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Packeiser EM, Engels L, Nolte I, Goericke-Pesch S, Murua Escobar H. MDR1 Inhibition Reverses Doxorubicin-Resistance in Six Doxorubicin-Resistant Canine Prostate and Bladder Cancer Cell Lines. Int J Mol Sci 2023; 24:ijms24098136. [PMID: 37175843 PMCID: PMC10179448 DOI: 10.3390/ijms24098136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/22/2023] [Accepted: 04/27/2023] [Indexed: 05/15/2023] Open
Abstract
Acquired chemoresistance during chemotherapy, often accompanied by cross- and multi-resistance, limits therapeutic outcomes and leads to recurrence. In order to create in vitro model systems to understand acquired doxorubicin-resistance, we generated doxorubicin-resistant sublines of canine prostate adenocarcinoma and urothelial cell carcinoma cell lines. Chemoresistance to doxorubicin, cross-resistance to carboplatin, and the reversibility of the acquired resistance by the specific MDR1-inhibitor tariquidar were quantified in metabolic assays. Resistance mechanisms were characterized by expression of the efflux transporters MDR1 and RALBP1, as well as the molecular target of doxorubicin, TOP2A, with qPCR and Western blotting. Six out of nine cell lines established stable resistance to 2 µM doxorubicin. Drug efflux via massive MDR1 overexpression was identified as common, driving resistance mechanism in all sublines. MDR1 inhibition with tariquidar extensively reduced or reversed the acquired, and also partly the parental resistance. Three cell lines developed additional, non-MDR1-dependent resistance. RALBP1 was upregulated in one resistant subline at the protein level, while TOP2A expression was not altered. Combination therapies aiming to inhibit MDR1 activity can now be screened for synergistic effects using our resistant sublines. Nevertheless, detailed resistance mechanisms and maintained molecular target expression in the resistant sublines are still to be examined.
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Affiliation(s)
- Eva-Maria Packeiser
- Department of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, Foundation, 30559 Hannover, Germany
- Unit for Reproductive Medicine-Clinic for Small Animals, University of Veterinary Medicine Hannover, Foundation, 30559 Hannover, Germany
| | - Leoni Engels
- Department of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, Foundation, 30559 Hannover, Germany
| | - Ingo Nolte
- Department of Small Animal Medicine and Surgery, University of Veterinary Medicine Hannover, Foundation, 30559 Hannover, Germany
| | - Sandra Goericke-Pesch
- Unit for Reproductive Medicine-Clinic for Small Animals, University of Veterinary Medicine Hannover, Foundation, 30559 Hannover, Germany
| | - Hugo Murua Escobar
- Department of Medicine, Clinic III, Hematology, Oncology and Palliative Medicine, University Medical Center Rostock, 18057 Rostock, Germany
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Levin M, Stark M, Ofran Y, Assaraf YG. Deciphering molecular mechanisms underlying chemoresistance in relapsed AML patients: towards precision medicine overcoming drug resistance. Cancer Cell Int 2021; 21:53. [PMID: 33446189 PMCID: PMC7809753 DOI: 10.1186/s12935-021-01746-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 01/02/2021] [Indexed: 12/13/2022] Open
Abstract
Background Acute myeloid leukemia (AML) remains a devastating disease with a 5-year survival rate of less than 30%. AML treatment has undergone significant changes in recent years, incorporating novel targeted therapies along with improvements in allogeneic bone marrow transplantation techniques. However, the standard of care remains cytarabine and anthracyclines, and the primary hindrance towards curative treatment is the frequent emergence of intrinsic and acquired anticancer drug resistance. In this respect, patients presenting with chemoresistant AML face dismal prognosis even with most advanced therapies. Herein, we aimed to explore the potential implementation of the characterization of chemoresistance mechanisms in individual AML patients towards efficacious personalized medicine. Methods Towards the identification of tailored treatments for individual patients, we herein present the cases of relapsed AML patients, and compare them to patients displaying durable remissions following the same chemotherapeutic induction treatment. We quantified the expression levels of specific genes mediating drug transport and metabolism, nucleotide biosynthesis, and apoptosis, in order to decipher the molecular mechanisms underlying intrinsic and/or acquired chemoresistance modalities in relapsed patients. This was achieved by real-time PCR using patient cDNA, and could be readily implemented in the clinical setting. Results This analysis revealed pre-existing differences in gene expression levels between the relapsed patients and patients with lasting remissions, as well as drug-induced alterations at different relapse stages compared to diagnosis. Each of the relapsed patients displayed unique chemoresistance mechanisms following similar treatment protocols, which could have been missed in a large study aimed at identifying common drug resistance determinants. Conclusions Our findings emphasize the need for standardized evaluation of key drug transport and metabolism genes as an integral component of routine AML management, thereby allowing for the selection of treatments of choice for individual patients. This approach could facilitate the design of efficacious personalized treatment regimens, thereby reducing relapse rates of therapy refractory disease.
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Affiliation(s)
- May Levin
- The Fred Wyszkowski Cancer Research Laboratory, Dept. of Biology, Technion-Israel Institute of Technology, 3200003, Haifa, Israel
| | - Michal Stark
- The Fred Wyszkowski Cancer Research Laboratory, Dept. of Biology, Technion-Israel Institute of Technology, 3200003, Haifa, Israel
| | - Yishai Ofran
- Department of Hematology and Bone Marrow Transplantation, Rambam Health Care Campus, Haifa, Israel.
| | - Yehuda G Assaraf
- The Fred Wyszkowski Cancer Research Laboratory, Dept. of Biology, Technion-Israel Institute of Technology, 3200003, Haifa, Israel.
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Wang Y, Rakela S, Chambers JW, Hua ZC, Muller MT, Nitiss JL, Tse-Dinh YC, Leng F. Kinetic Study of DNA Topoisomerases by Supercoiling-Dependent Fluorescence Quenching. ACS OMEGA 2019; 4:18413-18422. [PMID: 31720544 PMCID: PMC6844113 DOI: 10.1021/acsomega.9b02676] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 10/11/2019] [Indexed: 06/10/2023]
Abstract
DNA topoisomerases are essential enzymes for all living organisms and important targets for anticancer drugs and antibiotics. Although DNA topoisomerases have been studied extensively, steady-state kinetics has not been systematically investigated because of the lack of an appropriate assay. Previously, we demonstrated that newly synthesized, fluorescently labeled plasmids pAB1_FL905 and pAB1_FL924 can be used to study DNA topoisomerase-catalyzed reactions by fluorescence resonance energy transfer (FRET) or supercoiling-dependent fluorescence quenching (SDFQ). With the FRET or SDFQ method, we performed steady-state kinetic studies for six different DNA topoisomerases including two type IA enzymes (Escherichia coli and Mycobacterium smegmatis DNA topoisomerase I), two type IB enzymes (human and variola DNA topoisomerase I), and two type IIA enzymes (E. coli DNA gyrase and human DNA topoisomerase IIα). Our results show that all DNA topoisomerases follow the classical Michaelis-Menten kinetics and have unique steady-state kinetic parameters, K M, V max, and k cat. We found that k cat for all topoisomerases are rather low and that such low values may stem from the tight binding of topoisomerases to DNA. Additionally, we confirmed that novobiocin is a competitive inhibitor for adenosine 5'-triphosphate binding to E. coli DNA gyrase, demonstrating the utility of our assay for studying topoisomerase inhibitors.
