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Alatawneh N, Meijler MM. Unraveling the Antibacterial and Iron Chelating Activity of
N
‐Oxide Hydroxy‐Phenazine natural Products and Synthetic Analogs against
Staphylococcus Aureus. Isr J Chem 2023. [DOI: 10.1002/ijch.202200112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
Affiliation(s)
- Nadeem Alatawneh
- Department of Chemistry and The National Institute for Biotechnology in the Negev Ben-Gurion University of the Negev Be'er Sheva 84105 Israel
| | - Michael M. Meijler
- Department of Chemistry and The National Institute for Biotechnology in the Negev Ben-Gurion University of the Negev Be'er Sheva 84105 Israel
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2
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Spin Trapping Hydroxyl and Aryl Radicals of One-Electron Reduced Anticancer Benzotriazine 1,4-Dioxides. Molecules 2022; 27:molecules27030812. [PMID: 35164077 PMCID: PMC8840461 DOI: 10.3390/molecules27030812] [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: 12/15/2021] [Revised: 01/19/2022] [Accepted: 01/21/2022] [Indexed: 02/06/2023] Open
Abstract
Hypoxia in tumors results in resistance to both chemotherapy and radiotherapy treatments but affords an environment in which hypoxia-activated prodrugs (HAP) are activated upon bioreduction to release targeted cytotoxins. The benzotriazine 1,4-di-N-oxide (BTO) HAP, tirapazamine (TPZ, 1), has undergone extensive clinical evaluation in combination with radiotherapy to assist in the killing of hypoxic tumor cells. Although compound 1 did not gain approval for clinical use, it has spurred on the development of other BTOs, such as the 3-alkyl analogue, SN30000, 2. There is general agreement that the cytotoxin(s) from BTOs arise from the one-electron reduced form of the compounds. Identifying the cytotoxic radicals, and whether they play a role in the selective killing of hypoxic tumor cells, is important for continued development of the BTO class of anticancer prodrugs. In this study, nitrone spin-traps, combined with electron spin resonance, give evidence for the formation of aryl radicals from compounds 1, 2 and 3-phenyl analogues, compounds 3 and 4, which form carbon C-centered radicals. In addition, high concentrations of DEPMPO (5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide) spin-trap the •OH radical. The combination of spin-traps with high concentrations of DMSO and methanol also give evidence for the involvement of strongly oxidizing radicals. The failure to spin-trap methyl radicals with PBN (N-tert-butylphenylnitrone) on the bioreduction of compound 2, in the presence of DMSO, implies that free •OH radicals are not released from the protonated radical anions of compound 2. The spin-trapping of •OH radicals by high concentrations of DEPMPO, and the radical species arising from DMSO and methanol give both direct and indirect evidence for the scavenging of •OH radicals that are involved in an intramolecular process. Hypoxia-selective cytotoxicity is not related to the formation of aryl radicals from the BTO compounds as they are associated with high aerobic cytotoxicity.
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3
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Li Y, Zhao L, Li XF. Targeting Hypoxia: Hypoxia-Activated Prodrugs in Cancer Therapy. Front Oncol 2021; 11:700407. [PMID: 34395270 PMCID: PMC8358929 DOI: 10.3389/fonc.2021.700407] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 07/09/2021] [Indexed: 12/18/2022] Open
Abstract
Hypoxia is an important characteristic of most solid malignancies, and is closely related to tumor prognosis and therapeutic resistance. Hypoxia is one of the most important factors associated with resistance to conventional radiotherapy and chemotherapy. Therapies targeting tumor hypoxia have attracted considerable attention. Hypoxia-activated prodrugs (HAPs) are bioreductive drugs that are selectively activated under hypoxic conditions and that can accurately target the hypoxic regions of solid tumors. Both single-agent and combined use with other drugs have shown promising antitumor effects. In this review, we discuss the mechanism of action and the current preclinical and clinical progress of several of the most widely used HAPs, summarize their existing problems and shortcomings, and discuss future research prospects.
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Affiliation(s)
- Yue Li
- Department of Nuclear Medicine, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen, China.,The First Affiliated Hospital, Jinan University, Guangzhou, China.,Department of Nuclear Medicine, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen, China
| | - Long Zhao
- Department of Nuclear Medicine, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen, China.,Department of Nuclear Medicine, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen, China
| | - Xiao-Feng Li
- Department of Nuclear Medicine, The Second Clinical Medical College, Jinan University (Shenzhen People's Hospital), Shenzhen, China.,Department of Nuclear Medicine, The First Affiliated Hospital of Southern University of Science and Technology, Shenzhen, China
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4
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Karan S, Cho MY, Lee H, Lee H, Park HS, Sundararajan M, Sessler JL, Hong KS. Near-Infrared Fluorescent Probe Activated by Nitroreductase for In Vitro and In Vivo Hypoxic Tumor Detection. J Med Chem 2021; 64:2971-2981. [PMID: 33711229 DOI: 10.1021/acs.jmedchem.0c02162] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Tumor hypoxia is correlated with increased resistance to chemotherapy and poor overall prognoses across a number of cancer types. We present here a cancer cell-selective and hypoxia-responsive probe (fol-BODIPY) designed on the basis of density functional theory (DFT)-optimized quantum chemical calculations. The fol-BODIPY probe was found to provide a rapid fluorescence "off-on" response to hypoxia relative to controls, which lack the folate or nitro-benzyl moieties. In vitro confocal microscopy and flow cytometry analyses, as well as in vivo near-infrared optical imaging of CT26 solid tumor-bearing mice, provided support for the contention that fol-BODIPY is more readily accepted by folate receptor-positive CT26 cancer cells and provides a superior fluorescence "off-on" signal under hypoxic conditions than the controls. Based on the findings of this study, we propose that fol-BODIPY may serve as a tumor-targeting, hypoxia-activatable probe that allows for direct cancer monitoring both in vitro and in vivo.
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Affiliation(s)
- Sanu Karan
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea
- Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Mi Young Cho
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea
| | - Hyunseung Lee
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea
| | - Hwunjae Lee
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea
| | - Hye Sun Park
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea
| | - Mahesh Sundararajan
- Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai 400 085, India
| | - Jonathan L Sessler
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712-1224, United States
| | - Kwan Soo Hong
- Research Center for Bioconvergence Analysis, Korea Basic Science Institute, Cheongju 28119, Republic of Korea
- Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon 34134, Republic of Korea
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5
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Rivera G. Quinoxaline 1,4-di-N-Oxide Derivatives: Are They Unselective or Selective Inhibitors? Mini Rev Med Chem 2021; 22:15-25. [PMID: 33573542 DOI: 10.2174/1389557521666210126142541] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/07/2020] [Accepted: 12/07/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND For decades, the quinoxaline 1,4-di-N-oxide ring has been considered a privileged structure to develop new antibacterial, antitumoural, and antiprotozoal agents, among others, however its mechanism of action is not clear. OBJECTIVE The main aim of this mini-review was to analyze the mechanism of action of quinoxaline 1,4-di-N-oxide derivatives reported as antibacterial, antitumoural and antiprotozoal agents. RESULTS Initially, the mechanism of action of quinoxaline 1,4-di-N-oxide derivatives against bacteria, tumoural cell lines, and parasites has been described as nonspecific, but recently, the results against different organisms have shown that these compounds have an inhibitory action on specific targets such as trypanothione reductase, triosephosphate isomerase, and other essential enzymes. CONCLUSION In summary, quinoxaline 1,4-di-N-oxide is a scaffold to develop new anti-Mycobacterium tuberculosis, antitumoural and antiprotozoal agents, however, understanding the mechanism of action of quinoxaline 1,4-di-N-oxide derivatives in each microorganism could contribute to the development of new, and more potent selective drugs.
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Affiliation(s)
- Gildardo Rivera
- Laboratorio de Biotecnología Farmacéutica, Centro de Biotecnología Genómica, Instituto Politécnico Nacional, 88710 Reynosa. Mexico
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6
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Subcellular Location of Tirapazamine Reduction Dramatically Affects Aerobic but Not Anoxic Cytotoxicity. Molecules 2020; 25:molecules25214888. [PMID: 33105798 PMCID: PMC7660101 DOI: 10.3390/molecules25214888] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 10/20/2020] [Accepted: 10/20/2020] [Indexed: 11/16/2022] Open
Abstract
Hypoxia is an adverse prognostic feature of solid cancers that may be overcome with hypoxia-activated prodrugs (HAPs). Tirapazamine (TPZ) is a HAP which has undergone extensive clinical evaluation in this context and stimulated development of optimized analogues. However the subcellular localization of the oxidoreductases responsible for mediating TPZ-dependent DNA damage remains unclear. Some studies conclude only nuclear-localized oxidoreductases can give rise to radical-mediated DNA damage and thus cytotoxicity, whereas others identify a broader role for endoplasmic reticulum and cytosolic oxidoreductases, indicating the subcellular location of TPZ radical formation is not a critical requirement for DNA damage. To explore this question in intact cells we engineered MDA-231 breast cancer cells to express the TPZ reductase human NADPH: cytochrome P450 oxidoreductase (POR) harboring various subcellular localization sequences to guide this flavoenzyme to the nucleus, endoplasmic reticulum, cytosol or inner surface of the plasma membrane. We show that all POR variants are functional, with differences in rates of metabolism reflecting enzyme expression levels rather than intracellular TPZ concentration gradients. Under anoxic conditions, POR expression in all subcellular compartments increased the sensitivity of the cells to TPZ, but with a fall in cytotoxicity per unit of metabolism (termed ‘metabolic efficiency’) when POR is expressed further from the nucleus. However, under aerobic conditions a much larger increase in cytotoxicity was observed when POR was directed to the nucleus, indicating very high metabolic efficiency. Consequently, nuclear metabolism results in collapse of hypoxic selectivity of TPZ, which was further magnified to the point of reversing O2 dependence (oxic > hypoxic sensitivity) by employing a DNA-affinic TPZ analogue. This aerobic hypersensitivity phenotype was partially rescued by cellular copper depletion, suggesting the possible involvement of Fenton-like chemistry in generating short-range effects mediated by the hydroxyl radical. In addition, the data suggest that under aerobic conditions reoxidation strictly limits the TPZ radical diffusion range resulting in site-specific cytotoxicity. Collectively these novel findings challenge the purported role of intra-nuclear reductases in orchestrating the hypoxia selectivity of TPZ.
