351
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Abstract
A high throughput assay (the DRAG test) is described, which could be a useful tool for the detection of repairable DNA adducts, and which is based on the inhibition of the growth of DNA repair-deficient Chinese hamster ovary (CHO) cells. The cytotoxicity of a test substance towards DNA repair-deficient CHO cell lines is compared with the corresponding cytotoxicity in the parental wild-type CHO cell line (AA8). A more pronounced toxicity toward a DNA repair-deficient cell line is interpreted as being the consequence of its inability to repair the DNA adduct induced by the compound. (+)-7beta,8alpha-Dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, camptothecin, ethyl methanesulphonate and mitomycin C were used as reference substances, and the overall results indicate that the DRAG test could be useful in the screening of compounds for the production of repairable DNA adducts. The main advantages with the DRAG test are that it provides a relevant endpoint, it is rapid, it requires small amounts of the test item, and it permits a large number of compounds to be tested.
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Affiliation(s)
- T Helleday
- Department of Genetic and Cellular Toxicology, Wallenberg Laboratory, Stockholm University, 106 91 Stockholm, Sweden
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352
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Arnaudeau C, Lundin C, Helleday T. DNA double-strand breaks associated with replication forks are predominantly repaired by homologous recombination involving an exchange mechanism in mammalian cells. J Mol Biol 2001; 307:1235-45. [PMID: 11292338 DOI: 10.1006/jmbi.2001.4564] [Citation(s) in RCA: 314] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
DNA double-strand breaks (DSB) represent a major disruption in the integrity of the genome. DSB can be generated when a replication fork encounters a DNA lesion. Recombinational repair is known to resolve such replication fork-associated DSB, but the molecular mechanism of this repair process is poorly understood in mammalian cells. In the present study, we investigated the molecular mechanism by which recombination resolves camptothecin (CPT)-induced DSB at DNA replication forks. The frequency of homologous recombination (HR) was measured using V79/SPD8 cells which contain a duplication in the endogenous hprt gene that is resolved by HR. We demonstrate that DSB associated with replication forks induce HR at the hprt gene in early S phase. Further analysis revealed that these HR events involve an exchange mechanism. Both the irs1SF and V3-3 cell lines, which are deficient in HR and non-homologous end joining (NHEJ), respectively, were found to be more sensitive than wild-type cells to DSB associated with replication forks. The irs1SF cell line was more sensitive in this respect than V3-3 cells, an observation consistent with the hypothesis that DSB associated with replication forks are repaired primarily by HR. The frequency of formation of DSB associated with replication forks was not affected in HR and NHEJ deficient cells, indicating that the loss of repair, rather than the formation of DSB associated with replication forks is responsible for the increased sensitivity of the mutant strains. We propose that the presence of DSB associated with replication forks rapidly induces HR via an exchange mechanism and that HR plays a more prominent role in the repair of such DSB than does NHEJ.
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Affiliation(s)
- C Arnaudeau
- Department of Genetic and Cellular Toxicology, Wallenberg Laboratory, Stockholm University, Stockholm, S-106 91, Sweden
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353
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Shao RG, Cao CX, Nieves-Neira W, Dimanche-Boitrel MT, Solary E, Pommier Y. Activation of the Fas pathway independently of Fas ligand during apoptosis induced by camptothecin in p53 mutant human colon carcinoma cells. Oncogene 2001; 20:1852-9. [PMID: 11313933 DOI: 10.1038/sj.onc.1204264] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2000] [Revised: 10/18/2000] [Accepted: 01/15/2001] [Indexed: 12/30/2022]
Abstract
The present study explored the role of the cell surface receptor Fas (CD95/APO-1) in apoptosis induced by camptothecin (CPT) in the HT29 colon carcinoma cell line. CPT-induced apoptosis was associated with high molecular weight DNA fragmentation as measured by filter elution. This fragmentation was inhibited by the caspase inhibitor, z-VAD-fmk and by cycloheximide, which also prevented proteolytic activation of caspase-3 and poly(ADP-ribose)polymerase cleavage. Under such conditions, Fas, Fas ligand, Bax, and p21 expression were increased and Fas recruited the FADD adaptor. Fas expression increase was blocked by cycloheximide but not by z-VAD-fmk, consistent with caspase activation downstream from Fas. Treatment of HT29 cells with FasL or with the CH-11 agonistic anti-Fas antibody potentiated the apoptotic response of cells treated with CPT. The anti-Fas blocking antibody ZB4 and the Fas-ligand inhibitor failed to protect HT29 cells from CPT-induced apoptosis. Such a protection was obtained by transient expression of constructs encoding a dominant-negative mutant of FADD, FADD in an antisense orientation and E8 or MC159 viral proteins that inhibit Fas-induced apoptosis at the level of FADD and procaspase-8, respectively. Together, these data show that topoisomerase I-mediated DNA damage-induced apoptosis involves activation of the Fas pathway without detectable Fas-ligand requirement in CPT-treated cells.
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Affiliation(s)
- R G Shao
- Laboratory of Molecular Pharmacology, Division of Basic Science, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA
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354
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Frøhlich RF, Hansen SG, Lisby M, Grainge I, Westergaard O, Jayaram M, Knudsen BR. Inhibition of Flp recombinase by the topoisomerase I-targeting drugs, camptothecin and NSC-314622. J Biol Chem 2001; 276:6993-7. [PMID: 11152668 DOI: 10.1074/jbc.c000901200] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recombinases of the lambda-Int family and type IB topoisomerases act by introducing transient single strand breaks in DNA using chemically identical reaction schemes. Recent structural data have supported the relationship between the two enzyme groups by revealing considerable similarities in the architecture of their catalytic pockets. In this study we show that the Int-type recombinase Flp is inhibited by the two structurally unrelated topoisomerase I-directed anti-cancer drugs, camptothecin (CPT) and NSC-314622. The interaction of these drugs with topoisomerase I is very specific with several single amino acid substitutions conferring drug resistance to the enzyme. Thus, the observed interaction of CPT and NSC-314622 with Flp, which is comparable to their interaction with the cleavage complex formed by topoisomerase I, strongly supports a close mechanistic and evolutionary relationship between the two enzymes. The results suggest that Flp and other Int family recombinases may provide model systems for dissecting the molecular mechanisms of topoisomerase I-directed anti-cancer therapeutic agents.
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Affiliation(s)
- R F Frøhlich
- Department of Molecular and Structural Biology, University of Aarhus, Building 130, C. F. Møllers Allé, DK-8000 Aarhus C, Denmark
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355
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Vanhoefer U, Harstrick A, Achterrath W, Cao S, Seeber S, Rustum YM. Irinotecan in the treatment of colorectal cancer: clinical overview. J Clin Oncol 2001; 19:1501-18. [PMID: 11230497 DOI: 10.1200/jco.2001.19.5.1501] [Citation(s) in RCA: 235] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE AND METHODS For more than three decades, the therapeutic options for patients with advanced colorectal cancer have almost exclusively been based on fluoropyrimidines. With the recognition that topoisomerase-I (TOP-I) is an important therapeutic target in cancer therapy, irinotecan, a semisynthetic TOP-I-interactive camptothecin derivative, has been clinically established in the treatment of colorectal cancer. RESULTS Irinotecan was investigated as second-line chemotherapy after prior treatment with fluorouracil (FU)-based regimens in two large randomized phase III trials comparing irinotecan with either best supportive care or an infusional FU/leucovorin (LV) regimen. The outcomes of these trials established irinotecan as the standard therapy in the second-line treatment of colorectal cancer. The therapeutic value of irinotecan in the first-line treatment of metastatic colorectal cancer was investigated in two large randomized phase III trials comparing the combination of irinotecan and FU/LV with FU/LV alone. Both trials demonstrated significant superior efficacy for the combination of irinotecan and FU/LV in terms of response rate, median time to disease progression, and median survival time. Consequently, the combination of irinotecan and FU/LV has been approved as first-line chemotherapy for patients with metastatic colorectal cancer and constitutes the reference therapy against which other treatment options must be tested in the future. CONCLUSION In this review, the clinical rationale and update of the present clinical status of irinotecan in the treatment of colorectal cancer and future prospects of irinotecan-based combinations are discussed.
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Affiliation(s)
- U Vanhoefer
- Department of Internal Medicine (Cancer Research), West German Cancer Center, University of Essen Medical School, Essen, Germany
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356
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Chen AY, Scruggs PB, Geng L, Rothenberg ML, Hallahan DE. p53 and p21 are major cellular determinants for DNA topoisomerase I-mediated radiation sensitization in mammalian cells. Ann N Y Acad Sci 2001; 922:298-300. [PMID: 11193905 DOI: 10.1111/j.1749-6632.2000.tb07047.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- A Y Chen
- Department of Radiation Oncology, Vanderbilt University Medical Center, 1301 22nd Ave. S., Vanderbilt Clinic, Nashville, TN 37232-5671, USA.