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Affiliation(s)
- Yunke Wang
- Biomolecular
Sciences Institute, Department of Chemistry & Biochemistry, and Enviromental
and Occupational Health, Robert Stempel College of Public Health &
Social Work, Florida International University, Miami, Florida 33199, United States
- School
of Life Sciences, Nanjing University, Nanjing, Jiangsu Province 210023, P. R. China
| | - Samantha Rakela
- Biomolecular
Sciences Institute, Department of Chemistry & Biochemistry, and Enviromental
and Occupational Health, Robert Stempel College of Public Health &
Social Work, Florida International University, Miami, Florida 33199, United States
| | - Jeremy W. Chambers
- Biomolecular
Sciences Institute, Department of Chemistry & Biochemistry, and Enviromental
and Occupational Health, Robert Stempel College of Public Health &
Social Work, Florida International University, Miami, Florida 33199, United States
| | - Zi-Chun Hua
- School
of Life Sciences, Nanjing University, Nanjing, Jiangsu Province 210023, P. R. China
- Changzhou
High-Tech Research Institute of Nanjing University and Jiangsu TargetPharma
Laboratories Inc., Changzhou, Jiangsu 213164, P. R. China
| | - Mark T. Muller
- TopoGEN,
Inc., Buena Vista, Colorado 81211, United
States
| | - John L. Nitiss
- Pharmaceutical
Sciences Department, College of Pharmacy at Rockford, University of Illinois at Chicago, 1601 Parkview Avenue, N310, Rockford, Illinois 61107, United States
| | - Yuk-Ching Tse-Dinh
- Biomolecular
Sciences Institute, Department of Chemistry & Biochemistry, and Enviromental
and Occupational Health, Robert Stempel College of Public Health &
Social Work, Florida International University, Miami, Florida 33199, United States
| | - Fenfei Leng
- Biomolecular
Sciences Institute, Department of Chemistry & Biochemistry, and Enviromental
and Occupational Health, Robert Stempel College of Public Health &
Social Work, Florida International University, Miami, Florida 33199, United States
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Gokare P, Navaraj A, Zhang S, Motoyama N, Sung SS, Finnberg NK. Targeting of Chk2 as a countermeasure to dose-limiting toxicity triggered by topoisomerase-II (TOP2) poisons. Oncotarget 2017; 7:29520-30. [PMID: 27121056 PMCID: PMC5045414 DOI: 10.18632/oncotarget.8790] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 03/28/2016] [Indexed: 11/29/2022] Open
Abstract
The DNA damage response (DDR) gene cell cycle checkpoint kinase 2 (Chk2) triggers programmed cell death and lethal radiation-induced toxicity in mice in vivo. However, it is not well established to what extent targeting of Chk2 may protect from dose-limiting toxicities (DLT) inflicted by mainstay cancer chemotherapy. We screened different classes of chemotherapy in wild type and Chk2-deficient cells. Here we show that loss of Chk2 protect from cell death in vitro and lethal toxicity in vivo following treatment with topoisomerase II (TOP2)–inhibitors whereas no such protection was observed following treatment with topoisomerase I (TOP1) inhibitors. Furthermore, through combined in silico and functional screens of the Diversity Set II (NCI/NTP) chemical library we identified the carbanilide-derivative NSC105171, also known as ptu-23, as a novel Chk2 inhibitor (Chk2i). Indeed, NSC105171 can be administered safely to mice to countermeasure etoposide-induced toxicity. Incorporation of Chk2i into chemotherapy protocols employing TOP2-inhibitors may be an effective strategy to prevent DLT's without interfering with treatment.
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Affiliation(s)
- Prashanth Gokare
- Laboratory of Translational Oncology and Experimental Cancer Therapeutics, Department of Medical Oncology and Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.,Penn State Hershey Cancer Institute, Penn State Hershey Medical Center, Hershey, PA 17104, USA
| | - Arunasalam Navaraj
- Penn State Hershey Cancer Institute, Penn State Hershey Medical Center, Hershey, PA 17104, USA
| | - Shengliang Zhang
- Laboratory of Translational Oncology and Experimental Cancer Therapeutics, Department of Medical Oncology and Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.,Penn State Hershey Cancer Institute, Penn State Hershey Medical Center, Hershey, PA 17104, USA
| | - Noboru Motoyama
- Institute of Longevity, Department of Cognitive Brain Sciences Research Institute, National Center for Geriatrics and Gerontology, Aichi 474-8511, Japan
| | - Shen-Shu Sung
- Department of Pharmacology, Penn State College of Medicine, Hershey, PA 17104, USA
| | - Niklas K Finnberg
- Laboratory of Translational Oncology and Experimental Cancer Therapeutics, Department of Medical Oncology and Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.,Penn State Hershey Cancer Institute, Penn State Hershey Medical Center, Hershey, PA 17104, USA
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5
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Bansal S, Bajaj P, Pandey S, Tandon V. Topoisomerases: Resistance versus Sensitivity, How Far We Can Go? Med Res Rev 2016; 37:404-438. [PMID: 27687257 DOI: 10.1002/med.21417] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/04/2016] [Accepted: 08/29/2016] [Indexed: 12/15/2022]
Abstract
DNA topoisomerases are ubiquitously present remarkable molecular machines that help in altering topology of DNA in living cells. The crucial role played by these nucleases during DNA replication, transcription, and recombination vis-à-vis less sequence similarity among different species makes topoisomerases unique and attractive targets for different anticancer and antibacterial drugs. However, druggability of topoisomerases by the existing class of molecules is increasingly becoming questationable due to resistance development predominated by mutations in the corresponding genes. The current scenario facing a decline in the development of new molecules further comprises an important factor that may challenge topoisomerase-targeting therapy. Thus, it is imperative to wisely use the existing inhibitors lest with this rapid rate of losing grip over the target we may not go too far. Furthermore, it is important not only to design new molecules but also to develop new approaches that may avoid obstacles in therapies due to multiple resistance mechanisms. This review provides a succinct account of different classes of topoisomerase inhibitors, focuses on resistance acquired by mutations in topoisomerases, and discusses the various approaches to increase the efficacy of topoisomerase inhibitors. In a later section, we also suggest the possibility of using bisbenzimidazoles along with efflux pump inhibitors for synergistic bactericidal effects.
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Affiliation(s)
- Sandhya Bansal
- Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, New Delhi, India
| | - Priyanka Bajaj
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India
| | - Stuti Pandey
- Department of Chemistry, University of Delhi, New Delhi, India
| | - Vibha Tandon
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.,Department of Chemistry, University of Delhi, New Delhi, India
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Detection of the Epstein-Barr virus and DNA-topoisomerase II- α in recurrent and nonrecurrent giant cell lesion of the jawbones. BIOMED RESEARCH INTERNATIONAL 2013; 2013:327424. [PMID: 23956975 PMCID: PMC3727186 DOI: 10.1155/2013/327424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 06/09/2013] [Accepted: 06/10/2013] [Indexed: 11/18/2022]
Abstract
The aims of this study were to determine whether the expression of Topo II-α correlates with presence of EBV in giant cell lesion of the jawbones and whether it is predictive of clinical biologic behavior of these lesions. Paraffin-embedded tissues from 8 recurrent and 7 nonrecurrent cases of bony GCLs and 9 peripheral giant cell lesions (PGCLs) as a control group were assessed for the expression of EBV and Topo II-α using immunohistochemistry. The results showed positive staining for Topo II-α in mononuclear stromal cells (MSCs) and multinucleated giant cells (MGCs). Student t-test showed that mean Topo II-α labelling index (LI) in recurrent cases was significantly higher than that in non-recurrent cases (P = 0.0001). Moreover, Spearman's correlation coefficients method showed a significant correlation between DNA Topo II-α LI and both of gender and site in these lesions. Moderate EBV expression in relation to the highest Topo II-α LI was observed in two cases of GCT. It was concluded that high Topo II-α LIs could be identified as reliable predicators for the clinical behavior of GCLs. Moreover, EBV has no etiological role in the benign CGCLs in contrast to its role in the pathogenesis of GCTs.
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7
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Tamaichi H, Sato M, Porter ACG, Shimizu T, Mizutani S, Takagi M. Ataxia telangiectasia mutated-dependent regulation of topoisomerase II alpha expression and sensitivity to topoisomerase II inhibitor. Cancer Sci 2013; 104:178-84. [PMID: 23163762 DOI: 10.1111/cas.12067] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 11/14/2012] [Accepted: 11/14/2012] [Indexed: 11/28/2022] Open
Abstract
Topoisomerase II alpha (TOP2A) has a crucial role in proper chromosome condensation and segregation. Here we report the interaction of TOP2A with ataxia telangiectasia mutated (ATM) and its phosphorylation in an ATM-dependent manner after DNA damage. In vitro kinase assay and site-directed mutagenesis studies revealed that serine 1512 is the target of phosphorylation through ATM. Serine 1512 to Alanine mutation of TOP2A showed increased stability of the protein, retaining TOP2A activity at least with regard to cell survival activity. Ataxia telangiectasia-derived cell lines showed high levels of TOP2A that were associated with hypersensitivity to the TOP2 inhibitor etoposide. These findings suggest that ATM-dependent TOP2A modification is required for proper regulation of TOP2 stability and subsequently of the sensitivity to TOP2 inhibitor. In a lymphoblastoid cell line derived from a patient who developed MLL rearrangement, positive infant leukemia, defective ATM expression, and increased TOP2A expression were shown. It was intriguing that hypersensitivity to TOP2 inhibitor and susceptibility to MLL gene rearrangement were shown by low-dose etoposide exposure in this cell line. Thus, our findings have clinically important implications for the pathogenesis of infantile acute leukemia as well as treatment-associated secondary leukemia following exposure to TOP2 inhibitors.