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Kaneda S, Kawada J, Shinohara M, Kumemura M, Ueno R, Kawamoto T, Suzuki K, Kim B, Ikeuchi Y, Sakai Y, Collard D, Fujita H, Fujii T. Boyden chamber-based compartmentalized tumor spheroid culture system to implement localized anticancer drug treatment. BIOMICROFLUIDICS 2019; 13:054111. [PMID: 31893010 PMCID: PMC6932857 DOI: 10.1063/1.5125650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 10/04/2019] [Indexed: 06/10/2023]
Abstract
In anticancer drug development, it is important to simultaneously evaluate both the effect of drugs on cell proliferation and their ability to penetrate tissues. To realize such an evaluation process, here, we present a compartmentalized tumor spheroid culture system utilizing a thin membrane with a through-hole to conduct localized anticancer treatment of tumor spheroids and monitor spheroid dimensions as an indicator of cell proliferation. The system is based on a commercialized Boyden chamber plate; a through-hole was bored through a porous membrane of the chamber, and the pre-existing 0.4 μm membrane pores were filled with parylene C. A HepG2 spheroid was immobilized onto the through-hole, separating the upper and lower compartments. Fluorescein (to verify the isolation between the compartments) and tirapazamine (TPZ; to treat only the lower part of the spheroid) were added to the upper and lower compartments, respectively. Since the transportation of fluorescein was blocked during treatment, i.e., the upper and lower compartments were isolated, it was confirmed that localized TPZ treatment was successfully conducted using the developed system. The effect of localized TPZ treatment on cell proliferation was estimated by measuring the maximum horizontal cross-sectional areas in the upper and lower parts of the spheroid by microscopic observations. This system can, thus, be used to perform localized anticancer drug treatment of tumor spheroids and evaluate the effect of drugs on cell proliferation.
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Affiliation(s)
- Shohei Kaneda
- Authors to whom correspondence should be addressed: and
| | - Jiro Kawada
- Center for International Research on Integrative Biomedical Systems, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 156-0041, Japan
| | - Marie Shinohara
- Center for International Research on Integrative Biomedical Systems, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 156-0041, Japan
| | | | - Ryohei Ueno
- LIMMS-CNRS/IIS, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 156-0041, Japan
| | - Tomoaki Kawamoto
- Department of Mechanical Systems Engineering, Faculty of Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji-shi, Tokyo 192-0015, Japan
| | - Kenji Suzuki
- Department of Mechanical Systems Engineering, Faculty of Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji-shi, Tokyo 192-0015, Japan
| | | | | | | | - Dominique Collard
- LIMMS-CNRS/IIS, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 156-0041, Japan
| | - Hiroyuki Fujita
- Center for Interdisciplinary Research on Micro-Nano Methods, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 156-0041, Japan
| | - Teruo Fujii
- Center for International Research on Integrative Biomedical Systems, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 156-0041, Japan
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Hay MP, Shin HN, Wong WW, Sahimi WW, Vaz ATD, Yadav P, Anderson RF, Hicks KO, Wilson WR. Benzotriazine Di-Oxide Prodrugs for Exploiting Hypoxia and Low Extracellular pH in Tumors. Molecules 2019; 24:E2524. [PMID: 31295864 PMCID: PMC6680510 DOI: 10.3390/molecules24142524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 07/05/2019] [Accepted: 07/06/2019] [Indexed: 12/31/2022] Open
Abstract
Extracellular acidification is an important feature of tumor microenvironments but has yet to be successfully exploited in cancer therapy. The reversal of the pH gradient across the plasma membrane in cells that regulate intracellular pH (pHi) has potential to drive the selective uptake of weak acids at low extracellular pH (pHe). Here, we investigate the dual targeting of low pHe and hypoxia, another key feature of tumor microenvironments. We prepared eight bioreductive prodrugs based on the benzotriazine di-oxide (BTO) nucleus by appending alkanoic or aminoalkanoic acid sidechains. The BTO acids showed modest selectivity for both low pHe (pH 6.5 versus 7.4, ratios 2 to 5-fold) and anoxia (ratios 2 to 8-fold) in SiHa and FaDu cell cultures. Related neutral BTOs were not selective for acidosis, but had greater cytotoxic potency and hypoxic selectivity than the BTO acids. Investigation of the uptake and metabolism of representative BTO acids confirmed enhanced uptake at low pHe, but lower intracellular concentrations than expected for passive diffusion. Further, the modulation of intracellular reductase activity and competition by the cell-excluded electron acceptor WST-1 suggests that the majority of metabolic reductions of BTO acids occur at the cell surface, compromising the engagement of the resulting free radicals with intracellular targets. Thus, the present study provides support for designing bioreductive prodrugs that exploit pH-dependent partitioning, suggesting, however, that that the approach should be applied to prodrugs with obligate intracellular activation.
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Affiliation(s)
- Michael P Hay
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Symonds St, Auckland 1142, New Zealand
| | - Hong Nam Shin
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Way Wua Wong
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Wan Wan Sahimi
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Aaron T D Vaz
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Pooja Yadav
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Robert F Anderson
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Symonds St, Auckland 1142, New Zealand
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Kevin O Hicks
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Symonds St, Auckland 1142, New Zealand
| | - William R Wilson
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Symonds St, Auckland 1142, New Zealand.
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Shen X, Gates KS. Enzyme-Activated Generation of Reactive Oxygen Species from Heterocyclic N-Oxides under Aerobic and Anaerobic Conditions and Its Relevance to Hypoxia-Selective Prodrugs. Chem Res Toxicol 2019; 32:348-361. [PMID: 30817135 DOI: 10.1021/acs.chemrestox.9b00036] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Enzymatic one-electron reduction of heterocyclic N-oxides can lead to the intracellular generation of reactive oxygen species via several different chemical pathways. These reactions may be relevant to hypoxia-selective anticancer drugs, antimicrobial agents, and unwanted toxicity of heterocylic nitrogen compounds.
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Jackson RK, Liew LP, Hay MP. Overcoming Radioresistance: Small Molecule Radiosensitisers and Hypoxia-activated Prodrugs. Clin Oncol (R Coll Radiol) 2019; 31:290-302. [PMID: 30853148 DOI: 10.1016/j.clon.2019.02.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 02/12/2019] [Indexed: 12/25/2022]
Abstract
The role of hypoxia in radiation resistance is well established and many approaches to overcome hypoxia in tumours have been explored, with variable success. Two small molecule strategies for targeting hypoxia have dominated preclinical and clinical efforts. One approach has been the use of electron-affinic nitroheterocycles as oxygen-mimetic sensitisers. These agents are best exemplified by the 5-nitroimidazole nimorazole, which has limited use in conjunction with radiotherapy in head and neck squamous cell carcinoma. The second approach seeks to leverage tumour hypoxia as a tumour-specific address for hypoxia-activated prodrugs. These prodrugs are selectively activated by reductases under hypoxia to release cytotoxins, which in some instances may diffuse to kill surrounding oxic tumour tissue. A number of these hypoxia-activated prodrugs have been examined in clinical trial and the merits and shortcomings of recent examples are discussed. There has been an evolution from delivering DNA-interactive cytotoxins to molecularly targeted agents. Efforts to implement these strategies clinically continue today, but success has been elusive. Several issues have been identified that compromised these clinical campaigns. A failure to consider the extravascular transport and the micropharmacokinetic properties of the prodrugs has reduced efficacy. One key element for these 'targeted' approaches is the need to co-develop biomarkers to identify appropriate patients. Hypoxia-activated prodrugs require biomarkers for hypoxia, but also for appropriate activating reductases in tumours, as well as markers of intrinsic sensitivity to the released drug. The field is still evolving and changes in radiation delivery and the impact of immune-oncology will provide fertile ground for future innovation.
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Affiliation(s)
- R K Jackson
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - L P Liew
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
| | - M P Hay
- Auckland Cancer Society Research Centre, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand.
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Abstract
In 2012, cancer affected 14.1 million people worldwide and was responsible for 8.2 million deaths. The disease predominantly affects aged populations and is one of the leading causes of death in most western countries. In tumors, the aggressive growth of the neoplastic cell population and associated overexpression of pro-angiogenic factors lead to the development of disorganized blood vessel networks that are structurally and functionally different from normal vasculature. A disorganized labyrinth of vessels that are immature, tortuous and hyperpermeable typifies tumor vasculature. Functionally, the ability of the tumor vasculature to deliver nutrients and remove waste products is severely diminished. A critical consequence of the inadequate vascular networks in solid tumors is the development of regions of hypoxia [low oxygen tensions typically defined as oxygen tensions (pO2 values) < 10 mm Hg]. Tumor cells existing in such hypoxic environments have long been known to be resistant to anticancer therapy, display an aggressive phenotype, and promote tumor progression and dissemination. This review discusses the physiological basis of hypoxia, methods of detection, and strategies to overcome the resulting therapy resistance.
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Affiliation(s)
- Veronica S Hughes
- 1 Department of Radiation Oncology, University of Florida, Cancer Genetic Research Complex , Gainesville, FL , USA
| | - Jennifer M Wiggins
- 1 Department of Radiation Oncology, University of Florida, Cancer Genetic Research Complex , Gainesville, FL , USA
| | - Dietmar W Siemann
- 1 Department of Radiation Oncology, University of Florida, Cancer Genetic Research Complex , Gainesville, FL , USA
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12
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Shen X, Laber CH, Sarkar U, Galazzi F, Johnson KM, Mahieu NG, Hillebrand R, Fuchs-Knotts T, Barnes CL, Baker GA, Gates KS. Exploiting the Inherent Photophysical Properties of the Major Tirapazamine Metabolite in the Development of Profluorescent Substrates for Enzymes That Catalyze the Bioreductive Activation of Hypoxia-Selective Anticancer Prodrugs. J Org Chem 2018; 83:3126-3131. [DOI: 10.1021/acs.joc.7b03035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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13
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Gu Y, Chang TTA, Wang J, Jaiswal JK, Edwards D, Downes NJ, Liyanage HDS, Lynch CRH, Pruijn FB, Hickey AJR, Hay MP, Wilson WR, Hicks KO. Reductive Metabolism Influences the Toxicity and Pharmacokinetics of the Hypoxia-Targeted Benzotriazine Di-Oxide Anticancer Agent SN30000 in Mice. Front Pharmacol 2017; 8:531. [PMID: 28848445 PMCID: PMC5554537 DOI: 10.3389/fphar.2017.00531] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 07/28/2017] [Indexed: 12/23/2022] Open
Abstract
3-(3-Morpholinopropyl)-7,8-dihydro-6H-indeno[5,6-e][1,2,4]triazine 1,4-dioxide (SN30- 000), an analog of the well-studied bioreductive prodrug tirapazamine (TPZ), has improved activity against hypoxic cells in tumor xenografts. However, little is known about its biotransformation in normal tissues. Here, we evaluate implications of biotransformation of SN30000 for its toxicokinetics in NIH-III mice. The metabolite profile demonstrated reduction to the 1-N-oxide (M14), oxidation of the morpholine side-chain (predominantly to the alkanoic acid M18) and chromophore, and subsequent glucuronidation. Plasma pharmacokinetics of SN30000 and its reduced metabolites was unaffected by the presence of HT29 tumor xenografts, indicating extensive reduction in normal tissues. This bioreductive metabolism, as modeled by hepatic S9 preparations, was strongly inhibited by oxygen indicating that it proceeds via the one-electron (radical) intermediate previously implicated in induction of DNA double strand breaks and cytotoxicity by SN30000. Plasma pharmacokinetics of SN30000 and M14 (but not M18) corresponded closely to the timing of reversible acute clinical signs (reduced mobility) and marked hypothermia (rectal temperature drop of ∼8°C at nadir following the maximum tolerated dose). Similar acute toxicity was elicited by dosing with TPZ or M14, although M14 did not induce the kidney and lung histopathology caused by SN30000. M14 also lacked antiproliferative potency in hypoxic cell cultures. In addition M14 showed much slower redox cycling than SN30000 in oxic cultures. Thus a non-bioreductive mechanism, mediated through M14, appears to be responsible for the acute toxicity of SN30000 while late toxicities are consistent with DNA damage resulting from its one-electron reduction. A two-compartment pharmacokinetic model, in which clearance of SN30000 is determined by temperature-dependent bioreductive metabolism to M14, was shown to describe the non-linear PK of SN30000 in mice. This study demonstrates the importance of non-tumor bioreductive metabolism in the toxicology and pharmacokinetics of benzotriazine di-oxides designed to target tumor hypoxia.
