1
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Falkiewicz K, Kozak W, Zdrowowicz M, Spisz P, Chomicz-Mańka L, Torchala M, Rak J. Why 6-Iodouridine Cannot Be Used as a Radiosensitizer of DNA Damage? Computational and Experimental Studies. J Phys Chem B 2023; 127:2565-2574. [PMID: 36893332 PMCID: PMC10041638 DOI: 10.1021/acs.jpcb.3c00548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Previous density functional theory (DFT) studies on 6-brominated pyrimidine nucleosides suggest that 6-iodo-2'-deoxyuridine (6IdU) should act as a better radiosensitizer than its 5-iodosubstituted 2'-deoxyuridine analogue. In this work, we show that 6IdU is unstable in an aqueous solution. Indeed, a complete disappearance of the 6IdU signal was observed during its isolation by reversed-phase high-performance liquid chromatography (RP-HPLC). As indicated by the thermodynamic characteristics for the SN1-type hydrolysis of 6IdU obtained at the CAM-B3LYP/DGDZVP++ level and the polarizable continuum model (PCM) of water, 6-iodouracil (6IU) was already released quantitatively at ambient temperatures. The simulation of the hydrolysis kinetics demonstrated that a thermodynamic equilibrium was reached within seconds for the title compound. To assess the reliability of the calculations carried out, we synthesized 6-iodouridine (6IUrd), which was, unlike 6IdU, sufficiently stable in an aqueous solution at room temperature. The activation barrier for the N-glycosidic bond dissociation in 6IUrd was estimated experimentally using an Arrhenius plot. The stabilities in water calculated for 6IdU, 6IUrd, and 5-iodo-2'-deoxyuridine (5IdU) could be explained by the electronic and steric effects of the 2'-hydroxy group present in the ribose moiety. Our studies highlight the issue of the hydrolytic stability of potentially radiosensitizing nucleotides which, besides having favorable dissociative electron attachment (DEA) characteristics, must be stable in water to have any practical application.
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Affiliation(s)
- Karina Falkiewicz
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Witold Kozak
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Magdalena Zdrowowicz
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Paulina Spisz
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
- Laboratory of Intermolecular Interactions, Department of Bioinorganic Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Lidia Chomicz-Mańka
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Mieczyslaw Torchala
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Janusz Rak
- Laboratory of Biological Sensitizers, Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
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2
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Ramotowska S, Spisz P, Brzeski J, Ciesielska A, Makowski M. Application of the SwitchSense Technique for the Study of Small Molecules’ (Ethidium Bromide and Selected Sulfonamide Derivatives) Affinity to DNA in Real Time. J Phys Chem B 2022; 126:7238-7251. [PMID: 36106569 PMCID: PMC9527753 DOI: 10.1021/acs.jpcb.2c03138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The discovery and introduction of the switchSense technique
in
the chemical laboratory have drawn well-deserved interest owing to
its wide range of applications. Namely, it can be used to determine
the diameter of proteins, alterations in their tertiary structures
(folding), and many other conformational changes that are important
from a biological point of view. The essence of this technique is
based on its ability to study of the interactions between an analyte
and a ligand in real time (in a buffer flow). Its simplicity, on the
other hand, is based on the use of a signaling system that provides
information about the ongoing interactions based on the changes in
the fluorescence intensity. This technique can be extremely advantageous
in the study of new pharmaceuticals. The design of compounds with
biological activity, as well as the determination of their molecular
targets and modes of interactions, is crucial in the search for new
drugs and the fight against drug resistance. This article presents
another possible application of the switchSense technique for the
study of the binding kinetics of small model molecules such as ethidium
bromide (EB) and selected sulfonamide derivatives with DNA in the
static and dynamic modes at three different temperatures (15, 25,
and 37 °C) each. The experimental results remain in very good
agreement with the molecular dynamics docking ones. These physicochemical
insights and applications obtained from the switchSense technique
allow for the design of an effective strategy for molecular interaction
assessments of small but pharmaceutically important molecules with
DNA.
