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Identification of AGT and CD44 in methotrexate-resistant colorectal cancer and reversal of methotrexate-resistance. Pathol Res Pract 2021; 229:153717. [PMID: 34952427 DOI: 10.1016/j.prp.2021.153717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 11/03/2021] [Accepted: 11/25/2021] [Indexed: 11/21/2022]
Abstract
This study aims to screen out hub genes in 2 methotrexate-resistant colorectal cancer (CRC) cells (HT29 and Caco2), compared with parental CRC cells and reverse methotrexate-resistance in methotrexate-resistant CRC. GEO database and R software were utilized to analyze the gene expression profiles GSE11440 and GSE16066. Venn diagram was used to identify intersection differentially expressed genes (DEGs) between GSE11440 and GSE16066. Protein-protein interaction (PPI) was utilized to screen out central node genes. Hub genes were determined by volcano graphs, heatmaps and box plots. The functional enrichment analysis was exhibited with DAVID. The GEPIA was used to obtain survival curves to analyze association between patient prognosis and hub genes. Western blotting was used to detect the expressions of hub genes. CCK-8 assay was used to show MTX-resistant CRC cell viability following CD44 inhibitor (THIQ) and AGT inhibitor (O6-BG) treatments. In our results, there were 180 intersection DEGs between GSE11440 and GSE16066. CD44 and AGT were screened out as hub genes by PPI, heatmaps, volcano and box plots. In the 2 MTX-resistant CRC cells, the expressions of CD44 and AGT were up-regulated compared with parental CRC cells. The results of western blotting showed that CD44 and AGT were up-regulated in MTX-resistant HT29 and Caco2 cells compared with parental CRC cells. CCK-8 assay results showed that the combination of MTX with O6-BG or THIQ could significantly reduce the activity of MTX-resistant CRC cells. This research screened out CD44 and AGT in MTX-resistant CRC cells by bioinformatics and suggested that the combination of MTX with O6-BG or THIQ could enhance the sensitivity of MTX-resistant CRC cells to MTX. This research provides a new strategy for overcoming MTX-resistance in CRC.
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Penketh PG, Williamson HS, Baumann RP, Shyam K. Design Strategy for the EPR Tumor-Targeting of 1,2-Bis(sulfonyl)-1-alkylhydrazines. Molecules 2021; 26:molecules26020259. [PMID: 33419160 PMCID: PMC7825511 DOI: 10.3390/molecules26020259] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 12/30/2020] [Accepted: 01/01/2021] [Indexed: 02/04/2023] Open
Abstract
A design strategy for macromolecular prodrugs is described, that are expected to exhibit robust activity against most solid tumor types while resulting in minimal toxicities to normal tissues. This approach exploits the enhanced permeability, and retention (EPR) effect, and utilizes carefully engineered rate constants to selectively target tumor tissue with short-lived cytotoxic moieties. EPR based tumor accumulation (half-life ~ 15 h) is dependent upon the ubiquitous abnormal solid tumor capillary morphology and is expected to be independent of individual tumor cell genetic variability that leads to resistance to molecularly targeted agents. The macromolecular sulfonylhydrazine-based prodrugs hydrolyze spontaneously with long half-life values (~10 h to >300 h dependent upon their structure) resulting in the majority of the 1,2-bis(sulfonyl)-1-alkylhydrazines (BSHs) cytotoxic warhead being released only after tumor sequestration. The very short half-life (seconds) of the finally liberated BSHs localizes the cytotoxic stress to the tumor target site by allowing insufficient time for escape. Thus, short lifespan anticancer species are liberated, and exhibit their activity largely within the tumor target. The abnormal tumor cell membrane pH gradients favor the uptake of BSHs compared to that of normal cells, further enhancing their selectivity. The reliance on physicochemical/chemical kinetic parameters and the EPR effect is expected to reduce response variability, and the acquisition of resistance.
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Affiliation(s)
- Philip G. Penketh
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA; (R.P.B.); (K.S.)
- Correspondence:
| | | | - Raymond P. Baumann
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA; (R.P.B.); (K.S.)
| | - Krishnamurthy Shyam
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510, USA; (R.P.B.); (K.S.)
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Penketh P, Williamson H, Shyam K. Physicochemical Considerations of Tumor Selective Drug Delivery and Activity Confinement with Particular Reference to 1,2-Bis(Sulfonyl)-1- Alkylhydrazines Delivery. Curr Drug Deliv 2020; 17:362-374. [PMID: 32342817 PMCID: PMC7499353 DOI: 10.2174/1567201817666200427215044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 10/21/2019] [Accepted: 03/12/2020] [Indexed: 02/04/2023]
Abstract
Hypoxic tumor cell sub-populations are highly resistant to radiotherapy and their presence frequently causes disease recurrence and death. Here, we described the physicochemical properties required to develop superior tumor-targeted hypoxia-activated modular prodrugs that liberate extremely short-lived bis(sulfonyl)hydrazines (BSHs) as reactive cytotoxins, thereby precisely focusing cytotoxic stress on these radio-resistant hypoxic sub-populations. Therefore, cytotoxic stress will be focused on radiation resistant areas and thus strongly synergizing with radiotherapy.
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Affiliation(s)
- Philip Penketh
- Address correspondence to this author at the Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA;
Tel: 2032309516; E-mail:
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Reductive Activity and Mechanism of Hypoxia- Targeted AGT Inhibitors: An Experimental and Theoretical Investigation. Int J Mol Sci 2019; 20:ijms20246308. [PMID: 31847200 PMCID: PMC6941096 DOI: 10.3390/ijms20246308] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 12/05/2019] [Accepted: 12/10/2019] [Indexed: 11/16/2022] Open
Abstract
O6-alkylguanine-DNA alkyltransferase (AGT) is the main cause of tumor cell resistance to DNA-alkylating agents, so it is valuable to design tumor-targeted AGT inhibitors with hypoxia activation. Based on the existing benchmark inhibitor O6-benzylguanine (O6-BG), four derivatives with hypoxia-reduced potential and their corresponding reduction products were synthesized. A reductase system consisting of glucose/glucose oxidase, xanthine/xanthine oxidase, and catalase were constructed, and the reduction products of the hypoxia-activated prodrugs under normoxic and hypoxic conditions were determined by high-performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The results showed that the reduction products produced under hypoxic conditions were significantly higher than that under normoxic condition. The amount of the reduction product yielded from ANBP (2-nitro-6-(3-amino) benzyloxypurine) under hypoxic conditions was the highest, followed by AMNBP (2-nitro-6-(3-aminomethyl)benzyloxypurine), 2-NBP (2-nitro-6-benzyloxypurine), and 3-NBG (O6-(3-nitro)benzylguanine). It should be noted that although the levels of the reduction products of 2-NBP and 3-NBG were lower than those of ANBP and AMNBP, their maximal hypoxic/normoxic ratios were higher than those of the other two prodrugs. Meanwhile, we also investigated the single electron reduction mechanism of the hypoxia-activated prodrugs using density functional theory (DFT) calculations. As a result, the reduction of the nitro group to the nitroso was proven to be a rate-limiting step. Moreover, the 2-nitro group of purine ring was more ready to be reduced than the 3-nitro group of benzyl. The energy barriers of the rate-limiting steps were 34–37 kcal/mol. The interactions between these prodrugs and nitroreductase were explored via molecular docking study, and ANBP was observed to have the highest affinity to nitroreductase, followed by AMNBP, 2-NBP, and 3-NBG. Interestingly, the theoretical results were generally in a good agreement with the experimental results. Finally, molecular docking and molecular dynamics simulations were performed to predict the AGT-inhibitory activity of the four prodrugs and their reduction products. In summary, simultaneous consideration of reduction potential and hypoxic selectivity is necessary to ensure that such prodrugs have good hypoxic tumor targeting. This study provides insights into the hypoxia-activated mechanism of nitro-substituted prodrugs as AGT inhibitors, which may contribute to reasonable design and development of novel tumor-targeted AGT inhibitors.
