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Raab CA, Raab M, Becker S, Strebhardt K. Non-mitotic functions of polo-like kinases in cancer cells. Biochim Biophys Acta Rev Cancer 2021; 1875:188467. [PMID: 33171265 DOI: 10.1016/j.bbcan.2020.188467] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 11/03/2020] [Accepted: 11/03/2020] [Indexed: 12/12/2022]
Abstract
Inhibitors of mitotic protein kinases are currently being developed as non-neurotoxic alternatives of microtubule-targeting agents (taxanes, vinca alkaloids) which provide a substantial survival benefit for patients afflicted with different types of solid tumors. Among the mitotic kinases, the cyclin-dependent kinases, the Aurora kinases, the kinesin spindle protein and Polo-like kinases (PLKs) have emerged as attractive targets of cancer therapeutics. The functions of mammalian PLK1-5 are traditionally linked to the regulation of the cell cycle and to the stress response. Especially the key role of PLK1 and PLK4 in cellular growth and proliferation, their overexpression in multiple types of human cancer and their druggability, make them appealing targets for cancer therapy. Inhibitors for PLK1 and PLK4 are currently being tested in multiple cancer trials. The clinical success of microtubule-targeting agents is attributed not solely to the induction of a mitotic arrest in cancer cells, but also to non-mitotic effects like targeting intracellular trafficking on microtubules. This raises the question whether new cancer targets like PLK1 and PLK4 regulate critical non-mitotic functions in tumor cells. In this article we summarize the important roles of PLK1-5 for the regulation of non-mitotic signaling. Due to these functions it is conceivable that inhibitors for PLK1 or PLK4 can target interphase cells, which underscores their attractive potential as cancer drug targets. Moreover, we also describe the contribution of the tumor-suppressors PLK2, PLK3 and PLK5 to cancer cell signaling outside of mitosis. These observations highlight the urgent need to develop highly specific ATP-competitive inhibitors for PLK4 and for PLK1 like the 3rd generation PLK-inhibitor Onvansertib to prevent the inhibition of tumor-suppressor PLKs in- and outside of mitosis. The remarkable feature of PLKs to encompass a unique druggable domain, the polo-box-domain (PBD) that can be found only in PLKs offers the opportunity for the development of inhibitors that target PLKs exclusively. Beyond the development of mono-specific ATP-competitive PLK inhibitors, the PBD as drug target will support the design of new drugs that eradicate cancer cells based on the mitotic and non-mitotic function of PLK1 and PLK4.
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Affiliation(s)
| | - Monika Raab
- Department of Gynecology, Goethe-University, Frankfurt, Germany
| | - Sven Becker
- Department of Gynecology, Goethe-University, Frankfurt, Germany
| | - Klaus Strebhardt
- Department of Gynecology, Goethe-University, Frankfurt, Germany; German Cancer Consortium (DKTK), German Cancer Research Center, Partner Site Frankfurt am Main, Frankfurt, Germany.
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2
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Abdelfatah S, Fleischer E, Klinger A, Wong VKW, Efferth T. Identification of inhibitors of the polo-box domain of polo-like kinase 1 from natural and semisynthetic compounds. Invest New Drugs 2020; 38:1-9. [PMID: 30877426 DOI: 10.1007/s10637-019-00752-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 02/25/2019] [Indexed: 12/30/2022]
Abstract
PLK1 has an important role in the regulation of cell cycle and represents an important target for cancer treatment. This enzyme belongs to the Polo-like kinases family, which is characterized by a regulatory domain named Polo-box domain (PBD). Rather than regular kinase inhibitors, this domain provides high selectivity to PLK1. Here, we report on four novel PLK1 PBD inhibitors identified by cytotoxicity screening and fluorescence polarization assay of a chemical library of natural and semisynthetic compounds. These compounds revealed two- to three-fold higher selectivity to the PDB of PLK1 than to those of the related family members, PLK2 and PLK3. These four substances inhibited tumor cell growth of sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. The tested compounds increased the apoptotic cell fraction, which indicates apoptosis as a major mechanism of cell death. Cell cycle analysis showed compound (5) arrested the cell cycle of CCRF-CEM cells in the G2/M phase, while the other three molecules ((compound (3), compound (4), and compound (6)) exerted pronounced cytotoxicity with an increase of cells in the sub-G1 population. Molecular docking was performed for the understanding of ligand-protein interaction, the tested candidates showed strong binding affinity to PLK1 PBD. In conclusion, we identified four new chemical scaffolds that may serve as lead compounds for the development of selective PLK1 inhibitors in the future.
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Affiliation(s)
- Sara Abdelfatah
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, 55128, Mainz, Germany
| | | | | | - Vincent Kam Wai Wong
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau, China
| | - Thomas Efferth
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, 55128, Mainz, Germany.
