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Dong Y, Chen Y, Zhou L, Shao Y, Fu X, Zheng Y. Molecular efficacy of radio- and chemotherapy sequences from direct DNA damage measurements. Int J Radiat Biol 2017; 93:1274-1282. [PMID: 28799445 DOI: 10.1080/09553002.2017.1366673] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PURPOSE To investigate the molecular aspects of the synergy between ionizing radiation and platinum (Pt) chemotherapeutic agents in cancer treatment with chemoradiation therapy (CRT) by measuring damages induced by low-energy electrons (LEE) to DNA bound to cisplatin. LEE are produced abundantly by any type of ionizing radiation and cisplatin represents a typical Pt-chemotherapeutic agents. MATERIALS AND METHODS Our strategy involves two parallel administrations of cisplatin and irradiation with a 4.6 and 9.6 eV electron fluence of 1.1 × 1012: (1) LEE bombardment of supercoiled DNA and its subsequent reaction with cisplatin; (2) the reaction of DNA with cisplatin followed by LEE irradiation. The damage yields for the loss of supercoiled (LS), single-strand breaks (SSB) and double-strand breaks (DSB) were obtained from gel electrophoresis analysis. Base modifications were revealed by treating the samples with Escherichia coli base excision repair endonuclease (Nth and Fpg). RESULTS The yields were deduced from the respective time-response for the reaction of DNA with cisplatin. The results show that binding cisplatin to DNA followed by LEE irradiation, consistently yields more DNA damages than the reverse order. In comparison to non-treated DNA, administration (2) results in an increase of LS and SSB of 1.4-3.3 folds and of DSB by more than an order of magnitude. Furthermore, after enzyme treatment, the yields of DSB rise by factors of 5.3-15.4, indicating a large increase of clustered damages, which should at least partially translate into an increase of lethal damages in cancer cells during the CRT. CONCLUSIONS Our results demonstrate that a strong synergy between radiation and cisplatin can only be achieved at the molecular level, if the drug is present at the time of irradiation. Furthermore, this work confirms the LEE mechanism previously proposed to explain the synergy between radiation and Pt drugs in CRT. It involves chemical sensitization of DNA prior to irradiation, to facilitate strand breaks and clustered damages induced by the highly reactive LEE.
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Affiliation(s)
- Yanfang Dong
- a Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou , P.R. China
| | - Yunfeng Chen
- a Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou , P.R. China
| | - Limei Zhou
- a Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou , P.R. China
| | - Yu Shao
- a Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou , P.R. China
| | - Xianzhi Fu
- a Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou , P.R. China
| | - Yi Zheng
- a Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment , Fuzhou University , Fuzhou , P.R. China
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2
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In vitro anticancer activity evaluation of new cationic platinum(II) complexes based on imidazole moiety. Bioorg Med Chem 2017; 25:1907-1913. [DOI: 10.1016/j.bmc.2017.02.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 01/16/2017] [Accepted: 02/07/2017] [Indexed: 11/20/2022]
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3
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Sahbani SK, Cloutier P, Bass AD, Hunting DJ, Sanche L. Electron Resonance Decay into a Biological Function: Decrease in Viability of E. coli Transformed by Plasmid DNA Irradiated with 0.5-18 eV Electrons. J Phys Chem Lett 2015; 6:3911-3914. [PMID: 26722892 PMCID: PMC5173358 DOI: 10.1021/acs.jpclett.5b01585] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Transient negative ions (TNIs) are ubiquitous in electron-molecule scattering at low electron impact energies (0-20 eV) and are particularly effective in damaging large biomolecules. Because ionizing radiation generates mostly 0-20 eV electrons, TNIs are expected to play important roles in cell mutagenesis and death during radiotherapeutic cancer treatment, although this hypothesis has never been directly verified. Here, we measure the efficiency of transforming E. coli bacteria by inserting into the cells, pGEM-3ZfL(-) plasmid DNA that confers resistance to the antibiotic ampicillin. Before transformation, plasmids are irradiated with electrons of specific energies between 0.5 and 18 eV. The loss of transformation efficiency plotted as a function of irradiation energy reveals TNIs at 5.5 and 9.5 eV, corresponding to similar states observed in the yields of DNA double strand breaks. We show that TNIs are detectable in the electron-energy dependence of a biological process and can decrease cell viability.