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Sharpe MA, Raghavan S, Baskin DS. PAM-OBG: A monoamine oxidase B specific prodrug that inhibits MGMT and generates DNA interstrand crosslinks, potentiating temozolomide and chemoradiation therapy in intracranial glioblastoma. Oncotarget 2018; 9:23923-23943. [PMID: 29844863 PMCID: PMC5963626 DOI: 10.18632/oncotarget.25246] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 04/08/2018] [Indexed: 12/31/2022] Open
Abstract
Via extensive analyses of genetic databases, we have characterized the DNA-repair capacity of glioblastoma with respect to patient survival. In addition to elevation of O6-methylguanine DNA methyltransferase (MGMT), down-regulation of three DNA repair pathways; canonical mismatch repair (MMR), Non-Homologous End-Joining (NHEJ), and Homologous Recombination (HR) are correlated with poor patient outcome. We have designed and tested both in vitro and in vivo, a monoamine oxidase B (MAOB) specific prodrug, PAM-OBG, that is converted by glioma MAOB into the MGMT inhibitor O6-benzylguanine (O6BG) and the DNA crosslinking agent acrolein. In cultured glioma cells, we show that PAM-OBG is converted to O6BG, inhibiting MGMT and sensitizing cells to DNA alkylating agents such as BCNU, CCNU, and Temozolomide (TMZ). In addition, we demonstrate that the acrolein generated is highly toxic in glioma treated with an inhibitor of Nucleotide Excision Repair (NER). In mouse intracranial models of primary human glioma, we show that PAM-OBG increases survival of mice treated with either BCNU or CCNU by a factor of six and that in a chemoradiation model utilizing six rounds of TMZ/2Gy radiation, pre-treatment with PAM-OBG more than doubled survival time.
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Affiliation(s)
- Martyn A Sharpe
- Department of Neurosurgery, Kenneth R. Peak Brain and Pituitary Tumor Center, Houston Methodist Hospital, TX 77030, Houston, USA
| | - Sudhir Raghavan
- Department of Neurosurgery, Kenneth R. Peak Brain and Pituitary Tumor Center, Houston Methodist Hospital, TX 77030, Houston, USA
| | - David S Baskin
- Department of Neurosurgery, Kenneth R. Peak Brain and Pituitary Tumor Center, Houston Methodist Hospital, TX 77030, Houston, USA
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Miggiano R, Valenti A, Rossi F, Rizzi M, Perugino G, Ciaramella M. Every OGT Is Illuminated … by Fluorescent and Synchrotron Lights. Int J Mol Sci 2017; 18:ijms18122613. [PMID: 29206193 PMCID: PMC5751216 DOI: 10.3390/ijms18122613] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 11/28/2017] [Accepted: 11/30/2017] [Indexed: 12/23/2022] Open
Abstract
O6-DNA-alkyl-guanine-DNA-alkyl-transferases (OGTs) are evolutionarily conserved, unique proteins that repair alkylation lesions in DNA in a single step reaction. Alkylating agents are environmental pollutants as well as by-products of cellular reactions, but are also very effective chemotherapeutic drugs. OGTs are major players in counteracting the effects of such agents, thus their action in turn affects genome integrity, survival of organisms under challenging conditions and response to chemotherapy. Numerous studies on OGTs from eukaryotes, bacteria and archaea have been reported, highlighting amazing features that make OGTs unique proteins in their reaction mechanism as well as post-reaction fate. This review reports recent functional and structural data on two prokaryotic OGTs, from the pathogenic bacterium Mycobacterium tuberculosis and the hyperthermophilic archaeon Sulfolobus solfataricus, respectively. These studies provided insight in the role of OGTs in the biology of these microorganisms, but also important hints useful to understand the general properties of this class of proteins.
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Affiliation(s)
- Riccardo Miggiano
- DSF-Dipartimento di Scienze del Farmaco, University of Piemonte Orientale, Via Bovio 6, 28100 Novara, Italy.
| | - Anna Valenti
- Institute of Biosciences and BioResources, National Research Council of Italy, Via Pietro Castellino 111, 80131 Naples, Italy.
| | - Franca Rossi
- DSF-Dipartimento di Scienze del Farmaco, University of Piemonte Orientale, Via Bovio 6, 28100 Novara, Italy.
| | - Menico Rizzi
- DSF-Dipartimento di Scienze del Farmaco, University of Piemonte Orientale, Via Bovio 6, 28100 Novara, Italy.
| | - Giuseppe Perugino
- Institute of Biosciences and BioResources, National Research Council of Italy, Via Pietro Castellino 111, 80131 Naples, Italy.
| | - Maria Ciaramella
- Institute of Biosciences and BioResources, National Research Council of Italy, Via Pietro Castellino 111, 80131 Naples, Italy.