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3
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Abdelfatah S, Berg A, Huang Q, Yang LJ, Hamdoun S, Klinger A, Greten HJ, Fleischer E, Berg T, Wong VK, Efferth T. MCC1019, a selective inhibitor of the Polo-box domain of Polo-like kinase 1 as novel, potent anticancer candidate. Acta Pharm Sin B 2019; 9:1021-1034. [PMID: 31649851 PMCID: PMC6804483 DOI: 10.1016/j.apsb.2019.02.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 12/20/2018] [Accepted: 12/22/2018] [Indexed: 01/01/2023] Open
Abstract
Polo-like kinase (PLK1) has been identified as a potential target for cancer treatment. Although a number of small molecules have been investigated as PLK1 inhibitors, many of which showed limited selectivity. PLK1 harbors a regulatory domain, the Polo box domain (PBD), which has a key regulatory function for kinase activity and substrate recognition. We report on 3-bromomethyl-benzofuran-2-carboxylic acid ethyl ester (designated: MCC1019) as selective PLK1 inhibitor targeting PLK1 PBD. Cytotoxicity and fluorescence polarization-based screening were applied to a library of 1162 drug-like compounds to identify potential inhibitors of PLK1 PBD. The activity of compound MC1019 against the PLK1 PBD was confirmed using fluorescence polarization and microscale thermophoresis. This compound exerted specificity towards PLK1 over PLK2 and PLK3. MCC1019 showed cytotoxic activity in a panel of different cancer cell lines. Mechanistic investigations in A549 lung adenocarcinoma cells revealed that MCC1019 induced cell growth inhibition through inactivation of AKT signaling pathway, it also induced prolonged mitotic arrest—a phenomenon known as mitotic catastrophe, which is followed by immediate cell death via apoptosis and necroptosis. MCC1019 significantly inhibited tumor growth in vivo in a murine lung cancer model without affecting body weight or vital organ size, and reduced the growth of metastatic lesions in the lung. We propose MCC1019 as promising anti-cancer drug candidate.
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Key Words
- 3-MA, 3-methyladenine
- ABC, avidin-biotin complex
- APC/C, anaphase-promoting complex/cyclosome
- BUBR1, budding uninhibited by benzimidazole-related 1
- CDC2, cell division cycle protein 2 homolog
- CDC25, cell division cycle 25
- CDK, cyclin-dependent kinase
- Cell cycle
- DAPI, 4′,6-diamidino-2-phenylindole
- DAPKs, death-associated protein kinase
- FBS, fetal bovine serum
- FOXO, forkhead box O
- HIF-1α, hypoxia-inducible factor 1 α
- IC50, 50% inhibition concentration
- IHC, immunohistochemistry
- Kd, the dissociation constant
- LC3, light chain 3
- MFP, M phase promoting factor
- MST, microscale thermophoresis
- MTD, maximal tolerance dose
- Mono-targeted therapy
- Nec-1, necrostatin 1
- Necroptosis
- PARP-1, poly(ADP-ribose) polymerase-1
- PBD, Polo box domain
- PDB, Protein Data Bank
- PI, propidium iodide
- PLK1
- PLK1, Polo-like kinase
- Polo box domain
- Polo-like kinase
- SAC, spindle assembly checkpoint
- Spindle damage
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Affiliation(s)
- Sara Abdelfatah
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz 55128, Germany
| | - Angela Berg
- Leipzig University, Institute of Organic Chemistry, Leipzig 04103, Germany
| | - Qi Huang
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau, China
| | - Li Jun Yang
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau, China
| | - Sami Hamdoun
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz 55128, Germany
| | | | - Henry J. Greten
- Abel Salazar Institute of Biomedical Sciences, University of Porto, Porto 4099-003, Portugal
| | | | - Thorsten Berg
- Leipzig University, Institute of Organic Chemistry, Leipzig 04103, Germany
| | - Vincent K.W. Wong
- State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, Macau, China
| | - Thomas Efferth
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz 55128, Germany
- Corresponding author. Tel.: +49 6131 3925751; fax: +49 6131 23752.
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4
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Abdelfatah S, Berg A, Böckers M, Efferth T. A selective inhibitor of the Polo-box domain of Polo-like kinase 1 identified by virtual screening. J Adv Res 2018; 16:145-156. [PMID: 30899597 PMCID: PMC6412170 DOI: 10.1016/j.jare.2018.10.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 10/27/2018] [Accepted: 10/28/2018] [Indexed: 12/04/2022] Open
Abstract
We were able to identify a novel anticancer molecule that targets PLK1. The compound shows good activity in leukaemia-sensitive and -resistant cells. Compound (1) induces mitotic arrest and interferes with normal spindle formation. We showed the importance of virtual screening for facilitating drug discovery. Compound (1) is a good scaffold for further chemical development.
