the same gel. In experiments to evaluate the reference cell comets as external and internal standards, the reference and test cells were present in separate gels on the same slide or mixed together in the same gel, respectively, before their co-exposure to X-irradiation. Using the reference cell comets as internal standards led to substantial reductions in the coefficient of variation (CoV) for intra- and inter-experimental measures of comet formation and DNA damage repair; only minor reductions in CoV were noted when the reference and test cell comets were in separate gels. These studies indicate that differences between individual gels appreciably contribute to CA variation. Further studies using the reference cells as internal standards allowed greater significance to be obtained between groups of replicate samples. Ultimately, we anticipate that development will deliver robust quality assurance materials for CA.
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Affiliation(s)
- Murizal Zainol
- Radiation and Oxidative Stress Group, Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester, UK
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15
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Tsoi M, Do TT, Tang V, Aguilera JA, Perry CC, Milligan JR. Characterization of condensed plasmid DNA models for studying the direct effect of ionizing radiation. Biophys Chem 2010; 147:104-10. [PMID: 20096988 DOI: 10.1016/j.bpc.2009.12.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 12/19/2009] [Accepted: 12/19/2009] [Indexed: 10/20/2022]
Abstract
We have examined the changes in physical properties of aqueous solutions of the plasmid pUC18 that take place on the addition of the cationic oligopeptide penta-arginine. An increase in sedimentation rate and static light scattering, and changes in the nucleic acid CD spectrum all suggest that this ligand acts to condense the plasmid. Dynamic light scattering suggests the hydrodynamic radii of the condensate particles are a few micrometers, ca. 50-fold larger than that of the monomeric plasmid. Condensation of the plasmid also produces a ca. 100-fold decrease in the strand break yield produced by gamma irradiation. This extensive protection against reactive intermediates in the bulk of the solution implies that condensed plasmid DNA may offer a model system with which to study the direct effect of ionizing radiation (ionization of the DNA itself). The use of peptide ligands as condensing agents in this application is attractive because the derivatives of several amino acids (particularly tryptophan and tyrosine) have been shown to modify the radiation chemistry of DNA extensively.
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Affiliation(s)
- Mandi Tsoi
- Department of Radiology, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0610, USA
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16
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Heshmati E, Abdolmaleki P, Mozdarani H, Sarvestani AS. Effects of halogen substitution on Watson–Crick base pairing: A possible mechanism for radiosensitivity. Bioorg Med Chem Lett 2009; 19:5256-60. [DOI: 10.1016/j.bmcl.2009.06.105] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 05/21/2009] [Accepted: 06/18/2009] [Indexed: 11/15/2022]
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17
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Ly A, Bullick S, Won JH, Milligan JR. Cationic peptides containing tyrosine protect against radiation-induced oxidative DNA damage. Int J Radiat Biol 2009; 82:421-33. [PMID: 16846977 DOI: 10.1080/09553000600771531] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE To examine the effect of the amino acid tyrosine on oxidatively or direct-type damaged DNA damage when it is present in a DNA binding ligand. MATERIALS AND METHODS We made use of tetralysine ligands to ensure binding to DNA and to condense the DNA, and simulated direct-type damage by using gamma irradiation in the presence of thiocyanate ions. These ligands contained an additional C terminal amino acid. Phenylalanine was used as a control for tyrosine. These ligands were used in conjuction with a plasmid substrate to quantify strand break yields. Base damage yields were estimated by measuring the strand break yield after incubation of the plasmid with the bacterial base excision repair enzyme formamidopyrimidine-DNA N-glycosylase (FPG). RESULTS When the condensing ligand contains an additional tyrosine or tryptophan residue, the plasmid is protected against the effects of a single electron oxidation, as assayed by sensitivity to a base excision repair enzyme. This protection is significantly greater in condensed plasmid where the amino acid residues are in close proximity to the DNA, and can be observed even when only a small fraction of the ligand contains tyrosine. CONCLUSIONS Bound tyrosine residues located in close proximity to DNA are capable of reversing oxidative DNA damage far more efficiently than when present unbound in the bulk solution. This suggests that tyrosine residues in DNA binding proteins may participate in the repair of DNA that has been oxidatively damaged by ionizing radiation.
