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Hamaguchi-Suzuki N, Adachi N, Moriya T, Yasuda S, Kawasaki M, Suzuki K, Ogasawara S, Anzai N, Senda T, Murata T. Cryo-EM structure of P-glycoprotein bound to triple elacridar inhibitor molecules. Biochem Biophys Res Commun 2024; 709:149855. [PMID: 38579618 DOI: 10.1016/j.bbrc.2024.149855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 03/27/2024] [Indexed: 04/07/2024]
Abstract
P-glycoprotein (P-gp) is an ATP-binding cassette transporter known for its roles in expelling xenobiotic compounds from cells and contributing to cellular drug resistance through multidrug efflux. This mechanism is particularly problematic in cancer cells, where it diminishes the therapeutic efficacy of anticancer drugs. P-gp inhibitors, such as elacridar, have been developed to circumvent the decrease in drug efficacy due to P-gp efflux. An earlier study reported the cryo-EM structure of human P-gp-Fab (MRK-16) complex bound by two elacridar molecules, at a resolution of 3.6 Å. In this study, we have obtained a higher resolution (2.5 Å) structure of the P-gp- Fab (UIC2) complex bound by three elacridar molecules. This finding, which exposes a larger space for compound-binding sites than previously acknowledged, has significant implications for the development of more selective inhibitors and enhances our understanding of the compound recognition mechanism of P-gp.
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Affiliation(s)
- Norie Hamaguchi-Suzuki
- Department of Pharmacology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo, Chiba, 260-8670, Japan; Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan
| | - Naruhiko Adachi
- Structure Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, 305-0801, Japan; Life Science Center for Survival Dynamics, Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan
| | - Toshio Moriya
- Structure Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, 305-0801, Japan
| | - Satoshi Yasuda
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan; Membrane Protein Research Center, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan
| | - Masato Kawasaki
- Structure Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, 305-0801, Japan
| | - Kano Suzuki
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan; Membrane Protein Research Center, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan
| | - Satoshi Ogasawara
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan; Membrane Protein Research Center, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan
| | - Naohiko Anzai
- Department of Pharmacology, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo, Chiba, 260-8670, Japan
| | - Toshiya Senda
- Structure Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1, Oho, Tsukuba, 305-0801, Japan
| | - Takeshi Murata
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan; Membrane Protein Research Center, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, 263-8522, Japan.
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Schulz JA, Hartz AMS, Bauer B. ABCB1 and ABCG2 Regulation at the Blood-Brain Barrier: Potential New Targets to Improve Brain Drug Delivery. Pharmacol Rev 2023; 75:815-853. [PMID: 36973040 PMCID: PMC10441638 DOI: 10.1124/pharmrev.120.000025] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 03/10/2023] [Accepted: 03/10/2023] [Indexed: 03/29/2023] Open
Abstract
The drug efflux transporters ABCB1 and ABCG2 at the blood-brain barrier limit the delivery of drugs into the brain. Strategies to overcome ABCB1/ABCG2 have been largely unsuccessful, which poses a tremendous clinical problem to successfully treat central nervous system (CNS) diseases. Understanding basic transporter biology, including intracellular regulation mechanisms that control these transporters, is critical to solving this clinical problem.In this comprehensive review, we summarize current knowledge on signaling pathways that regulate ABCB1/ABCG2 at the blood-brain barrier. In Section I, we give a historical overview on blood-brain barrier research and introduce the role that ABCB1 and ABCG2 play in this context. In Section II, we summarize the most important strategies that have been tested to overcome the ABCB1/ABCG2 efflux system at the blood-brain barrier. In Section III, the main component of this review, we provide detailed information on the signaling pathways that have been identified to control ABCB1/ABCG2 at the blood-brain barrier and their potential clinical relevance. This is followed by Section IV, where we explain the clinical implications of ABCB1/ABCG2 regulation in the context of CNS disease. Lastly, in Section V, we conclude by highlighting examples of how transporter regulation could be targeted for therapeutic purposes in the clinic. SIGNIFICANCE STATEMENT: The ABCB1/ABCG2 drug efflux system at the blood-brain barrier poses a significant problem to successful drug delivery to the brain. The article reviews signaling pathways that regulate blood-brain barrier ABCB1/ABCG2 and could potentially be targeted for therapeutic purposes.