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Affiliation(s)
- Yongchuan Gu
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Tony T-A Chang
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Jingli Wang
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Jagdish K Jaiswal
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - David Edwards
- Cancer Research Centre for Drug Development, Cancer Research UK (CRUK)London, United Kingdom
| | | | - H D Sarath Liyanage
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Courtney R H Lynch
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Frederik B Pruijn
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Anthony J R Hickey
- School of Biological Sciences, The University of AucklandAuckland, New Zealand
| | - Michael P Hay
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - William R Wilson
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
| | - Kevin O Hicks
- Experimental Therapeutics Group, Auckland Cancer Society Research Centre, School of Medical Sciences, The University of AucklandAuckland, New Zealand
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14
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Moriwaki T, Okamoto S, Sasanuma H, Nagasawa H, Takeda S, Masunaga SI, Tano K. Cytotoxicity of Tirapazamine (3-Amino-1,2,4-benzotriazine-1,4-dioxide)-Induced DNA Damage in Chicken DT40 Cells. Chem Res Toxicol 2016; 30:699-704. [PMID: 27943678 DOI: 10.1021/acs.chemrestox.6b00417] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tirapazamine (TPZ) is an anticancer drug with highly selective cytotoxicity toward hypoxic cells. TPZ is converted to a radical intermediate under hypoxic conditions, and this intermediate interacts with intracellular macromolecules, including DNA. TPZ has been reported to indirectly induce DNA double-strand breaks (DSBs) through the formation of various intermediate DNA lesions under hypoxic conditions. Although the topoisomerase II-DNA complex has been identified as one of these intermediates, other lesions have not yet been defined. In order to obtain a deeper understanding of the mechanisms responsible for the selective cytotoxicity of TPZ toward hypoxic cells, its cellular sensitivity was systematically examined with genetically isogenic DNA-repair-deficient mutant DT40 cell lines. Our results showed that tdp1-/-, tdp2-/-, parp1-/-, and aptx1-/- cells displayed hypersensitivity to TPZ only under hypoxic conditions. These results strongly suggest that the accumulation of the topoisomerase I-trapped DNA complex, topoisomerase II-trapped DNA complex, and abortive ligation products with 5'-AMP are the potential causes of TPZ-induced hypoxic cell death. Furthermore, our genetic analysis revealed that under normoxic conditions (as well as hypoxic conditions), TPZ exhibited significant cytotoxicity toward cell lines deficient in homologous recombination, nonhomologous end joining, base excision repair, and translesion synthesis. Ascorbic acid, a radical scavenger, suppressed TPZ-induced cytotoxicity toward normoxic cells. These results suggest the involvement of oxidative DNA damage and DSBs produced by reactive oxygen species generated from superoxide, a byproduct of the oxidation of TPZ radical intermediates in normoxic cells. Collectively, our results demonstrate that TPZ induces oxidative DNA damage under normoxic and hypoxic conditions and selectively introduces abortive topoisomerase-DNA complexes and unligatable DNA ends under hypoxic conditions.
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Affiliation(s)
- Takahito Moriwaki
- Division of Radiation Life Science, Research Reactor Institute, Kyoto University , 2 Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - Saki Okamoto
- Division of Radiation Life Science, Research Reactor Institute, Kyoto University , 2 Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - Hiroyuki Sasanuma
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University , Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hideko Nagasawa
- Laboratory of Pharmaceutical and Medicinal Chemistry, Gifu Pharmaceutical University , 1-25-4 Daigaku-nishi, Gifu-shi, Gifu 501-1196, Japan
| | - Shunichi Takeda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University , Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Shin-Ichiro Masunaga
- Division of Radiation Life Science, Research Reactor Institute, Kyoto University , 2 Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - Keizo Tano
- Division of Radiation Life Science, Research Reactor Institute, Kyoto University , 2 Asashiro-Nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
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15
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Cheng G, Sa W, Cao C, Guo L, Hao H, Liu Z, Wang X, Yuan Z. Quinoxaline 1,4-di-N-Oxides: Biological Activities and Mechanisms of Actions. Front Pharmacol 2016; 7:64. [PMID: 27047380 PMCID: PMC4800186 DOI: 10.3389/fphar.2016.00064] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 03/07/2016] [Indexed: 11/29/2022] Open
Abstract
Quinoxaline 1,4-di-N-oxides (QdNOs) have manifold biological properties, including antimicrobial, antitumoral, antitrypanosomal and antiinflammatory/antioxidant activities. These diverse activities endow them broad applications and prospects in human and veterinary medicines. As QdNOs arouse widespread interest, the evaluation of their medicinal chemistry is still in progress. In the meantime, adverse effects have been reported in some of the QdNO derivatives. For example, genotoxicity and bacterial resistance have been found in QdNO antibacterial growth promoters, conferring urgent need for discovery of new QdNO drugs. However, the modes of actions of QdNOs are not fully understood, hindering the development and innovation of these promising compounds. Here, QdNOs are categorized based on the activities and usages, among which the antimicrobial activities are consist of antibacterial, antimycobacterial and anticandida activities, and the antiprotozoal activities include antitrypanosomal, antimalarial, antitrichomonas, and antiamoebic activities. The structure-activity relationship and the mode of actions of each type of activity of QdNOs are summarized, and the toxicity and the underlying mechanisms are also discussed, providing insight for the future research and development of these fascinating compounds.
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Affiliation(s)
- Guyue Cheng
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China; College of Veterinary Medicine, Huazhong Agricultural UniversityWuhan, China
| | - Wei Sa
- College of Veterinary Medicine, Huazhong Agricultural University Wuhan, China
| | - Chen Cao
- College of Veterinary Medicine, Huazhong Agricultural University Wuhan, China
| | - Liangliang Guo
- College of Veterinary Medicine, Huazhong Agricultural University Wuhan, China
| | - Haihong Hao
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China; College of Veterinary Medicine, Huazhong Agricultural UniversityWuhan, China
| | - Zhenli Liu
- College of Veterinary Medicine, Huazhong Agricultural UniversityWuhan, China; National Reference Laboratory of Veterinary Drug Residues and MOA Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China
| | - Xu Wang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China; College of Veterinary Medicine, Huazhong Agricultural UniversityWuhan, China
| | - Zonghui Yuan
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural UniversityWuhan, China; College of Veterinary Medicine, Huazhong Agricultural UniversityWuhan, China; National Reference Laboratory of Veterinary Drug Residues and MOA Key Laboratory for the Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural UniversityWuhan, China
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16
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Ahmadinejad N, Tari MT. Substitution effect on thermochemical properties of gas-phase tirapazamine by density functional theory. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2015. [DOI: 10.1134/s0036024415110023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Cheng G, Li B, Wang C, Zhang H, Liang G, Weng Z, Hao H, Wang X, Liu Z, Dai M, Wang Y, Yuan Z. Systematic and Molecular Basis of the Antibacterial Action of Quinoxaline 1,4-Di-N-Oxides against Escherichia coli. PLoS One 2015; 10:e0136450. [PMID: 26296207 PMCID: PMC4546592 DOI: 10.1371/journal.pone.0136450] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 08/03/2015] [Indexed: 01/28/2023] Open
Abstract
Quinoxaline 1,4-di-N-oxides (QdNOs) are widely known as potent antibacterial agents, but their antibacterial mechanisms are incompletely understood. In this study, the transcriptomic and proteomic profiles of Escherichia coli exposed to QdNOs were integratively investigated, and the results demonstrated that QdNOs mainly induced an SOS response and oxidative stress. Moreover, genes and proteins involved in the bacterial metabolism, cellular structure maintenance, resistance and virulence were also found to be changed, conferring bacterial survival strategies. Biochemical assays showed that reactive oxygen species were induced in the QdNO-treated bacteria and that free radical scavengers attenuated the antibacterial action of QdNOs and DNA damage, suggesting an oxidative-DNA-damage action of QdNOs. The QdNO radical intermediates, likely carbon-centered and aryl-type radicals, as identified by electron paramagnetic resonance, were the major radicals induced by QdNOs, and xanthine oxidase was one of the QdNO-activating enzymes. This study provides new insights into the action of QdNOs in a systematic manner and increases the current knowledge of bacterial physiology under antibiotic stresses, which may be of great value in the development of new antibiotic-potentiating strategies.
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Affiliation(s)
- Guyue Cheng
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Bei Li
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Chenxi Wang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Hongfei Zhang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Guixia Liang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Zhifei Weng
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Haihong Hao
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Xu Wang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Zhenli Liu
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Menghong Dai
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- * E-mail: (MD); (YW); (ZY)
| | - Yulian Wang
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- * E-mail: (MD); (YW); (ZY)
| | - Zonghui Yuan
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
- * E-mail: (MD); (YW); (ZY)
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18
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Johnson K, Parsons ZD, Barnes CL, Gates KS. Toward hypoxia-selective DNA-alkylating agents built by grafting nitrogen mustards onto the bioreductively activated, hypoxia-selective DNA-oxidizing agent 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine). J Org Chem 2014; 79:7520-31. [PMID: 25029663 PMCID: PMC4136725 DOI: 10.1021/jo501252p] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Indexed: 12/14/2022]
Abstract
Tirapazamine (3-amino-1,2,4-benzotriazine 1,4-dioxide) is a heterocyclic di-N-oxide that undergoes enzymatic deoxygenation selectively in the oxygen-poor (hypoxic) cells found in solid tumors to generate a mono-N-oxide metabolite. This work explored the idea that the electronic changes resulting from the metabolic deoxygenation of tirapazamine analogues might be exploited to activate a DNA-alkylating species selectively in hypoxic tissue. Toward this end, tirapazamine analogues bearing nitrogen mustard units were prepared. In the case of the tirapazamine analogue 18a bearing a nitrogen mustard unit at the 6-position, it was found that removal of the 4-oxide from the parent di-N-oxide to generate the mono-N-oxide analogue 17a did indeed cause a substantial increase in reactivity of the mustard unit, as measured by hydrolysis rates and DNA-alkylation yields. Hammett sigma values were measured to quantitatively assess the magnitude of the electronic changes induced by metabolic deoxygenation of the 3-amino-1,2,4-benzotriazine 1,4-dioxide heterocycle. The results provide evidence that the 1,2,4-benzotiazine 1,4-dioxide unit can serve as an oxygen-sensing prodrug platform for the selective unmasking of bioactive agents in hypoxic cells.