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Affiliation(s)
- Anne Ly
- Department of Radiology, University of California at San Diego, La Jolla, California 92093-0610, USA.
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18
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Zeng Y, Wang Y. Sequence-dependent formation of intrastrand crosslink products from the UVB irradiation of duplex DNA containing a 5-bromo-2'-deoxyuridine or 5-bromo-2'-deoxycytidine. Nucleic Acids Res 2006; 34:6521-9. [PMID: 17130170 PMCID: PMC1702501 DOI: 10.1093/nar/gkl892] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The replacement of thymidine with 5-bromo-2′-deoxyuridine (BrdU) is well-known to sensitize cells to ionizing radiation and photoirradiation. We reported here the sequence-dependent formation of intrastrand crosslink products from the UVB irradiation of duplex oligodeoxynucleotides harboring a BrdU or its closely related 5-bromo-2′-deoxycytidine (BrdC). Our results showed that two types of crosslink products could be induced from d(BrCG), d(BrUG), d(GBrU), or d(ABrU); the C(5) of cytosine or uracil could be covalently bonded to the N(2) or C(8) of its neighboring guanine, and the C(5) of uracil could couple with the C(2) or C(8) of its neighboring adenine. By using those crosslink product-bearing dinucleoside monophosphates as standards, we demonstrated, by using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), that all the crosslink products described above except d(G[N(2)-5]U) and d(G[N(2)-5]C) could form in duplex DNA. In addition, LC-MS/MS quantification results revealed that both the nature of the halogenated pyrimidine base and its 5′ flanking nucleoside affected markedly the generation of intrastrand crosslink products. The yields of crosslink products were much higher while the 5′ neighboring nucleoside was a dG than while it was a dA, and BrdC induced the formation of crosslink products much more efficiently than BrdU. The formation of intrastrand crosslink products from these halopyrimidines in duplex DNA may account for the photosensitizing effects of these nucleosides.
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Affiliation(s)
| | - Yinsheng Wang
- To whom correspondence should be addressed. Tel: +1 951 827 2700; Fax: +1 951 827 4713;
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19
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Abstract
PURPOSE To define ionic conditions under which oligolysines condense DNA as assayed by radioprotection of a plasmid substrate. And to compare these conditions with those required by the well-characterized ligands spermidine and hexammine cobalt (III). This will enable a reversible compaction model for plasmid DNA to be devised that models more closely mammalian chromatin than those based on polyamines. MATERIALS AND METHODS Aqueous solutions containing plasmid DNA, sodium perchlorate and one of the five ligands trilysine, tetralysine, pentalysine, spermidine, or hexammine cobalt (III) were subjected to gamma-irradiation. The yields of the resulting single-strand breaks were quantified by gel electrophoresis. The effects of tetralysine and pentalysine were also examined by light scattering. RESULTS The combination of low concentrations of the ligand and high concentrations of sodium perchlorate produced a relatively high yield of single-strand breaks. In contrast, the combination of high concentrations of the ligand and low concentrations of sodium perchlorate resulted in an approximately 25-fold lower single-strand break yield. The transition between these two break yields took place over very narrow concentration ranges of the ligand. A large change in light scattering occurred at the same concentration. The radioprotective ability of the ligands decreased in the order pentalysine > tetralysine > hexammine cobalt (III) > spermidine > trilysine. CONCLUSIONS The effect of the oligolysines is qualitatively very similar to the previously reported radioprotection produced under similar conditions by the polyamines spermidine and spermine. It is caused by condensation of the DNA into a highly compacted form. As peptides, oligolysines are structurally more closely related than other ligands to naturally occurring DNA condensing agents such as histone proteins. Therefore, they may form the basis of a model system suitable for studying DNA damage produced by the direct effect of ionizing radiation (ionization of the DNA itself).