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Affiliation(s)
- Hiroyuki Tamaichi
- Department of Pediatrics and Developmental Biology, Tokyo Medical and Dental University, Tokyo, Japan
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8
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Abstract
A new mechanism involving cleavage of a transcription factor called CREB3L1 has been proposed to explain the anti-tumour effects of doxorubicin.
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Affiliation(s)
- Anand G Patel
- is in the Department of Molecular Pharmacology and Experimental Therapeutics , Mayo Clinic , Rochester , United States
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9
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Lu H, Hallstrom TC. Sensitivity to TOP2 targeting chemotherapeutics is regulated by Oct1 and FILIP1L. PLoS One 2012; 7:e42921. [PMID: 22900064 PMCID: PMC3416772 DOI: 10.1371/journal.pone.0042921] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 07/13/2012] [Indexed: 12/28/2022] Open
Abstract
Topoisomerase II (TOP2) targeting drugs like doxorubicin and etoposide are frontline chemotherapeutics for a wide variety of solid and hematological malignancies, including breast and ovarian adenocarcinomas, lung cancers, soft tissue sarcomas, leukemias and lymphomas. These agents cause a block in DNA replication leading to a pronounced DNA damage response and initiation of apoptotic programs. Resistance to these agents is common, however, and elucidation of the mechanisms causing resistance to therapy could shed light on strategies to reduce the frequency of ineffective treatments. To explore these mechanisms, we utilized an unbiased shRNA screen to identify genes that regulate cell death in response to doxorubicin treatment. We identified the Filamin A interacting protein 1-like (FILIP1L) gene as a crucial mediator of apoptosis triggered by doxorubicin. FILIP1L shares significant similarity with bacterial SbcC, an ATPase involved in DNA repair. FILIP1L was originally described as DOC1, or “down-regulated in ovarian cancer” and has since been shown to be downregulated in a wide variety of human tumors. FILIP1L levels increase markedly through transcriptional mechanisms following treatment with doxorubicin and other TOP2 poisons, including etoposide and mitoxantrone, but not by the TOP2 catalytic inhibitors merbarone or dexrazoxane (ICRF187), or by UV irradiation. This induction requires the action of the OCT1 transcription factor, which relocalizes to the FILIP1L promoter and facilitates its expression following doxorubicin treatment. Our findings suggest that the FILIP1L expression status in tumors may influence the response to anti-TOP2 chemotherapeutics.
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Affiliation(s)
- Huarui Lu
- Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Timothy C. Hallstrom
- Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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11
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Jamieson D, Boddy AV. Pharmacogenetics of genes across the doxorubicin pathway. Expert Opin Drug Metab Toxicol 2011; 7:1201-10. [DOI: 10.1517/17425255.2011.610180] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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12
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Gheeya JS, Chen QR, Benjamin CD, Cheuk AT, Tsang P, Chung JY, Metaferia BB, Badgett TC, Johansson P, Wei JS, Hewitt SM, Khan J. Screening a panel of drugs with diverse mechanisms of action yields potential therapeutic agents against neuroblastoma. Cancer Biol Ther 2009; 8:2386-95. [PMID: 19946221 DOI: 10.4161/cbt.8.24.10184] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Neuroblastoma (NB) is the most common extracranial solid tumor in children. Despite current aggressive therapy, the survival rate for high risk NB remains less than 40%. To identify novel effective chemo-agents against NB, we screened a panel of 96 drugs against two NB cell lines, SK-N-AS and SH-SY5Y. We found 30 compounds that were active against NB cell lines at < or =10 microM concentration. More interestingly, 17 compounds are active at < or =1 microM concentration, and they act through a wide spectrum of diverse mechanisms such as mitotic inhibition, topoisomerase inhibition, targeting various biological pathways, and unknown mechanisms. The majority of these active compounds also induced caspase 3/7 by more than 2-fold. Of these 17 active compounds against NB cell lines at sub-micromolar concentration, eleven compounds are not currently used to treat NB. Among them, nine are FDA approved compounds, and three agents are undergoing clinical trials for various malignancies. Furthermore, we identified four agents active against these NB cell lines that have not yet been tested in the clinical setting. Finally we demonstrated that Cucurbitacin I inhibits neuroblastoma cell growth through inhibition of STAT3 pathway. These drugs thus represent potential novel therapeutic agents for patients with NB, and further validation studies are needed to translate them to the clinic.
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Affiliation(s)
- Jinesh S Gheeya
- Oncogenomics Section, Pediatric Oncology Branch, Advanced Technology Center, National Cancer Institute, Gaithersburg, MD, USA
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13
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Pyranonaphthoquinone derivatives of eleutherin, ventiloquinone L, thysanone and nanaomycin A possessing a diverse topoisomerase II inhibition and cytotoxicity spectrum. Bioorg Med Chem 2009; 17:7131-7. [DOI: 10.1016/j.bmc.2009.08.064] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 08/20/2009] [Accepted: 08/29/2009] [Indexed: 11/24/2022]
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Evidence for the presence of R250G mutation at the ATPase domain of topoisomerase II in an arsenite-resistant Leishmania donovani exhibiting a differential drug inhibition profile. Int J Antimicrob Agents 2009; 33:80-5. [DOI: 10.1016/j.ijantimicag.2008.06.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Revised: 04/21/2008] [Accepted: 06/23/2008] [Indexed: 12/11/2022]
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Abstract
Eukaryotic type II topoisomerases (Topo II) are implicated in a wide range of cellular processes. Cells in which Topo II protein has been specifically depleted or mutated provide powerful systems for analysing the normal in vivo functions of Topo II proteins and for assessing their roles in various chemotherapy regimens. Summarised here are the ways in which Topo II has been depleted or mutated in animal cells and the type of information gleaned. The cell lines generated are tabulated and represent a useful resource for further in vivo studies of Topo II function, one that we expect to grow in size and utility in the coming years.
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Affiliation(s)
- Andrew C G Porter
- Department of Haematology, Imperial College Faculty of Medicine, London, UK
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Shamaa AA, Zyada MM, Wagner M, Awad SS, Osman MM, Abdel Azeem AA. The significance of Epstein Barr virus (EBV) & DNA topoisomerase II alpha (DNA-Topo II alpha) immunoreactivity in normal oral mucosa, oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). Diagn Pathol 2008; 3:45. [PMID: 19021895 PMCID: PMC2611966 DOI: 10.1186/1746-1596-3-45] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Accepted: 11/20/2008] [Indexed: 12/04/2022] Open
Abstract
Background Head and neck cancer including oral cancer is considered to develop by accumulated genetic alterations and the major pathway is cancerization from lesions such as intraepithelial dysplasia in oral leukoplakia and erythroplakia. The relationship of proliferation markers with the grading of dysplasia is uncertain. The involvement of EBV in oral carcinogenesis is not fully understood. Aim The present study was designed to investigate the role of EBV and DNA Topoisomerase II∝ (DNA-Topo II∝) during oral carcinogenesis and to examine the prognostic significance of these protein expressions in OSCCs. Methods Using specific antibodies for EBV and DNA-Topo II∝, we examined protein expressions in archival lesion tissues from 16 patients with oral epithelial dysplasia, 22 oral squamous cell carcinoma and 20 normal oral mucosa by immunohistochemistry. Clinical information was obtained through the computerized retrospective database from the tumor registry. Results DNA-Topo II∝ was expressed in all examined specimens. Analysis of Variance ANOVA revealed highly significant difference (P < 0.01) in young aged labial tissues and significant (P ≤ 0.05) in gingival and not significant (P > 0.05) in inferior surface of tongue and in hard palatal tissues. Significant differences were observed between OEDs and NSE (P < 0.001) and SCCs and controls (P < 0.001), also, significant differences could be observed between SCCs and OEDs. DNA-Topo II∝ expression was significantly higher in tumors of low differentiation versus tumors of moderate and high differentiation (P < 0.001), DNA-Topo II∝ expression was correlated with age, tumor size, tumor stage, node metastasis and tumor differentiation, but not with gender and tumor site. None of normal squamous epithelium (NSE) expressed EBV. Heterogenous reactivity for EBV was observed through the series of dysplasia and squamous cell carcinoma. Its expression increased progressively with lymph node metastasis and low tumor differentiation, but no significant association could be observed with other clinicopathological parameters. EBV protein expression was increased with elevated Topo II-∝ LI in OEDs and OSCCs. A tendency to positive correlation between EBV and Topo II∝ expression was observed in OEDs but not in OSCCs. Conclusion EBV and DNA Topo II-αLI expression are possible indicators in oral carcinogenesis and may be valuable diagnostic and prognostic indices in oral carcinoma.