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357
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Adamec E, Mohan PS, Cataldo AM, Vonsattel JP, Nixon RA. Up-regulation of the lysosomal system in experimental models of neuronal injury: implications for Alzheimer's disease. Neuroscience 2001; 100:663-75. [PMID: 11098128 DOI: 10.1016/s0306-4522(00)00281-5] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Previous studies established that the populations of neurons that frequently degenerate in Alzheimer's disease exhibit robust up-regulation of the lysosomal system. In this study, we investigated alterations of the lysosomal system during different forms of experimental injury in rat hippocampal neurons in culture, utilizing a combination of immunocytochemical and biochemical methods. Using triple-label immnocytochemistry for activated caspase-3, fragmentation of DNA and the microtubule-associated protein-2, we characterized treatment paradigms as models of the apoptotic (staurosporine, camptothecin), the oncotic (high-dose menadione, glutamate), and the mixed apoptotic and oncotic (low-dose menadione) pathways of neuronal death. Slowly developing apoptotic or slowly developing mixed apoptotic and oncotic forms of neuronal injury were associated with substantial increases in the number and size of cathepsin D-positive vesicles (late endosomes and mature lysosomes) as determined by immunocytochemistry, and elevated levels of cathepsin D by western blotting. In agreement with our previous findings in Alzheimer's disease, where lysosomal system activation was not restricted to overtly degenerating neurons, up-regulation of this system was also detected quite early during the course of experimental neuronal injury, preceding the development of dystrophic neurites, nuclear segmentation or fragmentation of DNA. These findings implicate lysosomal system activation, both in Alzheimer's disease and in experimental models of neuronal injury, as an important event associated with early stages of neurodegeneration.
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Affiliation(s)
- E Adamec
- Mailman Research Center, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA.
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358
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Karayan L, Riou JF, Séité P, Migeon J, Cantereau A, Larsen CJ. Human ARF protein interacts with topoisomerase I and stimulates its activity. Oncogene 2001; 20:836-48. [PMID: 11314011 DOI: 10.1038/sj.onc.1204170] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2000] [Revised: 11/03/2000] [Accepted: 12/12/2000] [Indexed: 11/09/2022]
Abstract
The ARF gene (p19(ARF) in mouse and p14(ARF) in man) has become a central actor of the cell cycle regulation process as it participates to the ARF-MDM2-p53 pathway and the Rb-E2F-1 pathway. By use of immunoprecipitation and Western blotting (IP/WB), we now show that ARF physically associates with topoisomerase I (Topo I). ARF-Topo I immune complexes were detected in SF9 insect cells infected with recombinant baculoviruses encoding the two genes as well as in 293 cells that express endogenously these proteins. Preparations of a GST-ARF recombinant protein stimulated the DNA relaxation activity of Topo I but, in contrast, had no effect on the decatenation activity of Topo II. The Topo I stimulation was also detected in cell extracts of SF9 cells expressing both proteins. A confocal microscopy study indicated that part of ARF and Topo I colocalized in the granular component structure of the nucleolus. As a whole, our data indicate that Topo I is a new partner of ARF and suggest that ARF is involved in cell reactions that require Topo I.
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Affiliation(s)
- L Karayan
- Laboratoire d'Oncologie Moléculaire, FRE 2224 CNRS, Poitiers Cedex, France
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359
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Brehm BR, Bock C, Wesselborg S, Pfeiffer S, Schüler S, Schulze-Osthoff K. Prevention of human smooth muscle cell proliferation without induction of apoptosis by the topoisomerase I inhibitor topotecan. Biochem Pharmacol 2001; 61:119-27. [PMID: 11137716 DOI: 10.1016/s0006-2952(00)00514-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Despite significant improvements in the treatment of atherosclerotic disease involving procedures such as angioplasty, bypass grafting, endartherectomy, or stent implantation, secondary failure due to late restenosis still occurs in 30-50% of individuals. Restenosis and later stages of atherosclerotic lesions arise from a complex series of fibroproliferative responses to vascular injury that are triggered by potent growth-regulatory molecules and finally result in vascular smooth muscle cell proliferation, migration, and neointima formation. The aim of this study was to investigate the antiproliferative effects of the topoisomerase I inhibitor topotecan on human arterial coronary smooth muscle cells. Following incubation of cells with different drug concentrations, mitotic indices were measured by bromodeoxyuridine incorporation, while cellular mitochondrial activity was evaluated using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. Continuous incubation with topotecan for 7 days resulted in a complete and dose-dependent reduction of smooth muscle cell proliferation, and topotecan inhibited cell proliferation in the presence of growth factors as well. In contrast, mitochondrial activity was only partially decreased. Remarkably, although even short-term incubations for 20 min were sufficient to induce a long-lasting growth inhibition, topotecan did not induce apoptosis. Our results therefore suggest that, based on its drug profile, the topoisomerase I inhibitor topotecan may be a promising drug to inhibit restenosis occurring after coronary angioplasty with local devices.
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Affiliation(s)
- B R Brehm
- Department of Cardiology, University of Tübingen, Tübingen, Germany
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360
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Abstract
BACKGROUND Flow cytometry is a valuable tool for the study of cellular and molecular interactions. We sought to develop instrumentation that would allow accurate and precise inline dynamic temperature control of flow cytometry samples in order to expand the analytical capabilities of flow cytometry. METHODS Using a temperature controller, DC power supply, and a Peltier module, we designed a temperature control circuit that regulates the temperature of a heat transfer block. The heat transfer block surrounds the sample line to efficiently heat and cool the sample. We attached DNA oligomers to microspheres and observed the denaturation of fluorescently labeled complementary oligomers to verify that the sample was achieving the desired temperature. RESULTS The inline thermoregulation unit can ramp between 30 and 95 degrees C (>2 degrees C per second) within 30 s repeatedly. The accuracy of the instrument was verified by comparing the observed melting temperatures of the oligomer sets to the predicted values. These values varied within 6% of the predicted and were reproducible over a variety of conditions. CONCLUSIONS The apparatus we constructed accurately and dynamically controls the sample temperature of inline samples. Flow cytometers equipped with our inline thermoregulation unit will be able to conveniently use temperature as a robust experimental parameter.
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Affiliation(s)
- S W Graves
- National Flow Cytometry Resource, Biosciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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361
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Czuwara-Ladykowska J, Makiela B, Smith EA, Trojanowska M, Rudnicka L. The inhibitory effects of camptothecin, a topoisomerase I inhibitor, on collagen synthesis in fibroblasts from patients with systemic sclerosis. ARTHRITIS RESEARCH 2001; 3:311-8. [PMID: 11549373 PMCID: PMC64844 DOI: 10.1186/ar321] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2001] [Revised: 07/03/2001] [Accepted: 07/06/2001] [Indexed: 11/10/2022]
Abstract
The main manifestation of systemic sclerosis (SSc) is the overproduction of extracellular matrix, predominantly type I collagen. This study was undertaken to evaluate the effects of noncytotoxic doses of the topoisomerase I inhibitor camptothecin (CPT) on collagen production in the activated dermal fibroblasts from patients with SSc and healthy donors. The fibroblasts were cultured in the presence or absence of CPT. Production of collagenous proteins by fibroblasts was determined in cell and matrix layers by ELISA and in conditioned media by [(3)H]proline incorporation, gel electrophoresis, and autoradiography. Expression of alpha2(I) collagen (COL1A2) mRNA was measured by northern blot, and the activity of COL1A2 promoter was determined by a chloramphenicol acetyltransferase assay. CPT (10(-7) M) decreased the deposition of type I collagen by 68%, of type III by 38%, and of type VI by 21% in SSc fibroblasts and to a lesser degree in healthy controls. Similarly, CPT (10(-8) M to 10(-6) M) significantly inhibited secretion of newly synthesized collagenous proteins into conditioned media by 50%. CPT (10(-8) M to 10(-6) M) caused a significant dose-dependent inhibition of COL1A2 mRNA levels and COL1A2 promoter activity, both by as much as 60%. The inhibitory effect of CPT on collagen production by fibroblasts from patients with SSc suggests that topoisomerase I inhibitors may be effective in limiting fibrosis in such patients.
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Affiliation(s)
- J Czuwara-Ladykowska
- Department of Medicine, Division of Rheumatology and Immunology, Medical University of South Carolina, 96 Jonathan Lucas Street, Charleston, SC 29425, USA.
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362
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Hwang Y, Rhodes D, Bushman F. Rapid microtiter assays for poxvirus topoisomerase, mammalian type IB topoisomerase and HIV-1 integrase: application to inhibitor isolation. Nucleic Acids Res 2000; 28:4884-92. [PMID: 11121479 PMCID: PMC115247 DOI: 10.1093/nar/28.24.4884] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2000] [Revised: 10/31/2000] [Accepted: 10/31/2000] [Indexed: 11/15/2022] Open
Abstract
We have developed microtiter assays for detecting catalysis by type IB topoisomerases and retroviral integrases. Each assay employs model DNA substrates containing biotin in one strand and digoxigenin in another. In each case action of the enzyme results in the formation of a single DNA strand containing both groups. This allows the reaction product to be quantified by capturing biotinylated product DNA on avidin-coated plates followed by detection using an anti-digoxigenin ELISA. The order of addition of reactants and inhibitors can be varied to distinguish effects of test compounds on different steps in the reaction. These assays were used to screen compound libraries for inhibitors active against mammalian topoisomerase or HIV integrase. We identified (-)-epigallocatechin 3-O:-gallate, as a potent inhibitor of religation by mammalian topoisomerase (IC(50) of 26 nM), potentially explaining the anti-cancer properties previously attributed to this compound. New integrase inhibitors were also identified. A similar strategy may be used to develop microtiter assays for many further DNA modifying enzymes.