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Affiliation(s)
- G L Newton
- Department of Chemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0610, USA
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20
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Cecchini S, Girouard S, Huels MA, Sanche L, Hunting DJ. Single-strand-specific radiosensitization of DNA by bromodeoxyuridine. Radiat Res 2004; 162:604-15. [PMID: 15548110 DOI: 10.1667/rr3267] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The effects of bromodeoxyuridine (BrdUrd) substitution for thymidine on gamma-ray-induced strand breakage were determined in single- and double-stranded oligonucleotides and double-stranded oligonucleotides containing a mismatched bubble region. BrdUrd does not sensitize complementary double-stranded DNA to gamma-ray-induced strand breakage, but it greatly sensitizes single-stranded DNA. However, when the BrdUrd is present in a single-stranded bubble of a double-stranded oligonucleotide, the non-base-paired nucleotides adjacent to the BrdUrd as well as several unpaired sites on the opposite unsubstituted strand are strongly sensitized. The radiosensitization properties of BrdUrd result primarily from the electrophilic nature of the bromine, making it a good leaving group and leading to the irreversible formation of the uridine-yl radical (dUrd(.)) or the uridine-yl anion (dUrd(-)) upon addition of an electron. The radiolytic loss of the bromine atom is greatly suppressed in double-stranded compared to single-stranded DNA. Thus we propose that the radiosensitization effects of bromouracil in vivo will likely be limited to single-strand regions such as found in transcription bubbles, replication forks, DNA bulges and the loop region of telomeres. Our results may have profound implications for the clinical use of bromodeoxyuridine (BrdUrd) as a radiosensitizer as well as for the development of targeted radiosensitizers.
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Affiliation(s)
- S Cecchini
- Group in the Radiation Sciences, Department of Nuclear Medicine and Radiobiology, Université de Sherbrooke, Sherbrooke, Quebec, Canada J1H 5N4
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21
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Pignol JP, Rakovitch E, Beachey D, Le Sech C. Clinical significance of atomic inner shell ionization (ISI) and Auger cascade for radiosensitization using IUdR, BUdR, platinum salts, or gadolinium porphyrin compounds. Int J Radiat Oncol Biol Phys 2003; 55:1082-91. [PMID: 12605988 DOI: 10.1016/s0360-3016(02)04508-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
PURPOSE Halogenated pyrimidines (iododeoxyuridine [IUdR] and bromodeoxyuridine [BUdR]), platinum salts, and gadolinium porphyrins are heavy atom compounds used as radiosensitizers. For IUdR, it has been hypothesized that iodine inner shell ionizations (ISI) and Auger cascades could be one of the primary radiosensitization mechanisms. The purpose of this paper is to estimate the number of ISI produced per tumor cell and per 2 Gy irradiation in clinically relevant modelings. MATERIALS AND METHODS ISI were evaluated using a two-step method. Photon-induced ISI were calculated using the MCNP-4C Monte Carlo code, heavy atom concentrations from clinical data published in the literature, and at various depths in a water phantom irradiated with 6-MV, (60)Co, (137)Cs, or (192)Ir sources. Electron knock-on induced ISI on K, L, and M atomic shells were evaluated with an hybrid method, using simulated electron spectra and cross-sections derived from the Møller formalism. Using a biological dose equivalence of 0.05 Gy per cell ISI, relative biological effectiveness (RBE) values were calculated for each situation. RESULTS For platinum and gadolinium, ISI occurs in far less than 0.1% of the cell, whichever is the configuration. For IUdR and BUdR, ISI occurs in between 45% to 483% of the cell. Due to spectrum degradation, about 3 times more photoelectric ISI are generated at greater than shallower depths, and 10 times more for (192)Ir compared with (60)Co or 6-MV X-rays. Photoelectric ISI are about 3 times more frequent for iodine than bromine, but electron knock-on ISI are more frequent on bromine, and at the end about the same number of ISI are generated for both elements. RBEs were found to be between 1.01 and 1.12 for clinically relevant irradiation settings. CONCLUSIONS The mechanisms of radiosensitization for platinum and gadolinium are clearly not related to an Auger cascade. For halogenated pyrimidines, however, clinically relevant numbers of ISI are generated within each cell. For IUdR, ISI appears to be strongly tied to the photon spectra. Halogenated pyrimidines should be evaluated again clinically, but using lower energy photons like a (192)Ir implant.