Polo-like kinase 1 (PLK1), a member of the Polo-like kinase family, plays an important regulatory role in mitosis and cell cycle progression. PLK1 overexpression is correlated with tumourigenesis and poor prognosis in cancer patients. Therefore, the identification of novel compounds that inhibit PLK1 would provide attractive therapeutic approaches. Although some PLK1 kinase inhibitors have been developed, their application has been limited by off-target effects. PLK1 contains a regulatory domain named the Polo-box domain (PBD), which is characteristic only for the Polo-like kinase family. This domain represents an alternative therapeutic target with higher selectivity for PLK1. In this study, we applied in silico virtual drug screening, fluorescence polarization and microscale thermophoresis to identify new scaffolds targeting the PBD of PLK1. One compound, 3-{[(1R,9S)-3-(naphthalen-2-yl)-6-oxo-7,11-diazatricyclo[7.3.1.02,7]trideca-2,4-dien-11-yl]methyl}benzonitrile (designated compound (1)), out of a total of 30,793 natural product derivatives, inhibited the PLK1 PBD with high selectivity (IC50: 17.9 ± 0.5 µM). This compound inhibited the growth of cultured leukaemia cells (CCRF-CEM and CEM/ADR5000) and arrested the cell cycle in the G2/M phase, which is characteristic for PLK1 inhibitors. Immunofluorescence analyses showed that treatment with compound (1) disrupted spindle formation due to the aberrant localization of PLK1 during the mitotic process, leading to G2/M arrest and ultimately cell death. In conclusion, compound (1) is a selective PLK1 inhibitor that inhibits cancer cell growth. It represents a chemical scaffold for the future synthesis of new selective PLK1 inhibitors for cancer therapy.
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Affiliation(s)
- Sara Abdelfatah
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz 55128, Germany
| | - Angela Berg
- Leipzig University, Institute of Organic Chemistry Johannisallee 29, 04103 Leipzig, Germany
| | - Madeleine Böckers
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz 55128, Germany
| | - Thomas Efferth
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz 55128, Germany
- Corresponding author.
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Leroux AE, Schulze JO, Biondi RM. AGC kinases, mechanisms of regulation and innovative drug development. Semin Cancer Biol 2017; 48:1-17. [PMID: 28591657 DOI: 10.1016/j.semcancer.2017.05.011] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/16/2017] [Accepted: 05/31/2017] [Indexed: 12/22/2022]
Abstract
The group of AGC kinases consists of 63 evolutionarily related serine/threonine protein kinases comprising PDK1, PKB/Akt, SGK, PKC, PRK/PKN, MSK, RSK, S6K, PKA, PKG, DMPK, MRCK, ROCK, NDR, LATS, CRIK, MAST, GRK, Sgk494, and YANK, while two other families, Aurora and PLK, are the most closely related to the group. Eight of these families are physiologically activated downstream of growth factor signalling, while other AGC kinases are downstream effectors of a wide range of signals. The different AGC kinase families share aspects of their mechanisms of inhibition and activation. In the present review, we update the knowledge of the mechanisms of regulation of different AGC kinases. The conformation of the catalytic domain of many AGC kinases is regulated allosterically through the modulation of the conformation of a regulatory site on the small lobe of the kinase domain, the PIF-pocket. The PIF-pocket acts like an ON-OFF switch in AGC kinases with different modes of regulation, i.e. PDK1, PKB/Akt, LATS and Aurora kinases. In this review, we make emphasis on how the knowledge of the molecular mechanisms of regulation can guide the discovery and development of small allosteric modulators. Molecular probes stabilizing the PIF-pocket in the active conformation are activators, while compounds stabilizing the disrupted site are allosteric inhibitors. One challenge for the rational development of allosteric modulators is the lack of complete structural information of the inhibited forms of full-length AGC kinases. On the other hand, we suggest that the available information derived from molecular biology and biochemical studies can already guide screening strategies for the identification of innovative mode of action molecular probes and the development of selective allosteric drugs for the treatment of human diseases.
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Affiliation(s)
- Alejandro E Leroux
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina.
| | - Jörg O Schulze
- Research Group PhosphoSites, Medizinische Klinik 1, Universitätsklinikum Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany.
| | - Ricardo M Biondi
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina; Research Group PhosphoSites, Medizinische Klinik 1, Universitätsklinikum Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany, German Cancer Research Center (DKFZ), Heidelberg, Germany.