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Eguchi H, Umemura M, Kurotani R, Fukumura H, Sato I, Kim JH, Hoshino Y, Lee J, Amemiya N, Sato M, Hirata K, Singh DJ, Masuda T, Yamamoto M, Urano T, Yoshida K, Tanigaki K, Yamamoto M, Sato M, Inoue S, Aoki I, Ishikawa Y. A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging. Sci Rep 2015; 5:9194. [PMID: 25779357 PMCID: PMC4361848 DOI: 10.1038/srep09194] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 02/04/2015] [Indexed: 01/07/2023] Open
Abstract
Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies.
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Affiliation(s)
- Haruki Eguchi
- Cardiovascular Research Institute, Yokohama City University, Graduate School of Medicine, Yokohama, Japan,Advanced Applied Science Department, Research Laboratory, IHI Corporation, Yokohama, Japan,
| | - Masanari Umemura
- Cardiovascular Research Institute, Yokohama City University, Graduate School of Medicine, Yokohama, Japan
| | - Reiko Kurotani
- Biochemical Engineering, Faculty of Engineering, Yamagata University, Yonezawa, Yamagata, Japan
| | | | - Itaru Sato
- Department of Oral Surgery, Yokohama City University, Graduate School of Medicine, Yokohama, Japan
| | - Jeong-Hwan Kim
- Cardiovascular Research Institute, Yokohama City University, Graduate School of Medicine, Yokohama, Japan,Nanoparticles by Design Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | - Yujiro Hoshino
- Department of Environment and Natural Sciences, Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama, Japan
| | - Jin Lee
- Department of Radiology, Yokohama City University, Graduate School of Medicine, Yokohama, Japan
| | - Naoyuki Amemiya
- Department of Electrical Engineering, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Motohiko Sato
- Department of Physiology, Aichi Medical University, Nagakute, Aichi, Japan
| | - Kunio Hirata
- RIKEN, Research Infrastructure Group, SR Life Science Instrumentation Unit, Hyogo, Japan
| | - David J. Singh
- Materials Science and Technology Division, Oak Ridge National Laboratory, TN, USA
| | - Takatsugu Masuda
- Tokyo Neutron Science Laboratory, Institute for Solid State Physics, the University of Tokyo, Shirakata, Tokai, Japan
| | - Masahiro Yamamoto
- Department of Chemistry of Functional Molecules, Faculty of Science and Engineering, Konan University, Kobe, Japan
| | - Tsutomu Urano
- Yokohama City University, Graduate School, Yokohama, Japan
| | - Keiichiro Yoshida
- Department of Histology and Cell Biology, Yokohama City University School of Medicine, Yokohama, Japan
| | - Katsumi Tanigaki
- WPI-AIMR & Department of Physics, Graduate School of Science, Tohoku University, Sendai, Japan
| | - Masaki Yamamoto
- RIKEN, Research Infrastructure Group, SR Life Science Instrumentation Unit, Hyogo, Japan
| | - Mamoru Sato
- Structural Biology Laboratory, Graduate School of Medical Life Science, Yokohama City University, Yokohama, Japan
| | - Seiichi Inoue
- Department of Environment and Natural Sciences, Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama, Japan
| | - Ichio Aoki
- Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Yoshihiro Ishikawa
- Cardiovascular Research Institute, Yokohama City University, Graduate School of Medicine, Yokohama, Japan,
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Kouass Sahbani S, Sanche L, Cloutier P, Bass AD, Hunting DJ. Loss of cellular transformation efficiency induced by DNA irradiation with low-energy (10 eV) electrons. J Phys Chem B 2014; 118:13123-31. [PMID: 25325149 DOI: 10.1021/jp508170c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Low energy electrons (LEEs) of energies less than 20 eV are generated in large quantities by ionizing radiation in biological matter. While LEEs are known to induce single (SSBs) and double strand breaks (DSBs) in DNA, their ability to inactivate cells by inducing nonreparable lethal damage has not yet been demonstrated. Here we observe the effect of LEEs on the functionality of DNA, by measuring the efficiency of transforming Escherichia coli with a [pGEM-3Zf (-)] plasmid irradiated with 10 eV electrons. Highly ordered DNA films were prepared on pyrolitic graphite by molecular self-assembly using 1,3-diaminopropane ions (Dap(2+)). The uniformity of these films permits the inactivation of approximately 50% of the plasmids compared to <10% using previous methods, which is sufficient for the subsequent determination of their functionality. Upon LEE irradiation, the fraction of functional plasmids decreased exponentially with increasing electron fluence, while LEE-induced isolated base damage, frank DSB, and non DSB-cluster damage increased linearly with fluence. While DSBs can be toxic, their levels were too low to explain the loss of plasmid functionality observed upon LEE irradiation. Similarly, non-DSB cluster damage, revealed by transforming cluster damage into DSBs by digestion with repair enzymes, also occurred relatively infrequently. The exact nature of the lethal damage remains unknown, but it is probably a form of compact cluster damage in which the lesions are too close to be revealed by purified repair enzymes. In addition, this damage is either not repaired or is misrepaired by E. coli, since it results in plasmid inactivation, when they contain an average of three lesions. Comparison with previous results from a similar experiment performed with γ-irradiated plasmids indicates that the type of clustered DNA lesions, created directly on cellular DNA by LEEs, may be more difficult to repair than those produced by other species from radiolysis.