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Affiliation(s)
- Jean-Philippe Pignol
- Department of Radiation Oncology, Toronto-Sunnybrook Regional Cancer Centre, Toronto, Ontario, Canada.
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22
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Abstract
The ionizing radiation induced bystander effect is initiated by damage to a cellular molecule which then gives rise to a signal exported to other cells. The nature of this damage is considered with the understanding that it may not be the same as that responsible for the traditional cellular effects of radiation. Consideration is give to amounts of endogenous damage and to radiation yields of the various candidate lesions.
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Affiliation(s)
- John F Ward
- Department of Radiology, 0610, University of California, La Jolla, San Diego, CA 92093, USA.
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23
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Franken NA, Van Bree C, Veltmaat MA, Rodermond HM, Haveman J, Barendsen GW. Radiosensitization by bromodeoxyuridine and hyperthermia: analysis of linear and quadratic parameters of radiation survival curves of two human tumor cell lines. JOURNAL OF RADIATION RESEARCH 2001; 42:179-190. [PMID: 11599884 DOI: 10.1269/jrr.42.179] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Sensitization by bromodeoxyuridine (BrdUrd) and hyperthermia (HT) on cell reproductive death induced by ionizing radiation was analyzed using the linear-quadratic [S(D)/S(0)=exp(-(alphaD + betaD2)]] model. Plateau-phase human lung tumor cells (SW-1573) and human colorectal carcinonoma cells (RKO) were treated with BrdUrd, radiation and HT. LQ-analysis was performed at iso-incubation dose and at iso-incorporation level of BrdUrd. and at iso-HT doses and iso-survival levels after HT. Clonogenic assays were performed 24 h after treatment to allow repair of potentially lethal damage (PLD). In SW cells BrdUrd. HT or the combination significantly increased the alpha-parameter (factor 2.0-5.7), without altering the beta-parameter. In RKO cells sensitization with BrdUrd increased both a (factor 1.4) and beta (factor 1.3) while HT only influenced beta (factor 2.1-4.0). The combination did not further increase the a and beta. The results indicate that BrdUrd has its main effect on the parameter alpha, dominant at clinically relevant radiation doses but that HT can affect both a and beta. The addition of BrdUrd and HT provides a method to enhance the efficacy of radiotherapy.
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Affiliation(s)
- N A Franken
- Department of Radiotherapy, Academic Medical Center, University of Amsterdam, The Netherlands.
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24
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Hawkins RB. A microdosimetric-kinetic model for the sensitization of v79 cells to radiation by incorporation of bromodeoxyuridine. Radiat Res 2001; 155:698-702. [PMID: 11302767 DOI: 10.1667/0033-7587(2001)155[0698:amkmft]2.0.co;2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Hawkins, R. B. A Microdosimetric-Kinetic Model for the Sensitization of V79 Cells to Radiation by Incorporation of Bromodeoxyuridine. Radiat. Res. 155, 698-702 (2001). The sensitization of G(1)-phase V79 cells to killing by ionizing radiation through incorporation of bromodeoxyuridine (BrdU) in their DNA has been reported to occur exclusively through an increase in the value of the quadratic parameter of the linear-quadratic survival relationship (beta) with no change in the linear parameter (alpha). The consequence of this, as understood through the microdosimetric-kinetic model of cell survival, is discussed. It is shown that the invariance of alpha implies that sensitization is due solely to a decrease in the rate of repair of the initial (potentially lethal) lesions in DNA containing BrdU. Further, for alpha to be unchanged, the average size of the compartments into which the nucleus is partitioned (domains), as postulated in the microdosimetric-kinetic model, must vary in proportion to the reciprocal of the square root of the rate constant for repair of the DNA lesions. This implies that the domain is not a structural subunit of the nucleus. It is a surrogate representation of the consequence of lesions in DNA being restricted to a region in the vicinity of the location in the nucleus at which they are created. A lesion is confined because the distance it can diffuse by random flight to react with another lesion to form a lethal lesion is restricted because a lesion's lifetime is limited by the repair process.