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Affiliation(s)
- Ali A Shamaa
- Oral Biology Department, Faculty of Dentistry, Minia University, Minia, Egypt.
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17
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Rogojina AT, Nitiss JL. Isolation and characterization of mAMSA-hypersensitive mutants. Cytotoxicity of Top2 covalent complexes containing DNA single strand breaks. J Biol Chem 2008; 283:29239-50. [PMID: 18723844 DOI: 10.1074/jbc.m804058200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Topoisomerase II (Top2) is the primary target for active anti-cancer agents. We developed an efficient approach for identifying hypersensitive Top2 mutants and isolated a panel of mutants in yeast Top2 conferring hypersensitivity to the intercalator N-[4-(9-acridinylamino)-3-methoxyphenyl]methanesulphonanilide (mAMSA). Some mutants conferred hypersensitivity to etoposide as well as mAMSA, whereas other mutants exhibited hypersensitivity only to mAMSA. Two mutants in Top2, changing Pro(473) to Leu and Gly(737) to Val, conferred extraordinary hypersensitivity to mAMSA and were chosen for further characterization. The mutant proteins were purified, and their biochemical activities were assessed. Both mutants encode enzymes that are hypersensitive to inhibition by mAMSA and other intercalating agents and exhibited elevated levels of mAMSA-induced Top2:DNA covalent complexes. While Gly(737) --> Val Top2p generated elevated levels of Top2-mediated double strand breaks in vitro, the Pro(473) --> Leu mutant protein showed only a modest increase in Top2-mediated double strand breaks but much higher levels of Top2-mediated single strand breaks. In addition, the Pro(473) --> Leu mutant protein also generated high levels of mAMSA-stabilized covalent complexes in the absence of ATP. We tested the role of single strand cleavage in cell killing with alleles of Top2 that could generate single strand breaks, but not double strand breaks. Expression in yeast of a Pro(473) --> Leu mutant that could only generate single strand breaks conferred hypersensitivity to mAMSA. These results indicate that generation of single strand breaks by Top2-targeting agents can be an important component of cell killing by Top2-targeting drugs.
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Affiliation(s)
- Anna T Rogojina
- Molecular Pharmacology Department, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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Burgess DJ, Doles J, Zender L, Xue W, Ma B, McCombie WR, Hannon GJ, Lowe SW, Hemann MT. Topoisomerase levels determine chemotherapy response in vitro and in vivo. Proc Natl Acad Sci U S A 2008; 114:689-94. [PMID: 18574145 DOI: 10.3171/2010.2.jns09719] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Topoisomerase poisons are chemotherapeutic agents that are used extensively for treating human malignancies. These drugs can be highly effective, yet tumors are frequently refractory to treatment or become resistant upon tumor relapse. Using a pool-based RNAi screening approach and a well characterized mouse model of lymphoma, we explored the genetic basis for heterogeneous responses to topoisomerase poisons in vitro and in vivo. These experiments identified Top2A expression levels as major determinants of response to the topoisomerase 2 poison doxorubicin and showed that suppression of Top2A produces resistance to doxorubicin in vitro and in vivo. Analogously, using a targeted RNAi approach, we demonstrated that suppression of Top1 produces resistance to the topoisomerase 1 poison camptothecin yet hypersensitizes cancer cells to doxorubicin. Importantly, lymphomas relapsing after treatment display spontaneous changes in topoisomerase levels as predicted by in vitro gene knockdown studies. These results highlight the utility of pooled shRNA screens for identifying genetic determinants of chemotherapy response and suggest strategies for improving the effectiveness of topoisomerase poisons in the clinic.
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Affiliation(s)
- Darren J Burgess
- Cold Spring Harbor Laboratory and Howard Hughes Medical Institute, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA
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19
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Topoisomerase levels determine chemotherapy response in vitro and in vivo. Proc Natl Acad Sci U S A 2008; 105:9053-8. [PMID: 18574145 DOI: 10.1073/pnas.0803513105] [Citation(s) in RCA: 231] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Topoisomerase poisons are chemotherapeutic agents that are used extensively for treating human malignancies. These drugs can be highly effective, yet tumors are frequently refractory to treatment or become resistant upon tumor relapse. Using a pool-based RNAi screening approach and a well characterized mouse model of lymphoma, we explored the genetic basis for heterogeneous responses to topoisomerase poisons in vitro and in vivo. These experiments identified Top2A expression levels as major determinants of response to the topoisomerase 2 poison doxorubicin and showed that suppression of Top2A produces resistance to doxorubicin in vitro and in vivo. Analogously, using a targeted RNAi approach, we demonstrated that suppression of Top1 produces resistance to the topoisomerase 1 poison camptothecin yet hypersensitizes cancer cells to doxorubicin. Importantly, lymphomas relapsing after treatment display spontaneous changes in topoisomerase levels as predicted by in vitro gene knockdown studies. These results highlight the utility of pooled shRNA screens for identifying genetic determinants of chemotherapy response and suggest strategies for improving the effectiveness of topoisomerase poisons in the clinic.
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20
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Studies on the anti-proliferative effects of novel DNA-intercalating bipyridyl–thiourea–Pt(II) complexes against cisplatin-sensitive and -resistant human ovarian cancer cells. J Inorg Biochem 2008; 102:699-712. [DOI: 10.1016/j.jinorgbio.2007.10.015] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 10/02/2007] [Accepted: 10/30/2007] [Indexed: 11/17/2022]
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21
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Qi H, Lin CP, Fu X, Wood LM, Liu AA, Tsai YC, Chen Y, Barbieri CM, Pilch DS, Liu LF. G-quadruplexes induce apoptosis in tumor cells. Cancer Res 2007; 66:11808-16. [PMID: 17178877 DOI: 10.1158/0008-5472.can-06-1225] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Several G-rich oligodeoxynucleotides (ODNs), which are capable of forming G-quadruplexes, have been shown to exhibit antiproliferative activity against tumor cell lines and antitumor activity in nude mice carrying prostate and breast tumor xenografts. However, the molecular basis for their antitumor activity remains unclear. In the current study, we showed that a variety of telomeric G-tail oligodeoxynucleotides (TG-ODNs) exhibited antiproliferative activity against many tumor cells in culture. Systematic mutational analysis of the TG-ODNs suggests that the antiproliferative activity depends on the G-quadruplex conformation of these TG-ODNs. TG-ODNs were also shown to induce poly(ADP-ribose) polymerase-1 cleavage, phosphatidylserine flipping, and caspase activation, indicative of induction of apoptosis. TG-ODN-induced apoptosis was largely ataxia telangiectasia mutated (ATM) dependent. Furthermore, TG-ODN-induced apoptosis was inhibited by the c-Jun NH(2)-terminal kinase (JNK) inhibitor SP600125. Indeed, TG-ODNs were shown to activate the JNK pathway in an ATM-dependent manner as evidenced by elevated phosphorylation of JNK and c-Jun. Interestingly, a number of G-quadruplex ODNs (GQ-ODN) derived from nontelomeric sequences also induced ATM/JNK-dependent apoptosis, suggesting a possible common mechanism of tumor cell killing by GQ-ODNs.