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Affiliation(s)
- Y Hwang
- Infectious Disease Laboratory, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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363
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Arimondo PB, Riou JF, Mergny JL, Tazi J, Sun JS, Garestier T, Hélène C. Interaction of human DNA topoisomerase I with G-quartet structures. Nucleic Acids Res 2000; 28:4832-8. [PMID: 11121473 PMCID: PMC115246 DOI: 10.1093/nar/28.24.4832] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Because of their role in the control of the topological state of DNA, topoisomerases are ubiquitous and vital enzymes, which participate in nearly all events related to DNA metabolism including replication and transcription. We show here that human topoisomerase I (Topo I) plays an unexpected role of 'molecular matchmaker' for G-quartet formation. G-quadruplexes are multi-stranded structures held together by square planes of four guanines ('G-quartets') interacting by forming Hoogsteen hydrogen bonds. Topo I is able to promote the formation of four-stranded intermolecular DNA structures when added to single-stranded DNA containing a stretch of at least five guanines. We provide evidence that these complexes are parallel G-quartet structures, mediated by tetrads of hydrogen-bonded guanine. In addition, Topo I binds specifically to pre-formed parallel and anti-parallel G4-DNA.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle CNRS UMR 8646, INSERM U201, 43 rue Cuvier, 75231 Paris cedex 05, France
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364
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Jerina DM, Sayer JM, Kroth H, Kohlhagen G, Laco GS, Pommier Y. Bay-Region Diol Epoxides of Benzo[a]Pyrene are Stealth Poisons of Topoisomerase I. Polycycl Aromat Compd 2000. [DOI: 10.1080/10406630008028523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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365
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Rangarajan M, Kim JS, Sim SP, Liu A, Liu LF, Lavoie EJ. Topoisomerase I inhibition and cytotoxicity of 5-bromo- and 5-phenylterbenzimidazoles. Bioorg Med Chem 2000; 8:2591-600. [PMID: 11092544 DOI: 10.1016/s0968-0896(00)00188-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Topoisomerase I is an enzyme that is essential for maintaining the three-dimensional structure of DNA during the processes of transcription, translation and mitosis. With the introduction of new clinical agents that are effective in poisoning topoisomerase I, this enzyme has proved to be an attractive molecular target in the development of anticancer drugs. Several terbenzimidazoles have been identified as potent topoisomerase I poisons. Structure-activity data on various terbenzimidazoles have revealed that the presence of lipophilic substituents at the 5-position of various terbenzimidazoles correlates with enhanced cytotoxicity. While the effect of having substituents at both the 5- and 6-positions had not been evaluated, previous studies did indicate that the presence of a fused benzo-ring at the 5,6-position results in a significant decrease in topoisomerase I poisoning activity and cytotoxicity. In the present study we investigated whether substituents at both the 5- and 6-positions of varied terbenzimidazoles would allow for retention of topo I poisoning activity. The 6-bromo, 6-methoxy, or 6-phenyl derivatives of both 5-bromo- and 5-phenylterbenzimidazole were synthesized and evaluated for topo I poisoning activity, as well as their cytotoxicity toward human lymphoblastoma cells. The data indicate that such derivatives do retain similar topo I poisoning activity and possess cytotoxicity equivalent to either 5-bromo- or 5-phenylterbenzimidazole. Significant enhancement in the topoisomerase I poisoning activity and cytotoxicity of 5-phenylterbenzimidazole is observed when the 2"-position is substituted with either a chloro or trifluoromethyl substituent. The influence of such substituents on the biological activity of 5.6-dibromoterbenzimidazole (6a) was also explored. In the case of either 2"-chloro-5,6-dibromoterbenzimidazole (6b) or 2"-trifluoromethyl-5,6-dibromoterbenzimidazole (6c), topoisomerase I poisoning was not enhanced relative to 6a. While cytotoxicity toward RPMI 8402 was also not significantly affected, comparative studies performed against several solid human tumor cell lines did reveal a significant increase in cytotoxicity observed for 6c as compared to 6a.
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Affiliation(s)
- M Rangarajan
- Department of Pharmaceutical Chemistry, Rutgers, The State University of New Jersey, Piscataway 08854, USA
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366
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Cheng C, Shuman S. Recombinogenic flap ligation pathway for intrinsic repair of topoisomerase IB-induced double-strand breaks. Mol Cell Biol 2000; 20:8059-68. [PMID: 11027276 PMCID: PMC86416 DOI: 10.1128/mcb.20.21.8059-8068.2000] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Topoisomerase IB catalyzes recombinogenic DNA strand transfer reactions in vitro and in vivo. Here we characterize a new pathway of topoisomerase-mediated DNA ligation in vitro (flap ligation) in which vaccinia virus topoisomerase bound to a blunt-end DNA joins the covalently held strand to a 5' resected end of a duplex DNA containing a 3' tail. The joining reaction occurs with high efficiency when the sequence of the 3' tail is complementary to that of the scissile strand immediately 5' of the cleavage site. A 6-nucleotide segment of complementarity suffices for efficient flap ligation. Invasion of the flap into the duplex apparently occurs while topoisomerase remains bound to DNA, thereby implying a conformational flexibility of the topoisomerase clamp around the DNA target site. The 3' flap acceptor DNA mimics a processed end in the double-strand-break-repair recombination pathway. Our findings suggest that topoisomerase-induced breaks may be rectified by flap ligation, with ensuing genomic deletions or translocations.
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Affiliation(s)
- C Cheng
- Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA
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367
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Pommier Y, Laco GS, Kohlhagen G, Sayer JM, Kroth H, Jerina DM. Position-specific trapping of topoisomerase I-DNA cleavage complexes by intercalated benzo[a]- pyrene diol epoxide adducts at the 6-amino group of adenine. Proc Natl Acad Sci U S A 2000; 97:10739-44. [PMID: 10995470 PMCID: PMC27093 DOI: 10.1073/pnas.190312697] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2000] [Accepted: 07/06/2000] [Indexed: 11/18/2022] Open
Abstract
DNA topoisomerase I (top1) is the target of potent anticancer agents, including camptothecins and DNA intercalators, which reversibly stabilize (trap) top1 catalytic intermediates (cleavage complexes). The aim of the present study was to define the structural relationship between the site(s) of covalently bound intercalating agents, whose solution conformations in DNA are known, and the site(s) of top1 cleavage. Two diastereomeric pairs of oligonucleotide 22-mers, derived from a sequence used to determine the crystal structure of top1-DNA complexes, were synthesized. One pair contained either a trans-opened 10R- or 10S-benzo[a]pyrene 7, 8-diol 9,10-epoxide adduct at the N(6)-amino group of a central 2'-deoxyadenosine residue in the scissile strand, and the other pair contained the same two adducts in the nonscissile strand. These adducts were derived from the (+)-(7R,8S,9S,10R)- and (-)-(7S,8R,9R, 10S)-7,8-diol 9,10-epoxides in which the benzylic 7-hydroxyl group and the epoxide oxygen are trans. On the basis of analogy with known solution conformations of duplex oligonucleotides containing these adducts, we conclude that top1 cleavage complexes are trapped when the hydrocarbon adduct is intercalated between the base pairs flanking a preexisting top1 cleavage site, or between the base pairs immediately downstream (3' relative to the scissile strand) from this site. We propose a model with the +1 base rotated out of the duplex, and in which the intercalated adduct prevents religation of the corresponding nucleotide at the 5' end of the cleaved DNA. These results suggest mechanisms whereby intercalating agents interfere with the normal function of human top1.
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Affiliation(s)
- Y Pommier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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369
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Hammonds TR, Foster SR, Maxwell A. Increased sensitivity to quinolone antibacterials can be engineered in human topoisomerase IIalpha by selective mutagenesis. J Mol Biol 2000; 300:481-91. [PMID: 10884345 DOI: 10.1006/jmbi.2000.3892] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A potential region of drug-DNA interaction in the A subunit of DNA gyrase has previously been identified from crystallographic studies. The local amino acid sequence has been compared with similar regions in yeast topoisomerase II and human topoisomerase IIalpha. Three non- conserved, potentially solvent-accessible residues at positions 762, 763 and 766 in human topoisomerase IIalpha lie between well-conserved regions. The corresponding residues in GyrA (83, 84 and 87) have a high frequency of mutation in quinolone-resistant bacteria. Mutations in human topoisomerase IIalpha have been generated in an attempt to engineer ciprofloxacin sensitivity into this enzyme: M762S, S763A and M766D (each mutated to the identical amino acid present in gyrase), along with an M762S/S763A double mutant and a triple mutant. These enzymes were introduced into a temperature-sensitive yeast strain, deficient in topoisomerase II, for in vivo studies, and were overproduced for in vitro studies. The M766D mutation renders the enzyme incapable of supporting the temperature-sensitive strain at a non-permissive temperature. However, both M766D and the triple mutant enzymes can be overproduced and are fully active in vitro. The double mutant was impaired in its ability to cleave DNA and had reduced catalytic activity. The triple mutation confers a three-fold increase in sensitivity to ciprofloxacin in vitro and similar sensitivities to a range of other quinolones. The activity of the quinolone CP-115,953, a bacterial and eukaryotic topoisomerase II poison, was unaffected by any of these mutations. Mutations in this region were found to increase the sensitivity of the enzyme to the DNA intercalating anti-tumour agents m-AMSA and ellipticine, but confer resistance to the non-intercalating agents etoposide, teniposide and merbarone, an effect that was maximal in the triple mutant. We have therefore shown the importance of this region in determining the sensitivity of topoisomerase II to drugs and have engineered increased sensitivity to quinolones.