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Affiliation(s)
- Kevin
M. Johnson
- Departments of Chemistry and Biochemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United
States
| | - Zachary D. Parsons
- Departments of Chemistry and Biochemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United
States
| | - Charles L. Barnes
- Departments of Chemistry and Biochemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United
States
| | - Kent S. Gates
- Departments of Chemistry and Biochemistry, University of Missouri, 125 Chemistry Building, Columbia, Missouri 65211, United
States
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19
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Wang J, Guise CP, Dachs GU, Phung Y, Hsu AHL, Lambie NK, Patterson AV, Wilson WR. Identification of one-electron reductases that activate both the hypoxia prodrug SN30000 and diagnostic probe EF5. Biochem Pharmacol 2014; 91:436-46. [PMID: 25130546 DOI: 10.1016/j.bcp.2014.08.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/08/2014] [Accepted: 08/08/2014] [Indexed: 02/08/2023]
Abstract
SN30000 is a second-generation benzotriazine-N-oxide hypoxia-activated prodrug scheduled for clinical trial. Previously we showed that covalent binding of the hypoxia probe EF5 predicts metabolic activation of SN30000 in a panel of cancer cell lines under anoxia, suggesting that they are activated by the same reductases. However the identity of these reductases is unknown. Here, we test whether forced expression of nine oxidoreductases with known or suspected roles in bioreductive prodrug metabolism (AKR1C3, CYB5R3, FDXR, MTRR, NDOR1, NOS2A, NQO1, NQO2 and POR) enhances oxic or anoxic reduction of SN30000 and EF5 by HCT116 cells. Covalent binding of (14)C-EF5 and reduction of SN30000 to its 1-oxide and nor-oxide metabolites was highly selective for anoxia in all lines, with significantly elevated anoxic metabolism of both compounds in lines over-expressing POR, MTRR, NOS2A or NDOR1. There was a strong correlation between EF5 binding and SN30000 metabolism under anoxia across the cell lines (R(2)=0.84, p=0.0001). Antiproliferative potency of SN30000 under anoxia was increased most strongly by overexpression of MTRR and POR. Transcript abundance in human tumours, evaluated using public domain mRNA expression data, was highest for MTRR, followed by POR, NOS2A and NDOR1, with little variation between tumour types. Immunostaining of tissue microarrays demonstrated variable MTRR protein expression across 517 human cancers with most displaying low expression. In conclusion, we have identified four diflavin reductases (POR, MTRR, NOS2A and NDOR1) capable of reducing both SN30000 and EF5, further supporting use of 2-nitroimidazole probes to predict the ability of hypoxic cells to activate SN30000.
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Affiliation(s)
- Jingli Wang
- Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland, New Zealand
| | - Chris P Guise
- Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand
| | - Gabi U Dachs
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand; Department of Pathology, University of Otago Christchurch, PO Box 4345, Christchurch 8140, New Zealand
| | - Yen Phung
- Department of Pathology, University of Otago Christchurch, PO Box 4345, Christchurch 8140, New Zealand
| | - Annie Huai-Ling Hsu
- Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland, New Zealand
| | - Neil K Lambie
- Department of Anatomical Pathology, Prince of Wales Hospital, Barker Street, Randwick, NSW 2031, Australia
| | - Adam V Patterson
- Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand
| | - William R Wilson
- Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand.
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20
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Anderson RF, Yadav P, Patel D, Reynisson J, Tipparaju SR, Guise CP, Patterson AV, Denny WA, Maroz A, Shinde SS, Hay MP. Characterisation of radicals formed by the triazine 1,4-dioxide hypoxia-activated prodrug, SN30000. Org Biomol Chem 2014; 12:3386-92. [PMID: 24737463 DOI: 10.1039/c4ob00236a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The radical species underlying the activity of the bioreductive anticancer prodrug, SN30000, have been identified by electron paramagnetic resonance and pulse radiolysis techniques. Spin-trapping experiments indicate both an aryl-type radical and an oxidising radical, trapped as a carbon-centred radical, are formed from the protonated radical anion of SN30000. The carbon-centred radical, produced upon the one-electron oxidation of the 2-electron reduced metabolite of SN30000, oxidises 2-deoxyribose, a model for the site of damage on DNA which leads to double strand breaks. Calculations using density functional theory support the assignments made.
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Affiliation(s)
- Robert F Anderson
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
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21
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Yadav P, Marshall AJ, Reynisson J, Denny WA, Hay MP, Anderson RF. Fragmentation of the quinoxaline N-oxide bond to the ˙OH radical upon one-electron bioreduction. Chem Commun (Camb) 2014; 50:13729-31. [DOI: 10.1039/c4cc05657d] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
One-electron reduction of 3-trifluoromethyl-quinoxaline 1,4-dioxide breaks the N-oxide bond to release the ˙OH radical.
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Affiliation(s)
- Pooja Yadav
- Auckland Cancer Society Research Centre
- University of Auckland
- Auckland 1142, New Zealand
| | - Andrew J. Marshall
- Auckland Cancer Society Research Centre
- University of Auckland
- Auckland 1142, New Zealand
| | - Jóhannes Reynisson
- School of Chemical Sciences
- University of Auckland
- Auckland 1142, New Zealand
| | - William A. Denny
- Auckland Cancer Society Research Centre
- University of Auckland
- Auckland 1142, New Zealand
| | - Michael P. Hay
- Auckland Cancer Society Research Centre
- University of Auckland
- Auckland 1142, New Zealand
| | - Robert F. Anderson
- Auckland Cancer Society Research Centre
- University of Auckland
- Auckland 1142, New Zealand
- School of Chemical Sciences
- University of Auckland
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22
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Hypoxia-Directed Drug Strategies to Target the Tumor Microenvironment. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 772:111-45. [DOI: 10.1007/978-1-4614-5915-6_6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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23
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Shen X, Rajapakse A, Gallazzi F, Junnotula V, Fuchs-Knotts T, Glaser R, Gates KS. Isotopic labeling experiments that elucidate the mechanism of DNA strand cleavage by the hypoxia-selective antitumor agent 1,2,4-benzotriazine 1,4-di-N-oxide. Chem Res Toxicol 2013; 27:111-8. [PMID: 24328261 DOI: 10.1021/tx400356y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The 1,2,4-benzotriazine 1,4-dioxides are an important class of potential anticancer drugs that selectively kill the low-oxygen (hypoxic) cells found in solid tumors. These compounds undergo intracellular one-electron enzymatic reduction to yield an oxygen-sensitive drug radical intermediate that partitions forward, under hypoxic conditions, to generate a highly reactive secondary radical that causes cell killing DNA damage. Here, we characterized bioreductively activated, hypoxia-selective DNA-strand cleavage by 1,2,4-benzotriazine 1,4-dioxide. We found that one-electron enzymatic activation of 1,2,4-benzotriazine 1,4-dioxide under hypoxic conditions in the presence of the deuterium atom donor methanol-d4 produced nondeuterated mono-N-oxide metabolites. This and the results of other isotopic labeling studies provided evidence against the generation of atom-abstracting drug radical intermediates and are consistent with a DNA-damage mechanism involving the release of hydroxyl radical from enzymatically activated 1,2,4-benzotriazine 1,4-dioxides.
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Affiliation(s)
- Xiulong Shen
- Department of Chemistry, University of Missouri , 125 Chemistry Building, Columbia, Missouri 65211, United States
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24
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Rajapakse A, Linder C, Morrison RD, Sarkar U, Leigh ND, Barnes CL, Daniels JS, Gates KS. Enzymatic conversion of 6-nitroquinoline to the fluorophore 6-aminoquinoline selectively under hypoxic conditions. Chem Res Toxicol 2013; 26:555-63. [PMID: 23488987 DOI: 10.1021/tx300483z] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is substantial interest in small molecules that can be used to detect or kill the hypoxic (low oxygen) cells found in solid tumors. Nitroaryl moieties are useful components in the design of hypoxia-selective imaging agents and prodrugs because one-electron reductases can convert the nitroaryl group to nitroso, hydroxylamino, and amino metabolites selectively under low oxygen conditions. Here, we describe the in vitro, cell free metabolism of a pro-fluorescent substrate, 6-nitroquinoline (1) under both aerobic and hypoxic conditions. Both LC-MS and fluorescence spectroscopic analyses provided evidence that the one-electron reducing enzyme system, xanthine/xanthine oxidase, converted the nonfluorescent parent compound 1 to the known fluorophore 6-aminoquinoline (2) selectively under hypoxic conditions. The presumed intermediate in this reduction process, 6-hydroxylaminoquinoline (6), is fluorescent and can be efficiently converted by xanthine/xanthine oxidase to 2 only under hypoxic conditions. This finding provides evidence for multiple oxygen-sensitive steps in the enzymatic conversion of nitroaryl compounds to the corresponding amino derivatives. In a side reaction that is separate from the bioreductive metabolism of 1, xanthine oxidase converted 1 to 6-nitroquinolin-2(1H)-one (5). These studies may enable the use of 1 as a fluorescent substrate for the detection and profiling of one-electron reductases in cell culture or biopsy samples. In addition, the compound may find use as a fluorogenic probe for the detection of hypoxia in tumor models. The occurrence of side products such as 5 in the enzymatic bioreduction of 1 underscores the importance of metabolite identification in the characterization of hypoxia-selective probes and drugs that employ nitroaryl units as oxygen sensors.