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Affiliation(s)
- Haiyan Qi
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
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22
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Fryknäs M, Rickardson L, Wickström M, Dhar S, Lövborg H, Gullbo J, Nygren P, Gustafsson MG, Isaksson A, Larsson R. Phenotype-based screening of mechanistically annotated compounds in combination with gene expression and pathway analysis identifies candidate drug targets in a human squamous carcinoma cell model. ACTA ACUST UNITED AC 2006; 11:457-68. [PMID: 16928983 DOI: 10.1177/1087057106288048] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The squamous cell carcinoma HeLa cell line and an epithelial cell line hTERT-RPE with a nonmalignant phenotype were interrogated for HeLa cell selectivity in response to 1267 annotated compounds representing 56 pharmacological classes. Selective cytotoxic activity was observed for 14 of these compounds dominated by cyclic adenosine monophosphate (cAMP) selective phosphodiesterase (PDE) inhibitors, which tended to span a representation of the chemical descriptor space of the library. The PDE inhibitors induced delayed cell death with features compatible with classical apoptosis. The PDE inhibitors were largely inactive when tested against a cell line panel consisting of hematological and nonsquamous epithelial phenotypes. In a genome-wide DNA microarray analysis, PDE3A and PDE2A were found to be significantly increased in HeLa cells compared to the other cell lines. The pathway analysis software PathwayAssist was subsequently used to extract a list of proteins and small molecules retrieved from Medline abstracts associated with the hit compounds. The resulting list consisted of major parts of the cAMP-protein kinase A pathway linking to ERK, P38, and AKT. This molecular network may provide a basis for further exploitation of novel candidate targets for the treatment of squamous cell carcinoma.
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Affiliation(s)
- Mårten Fryknäs
- Department of Genetics and Pathology, Uppsala University, S-751 85 Uppsala, Sweden
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23
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Rickardson L, Fryknäs M, Haglund C, Lövborg H, Nygren P, Gustafsson MG, Isaksson A, Larsson R. Screening of an annotated compound library for drug activity in a resistant myeloma cell line. Cancer Chemother Pharmacol 2006; 58:749-58. [PMID: 16528529 DOI: 10.1007/s00280-006-0216-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 02/16/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE Resistance to anticancer drugs is a major problem in chemotherapy. In order to identify drugs with selective cytotoxic activity in drug-resistant cancer cells, the annotated compound library LOPAC1280, containing compounds from 56 pharmacological classes, was screened in the myeloma cell line RPMI 8226 and its doxorubicin-resistant subline 8226/Dox40. METHODS Cell survival was measured by the Fluorometric Microculture Cytotoxicity Assay. RESULTS Selective cytotoxic activity in 8226/Dox40 was obtained for 33 compounds, with the most pronounced difference observed for the glucocorticoids. A microarray analysis of the cells showed a difference in mRNA-expression for the glucocorticoid receptor suggesting potential mechanisms for the difference in glucocorticoid sensitivity. In the presence of the glucocorticoid-receptor antagonist RU486, the sensitivity to the glucocorticoids was reduced and a similar effect level in RPMI 8226 and 8226/Dox40 was achieved. CONCLUSION In conclusion, screening of mechanistically annotated compounds on drug-resistant cancer cells can identify compounds with selective activity and provide a basis for the development of novel treatments of drug-resistant malignancies.
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Affiliation(s)
- Linda Rickardson
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University, 751 85, Uppsala, Sweden.
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24
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Rickardson L, Fryknäs M, Dhar S, Lövborg H, Gullbo J, Rydåker M, Nygren P, Gustafsson MG, Larsson R, Isaksson A. Identification of molecular mechanisms for cellular drug resistance by combining drug activity and gene expression profiles. Br J Cancer 2005; 93:483-92. [PMID: 16012520 PMCID: PMC2361589 DOI: 10.1038/sj.bjc.6602699] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Acquired drug resistance is a major problem in cancer treatment. To explore the genes involved in chemosensitivity and resistance, 10 human tumour cell lines, including parental cells and resistant subtypes selected for resistance against doxorubicin, melphalan, teniposide and vincristine, were profiled for mRNA expression of 7400 genes using cDNA microarray technology. The drug activity of 66 cancer agents was evaluated on the cell lines, and correlations between drug activity and gene expression were calculated and ranked. Hierarchical clustering of drugs based on their drug–gene correlations yielded clusters of drugs with similar mechanism of action. Genes correlated with drug sensitivity and resistance were imported into the PathwayAssist software to identify putative molecular pathways involved. A substantial number of both proapoptotic and antiapoptotic genes such as signal transducer and activator of transcription 1, mitogen-activated protein kinase 1 and focal adhesion kinase were found to be associated to drug resistance, whereas genes linked to cell cycle control and proliferation, such as cell division cycle 25A and signal transducer of activator of transcription 5A, were associated to general drug sensitivity. The results indicate that combined information from drug activity and gene expression in a resistance-based cell line panel may provide new knowledge of the genes involved in anticancer drug resistance and become a useful tool in drug development.
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Affiliation(s)
- L Rickardson
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University Hospital, S-751 85 Uppsala, Sweden
| | - M Fryknäs
- Department of Genetics and Pathology, Uppsala University, S-751 85 Uppsala, Sweden
| | - S Dhar
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University Hospital, S-751 85 Uppsala, Sweden
| | - H Lövborg
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University Hospital, S-751 85 Uppsala, Sweden
| | - J Gullbo
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University Hospital, S-751 85 Uppsala, Sweden
| | - M Rydåker
- Department of Genetics and Pathology, Uppsala University, S-751 85 Uppsala, Sweden
| | - P Nygren
- Department of Oncology, Radiology and Clinical Immunology, Uppsala University, S-751 85 Uppsala, Sweden
| | - M G Gustafsson
- Department of Genetics and Pathology, Uppsala University, S-751 85 Uppsala, Sweden
- Department of Engineering Sciences, Uppsala University, S-751 85 Uppsala, Sweden
| | - R Larsson
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University Hospital, S-751 85 Uppsala, Sweden
- Department of Medical Sciences, Division of Clinical Pharmacology, Uppsala University Hospital, S-751 85 Uppsala, Sweden. E-mail:
| | - A Isaksson
- Department of Genetics and Pathology, Uppsala University, S-751 85 Uppsala, Sweden
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25
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Random mutagenesis of the B'A' core domain of yeast DNA topoisomerase II and large-scale screens of mutants resistant to the anticancer drug etoposide. Biochem Biophys Res Commun 2005; 327:597-603. [PMID: 15629155 DOI: 10.1016/j.bbrc.2004.12.049] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Indexed: 11/23/2022]
Abstract
Mutagenic PCR method was applied to introduce point mutations to the B'A' core domain of yeast DNA topoisomerase II. Screens for mutants resistant to the anticancer drug etoposide were carried out in a yeast ts system in the presence of high concentrations of the drug or in a drug-hypersensitive genetic background. 129 mutants were obtained from a total of 47,000 transformants. Nucleotide sequencing of 40 selected mutants showed that a large number of the mutations map to regions encoding the linker that joins the ATPase domain to the B' module and the B'A' linker. Significant reduction in catalytic activity was evident for a large fraction of mutant enzymes and all mutants were also resistant to amsacrine, another topoisomerase II drug with a different chemical structure, suggesting that few of the mutations reflect simple changes of specific amino acid side chains that are directly involved in enzyme-drug interactions.
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26
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Walker JV, Nitiss KC, Jensen LH, Mayne C, Hu T, Jensen PB, Sehested M, Hsieh T, Nitiss JL. A mutation in human topoisomerase II alpha whose expression is lethal in DNA repair-deficient yeast cells. J Biol Chem 2004; 279:25947-54. [PMID: 15037624 DOI: 10.1074/jbc.m312314200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type II DNA topoisomerases are ATP-dependent enzymes that catalyze alterations in DNA topology. These enzymes are important targets of a variety of anti-bacterial and anti-cancer agents. We identified a mutation in human topoisomerase II alpha, changing aspartic acid 48 to asparagine, that has the unique property of failing to transform yeast cells deficient in recombinational repair. In repair-proficient yeast strains, the Asp-48 --> Asn mutant can be expressed and complements a temperature-sensitive top2 mutation. Purified Asp-48 --> Asn Top2alpha has relaxation and decatenation activity similar to the wild type enzyme, but the purified protein exhibits several biochemical alterations compared with the wild type enzyme. The mutant enzyme binds both covalently closed and linear DNA with greater avidity than the wild type enzyme. hTop2alpha(Asp-48 --> Asn) also exhibited elevated levels of drug-independent cleavage compared with the wild type enzyme. The enzyme did not show altered sensitivity to bisdioxopiperazines nor did it form stable closed clamps in the absence of ATP, although the enzyme did form elevated levels of closed clamps in the presence of a non-hydrolyzable ATP analog compared with the wild type enzyme. We suggest that the lethality exhibited by the mutant is likely because of its enhanced drug-independent cleavage, and we propose that alterations in the ATP binding domain of the enzyme are capable of altering the interactions of the enzyme with DNA. This mutant enzyme also serves as a new model for understanding the action of drugs targeting topoisomerase II.