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Affiliation(s)
- T R Hammonds
- Department of Biochemistry, University of Leicester, Leicester, LE1 7RH, UK.
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370
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Veilleux S, Caron N, Boissonneault G. Comparative study of the coupling between topoisomerase I activity and high-mobility group proteins in E. coli and mammalian cells. DNA Cell Biol 2000; 19:421-9. [PMID: 10945232 DOI: 10.1089/10445490050085915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
It is now well established that the HMG box DNA-binding motif can alter the topology of double-stranded DNA in several ways. Using the spermatid-specific tsHMG as a model protein of the HMG-1/-2 family, we have demonstrated that its expression in E. coli produces an increase in plasmid supercoiling density that is likely a consequence of its ability to constrain free supercoils in vivo. As demonstrated in vitro, stabilization of free DNA supercoils by tsHMG prevents topoisomerase I from gaining access to the template and could represent a mechanism for the apparent inhibition of topoisomerase I in bacteria. A similar modulation of eukaryotic topoisomerase I activity was not detected after expression of the tsHMG in mammalian cells. This differential response is discussed in terms of the marked difference in DNA packaging and accessibility of free supercoils in prokaryotic vs. eukaryotic cells.
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Affiliation(s)
- S Veilleux
- Département de Biochimie, Faculté de Médicine, Université de Sherbrooke, Québec, Canada
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371
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Abstract
Protozoan parasites are responsible for a wide range of debilitating and fatal diseases that are proving notoriously difficult to treat. Many of the standard chemotherapies in use today are expensive, have toxic side effects and, in some cases have marginal efficacy because of the emergence of drug-resistant parasites. In the search for more effective treatments, protozoan topoisomerases are now being considered as potential drug targets, building on the clinical success of anticancer and antibacterial agents that target human and bacterial topoisomerases. In this review, Sandra Cheesman explores progress in this relatively new but potentially important field of research.
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Affiliation(s)
- S J Cheesman
- Institute of Cell and Molecular Biology, the University of Edinburgh, Darwin Building, King's Buildings, Mayfield Road, Edinburgh, UK EH9 3JR.
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372
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Scheller J, Schürer A, Rudolph C, Hettwer S, Kramer W. MPH1, a yeast gene encoding a DEAH protein, plays a role in protection of the genome from spontaneous and chemically induced damage. Genetics 2000; 155:1069-81. [PMID: 10880470 PMCID: PMC1461162 DOI: 10.1093/genetics/155.3.1069] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have characterized the MPH1 gene from Saccharomyces cerevisiae. mph1 mutants display a spontaneous mutator phenotype. Homologs were found in archaea and in the EST libraries of Drosophila, mouse, and man. Mph1 carries the signature motifs of the DEAH family of helicases. Selected motifs were shown to be necessary for MPH1 function by introducing missense mutations. Possible indirect effects on translation and splicing were excluded by demonstrating nuclear localization of the protein and splicing proficiency of the mutant. A mutation spectrum did not show any conspicuous deviations from wild type except for an underrepresentation of frameshift mutations. The mutator phenotype was dependent on REV3 and RAD6. The mutant was sensitive to MMS, EMS, 4-NQO, and camptothecin, but not to UV light and X rays. Epistasis analyses were carried out with representative mutants from various repair pathways (msh6, mag1, apn1, rad14, rad52, rad6, mms2, and rev3). No epistatic interactions were found, either for the spontaneous mutator phenotype or for MMS, EMS, and 4-NQO sensitivity. mph1 slightly increased the UV sensitivity of mms2, rad6, and rad14 mutants, but no effect on X-ray sensitivity was observed. These data suggest that MPH1 is not part of a hitherto known repair pathway. Possible functions are discussed.
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Affiliation(s)
- J Scheller
- Abteilung Molekulare Genetik und Präparative Molekularbiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
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373
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Rangarajan M, Kim JS, Jin S, Sim SP, Liu A, Pilch DS, Liu LF, LaVoie EJ. 2"-Substituted 5-phenylterbenzimidazoles as topoisomerase I poisons. Bioorg Med Chem 2000; 8:1371-82. [PMID: 10896114 DOI: 10.1016/s0968-0896(00)00054-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
5-Phenylterbenzimidazole (1) is active as a topoisomerase I poison (topo I) and is cytotoxic to human tumor cells. No cross-resistance was observed for 1 when it was evaluated against the camptothecin-resistant cell line, CPT-K5. Derivatives of 1 substituted at the 2"-position, however, did exhibit cross-resistance to this cell line. The basis for the resistance of this cell line towards CPT is that it possesses a mutant form of topo I. These results suggest that substituents at the 2"-position may be in proximity to the wild-type enzyme. Therefore, we hypothesized that terbenzimidazoles with 2"-substituents could be capable of interacting with the enzyme and thereby influence activity within this class of topo I poisons. 5-Phenylterbenzimidazoles with a hydroxy, hydroxymethyl, mercapto, amino, N-benzoylaminomethyl, chloro, and trifluoromethyl group at the 2"-position were synthesized. In addition, several 2"-ethyl-5-phenylterbenzimidazoles were prepared containing either a methoxy, hydroxy, amino, or N-acetylamino group at the 2-position of the ethyl side-chain. These 2"-substituted 5-phenylterbenzimidazoles were evaluated as topo I poisons and for cytotoxic activity. The presence of a strong electron-withdrawing group at the 2"-position, such as a chloro or trifluoromethyl group, did enhance both topo I poisoning activity and cytotoxicity. Studies on the relative DNA binding affinity of 1 to its 2"-amino and 2"-trifluoromethyl derivatives did exhibit a correlation with their relative differences in biological activity.
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Affiliation(s)
- M Rangarajan
- Department of Pharmaceutical Chemistry, Rutgers, The State University of New Jersey, Piscataway 08854, USA
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374
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Strumberg D, Pilon AA, Smith M, Hickey R, Malkas L, Pommier Y. Conversion of topoisomerase I cleavage complexes on the leading strand of ribosomal DNA into 5'-phosphorylated DNA double-strand breaks by replication runoff. Mol Cell Biol 2000; 20:3977-87. [PMID: 10805740 PMCID: PMC85758 DOI: 10.1128/mcb.20.11.3977-3987.2000] [Citation(s) in RCA: 263] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Topoisomerase I cleavage complexes can be induced by a variety of DNA damages and by the anticancer drug camptothecin. We have developed a ligation-mediated PCR (LM-PCR) assay to analyze replication-mediated DNA double-strand breaks induced by topoisomerase I cleavage complexes in human colon carcinoma HT29 cells at the nucleotide level. We found that conversion of topoisomerase I cleavage complexes into replication-mediated DNA double-strand breaks was only detectable on the leading strand for DNA synthesis, which suggests an asymmetry in the way that topoisomerase I cleavage complexes are metabolized on the two arms of a replication fork. Extension by Taq DNA polymerase was not required for ligation to the LM-PCR primer, indicating that the 3' DNA ends are extended by DNA polymerase in vivo closely to the 5' ends of the topoisomerase I cleavage complexes. These findings suggest that the replication-mediated DNA double-strand breaks generated at topoisomerase I cleavage sites are produced by replication runoff. We also found that the 5' ends of these DNA double-strand breaks are phosphorylated in vivo, which suggests that a DNA 5' kinase activity acts on the double-strand ends generated by replication runoff. The replication-mediated DNA double-strand breaks were rapidly reversible after cessation of the topoisomerase I cleavage complexes, suggesting the existence of efficient repair pathways for removal of topoisomerase I-DNA covalent adducts in ribosomal DNA.
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Affiliation(s)
- D Strumberg
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, USA
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375
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Fertala J, Vance JR, Pourquier P, Pommier Y, Bjornsti MA. Substitutions of Asn-726 in the active site of yeast DNA topoisomerase I define novel mechanisms of stabilizing the covalent enzyme-DNA intermediate. J Biol Chem 2000; 275:15246-53. [PMID: 10809761 DOI: 10.1074/jbc.275.20.15246] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic DNA topoisomerase I (Top1p) catalyzes changes in DNA topology and is the cellular target of camptothecin. Recent reports of enzyme structure highlight the importance of conserved amino acids N-terminal to the active site tyrosine and the involvement of Asn-726 in mediating Top1p sensitivity to camptothecin. To investigate the contribution of this residue to enzyme catalysis, we evaluated the effect of substituting His, Asp, or Ser for Asn-726 on yeast Top1p. Top1N726S and Top1N726D mutant proteins were resistant to camptothecin, although the Ser mutant was distinguished by a lack of detectable changes in activity. Thus, a basic residue immediately N-terminal to the active site tyrosine is required for camptothecin cytotoxicity. However, replacing Asn-726 with Asp or His interfered with distinct aspects of the catalytic cycle, resulting in cell lethality. In contrast to camptothecin, which inhibits enzyme-catalyzed religation of DNA, the His substituent enhanced the rate of DNA scission, whereas the Asp mutation diminished the enzyme binding of DNA. Yet, these effects on enzyme catalysis were not mutually exclusive as the His mutant was hypersensitive to camptothecin. These results suggest distinct mechanisms of poisoning DNA topoisomerase I may be explored in the development of antitumor agents capable of targeting different aspects of the Top1p catalytic cycle.