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Penketh PG, Finch RA, Sauro R, Baumann RP, Ratner ES, Shyam K. pH-dependent general base catalyzed activation rather than isocyanate liberation may explain the superior anticancer efficacy of laromustine compared to related 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine prodrugs. Chem Biol Drug Des 2017. [PMID: 28636806 DOI: 10.1111/cbdd.13057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Laromustine (also known as cloretazine, onrigin, VNP40101M, 101M) is a prodrug of 90CE, a short-lived chloroethylating agent with anticancer activity. The short half-life of 90CE necessitates the use of latentiated prodrug forms for in vivo treatments. Alkylaminocarbonyl-based prodrugs such as laromustine exhibit significantly superior in vivo activity in several murine tumor models compared to analogs utilizing acyl, and alkoxycarbonyl latentiating groups. The alkylaminocarbonyl prodrugs possess two exclusive characteristics: (i) They are primarily unmasked by spontaneous base catalyzed elimination; and (ii) they liberate a reactive carbamoylating species. Previous speculations as to the therapeutic superiority of laromustine have focused upon the inhibition of enzymes by carbamoylation. We have investigated the therapeutic interactions of analogs with segregated chloroethylating and carbamoylating activities (singly and in combination) in the in vivo murine L1210 leukemia model. The combined treatment with chloroethylating and carbamoylating prodrugs failed to result in any synergism and produced a reduction in the therapeutic efficacy compared to the chloroethylating prodrug alone. Evidence supporting an alternative explanation for the superior tumor selectivity of laromustine is presented that is centered upon the high pH sensitivity of its base catalyzed activation, and the more alkaline intracellular pH values commonly found within tumor cells.
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Affiliation(s)
- Philip G Penketh
- Department of Obstetrics, Gynecology & Reproductive Sciences, Yale University School of Medicine, New Haven, CT, USA
| | - Richard A Finch
- Department of Veterinary Sciences, The University of Texas MD Anderson Cancer Center, Bastrop, TX, USA
| | - Rachel Sauro
- Department of Obstetrics, Gynecology & Reproductive Sciences, Yale University School of Medicine, New Haven, CT, USA
| | - Raymond P Baumann
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Elena S Ratner
- Department of Obstetrics, Gynecology & Reproductive Sciences, Yale University School of Medicine, New Haven, CT, USA
| | - Krishnamurthy Shyam
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
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8
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Abstract
DNA-damaging agents, such as methylating agents, chloroethylating agents and platinum-based agents, have been extensively used as anticancer drugs. However, the side effects, high toxicity, lack of selectivity and resistance severely limit their clinical applications. In recent years, a strategy combining a DNA-damaging agent with a bioactive molecule (e.g., enzyme inhibitors) or carrier (e.g., steroid hormone and DNA intercalators) to produce a new 'combi-molecule' with improved efficacy or selectivity has been attempted to overcome these drawbacks. The combi-molecule simultaneously acts on two targets and is expected to possess better potency than the parent compounds. Many studies have shown DNA-damaging combi-molecules exhibiting excellent anticancer activity in vitro and in vivo. This review focuses on the development of combi-molecules, which possess increased DNA-damaging potency, anticancer efficacy and tumor selectivity and reduced side reactions than the parent compounds. The future opportunities and challenges in the discovery of combi-molecules were also discussed.
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Measurement of O 6 -alkylguanine-DNA alkyltransferase activity in tumour cells using stable isotope dilution HPLC-ESIMS/MS. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1033-1034:138-146. [PMID: 27544051 DOI: 10.1016/j.jchromb.2016.08.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Revised: 08/01/2016] [Accepted: 08/06/2016] [Indexed: 11/21/2022]
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Identification of the Structural Features of Guanine Derivatives as MGMT Inhibitors Using 3D-QSAR Modeling Combined with Molecular Docking. Molecules 2016; 21:molecules21070823. [PMID: 27347909 PMCID: PMC6273773 DOI: 10.3390/molecules21070823] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 06/08/2016] [Accepted: 06/18/2016] [Indexed: 01/29/2023] Open
Abstract
DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), which plays an important role in inducing drug resistance against alkylating agents that modify the O6 position of guanine in DNA, is an attractive target for anti-tumor chemotherapy. A series of MGMT inhibitors have been synthesized over the past decades to improve the chemotherapeutic effects of O6-alkylating agents. In the present study, we performed a three-dimensional quantitative structure activity relationship (3D-QSAR) study on 97 guanine derivatives as MGMT inhibitors using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods. Three different alignment methods (ligand-based, DFT optimization-based and docking-based alignment) were employed to develop reliable 3D-QSAR models. Statistical parameters derived from the models using the above three alignment methods showed that the ligand-based CoMFA (Qcv2 = 0.672 and Rncv2 = 0.997) and CoMSIA (Qcv2 = 0.703 and Rncv2 = 0.946) models were better than the other two alignment methods-based CoMFA and CoMSIA models. The two ligand-based models were further confirmed by an external test-set validation and a Y-randomization examination. The ligand-based CoMFA model (Qext2 = 0.691, Rpred2 = 0.738 and slope k = 0.91) was observed with acceptable external test-set validation values rather than the CoMSIA model (Qext2 = 0.307, Rpred2 = 0.4 and slope k = 0.719). Docking studies were carried out to predict the binding modes of the inhibitors with MGMT. The results indicated that the obtained binding interactions were consistent with the 3D contour maps. Overall, the combined results of the 3D-QSAR and the docking obtained in this study provide an insight into the understanding of the interactions between guanine derivatives and MGMT protein, which will assist in designing novel MGMT inhibitors with desired activity.
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Li L, Wang W, Ding M, Luo G, Liang Q. Single-Cell-Arrayed Agarose Chip for in Situ Analysis of Cytotoxicity and Genotoxicity of DNA Cross-Linking Agents. Anal Chem 2016; 88:6734-42. [PMID: 27269449 DOI: 10.1021/acs.analchem.6b01008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Development of approach or device to allow continuous multiple measurements, such as integrating cytotoxic and genotoxic analysis, is quite appealing for study of the drug's activity and mechanism of action or resistance. In this study, a single-cell-arrayed agarose chip system was developed to combine cell cultivation with subsequent in situ analysis of cytotoxicity and genotoxicity of the chemotherapeutic agent. The modified alkaline comet assay coupled with the Live/Dead assay was used to monitor the interstrand cross-links (ICLs) formation and the cytotoxic effects in different glioma cell lines. In addition, the ICL-induced double strand breaks (DSBs) was measured on the chip to reflect the level of ICLs indirectly. Compared with the traditional methods, the microarray agarose device offers higher throughput, reproducibility, and robustness, exhibiting good potential for high-content drug screening.