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6
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Helmke C, Raab M, Rödel F, Matthess Y, Oellerich T, Mandal R, Sanhaji M, Urlaub H, Rödel C, Becker S, Strebhardt K. Ligand stimulation of CD95 induces activation of Plk3 followed by phosphorylation of caspase-8. Cell Res 2016; 26:914-34. [PMID: 27325299 PMCID: PMC4973331 DOI: 10.1038/cr.2016.78] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 02/25/2016] [Accepted: 04/18/2016] [Indexed: 02/07/2023] Open
Abstract
Upon interaction of the CD95 receptor with its ligand, sequential association of the adaptor molecule FADD (MORT1), pro-forms of caspases-8/10, and the caspase-8/10 regulator c-FLIP leads to the formation of a death-inducing signaling complex. Here, we identify polo-like kinase (Plk) 3 as a new interaction partner of the death receptor CD95. The enzymatic activity of Plk3 increases following interaction of the CD95 receptor with its ligand. Knockout (KO) or knockdown of caspase-8, CD95 or FADD prevents activation of Plk3 upon CD95 stimulation, suggesting a requirement of a functional DISC for Plk3 activation. Furthermore, we identify caspase-8 as a new substrate for Plk3. Phosphorylation occurs on T273 and results in stimulation of caspase-8 proapoptotic function. Stimulation of CD95 in cells expressing a non-phosphorylatable caspase-8-T273A mutant in a rescue experiment or in Plk3-KO cells generated by CRISPR/Cas9 reduces the processing of caspase-8 prominently. Low T273 phosphorylation correlates significantly with low Plk3 expression in a cohort of 95 anal tumor patients. Our data suggest a novel mechanism of kinase activation within the Plk family and propose a new model for the stimulation of the extrinsic death pathway in tumors with high Plk3 expression.
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Affiliation(s)
- Christina Helmke
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany
| | - Monika Raab
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany
| | - Franz Rödel
- Department of Radiotherapy and Oncology, Goethe University, 60590 Frankfurt, Germany.,German Cancer Consortium (DKTK)/German Cancer Research Center, 69120 Heidelberg, Germany
| | - Yves Matthess
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany.,German Cancer Consortium (DKTK)/German Cancer Research Center, 69120 Heidelberg, Germany
| | - Thomas Oellerich
- German Cancer Consortium (DKTK)/German Cancer Research Center, 69120 Heidelberg, Germany.,Department of Medicine II, Hematology/Oncology, Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
| | - Ranadip Mandal
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany.,German Cancer Consortium (DKTK)/German Cancer Research Center, 69120 Heidelberg, Germany
| | - Mourad Sanhaji
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.,Bioanalytics, Institute for Clinical Chemistry, University Medical Center Göttingen, Robert-Koch-Straße 40, 37075 Göttingen, Germany
| | - Claus Rödel
- Department of Radiotherapy and Oncology, Goethe University, 60590 Frankfurt, Germany.,German Cancer Consortium (DKTK)/German Cancer Research Center, 69120 Heidelberg, Germany
| | - Sven Becker
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany
| | - Klaus Strebhardt
- Department of Gynecology, Goethe University, 60590 Frankfurt, Germany.,German Cancer Consortium (DKTK)/German Cancer Research Center, 69120 Heidelberg, Germany
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7
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Scharow A, Knappe D, Reindl W, Hoffmann R, Berg T. Development of Bifunctional Inhibitors of Polo-Like Kinase 1 with Low-Nanomolar Activities Against the Polo-Box Domain. Chembiochem 2016; 17:759-67. [PMID: 26634982 DOI: 10.1002/cbic.201500535] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Indexed: 01/10/2023]
Abstract
Polo-like kinase 1 (Plk1), a validated cancer target, harbors a protein-protein interaction domain referred to as the polo-box domain (PBD), in addition to its enzymatic domain. Although functional inhibition either of the enzymatic domain or of the PBD has been shown to inhibit Plk1, so far there have been no reports of bifunctional agents with the potential to target both protein domains. Here we report the development of Plk1 inhibitors that incorporate both an ATP-competitive ligand of the enzymatic domain, derived from BI 2536, and a functional inhibitor of the PBD, based either on the small molecule poloxin-2 or on a PBD-binding peptide. Although these bifunctional agents do not seem to bind both protein domains simultaneously, the most potent compound displays low-nanomolar activity against the Plk1 PBD, with excellent selectivity over the PBDs of Plk2 and Plk3. Our data provide insights into challenges and opportunities relating to the optimization of Plk1 PBD ligands as potent Plk1 inhibitors.
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Affiliation(s)
- Andrej Scharow
- Leipzig University, Institute of Organic Chemistry, Johannisallee 29, 04103, Leipzig, Germany
| | - Daniel Knappe
- Leipzig University, Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine (BBZ), Deutscher Platz 5, 04103, Leipzig, Germany
| | - Wolfgang Reindl
- Max Planck Institute of Biochemistry, Department of Molecular Biology, Am Klopferspitz 18, 82152, Martinsried, Germany
- Evotec AG, Manfred Eigen Campus, Essener Bogen 7, 22419, Hamburg, Germany
| | - Ralf Hoffmann
- Leipzig University, Institute of Bioanalytical Chemistry, Center for Biotechnology and Biomedicine (BBZ), Deutscher Platz 5, 04103, Leipzig, Germany
| | - Thorsten Berg
- Leipzig University, Institute of Organic Chemistry, Johannisallee 29, 04103, Leipzig, Germany.