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Affiliation(s)
- J Fertala
- Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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376
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Yanase K, Sugimoto Y, Tsukahara S, Oh-Hara T, Andoh T, Tsuruo T. Identification and characterization of a deletion mutant of DNA topoisomerase I mRNA in a camptothecin-resistant subline of human colon carcinoma. Jpn J Cancer Res 2000; 91:551-9. [PMID: 10835501 PMCID: PMC5926386 DOI: 10.1111/j.1349-7006.2000.tb00980.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In previous studies, we established two camptothecin (CPT)-resistant sublines, HT-29 / CPT and St-4 / CPT, from the human colon cancer cell line HT-29 and the human stomach cancer cell line St-4, respectively. Cellular contents of DNA topoisomerase I (topo I) in the resistant cells were eight-fold less than those in the corresponding parental lines. In this study, we have shown expression of two species of the TOP1 mRNA in HT-29 / CPT. The longer mRNA (4.0 kb) is the wild-type TOP1 mRNA, and the shorter mRNA (3.3 kb) proved to have a deletion of 672 bp (nucleotides 58 - 729 or 59 - 730) that caused the in-frame deletion of amino acids 20 - 243 of human topo I. The deleted region is identical to exons 3 - 9 of the TOP1 gene. The expression level of the 3.3-kb mRNA was similar to that of the wild-type mRNA in HT-29 / CPT. St-4 / CPT expressed only the wild-type TOP1 mRNA in lesser amounts than did St-4. Mouse NIH3T3 cells transfected with the wild-type TOP1 cDNA showed higher sensitivity to CPT than the parental cells, whereas those transfected with the deleted TOP1 cDNA showed levels similar to those of the parental cells. Expression of the exogenous TOP1 mRNA was confirmed; however, expression of the truncated topo I was not detected in cells transfected with the deleted TOP1 cDNA. These results suggest that the expression of the deleted TOP1 mRNA led to the low expression of CPT-sensitive topo I in the resistant cells.
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Affiliation(s)
- K Yanase
- Cancer Chemotherapy Center, Japanese Foundation for Cancer Research, 1-37-1 Kami-Ikebukuro, Toshima-ku, Tokyo 170-8455, Japan
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377
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Makhey D, Yu C, Liu A, Liu LF, LaVoie EJ. Substituted benz[a]acridines and benz[c]acridines as mammalian topoisomerase poisons. Bioorg Med Chem 2000; 8:1171-82. [PMID: 10882027 DOI: 10.1016/s0968-0896(00)00048-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Coralyne and several other synthetic benzo[a,g]quinolizium derivatives related to protoberberine alkaloids have exhibited activity as topoisomerase poisons. These compounds are characterized by the presence of a positively charged iminium group, which has been postulated to be associated with their pharmacological properties. The objective of the present study was to devise stable noncharged bioisosteres of these compounds. Several similarly substituted benz[a]acridine and benz[c]acridine derivatives were synthesized and their relative activity as topoisomerase poisons was determined. While the benz[c]acridine derivatives evaluated as part of this study were devoid of topoisomerase poisoning activity, several dihydrobenz[a]acridines were able to enhance DNA cleavage in the presence of topo I. In contrast to certain protoberberine derivatives that did exhibit activity as topo II poisons, none of the benz[a]acridines derivatives enhanced DNA cleavage in the presence of topo II. Among the benz[a]acridines studied, 5,6-dihydro-3,4-methylenedioxy-9,10-dimethoxybenz[a]acridine, 13e, was the most potent topo I poison, with comparable potency to coralyne. These data suggest that heterocyclic compounds structurally related to coralyne can exhibit potent topo I poisoning activity despite the absence of an iminium cation within their structure. In comparison to coralyne or other protoberberine derivatives, these benz[a]acridine derivatives possess distinctly different physicochemical properties and represent a novel series of topo I poisons.
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Affiliation(s)
- D Makhey
- Department of Pharmaceutical Chemistry, Rutgers, The State University of New Jersey, Piscataway 08854-8020, USA
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378
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Goossens JF, Hénichart JP, Dassonneville L, Facompré M, Bailly C. Relation between intracellular acidification and camptothecin-induced apoptosis in leukemia cells. Eur J Pharm Sci 2000; 10:125-31. [PMID: 10727878 DOI: 10.1016/s0928-0987(99)00091-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Leukemia cells (HL-60 and P388) treated with the topoisomerase I inhibitor camptothecin (CPT) undergo rapid apoptosis as judged from internucleosomal degradation of genomic DNA, morphological changes and flow cytometry analysis. The intracellular free calcium concentration is not affected by the treatment with a high dose of CPT. In contrast, fluorescence measurements of cells loaded with the pH indicator BCECF-AM indicate that the intracellular pH decreases significantly. Incubation of the leukemia cells with a high drug concentration for 5 h or with lower drug concentrations for 15 h results in a pronounced intracellular acidification. Measurements with the whole cell population show a decrease of 0.3-0.4 pH units. The extent of the acidic shift is proportional to the drug concentration and the period of incubation. No such effects were observed with P388CPT5 cells resistant to CPT. The results support the hypothesis that apoptosis induced in leukemia cells by CPT is associated with decreased intracellular pH. Modification of intracellular pH by topoisomerase inhibitors is viewed as an essential event responsible for the induction and/or propagation of apoptosis. The role of CPT-induced cellular acidification in the mechanism of action of the drug is discussed.
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Affiliation(s)
- J F Goossens
- Laboratoire de Chimie Analytique, Faculté de Pharmacie, B.P. 83, 59006, Lille, France
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379
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Arimondo PB, Moreau P, Boutorine A, Bailly C, Prudhomme M, Sun JS, Garestier T, Hélène C. Recognition and cleavage of DNA by rebeccamycin- or benzopyridoquinoxaline conjugated of triple helix-forming oligonucleotides. Bioorg Med Chem 2000; 8:777-84. [PMID: 10819166 DOI: 10.1016/s0968-0896(00)00012-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Indolocarbazole and benzopyridoquinoxaline derivatives have been shown to have anti-tumor activity and to stimulate DNA topoisomerase I-mediated cleavage. Two indolocarbazole compounds (R-6 and R-95) and one benzopyridoquinoxaline derivative (BPQ(1256)) were covalently attached to the 3'-end of a 16mer triple helix-forming oligonucleotide (TFO). These conjugates bind to DNA with a higher affinity than the unsubstituted oligonucleotides. Furthermore, they induce topoisomerase I-mediated and triplex-directed DNA cleavage in a sequence-specific manner.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, UMR 8646 CNRS-Muséum National d'Histoire Naturelle, INSERM U201, Paris, France
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380
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Fortune JM, Osheroff N. Topoisomerase II as a target for anticancer drugs: when enzymes stop being nice. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2000; 64:221-53. [PMID: 10697411 DOI: 10.1016/s0079-6603(00)64006-0] [Citation(s) in RCA: 259] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Topoisomerase II is an essential enzyme that plays a role in virtually every cellular DNA process. This enzyme interconverts different topological forms of DNA by passing one nucleic acid segment through a transient double-stranded break generated in a second segment. By virtue of its double-stranded DNA passage reaction, topoisomerase II is able to regulate DNA over- and underwinding, and can resolve knots and tangles in the genetic material. Beyond the critical physiological functions of the eukaryotic enzyme, topoisomerase II is the target for some of the most successful anticancer drugs used to treat human malignancies. These agents are referred to as topoisomerase II poisons, because they transform the enzyme into a potent cellular toxin. Topoisomerase II poisons act by increasing the concentration of covalent enzyme-cleaved DNA complexes that normally are fleeting intermediates in the catalytic cycle of topoisomerase II. As a result of their action, these drugs generate high levels of enzyme-mediated breaks in the genetic material of treated cells and ultimately trigger cell death pathways. Topoisomerase II is also the target for a second category of drugs referred to as catalytic inhibitors. Compounds in this category prevent topoisomerase II from carrying out its required physiological functions. Drugs from both categories vary widely in their mechanisms of actions. This review focuses on topoisomerase II function and how drugs alter the catalytic cycle of this important enzyme.