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Affiliation(s)
- Lili Li
- Beijing Key Lab of Microanalytical Methods & Instrumentation, Key Lab of Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China
| | - Weixing Wang
- Beijing Key Lab of Microanalytical Methods & Instrumentation, Key Lab of Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China
| | - Mingyu Ding
- Beijing Key Lab of Microanalytical Methods & Instrumentation, Key Lab of Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China
| | - Guoan Luo
- Beijing Key Lab of Microanalytical Methods & Instrumentation, Key Lab of Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China
| | - Qionglin Liang
- Beijing Key Lab of Microanalytical Methods & Instrumentation, Key Lab of Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University , Beijing 100084, P. R. China
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Sun G, Zhang N, Zhao L, Fan T, Zhang S, Zhong R. Synthesis and antitumor activity evaluation of a novel combi-nitrosourea prodrug: Designed to release a DNA cross-linking agent and an inhibitor of O(6)-alkylguanine-DNA alkyltransferase. Bioorg Med Chem 2016; 24:2097-107. [PMID: 27041398 DOI: 10.1016/j.bmc.2016.03.041] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 03/22/2016] [Accepted: 03/25/2016] [Indexed: 10/22/2022]
Abstract
The drug resistance of CENUs induced by O(6)-alkylguanine-DNA alkyltransferase (AGT), which repairs the O(6)-alkylated guanine and subsequently inhibits the formation of dG-dC cross-links, hinders the application of CENU chemotherapies. Therefore, the discovery of CENU analogs with AGT inhibiting activity is a promising approach leading to novel CENU chemotherapies with high therapeutic index. In this study, a new combi-nitrosourea prodrug 3-(3-(((2-amino-9H-purin-6-yl)oxy)methyl)benzyl)-1-(2-chloroethyl)-1-nitrosourea (6), designed to release a DNA cross-linking agent and an inhibitor of AGT, was synthesized and evaluated for its antitumor activity and ability to induce DNA interstrand cross-links (ICLs). The results indicated that 6 exhibited higher cytotoxicity against mer(+) glioma cells compared with ACNU, BCNU, and their respective combinations with O(6)-benzylguanine (O(6)-BG). Quantifications of dG-dC cross-links induced by 6 were performed using HPLC-ESI-MS/MS. Higher levels of dG-dC cross-link were observed in 6-treated human glioma SF763 cells (mer(+)), whereas lower levels of dG-dC cross-link were observed in 6-treated calf thymus DNA, when compared with the groups treated with BCNU and ACNU. The results suggested that the superiority of 6 might result from the AGT inhibitory moiety, which specifically functions in cells with AGT activity. Molecular docking studies indicated that five hydrogen bonds were formed between the O(6)-BG analogs released from 6 and the five residues in the active pocket of AGT, which provided a reasonable explanation for the higher AGT-inhibitory activity of 6 than O(6)-BG.
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Affiliation(s)
- Guohui Sun
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, PR China
| | - Na Zhang
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, PR China
| | - Lijiao Zhao
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, PR China.
| | - Tengjiao Fan
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, PR China
| | - Shufen Zhang
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, PR China
| | - Rugang Zhong
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, PR China
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Ishiguro K, Zhu YL, Lin ZP, Penketh PG, Shyam K, Zhu R, Baumann RP, Sartorelli AC, Rutherford TJ, Ratner ES. Cataloging antineoplastic agents according to their effectiveness against platinum-resistant and platinum-sensitive ovarian carcinoma cell lines. JOURNAL OF TRANSLATIONAL SCIENCE 2016; 2:117-124. [PMID: 27076919 DOI: 10.15761/jts.1000127] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Although epithelial ovarian cancers (EOCs) are initially treated with platinum-based chemotherapy, EOCs vary in platinum responsiveness. Cataloging antineoplastic agents according to their effectiveness against platinum-resistant and platinum-sensitive EOC cell lines is valuable for development of therapeutic strategies to avoid platinum inefficacy and to exploit platinum sensitivity. TOV-21G devoid of FANCF expression, OV-90 and SKOV-3 were employed as examples of platinum-sensitive, platinum-intermediate and platinum-resistant cell lines, respectively. Antineoplastic agents examined included mitomycin C, doxorubicin, etoposide, gemcitabine, chlorambucil, paclitaxel, triapine and X-rays. Their effectiveness against cell lines was analyzed by clonogenic assays. Cytotoxic profiles of mitomycin C and carboplatin were similar, with mitomycin C exhibiting greater potency and selectivity against TOV-21G than carboplatin. Cytotoxic profiles of doxorubicin, etoposide and X-rays overlapped with that of carboplatin, while OV-90 overexpressing Rad51 was more resistant to chlorambucil than SKOV-3. The efficacy of paclitaxel and triapine was independent of platinum sensitivity or resistance. Consistent with these cytotoxic profiles, cisplatin/mitomycin C, triapine, and paclitaxel differed in the capacity to induce phosphorylation of H2AX, and produced unique inhibitory patterns of DNA/RNA syntheses in HL-60 human leukemia cells. Paclitaxel and triapine in combination produced additive antitumor effects in M109 murine lung carcinoma. In conclusion, mitomycin C is potentially more effective against Fanconi anemia pathway-deficient EOCs than carboplatin. Doxorubicin and etoposide, because of their overlapping cytotoxic properties with carboplatin, are unlikely to be efficacious against platinum-refractory EOCs. Paclitaxel and triapine are effective regardless of platinum sensitivity status, and promising in combination for both platinum-sensitive and platinum-refractory EOCs.
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Affiliation(s)
- Kimiko Ishiguro
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Yong-Lian Zhu
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Z Ping Lin
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Philip G Penketh
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Krishnamurthy Shyam
- Department of Pharmacology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Rui Zhu
- Department of Pharmacology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Raymond P Baumann
- Department of Pharmacology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Alan C Sartorelli
- Department of Pharmacology, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Thomas J Rutherford
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Elena S Ratner
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
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Shyam K, Penketh PG, Baumann RP, Finch RA, Zhu R, Zhu YL, Sartorelli AC. Antitumor sulfonylhydrazines: design, structure-activity relationships, resistance mechanisms, and strategies for improving therapeutic utility. J Med Chem 2015; 58:3639-71. [PMID: 25612194 DOI: 10.1021/jm501459c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
1,2-Bis(sulfonyl)-1-alkylhydrazines (BSHs) were conceived as more specific DNA guanine O-6 methylating and chloroethylating agents lacking many of the undesirable toxicophores contained in antitumor nitrosoureas. O(6)-Alkylguanine-DNA alkyltransferase (MGMT) is the sole repair protein for O(6)-alkylguanine lesions in DNA and has been reported to be absent in 5-20% of most tumor types. Many BSHs exhibit highly selective cytotoxicity toward cells deficient in MGMT activity. The development of clinically useful MGMT assays should permit the identification of tumors with this vulnerability and allow for the preselection of patient subpopulations with a high probability of responding. The BSH system is highly versatile, permitting the synthesis of many prodrug types with the ability to incorporate an additional level of tumor-targeting due to preferential activation by tumor cells. Furthermore, it may be possible to expand the spectrum of activity of these agents to include tumors with MGMT activity by combining them with tumor-targeted MGMT inhibitors.