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Affiliation(s)
- Jerrylaine V Walker
- Department of Molecular Pharmacology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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27
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Suda N, Ito Y, Imai T, Kikumori T, Kikuchi A, Nishiyama Y, Yoshida S, Suzuki M. The alpha4 residues of human DNA topoisomerase IIalpha function in enzymatic activity and anticancer drug sensitivity. Nucleic Acids Res 2004; 32:1767-73. [PMID: 15026536 PMCID: PMC390336 DOI: 10.1093/nar/gkh339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2003] [Revised: 02/23/2004] [Accepted: 02/23/2004] [Indexed: 11/12/2022] Open
Abstract
We introduced a series of Pro substitutions within and near the alpha4 helix, a part of the breakage/rejoining region, in human DNA topoisomerase IIalpha, and analyzed if this region is involved in determination of anti-cancer drug sensitivity in a temperature- sensitive yeast strain (top2-4 allele). Among the 19 mutants generated, H759P and N770P showed resistance to etoposide and doxorubicin at the non-permissive temperature, where cell growth depends on activity of the human enzyme. For these residues, mutants with an Ala substitution were further created, in which H759A also showed resistance to etoposide. H759P, H759A and N770P were expressed, purified and subjected to in vitro measurement of drug sensitivity. They generated lower amounts of the etoposide-induced cleavable complexes, and were also found to have lower decatenation activity than the wild-type. In the crystal structure, the yeast equivalent of His759 is found in the vicinity of the Arg713, a putative anchoring residue of the 3'-side of cleaved DNA strands. These results suggest that His759 and the other alpha4 helix residues are involved in the enzymatic activity and drug sensitivity of human DNA topoisomerase IIalpha, via interaction with cleaved DNA.
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Affiliation(s)
- Namiko Suda
- Department of Endocrine Surgery, Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan
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28
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Oestergaard VH, Bjergbaek L, Skouboe C, Giangiacomo L, Knudsen BR, Andersen AH. The transducer domain is important for clamp operation in human DNA topoisomerase IIalpha. J Biol Chem 2003; 279:1684-91. [PMID: 14583603 DOI: 10.1074/jbc.m309624200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
DNA topoisomerase II is a multidomain homodimeric enzyme that changes DNA topology by coupling ATP hydrolysis to the transport of one DNA helix through a transient double-stranded break in another. The process requires dramatic conformational changes including closure of an ATP-operated clamp, which is comprised of two N-terminal domains from each protomer. The most N-terminal domain contains the ATP-binding site and is directly involved in clamp closure, undergoing dimerization upon ATP binding. The second domain, the transducer domain, forms the walls of the N-terminal clamp and connects the clamp to the enzyme core. Although structurally conserved, it is unclear whether the transducer domain is involved in clamp mechanism. We have purified and characterized a human topoisomerase II alpha enzyme with a two-amino acid insertion at position 408 in the transducer domain. The enzyme retains both ATPase and DNA cleavage activities. However, the insertion, which is situated far from the N-terminal dimerization area, severely disrupts the function of the N-terminal clamp. The clamp-deficient enzyme is catalytically inactive and lacks most aspects of interdomain communication. Surprisingly, it seems to have retained the intersubunit communication, allowing it to bind ATP cooperatively in the presence of DNA. The results show that even distal parts of the transducer domain are important for the dynamics of the N-terminal clamp and furthermore indicate that stable clamp closure is not required for cooperative binding of ATP.
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Affiliation(s)
- Vibe H Oestergaard
- Department of Molecular Biology, University of Aarhus, C. F. Møllers Allé, Building 130, 8000 Aarhus C, Denmark
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29
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Schwarzenbach H. Expression of MDR1/P-glycoprotein, the multidrug resistance protein MRP, and the lung-resistance protein LRP in multiple myeloma. Med Oncol 2002; 19:87-104. [PMID: 12180485 DOI: 10.1385/mo:19:2:87] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study was to determine the incidence of three genes associated with multidrug resistance (MDR) in multiple myeloma in relation to treatment status. MDR1/Pgp (P-glycoprotein) expression was detected in 41% of 93 myeloma samples. Generally, the incidence of MDR1/Pgp expression was higher in pretreated samples, and treatments with doxorubicin and/or vincristine were more effective in MDR1/Pgp expression than with alkylating agents. A significant association was observed between MDR1 /Pgp-positiveness and the ability of verapmil to increase doxorubicin sensitivity, suggesting functional relevance of MDR1/Pgp expression. MRP (multidrug resistance protein) expression was detected in 20.5% of 88 myeloma samples, in 26% at the mRNA level analyzed by quantitative reverse transriptase-polymerase chain reaction, and in only 3 of 79 samples by immunohistochemistry. LRP (lung-resistance protein) protein expression was observed in 12.5% of 72 myeloma samples. MRP and LRP expression was similar in samples with and without prior therapy. Approximately 80% of the myeloma samples with detectable mRNA expression of MDRI and MRP exhibited low expression levels corresponding to < 10% of the Pgp- and MRP-overexpressing multidrug-resistant human myeloma cell lines 8226/Dox6 and 8226/DOXint40c, respectively. Some normal bone marrow samples showed higher levels of MRP mRNA as compared to myeloma specimens, whereas MDRI mRNA expression in normal bone marrow was much lower (< or = 5%) than that in 8226/Dox6. These findings indicate a requirement to develop single-cell assays for MRP detection in multiple myeloma that are more sensitive than immunohistochemistry and might be useful to evaluate the incidence of genes associated with MDR.
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30
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Schwarzenbach H. A diagnostic tool for monitoring multidrug resistance expression in human tumor tissues. Anal Biochem 2002; 308:26-33. [PMID: 12234460 DOI: 10.1016/s0003-2697(02)00228-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Studies on multidrug resistance (MDR) require a sensitive and quantitative assay of mRNA expression in clinical tumor samples. Based on the small size, heterogenity, and the possibility of partial degradation of clinical specimens, unambiguous data are often difficult to obtain. The aim of the present study was to develop a multiplex polymerase chain reaction (PCR) in combination with nested PCR for quantitative analyses of mRNA expression of MDR1, MRP (multidrug resistance protein), and DNA topoisomerase IIalpha in small amounts of tumor tissue. RNA samples extracted from the human cell line RPMI 8226 and its MDR sublines 8226/Dox6 and DOXint40c, that overexpress MDR1 and MRP, respectively, were used as model substrates. In the first step, cDNAs of the three genes as well as of the housekeeping gene beta-actin were simultaneously amplified in single tubes using 20 cycles of PCR after random-primed reverse transcription. When necessary, a second amplification step of the preamplified PCR products was employed using nested primer pairs. Primer competition was evaluated by analyses of serially diluted amounts of cDNA and at different numbers of PCR cycles. Based on the results obtained, this multiplex/nested PCR approach may provide a base for quantitative analyses of MDR1, MRP, and topoisomerase IIalpha mRNA expression in clinical tumor biopsies.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/biosynthesis
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- Actins/genetics
- Blotting, Southern
- DNA Primers/genetics
- DNA Topoisomerases, Type II/biosynthesis
- DNA Topoisomerases, Type II/genetics
- DNA, Complementary/genetics
- Drug Resistance, Multiple
- Drug Resistance, Neoplasm
- Gene Expression
- Humans
- Multidrug Resistance-Associated Proteins/biosynthesis
- Multidrug Resistance-Associated Proteins/genetics
- Multiple Myeloma/drug therapy
- Multiple Myeloma/genetics
- Multiple Myeloma/metabolism
- Polymerase Chain Reaction/methods
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Tumor Cells, Cultured
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31
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Wessel I, Jensen LH, Renodon-Corniere A, Sorensen TK, Nitiss JL, Jensen PB, Sehested M. Human small cell lung cancer NYH cells resistant to the bisdioxopiperazine ICRF-187 exhibit a functional dominant Tyr165Ser mutation in the Walker A ATP binding site of topoisomerase II alpha. FEBS Lett 2002; 520:161-6. [PMID: 12044890 DOI: 10.1016/s0014-5793(02)02805-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bisdioxopiperazine anti-cancer agents are catalytic inhibitors of topoisomerase II which by unknown means lock the enzyme in a closed clamp form and inhibit its ATPase activity. In order to demarcate a putative pharmacophore, we here describe a novel Tyr165Ser mutation in the enzyme's Walker A ATP binding site leading to specific bisdioxopiperazine resistance when transformed into a temperature-conditional yeast system. The Tyr165Ser mutation differed from a previously described Arg162Gln by being heterozygous and by purified Tyr165Ser enzyme being drug-resistant in a kinetoplast DNA decatenation enzymatic assay. This suggested dominant nature of Tyr165Ser was supported by co-transformation studies in yeast of plasmids carrying wild type and mutant genes. These results enable a model of the bisdioxopiperazine pharmacophore using the proposed asymmetric ATP hydrolysis of the enzyme.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Amino Acid Substitution
- Antigens, Neoplasm
- Antineoplastic Agents/pharmacology
- Binding Sites/genetics
- Carcinoma, Small Cell/enzymology
- Carcinoma, Small Cell/genetics
- Carcinoma, Small Cell/pathology
- Cell Division/drug effects
- Cell Division/genetics
- DNA Topoisomerases, Type II/genetics
- DNA Topoisomerases, Type II/metabolism
- DNA-Binding Proteins
- Dose-Response Relationship, Drug
- Drug Resistance, Fungal/genetics
- Drug Resistance, Neoplasm/genetics
- Genotype
- Humans
- Lung Neoplasms/enzymology
- Lung Neoplasms/genetics
- Lung Neoplasms/pathology
- Mutation
- Protein Binding
- Razoxane/pharmacology
- Saccharomyces cerevisiae/drug effects
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/growth & development
- Transformation, Genetic
- Tumor Cells, Cultured/drug effects
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Affiliation(s)
- Irene Wessel
- Department of Pathology, Laboratory Center, Rigshospitalet 5431, DK-2100 Copenhagen, Denmark
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32
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Abstract
DNA topoisomerases are essential enzymes that regulate the conformational changes in DNA topology by catalysing the concerted breakage and rejoining of DNA strands during normal cellular growth. Over the past few years there has been considerable pharmacological interest in these enzymes because inhibitors of DNA topoisomerases represent a major class of anticancer drugs. This review highlights topoisomerase-targeting drugs that have shown promising anticancer activities. The mechanisms by which those drugs interfere with the catalytic cycles of type I and type II DNA topoisomerases and the factors involved in the development of resistance to these drugs are discussed.