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Affiliation(s)
- Julia A Schulz
- Department of Pharmaceutical Sciences, College of Pharmacy (J.A.S., B.B.), Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, College of Medicine (A.M.S.H.), University of Kentucky, Lexington, Kentucky
| | - Anika M S Hartz
- Department of Pharmaceutical Sciences, College of Pharmacy (J.A.S., B.B.), Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, College of Medicine (A.M.S.H.), University of Kentucky, Lexington, Kentucky
| | - Björn Bauer
- Department of Pharmaceutical Sciences, College of Pharmacy (J.A.S., B.B.), Sanders-Brown Center on Aging and Department of Pharmacology and Nutritional Sciences, College of Medicine (A.M.S.H.), University of Kentucky, Lexington, Kentucky
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Gutay-Tóth Z, Gellen G, Doan M, Eliason JF, Vincze J, Szente L, Fenyvesi F, Goda K, Vecsernyés M, Szabó G, Bacso Z. Cholesterol-Depletion-Induced Membrane Repair Carries a Raft Conformer of P-Glycoprotein to the Cell Surface, Indicating Enhanced Cholesterol Trafficking in MDR Cells, Which Makes Them Resistant to Cholesterol Modifications. Int J Mol Sci 2023; 24:12335. [PMID: 37569709 PMCID: PMC10419235 DOI: 10.3390/ijms241512335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Revised: 07/26/2023] [Accepted: 07/31/2023] [Indexed: 08/13/2023] Open
Abstract
The human P-glycoprotein (P-gp), a transporter responsible for multidrug resistance, is present in the plasma membrane's raft and non-raft domains. One specific conformation of P-gp that binds to the monoclonal antibody UIC2 is primarily associated with raft domains and displays heightened internalization in cells overexpressing P-gp, such as in NIH-3T3 MDR1 cells. Our primary objective was to investigate whether the trafficking of this particular P-gp conformer is dependent on cholesterol levels. Surprisingly, depleting cholesterol using cyclodextrin resulted in an unexpected increase in the proportion of raft-associated P-gp within the cell membrane, as determined by UIC2-reactive P-gp. This increase appears to be a compensatory response to cholesterol loss from the plasma membrane, whereby cholesterol-rich raft micro-domains are delivered to the cell surface through an augmented exocytosis process. Furthermore, this exocytotic event is found to be part of a complex trafficking mechanism involving lysosomal exocytosis, which contributes to membrane repair after cholesterol reduction induced by cyclodextrin treatment. Notably, cells overexpressing P-gp demonstrated higher total cellular cholesterol levels, an increased abundance of stable lysosomes, and more effective membrane repair following cholesterol modifications. These modifications encompassed exocytotic events that involved the transport of P-gp-carrying rafts. Importantly, the enhanced membrane repair capability resulted in a durable phenotype for MDR1 expressing cells, as evidenced by significantly improved viabilities of multidrug-resistant Pgp-overexpressing immortal NIH-3T3 MDR1 and MDCK-MDR1 cells compared to their parents when subjected to cholesterol alterations.
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Affiliation(s)
- Zsuzsanna Gutay-Tóth
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.G.-T.); (G.G.); (M.D.); (K.G.); (G.S.)
- Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, 4032 Debrecen, Hungary
| | - Gabriella Gellen
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.G.-T.); (G.G.); (M.D.); (K.G.); (G.S.)
- Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, 4032 Debrecen, Hungary
- MTA-ELTE Lendület Ion Mobility Mass Spectrometry Research Group, Department of Analytical Chemistry, Institute of Chemistry, ELTE Eötvös Loránd University, 1053 Budapest, Hungary
| | - Minh Doan
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.G.-T.); (G.G.); (M.D.); (K.G.); (G.S.)
| | - James F. Eliason
- Great Lakes Stem Cell Innovation Center, Detroit, MI 48202, USA;
| | - János Vincze
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary;
| | - Lajos Szente
- CycloLab Cyclodextrin Research & Development Laboratory, Ltd., 1097 Budapest, Hungary;
| | - Ferenc Fenyvesi
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Debrecen, 4032 Debrecen, Hungary; (F.F.); (M.V.)
| | - Katalin Goda
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.G.-T.); (G.G.); (M.D.); (K.G.); (G.S.)
| | - Miklós Vecsernyés
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Debrecen, 4032 Debrecen, Hungary; (F.F.); (M.V.)
| | - Gábor Szabó
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.G.-T.); (G.G.); (M.D.); (K.G.); (G.S.)
| | - Zsolt Bacso
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.G.-T.); (G.G.); (M.D.); (K.G.); (G.S.)
- Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, 4032 Debrecen, Hungary
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Debrecen, 4032 Debrecen, Hungary; (F.F.); (M.V.)