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Affiliation(s)
- Krishnamurthy Shyam
- †Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
| | - Philip G Penketh
- †Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
| | - Raymond P Baumann
- †Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
| | - Rick A Finch
- ‡Department of Veterinary Sciences, The University of Texas M.D. Anderson Cancer Center, 650 Cool Water Drive, Bastrop, Texas 78602, United States
| | - Rui Zhu
- †Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
| | - Yong-Lian Zhu
- †Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
| | - Alan C Sartorelli
- †Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
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15
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Ishiguro K, Lin ZP, Penketh PG, Shyam K, Zhu R, Baumann RP, Zhu YL, Sartorelli AC, Rutherford TJ, Ratner ES. Distinct mechanisms of cell-kill by triapine and its terminally dimethylated derivative Dp44mT due to a loss or gain of activity of their copper(II) complexes. Biochem Pharmacol 2014; 91:312-22. [PMID: 25130544 DOI: 10.1016/j.bcp.2014.08.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 08/02/2014] [Accepted: 08/04/2014] [Indexed: 12/11/2022]
Abstract
Triapine, currently being evaluated as an antitumor agent in phase II clinical trials, and its terminally dimethylated derivative Dp44mT share the α-pyridyl thiosemicarbazone backbone that functions as ligands for transition metal ions. Yet, Dp44mT is approximately 100-fold more potent than triapine in cytotoxicity assays. The aims of this study were to elucidate the mechanisms underlying their potency disparity and to determine their kinetics of cell-kill in culture to aid in the formulation of their clinical dosing schedules. The addition of Cu(2+) inactivated triapine in a 1:1 stoichiometric fashion, while it potentiated the cytotoxicity of Dp44mT. Clonogenic assays after finite-time drug-exposure revealed that triapine produced cell-kill in two phases, one completed within 20 min that caused limited cell-kill, and the other occurring after 16 h of exposure that produced extensive cell-kill. The ribonucleotide reductase inhibitor triapine at 0.4 μM caused immediate complete arrest of DNA synthesis, whereas Dp44mT at this concentration did not appreciably inhibit DNA synthesis. The inhibition of DNA synthesis by triapine was reversible upon its removal from the medium. Cell death after 16 h exposure to triapine paralleled the appearance of phospho-(γ)H2AX, a marker of DNA double-strand breaks induced by collapse of DNA replication forks after prolonged replication arrest. In contrast to triapine, Dp44mT produced robust cell-kill within 1h in a concentration-dependent manner. The short-term action of both agents was prevented by thiols, indicative of the involvement of reactive oxygen species. The time dependency in the production of cell-kill by triapine should be considered in treatment regimens.
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Affiliation(s)
- Kimiko Ishiguro
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Yale University School of Medicine, New Haven, CT 06520, United States.
| | - Z Ping Lin
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Philip G Penketh
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Krishnamurthy Shyam
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Rui Zhu
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Raymond P Baumann
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Yong-Lian Zhu
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Alan C Sartorelli
- Department of Pharmacology and Developmental Therapeutics Program, Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Thomas J Rutherford
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Elena S Ratner
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Yale University School of Medicine, New Haven, CT 06520, United States.
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16
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Penketh PG, Patridge E, Shyam K, Baumann RP, Zhu R, Ishiguro K, Sartorelli AC. Influence of glutathione and glutathione S-transferases on DNA interstrand cross-link formation by 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine, the active anticancer moiety generated by laromustine. Chem Res Toxicol 2014; 27:1440-9. [PMID: 25012050 PMCID: PMC4137992 DOI: 10.1021/tx500197t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
![]()
Prodrugs
of 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine
(90CE) are promising anticancer agents. The 90CE moiety is a readily
latentiated, short-lived (t1/2 ∼
30 s) chloroethylating agent that can generate high yields of oxophilic
electrophiles responsible for the chloroethylation of the O-6 position
of guanine in DNA. These guanine O-6 alkylations are believed to be
responsible for the therapeutic effects of 90CE and its prodrugs.
Thus, 90CE demonstrates high selectivity toward tumors with diminished
levels of O6-alkylguanine-DNA alkyltransferase
(MGMT), the resistance protein responsible for O6-alkylguanine repair. The formation of O6-(2-chloroethyl)guanine lesions ultimately leads to the generation
of highly cytotoxic 1-(N3-cytosinyl),-2-(N1-guaninyl)ethane DNA interstrand cross-links
via N1,O6-ethanoguanine
intermediates. The anticancer activity arising from this sequence
of reactions is thus identical to this component of the anticancer
activity of the clinically used chloroethylnitrosoureas. Herein, we
evaluate the ability of glutathione (GSH) and other low molecular
weight thiols, as well as GSH coupled with various glutathione S-transferase enzymes (GSTs) to attenuate the final yields
of cross-links generated by 90CE when added prior to or immediately
following the initial chloroethylation step to determine the major
point(s) of interaction. In contrast to studies utilizing BCNU as
a chloroethylating agent by others, GSH (or GSH/GST) did not appreciably
quench DNA interstrand cross-link precursors. While thiols alone offered
little protection at either alkylation step, the GSH/GST couple was
able to diminish the initial yields of cross-link precursors. 90CE
exhibited a very different GST isoenzyme susceptibility to that reported
for BCNU, this could have important implications in the relative resistance
of tumor cells to these agents. The protection afforded by GSH/GST
was compared to that produced by MGMT.
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Affiliation(s)
- Philip G Penketh
- Department of Pharmacology and Yale Cancer Center, Yale University School of Medicine , New Haven, Connecticut 06520, United States
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17
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Sun G, Zhao L, Fan T, Li S, Zhong R. Investigations on the Effect of O6-Benzylguanine on the Formation of dG-dC Interstrand Cross-Links Induced by Chloroethylnitrosoureas in Human Glioma Cells Using Stable Isotope Dilution High-Performance Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometry. Chem Res Toxicol 2014; 27:1253-62. [PMID: 24914620 DOI: 10.1021/tx500143b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Guohui Sun
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Lijiao Zhao
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Tengjiao Fan
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Sisi Li
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
| | - Rugang Zhong
- Beijing Key Laboratory of Environmental & Viral Oncology, College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, P. R. China
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18
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Larabi R, Abtouche S, Brahimi M. Theoretical study of methyl group transfer assisted by proton transfer reaction in the N-acylated imidates. J Mol Model 2014; 20:2302. [DOI: 10.1007/s00894-014-2302-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 05/12/2014] [Indexed: 11/28/2022]
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19
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Penketh PG, Shyam K, Zhu R, Baumann RP, Ishiguro K, Sartorelli AC. Influence of phosphate and phosphoesters on the decomposition pathway of 1,2-bis(methylsulfonyl)-1-(2-chloroethyhydrazine (90CE), the active anticancer moiety generated by Laromustine, KS119, and KS119W. Chem Res Toxicol 2014; 27:818-33. [PMID: 24618018 PMCID: PMC4033638 DOI: 10.1021/tx500004y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Prodrugs of the short-lived chloroethylating
agent 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine
(90CE) and its methylating analogue 1,2-bis(methylsulfonyl)-1-(methyl)hydrazine
(KS90) are potentially useful anticancer agents. This class of agents
frequently yields higher ratios of therapeutically active oxophilic
electrophiles responsible for DNA O6-guanine
alkylations to other electrophiles with lower therapeutic relevance
than the nitrosoureas. This results in improved selectivity toward
tumors with diminished levels of O6-alkylguanine-DNA
alkyltransferase (MGMT), the resistance protein responsible for O6-alkylguanine repair. The formation of O6-(2-chloroethyl)guanine, which leads to the
formation of a DNA–DNA interstrand cross-link, accounts for
the bulk of the anticancer activity of 90CE prodrugs. Herein, we describe
a new decomposition pathway that is available to 90CE but not to its
methylating counterpart. This pathway appears to be subject to general/acid
base catalysis with phosphate (Pi), phosphomonoesters, and phosphodiesters,
being particularly effective. This pathway does not yield a chloroethylating
species and results in a major change in nucleophile preference since
thiophilic rather than oxophilic electrophiles are produced. Thus,
a Pi concentration dependent decrease in DNA–DNA interstand
cross-link formation was observed. Changes in 90CE decomposition products
but not alkylation kinetics occurred in the presence of Pi since the
prebranch point elimination of the N-1 methanesulfinate moiety remained
the rate-limiting step. The Pi catalyzed route is expected to dominate
at Pi and phosphoester concentrations totaling >25–35 mM.