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Affiliation(s)
- Anuruddha Rajapakse
- Department of Chemistry, University of Missouri , 125 Chemistry Building, Columbia, Missouri 65211, United States
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25
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Transferring oxygen isotopes to 1,2,4-benzotriazine 1-oxides forming the corresponding 1,4-dioxides by using the HOF·CH3CN complex. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.08.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Yin J, Glaser R, Gates KS. On the reaction mechanism of tirapazamine reduction chemistry: unimolecular N-OH homolysis, stepwise dehydration, or triazene ring-opening. Chem Res Toxicol 2012; 25:634-45. [PMID: 22390168 DOI: 10.1021/tx200546u] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The initial steps of the activation of tirapazamine (TPZ, 1, 3-amino-1,2,4-benzotriazine 1,4-N,N-dioxide) under hypoxic conditions consist of the one-electron reduction of 1 to radical anion 2 and the protonation of 2 at O(N4) or O(N1) to form neutral radicals 3 and 4, respectively. There are some questions, however, as to whether radicals 3 and/or 4 will then undergo N-OH homolyses 3 → 5 + ·OH and 4 → 6 + ·OH or, alternatively, whether 3 and/or 4 may react by dehydration and form aminyl radicals via 3 → 11 + H(2)O and 4 → 12 + H(2)O or phenyl radicals via 3 → 17 + H(2)O. These outcomes might depend on the chemistry after the homolysis of 3 and/or 4, that is, dehydration may be the result of a two-step sequence that involves N-OH homolysis and formation of ·OH aggregates of 5 and 6 followed by H-abstraction within the ·OH aggregates to form hydrates of aminyls 11 and 12 or of phenyl 17. We studied these processes with configuration interaction theory, perturbation theory, and density functional theory. All stationary structures of OH aggregates of 5 and 6, of H(2)O aggregates of 11, 12, and 17, and of the transition state structures for H-abstraction were located and characterized by vibrational analysis and with methods of electron and spin-density analysis. The doublet radical 17 is a normal spin-polarized radical, whereas the doublet radicals 11 and 12 feature quartet instabilities. The computed reaction energies and activation barriers allow for dehydration in principle, but the productivity of all of these channels should be low for kinetic and dynamic reasons. With a view to plausible scenarios for the generation of latent aryl radical species without dehydration, we scanned the potential energy surfaces of 2-4 as a function of the (O)N1-Y (Y = C5a, N2) and (O)N4-Z (Z = C4a, C3) bond lengths. The elongation of any one of these bonds by 0.5 Å requires less than 25 kcal/mol, and this finding strongly suggests the possibility of bimolecular reactions of the spin-trap molecules with 2-4 concomitant with triazene ring-opening.
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Affiliation(s)
- Jian Yin
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
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27
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Yin J, Glaser R, Gates KS. Electron and spin-density analysis of tirapazamine reduction chemistry. Chem Res Toxicol 2012; 25:620-33. [PMID: 22390194 DOI: 10.1021/tx2005458] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Tirapazamine (TPZ, 1, 3-amino-1,2,4-benzotriazine 1,4-N,N-dioxide), the radical anion 2 formed by one-electron reduction of 1, and neutral radicals 3 and 4 formed by protonation of 2 at O(N4) or O(N1), respectively, and their N-OH homolyses 3 → 5 + ·OH and 4 → 6 + ·OH have been studied with configuration interaction theory, perturbation theory, and density functional theory. A comprehensive comparative analysis is presented of structures and electronic structures and with focus on the development of an understanding of the spin-density distributions of the radical species. The skeletons of radicals 3 and 4 are distinctly nonplanar, several stereoisomeric structures are discussed, and there exists an intrinsic preference for 3 over 4. The N-oxides 1, 5, and 6 have closed-shell singlet ground states and low-lying, singlet biradical (SP-1, SP-6) or biradicaloid (SP-5) excited states. The doublet radicals 2, 3, and 4 are heavily spin-polarized. Most of the spin density of the doublet radicals 2, 3, and 4 is located in one (N,O)-region, and in particular, 3 and 4 are not C3-centered radicals. Significant amounts of spin density occur in both rings in the singlet biradical(oid) excited states of 1, 5, and 6. The dipole moment of the N2-C3(X) bond is large, and the nature of X provides a powerful handle to modulate the N2-C3 bond polarity with opposite effects on the two NO regions. Our studies show very low proton affinities of radical anion 2 and suggest that the pK(a) of radical [2+H] might be lower than 6. Implications are discussed regarding the formation of hydroxyl from 3 and/or 4, regarding the ability of 5 and 6 to react with carbon-centered radicals in a manner that ultimately leads to oxygen transfer, and regarding the interpretation of the EPR spectra of reduced TPZ species and of their spin-trap adducts.
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Affiliation(s)
- Jian Yin
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA
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Chowdhury G, Sarkar U, Pullen S, Wilson WR, Rajapakse A, Fuchs-Knotts T, Gates KS. DNA strand cleavage by the phenazine di-N-oxide natural product myxin under both aerobic and anaerobic conditions. Chem Res Toxicol 2011; 25:197-206. [PMID: 22084973 DOI: 10.1021/tx2004213] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Heterocyclic N-oxides are an interesting class of antitumor agents that selectively kill the hypoxic cells found in solid tumors. The hypoxia-selective activity of the lead compound in this class, tirapazamine, stems from its ability to undergo intracellular one-electron reduction to an oxygen-sensitive drug radical intermediate. In the presence of molecular oxygen, the radical intermediate is back-oxidized to the parent molecule. Under hypoxic conditions, the extended lifetime of the drug radical intermediate enables its conversion to a highly cytotoxic DNA-damaging intermediate via a "deoxygenative" mechanism involving the loss of oxygen from one of its N-oxide groups. The natural product myxin is a phenazine di-N-oxide that displays potent antibiotic activity against a variety of organisms under aerobic conditions. In light of the current view of heterocyclic N-oxides as agents that selectively operate under hypoxic conditions, it is striking that myxin was identified from Sorangium extracts based upon its antibiotic properties under aerobic conditions. Therefore, we set out to examine the molecular mechanisms underlying the biological activity of myxin. We find that myxin causes bioreductively activated, radical-mediated DNA strand cleavage under both aerobic and anaerobic conditions. Our evidence indicates that strand cleavage occurs via a deoxygenative metabolism. We show that myxin displays potent cytotoxicity against the human colorectal cancer cell line HCT-116 under both aerobic and anaerobic conditions that is comparable to the cell-killing properties of tirapazamine under anaerobic conditions. This work sheds light on the processes by which the naturally occurring aromatic N-oxide myxin gains its potent antibiotic properties under aerobic conditions. Furthermore, these studies highlight the general potential for aromatic N-oxides to undergo highly cytotoxic deoxygenative metabolism following enzymatic one-electron reduction under aerobic conditions.
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Affiliation(s)
- Goutam Chowdhury
- Department of Chemistry, University of Missouri-Columbia, 125 Chemistry Building, Columbia, Missouri 65211, United States
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ZHA DONG, LI LAICAI, ZHENG YAN, WANG XIN, TIAN ANMIN, WONG NINGBEW. THEORETICAL STUDY OF THE HYDROLYSIS MECHANISM OF METABOLIC PRODUCT FROM TIRAPAZAMINE'S UNDERGOING ENZYMATIC CATALYSIS. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633606002143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Two different hydrolysis mechanisms of metabolic product from tirapazamine's enzymatic catalysis have been studied by density functional theory (DFT) at the B3LYP/6-31G(d) and B3LYP/6-311+G(d) levels. The results indicate that the activation barrier of rate-controling step of Brown's model is smaller than that of Denny's model.
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Affiliation(s)
- DONG ZHA
- Department of Chemistry, Sichuan Normal University, Chengdu 610066, People's Republic of China
| | - LAI-CAI LI
- Department of Chemistry, Sichuan Normal University, Chengdu 610066, People's Republic of China
| | - YAN ZHENG
- Department of Chemistry, Sichuan Normal University, Chengdu 610066, People's Republic of China
| | - XIN WANG
- Department of Chemistry, Sichuan University, Chengdu 610064, People's Republic of China
| | - AN-MIN TIAN
- Department of Chemistry, Sichuan University, Chengdu 610064, People's Republic of China
| | - NING-BEW WONG
- Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong, China
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Hicks KO, Siim BG, Jaiswal JK, Pruijn FB, Fraser AM, Patel R, Hogg A, Liyanage HDS, Dorie MJ, Brown JM, Denny WA, Hay MP, Wilson WR. Pharmacokinetic/pharmacodynamic modeling identifies SN30000 and SN29751 as tirapazamine analogues with improved tissue penetration and hypoxic cell killing in tumors. Clin Cancer Res 2010; 16:4946-57. [PMID: 20732963 DOI: 10.1158/1078-0432.ccr-10-1439] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE Tirapazamine (TPZ) has attractive features for targeting hypoxic cells in tumors but has limited clinical activity, in part because of poor extravascular penetration. Here, we identify improved TPZ analogues by using a spatially resolved pharmacokinetic/pharmacodynamic (SR-PKPD) model that considers tissue penetration explicitly during lead optimization. EXPERIMENTAL DESIGN The SR-PKPD model was used to guide the progression of 281 TPZ analogues through a hierarchical screen. For compounds exceeding hypoxic selectivity thresholds in single-cell cultures, SR-PKPD model parameters (kinetics of bioreductive metabolism, clonogenic cell killing potency, diffusion coefficients in multicellular layers, and plasma pharmacokinetics at well tolerated doses in mice) were measured to prioritize testing in xenograft models in combination with radiation. RESULTS SR-PKPD-guided lead optimization identified SN29751 and SN30000 as the most promising hypoxic cytotoxins from two different structural subseries. Both were reduced to the corresponding 1-oxide selectively under hypoxia by HT29 cells, with an oxygen dependence quantitatively similar to that of TPZ. SN30000, in particular, showed higher hypoxic potency and selectivity than TPZ in tumor cell cultures and faster diffusion through HT29 and SiHa multicellular layers. Both compounds also provided superior plasma PK in mice and rats at equivalent toxicity. In agreement with SR-PKPD predictions, both were more active than TPZ with single dose or fractionated radiation against multiple human tumor xenografts. CONCLUSIONS SN30000 and SN29751 are improved TPZ analogues with potential for targeting tumor hypoxia in humans. Novel SR-PKPD modeling approaches can be used for lead optimization during anticancer drug development.
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Affiliation(s)
- Kevin O Hicks
- Auckland Cancer Society Research Centre, The University of Auckland, Auckland, New Zealand
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Shinde SS, Maroz A, Hay MP, Patterson AV, Denny WA, Anderson RF. Characterization of radicals formed following enzymatic reduction of 3-substituted analogues of the hypoxia-selective cytotoxin 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine). J Am Chem Soc 2010; 132:2591-9. [PMID: 20141134 DOI: 10.1021/ja908689f] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The mechanism by which the 1,2,4-benzotriazine 1,4-dioxide (BTO) class of bioreductive hypoxia-selective prodrugs (HSPs) form reactive radicals that kill cancer cells has been investigated by steady-state radiolysis, pulse radiolysis (PR), electron paramagnetic resonance (EPR), and density functional theory (DFT) calculations. Tirapazamine (TPZ, 3-amino BTO, 1) and a series of 3-substituted analogues, -H (2), -methyl (3), -ethyl (4), -methoxy (5), -ethoxymethoxy (6), and -phenyl (7), were reduced in aqueous solution under anaerobic steady-state radiolysis conditions, and their radicals were found to remove the substrates by short chain reactions of different lengths in the presence of formate ions. Multiple carbon-centered radical intermediates, produced upon anaerobic incubation of the compounds with cytochrome P(450) reductase enriched microsomes, were trapped by N-tert-butyl-alpha-phenylnitrone and observed using EPR. The highly oxidizing oxymethyl radical, from compound 5, was identified, and experimental spectra obtained for compounds 1, 2, 3, and 7 were well simulated after the inclusion of aryl radicals. The identification of a range of oxidizing radicals in the metabolism of the BTO compounds gives a new insight into the mechanism by which these HSPs can cause a wide variety of damage to biological targets such as DNA.