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Affiliation(s)
- Saloua Kouass Sahbani
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke , Sherbrooke, Quebec, Canada J1H 5N4
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6
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Bao Q, Chen Y, Zheng Y, Sanche L. Cisplatin Radiosensitization of DNA Irradiated with 2-20 eV Electrons: Role of Transient Anions. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2014; 118:15516-15524. [PMID: 26793285 PMCID: PMC4716812 DOI: 10.1021/jp503706h] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Platinum chemotherapeutic agents, such as cisplatin (cis-diamminedichloroplatinum(II)), can act as radiosensitizers when bound covalently to nuclear DNA in cancer cells. This radiosensitization is largely due to an increase in DNA damage induced by low-energy secondary electrons, produced in large quantities by high-energy radiation. We report the yields of single- and double-strand breaks (SSB and DSB) and interduplex cross-links (CL) induced by electrons of 1.6-19.6 eV (i.e., the yield functions) incident on 5 monolayer (ML) films of cisplatin-DNA complexes. These yield functions are compared with those previously recorded with 5 ML films of unmodified plasmid DNA. Binding of five cisplatin molecules to plasmid DNA (3197 base pairs) enhances SSB, DSB, and CL by factors varying, from 1.2 to 2.8, 1.4 to 3.5, and 1.2 to 2.7, respectively, depending on electron energy. All yield functions exhibit structures around 5 and 10 eV that can be attributed to enhancement of bond scission, via the initial formation of core-excited resonances associated with π → π* transitions of the bases. This increase in damage is interpreted as arising from a modification of the parameters of the corresponding transient anions already present in nonmodified DNA, particularly those influencing molecular dissociation. Two additional resonances, specific to cisplatin-modified DNA, are formed at 13.6 and 17.6 eV in the yield function of SSB. Furthermore, cisplatin binding causes the induction of DSB by electrons of 1.6-3.6 eV, i.e., in an energy region where a DSB cannot be produced by a single electron in pure DNA. Breaking two bonds with a subexcitation-energy electron is tentatively explained by a charge delocalization mechanism, where a single electron occupies simultaneously two σ* bonds linking the Pt atom to guanine bases on opposite strands.