In
view of the abundance of Pi and phosphoesters in cells, this pathway
may have important effects on agent toxicity, tumor selectivity, and
resistance to prodrugs of 90CE. Furthermore, it may be possible to
design analogues that diminish this thiophile-generating pathway,
which is likely superfluous at best and potentially detrimental to
the targeting of hypoxic regions where Pi concentrations can be significantly
elevated.
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Affiliation(s)
- Philip G Penketh
- Department of Pharmacology and Yale Cancer Center, Yale University School of Medicine , 333 Cedar Street, New Haven, Connecticut 06520-8066, United States
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20
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Chloroethylating and methylating dual function antineoplastic agents display superior cytotoxicity against repair proficient tumor cells. Bioorg Med Chem Lett 2013; 23:1853-9. [PMID: 23395657 DOI: 10.1016/j.bmcl.2013.01.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Revised: 12/20/2012] [Accepted: 01/02/2013] [Indexed: 11/20/2022]
Abstract
Two new agents based upon the structure of the clinically active prodrug laromustine were synthesized. These agents, 2-(2-chloroethyl)-N-methyl-1,2-bis(methylsulfonyl)-N-nitrosohydrazinecarboxamide (1) and N-(2-chloroethyl)-2-methyl-1,2-bis(methylsulfonyl)-N-nitrosohydrazinecarboxamide (2), were designed to retain the potent chloroethylating and DNA cross-linking functions of laromustine, and gain the ability to methylate DNA at the O-6 position of guanine, while lacking the carbamoylating activity of laromustine. The methylating arm was introduced with the intent of depleting the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT). Compound 1 is markedly more cytotoxic than laromustine in both AGT minus EMT6 mouse mammary carcinoma cells and high AGT expressing DU145 human prostate carcinoma cells. DNA cross-linking studies indicated that its cross-linking efficiency is nearly identical to its predicted active decomposition product, 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine (90CE), which is also produced by laromustine. AGT ablation studies in DU145 cells demonstrated that 1 can efficiently deplete AGT. Studies assaying methanol and 2-chloroethanol production as a consequence of the methylation and chloroethylation of water by 1 and 2 confirmed their ability to function as methylating and chloroethylating agents and provided insights into the superior activity of 1.
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21
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Ishiguro K, Shyam K, Penketh PG, Baumann RP, Sartorelli AC, Rutherford TJ, Ratner ES. Expression of O6-Methylguanine-DNA Methyltransferase Examined by Alkyl-Transfer Assays, Methylation-Specific PCR and Western Blots in Tumors and Matched Normal Tissue. ACTA ACUST UNITED AC 2013; 4:919-931. [PMID: 23946891 DOI: 10.4236/jct.2013.44103] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The tumor selectivity of alkylating agents that produce guanine O6-chloroethyl (laromustine and carmustine) and O6-methyl (temozolomide) lesions, depends upon O6-methylguanine-DNA methyltransferase (MGMT) activity being lower in tumor than in host tissue. Despite the established role of MGMT as a tumor resistance factor, consensus on how to assess MGMT expression in clinical samples is unsettled. The aim of this study is to examine the relationship between the values derived from distinctive MGMT measurements in 13, 12, 6 and 2 pairs of human tumors and matched normal adjacent tissue from the colon, kidney, lung and liver, respectively, and in human cell lines. The MGMT measurements included (a) alkyl-transfer assays using [benzene-3H]O6-benzylguanine as a substrate to assess functional MGMT activity, (b) methylation-specific PCR (MSP) to probe MGMT gene promoter CpG methylations as a measure of gene silencing, and (c) western immunoblots to analyze the MGMT protein. In human cell lines, a strict negative correlation existed between MGMT activity and the extent of promoter methylation. In tissue specimens, by contrast, the correlation between these two variables was low. Moreover, alkyl-transfer assays identified 3 pairs of tumors and normal tissue with tumor-selective reduction in MGMT activity in the absence of promoter methylation. Cell line MGMT migrated as a single band in western analyses, whereas tissue MGMT was heterogeneous around its molecular size and at much higher molecular masses, indicative of multi-layered post-translational modifications. Malignancy is occasionally associated with a mobility shift in MGMT. Contrary to the prevalent expectation that MGMT expression is governed at the level of gene silencing, these data suggest that other mechanisms that can lead to tumor-selective reduction in MGMT activity exist in human tissue.