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Rahman H, Ware MJ, Sajid A, Lusvarghi S, Durell SR, Ambudkar SV. Residues from Homologous Transmembrane Helices 4 and 10 Are Critical for P-Glycoprotein (ABCB1)-Mediated Drug Transport. Cancers (Basel) 2023; 15:3459. [PMID: 37444569 DOI: 10.3390/cancers15133459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/27/2023] [Accepted: 06/27/2023] [Indexed: 07/15/2023] Open
Abstract
P-glycoprotein (P-gp, ABCB1) transports structurally dissimilar hydrophobic and amphipathic compounds, including anticancer drugs, thus contributing to multidrug-resistant cancer. Cryo-EM structures of human P-gp revealed that TMHs 4 and 10 contribute to the formation of the drug-binding cavity and undergo conformational changes during drug transport. To assess the role of the conformational changes in TMH4 and TMH10 during drug transport, we generated two mutants (TMH4-7A and TMH10-7A), each containing seven alanine substitutions. Analysis of the drug efflux function of these mutants using 15 fluorescent substrates revealed that most of the substrates were transported, indicating that even seven mutations in an individual helix have no significant effect on transport function. We then designed the TMH4,10-14A mutant combining seven mutations in both TMHs 4 and 10. Interestingly, when the TMH4,10-14A mutant was tested with 15 substrates, there was no efflux observed for fourteen. The basal ATPase activity of the TMH4,10-14A mutant, similar to that of the WT protein, was inhibited by zosuquidar but was not stimulated by verapamil or rhodamine 6G. Molecular dynamics simulations indicated that the mutations cause TMHs 4 and 10 to pack tighter to their proximal helices, reducing their independent mobility. In aggregate, our findings demonstrate the critical role of the residues of homologous TMHs 4 and 10 for substrate transport, consistent with conformational changes observed in the structure of P-gp.
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Affiliation(s)
- Hadiar Rahman
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA
| | - Mark J Ware
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA
| | - Andaleeb Sajid
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA
| | - Sabrina Lusvarghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA
| | - Stewart R Durell
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4256, USA
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Özvegy-Laczka C, Ungvári O, Bakos É. Fluorescence-based methods for studying activity and drug-drug interactions of hepatic solute carrier and ATP binding cassette proteins involved in ADME-Tox. Biochem Pharmacol 2023; 209:115448. [PMID: 36758706 DOI: 10.1016/j.bcp.2023.115448] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 01/31/2023] [Accepted: 02/01/2023] [Indexed: 02/11/2023]
Abstract
In humans, approximately 70% of drugs are eliminated through the liver. This process is governed by the concerted action of membrane transporters and metabolic enzymes. Transporters mediating hepatocellular uptake of drugs belong to the SLC (Solute carrier) superfamily of transporters. Drug efflux either toward the portal vein or into the bile is mainly mediated by active transporters of the ABC (ATP Binding Cassette) family. Alteration in the function and/or expression of liver transporters due to mutations, disease conditions, or co-administration of drugs or food components can result in altered pharmacokinetics. On the other hand, drugs or food components interacting with liver transporters may also interfere with liver function (e.g., bile acid homeostasis) and may even cause liver toxicity. Accordingly, certain transporters of the liver should be investigated already at an early stage of drug development. Most frequently radioactive probes are applied in these drug-transporter interaction tests. However, fluorescent probes are cost-effective and sensitive alternatives to radioligands, and are gaining wider application in drug-transporter interaction tests. In our review, we summarize our current understanding about hepatocyte ABC and SLC transporters affected by drug interactions. We provide an update of the available fluorescent and fluorogenic/activable probes applicable in in vitro or in vivo testing of these ABC and SLC transporters, including near-infrared transporter probes especially suitable for in vivo imaging. Furthermore, our review gives a comprehensive overview of the available fluorescence-based methods, not directly relying on the transport of the probe, suitable for the investigation of hepatic ABC or SLC-type drug transporters.
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Affiliation(s)
- Csilla Özvegy-Laczka
- Institute of Enzymology, RCNS, Eötvös Loránd Research Network, H-1117 Budapest, Magyar tudósok krt. 2., Hungary.