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Affiliation(s)
- J M Fortune
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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381
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Gornet JM, Azoulay D, Lévi F, Yovine A, Misset JL, Goldwasser F. Dramatic tumor response of bulky liver metastases following treatment with CPT-11 and a chronomodulated 4-day infusion of 5-fluorouracil, folinic acid and oxaliplatin every 2 weeks in a colorectal cancer patient. Anticancer Drugs 2000; 11:263-8. [PMID: 10898541 DOI: 10.1097/00001813-200004000-00006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Three active antitumor agents, i.e. 5-fluorouracil (5-FU), oxaliplatin and CPT-11, are available for the treatment of advanced colorectal cancer (CRC) patients and have been successfully combined in two-drug regimens. Hence, CRC has become a chemosensitive disease, but the optimal combination of these agents in first-line treatment remains to be determined. We report the first case of the combination of CPT-11 with oxaliplatin, 5-FU and folinic acid (FA) as first-line chemotherapy for a patient with a pre-occlusive sigmoid adenocarcinoma and synchronous bulky liver metastases. CPT-11 was given at 125 mg/m2, prior to the start of a chronomodulated 4-day infusion of oxaliplatin 25 mg/m2/day, 5-FU 800 mg/m2/day and FA 300 mg/m2/day repeated every 2 weeks. The doses could be escalated to 150 mg/m2 for CPT-11 and 900 mg/m2/day for 5-FU. After six cycles of chemotherapy 70% reduction in tumor size was documented in the liver. The primary tumor was no longer detectable by barium enema. The toxicity included three episodes of grade 4 neutropenic fever, and two episodes of severe diarrhea and vomiting with dehydration. A cumulative grade 2 neurosensory toxicity was observed after six cycles. Following surgery of the primary tumor, because of the major hepatic tumor response and of the absence of extra-hepatic metastases, the patient might be registered for a liver transplantation program. This first report of combining the three active agents in CRC every 2 weeks led to a high dose intensity of each agent and was associated with a dramatic tumor response of a very advanced disease in a patient with already altered performance status. The antitumor activity in this patient suggests that a three-drug intensified regimen might be feasible and active. A prospective study appears warranted to further examine the efficacy and toxicity of this therapeutic approach, and to determine whether it may increase the fraction of advanced CRC patients becoming resectable. This aggressive chemotherapy program may contribute to a re-examination of the usefulness of liver transplantation in patients with metastatic CRC confined to the liver.
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Affiliation(s)
- J M Gornet
- Service de Cancérologie, Hôpital Paul Brousse, Villejuif, France
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382
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Perrin D, van Hille B, Barret JM, Kruczynski A, Etiévant C, Imbert T, Hill BT. F 11782, a novel epipodophylloid non-intercalating dual catalytic inhibitor of topoisomerases I and II with an original mechanism of action. Biochem Pharmacol 2000; 59:807-19. [PMID: 10718339 DOI: 10.1016/s0006-2952(99)00382-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
F 11782, a novel epipodophylloid, proved a potent inhibitor of the catalytic activities of both topoisomerases I and II. Unlike classical inhibitors such as camptothecin or etoposide, F 11782 did not stabilise cleavable complexes induced by either topoisomerases I or II nor did it preferentially inhibit the religation step of the catalytic cycle of either enzyme. F 11782 neither intercalated DNA nor bound in its minor groove, and showed only weak inhibition of the ATPase activity associated with topoisomerase II. F 11782 appeared to act by inhibiting the binding of topoisomerases I and II to DNA in a manner dependent both on drug and enzyme concentrations, via a mechanism not previously described or shared by other known topoisomerase 'poisons' or inhibitors. In contrast, F 11782 had only a weak effect or none at all on various other DNA-interacting enzymes. In conclusion, F 11782, as a non-intercalating, specific catalytic inhibitor of both topoisomerases I and II with an original mechanism of action, may be considered to represent the first of a new class of topoisomerase-interacting agents.
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Affiliation(s)
- D Perrin
- Division of Experimental Cancerology I, Centre de Recherche Pierre Fabre, Castres, France.
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383
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Ren J, Bailly C, Chaires JB. NB-506, an indolocarbazole topoisomerase I inhibitor, binds preferentially to triplex DNA. FEBS Lett 2000; 470:355-9. [PMID: 10745096 DOI: 10.1016/s0014-5793(00)01335-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A novel competition dialysis method was used to study the structural selectivity of the nucleic acid binding of NB-506, a promising indolocarbazole anticancer agent. A pronounced preference for NB-506 binding to the DNA triplex poly [dA]:(poly[dT])(2) was observed among potential binding to 12 different nucleic acid structures and sequences. Structures included in the assay ranged from single-stranded DNA, through a variety of right-handed DNA duplexes, to multistranded triplex and tetraplex forms. RNA and left-handed Z DNA were also included in the assay. The preferential binding to triplex was confirmed by UV melting experiments. The novel and unexpected structural selectivity shown by NB-506 may arise from a complementary shape between its extended aromatic ring system and the planar triplex stack.
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Affiliation(s)
- J Ren
- Department of Biochemistry, University of Mississippi Medical Center, 2500 N. State St., Jackson, MS 39216-4505, USA
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384
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Dudouit F, Goossens JF, Houssin R, Hénichart JP, Colson P, Houssier C, Gelus N, Bailly C. Synthesis, DNA binding, topoisomerases inhibition and cytotoxic properties of 4-arylcarboxamidopyrrolo-2-carboxyanilides. Bioorg Med Chem Lett 2000; 10:553-7. [PMID: 10741552 DOI: 10.1016/s0960-894x(00)00028-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Three 4-arylcarboxamidopyrrolo-2-carboxyanilides bearing different substituents on the pyrrole nitrogen were synthesized and evaluated for their capacities to bind to specific sequences within the minor groove of DNA and to inhibit human topoisomerases I and II in vitro. The cytotoxicity of the drugs correlates with their DNA binding affinities. The two drugs bearing a N-methyl or N-benzyl pyrrole stabilize topoisomerase I-DNA complexes.
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Affiliation(s)
- F Dudouit
- Institut de Chimie Pharmaceutique Albert Lespragnol, Université de Lille 2, France
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385
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Wakabayashi I, Mayer B, Groschner K. Inhibitory effects of aclarubicin on nitric oxide production in aortic smooth muscle cells and macrophages. Biochem Pharmacol 2000; 59:719-26. [PMID: 10677589 DOI: 10.1016/s0006-2952(99)00358-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of aclaruhicin (ACR), an anthracycline antibiotic, on inducible nitric oxide (NO) synthesis was investigated in rat aortic smooth muscle cells (RASMCs) and RAW macrophages. ACR at concentrations as low as 0.1 microM significantly inhibited NO production induced by interleukin-1beta in RASMCs. About 5- to 10-fold higher concentrations of ACR were required for inhibition of interferon-gamma and lipopolipopolysaccharide-induced NO production in RAW cells. When ACR was subsequently administered to inducible NO synthase (iNOS) induction, the NO production was barely suppressed in RASMCs. Moreover, ACR (up to 10 microM) lacked direct inhibitory effects on iNOS activity in homogenates of these cells. ACR (0.1 microM) inhibited the expression of iNOS protein and mRNA in RASMCs without concomitant cytotoxic effects. ACR (>0.5 microM)-induced inhibition of NO production in RAW cells was associated with substantial cytotoxic effects as shown by measurement of lactate dehydrogenase release. These results suggest that ACR is a potent inhibitor of iNOS induction in vascular smooth muscle, but inhibits iNOS induction in macrophage only at high cytotoxic
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MESH Headings
- Aclarubicin/pharmacology
- Animals
- Antibiotics, Antineoplastic/pharmacology
- Aorta/cytology
- Cell Division/drug effects
- Cells, Cultured
- Dichlororibofuranosylbenzimidazole/pharmacology
- Enzyme Inhibitors/pharmacology
- In Vitro Techniques
- Macrophages/drug effects
- Macrophages/metabolism
- Male
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Nitric Oxide/metabolism
- Nitric Oxide Synthase/biosynthesis
- Nitric Oxide Synthase/metabolism
- Nitric Oxide Synthase Type II
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
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Affiliation(s)
- I Wakabayashi
- Department of Hygiene and Preventive Medicine, School of Medicine, Yamagata University, Yamagata, Japan.
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386
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Lavrukhin OV, Fortune JM, Wood TG, Burbank DE, Van Etten JL, Osheroff N, Lloyd RS. Topoisomerase II from Chlorella virus PBCV-1. Characterization of the smallest known type II topoisomerase. J Biol Chem 2000; 275:6915-21. [PMID: 10702252 DOI: 10.1074/jbc.275.10.6915] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type II topoisomerases, a family of enzymes that govern topological DNA interconversions, are essential to many cellular processes in eukaryotic organisms. Because no data are available about the functions of these enzymes in the replication of viruses that infect eukaryotic hosts, this led us to express and characterize the first topoisomerase II encoded by one of such viruses. Paramecium bursaria chlorella virus 1 (PBCV-1) infects certain chlorella-like green algae and encodes a 120-kDa protein with a similarity to type II topoisomerases. This protein was expressed in Saccharomyces cerevisiae and was highly active in relaxation of both negatively and positively supercoiled plasmid DNA, catenation of plasmid DNA, and decatenation of kinetoplast DNA networks. Its optimal activity was determined, and the omission of Mg(2+) or its replacement with other divalent cations abolished DNA relaxation. All activities of the recombinant enzyme were ATP dependent. Increasing salt concentrations shifted DNA relaxation from a normally processive mechanism to a distributive mode. Thus, even though the PBCV-1 enzyme is considerably smaller than other eukaryotic topoisomerase II enzymes (whose molecular masses are typically 160-180 kDa), it displays all the catalytic properties expected for a type II topoisomerase.