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Affiliation(s)
- R B Hawkins
- Department of Radiation Oncology, Alton Ochsner Medical Foundation and Ochsner Clinic, 1514 Jefferson Highway, New Orleans, Louisiana 70121, USA
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25
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Hammers HJ, Kirchner H, Schlenke P. Ultraviolet-induced detection of halogenated pyrimidines: simultaneous analysis of DNA replication and cellular markers. CYTOMETRY 2000; 40:327-35. [PMID: 10918283 DOI: 10.1002/1097-0320(20000801)40:4<327::aid-cyto8>3.0.co;2-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND We describe a new nonenzymatic methodology that allows the simultaneous detection of DNA replication and other cellular markers such as immunophenotyping. DNA replicating cells are identified by their incorporation of halogenated thymidine analogs, e.g., 5-bromo-deoxyuridine (BrdUrd). METHODS Irradiation with ultraviolet (UV)-B or UV-A light in the presence of Hoechst 33258 and subsequent treatment with a hypotonic buffer makes BrdUrd accessible to monoclonal antibodies (mAb), thus allowing its sensitive detection. RESULTS The photolysis of BrdUrd in DNA with UV light is sequence dependent and results in DNA damage, allowing the detection of remaining BrdUrd using hypotonic conditions. However, treatment with other inducers of single or double- strand breaks of DNA such as gamma irradiation or hydrogen peroxide did not allow BrdUrd detection. The new methodology is compatible with both mild crosslinking fixation, i.e., aldehydes, or coagulative fixation, i.e., alcohols. The successful identification of CD34+, CD138+, or CD19+ cells out of heterogeneous cell suspensions and their cell-cycle analysis are described. Results correlated very well with acid denaturation (r = 0.972). The average coefficient of variation (CV) of G(1) in the DNA histogram was smaller than 5%, resulting in good preservation of DNA distribution. Also, the signal-to-noise ratio was almost twice as high as for 2N acid denaturation, facilitating convenient discrimination of BrdUrd-positive cells. CONCLUSIONS In contrast to previous approaches, this methodology eliminates the need for any additional enzymatic treatment such as DNA digestion or strand-break labeling after UV irradiation. The method is fast, convenient, and inexpensive and should be able to promote the use of halogenated pyrimidines in basic and clinical research of cancer, immunology, and pharmacology.
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Affiliation(s)
- H J Hammers
- Institute of Immunology and Transfusion Medicine, University of Luebeck School of Medicine, Germany.
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26
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Rieber M, Strasberg-Rieber M. Induction of p53 and melanoma cell death is reciprocal with down-regulation of E2F, cyclin D1 and pRB. Int J Cancer 1998; 76:757-60. [PMID: 9610736 DOI: 10.1002/(sici)1097-0215(19980529)76:5<757::aid-ijc22>3.0.co;2-#] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Tumor-suppressor-gene products such as p53 and retinoblastoma (Rb) play an important role as negative regulators of cell-cycle progression, which is reciprocally favored by the availability of cyclin D1 and the E2F transcription factor. We now show that UV irradiation of B16 melanoma after prior exposure to the radiation sensitizer, bromodeoxyuridine (BUdR) leads to induction of p53 and DNA fragmentation, and concomitant decreases in Rb, E2F, cyclin D1, and cell viability, with no comparable effects on irradiated unsensitized cells. Our data suggest that over-expression of p53 correlates with down-regulation of E2F, cyclin D1 in inducing apoptosis.
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Affiliation(s)
- M Rieber
- Instituto Venezolano de Investigaciones Científicas, Centro de Microbiología y Biología Celular, Tumor-Cell Biology Laboratory, Caracas, Venzuela.