| | - Orsolya Ungvári
- Institute of Enzymology, RCNS, Eötvös Loránd Research Network, H-1117 Budapest, Magyar tudósok krt. 2., Hungary; Doctoral School of Biology, Institute of Biology, ELTE Eötvös Loránd University, Budapest, Hungary
| | - Éva Bakos
- Institute of Enzymology, RCNS, Eötvös Loránd Research Network, H-1117 Budapest, Magyar tudósok krt. 2., Hungary
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6
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The Mechanisms of lncRNA-Mediated Multidrug Resistance and the Clinical Application Prospects of lncRNAs in Breast Cancer. Cancers (Basel) 2022; 14:cancers14092101. [PMID: 35565231 PMCID: PMC9103444 DOI: 10.3390/cancers14092101] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/05/2022] [Accepted: 04/21/2022] [Indexed: 02/01/2023] Open
Abstract
Simple Summary Multidrug resistance (MDR) is a major cause of breast cancer (BC) chemotherapy failure. Long noncoding RNAs (lncRNAs) have been shown closely related to the chemoresistance of BC. In this work, the mechanisms of lncRNA-mediated MDR in BC were elaborated from eight sections, including apoptosis, autophagy, DNA repair, cell cycle, drug efflux, epithelial-mesenchymal transition, epigenetic modification and the tumor microenvironment. Additionally, we also discuss the clinical significance of lncRNAs, which may be biomarkers for diagnosis, therapy and prognosis. Abstract Breast cancer (BC) is a highly heterogeneous disease and presents a great threat to female health worldwide. Chemotherapy is one of the predominant strategies for the treatment of BC; however, multidrug resistance (MDR) has seriously affected or hindered the effect of chemotherapy. Recently, a growing number of studies have indicated that lncRNAs play vital and varied roles in BC chemoresistance, including apoptosis, autophagy, DNA repair, cell cycle, drug efflux, epithelial-mesenchymal transition (EMT), epigenetic modification and the tumor microenvironment (TME). Although thousands of lncRNAs have been implicated in the chemoresistance of BC, a systematic review of their regulatory mechanisms remains to be performed. In this review, we systematically summarized the mechanisms of MDR and the functions of lncRNAs mediated in the chemoresistance of BC from the latest literature. These findings significantly enhance the current understanding of lncRNAs and suggest that they may be promising prognostic biomarkers for BC patients receiving chemotherapy, as well as therapeutic targets to prevent or reverse chemoresistance.
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Abzianidze V, Moiseeva N, Suponina D, Zakharenkova S, Rogovskaya N, Laletina L, Holder AA, Krivorotov D, Bogachenkov A, Garabadzhiu A, Ukolov A, Kosorukov V. Natural Phaeosphaeride A Derivatives Overcome Drug Resistance of Tumor Cells and Modulate Signaling Pathways. Pharmaceuticals (Basel) 2022; 15:ph15040395. [PMID: 35455394 PMCID: PMC9030166 DOI: 10.3390/ph15040395] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 03/18/2022] [Accepted: 03/22/2022] [Indexed: 02/05/2023] Open
Abstract
In the present study, natural phaeosphaeride A (PPA) derivatives are synthesized. Anti-tumor studies are carried out on the PC3, K562, HCT-116, THP-1, MCF-7, A549, NCI-H929, Jurkat, and RPMI8226 tumor cell lines, and on the human embryonic kidney (HEK293) cell line. All the compounds synthesized turned out to have better efficacy than PPA towards the tumor cell lines listed. Among them, three compounds exhibited an ability to overcome the drug resistance of tumor cells associated with the overexpression of the P-glycoprotein by modulating the work of this transporter. Luminex xMAP technology was used to assess the effect of five synthesized compounds on the activation of intracellular kinase cascades in A431 cells. MILLIPLEX MAP Multi-Pathway Magnetic Bead 9-Plex was used, which allowed for the simultaneous detection of the following nine phosphorylated protein markers of the main intracellular signaling pathways: a universal transcription factor that controls the expression of immune-response genes, apoptosis and cell cycle NFκB (pS536); cAMP-dependent transcription factor (CREB (pS133); mitogen-activated kinase p38 (pT180/pY182); stress-activated protein kinase JNK (pT183/pY185); ribosomal SK; transcription factors STAT3 (pS727) and STAT5A/B (pY694/699); protein kinase B (Akt) (pS473); and kinase regulated by extracellular signals ERK1/2 (pT185/pY187). The effect of various concentrations of PPA derivatives on the cell culture was studied using xCelligence RTCA equipment. The compounds were found to modulate JNK, ERK1/2, and p38 signaling pathways. The set of activated kinase cascades suggests that oxidative stress is the main probable mechanism of the toxic action of PPA derivatives.
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Affiliation(s)
- Victoria Abzianidze
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
- Correspondence: (V.A.); (A.H.); Tel.: +7-981-249-0902 (V.A.); +1-757-683-7102 (A.H.)
| | - Natalia Moiseeva
- Laboratory of Tumor Cell Genetics, Institute of Carcinogenesis, N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation, 115478 Moscow, Russia; (N.M.); (L.L.)
| | - Diana Suponina
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
| | - Sofya Zakharenkova
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
| | - Nadezhda Rogovskaya
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
| | - Lidia Laletina
- Laboratory of Tumor Cell Genetics, Institute of Carcinogenesis, N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation, 115478 Moscow, Russia; (N.M.); (L.L.)
| | - Alvin A. Holder
- Department of Chemistry and Biochemistry, Old Dominion University, 4501 Elkhorn Avenue, Norfolk, VA 23529, USA
- Correspondence: (V.A.); (A.H.); Tel.: +7-981-249-0902 (V.A.); +1-757-683-7102 (A.H.)
| | - Denis Krivorotov
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
| | - Alexander Bogachenkov
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
| | - Alexander Garabadzhiu
- Saint Petersburg State Technological Institute (Technical University), 190013 Saint Petersburg, Russia;
| | - Anton Ukolov
- Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint Petersburg, Russia; (D.S.); (S.Z.); (N.R.); (D.K.); (A.B.); (A.U.)