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Affiliation(s)
- O V Lavrukhin
- Department of Human Biological Chemistry and Genetics and Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, Texas 77555-1071, USA
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387
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Pommier Y, Kohlhagen G, Pourquier P, Sayer JM, Kroth H, Jerina DM. Benzo[a]pyrene diol epoxide adducts in DNA are potent suppressors of a normal topoisomerase I cleavage site and powerful inducers of other topoisomerase I cleavages. Proc Natl Acad Sci U S A 2000; 97:2040-5. [PMID: 10688881 PMCID: PMC15750 DOI: 10.1073/pnas.040397497] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The catalytic intermediates of DNA topoisomerase I (top1) are cleavage complexes that can relax DNA supercoiling (intramolecular reaction) or mediate recombinations (intermolecular religation). We report here that DNA adducts formed from benzo[a]pyrene bay-region diol epoxides can markedly affect top1 activity. Four oligonucleotide 22-mers of the same sequence were synthesized, each of which contained a stereoisomerically unique benzo[a]pyrene 7, 8-diol 9,10-epoxide adduct at the 2-amino group of a central 2'-deoxyguanosine residue. These four adducts correspond to either cis or trans opening at C-10 of the (+)-(7R, 8S, 9S, 10R)- or (-)-(7S, 8R, 9R, 10S)-7,8-diol 9,10-epoxides. Their solution conformations in duplex DNA (intercalated and minor-groove bound for the cis and trans opened adducts respectively) can be deduced from previous NMR studies. All four adducts completely suppress top1 cleavage activity at the alkylation site and induce the formation of new top1cleavage complexes on both strands of the DNA 3-6 bases away from the alkylation site. The trans opened adduct from the highly carcinogenic (+)-diol epoxide is the most active in inducing top1 cleavage independently of camptothecin, demonstrating that minor groove alkylation can efficiently poison top1. We also found that this isomer of the diol epoxide induces the formation of top1-DNA complexes in mammalian cells, which suggests a possible relationship between induction of top1 cleavage complexes and carcinogenic activity of benzo[a]pyrene diol epoxides.
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Affiliation(s)
- Y Pommier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, NIH, Bethesda, MD 20892, USA
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388
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Pourquier P, Takebayashi Y, Urasaki Y, Gioffre C, Kohlhagen G, Pommier Y. Induction of topoisomerase I cleavage complexes by 1-beta -D-arabinofuranosylcytosine (ara-C) in vitro and in ara-C-treated cells. Proc Natl Acad Sci U S A 2000; 97:1885-90. [PMID: 10677551 PMCID: PMC26531 DOI: 10.1073/pnas.97.4.1885] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/1999] [Indexed: 11/18/2022] Open
Abstract
1-beta-d-Arabinofuranosylcytosine (Ara-C) is a nucleoside analog commonly used in the treatment of leukemias. Ara-C inhibits DNA polymerases and can be incorporated into DNA. Its mechanism of cytotoxicity is not fully understood. Using oligonucleotides and purified human topoisomerase I (top1), we found a 4- to 6-fold enhancement of top1 cleavage complexes when ara-C was incorporated at the +1 position (immediately 3') relative to a unique top1 cleavage site. This enhancement was primarily due to a reversible inhibition of top1-mediated DNA religation. Because ara-C incorporation is known to alter base stacking and sugar puckering at the misincorporation site and at the neighboring base pairs, the observed inhibition of religation at the ara-C site suggests the importance of the alignment of the 5'-hydroxyl end for religation with the phosphate group of the top1 phosphotyrosine bond. This study also demonstrates that ara-C treatment and DNA incorporation trap top1 cleavage complexes in human leukemia cells. Finally, we report that camptothecin-resistant mouse P388/CPT45 cells with no detectable top1 are crossresistant to ara-C, which suggests that top1 poisoning is a potential mechanism for ara-C cytotoxicity.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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389
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Fleury F, Sukhanova A, Ianoul A, Devy J, Kudelina I, Duval O, Alix AJ, Jardillier JC, Nabiev I. Molecular determinants of site-specific inhibition of human DNA topoisomerase I by fagaronine and ethoxidine. Relation to DNA binding. J Biol Chem 2000; 275:3501-9. [PMID: 10652345 DOI: 10.1074/jbc.275.5.3501] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA topoisomerase (top) I inhibition activity of the natural alkaloid fagaronine (NSC157995) and its new synthetic derivative ethoxidine (12-ethoxy-benzo[c]phenanthridine) has been correlated with their molecular interactions and sequence specificity within the DNA complexes. Flow linear dichroism shows that ethoxidine exhibits the same inhibition of DNA relaxation as fagaronine at the 10-fold lower concentration. The patterns of DNA cleavage by top I show linear enhancement of CPT-dependent sites at the 0.016-50 microM concentrations of fagaronine, whereas ethoxidine suppress both top I-specific and CPT-dependent sites. Suppression of top I-mediated cleavage by ethoxidine is found to be specific for the sites, including strand cut between A and T. Fagaronine and ethoxidine are DNA major groove intercalators. Ethoxidine intercalates DNA in A-T sequences and its 12-ethoxy-moiety (absent in fagaronine) extends into the DNA minor groove. These findings may explain specificity of suppression by ethoxidine of the strong top I cleavage sites with the A(+1), T(-1) immediately adjacent to the strand cut. Fagaronine does not show any sequence specificity of DNA intercalation, but its highly electronegative oxygen of hydroxy group (absent in ethoxidine) is shown to be an acceptor of the hydrogen bond with the NH(2) group of G base of DNA. Ability of fagaronine to stabilize top I-mediated ternary complex is proposed to be determined by interaction of its hydroxy group with the guanine at position (+1) of the DNA cleavage site and of quaternary nitrogen interaction with top I. The model proposed provides a guidance for screening new top I-targeted drugs in terms of identification of molecular determinants responsible for their top I inhibition effects.
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Affiliation(s)
- F Fleury
- EA2063, Institut Fédératif de Recherche no. 53 "Biomolécules," UFR de Pharmacie, Université de Reims Champagne-Ardenne, 51100 Reims, France
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390
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Gupta D, Bronstein IB, Holden JA. Expression of DNA topoisomerase I in neoplasms of the kidney: correlation with histological grade, proliferation, and patient survival. Hum Pathol 2000; 31:214-9. [PMID: 10685636 DOI: 10.1016/s0046-8177(00)80222-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Renal cell carcinoma is an inherently chemotherapeutically resistant neoplasm. Because of this, new drugs targeting this tumor are needed. One class of new anticancer drug targets the enzyme DNA topoisomerase I. Laboratory data indicate that cells sensitive to topo I targeting drugs contain high topo I levels. To determine whether some renal cell carcinomas contain elevated topo I and might therefore be targets of topo I active antitumor agents, we used a new immunohistochemical stain for topo I to determine the expression of the enzyme in 51 tumors of the kidney. Increased topo I expression was found in 4 of 11 (36%) grade 3 renal cell carcinomas and in 8 of 8 (100%) grade 4 renal cell carcinomas. Normal topo I expression was observed in all adenomas, oncocytomas, and grade 1 and grade 2 renal cell carcinomas. Because topo I targeted anticancer drugs are S-phase specific, topo II-alpha and MIB-1 proliferation indices also were performed. Topo II-alpha correlates well with MIB-1 (correlation coefficient = 0.96). Of the 12 tumors with elevated topo I, only 3 had topo II-alpha proliferation indices greater than 40, indicating a tumor with elevated topo I expression and a large growth fraction. We hypothesize that these tumors might be susceptible to topo I anticancer drug therapy. In addition, we found that the average topo II-alpha proliferation index of tumors from patients who died of disease was 27.4 +/- 19.8, which was statistically different from the average topo II-alpha index of 5.8 +/- 6.5 observed in tumors from patients who remained alive during our follow-up.
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Affiliation(s)
- D Gupta
- Department of Pathology, University of Utah Health Sciences Center, Salt Lake City 84132, USA
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391
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Anderson VE, Zaniewski RP, Kaczmarek FS, Gootz TD, Osheroff N. Quinolones inhibit DNA religation mediated by Staphylococcus aureus topoisomerase IV. Changes in drug mechanism across evolutionary boundaries. J Biol Chem 1999; 274:35927-32. [PMID: 10585479 DOI: 10.1074/jbc.274.50.35927] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Quinolones are the most active oral antibacterials in clinical use and act by increasing DNA cleavage mediated by prokaryotic type II topoisomerases. Although topoisomerase IV appears to be the primary cytotoxic target for most quinolones in Gram-positive bacteria, interactions between the enzyme and these drugs are poorly understood. Therefore, the effects of ciprofloxacin on the DNA cleavage and religation reactions of Staphylococcus aureus topoisomerase IV were characterized. Ciprofloxacin doubled DNA scission at 150 nM drug and increased cleavage approximately 9-fold at 5 microM. Furthermore, it dramatically inhibited rates of DNA religation mediated by S. aureus topoisomerase IV. This inhibition of religation is in marked contrast to the effects of antineoplastic quinolones on eukaryotic topoisomerase II, and suggests that the mechanistic basis for quinolone action against type II topoisomerases has not been maintained across evolutionary boundaries. The apparent change in quinolone mechanism was not caused by an overt difference in the drug interaction domain on topoisomerase IV. Therefore, we propose that the mechanistic basis for quinolone action is regulated by subtle changes in drug orientation within the enzyme.drug.DNA ternary complex rather than gross differences in the site of drug binding.