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27
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Van Bree C, Franken NA, Bakker PJ, Klomp-Tukker LJ, Barendsen GW, Kipp JB. Hyperthermia and incorporation of halogenated pyrimidines: radiosensitization in cultured rodent and human tumor cells. Int J Radiat Oncol Biol Phys 1997; 39:489-96. [PMID: 9308955 DOI: 10.1016/s0360-3016(97)00129-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
PURPOSE To investigate the possible benefit of hyperthermia (HT) in combination with radiosensitization by halogenated pyrimidines (HPs) in rodent as well as in human tumor cells. METHODS AND MATERIALS Exponentially growing rodent cells, radiosensitive R-1 and MOS cells and radioresistant RUC-II and V79 cells, and human SW1573 cells, were exposed to 0, 1, 2, and 4 microM of chloro- (CldUrd), bromo- (BrdUrd), or iodo-deoxyuridine (IdUrd) in the culture medium. Survival after irradiation with gamma-rays from a 137Cs source and/or hyperthermic treatment (HT, 60 min at 42 degrees C) was determined by clonogenic assay. Linear-quadratic analyses of the radiation survival curves were performed to assess sensitization in the dose range 1 to 3 Gy relevant to radiotherapy. RESULTS The incorporation of HPs sensitized all cell lines to HT and resulted in radiosensitization dependent on the percentage of thymidine replacement. At equal levels of thymidine replacement, IdUrd was the most potent radiosensitizer. HT further increased radiation-induced lethality of cells that had incorporated HPs. Linear-quadratic analyses showed that HT further increased the linear parameter of the LQ formula while the quadratic parameter was not significantly changed. CONCLUSION The combination of HT and HPs act additively in increasing the radiosensitivity of rodent tumor cell lines with varying radiosensitivities as well as of a human tumor cell line. In particular, the ratio of the linear parameter to the quadratic parameter, relevant for fractionation effects in radiotherapy, was increased.
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Affiliation(s)
- C Van Bree
- Academic Medical Center, University of Amsterdam, Department of Radiotherapy, The Netherlands
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28
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Franken NA, Van Bree CV, Kipp JB, Barendsen GW. Modification of potentially lethal damage in irradiated Chinese hamster V79 cells after incorporation of halogenated pyrimidines. Int J Radiat Biol 1997; 72:101-9. [PMID: 9246199 DOI: 10.1080/095530097143581] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Radiosensitization of exponentially growing and plateau phase Chinese hamster V79 cells by incorporation of halogenated pyrimidines (HP) was investigated for different culture conditions that influenced repair. For this purpose cells were grown for 72 h with 0, 1, 2 and 4 microM of chloro-(CldUrd), bromo- (BrdUrd) or iodo-deoxyuridine (IdUrd) and were subsequently irradiated with gamma-rays from a 197Cs source, either in exponential growth or in plateau-phase. Cell survival after irradiation was determined by clonogenic assay. In exponentially growing cultures thymidine-replacement in the DNA of the cells after incubation with 4 microM of CldUrd, BrdUrd and IdUrd was 22.3, 32.7 and 12.7%, respectively. In plateau-phase cultures the percentage thymidine replacement in the DNA of the cells after incubation during growth with 4 microM CldUrd, BrdUrd and IdUrd was 27.5, 33.8 and 10.7%, respectively. Linear-quadratic analyses of the radiation survival curves were performed. In exponentially growing cells a marked increase by a factor 2-3 of the value of alpha was obtained. The beta term significantly increased only in cells which were grown in the presence of BrdUrd and which were trypsinized and replated immediately after irradiation. In plateau-phase cells which were trypsinized and plated immediately after irradiation both alpha and beta increased up to a factor 2-3 with increasing incorporation of halogenated pyrimidines. In plateau phase cells which were allowed to repair potentially lethal damage (PLD) for 6 h and subsequently trypsinized and plated, alpha increased by a factor 3-4. In these latter conditions changes in beta were smaller. In exponentially growing cells in which repair was allowed after irradiation by plating prior to the treatment, the alpha values decreased for all the HP drugs tested as compared to the alpha of cells plated immediately after irradiation. In contrast, delay of plating for plateau phase cells yielded increased alpha values not only when compared with the alpha of plateau phase cells plated immediately after treatment but also when compared with the alpha value of radiosensitized exponentially growing cells. The increase of alpha might be interpreted as an enhancement in the expression of PLD. The larger contribution of fixation of PLD might be due to initial DNA damage and/or to inhibition of PLD repair resulting from incorporation of HP. The increase of beta might be attributed to enhanced interaction or to fixation of sublethal damage (SLD). In view of clinical applications of HP it is of interest that sensitization is not abolished in plateau-phase cells.