| | - Vyacheslav Kosorukov
- Laboratory of Transgenic Drugs, N.N. Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation, 115478 Moscow, Russia;
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Goebel J, Chmielewski J, Hrycyna CA. The roles of the human ATP-binding cassette transporters P-glycoprotein and ABCG2 in multidrug resistance in cancer and at endogenous sites: future opportunities for structure-based drug design of inhibitors. CANCER DRUG RESISTANCE (ALHAMBRA, CALIF.) 2022; 4:784-804. [PMID: 34993424 PMCID: PMC8730335 DOI: 10.20517/cdr.2021.19] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ATP-binding cassette (ABC) transporters P-glycoprotein (P-gp) and ABCG2 are multidrug transporters that confer drug resistance to numerous anti-cancer therapeutics in cell culture. These findings initially created great excitement in the medical oncology community, as inhibitors of these transporters held the promise of overcoming clinical multidrug resistance in cancer patients. However, clinical trials of P-gp and ABCG2 inhibitors in combination with cancer chemotherapeutics have not been successful due, in part, to flawed clinical trial designs resulting from an incomplete molecular understanding of the multifactorial basis of multidrug resistance (MDR) in the cancers examined. The field was also stymied by the lack of high-resolution structural information for P-gp and ABCG2 for use in the rational structure-based drug design of inhibitors. Recent advances in structural biology have led to numerous structures of both ABCG2 and P-gp that elucidated more clearly the mechanism of transport and the polyspecific nature of their substrate and inhibitor binding sites. These data should prove useful helpful for developing even more potent and specific inhibitors of both transporters. As such, although possible pharmacokinetic interactions would need to be evaluated, these inhibitors may show greater effectiveness in overcoming ABC-dependent multidrug resistance in combination with chemotherapeutics in carefully selected subsets of cancers. Another perhaps even more compelling use of these inhibitors may be in reversibly inhibiting endogenously expressed P-gp and ABCG2, which serve a protective role at various blood-tissue barriers. Inhibition of these transporters at sanctuary sites such as the brain and gut could lead to increased penetration by chemotherapeutics used to treat brain cancers or other brain disorders and increased oral bioavailability of these agents, respectively.
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Affiliation(s)
- Jason Goebel
- Department of Chemistry, Purdue University West Lafayette, IN 47907, USA
| | - Jean Chmielewski
- Department of Chemistry, Purdue University West Lafayette, IN 47907, USA
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9
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Ramírez AS, Nosol K, Locher KP. Production of Human ABC Transporters and Oligosaccharyltransferase Complexes for Structural Studies. Methods Mol Biol 2022; 2507:273-294. [PMID: 35773587 DOI: 10.1007/978-1-0716-2368-8_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Structural studies of membrane proteins require high-quality samples. The target proteins should not only be pure and homogeneous but should also be active and allow the capture of a functionally relevant state. Here we present optimized methods for the expression and purification of human ABC transporters and oligosaccharyltransferase (OST) complexes that can be used for high-resolution structure determination using single-particle cryo-electron microscopy (cryo-EM). The protocols are based on the generation of stable cell lines that enable tetracycline-inducible expression of the target proteins. For the multidrug exporter ABCB1, we describe a protocol for reconstitution into nanodiscs and evaluation of the ATPase activity in the presence of drugs. For human OST, we describe a strategy for the purification of OST-A and OST-B complexes, including techniques to evaluate their integrity and activity using in vitro glycosylation assays. These protocols can be adapted for the production of other human ABC transporters and multimeric membrane protein complexes.
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Affiliation(s)
- Ana S Ramírez
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich, Switzerland
| | - Kamil Nosol
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich, Switzerland
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich, Switzerland.
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10
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Liang BJ, Lusvarghi S, Ambudkar SV, Huang HC. Use of photoimmunoconjugates to characterize ABCB1 in cancer cells. NANOPHOTONICS 2021; 10:3049-3061. [PMID: 35070633 PMCID: PMC8773461 DOI: 10.1515/nanoph-2021-0252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Accurate detection of ATP-binding cassette drug transporter ABCB1 expression is imperative for precise identification of drug-resistant tumors. Existing detection methods fail to provide the necessary molecular details regarding the functional state of the transporter. Photo-immunoconjugates are a unique class of antibody-dye conjugates for molecular diagnosis and therapeutic treatment. However, conjugating hydrophobic photosensitizers to hydrophilic antibodies is quite challenging. Here, we devise a photoimmunoconjugate that combines a clinically approved benzoporphyrin derivative (BPD) photosensitizer and the conformational-sensitive UIC2 monoclonal antibody to target functionally active human ABCB1 (i.e., ABCB1 in the inward-open conformation). We show that PEGylation of UIC2 enhances the BPD conjugation efficiency and reduces the amount of non-covalently conjugated BPD molecules by 17%. Size exclusion chromatography effectively separates the different molecular weight species found in the UIC2-BPD sample. The binding of UIC2-BPD to ABCB1 was demonstrated in lipidic nanodiscs and ABCB1-overexpressing triple negative breast cancer (TNBC) cells. UIC2-BPD was found to retain the conformation sensitivity of UIC2, as the addition of ABCB1 modulators increases the antibody reactivity in vitro. Thus, the inherent fluorescence capability of BPD can be used to label ABCB1-overexpressing TNBC cells using UIC2-BPD. Our findings provide insight into conjugation of hydrophobic photosensitizers to conformation-sensitive antibodies to target proteins expressed on the surface of cancer cells.