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Affiliation(s)
- Qianhong Bao
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China
| | - Yunfeng Chen
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China
| | - Yi Zheng
- Research Institute of Photocatalysis, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou 350002, P. R. China
| | - Léon Sanche
- Group in the Radiation Sciences, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4
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Kouass Sahbani S, Rezaee M, Cloutier P, Sanche L, Hunting DJ. Non-DSB clustered DNA lesions induced by ionizing radiation are largely responsible for the loss of plasmid DNA functionality in the presence of cisplatin. Chem Biol Interact 2014; 217:9-18. [PMID: 24732435 DOI: 10.1016/j.cbi.2014.04.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 03/18/2014] [Accepted: 04/03/2014] [Indexed: 10/25/2022]
Abstract
The combination of cisplatin and ionizing radiation (IR) increases cell toxicity by both enhancing DNA damage and inhibiting repair mechanisms. Although the formation of cluster DNA lesions, particularly double-strand breaks (DSB) at the site of cisplatin-DNA-adducts has been reported to induce cell death, the contribution of DSB and non-DSB cluster lesions to the cellular toxicity is still unknown. Although both lesions are toxic, it is not always possible to measure their frequency and cell survival in the same model system. To overcome this problem, here, we investigate the effect of cisplatin-adducts on the induction of DSB and non-DSB cluster DNA lesions by IR and determine the impact of such lesions on plasmid functionality. Cluster lesions are two or more lesions on opposite DNA strands with a short distance such that error free repair is difficult or impossible. At a ratio of two cisplatin per plasmid, irradiation of platinated DNA in solution with (137)Cs γ-rays shows enhancements in the formation of DNA DSB and non-DSB cluster lesions by factors of 2.6 and 2.1, respectively, compared to unmodified DNA. However, in absolute terms, the yield for non-DSB cluster lesions is far larger than that for DSB, by a factor of 26. Unmodified and cisplatin-modified DNA were irradiated and subsequently transformed into Escherichia coli to give survival curves representing the functionality of the plasmid DNA as a function of radiation dose. Our results demonstrate that non-DSB cluster lesions are the only toxic lesions present at a sufficient frequency to account for the loss of DNA functionality. Our data also show that Frank-DSB lesions are simply too infrequent to account for the loss of DNA functionality. In conclusion, non-DSB cluster DNA damage is known to be difficult to repair and is probably the lesion responsible for the loss of functionality of DNA modified by cisplatin.
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Affiliation(s)
- S Kouass Sahbani
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada.
| | - M Rezaee
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - P Cloutier
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - L Sanche
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - D J Hunting
- Department of Nuclear Medicine & Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
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8
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Saloua KS, Sonia G, Pierre C, Léon S, Darel HJ. The relative contributions of DNA strand breaks, base damage and clustered lesions to the loss of DNA functionality induced by ionizing radiation. Radiat Res 2014; 181:99-110. [PMID: 24397439 DOI: 10.1667/rr13450.1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The majority of studies on lethal radiobiological damage have focused on double-strand breaks (DSBs), a type of clustered DNA damage and the evaluation of their toxicity, while other types of clustered DNA damage have received much less attention. The main purpose of this study is to evaluate the contribution of different lesions induced by ionizing radiation to the loss of plasmid DNA functionality. We employed a simple model system comprising E. coli transformed with an irradiated plasmid [pGEM-3Zf (-)] to determine the effect of DSBs and other lesions including base damage and clustered lesions on the functionality ("viability") of the plasmid. The yields of γ-radiation-induced single-strand breaks (SSBs) and DSBs were measured by gel electrophoresis. We found that the transformation efficiency decreases with radiation dose, but this decrease cannot be explained by the formation of DSBs. For example, at doses of 500 and 700 Gy, the relative transformation efficiency falls from 100% to 53% and 26%, respectively, while only 5.7% and 9.1% of the plasmids contain a DSB. In addition, it is also unlikely that randomly distributed base lesions could explain the loss of functionality of the plasmid, since cells can repair them efficiently. However, clustered lesions other than DSBs, which are difficult to repair and result in the loss of information on both DNA strands, have the potential to induce the loss of plasmid functionality. We therefore measured the yields of γ-radiation-induced base lesions and cluster damage, which are respectively converted into SSBs and DSBs by the base excision repair enzymes endonuclease III (Nth) and formamidopyrimidine-DNA glycosylase (Fpg). Our data demonstrate that the yield of cluster damage (i.e., lesions that yield DSBs following digestion) is 31 times higher than that of frank DSBs. This finding suggests that frank DSBs make a relatively minor contribution to the loss of DNA functionality induced by ionizing radiation, while other toxic lesions formed at a much higher frequencies than DSBs must be responsible for the loss of plasmid functionality. These lesions may be clustered lesions/locally multiply damaged sites (LMDS), including base damage, SSBs and/or intrastrand and interstrand crosslinks, leading to the loss of vital information in the DNA. Using a mathematical model, we estimate that at least three toxic lesions are required for the inactivation of plasmid functionality, in part because even these complex lesions can be repaired.