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Affiliation(s)
- Kimiko Ishiguro
- Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, USA
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22
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Zhu R, Seow HA, Baumann RP, Ishiguro K, Penketh PG, Shyam K, Sartorelli AC. Design of a hypoxia-activated prodrug inhibitor of O6-alkylguanine-DNA alkyltransferase. Bioorg Med Chem Lett 2012; 22:6242-7. [PMID: 22932317 DOI: 10.1016/j.bmcl.2012.08.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/24/2012] [Accepted: 08/01/2012] [Indexed: 11/15/2022]
Abstract
The efficacy of agents that alkylate the O-6 position of guanine is inhibited by O(6)-alkylguanine-DNA alkyltransferase (AGT) which removes these lesions from the tumor DNA. To increase differential toxicity, inhibitors must selectively deplete AGT in tumors, while sparing normal tissues where this protein serves a protective function. A newly synthesized prodrug of the AGT inhibitor O(6)-benzylguanine (O(6)-BG) with an α,α-dimethyl-4-nitrobenzyloxycarbonyl moiety masking the essential 2-amino group has demonstrated the feasibility of targeting hypoxic regions that are unique to solid tumors, for drug delivery. However, these modifications resulted in greatly decreased solubility. Recently, new potent global AGT inhibitors with improved formulatability such as O(6)-[(3-aminomethyl)benzylguanine (1) have been developed. However, acetylamino (N-(3-(((2-amino-9H-purin-6-yl)oxy)methyl)benzyl)acetamide) (2) exhibits a pronounced decrease in activity. Thus, 1 would be inactivated by N-acetylation and probably N-glucuronidation. To combat potential conjugational inactivation while retaining favorable solubility, we synthesized 6-((3-((dimethylamino)methyl)benzyl)oxy)-9H-purin-2-amine (3) in which the 3-aminomethyl moiety is protected by methylation; and to impart tumor selectivity we synthesized 2-(4-nitrophenyl)propan-2-yl(6-((3-((dimethylamino)methyl)benzyl)oxy)-9H-purin-2-yl)carbamate (7), a hypoxia targeted prodrug of 3 utilizing an α,α-dimethyl-4-nitrobenzyloxycarbonyl moiety. Consistent with this design, 7 demonstrates both hypoxia selective conversion by EMT6 cells of 7 to 3 and hypoxic sensitization of AGT containing DU145 cells to the cytotoxic actions of laromustine, while exhibiting improved solubility.
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Affiliation(s)
- Rui Zhu
- Department of Pharmacology and Developmental Therapeutics Program, Cancer Center, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8066, United States
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23
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Kim EY, Liu Y, Akintujoye OM, Shyam K, Grove TA, Sartorelli AC, Rockwell S. Preliminary studies with a new hypoxia-selective cytotoxin, KS119W, in vitro and in vivo. Radiat Res 2012; 178:126-37. [PMID: 22862779 DOI: 10.1667/rr2934.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Agents with selective toxicity to hypoxic cells have shown promise as adjuncts to radiotherapy. Our previous studies showed that the bioreductive alkylating agent KS119 had an extremely large differential toxicity to severely hypoxic and aerobic cells in cell culture, and was effective in killing the hypoxic cells of EMT6 mouse mammary tumors in vivo. However, the limited solubility of that compound precluded its development as an anticancer drug. Here we report our initial studies with KS119W, a water-soluble analog of KS119. The cytotoxicity of KS119W to EMT6 cells in vitro was similar to that of KS119, with both agents producing only minimal cytotoxicity to aerobic cells even after intensive treatments, while producing pronounced cytotoxicity to oxygen-deficient cells. This resulted in large differentials in the toxicities to hypoxic and aerobic cells (>1,000-fold at 10 μM). Low pH had only minimal effects on the cytotoxicity of KS119W. Under hypoxic conditions, EMT6 cells transfected to express high levels of either human or mouse versions of the repair protein O(6)-alkylguanine-DNA alkyltransferase, which is also known as O(6)-methylguanine DNA-methyltransferase, were much more resistant to KS119W than parental EMT6 cells lacking O(6)-alkylguanine-DNA alkyltransferase, confirming the importance of DNA O-6-alkylation to the cytotoxicity of this agent. Studies with EMT6 tumors in BALB/c Rw mice using both tumor cell survival and tumor growth delay assays showed that KS119W was effective as an adjunct to irradiation for the treatment of solid tumors in vivo, producing additive or supra-additive effects in most combination regimens for which the interactions could be evaluated. Our findings encourage additional preclinical studies to examine further the antineoplastic effects of KS119W alone and in combination with radiation, and to examine the pharmacology and toxicology of this new bioreductive alkylating agent so that its potential for clinical use as an adjuvant to radiotherapy can be evaluated.
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Affiliation(s)
- Eugene Y Kim
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520-8040, USA
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24
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Penketh PG, Shyam K, Baumann RP, Ishiguro K, Patridge EV, Zhu R, Sartorelli AC. A strategy for selective O(6)-alkylguanine-DNA alkyltransferase depletion under hypoxic conditions. Chem Biol Drug Des 2012; 80:279-90. [PMID: 22553921 DOI: 10.1111/j.1747-0285.2012.01401.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cellular resistance to chemotherapeutics that alkylate the O-6 position of guanine residues in DNA correlates with their O(6)-alkylguanine-DNA alkyltransferase activity. In normal cells high [O(6)-alkylguanine-DNA alkyltransferase] is beneficial, sparing the host from toxicity, whereas in tumor cells high [O(6)-alkylguanine-DNA alkyltransferase] prevents chemotherapeutic response. Therefore, it is necessary to selectively inactivate O(6)-alkylguanine-DNA alkyltransferase in tumors. The oxygen-deficient compartment unique to solid tumors is conducive to reduction, and could be utilized to provide this selectivity. Therefore, we synthesized 2-nitro-6-benzyloxypurine, an analog of O(6)-benzylguanine in which the essential 2-amino group is replaced by a nitro moiety, and 2-nitro-6-benzyloxypurine is >2000-fold weaker than O(6)-benzylguanine as an O(6)-alkylguanine-DNA alkyltransferase inhibitor. We demonstrate oxygen concentration sensitive net reduction of 2-nitro-6-benzyloxypurine by cytochrome P450 reductase, xanthine oxidase, and EMT6, DU145, and HL-60 cells to yield O(6)-benzylguanine. We show that 2-nitro-6-benzyloxypurine treatment depletes O(6)-alkylguanine-DNA alkyltransferase in intact cells under oxygen-deficient conditions and selectively sensitizes cells to laromustine (an agent that chloroethylates the O-6 position of guanine) under oxygen-deficient but not normoxic conditions. 2-Nitro-6-benzyloxypurine represents a proof of concept lead compound; however, its facile reduction (E(1/2) - 177 mV versus Ag/AgCl) may result in excessive oxidative stress and/or the generation of O(6)-alkylguanine-DNA alkyltransferase inhibitors in normoxic regions in vivo.
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Affiliation(s)
- Philip G Penketh
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA.