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Affiliation(s)
- N A Franken
- Department of Radiotherapy, University of Amsterdam, The Netherlands
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29
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Jonsson AC, Jönsson BA, Strand SE, Grafström G, Spanne P. Cell survival after Auger electron emission from stable intracellular indium exposed to monochromatic synchrotron radiation. Acta Oncol 1996; 35:947-52. [PMID: 9004776 DOI: 10.3109/02841869609104050] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The biological effect of Auger electrons emitted from indium in V79 cells was investigated. K-shell vacancies were induced by synchrotron x-rays. Two energies, 100 eV above and below the K-edge of indium, were used. The cell survival for controls was similar to that which has been reported by others, with D37 = 4.4 Gy. Indium-oxine-labelled cells exhibited a survival clearly below that of the controls, D37 = 3.2 Gy, but no significant difference in survival between irradiations above and below the K-edge could be observed. The explanation is, inter alia, that the number of photons interacting with indium atoms incorporated into the cell, is small compared with the number of photons interacting with other atoms in the cell. The toxicity of indium oxine made it impossible to incorporate a sufficient number of indium atoms into the cells to observe a difference in this study. However, monoenergetic irradiation above and below the K-edge, provides a technique for the investigation of basic biological effects of Auger processes.
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Affiliation(s)
- A C Jonsson
- Department of Radiation Physics, Lund University, Sweden.
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30
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Jones GD, Ward JF, Limoli CL, Moyer DJ, Aguilera JA. Mechanisms of radiosensitization in iododeoxyuridine-substituted cells. Int J Radiat Biol 1995; 67:647-53. [PMID: 7608627 DOI: 10.1080/09553009514550761] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The radiosensitization caused by iododeoxyuridine (IdU)-substitution of thymidine in V79-171 cells is decreased by the presence of acetone during irradiation. Acetone, at 1 mol dm-3, removes almost all the increase in double strand breaks (dsbs) caused by IdU substitution, but removes only about two-thirds of the enhancement in killing. Similar observations were made with BrdU-substituted cells. The decrease in cell radiosensitization coincides with the removal of the additional dsbs. The protection afforded by acetone is assumed to be due to its scavenging of hydrated electrons, thought to be the active species causing enhanced DNA damage in the presence of halogenated pyrimidines. The residual component of IdU radiosensitization, which could not be removed by treatment with acetone, is manifest largely as a shoulder effect (Dq) and may be due to either a subset of non-scavengable, lethal dsbs and/or the influence of IdU on the fixation of potentially lethal damage. This study further demonstrates that halogenated pyrimidine-mediated radiosensitization consists of at least distinct components each associated with a different phenomenon.
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Affiliation(s)
- G D Jones
- Department of Radiology-0610, University of California, San Diego, La Jolla 92093-0610, USA
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31
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Fuciarelli AF, Sisk EC, Miller JH, Zimbrick JD. Radiation-induced electron migration in nucleic acids. Int J Radiat Biol 1994; 66:505-9. [PMID: 7983438 DOI: 10.1080/09553009414551531] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Radiation-induced electron migration along DNA is a mechanism by which randomly produced stochastic energy deposition events can lead to non-random types of damage along DNA manifested distal to the sites of the initial energy deposition. Radiation-induced electron migration in nucleic acids has been examined using oligonucleotides containing 5-bromouracil (5-BrU). Interaction of 5-BrU with solvated electrons results in release of bromide ions and formation or uracil-5-yl radicals. Monitoring either bromide ion release or uracil formation provides an opportunity to study electron migration processes in model nucleic acid systems. Using this approach we have discovered that electron migration along oligonucleotides is significantly influenced by the base sequence and strandedness. Migration along 7 base pairs in oligonucleotides containing guanine bases was observed for oligonucleotides irradiated in solution, which compares with mean migration distances of 6-10 bp for Escherichia coli DNA irradiated in solution and 5.5 bp for E. coli DNA irradiated in cells. Evidence also suggests that electron migration can occur preferentially in the 5' to 3' direction along a double-stranded oligonucleotide containing a region of purine bases adjacent to the 5-BrU moiety. Our continued efforts will provide information regarding the contribution of electron transfer along DNA to formation of locally multiply damaged sites created in DNA by exposure to ionizing radiation.