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Affiliation(s)
- Sandra Ramotowska
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Paulina Spisz
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, Gdańsk 80-308, Poland
| | - Jakub Brzeski
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, Gdańsk 80-308, Poland
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | | | - Mariusz Makowski
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, Gdańsk 80-308, Poland
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3
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Zdrowowicz M, Spisz P, Hać A, Herman-Antosiewicz A, Rak J. Influence of Hypoxia on Radiosensitization of Cancer Cells by 5-Bromo-2'-deoxyuridine. Int J Mol Sci 2022; 23:ijms23031429. [PMID: 35163354 PMCID: PMC8836255 DOI: 10.3390/ijms23031429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 01/25/2022] [Accepted: 01/25/2022] [Indexed: 12/12/2022] Open
Abstract
Radiotherapy is a crucial cancer treatment, but its outcome is still far from satisfactory. One of the reasons that cancer cells show resistance to ionizing radiation is hypoxia, defined as a low level of oxygenation, which is typical for solid tumors. In the hypoxic environment, cancer cells are 2–3 times more resistant to ionizing radiation than normoxic cells. To overcome this important impediment, radiosensitizers should be introduced to cancer therapy. When modified with an electrophilic substituent, nucleosides may undergo efficient dissociative electron attachment (DEA) that leaves behind nucleoside radicals, which, in secondary reactions, are able to induce DNA damage, leading to cancer cell death. We report the radiosensitizing effect of one of the best-known DEA-type radiosensitizers—5-bromo-2′-deoxyuridine (BrdU)—on breast (MCF-7) and prostate (PC3) cancer cells under both normoxia and hypoxia. MCF-7 and PC3 cells were treated with BrdU to investigate the effect of hypoxia on cell proliferation, incorporation into DNA and radiosensitivity. While the oxygen concentration did not significantly affect the efficiency of BrdU incorporation into DNA or the proliferation of tumor cells, the radiosensitizing effect of BrdU on hypoxic cells was more evident than on normoxic cells. Further mechanistic studies performed with the use of flow cytometry showed that under hypoxia, BrdU increased the level of histone H2A.X phosphorylation after X-ray exposure to a greater extent than under normal oxygenation conditions. These results confirm that the formation of double-strand breaks in hypoxic BrdU-treated cancer cells is more efficient. In addition, by performing stationary radiolysis of BrdU solution in the presence of an ●OH radical scavenger, we compared the degree of its electron-induced degradation under aerobic and anaerobic conditions. It was determined that radiodegradation under anaerobic conditions was almost twice as high as that under aerobic conditions.
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Affiliation(s)
- Magdalena Zdrowowicz
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland; (M.Z.); (P.S.)
| | - Paulina Spisz
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland; (M.Z.); (P.S.)
| | - Aleksandra Hać
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdansk, 80-308 Gdańsk, Poland; (A.H.); (A.H.-A.)
| | - Anna Herman-Antosiewicz
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdansk, 80-308 Gdańsk, Poland; (A.H.); (A.H.-A.)
| | - Janusz Rak
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland; (M.Z.); (P.S.)
- Correspondence: ; Tel.: +48-58-523-51-18
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4
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Szabla R, Zdrowowicz M, Spisz P, Green NJ, Stadlbauer P, Kruse H, Šponer J, Rak J. 2,6-diaminopurine promotes repair of DNA lesions under prebiotic conditions. Nat Commun 2021; 12:3018. [PMID: 34021158 PMCID: PMC8139960 DOI: 10.1038/s41467-021-23300-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 04/20/2021] [Indexed: 01/04/2023] Open
Abstract
High-yielding and selective prebiotic syntheses of RNA and DNA nucleotides involve UV irradiation to promote the key reaction steps and eradicate biologically irrelevant isomers. While these syntheses were likely enabled by UV-rich prebiotic environment, UV-induced formation of photodamages in polymeric nucleic acids, such as cyclobutane pyrimidine dimers (CPDs), remains the key unresolved issue for the origins of RNA and DNA on Earth. Here, we demonstrate that substitution of adenine with 2,6-diaminopurine enables repair of CPDs with yields reaching 92%. This substantial self-repairing activity originates from excellent electron donating properties of 2,6-diaminopurine in nucleic acid strands. We also show that the deoxyribonucleosides of 2,6-diaminopurine and adenine can be formed under the same prebiotic conditions. Considering that 2,6-diaminopurine was previously shown to increase the rate of nonenzymatic RNA replication, this nucleobase could have played critical roles in the formation of functional and photostable RNA/DNA oligomers in UV-rich prebiotic environments. UV-induced photodamage that likely occurred during the prebiotic synthesis of DNA and RNA is still an untackled issue for their origin on early Earth. Here, the authors show that substitution of 2,6-diaminopurine for adenine enables repair of cyclobutane pyrimidine dimers with high yields, and demonstrate that both 2,6-diaminopurine and adenine nucleosides can be formed under the same prebiotic conditions.