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25
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Rockwell S, Liu Y, Seow HA, Ishiguro K, Baumann RP, Penketh PG, Shyam K, Akintujoye OM, Glazer PM, Sartorelli AC. Preclinical evaluation of Laromustine for use in combination with radiation therapy in the treatment of solid tumors. Int J Radiat Biol 2011; 88:277-85. [PMID: 22111842 DOI: 10.3109/09553002.2012.638359] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE These studies explored questions related to the potential use of Laromustine in the treatment of solid tumors and in combination with radiotherapy. MATERIALS AND METHODS The studies used mouse EMT6 cells (both parental and transfected with genes for O(6)-alkylguanine-DNA transferase [AGT]), repair-deficient human Fanconi Anemia C and Chinese hamster VC8 (BRCA2(-/-)) cells and corresponding control cells, and EMT6 tumors in mice assayed using cell survival and tumor growth assays. RESULTS Hypoxia during Laromustine treatment did not protect EMT6 cells or human fibroblasts from this agent. Rapidly proliferating EMT6 cells were more sensitive than quiescent cultures. EMT6 cells expressing mouse or human AGT, which removes O(6)-alkyl groups from DNA guanine, thereby protecting against G-C crosslink formation, increased resistance to Laromustine. Crosslink-repair-deficient Fanconi Anemia C and VC8 cells were hypersensitive to Laromustine, confirming the importance of crosslinks as lethal lesions. In vitro, Laromustine and radiation produced additive toxicities to EMT6 cells. Studies using tumor cell survival and tumor growth assays showed effects of regimens combining Laromustine and radiation that were compatible with additive or subadditive interactions. CONCLUSIONS The effects of Laromustine on solid tumors and with radiation are complex and are influenced by microenvironmental and proliferative heterogeneity within these malignancies.
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Affiliation(s)
- Sara Rockwell
- Department of Therapeutic Radiology, Yale Comprehensive Cancer Center, Yale University School of Medicine, New Haven, Connecticut 06520-8040, USA.
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26
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Perugino G, Vettone A, Illiano G, Valenti A, Ferrara MC, Rossi M, Ciaramella M. Activity and regulation of archaeal DNA alkyltransferase: conserved protein involved in repair of DNA alkylation damage. J Biol Chem 2011; 287:4222-31. [PMID: 22167184 DOI: 10.1074/jbc.m111.308320] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Agents that form methylation adducts in DNA are highly mutagenic and carcinogenic, and organisms have evolved specialized cellular pathways devoted to their repair, including DNA alkyltransferases. These are proteins conserved in eucarya, bacteria and archaea, acting by a unique reaction mechanism, which leads to direct repair of DNA alkylation damage and irreversible protein alkylation. The alkylated form of DNA alkyltransferases is inactive, and in eukaryotes, it is rapidly directed to degradation. We report here in vitro and in vivo studies on the DNA alkyltransferase from the thermophilic archaeon Sulfolobus solfataricus (SsOGT). The development of a novel, simple, and sensitive fluorescence-based assay allowed a careful characterization of the SsOGT biochemical and DNA binding activities. In addition, transcriptional and post-translational regulation of SsOGT by DNA damage was studied. We show that although the gene transcription is induced by alkylating agent treatment, the protein is degraded in vivo by an alkylation-dependent mechanism. These experiments suggest a striking conservation, from archaea to humans, of this important pathway safeguarding genome stability.
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Affiliation(s)
- Giuseppe Perugino
- Institute of Protein Biochemistry, Consiglio Nazionale delle Ricerche, Via P. Castellino 111, 80131 Naples, Italy
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Pegg AE. Multifaceted roles of alkyltransferase and related proteins in DNA repair, DNA damage, resistance to chemotherapy, and research tools. Chem Res Toxicol 2011; 24:618-39. [PMID: 21466232 DOI: 10.1021/tx200031q] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
O(6)-Alkylguanine-DNA alkyltransferase (AGT) is a widely distributed, unique DNA repair protein that acts as a single agent to directly remove alkyl groups located on the O(6)-position of guanine from DNA restoring the DNA in one step. The protein acts only once, and its alkylated form is degraded rapidly. It is a major factor in counteracting the mutagenic, carcinogenic, and cytotoxic effects of agents that form such adducts including N-nitroso-compounds and a number of cancer chemotherapeutics. This review describes the structure, function, and mechanism of action of AGTs and of a family of related alkyltransferase-like proteins, which do not act alone to repair O(6)-alkylguanines in DNA but link repair to other pathways. The paradoxical ability of AGTs to stimulate the DNA-damaging ability of dihaloalkanes and other bis-electrophiles via the formation of AGT-DNA cross-links is also described. Other important properties of AGTs include the ability to provide resistance to cancer therapeutic alkylating agents, and the availability of AGT inhibitors such as O(6)-benzylguanine that might overcome this resistance is discussed. Finally, the properties of fusion proteins in which AGT sequences are linked to other proteins are outlined. Such proteins occur naturally, and synthetic variants engineered to react specifically with derivatives of O(6)-benzylguanine are the basis of a valuable research technique for tagging proteins with specific reagents.
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Affiliation(s)
- Anthony E Pegg
- Department of Cellular and Molecular Physiology, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine , Pennsylvania 17033, United States.
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KS900: A hypoxia-directed, reductively activated methylating antitumor prodrug that selectively ablates O(6)-alkylguanine-DNA alkyltransferase in neoplastic cells. Biochem Pharmacol 2011; 81:1201-10. [PMID: 21396917 DOI: 10.1016/j.bcp.2011.02.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 02/24/2011] [Accepted: 02/28/2011] [Indexed: 11/22/2022]
Abstract
To most effectively treat cancer it may be necessary to preferentially destroy tumor tissue while sparing normal tissues. One strategy to accomplish this is to selectively cripple the involved tumor resistance mechanisms, thereby allowing the affected anticancer drugs to gain therapeutic efficacy. Such an approach is exemplified by our design and synthesis of the intracellular hypoxic cell activated methylating agent, 1,2-bis(methylsulfonyl)-1-methyl-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS900) that targets the O-6 position of guanine in DNA. KS900 is markedly more cytotoxic in clonogenic experiments under conditions of oxygen deficiency than the non-intracellularly activated agents KS90, and 90M, when tested in O(6)-alkylguanine-DNA alkyltransferase (AGT) non-expressing cells (EMT6 mouse mammary carcinoma, CHO/AA8 hamster ovary, and U251 human glioma), and than temozolomide when tested in AGT expressing cells (DU145 human prostate carcinoma). Furthermore, KS900 more efficiently ablates AGT in HL-60 human leukemia and DU145 cells than the spontaneous globally activated methylating agent KS90, with an IC(50) value over 9-fold lower than KS90. Finally, KS900 under oxygen-deficient conditions selectively sensitizes DU145 cells to the chloroethylating agent, onrigin, through the ablation of the resistance protein AGT. Thus, under hypoxia, KS900 is more cytotoxic at substantially lower concentrations than methylating agents such as temozolomide that are not preferentially activated in neoplastic cells by intracellular reductase catalysts. The necessity for intracellular activation of KS900 permits substantially greater cytotoxic activity against cells containing the resistance protein O(6)-alkylguanine-DNA alkyltransferase (AGT) than agents such as temozolomide. Furthermore, the hypoxia-directed intracellular activation of KS900 allows it to preferentially ablate AGT pools under the oxygen-deficient conditions that are present in malignant tissue.
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