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8
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Ferrarotto R, Goonatilake R, Yoo SY, Tong P, Giri U, Peng S, Minna J, Girard L, Wang Y, Wang L, Li L, Diao L, Peng DH, Gibbons DL, Glisson BS, Heymach JV, Wang J, Byers LA, Johnson FM. Epithelial-Mesenchymal Transition Predicts Polo-Like Kinase 1 Inhibitor-Mediated Apoptosis in Non-Small Cell Lung Cancer. Clin Cancer Res 2016; 22:1674-1686. [PMID: 26597303 PMCID: PMC4818738 DOI: 10.1158/1078-0432.ccr-14-2890] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 11/01/2015] [Indexed: 12/31/2022]
Abstract
PURPOSE To identify new therapeutic targets for non-small cell lung cancer (NSCLC), we systematically searched two cancer cell line databases for sensitivity data on a broad range of drugs. We identified polo-like kinase 1 (PLK1) as the most promising target for further investigation based on a subset of sensitive NSCLC cell lines and inhibitors that were in advanced clinical development. EXPERIMENTAL DESIGN To identify potential biomarkers of response of NSCLC to PLK1 inhibition and mechanisms of PLK1 inhibitor-induced apoptosis, integrated analysis of gene and protein expression, gene mutations, and drug sensitivity was performed using three PLK1 inhibitors (volasertib, BI2536, and GSK461364) with a large panel of NSCLC cell lines. RESULTS The NSCLC cell lines had different sensitivities to PLK1 inhibition, with a minority demonstrating sensitivity to all three inhibitors. PLK1 inhibition led to G2-M arrest, but only treatment-sensitive cell lines underwent substantial apoptosis following PLK1 inhibition. NSCLC lines with high epithelial-mesenchymal transition (EMT) gene signature scores (mesenchymal cell lines) were more sensitive to PLK1 inhibition than epithelial lines (P< 0.02). Likewise, proteomic profiling demonstrated that E-cadherin expression was higher in the resistant cell lines than in the sensitive ones (P< 0.01). Induction of an epithelial phenotype by expression of the miRNA miR-200 increased cellular resistance to PLK1 inhibition. Also, KRAS mutation and alterations in the tight-junction, ErbB, and Rho signaling pathways correlated with drug response of NSCLC. CONCLUSIONS In this first reported large-scale integrated analysis of PLK1 inhibitor sensitivity, we demonstrated that EMT leads to PLK1 inhibition sensitivity of NSCLC cells. Our findings have important clinical implications for mesenchymal NSCLC, a significant subtype of the disease that is associated with resistance to currently approved targeted therapies.
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Affiliation(s)
- Renata Ferrarotto
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Ruchitha Goonatilake
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
| | - Suk Young Yoo
- Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Pan Tong
- Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Uma Giri
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Shaohua Peng
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - John Minna
- Hamon Cancer Center for Therapeutic Oncology Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Luc Girard
- Hamon Cancer Center for Therapeutic Oncology Research, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - Yuehong Wang
- Department of Respiratory Medicine, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Liguang Wang
- Shandong Provincial Hospital Affiliated to Shandong University, Shandong University, China
| | - Lerong Li
- Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Lixia Diao
- Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - David H. Peng
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
| | - Don L. Gibbons
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Bonnie S. Glisson
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - John V. Heymach
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
| | - Jing Wang
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
- Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Lauren A. Byers
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
| | - Faye M. Johnson
- Departments of Thoracic/Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas
- The University of Texas Graduate School of Biomedical Sciences, Houston, Texas
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9
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Helmke C, Becker S, Strebhardt K. The role of Plk3 in oncogenesis. Oncogene 2016; 35:135-47. [PMID: 25915845 DOI: 10.1038/onc.2015.105] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 02/02/2015] [Accepted: 02/02/2015] [Indexed: 01/08/2023]
Abstract
The polo-like kinases (Plks) encompass a family of five serine/threonine protein kinases that play essential roles in many cellular processes involved in the control of the cell cycle, including entry into mitosis, DNA replication and the response to different types of stress. Plk1, which has been validated as a cancer target, came into the focus of many pharmaceutical companies for the development of small-molecule inhibitors as anticancer agents. Recently, FDA (Food and Drug Administration) has granted a breakthrough therapy designation to the Plk inhibitor BI 6727 (volasertib), which provided a survival benefit for patients suffering from acute myeloid leukemia. However, the various ATP-competitive inhibitors of Plk1 that are currently in clinical development also inhibit the activities of Plk2 and Plk3, which are considered as tumor suppressors. Plk3 contributes to the control and progression of the cell cycle while acting as a mediator of apoptosis and various types of cellular stress. The aberrant expression of Plk3 was found in different types of tumors. Recent progress has improved our understanding of Plk3 in regulating stress signaling and tumorigenesis. When using ATP-competitive Plk1 inhibitors, the biological roles of Plk1-related family members like Plk3 in cancer cells need to be considered carefully to improve treatment strategies against cancer.