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Affiliation(s)
- Kouass Sahbani Saloua
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4
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Rezaee M, Hunting DJ, Sanche L. New insights into the mechanism underlying the synergistic action of ionizing radiation with platinum chemotherapeutic drugs: the role of low-energy electrons. Int J Radiat Oncol Biol Phys 2013; 87:847-53. [PMID: 23910707 DOI: 10.1016/j.ijrobp.2013.06.2037] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 05/12/2013] [Accepted: 06/13/2013] [Indexed: 10/26/2022]
Abstract
PURPOSE To investigate the efficiencies of platinum chemotherapeutic drugs (Pt-drugs) in the sensitization of DNA to the direct effects of ionizing radiation and to determine the role of low-energy electrons (LEEs) in this process. METHODS AND MATERIALS Complexes of supercoiled plasmid DNA covalently bound to either cisplatin, carboplatin, or oxaliplatin were prepared in different molar ratios. Solid films of DNA and DNA modified by Pt-drugs were irradiated with either 10-KeV or 10-eV electrons. Damages to DNA were quantified by gel electrophoresis, and the yields for damage formation were obtained from exposure-response curves. RESULTS The presence of an average of 2 Pt-drug-DNA adducts (Pt-adducts) in 3199-bp plasmid DNA increases the probability of a double-strand break by factors of 3.1, 2.5, and 2.4 for carboplatin, cisplatin, and oxaliplatin, respectively. Electrons with energies of 10 eV and 10 KeV interact with Pt-adducts to preferentially enhance the formation of cluster lesions. The maximum increase in radiosensitivity per Pt-adduct is found at ratios up to 3.1×10(-4) Pt-adducts per nucleotide, which is equivalent to an average of 2 adducts per plasmid. Carboplatin and oxaliplatin show higher efficiencies than cisplatin in the radiosensitization of DNA. Because carboplatin and cisplatin give rise to identical reactive species that attach to DNA, carboplatin must be considered as a better radiosensitizer for equal numbers of Pt-adducts. CONCLUSION Platinum chemotherapeutic drugs preferentially enhance the formation of cluster damage to DNA induced by the direct effect of ionizing radiation, and LEEs are the main species responsible for such an enhancement via the formation of electron resonances.
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Affiliation(s)
- Mohammad Rezaee
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, QC, Canada.
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Rezaee M, Sanche L, Hunting DJ. Cisplatin enhances the formation of DNA single- and double-strand breaks by hydrated electrons and hydroxyl radicals. Radiat Res 2013; 179:323-31. [PMID: 23368416 DOI: 10.1667/rr3185.1] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The synergistic interaction of cisplatin with ionizing radiation is the clinical rationale for the treatment of several cancers including head and neck, cervical and lung cancer. The underlying molecular mechanism of the synergy has not yet been identified, although both DNA damage and repair processes are likely involved. Here, we investigate the indirect effect of γ rays on strand break formation in a supercoiled plasmid DNA (pGEM-3Zf-) covalently modified by cisplatin. The yields of single- and double-strand breaks were determined by irradiation of DNA and cisplatin/DNA samples with (60)Co γ rays under four different scavenging conditions to examine the involvement of hydrated electrons and hydroxyl radicals in inducing the DNA damage. At 5 mM tris in an N2 atmosphere, the presence of an average of two cisplatins per plasmid increased the yields of single- and double-strand breaks by factors of 1.9 and 2.2, respectively, relative to the irradiated unmodified DNA samples. Given that each plasmid of 3,200 base pairs contained an average of two cisplatins, this represents an increase in radiosensitivity of 3,200-fold on a per base pair basis. When hydrated electrons were scavenged by saturating the samples with N2O, these enhancement factors decreased to 1.5 and 1.2, respectively, for single- and double-strand breaks. When hydroxyl radicals were scavenged using 200 mM tris, the respective enhancement factors were 1.2 and 1.6 for single- and double-strand breaks, respectively. Furthermore, no enhancement in DNA damage by cisplatin was observed after scavenging both hydroxyl radicals and hydrated electrons. These findings show that hydrated electrons can induce both single- and double-strand breaks in the platinated DNA, but not in unmodified DNA. In addition, cisplatin modification is clearly an extremely efficient means of increasing the formation of both single- and double-strand breaks by the hydrated electrons and hydroxyl radicals created by ionizing radiation.
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Affiliation(s)
- Mohammad Rezaee
- Groupe en Sciences des Radiations, Départment de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada.
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Alizadeh E, Sanche L. Precursors of solvated electrons in radiobiological physics and chemistry. Chem Rev 2012; 112:5578-602. [PMID: 22724633 DOI: 10.1021/cr300063r] [Citation(s) in RCA: 225] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elahe Alizadeh
- Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Canada
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