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Affiliation(s)
- Barry J. Liang
- Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742, USA; and Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sabrina Lusvarghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Suresh V. Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Room 2120, Bldg 37, 37 Convent Drive, Bethesda, MD 20892-4256, USA
| | - Huang-Chiao Huang
- Fischell Department of Bioengineering, University of Maryland, 8278 Paint Branch Drive, College Park, MD 20742-5031, USA; and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201-1595, USA
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11
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Elfadadny A, El-Husseiny HM, Abugomaa A, Ragab RF, Mady EA, Aboubakr M, Samir H, Mandour AS, El-Mleeh A, El-Far AH, Abd El-Aziz AH, Elbadawy M. Role of multidrug resistance-associated proteins in cancer therapeutics: past, present, and future perspectives. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021; 28:49447-49466. [PMID: 34355314 DOI: 10.1007/s11356-021-15759-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 07/28/2021] [Indexed: 06/13/2023]
Abstract
Cancer, a major public health problem, is one of the world's top leading causes of death. Common treatments for cancer include cytotoxic chemotherapy, surgery, targeted drugs, endocrine therapy, and immunotherapy. However, despite the outstanding achievements in cancer therapies during the last years, resistance to conventional chemotherapeutic agents and new targeted drugs is still the major challenge. In the present review, we explain the different mechanisms involved in cancer therapy and the detailed outlines of cancer drug resistance regarding multidrug resistance-associated proteins (MRPs) and their role in treatment failures by common chemotherapeutic agents. Further, different modulators of MRPs are presented. Finally, we outlined the models used to analyze MRP transporters and proposed a future impact that may set up a base or pave the way for many researchers to investigate the cancer MRP further.
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Affiliation(s)
- Ahmed Elfadadny
- Department of Animal Medicine, Faculty of Veterinary Medicine, Damanhour University, Damanhour, El-Beheira, 22511, Egypt
| | - Hussein M El-Husseiny
- Department of Surgery, Anesthesiology, and Radiology, Faculty of Veterinary Medicine, Benha University, Moshtohor, Toukh, Elqaliobiya, 13736, Egypt
| | - Amira Abugomaa
- Faculty of Veterinary Medicine, Mansoura University, Mansoura, Dakahliya, 35516, Egypt
| | - Rokaia F Ragab
- Department of Biochemistry, Faculty of Veterinary Medicine, Damanhour University, Damanhour, El-Beheira, 22511, Egypt
| | - Eman A Mady
- Department of Animal Hygiene, Behavior and Management, Faculty of Veterinary Medicine, Benha University, Moshtohor, Toukh, Elqaliobiya, 13736, Egypt
| | - Mohamed Aboubakr
- Department of Pharmacology, Faculty of Veterinary Medicine, Benha University, Moshtohor, Toukh, Elqaliobiya, 13736, Egypt
| | - Haney Samir
- Department of Theriogenology, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt
| | - Ahmed S Mandour
- Department of Veterinary Medicine (Internal Medicine), Faculty of Veterinary Medicine, Suez Canal University, Ismailia, 41522, Egypt
| | - Amany El-Mleeh
- Department of Pharmacology, Faculty of Veterinary Medicine, Menoufia University, Shibin El Kom, Egypt
| | - Ali H El-Far
- Department of Biochemistry, Faculty of Veterinary Medicine, Damanhour University, Damanhour, El-Beheira, 22511, Egypt
| | - Ayman H Abd El-Aziz
- Animal Husbandry and Animal Wealth Development Department, Faculty of Veterinary Medicine, Damanhour University, Damanhour, 22511, Egypt
| | - Mohamed Elbadawy
- Department of Pharmacology, Faculty of Veterinary Medicine, Benha University, Moshtohor, Toukh, Elqaliobiya, 13736, Egypt.