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Affiliation(s)
- C Helmke
- Department of Obstetrics and Gynecology, School of Medicine, J.W. Goethe University, Frankfurt, Germany
| | - S Becker
- Department of Obstetrics and Gynecology, School of Medicine, J.W. Goethe University, Frankfurt, Germany
| | - K Strebhardt
- Department of Obstetrics and Gynecology, School of Medicine, J.W. Goethe University, Frankfurt, Germany
- German Cancer Consortium (DKTK), Heidelberg, Germany
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10
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Lee KS, Burke TR, Park JE, Bang JK, Lee E. Recent Advances and New Strategies in Targeting Plk1 for Anticancer Therapy. Trends Pharmacol Sci 2015; 36:858-877. [PMID: 26478211 PMCID: PMC4684765 DOI: 10.1016/j.tips.2015.08.013] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 08/21/2015] [Accepted: 08/21/2015] [Indexed: 12/11/2022]
Abstract
Polo-like kinase 1 (Plk1) plays key roles in regulating mitotic processes that are crucial for cellular proliferation. Overexpression of Plk1 is tightly associated with the development of particular cancers in humans, and a large body of evidence suggests that Plk1 is an attractive target for anticancer therapeutic development. Drugs targeting Plk1 can potentially be directed at two distinct sites: the N-terminal catalytic kinase domain (KD), which phosphorylates substrates, and the C-terminal polo-box domain (PBD) which is essential for protein-protein interactions. In this review we summarize recent advances and new challenges in the development of Plk1 inhibitors targeting these two domains. We also discuss novel strategies for designing and developing next-generation inhibitors to effectively treat Plk1-associated human disorders.
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Affiliation(s)
- Kyung S Lee
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Terrence R Burke
- Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Jung-Eun Park
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jeong K Bang
- Division of Magnetic Resonance, Korea Basic Science Institute, 804-1, Yangcheong Ri, Ochang, Chungbuk, Cheongwon 363-883, Republic of Korea
| | - Eunhye Lee
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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11
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Scharow A, Raab M, Saxena K, Sreeramulu S, Kudlinzki D, Gande S, Dötsch C, Kurunci-Csacsko E, Klaeger S, Kuster B, Schwalbe H, Strebhardt K, Berg T. Optimized Plk1 PBD Inhibitors Based on Poloxin Induce Mitotic Arrest and Apoptosis in Tumor Cells. ACS Chem Biol 2015; 10:2570-9. [PMID: 26279064 DOI: 10.1021/acschembio.5b00565] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Polo-like kinase 1 (Plk1) is a central regulator of mitosis and has been validated as a target for antitumor therapy. The polo-box domain (PBD) of Plk1 regulates its kinase activity and mediates the subcellular localization of Plk1 and its interactions with a subset of its substrates. Functional inhibition of the Plk1 PBD by low-molecular weight inhibitors has been shown to represent a viable strategy by which to inhibit the enzyme, while avoiding selectivity issues caused by the conserved nature of the ATP binding site. Here, we report structure-activity relationships and mechanistic analysis for the first reported Plk1 PBD inhibitor, Poloxin. We present the identification of the optimized analog Poloxin-2, displaying significantly improved potency and selectivity over Poloxin. Poloxin-2 induces mitotic arrest and apoptosis in cultured human tumor cells at low micromolar concentrations, highlighting it as a valuable tool compound for exploring the function of the Plk1 PBD in living cells.