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Affiliation(s)
- A F Fuciarelli
- Biology and Chemistry Department, Pacific Northwest Laboratory, Richland, WA 99352
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32
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Dover R, Patel K. Improved methodology for detecting bromodeoxyuridine in cultured cells and tissue sections by immunocytochemistry. HISTOCHEMISTRY 1994; 102:383-7. [PMID: 7532640 DOI: 10.1007/bf00268909] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Detection of DNA synthesizing cells may often be achieved by immunocytochemical detection of bromodeoxyuridine (BrdU), which is rapid and appears to give similar results to those found using tritiated thymidine. However, the methodology for detection of BrdU involves a denaturation or digestion step to allow access of the antibody to BrdU incorporated into single- rather than double-stranded DNA. We wished to determine if microwave treatment could be used to enhance the detection of BrdU without the need for any other digestion/denaturation steps. An important consideration was to investigate whether such treatment produces a similar quantitative result, since BrdU detection is usually assessed on the basis of cell number rather than topographical distribution. We have found that microwave treatment can allow considerably lower antibody concentrations and eliminates the need for any other denaturation step. It also reduces the non-specific background staining found when using monoclonal antibodies on mouse tissue. We have performed cell counts and found that the number of BrdU positive cells remains constant for a range of different immunocytochemical parameters. We also report conditions where immunopositivity is adversely affected by changes in technique and describe the optimised conditions for obtaining reproducible results.
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Affiliation(s)
- R Dover
- Department of Anatomy, Queen Mary and Westfield College, University of London, UK
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Wang Y, Pantelias GE, Iliakis G. Mechanism of radiosensitization by halogenated pyrimidines: the contribution of excess DNA and chromosome damage in BrdU radiosensitization may be minimal in plateau-phase cells. Int J Radiat Biol 1994; 66:133-42. [PMID: 8089623 DOI: 10.1080/09553009414551031] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We measured the contribution of increased DNA double-strand break (dsb) and interphase chromosome break induction in BrdU-mediated radiosensitization in exponentially growing (DNA dsb measurements only) and plateau-phase Chinese hamster ovary cells using an approach developed by Webb et al. (1993). The approach is based on the scavenging capacity of acetone for hydrated electrons, which are thought to react with bromine and form excess DNA and chromosome damage in BrdU-containing cells. In irradiated exponentially growing cells, acetone (1 M) removes the majority of excess DNA dsb induced in the presence of 4 microM BrdU (approximately 40% replacement of thymidine by BrdU), but does not restore cell radiosensitivity to the levels observed in BrdU-free cells. Although BrdU radiosensitizes cells by decreasing both D0 and Dq of the survival curve, acetone only restores D0 to levels measured in BrdU-free cells, but leaves Dq at levels measured in BrdU-containing cells. In plateau-phase cells, acetone removes the majority of excess DNA dsb and interphase chromosome breaks induced in the presence of 4 microM BrdU (approximately 50% replacement of thymidine by BrdU) but has only a small effect on BrdU-mediated radiosensitization to killing. These observations suggest that increased DNA damage production has a variable contribution in BrdU radiosensitization: it constitutes a major, albeit not the sole, component in the radiosensitization of exponentially growing cells, but only a minor component in the radiosensitization of plateau-phase cells. The results suggest that BrdU radiosensitization does not derive exclusively from increased DNA damage induction and support our previous hypothesis invoking repair inhibition/damage fixation as a component in the mechanism of radiosensitization. The results further suggest that repair inhibition is a major component in BrdU radiosensitization in exponentially growing cells, but the main cause of radiosensitization in plateau-phase cells.
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Affiliation(s)
- Y Wang
- Thomas Jefferson University, Department of Radiation Oncology and Nuclear Medicine, Philadelphia, PA 19107
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