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12
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Valspodar limits human cytomegalovirus infection and dissemination. Antiviral Res 2021; 193:105124. [PMID: 34197862 DOI: 10.1016/j.antiviral.2021.105124] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 11/20/2022]
Abstract
Human cytomegalovirus (HCMV) is a ubiquitous pathogen that establishes a life-long infection affecting up to 80% of the US population. HCMV periodically reactivates leading to enhanced morbidity and mortality in immunosuppressed patients causing a range of complications including organ transplant failure and cognitive disorders in neonates. Therapeutic options for HCMV are limited to a handful of antivirals that target late stages of the virus life cycle and efficacy is often challenged by the emergence of mutations that confer resistance. In addition, these antiviral therapies may have adverse reactions including neutropenia in newborns and an increase in adverse cardiac events in HSCT patients. These findings highlight the need to develop novel therapeutics that target different steps of the viral life cycle. To this end, we screened a small molecule library against ion transporters to identify new antivirals against the early steps of virus infection. We identified valspodar, a 2nd-generation ABC transporter inhibitor, that limits HCMV infection as demonstrated by the decrease in IE2 expression of virus infected cells. Cells treated with increasing concentrations of valspodar over a 9-day period show minimal cytotoxicity. Importantly, valspodar limits HCMV plaque numbers in comparison to DMSO controls demonstrating its ability to inhibit viral dissemination. Collectively, valspodar represents a potential new anti-HCMV therapeutic that limits virus infection by likely targeting a host factor. Further, the data suggest that specific ABC transporters may participate in the HCMV life-cycle.
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13
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Liu S, Khan AR, Yang X, Dong B, Ji J, Zhai G. The reversal of chemotherapy-induced multidrug resistance by nanomedicine for cancer therapy. J Control Release 2021; 335:1-20. [PMID: 33991600 DOI: 10.1016/j.jconrel.2021.05.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 05/08/2021] [Accepted: 05/11/2021] [Indexed: 12/13/2022]
Abstract
Multidrug resistance (MDR) of cancer is a persistent problem in chemotherapy. Scientists have considered the overexpressed efflux transporters responsible for MDR and chemotherapy failure. MDR extremely limits the therapeutic effect of chemotherapy in cancer treatment. Many strategies have been applied to solve this problem. Multifunctional nanoparticles may be one of the most promising approaches to reverse MDR of tumor. These nanoparticles can keep stability in the blood circulation and selectively accumulated in the tumor microenvironment (TME) either by passive or active targeting. The stimuli-sensitive or organelle-targeting nanoparticles can release the drug at the targeted-site without exposure to normal tissues. In order to better understand reversal of MDR, three main strategies are concluded in this review. First strategy is the synergistic effect of chemotherapeutic drugs and ABC transporter inhibitors. Through directly inhibiting overexpressed ABC transporters, chemotherapeutic drugs can enter into resistant cells without being efflux. Second strategy is based on nanoparticles circumventing over-expressed efflux transporters and directly targeting resistance-related organelles. Third approach is the combination of multiple therapy modes overcoming cancer resistance. At last, numerous researches demonstrated cancer stem-like cells (CSCs) had a deep relation with drug resistance. Here, we discuss two different drug delivery approaches of nanomedicine based on CSC therapy.
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Affiliation(s)
- Shangui Liu
- Department of Pharmaceutics, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, PR China
| | - Abdur Rauf Khan
- Department of Pharmaceutics, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, PR China
| | - Xiaoye Yang
- Department of Pharmaceutics, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, PR China
| | - Bo Dong
- Department of cardiovascular medicine, Shandong Provincial Hospital, Jinan 250021, PR China
| | - Jianbo Ji
- Department of Pharmaceutics, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, PR China
| | - Guangxi Zhai
- Department of Pharmaceutics, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, Jinan 250012, PR China.