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Affiliation(s)
- Sujata S Shinde
- Department of Chemistry and Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Junnotula V, Rajapakse A, Arbillaga L, de Cerain AL, Solano B, Villar R, Monge A, Gates KS. DNA strand cleaving properties and hypoxia-selective cytotoxicity of 7-chloro-2-thienylcarbonyl-3-trifluoromethylquinoxaline 1,4-dioxide. Bioorg Med Chem 2010; 18:3125-32. [PMID: 20371184 PMCID: PMC3268132 DOI: 10.1016/j.bmc.2010.03.042] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 03/15/2010] [Accepted: 03/16/2010] [Indexed: 11/28/2022]
Abstract
The heterocyclic N-oxide, 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, 1), shows promising antitumor activity in preclinical studies, but there is a continuing need to explore new compounds in this general structural category. In the work described here, we examined the properties of 7-chloro-2-thienylcarbonyl-3-trifluoromethylquinoxaline 1,4-dioxide (9h). We find that 9h causes redox-activated, hypoxia-selective DNA cleavage that mirrors the lead compound, tirapazamine, in both mechanism and potency. Furthermore, we find that 9h displays hypoxia-selective cytotoxicity against human cancer cell lines.
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Shinde SS, Hay MP, Patterson AV, Denny WA, Anderson RF. Spin trapping of radicals other than the *OH radical upon reduction of the anticancer agent tirapazamine by cytochrome P450 reductase. J Am Chem Soc 2009; 131:14220-1. [PMID: 19772319 DOI: 10.1021/ja906860a] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The radical species produced following one-electron reduction of tirapazamine (3-amino-1,2,4-benzotriazine 1,4-dioxide, TPZ) by cytochrome P(450) reductase-enriched microsomes have been investigated using electron paramagnetic resonance (EPR) spectroscopy. Spin trapping with 5,5'-dimethylpyrroline 1-N-oxide (DMPO) gave a composite spectrum of a carbon-centered radical and the well-known DMPO-OH adduct. Using (17)O-labeled water resulted in a change in the EPR spectrum to that of DMPO-(17)OH, indicating that this radical species is formed with solvent involvement and not from release of a (*)OH radical from one-electron-reduced TPZ. Furthermore, using the closely related spin trap 5-diethoxyphosphoryl-5-methylpyrroline N-oxide (DEPMPO), which is less prone to oxidation than DMPO, gave only a carbon-centered radical spectrum without any involvement of a (*)OH radical. Reduction of a more soluble analogue of TPZ, in redox equilibrium with its 1-oxide derivative, led to spin trapping of both a carbon-centered radical and a nitrogen-centered radical by N-tert-butyl-alpha-phenylnitrone (PBN). The multicentered nature of this nitrogen-centered radical spectrum provides support for the formation of a benzotriazinyl radical following one-electron reduction of this class of bioreductive drug.
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Affiliation(s)
- Sujata S Shinde
- Department of Chemistry and Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Abstract
PURPOSE This article seeks to illustrate some contributions of radiation chemistry to radiobiology and related science, and to draw attention to examples where radiation chemistry is central to our knowledge of specific aspects. Radiation chemistry is a mature branch of radiation science which is continually evolving and finding wider applications. This is particularly apparent in the study of the roles of free radicals in biology generally, and radiation biology specifically. The chemical viewpoint helps unite the spatial and temporal insight coming from radiation physics with the diversity of biological responses. While historically, the main application of radiation chemistry of relevance to radiation biology has been investigations of the free-radical processes leading to radiation-induced DNA damage and its chemical characterization, two features of radiation chemistry point to its wider importance. First, its emphasis on quantification and characterization at the molecular level helps provide links between DNA damage, biochemical repair processes, and mutagenicity and radiosensitivity. Second, its central pillar of chemical kinetics aids understanding of the roles of 'reactive oxygen species' in cell signalling and diverse biological effects more generally, and application of radiation chemistry in the development of drugs to enhance radiotherapy and as hypoxia-specific cytotoxins or diagnostic agents. The illustrations of the broader applications of radiation chemistry in this article focus on their relevance to radiation biology and demonstrate the importance of synergy in the radiation sciences. CONCLUSIONS The past contributions of radiation chemistry to radiation biology are evident, but there remains considerable potential to help advance future biological understanding using the knowledge and techniques of radiation chemistry.
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Affiliation(s)
- Peter O'Neill
- University of Oxford, Gray Institute for Radiation Oncology and Biology, Oxford, UK.
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WARDMAN P. The importance of radiation chemistry to radiation and free radical biology (The 2008 Silvanus Thompson Memorial Lecture). Br J Radiol 2009; 82:89-104. [DOI: 10.1259/bjr/60186130] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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Junnotula V, Sarkar U, Sinha S, Gates KS. Initiation of DNA strand cleavage by 1,2,4-benzotriazine 1,4-dioxide antitumor agents: mechanistic insight from studies of 3-methyl-1,2,4-benzotriazine 1,4-dioxide. J Am Chem Soc 2009; 131:1015-24. [PMID: 19117394 PMCID: PMC2819123 DOI: 10.1021/ja8049645] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The antitumor agent 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, TPZ, 1) gains medicinal activity through its ability to selectively damage DNA in the hypoxic cells found inside solid tumors. This occurs via one-electron enzymatic reduction of TPZ to yield an oxygen-sensitive drug radical (2) that leads to oxidatively generated DNA damage under hypoxic conditions. Two possible mechanisms have been considered to account for oxidatively generated DNA damage by TPZ. First, homolysis of the N-OH bond in 2 may yield the well-known DNA-damaging agent, hydroxyl radical. Alternatively, it has been suggested that elimination of water from 2 generates a benzotriazinyl radical (4) as the ultimate DNA-damaging species. In the studies described here, the TPZ analogue 3-methyl-1,2,4-benzotriazine 1,4-dioxide (5) was employed as a tool to probe the mechanism of DNA damage within this new class of antitumor drugs. Initially, it was demonstrated that 5 causes redox-activated, hypoxia-selective oxidation of DNA and small organic substrates in a manner that is completely analogous to TPZ. This suggests that 5 and TPZ damage DNA by the same chemical mechanism. Importantly, the methyl substituent in 5 provides a means for assessing whether the putative benzotriazinyl intermediate 7 is generated following one-electron reduction. Two complementary isotopic labeling experiments provide evidence against the formation of the benzotriazinyl radical intermediate. Rather, a mechanism involving the release of hydroxyl radical from the activated drug radical intermediates can explain the DNA-cleaving properties of this class of antitumor drug candidates.
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Affiliation(s)
- Venkatraman Junnotula
- University of Missouri–Columbia, Departments of Chemistry and Biochemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Ujjal Sarkar
- University of Missouri–Columbia, Departments of Chemistry and Biochemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Sarmistha Sinha
- University of Missouri–Columbia, Departments of Chemistry and Biochemistry, 125 Chemistry Building, Columbia, MO 65211
| | - Kent S. Gates
- University of Missouri–Columbia, Departments of Chemistry and Biochemistry, 125 Chemistry Building, Columbia, MO 65211
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Lavaggi ML, Cabrera M, González M, Cerecetto H. Differential Enzymatic Reductions Governing the Differential Hypoxia-Selective Cytotoxicities of Phenazine 5,10-Dioxides. Chem Res Toxicol 2008; 21:1900-6. [DOI: 10.1021/tx800199v] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- María Laura Lavaggi
- Departamento de Química Orgánica, Facultad de Química-Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - Mauricio Cabrera
- Departamento de Química Orgánica, Facultad de Química-Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - Mercedes González
- Departamento de Química Orgánica, Facultad de Química-Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - Hugo Cerecetto
- Departamento de Química Orgánica, Facultad de Química-Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
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Solano B, Junnotula V, Marín A, Villar R, Burguete A, Vicente E, Pérez-Silanes S, Aldana I, Monge A, Dutta S, Sarkar U, Gates KS. Synthesis and biological evaluation of new 2-arylcarbonyl-3-trifluoromethylquinoxaline 1,4-di-N-oxide derivatives and their reduced analogues. J Med Chem 2007; 50:5485-92. [PMID: 17910426 DOI: 10.1021/jm0703993] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As a continuation of our research in the quinoxaline 1,4-di-N-oxide new series of 2-arylcarbonyl-3-trifluoromethylquinoxaline, 1,4-di-N-oxide derivatives have been synthesized and evaluated in a full panel of 60 human tumor cell lines. Selective reductions were carried out on two compounds which allowed us to determine the compound structures by comparison of the 1H NMR spectra. In general, all the di-N-oxidized compounds showed good cytotoxic parameters. The best activity was observed in derivatives with electron-withdrawing groups in position 6 or 7 on the quinoxaline ring and in the unsubstituted analogues, whereas loss of one or two oxygens reduced the cytotoxicity. The best five compounds were selected for evaluation for the in vivo hollow fiber assays. In vitro studies reveal that compound 5h efficiently generates reactive oxygen species via redox cycling in the presence of the NADPH/cytochrome P450 enzyme system, providing a plausible molecular mechanism for the observed aerobic cytotoxicity of these quinoxaline N-oxides.
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Affiliation(s)
- Beatriz Solano
- Unidad en Investigación y Desarrollo de Medicamentos, Centro de Investigación en Farmacobiología Aplicada (CIFA), University of Navarra, c/Irunlarrea s/n, 31080 Pamplona, Spain
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Chowdhury G, Junnotula V, Daniels JS, Greenberg MM, Gates KS. DNA strand damage product analysis provides evidence that the tumor cell-specific cytotoxin tirapazamine produces hydroxyl radical and acts as a surrogate for O(2). J Am Chem Soc 2007; 129:12870-7. [PMID: 17900117 PMCID: PMC2821206 DOI: 10.1021/ja074432m] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The compound 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, TPZ) is a clinically promising anticancer agent that selectively kills the oxygen-poor (hypoxic) cells found in solid tumors. It has long been known that, under hypoxic conditions, TPZ causes DNA strand damage that is initiated by the abstraction of hydrogen atoms from the deoxyribose phosphate backbone of duplex DNA, but exact chemical mechanisms underlying this process remain unclear. Here we describe detailed characterization of sugar-derived products arising from TPZ-mediated strand damage. We find that the action of TPZ on duplex DNA under hypoxic conditions generates 5-methylene-2-furanone (6), oligonucleotide 3'-phosphoglycolates (7), malondialdehyde equivalents (8 or 9), and furfural (10). These results provide evidence that TPZ-mediated strand damage arises via hydrogen atom abstraction from both the most hindered (C1') and least hindered (C4' and C5') positions of the deoxyribose sugars in the double helix. The products observed are identical to those produced by hydroxyl radical. Additional experiments were conducted to better understand the chemical pathways by which TPZ generates the observed DNA-damage products. Consistent with previous work showing that TPZ can substitute for molecular oxygen in DNA damage reactions, it is found that, under anaerobic conditions, reaction of TPZ with a discrete, photogenerated C1'-radical in a DNA 2'-oligodeoxynucleotide cleanly generates the 2-deoxyribonolactone lesion (5) that serves as the precursor to 5-methylene-2-furanone (6). Overall, the results provide insight regarding the chemical structure of the DNA lesions that confront cellular repair, transcription, and replication machinery following exposure to TPZ and offer new information relevant to the chemical mechanisms underlying TPZ-mediated strand cleavage.