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Affiliation(s)
- V E Anderson
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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392
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Abstract
DNA topoisomerases catalyze changes in the topology of DNA. Recently, other functions have also been reported for these enzymes. For example, topoisomerase I participates in transcription by RNA polymerases I, II, and III, and also has a kinase activity. Topoisomerase I binds directly to at least two helicases, nucleolin and SV40 T antigen, and mechanistic studies show that T antigen alters the function of topoisomerase I. Additional protein and nucleotide interactions for both topoisomerases I and II suggest that each protein is multifunctional. It may be that the multifunctional nature of these enzymes is the basis for the antitumor activity seen with inhibitors of these enzymes. Clinical trials with combinations of CPT-11 and 5-fluorouracil for the treatment of colon cancer, and preclinical studies with CPT-11 and vincristine are particularly encouraging. Protracted schedules of administration of topoisomerase inhibitors will likely have greater antitumor effect than more concentrated, higher dose exposures, but a systematic determination of optimal schedules of administration is needed.
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Affiliation(s)
- S M Guichard
- Laboratoire de Pharmacologie, Institut Claudius Regaud, Toulouse, France
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393
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Pouliot JJ, Yao KC, Robertson CA, Nash HA. Yeast gene for a Tyr-DNA phosphodiesterase that repairs topoisomerase I complexes. Science 1999; 286:552-5. [PMID: 10521354 DOI: 10.1126/science.286.5439.552] [Citation(s) in RCA: 308] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Covalent intermediates between topoisomerase I and DNA can become dead-end complexes that lead to cell death. Here, the isolation of the gene for an enzyme that can hydrolyze the bond between this protein and DNA is described. Enzyme-defective mutants of yeast are hypersensitive to treatments that increase the amount of covalent complexes, indicative of enzyme involvement in repair. The gene is conserved in eukaryotes and identifies a family of enzymes that has not been previously recognized. The presence of this gene in humans may have implications for the effectiveness of topoisomerase I poisons, such as the camptothecins, in chemotherapy.
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Affiliation(s)
- J J Pouliot
- Laboratory of Molecular Biology, National Institute of Mental Health, Building 36, Room 1B08, Bethesda, MD 20892-4034, USA
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394
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Pommier Y, Pourquier P, Urasaki Y, Wu J, Laco GS. Topoisomerase I inhibitors: selectivity and cellular resistance. Drug Resist Updat 1999; 2:307-318. [PMID: 11504505 DOI: 10.1054/drup.1999.0102] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Topoisomerase I (top1) inhibitors (camptothecins and other structurally diverse compounds) are effective and promising anticancer agents. Determinants of selectivity toward cancer cells and resistance are multifactorial. These factors can be separated in three groups. The first is related to alterations in drug distribution and metabolism. The second group includes both quantitative and qualitative (mutations) differences in top I. The third group includes resistance and sensitivity factors downstream from the cleavage complexes. They include DNA repair, cell cycle checkpoints and apoptosis, and are probably key to the relative selectivity of camptothecins toward cancer cells and to clinical resistance. Copyright 1999 Harcourt Publishers Ltd.
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Affiliation(s)
- Yves Pommier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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395
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Reid RJ, Fiorani P, Sugawara M, Bjornsti MA. CDC45 and DPB11 are required for processive DNA replication and resistance to DNA topoisomerase I-mediated DNA damage. Proc Natl Acad Sci U S A 1999; 96:11440-5. [PMID: 10500195 PMCID: PMC18052 DOI: 10.1073/pnas.96.20.11440] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The antitumor agent camptothecin targets DNA topoisomerase I by reversibly stabilizing a covalent enzyme-DNA intermediate. The subsequent collision of DNA replication forks with these drug-enzyme-DNA complexes produces the cytotoxic DNA lesions that signal cell cycle arrest and ultimately lead to cell death. Despite intense investigation, the character of the lesions produced and the repair processes that resolve the damage remain poorly defined. A yeast genetic screen was implemented to isolate conditional mutants with enhanced sensitivity to DNA topoisomerase I-mediated DNA damage. Cells exhibiting temperature-sensitive growth in the presence of the DNA topoisomerase I mutant, Top1T722Ap, were selected. Substitution of Ala for Thr722 increases the stability of the covalent Top1T722Ap-DNA intermediate, mimicking the cytotoxic action of camptothecin. Two mutants isolated, cdc45-10 and dpb11-10, exhibited specific defects in DNA replication and a synthetic lethal phenotype in the absence of DNA damaging agents. The accumulation of Okazaki fragments under nonpermissive conditions suggests a common function in promoting processive DNA replication through polymerase switching. These results provide a mechanistic basis for understanding the cellular processes involved in the resolution of DNA damage induced by camptothecin and DNA topoisomerase I.
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Affiliation(s)
- R J Reid
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
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396
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Takebayashi Y, Pourquier P, Yoshida A, Kohlhagen G, Pommier Y. Poisoning of human DNA topoisomerase I by ecteinascidin 743, an anticancer drug that selectively alkylates DNA in the minor groove. Proc Natl Acad Sci U S A 1999; 96:7196-201. [PMID: 10377391 PMCID: PMC22050 DOI: 10.1073/pnas.96.13.7196] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ecteinascidin 743 (Et743, National Service Center 648766) is a potent antitumor agent from the Caribbean tunicate Ecteinascidia turbinata. Although Et743 is presently in clinical trials for human cancers, the mechanisms of antitumor activity of Et743 have not been elucidated. Et743 can alkylate selectively guanine N2 from the DNA minor groove, and this alkylation is reversed by DNA denaturation. Thus, Et743 differs from other DNA alkylating agents presently in the clinic (by both its biochemical activities and its profile of antitumor activity in preclinical models). In this study, we investigated cellular proteins that can bind to DNA alkylated by Et743. By using an oligonucleotide containing high-affinity Et743 binding sites and nuclear extracts from human leukemia CEM cells, we purified a 100-kDa protein as a cellular target of Et743 and identified it as topoisomerase I (top1). Purified top1 was then tested and found to produce cleavage complexes in the presence of Et743, whereas topoisomerase II had no effect. DNA alkylation was essential for the formation of top1-mediated cleavage complexes by Et743, and the distribution of the drug-induced top1 sites was different for Et743 and camptothecin. top1-DNA complexes were also detected in Et743-treated CEM cells by using cesium chloride gradient centrifugation followed by top1 immunoblotting. These data indicate that DNA minor groove alkylation by Et743 induces top1-mediated protein-linked DNA breaks and that top1 is a target for Et743 in vitro and in vivo.
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Affiliation(s)
- Y Takebayashi
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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397
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Pourquier P, Jensen AD, Gong SS, Pommier Y, Rogler CE. Human DNA topoisomerase I-mediated cleavage and recombination of duck hepatitis B virus DNA in vitro. Nucleic Acids Res 1999; 27:1919-25. [PMID: 10101202 PMCID: PMC148402 DOI: 10.1093/nar/27.8.1919] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this study, we report that eukaryotic topoisomerase I (top1) can linearize the open circular DNA of duck hepatitis B virus (DHBV). Using synthetic oligonucleotides mimicking the three-strand flap DR1 region of the DHBV genome, we found that top1 cleaves the DNA plus strand in a suicidal manner, which mimics the linearization of the virion DNA. We also report that top1 can cleave the DNA minus strand at specific sites and can linearize the minus strand via a non-homologous recombination reaction. These results are consistent with the possibility that top1 can act as a DNA endo-nuclease and strand transferase and play a role in the circularization, linearization and possibly integration of viral replication intermediates.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Building 37, Room 5D02, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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398
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Pourquier P, Bjornsti MA, Pommier Y. Induction of topoisomerase I cleavage complexes by the vinyl chloride adduct 1,N6-ethenoadenine. J Biol Chem 1998; 273:27245-9. [PMID: 9765247 DOI: 10.1074/jbc.273.42.27245] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
We used purified mammalian topoisomerases I (top1) and oligonucleotides to study top1-mediated cleavage and religation in the presence of a potent carcinogenic adduct, 1,N6-ethenoadenosine (epsilonA) incorporated immediately downstream of a unique top1 cleavage site. We found tha epsilonA markedly enhanced top1 cleavage complexes when it was incorporated at the +1 position of the top1 cleavage. This enhancement was due to a reduction of the religation step of the top1 reaction. In addition, epsilonA reduced the top1-mediated cleavage and decreased binding of the enzyme to DNA. We also studied the effects of the epsilonA adduct on top1 trapping by camptothecin (CPT), a well known top1 inhibitor. CPT was inactive when epsilonA was present at the +1 position. Alkylation of the top1 cleavage complex by 7-chloromethyl-10,11-methylenedioxycamptothecin (7-ClMe-MDO-CPT) was also blocked by the epsilonA adduct. Altogether, these results demonstrate that the epsilonA carcinogenic adduct can efficiently trap human top1 and mimic CPT effects. Normal hydrogen bonding of the base pairs immediately downstream from the top1 cleavage site is probably essential for efficient DNA religation and binding of camptothecins in the top1 cleavage complex.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, NCI, National Institutes of Health, Bethesda, Maryland 20892-4255, USA
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