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Affiliation(s)
- Z Topcu
- Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Ege University, 35100 Izmir, Turkey.
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33
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Okada Y, Tosaka A, Nimura Y, Kikuchi A, Yoshida S, Suzuki M. Atypical multidrug resistance may be associated with catalytically active mutants of human DNA topoisomerase II alpha. Gene 2001; 272:141-8. [PMID: 11470519 DOI: 10.1016/s0378-1119(01)00554-6] [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: 11/16/2022]
Abstract
In human cells, atypical drug resistance was previously identified with reduced catalytic activity or nuclear localization efficiency of DNA topoisomerase II alpha (TOP2 alpha). We have shown two etoposide resistant hTOP2 alpha mutants, K798L and K798P confer resistance to etoposide. In this work, we showed these mutants are also resistant against doxorubicin and mAMSA in vivo in the yeast strain ISE2, rad52, top2-4 at the non-permissive temperature. We purified these mutants to characterize the drug resistant mechanism. Purified recombinant proteins were 8- to 12-fold more resistant to etoposide and doxorubicin than wild type TOP2 alpha, and 2-fold more resistant to amsacrine, as measured by accumulation of cleavable DNA. These data show that K798L and K798P may be intrinsically resistant against these drugs in vitro and that this character may confer atypical multidrug resistant phenotype in vivo in yeast.
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Affiliation(s)
- Y Okada
- The First Department of Surgery, Nagoya University School of Medicine, Nagoya, 466-8550, Japan
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34
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Fortune JM, Lavrukhin OV, Gurnon JR, Van Etten JL, Lloyd RS, Osheroff N. Topoisomerase II from Chlorella virus PBCV-1 has an exceptionally high DNA cleavage activity. J Biol Chem 2001; 276:24401-8. [PMID: 11323425 DOI: 10.1074/jbc.m101693200] [Citation(s) in RCA: 32] [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
Chlorella virus PBCV-1 topoisomerase II is the only functional type II enzyme known to be encoded by a virus that infects eukaryotic cells. However, it has not been established whether the protein is expressed following viral infection or whether the enzyme has any catalytic features that distinguish it from cellular type II topoisomerases. Therefore, the present study characterized the physiological expression of PBCV-1 topoisomerase II and individual reaction steps catalyzed by the enzyme. Results indicate that the topoisomerase II gene is widely distributed among Chlorella viruses and that the protein is expressed 60-90 min after viral infection of algal cells. Furthermore, the enzyme has an extremely high DNA cleavage activity that sets it apart from all known eukaryotic type II topoisomerases. Levels of DNA scission generated by the viral enzyme are approximately 30 times greater than those observed with human topoisomerase IIalpha. The high levels of cleavage are not due to inordinately tight enzyme-DNA binding or to impaired DNA religation. Thus, they most likely reflect an elevated forward rate of scission. The robust DNA cleavage activity of PBCV-1 topoisomerase II provides a unique tool for studying the catalytic functions of type II topoisomerases.
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Affiliation(s)
- J M Fortune
- Departments of Biochemistry and Medicine (Hematology/Oncology), Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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Abstract
DNA topoisomerases are double-edged swords. They are essential for many vital functions of DNA during normal cell growth. However, they are also highly vulnerable under various physiological and nonphysiological stresses because of their delicate act on breaking and rejoining DNA. These stresses (e.g. exposure to topoisomerase poisons, acidic pH, and oxidative stresses) can convert DNA topoisomerases into DNA-breaking nucleases, resulting in cell death and/or genomic instability. The importance of topoisomerase-mediated DNA cleavage in tumor cell death and carcinogenesis has been recognized. This review focuses on recent findings concerning the molecular mechanisms of the stress responses to topoisomerase-mediated DNA damage. The involvement of ubiquitin/26S proteasome and SUMO/UBC9 in these processes, as well as the role of topoisomerase cleavable complexes in apoptotic cell death are discussed.
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Affiliation(s)
- T K Li
- Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA.
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Wang H, Mao Y, Zhou N, Hu T, Hsieh TS, Liu LF. Atp-bound topoisomerase ii as a target for antitumor drugs. J Biol Chem 2001; 276:15990-5. [PMID: 11278845 DOI: 10.1074/jbc.m011143200] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Topoisomerase II (TOP2) poisons interfere with the breakage/reunion reaction of TOP2 resulting in DNA cleavage. In the current studies, we show that two different classes (ATP-sensitive and -insensitive) of TOP2 poisons can be identified based on their differential sensitivity to the ATP-bound conformation of TOP2. First, in the presence of 1 mm ATP or the nonhydrolyzable analog adenosine 5'-(beta,gamma-imino)triphosphate, TOP2-mediated DNA cleavage induced by ATP-sensitive TOP2 poisons (e.g. doxorubicin, etoposide, mitoxantrone, and 4'-(9-acridinylamino)methanesulfon-m-anisidide) was 30-100-fold stimulated, whereas DNA cleavage induced by ATP-insensitive TOP2 poisons (e.g. amonafide, batracylin, and menadione) was only slightly (less than 3-fold) affected. In addition, ADP was shown to strongly antagonize TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive TOP2 poisons. Second, C427A mutant human TOP2alpha, which exhibits reduced ATPase activity, was shown to exhibit cross-resistance to all ATP-sensitive but not ATP-insensitive TOP2 poisons. Third, using ciprofloxacin competition assay, TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive poisons was shown to be antagonized by ciprofloxacin. These results suggest that ATP-bound TOP2 may be the specific target of ATP-sensitive TOP2 poisons. Using Lac repressor-operator complexes as roadblocks, we show that ATP-bound TOP2 acts as a circular clamp capable of entering DNA ends and sliding on unobstructed duplex DNA.