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Affiliation(s)
- Goutam Chowdhury
- University of Missouri–Columbia Departments of Chemistry and Biochemistry 125 Chemistry Building Columbia, MO 65211
| | - Venkatraman Junnotula
- University of Missouri–Columbia Departments of Chemistry and Biochemistry 125 Chemistry Building Columbia, MO 65211
| | - J. Scott Daniels
- University of Missouri–Columbia Departments of Chemistry and Biochemistry 125 Chemistry Building Columbia, MO 65211
| | - Marc M. Greenberg
- Johns Hopkins University Department of Chemistry 3400 N. Charles St. Baltimore, MD 21218
| | - Kent S. Gates
- University of Missouri–Columbia Departments of Chemistry and Biochemistry 125 Chemistry Building Columbia, MO 65211
- To whom correspondence should be addressed: ; phone: (573) 882-6763; FAX: (573) 882-2754
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Wilson WR, Hicks KO, Pullen SM, Ferry DM, Helsby NA, Patterson AV. Bystander effects of bioreductive drugs: potential for exploiting pathological tumor hypoxia with dinitrobenzamide mustards. Radiat Res 2007; 167:625-36. [PMID: 17523848 DOI: 10.1667/rr0807.1] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Accepted: 12/08/2006] [Indexed: 11/03/2022]
Abstract
Tumor hypoxia is an important therapeutic target, and it can potentially be exploited by hypoxia-activated prodrugs. However, physiological hypoxia in normal tissues is a limitation. One solution would be to confine activation to severely (pathologically) hypoxic tissue, using hypoxia-activated prodrugs that provide a bystander effect through diffusion of the activated cytotoxin to adjacent regions at intermediate oxygen concentrations (associated with partial radioresistance). To evaluate this requirement, we identified five hypoxia-activated prodrugs with at least 10-fold higher potency against a cell line (A549-P540(puro)) overexpressing human cytochrome P450 reductase (P450R) relative to A549-Lo21 cells with 200-fold lower P450R activity. Bystander killing by these hypoxia-activated prodrugs was tested in anoxic multicellular layer co-cultures of these two cell lines. Cytotoxic potency against A549-Lo21 cells was unaffected by the presence of A549-P450(puro) cells for tirapazamine and RSU-1069 but increased more than 10-fold for the aziridinyldintrobenzamide CB 1954, more than 14-fold for the corresponding nitrogen mustard SN 23862, and 15-fold for its water-soluble analog SN 23816. The cytotoxic extracellular metabolites resulting from hypoxic nitroreduction of CB 1954 and SN 23862 by A549-P450(puro) cells were identified by LC/MS and bioassay methods. For SN 23862, these included the 2-amine metabolite, previously, identified as the bystander metabolite from aerobic activation by the E. coli nfsB nitroreductase, but also novel di-reduced metabolites. Cytotoxicity of SN 23862 to A549-P450(puro) cells was inhibited by lower concentrations of oxygen than for tirapazamine. The combination of selective activation under severe hypoxia with an efficient bystander effect identifies the dinitrobenzamide mustards for further development as hypoxia-activated prodrugs.
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Affiliation(s)
- William R Wilson
- Auckland Cancer Society Research Centre, The University of Auckland, Auckland, New Zealand.
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Wardman P. Chemical radiosensitizers for use in radiotherapy. Clin Oncol (R Coll Radiol) 2007; 19:397-417. [PMID: 17478086 DOI: 10.1016/j.clon.2007.03.010] [Citation(s) in RCA: 317] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Accepted: 03/13/2007] [Indexed: 12/21/2022]
Abstract
Radiosensitizers are intended to enhance tumour cell killing while having much less effect on normal tissues. Some drugs target different physiological characteristics of the tumour, particularly hypoxia associated with radioresistance. Oxygen is the definitive hypoxic cell radiosensitizer, the large differential radiosensitivity of oxic vs hypoxic cells being an attractive factor. The combination of nicotinamide to reduce acute hypoxia with normobaric carbogen breathing is showing clinical promise. 'Electron-affinic' chemicals that react with DNA free radicals have the potential for universal activity to combat hypoxia-associated radioresistance; a nitroimidazole, nimorazole, is clinically effective at tolerable doses. Hypoxia-specific cytotoxins, such as tirapazamine, are valuable adjuncts to radiotherapy. Nitric oxide is a potent hypoxic cell radiosensitizer; variations in endogenous levels might have prognostic significance, and routes to deliver nitric oxide specifically to tumours are being developed. In principle, many drugs can be delivered selectively to hypoxic tumours using either reductase enzymes or radiation-produced free radicals to activate drug release from electron-affinic prodrugs. A redox-active agent based on a gadolinium chelate is being evaluated clinically. Pyrimidines substituted with bromine or iodine are incorporated into DNA and enhance free radical damage; fluoropyrimidines act by different mechanisms. A wide variety of drugs that influence the nature or repair of DNA damage are being evaluated in conjunction with radiation; it is often difficult to define the mechanisms underlying chemoradiation regimens. Drugs being evaluated include topoisomerase inhibitors (e.g. camptothecin, topotecan), and the hypoxia-activated anthraquinone AQ4N; alkylating agents include temozolomide. Drugs involved in DNA repair pathways being investigated include the potent poly(ADP ribose)polymerase inhibitor, AG14,361. Proteins involved in cell signalling, such as the Ras family, are attractive targets linked to radioresistance, as are epidermal growth factor receptors and linked kinases (drugs including vandetanib [ZD6,474], cetuximab and gefitinib), and cyclooxygenase-2 (celecoxib). The suppression of radioprotective thiols seems to offer more potential with alkylating agents than with radiotherapy, although it remains a strategy worthy of exploration.
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Affiliation(s)
- P Wardman
- University of Oxford, Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood HA6 2JR, UK.
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Zayas B, Beyley J, Terron M, Cordero M, Hernandez W, Alegría AE, Cox O. Comparison of the nucleic acid covalent binding capacity of two nitro-substituted benzazolo[3,2-a]quinolinium salts upon enzymatic reduction. Toxicol In Vitro 2007; 21:1155-64. [PMID: 17466486 PMCID: PMC2001286 DOI: 10.1016/j.tiv.2007.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Revised: 02/16/2007] [Accepted: 03/03/2007] [Indexed: 11/16/2022]
Abstract
The DNA binding capacity of two nitro-substituted benzazolo[3,2-a]quinolinium chlorides (NBQs), NBQ-38 and NBQ-95, was evaluated upon their enzymatic reduction with hypoxanthine (HX)/xanthine oxidase (XO) under anaerobic conditions. In the presence of 2'-deoxyguanosine (2'-dG) or calf thymus DNA, covalent-addition products were monitored. Reactions of each NBQ with 2'-dG or DNA differed in the NBQ to HX molar ratio. Control reactions, one without HX/OX and another under aerobic conditions, were also analyzed. Adducts were isolated and characterized by high performance liquid chromatography (HPLC) and electrospray ionization-mass spectrometry (ESI-MS). Authentic samples of the reduced forms of these NBQs, identified as ABQ-38 and ABQ-95, were synthesized as standards to monitor bioreduction processes. HPLC analysis showed that the yield of formation of an unknown product (possibly, 2'-dG-NHBQ-38 adduct) from the reaction of NBQ-38 with 2'-dG and DNA was proportional to the HX to NBQ-38 molar ratio. ESI-MS analysis of the DNA hydrolysates showed evidence of an adduct formed upon bioreduction of NBQ-38 by the ions detection at m/z 528.3 and 454.8, consistent with chemical structures of a 2'-dG-NHBQ-38 adduct and a fragment ion. DNA adducts were not observed with NBQ-95, although the corresponding bioreduction product ABQ-95 was detected by ESI-MS. This study provides mechanistic information of these bioreductively-activated pro-drugs with potential therapeutic applications.
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Affiliation(s)
- Beatriz Zayas
- School of Environmental Affairs, Universidad Metropolitana, San Juan, Puerto Rico.
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Shi X, Mandel SM, Platz MS. On the mechanism of reaction of radicals with tirapazamine. J Am Chem Soc 2007; 129:4542-50. [PMID: 17381087 DOI: 10.1021/ja0647405] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ketyl radicals produced by photolysis of ketones or di-tert-butyl peroxide (DTBP) in alcohol solvents react rapidly with tirapazamine (TPZ). The acetone ketyl radical (ACOH) reacts with TPZ with an absolute second-order rate constant of (9.7 +/- 0.4) x 108 M-1 s-1. The reaction kinetics can be followed by monitoring the bleaching of TPZ absorption at 475 nm or the formation of a reaction product which absorbs at 320 and 410 nm. The ACOD radical reacts with TPZ in 2-propanol-OD with an absolute rate constant of (6.7 +/- 0.5) x 108 M-1 s-1, corresponding to a kinetic isotope effect (KIE) of 1.4. Deuteration of the radical on carbon (ACOH-d6) retards the reaction of the radical with TPZ even further (absolute rate constant = (4.8 +/- 0.04) x 108 M-1 s-1). This result corresponds to a KIE of 2.0. Radicals derived from dioxane and diisopropyl ether by flash photolysis of DTBP in ethereal solvent react with TPZ more slowly than do ketyl radicals. It is concluded that ketyl radicals react, in part, with TPZ in organic solvents by transfer of a hydrogen atom from the OH and CH3 groups of the ketyl radical to the oxygen atom at the N4 position of TPZ to form acetone or acetone enol and a radical derivative of TPZ (TPZH). The latter species absorbs at 320 and 405 nm, has a lifetime of hundreds of microseconds in alcohol solvents, and decays by disproportionation to form TPZ and a reduced heterocycle. The reduced heterocycle eventually forms a desoxytirapazamine by a polar mechanism. The results are supported by density functional theory calculations. It is proposed that dioxanyl radical will also react, in part, with TPZ by transfer of a hydrogen atom from the carbon adjacent to the radical center to the oxygen atom at the N4 position of TPZ. This produces the enol ether and the previously mentioned TPZH radical. It is further posited that ether radicals react a bit more slowly than ketyl radicals because they lack the second mode of hydrogen transfer (from the OH group) that is present in the ACOH radical. Our data are permissive of the possibility that ether radicals add to TPZ at a rate that is competitive with beta-hydrogen atom transfer.