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Affiliation(s)
- Andrej Scharow
- Institute of Organic Chemistry, University of Leipzig , Johannisallee 29, 04103 Leipzig, Germany
| | - Monika Raab
- Johann Wolfgang Goethe-University , Medical School, Department of Gynecology and Obstetrics, Theodor-Stern-Kai 7-9, 60596 Frankfurt, Germany
| | - Krishna Saxena
- Johann Wolfgang Goethe-University Frankfurt , Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Sridhar Sreeramulu
- Johann Wolfgang Goethe-University Frankfurt , Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
| | - Denis Kudlinzki
- Johann Wolfgang Goethe-University Frankfurt , Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Santosh Gande
- Johann Wolfgang Goethe-University Frankfurt , Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Christina Dötsch
- Johann Wolfgang Goethe-University , Medical School, Department of Gynecology and Obstetrics, Theodor-Stern-Kai 7-9, 60596 Frankfurt, Germany
| | - Elisabeth Kurunci-Csacsko
- Johann Wolfgang Goethe-University , Medical School, Department of Gynecology and Obstetrics, Theodor-Stern-Kai 7-9, 60596 Frankfurt, Germany
| | - Susan Klaeger
- Technische Universität München , Emil Erlenmeyer Forum 5, 85354 Freising, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Bernhard Kuster
- Technische Universität München , Emil Erlenmeyer Forum 5, 85354 Freising, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Harald Schwalbe
- Johann Wolfgang Goethe-University Frankfurt , Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Klaus Strebhardt
- Johann Wolfgang Goethe-University , Medical School, Department of Gynecology and Obstetrics, Theodor-Stern-Kai 7-9, 60596 Frankfurt, Germany
- German Cancer Consortium (DKTK) , Heidelberg, Germany
| | - Thorsten Berg
- Institute of Organic Chemistry, University of Leipzig , Johannisallee 29, 04103 Leipzig, Germany
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12
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Aspinall CF, Zheleva D, Tighe A, Taylor SS. Mitotic entry: Non-genetic heterogeneity exposes the requirement for Plk1. Oncotarget 2015; 6:36472-88. [PMID: 26472023 PMCID: PMC4742190 DOI: 10.18632/oncotarget.5507] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 09/30/2015] [Indexed: 12/02/2022] Open
Abstract
The quest to develop novel antimitotic chemotherapy agents has led to the generation of several small molecule inhibitors targeting Plk1, a protein kinase required for multiple aspects of cell division. Previous studies have shown that upon exposure to Plk1 inhibitors, cells enter mitosis, delay briefly in prophase and then arrest in mitosis due to an inability to undergo centrosome separation. Here, we show that four different classes of Plk1 inhibitor block mitotic entry in several cancer cell lines and non-transformed RPE-1 cells. The proportion of cells that arrest in G2 is cell line and concentration dependent, and is subject to non-genetic heterogeneity. Following inhibitor washout, the G2 block is alleviated and cells enter mitosis but then fail to complete cell division indicating that most Plk1 inhibitors are not fully reversible. An exception is CYC140844; in contrast to five other inhibitors examined here, this novel Plk1 inhibitor is fully reversible. We discuss the implications for developing Plk1 inhibitors as chemotherapy agents and research tools.
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Affiliation(s)
- Claire F. Aspinall
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | | | - Anthony Tighe
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Stephen S. Taylor
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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13
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Park JE, Kim TS, Meng L, Bang JK, Kim BY, Lee KS. Putting a bit into the polo-box domain of polo-like kinase 1. J Anal Sci Technol 2015; 6:27. [PMID: 26500787 PMCID: PMC4610673 DOI: 10.1186/s40543-015-0069-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 09/27/2015] [Indexed: 01/11/2023] Open
Abstract
Polo-like kinase 1 (Plk1) plays key roles in regulating various mitotic processes that are critical for cellular proliferation. A growing body of evidence suggests that Plk1 overexpression is tightly associated with the development of human cancers. Interestingly, various types of cancer cells are shown to be addicted to a high level of Plk1, and the reversal of Plk1 addiction appears to be an effective strategy for selectively killing cancer cells, but not normal cells. Therefore, Plk1 is considered an attractive anticancer drug target. Over the years, a large number of inhibitors that target the catalytic activity of Plk1 have been developed. However, these inhibitors exhibit significant levels of cross-reactivity with related kinases, including Plk2 and Plk3. Consequently, as an alternative approach for developing anti-Plk1 therapeutics, substantial effort is under way to develop inhibitors that target the C-terminal protein–protein interaction domain of Plk1, called the polo-box domain (PBD). In this communication, I will discuss the pros and cons of targeting the PBD in comparison to those of targeting the ATP-binding site within the kinase domain.