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Affiliation(s)
- H Wang
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey/Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Nakopoulou L, Zervas A, Lazaris AC, Constantinides C, Stravodimos C, Davaris P, Dimopoulos C. Predictive value of topoisomerase II alpha immunostaining in urothelial bladder carcinoma. J Clin Pathol 2001; 54:309-13. [PMID: 11304849 PMCID: PMC1731402 DOI: 10.1136/jcp.54.4.309] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
AIMS The nuclear enzyme DNA topoisomerase II has been shown to be required for chromatin condensation and chromosomal segregation during mitosis; its isoform topo II alpha is linked with active cell proliferation in mammalian cells. The aim of this study was to examine the relation of the expression of topo II alpha to the biological behaviour of conventional urinary bladder cancer. METHODS Formalin fixed, paraffin wax embedded tissue from 94 specimens of bladder urothelial cancer were immuno-histochemically stained for topo II alpha. For each case, a topo II alpha index was determined. A similar index had been determined for Ki-67, a known cell proliferation marker. Each case had also been graded, staged, and evaluated for DNA ploidy as well as for p53 and bcl-2 immunoreactivity. RESULTS Raised topo II alpha expression (in > or = 10% of malignant nuclei) correlated with two adverse prognosticators--high grade (p = 0.027) and invasion of the muscularis propria (p = 0.013), but with no other evaluated parameter. By multivariate survival analysis using Cox's proportional hazard model, high expression of topo II alpha was found to be predictive for worse survival (p = 0.0047). Patients' age, tumour stage, and grade were also retained as independent prognostic factors (p = 0.0349, p = 0.00005, and p = 0.0130, respectively). The negative influence of increased topo II alpha immunopositivity on patients' survival was also seen in the subgroup of patients with non-muscle invasive carcinomas (p = 0.0004), in patients with a bcl-2 negative phenotype (p = 0.0330), and in those with low Ki-67 indices (p = 0.0341). CONCLUSIONS Because topo II alpha and Ki-67 failed to demonstrate a significant interrelation, they appear to be different molecules that both function at separate phases in the complex process of cellular proliferation. The assessment of increased topo II alpha immunoreactivity in specimens from urothelial carcinomas might help to select patients (particularly among those with superficial tumours) in the worse prognostic categories for new therapeutic strategies.
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Affiliation(s)
- L Nakopoulou
- Department of Pathology, Athens National University School of Medicine, 75 Mikras Asias Str., Goudi, GR-115 27 Athens, Greece.
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Arlt A, Vorndamm J, Breitenbroich M, Fölsch UR, Kalthoff H, Schmidt WE, Schäfer H. Inhibition of NF-kappaB sensitizes human pancreatic carcinoma cells to apoptosis induced by etoposide (VP16) or doxorubicin. Oncogene 2001; 20:859-68. [PMID: 11314019 DOI: 10.1038/sj.onc.1204168] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2000] [Revised: 12/04/2000] [Accepted: 12/12/2000] [Indexed: 11/08/2022]
Abstract
The transcription factor NF-kappaB has anti-apoptotic properties and may confer chemoresistance to cancer cells. Here, we describe human pancreatic carcinoma cell lines that differ in the responsiveness to the topoisomerase-2 inhibitors VP16 (20 microM) and doxorubicin (0.3 microM): Highly sensitive T3M4 [corrected] and PT45-P1 cells, and Capan-1 and A818-4 cells that were almost resistant to both anti cancer drugs. VP16, but not doxorubicin, transiently induced NF-kappaB activity in all cell lines, whereas basal NF-kappaB binding was nearly undetectable in T3M4 [corrected] and PT45-P1 cells, but rather high in Capan-1 and A818-4 cells, as demonstrated by gel-shift and luciferase assays. Treatment with various NF-kappaB inhibitors (Gliotoxin, MG132 and Sulfasalazine), or transfection with the IkappaBalpha super-repressor, strongly enhanced the apoptotic effects of VP16 or doxorubicin on resistant Capan-1 and 818-4 cells. Our results indicate that under certain conditions the resistance of pancreatic carcinoma cells to chemotherapy is due to their constitutive NF-kappaB activity rather than the transient induction of NF-kappaB by some anti-cancer drugs. Blockade of basal NF-kappaB activity by well established drugs efficiently reduces chemoresistance of pancreatic cancer cells and offers the potential for improved therapeutic strategies.
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Affiliation(s)
- A Arlt
- Laboratory of Molecular Gastroenterology, 1st Department of Medicine, University of Kiel, Germany
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Abstract
Topoisomerase I-mediated DNA damage induced by camptothecin has been shown to induce rapid small ubiquitin-related modifier (SUMO)-1 conjugation to topoisomerase I. In the current study, we show that topoisomerase II-mediated DNA damage induced by teniposide (VM-26) results in the formation of high molecular weight conjugates of both topoisomerase IIalpha and IIbeta isozymes in HeLa cells. Immunological characterization of these conjugates suggests that both topoisomerase IIalpha and IIbeta isozymes are conjugated to SUMO-1. The involvement of SUMO-1/UBC9 in the modification of topoisomerase II isozymes is also supported by the demonstration of physical interaction between topoisomerase II and SUMO-1/UBC9. Surprisingly, ICRF-193, which does not induce topoisomerase II-mediated DNA damage but traps topoisomerase II into a circular clamp conformation, is also shown to induce similar SUMO-1 conjugation to topoisomerase II isozymes. In addition, we show that both oxidative and heat shock stresses, which can cause protein damage, rapidly increase nuclear SUMO-1 conjugates. These studies raise the question on whether SUMO-1 conjugation to topoisomerases is an indirect result of a DNA damage response or a direct result because of protein conformational changes.
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Affiliation(s)
- Y Mao
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Okada Y, Ito Y, Kikuchi A, Nimura Y, Yoshida S, Suzuki M. Assignment of functional amino acids around the active site of human DNA topoisomerase IIalpha. J Biol Chem 2000; 275:24630-8. [PMID: 10807924 DOI: 10.1074/jbc.m003243200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An expression library for active site mutants of human topoisomerase IIalpha (TOP2alpha) was constructed by replacing the sequence encoding residues 793-808 with a randomized oligonucleotide cassette. This plasmid library was transformed into a temperature-sensitive yeast strain (top2-1), and viable transformants were selected at the restrictive temperature. Among the active TOP2alpha mutants, no substitution was allowed at Tyr(805), the 5' anchor of the cleaved DNA, and only conservative substitutions were allowed at Leu(794), Asp(797), Ala(801), and Arg(804). Thus, these 5 residues are critical for human TOP2alpha activity, and the remaining mutagenized residues are less critical for function. Using the x-ray crystal structure of yeast TOP2 as a structural model, it can be deduced that these 5 functionally important residues lie in a plane. One of the possible functions of this plane may be that it interacts with the DNA substrate upon catalysis. The side chains of Ser(803) and Lys(798), which confer drug resistance, lie adjacent to this plane.
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Affiliation(s)
- Y Okada
- First Department of Surgery and the Laboratories of Cancer Cell Biology and Medical Mycology, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya, 466-8550, Japan
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Abstract
The 10th Conference on DNA Topoisomerases in Therapy 6-8 October 1999 in Amsterdam, The Netherlands) covered basic research on DNA topoisomerases and aspects of topoisomerase-directed therapy. The understanding of basic aspects of enzyme functions and structures was discussed throughout the meeting, as this knowledge is fundamental to further developments of new and more effective therapeutic approaches. Several new crystal structures were presented, and implications for function and interaction with DNA and drugs were discussed. Knock-out mice for various topoisomerase genes have been produced and genes have been shown to differ in importance for development and survival. The interaction of topoisomerases with other proteins involved in DNA metabolism, chromosome stability and physiology were discussed. The main focus for cancer therapy was on camptothecins (CPT) and related compounds stabilizing covalent DNA-intermediates of topoisomerase I. Reports on recent clinical trials of first-generation, water-soluble CPT-analogs (topotecan and irinotecan) confirmed earlier findings of activity in several solid tumors and hematological malignancies. Improvements in efficacy and toxicity profiles are being sought in orally absorbable compounds and other drug formulations (e.g. in liposomes). Several new CPT-analogs at preclinical stages of development might also provide a greater stability of the lactone ring, higher DNA-binding affinity, and improved water solubility. New drugs have also been developed from a number of new non-CPT compounds, which inhibit the activity of DNA-topoisomerases but do not stabilize the DNA-linked form of the enzymes. Another focus of the meeting was on therapeutic targeting of microbial DNA topoisomerases. The antibiotic potential of the quinolones has been extended to gram-positive pathogens, particularly Streptococcus pneumoniae. The cloning and biochemical characterization of the DNA-topoisomerases of eukaryotic parasites such as Plasmodium falciparum or Candida albicans have been completed and the search for specific inhibitors targeting these enzymes is under way. Copyright 1999 Harcourt Publishers Ltd.
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Affiliation(s)
- Giuseppe Giaccone
- Medical Oncology, Academic Hospital Vrije Universiteit, Amsterdam, The Netherlands
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