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Affiliation(s)
- Rafał Szabla
- EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, UK. .,Institute of Physics, Polish Academy of Sciences, Warsaw, Poland.
| | | | - Paulina Spisz
- Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland
| | | | - Petr Stadlbauer
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Holger Kruse
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Jiří Šponer
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Janusz Rak
- Faculty of Chemistry, University of Gdańsk, Gdańsk, Poland
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5
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Spisz P, Kozak W, Chomicz-Mańka L, Makurat S, Falkiewicz K, Sikorski A, Czaja A, Rak J, Zdrowowicz M. 5-( N-Trifluoromethylcarboxy)aminouracil as a Potential DNA Radiosensitizer and Its Radiochemical Conversion into N-Uracil-5-yloxamic Acid. Int J Mol Sci 2020; 21:E6352. [PMID: 32883013 PMCID: PMC7504071 DOI: 10.3390/ijms21176352] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/18/2020] [Accepted: 08/28/2020] [Indexed: 01/01/2023] Open
Abstract
Hypoxia-a hallmark of solid tumors-dramatically impairs radiotherapy, one of the most common anticancer modalities. The adverse effect of the low-oxygen state can be eliminated by the concomitant use of a hypoxic cell radiosensitizer. In the present paper, we show that 5-(N-trifluoromethylcarboxy) aminouracil (CF3CONHU) can be considered as an effective radiosensitizer of DNA damage, working under hypoxia. The title compound was synthesized in the reaction of 5-aminouracil and trifluoroacetic anhydride in trifluoroacetic acid. Then, an aqueous and deoxygenated solution of the HPLC purified compound containing tert-butanol as a hydroxyl radical scavenger was irradiated with X-rays. Radiodegradation in a 26.67 ± 0.31% yield resulted in only one major product-N-uracil-5-yloxamic acid. The mechanism that is possibly responsible for the formation of the observed radioproduct has been elucidated with the use of DFT calculations. The cytotoxic test against the PC3 prostate cancer cell line and HDFa human dermal fibroblasts confirmed the low cytotoxicity of CF3CONHU. Finally, a clonogenic assay and flow cytometric analysis of histone H2A.X phosphorylation proved the radiosensitization in vitro.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Magdalena Zdrowowicz
- Department of Physical Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland; (P.S.); (W.K.); (L.C.-M.); (S.M.); (K.F.); (A.S.); (A.C.); (J.R.)
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6
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Spisz P, Zdrowowicz M, Kozak W, Chomicz-Mańka L, Falkiewicz K, Makurat S, Sikorski A, Wyrzykowski D, Rak J, Arthur-Baidoo E, Ziegler P, Rodrigues Costa MS, Denifl S. Uracil-5-yl O-Sulfamate: An Illusive Radiosensitizer. Pitfalls in Modeling the Radiosensitizing Derivatives of Nucleobases. J Phys Chem B 2020; 124:5600-5613. [PMID: 32539395 PMCID: PMC7356320 DOI: 10.1021/acs.jpcb.0c03844] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/12/2020] [Indexed: 12/16/2022]
Abstract
Efficient radiotherapy requires the concomitant use of ionizing radiation (IR) and a radiosensitizer. In the present work uracil-5-yl O-sulfamate (SU) is tested against its radiosensitizing potential. The compound possesses appropriate dissociative electron attachment (DEA) characteristics calculated at the M06-2X/6-31++G(d,p) level. Crossed electron-molecular beam experiments in the gas phase demonstrate that SU undergoes efficient DEA processes, and the single C-O or S-O bond dissociations account for the majority of fragments induced by electron attachment. Most DEAs proceed already for electrons with kinetic energies of ∼0 eV, which is supported by the exothermic thresholds calculated at the M06-2X/aug-cc-pVTZ level. However, in water solution under reductive conditions and physiological pH, SU does not undergo radiolysis, which demonstrates the crucial influence of aqueous environment on the radiosensitizing properties of modified nucleosides.