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Affiliation(s)
- Jung-Eun Park
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Building 37, Room 3118, Bethesda, MD 20892 USA
| | - Tae-Sung Kim
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Building 37, Room 3118, Bethesda, MD 20892 USA
| | - Lingjun Meng
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Building 37, Room 3118, Bethesda, MD 20892 USA
| | - Jeong K Bang
- Division of Magnetic Resonance, Korea Basic Science Institute, 804-1, Yangcheong Ri, Ochang, 363-883 Chungbuk Republic of Korea
| | - Bo Y Kim
- World Class Institute, Korea Research Institute of Bioscience and Biotechnology, Ochang, 363-883 Republic of Korea
| | - Kyung S Lee
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 9000 Rockville Pike, Building 37, Room 3118, Bethesda, MD 20892 USA
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Trakala M, Partida D, Salazar-Roa M, Maroto M, Wachowicz P, de Cárcer G, Malumbres M. Activation of the endomitotic spindle assembly checkpoint and thrombocytopenia in Plk1-deficient mice. Blood 2015; 126:1707-14. [PMID: 26185128 DOI: 10.1182/blood-2015-03-634402] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 07/09/2015] [Indexed: 12/12/2022] Open
Abstract
Polyploidization in megakaryocytes is achieved by endomitosis, a specialized cell cycle in which DNA replication is followed by aberrant mitosis. Typical mitotic regulators such as Aurora kinases or Cdk1 are dispensable for megakaryocyte maturation, and inhibition of mitotic kinases may in fact promote megakaryocyte maturation. However, we show here that Polo-like kinase 1 (Plk1) is required for endomitosis, and ablation of the Plk1 gene in megakaryocytes results in defective polyploidization accompanied by mitotic arrest and cell death. Lack of Plk1 results in defective centrosome maturation and aberrant spindle pole formation, thus impairing the formation of multiple poles typically found in megakaryocytes. In these conditions, megakaryocytes arrest for a long time in mitosis and frequently die. Mitotic arrest in wild-type megakaryocytes treated with Plk1 inhibitors or Plk1-null cells is triggered by the spindle assembly checkpoint (SAC), and can be rescued in the presence of SAC inhibitors. These data suggest that, despite the dispensability of proper chromosome segregation in megakaryocytes, an endomitotic SAC is activated in these cells upon Plk1 inhibition. SAC activation results in defective maturation of megakaryocytes and cell death, thus raising a note of caution in the use of Plk1 inhibitors in therapeutic strategies based on polyploidization regulators.
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Affiliation(s)
- Marianna Trakala
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - David Partida
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - María Salazar-Roa
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - María Maroto
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - Paulina Wachowicz
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - Guillermo de Cárcer
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - Marcos Malumbres
- Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
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15
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Strebhardt K. Drugging Plk1: An attractive approach to inhibit androgen receptor signaling. Cell Cycle 2015; 14:2193-4. [PMID: 26030710 PMCID: PMC5242295 DOI: 10.1080/15384101.2015.1056611] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 05/19/2015] [Indexed: 01/17/2023] Open
Affiliation(s)
- Klaus Strebhardt
- Department of Gynecology; School of Medicine; Goethe University; Frankfurt, Germany
- German Cancer Consortium; Heidelberg, Germany
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16
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Abstract
Small molecule inhibitors of protein kinases are key tools for signal transduction research and represent a major class of targeted drugs. Recent developments in quantitative proteomics enable an unbiased view on kinase inhibitor selectivity and modes of action in the biological context. While chemical proteomics techniques utilizing quantitative mass spectrometry interrogate both target specificity and affinity in cellular extracts, proteome-wide phosphorylation analyses upon kinase inhibitor treatment identify signal transduction pathway and network regulation in an unbiased manner. Thus, critical information is provided to promote new insights into mechanisms of kinase signaling and their relevance for kinase inhibitor drug discovery.
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Affiliation(s)
- Henrik Daub
- Evotec (München) GmbH, Am Klopferspitz
19a, 82152 Martinsried, Germany
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17
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Strebhardt K, Becker S, Matthess Y. Thoughts on the current assessment of Polo-like kinase inhibitor drug discovery. Expert Opin Drug Discov 2015; 10:1-8. [PMID: 25263688 DOI: 10.1517/17460441.2015.962510] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The Polo-like kinase 1 (Plk1) plays a key role in regulating a broad spectrum of critical cell cycle events. Plk1 is a marker of cellular proliferation and has prognostic potential in different types of human tumors. In a series of preclinical studies, Plk1 has been validated as a cancer target. This prompted many pharmaceutical companies to develop small-molecule inhibitors targeting the classical ATP-binding site of Plk1 for anticancer drug development. Recently, FDA has granted a Breakthrough Therapy designation to the Plk inhibitor BI 6727 (volasertib), which provided a survival benefit for patients suffering from acute myeloid leukemia. Remarkably, a new generation of Plk1 inhibitors that target the second druggable domain of Plk1, the Polo-box domain, is currently being tested preclinically. Since various ATP-competitive compounds of Plk1 inhibit also the activities of Plk2 and Plk3, which act as tumor suppressors, the roles of closely related Plk-family members in cancer cells need to be considered carefully. In this article, the authors highlight recent insights into the biology of Plks in cancer cells and discuss the progress in the development of small-molecule Plk1 inhibitors. The authors believe that the greatest therapeutic benefit might come through leukemic cells that are in direct contact with the inhibitor in the blood stream. The identification of biomarkers and studies that document Plk activities in treated patients would also be beneficial to better understand the role of Plk inhibition in tumor development and anticancer therapy.
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Affiliation(s)
- Klaus Strebhardt
- J.W. Goethe University, School of Medicine, Department of Obstetrics and Gynecology , Theodor-Stern-Kai 7, 60590 Frankfurt , Germany +49 69 6301 6894 ; +49 69 6301 6364 ;
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