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Affiliation(s)
- Xiaofeng Shi
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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Lee K, Roth RA, LaPres JJ. Hypoxia, drug therapy and toxicity. Pharmacol Ther 2007; 113:229-46. [PMID: 17046066 DOI: 10.1016/j.pharmthera.2006.08.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 08/07/2006] [Indexed: 12/18/2022]
Abstract
Hypoxia is defined as a decrease in available oxygen reaching the tissues of the body. It is linked to the pathology of cancer, cardiovascular disease, and stroke, the leading causes of death in the United States. Cells under hypoxic stress either induce an adaptive response that includes increasing the rates of glycolysis and angiogenesis or undergo cell death by promoting apoptosis or necrosis. The ability of cells to maintain a balance between adaptation and cell death is regulated by a family of transcription factors called the hypoxia inducible factors (HIF). HIF1, the most widely studied HIF, is essential for regulating the expression of a battery of hypoxia-responsive genes involved in the adaptive and cell death responses. The ability of HIF1 to balance these 2 responses likely lies in the regulation of HIF1alpha stability and transcriptional activity by post-translational hydroxylation and its ability to respond to other cellular factors including key metabolites and growth factors. Targeting HIF1 signaling for therapeutics, therefore, requires an understanding of how these various signals converge upon HIF1 and regulate its role in maintaining the balance between adaptation and cell death. In addition, one must understand how this balance can be perturbed during toxicant-induced tissue damage. This review will summarize our current understanding of hypoxia signaling as it applies to drug therapy and toxicity and describe how these processes can influence the HIF-mediated balance between adaptation and cell death.
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Affiliation(s)
- KangAe Lee
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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Razskazovskiy Y, Close DM. Alkyl radical adducts of aromatic N-oxides as hydrogen-abstracting agents: The reactivity of phenazine-N,N′-dioxide-methyl radical adduct. RESEARCH ON CHEMICAL INTERMEDIATES 2006. [DOI: 10.1163/156856706778400325] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Anderson RF, Shinde SS, Hay MP, Denny WA. Potentiation of the cytotoxicity of the anticancer agent tirapazamine by benzotriazine N-oxides: the role of redox equilibria. J Am Chem Soc 2006; 128:245-9. [PMID: 16390153 DOI: 10.1021/ja0559101] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tirapazamine (3-amino-1,2,4-benzotriazine 1,4-dioxide), the lead bioreductive drug with selective toxicity for hypoxic cells in tumors, is thought to act by forming an active oxidizing radical of high one-electron reduction potential, E(1), when reduced by reductases. It has a dual mechanism of action, both generating DNA radicals, following its one-electron reduction and subsequently oxidizing these DNA radicals to form labile cations or hydrolyzable lactones through transferring an O atom, resulting in DNA strand breaks. These parallel secondary reactions have been proposed to be also initiated by its two-electron reduced metabolite, the 1-oxide. We have used pulse radiolysis to show that the benzotriazinyl radical of a highly soluble analogue of tirapazamine, the 3-(N,N-dimethyl-1,2-ethanediamine) analogue, is able to oxidize tirapazamine itself. We have found that both tirapazamine and the 1-oxides are in equilibrium with their respective benzotriazinyl radicals, with high concentrations of the more soluble 1-oxide maintaining a high concentration of the more reactive oxidizing radical of tirapazamine. The one-electron reduction potentials, E(1), of the 1-oxides and related compounds have been measured and, together with the E(1) values of tirapazamine and the 2-nitroimidazole radiosensitizer, misonidazole, are shown to predict the published percentages of electron transfer. This radical chemistry study gives an insight into the mechanisms of the potentiation of radical damage, reported for DNA, that underlies the hypoxic cytotoxicity of electron affinic compounds. The E(1) values of the benzotriazinyl radicals of the benzotriazine compounds govern the position of the redox equilibria, which determine the amount of initial radical damage. The E(1) values of the 1,4-dioxides and 1-oxide compounds govern the degree of potentiation of the initial radical damage once formed.
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Affiliation(s)
- Robert F Anderson
- Department of Chemistry and Auckland Cancer Society Research Centre, The University of Auckland, Private Bag 92019, Auckland 1, New Zealand.
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Huxham LA, Kyle AH, Baker JHE, McNicol KL, Minchinton AI. Tirapazamine causes vascular dysfunction in HCT-116 tumour xenografts. Radiother Oncol 2006; 78:138-45. [PMID: 16455148 DOI: 10.1016/j.radonc.2006.01.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2005] [Revised: 12/19/2005] [Accepted: 01/06/2006] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND PURPOSE Tirapazamine is a hypoxic cytotoxin currently undergoing Phase II/III clinical evaluation in combination with radiation and chemotherapeutics for the treatment of non-hematological cancers. Tissue penetration studies using multicellular models have suggested that tirapazamine exposure may be limited to cells close to blood vessels. However, animal studies show tirapazamine enhances the anti-tumour activity of radiation and chemotherapy and clinical studies with tirapazamine, so far, are promising. To investigate this apparent paradox we examined the microregional effects of tirapazamine in vivo by mapping drug effects with respect to the position of blood vessels in tumour cryosections. PATIENTS AND METHODS Tirapazamine was administered i.p. to mice bearing HCT-116 tumours, which were excised at various times after treatment. Images of multiple-stained cryosections were overlaid to provide microregional information on the relative position of proliferating cells, hypoxia, perfusion and vasculature. RESULTS We observed extensive and permanent vascular dysfunction in a large proportion of tumours from mice treated with tirapazamine. In the affected tumours, blood flow ceased in the centrally located tumour vessels, leaving a rim of functional vessels around the periphery of the tumour. This vascular dysfunction commenced within 24 h after tirapazamine administration and the areas affected appeared to be replaced by necrosis over the following 24-48 h. CONCLUSIONS Because the majority of hypoxic cells are located in the center of tumours we propose that the activity of tirapazamine in vivo may be related to its effects on tumour vasculature and that its activity against hypoxic cells located distal to functional blood vessels may not be as important as previously believed.
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Affiliation(s)
- Lynsey A Huxham
- Medical Biophysics Department, British Columbia Cancer Research Centre, Vancouver, British Columbia, Canada
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Smith HO, Jiang CS, Weiss GR, Hallum AV, Liu PY, Robinson WR, Cheng PC, Scudder SA, Markman M, Alberts DS. Tirapazamine plus cisplatin in advanced or recurrent carcinoma of the uterine cervix: a Southwest Oncology Group study. Int J Gynecol Cancer 2006; 16:298-305. [PMID: 16445649 DOI: 10.1111/j.1525-1438.2006.00339.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The objective of this study was to determine objective response and overall survival (OS) and progression-free survival (PFS) following cisplatin plus tirapazamine treatment in eligible consenting patients with metastatic or recurrent squamous or adenosquamous carcinoma of the cervix. Treatment consisted of intravenous tirapazamine, 260 mg/m(2), followed by cisplatin, 75 mg/m(2), every 21 days for six cycles. Of 56 registered cases, 52 were evaluable for toxicity. There were six grade 4 toxicities (anemia [three], dyspnea [one], neutropenia/granulocytopenia [one], and dehydration [one]). Fifty-three patients were evaluable for response, OS, and PFS. The 6-month OS rate was 56.6% (95% CI 43.3-69.9%). The objective response rate was 32.1% (4 complete [2 confirmed and 2 unconfirmed] and 13 partial [8 confirmed and 5 unconfirmed]). Higher response rates (16/34 [47.1%] vs 1/19 [5.3%], P= 0.0018) were observed in patients who had not previously received radiation-sensitizing chemotherapy, as were OS and PFS (13.9 vs 4.0 months, P < 0.0001; 5.3 vs 1.8 months, P= 0.01). The OS was considered too low to warrant further testing in this disease setting. Despite this, tirapazamine plus cisplatin was active in patients who had not received cisplatin previously. Prior use of radiosensitizing chemotherapy impacted response and survival significantly and should be considered in future clinical trials.
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Affiliation(s)
- H O Smith
- Department of Obstetrics and Gynecology, 1 University of New Mexico Health Sciences Center, MSC 10 5580, Albuquerque, NM 87131-5286, USA.
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Abstract
Bioreductive drugs are inactive prodrugs that are converted into potent cytotoxins under conditions of either low oxygen tension or in the presence of high levels of specific reductases. The biochemical basis for selectivity relies on the ability of oxygen to reverse the activation process and the presence of elevated reductase levels in some tumour types. Key criteria for an ideal bioreductive drug should include poor activity against aerobic cells, activation over a broad range of oxygen tensions and, penetration through the aerobic fraction of cells. In addition, the active drug should be capable of killing non-proliferating cells. Numerous compounds are currently at various stages of drug development but Mitomycin C, which is generally considered to be the prototype bioreductive drug, is the only one in clinical use today. Of the drugs currently being evaluated clinically, tirapazamine has definite clinical activity against a variety of solid tumours when used in combination with cisplatin. Other drugs, such as EO9 and various nitroimidazoles, have not been impressive in the clinic and further development is required to improve properties such as drug delivery in the case of indoloquinones. A novel approach to exploiting tumour hypoxia is the development of a gene-directed enzyme prodrug therapy (GDEPT) strategy, where a gene encoding for a prodrug activating enzyme has been placed under the control of a hypoxia responsive promoter sequence. It is generally recognised that bioreductive drugs must be directed towards patients whose tumours have hypoxic regions or have appropriate enzymological characteristics. In terms of identifying tumour hypoxia, there has been considerable progress in the development of nitroimidazole based hypoxia markers that can be detected either via non-invasive or invasive procedures. Another strategy currently undergoing preclinical evaluation is the use of agents that modulate tumour blood flow and synergistic effects have been reported between bioreductive drugs and photodynamic therapy or inhibitors of nitric oxide synthase for example. The development of clinically useful bioreductive drugs depends therefore on the expertise of scientists and clinicians with varying backgrounds. The purpose of this review is to describe and critically assess recent developments in this field, with particular emphasis being placed on drug development and strategies aimed at optimising bioreductive drug activity.
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Affiliation(s)
- R M Phillips
- Clinical Oncology Unit, University of Bradford, Bradford, BD7 1DP, UK
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Li LC, Zha D, Zhu YQ, Xu MH, Wong NB. Theoretical study of the mechanism of hydroxyl radical release from tirapazamine’s undergoing enzymatic catalysis. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.04.040] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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