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Affiliation(s)
- Paulina Spisz
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Magdalena Zdrowowicz
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Witold Kozak
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Lidia Chomicz-Mańka
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Karina Falkiewicz
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Samanta Makurat
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Artur Sikorski
- Group
of Crystallochemistry, Physical Chemistry Department, Faculty of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Dariusz Wyrzykowski
- Group
of Physicochemistry and Complex Compounds, General and Inorganic Chemistry
Department, Faculty of Chemistry, University
of Gdańsk, 80-308 Gdańsk, Poland
| | - Janusz Rak
- Group
of Biological Sensitizers, Physical Chemistry Department, Faculty
of Chemistry, University of Gdańsk, 80-308 Gdańsk, Poland
| | - Eugene Arthur-Baidoo
- Institut
für Ionenphysik und Angewandte Physik and Center for Biomolecular
Sciences Innsbruck, Leopold-Franzens Universität
Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Patrick Ziegler
- Institut
für Ionenphysik und Angewandte Physik and Center for Biomolecular
Sciences Innsbruck, Leopold-Franzens Universität
Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - Mateus Salomao Rodrigues Costa
- Institut
für Ionenphysik und Angewandte Physik and Center for Biomolecular
Sciences Innsbruck, Leopold-Franzens Universität
Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - 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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7
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Spisz P, Zdrowowicz M, Makurat S, Kozak W, Skotnicki K, Bobrowski K, Rak J. Why Does the Type of Halogen Atom Matter for the Radiosensitizing Properties of 5-Halogen Substituted 4-Thio-2'-Deoxyuridines? Molecules 2019; 24:E2819. [PMID: 31382376 PMCID: PMC6695862 DOI: 10.3390/molecules24152819] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 07/30/2019] [Accepted: 07/31/2019] [Indexed: 01/06/2023] Open
Abstract
Radiosensitizing properties of substituted uridines are of great importance for radiotherapy. Very recently, we confirmed 5-iodo-4-thio-2'-deoxyuridine (ISdU) as an efficient agent, increasing the extent of tumor cell killing with ionizing radiation. To our surprise, a similar derivative of 4-thio-2'-deoxyuridine, 5-bromo-4-thio-2'-deoxyuridine (BrSdU), does not show radiosensitizing properties at all. In order to explain this remarkable difference, we carried out a radiolytic (stationary and pulse) and quantum chemical studies, which allowed the pathways to all radioproducts to be rationalized. In contrast to ISdU solutions, where radiolysis leads to 4-thio-2'-deoxyuridine and its dimer, no dissociative electron attachment (DEA) products were observed for BrSdU. This observation seems to explain the lack of radiosensitizing properties of BrSdU since the efficient formation of the uridine-5-yl radical, induced by electron attachment to the modified nucleoside, is suggested to be an indispensable attribute of radiosensitizing uridines. A larger activation barrier for DEA in BrSdU, as compared to ISdU, is probably responsible for the closure of DEA channel in the former system. Indeed, besides DEA, the XSdU anions may undergo competitive protonation, which makes the release of X- kinetically forbidden.
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Affiliation(s)
- Paulina Spisz
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Magdalena Zdrowowicz
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Samanta Makurat
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Witold Kozak
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
| | - Konrad Skotnicki
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland
| | - Krzysztof Bobrowski
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw, Poland
| | - Janusz Rak
- Laboratory of Biological Sensitizers, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
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8
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Makurat S, Spisz P, Kozak W, Rak J, Zdrowowicz M. 5-Iodo-4-thio-2'-Deoxyuridine as a Sensitizer of X-ray Induced Cancer Cell Killing. Int J Mol Sci 2019; 20:E1308. [PMID: 30875879 PMCID: PMC6470520 DOI: 10.3390/ijms20061308] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 03/12/2019] [Indexed: 12/21/2022] Open
Abstract
Nucleosides, especially pyrimidines modified in the C5-position, can act as radiosensitizers via a mechanism that involves their enzymatic triphosphorylation, incorporation into DNA, and a subsequent dissociative electron attachment (DEA) process. In this paper, we report 5-iodo-4-thio-2'-deoxyuridine (ISdU) as a compound that can effectively lead to ionizing radiation (IR)-induced cellular death, which is proven by a clonogenic assay. The test revealed that the survival of cells, pre-treated with 10 or 100 µM solution of ISdU and exposed to 0.5 Gy of IR, was reduced from 78.4% (for non-treated culture) to 67.7% and to 59.8%, respectively. For a somewhat higher dose of 1 Gy, the surviving fraction was reduced from 68.2% to 54.9% and to 40.8% for incubation with 10 or 100 µM ISdU, respectively. The cytometric analysis of histone H2A.X phosphorylation showed that the radiosensitizing effect of ISdU was associated, at least in part, with the formation of double-strand breaks. Moreover, the cytotoxic test against the MCF-7 breast cancer cell line and human dermal fibroblasts (HDFa line) confirmed low cytotoxic activity of ISdU. Based on the results of steady state radiolysis of ISdU with a dose of 140 Gy and quantum chemical calculations explaining the origin of the MS detected radioproducts, the molecular mechanism of sensitization by ISdU was proposed. In conclusion, we found ISdU to be a potential radiosensitizer that could improve anticancer radiotherapy.
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Affiliation(s)
- Samanta Makurat
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
| | - Paulina Spisz
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
| | - Witold Kozak
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
| | - Janusz Rak
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
| | - Magdalena Zdrowowicz
- Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
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