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14
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Liu Q, Liu DW, Zheng MJ, Deng L, Wang HM, Jin S, Liu JJ, Hao YY, Zhu LC, Lin B. Human epididymis protein 4 promotes P‑glycoprotein‑mediated chemoresistance in ovarian cancer cells through interactions with Annexin II. Mol Med Rep 2021; 24:496. [PMID: 33955501 PMCID: PMC8127061 DOI: 10.3892/mmr.2021.12135] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 03/16/2021] [Indexed: 12/11/2022] Open
Abstract
The aim of the present study was to investigate the effects of human epididymis protein 4 (HE4) on drug resistance and its underlying mechanisms. The associations among proteins were detected by immunoprecipitation and immunofluorescence assays. Then, stably transfected cell lines CAOV3-HE4-L and CAOV3-A2-L expressing HE4 short hairpin (sh)RNAs and ANXA2 shRNAs, respectively, were constructed. MTT assay, immunocytochemistry, western blotting, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and flow cytometry were employed to examine drug sensitivity, as well as the expression and activity of P-glycoprotein (P-gp). HE4 and P-gp in epithelial ovarian cancer tissues were assessed via immunohistochemistry. MicroRNAs that targeted the P-gp gene, ABCB1, were predicted using bioinformatics methods, and their expression was evaluated by RT-qPCR. The common signaling pathways shared by HE4, ANXA2 and P-gp were selected by Gene Set Enrichment Analysis (GSEA). The interaction of HE4, ANXA2 and P-gp were confirmed. P-gp expression was positively associated with HE4 and ANXA2 expression, respectively. Moreover, it was observed that there was no significant rescue of P-gp expression in CAOV3-A2-L cells following the administration of active HE4 protein. In addition, the expression of HE4 and P-gp in ovarian cancer tissues of drug-resistant patients were higher compared with that of the drug-sensitive group (P<0.05). Furthermore, the results revealed that hsa-miR-129-5p was significantly increased accompanied by decreased HE4 or ANXA2 expression and P-gp expression in CAOV3-HE4-L and CAOV3-A2-L cells. GSEA analyses disclosed that HE4, ANXA2 and P-gp genes were commonly enriched in the signaling pathway involved in regulating the actin cytoskeleton. These results indicated that HE4 promotes P-gp-mediated drug resistance in ovarian cancer cells through the interactions with ANXA2, and the underlying mechanism may be associated with decreased expression of hsa-miR-129-5p and dysregulation of the actin cytoskeleton signaling pathway.
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Affiliation(s)
- Qing Liu
- Department of Obstetrics and Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, Liaoning 110000, P.R. China
| | - Da-Wo Liu
- Department of Obstetrics and Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, Liaoning 110000, P.R. China
| | - Ming-Jun Zheng
- Department of Obstetrics and Gynecology, University Hospital, LMU Munich, D‑80337 Munich, Germany
| | - Lu Deng
- Department of Obstetrics and Gynecology, Hospital of Fudan University, Shanghai 200000, P.R. China
| | - Hui-Min Wang
- Department of Obstetrics and Gynecology, Liaoning Cancer Hospital and Institute, Shenyang, Liaoning 110000, P.R. China
| | - Shan Jin
- Department of Obstetrics and Gynecology, Liaoning Cancer Hospital and Institute, Shenyang, Liaoning 110000, P.R. China
| | - Juan-Juan Liu
- Department of Obstetrics and Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, Liaoning 110000, P.R. China
| | - Ying-Ying Hao
- Department of Obstetrics and Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, Liaoning 110000, P.R. China
| | - Lian-Cheng Zhu
- Department of Obstetrics and Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, Liaoning 110000, P.R. China
| | - Bei Lin
- Department of Obstetrics and Gynecology, Shengjing Hospital Affiliated to China Medical University, Shenyang, Liaoning 110000, P.R. China
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15
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Role of ABCB1 in mediating chemoresistance of triple-negative breast cancers. Biosci Rep 2021; 41:227788. [PMID: 33543229 PMCID: PMC7909869 DOI: 10.1042/bsr20204092] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/14/2021] [Accepted: 02/04/2021] [Indexed: 12/31/2022] Open
Abstract
Triple-negative breast cancer (TNBC) is a group of breast cancers which neither express hormonal receptors nor human epidermal growth factor receptor. Hence, there is a lack of currently known targeted therapies and the only available line of systemic treatment option is chemotherapy or more recently immune therapy. However, in patients with relapsed disease after adjuvant or neoadjuvant therapy, resistance to chemotherapeutic agents has often developed, which results in poor treatment response. Multidrug resistance (MDR) has emerged as an important mechanism by which TNBCs mediate drug resistance and occurs primarily due to overexpression of ATP-binding cassette (ABC) transporter proteins such as P-glycoprotein (Pgp). Pgp overexpression had been linked to poor outcome, reduced survival rates and chemoresistance in patients. The aim of this mini-review is to provide a topical overview of the recent studies and to generate further interest in this critical research area, with the aim to develop an effective and safe approach for overcoming Pgp-mediated chemoresistance in TNBC.
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16
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Bordignon E, Seeger MA, Galazzo L, Meier G. From in vitro towards in situ: structure-based investigation of ABC exporters by electron paramagnetic resonance spectroscopy. FEBS Lett 2020; 594:3839-3856. [PMID: 33219535 DOI: 10.1002/1873-3468.14004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 10/30/2020] [Accepted: 11/15/2020] [Indexed: 12/12/2022]
Abstract
ATP-binding cassette (ABC) exporters have been studied now for more than four decades, and recent structural investigation has produced a large number of protein database entries. Yet, important questions about how ABC exporters function at the molecular level remain debated, such as which are the molecular recognition hotspots and the allosteric couplings dynamically regulating the communication between the catalytic cycle and the export of substrates. This conundrum mainly arises from technical limitations confining all research to in vitro analysis of ABC transporters in detergent solutions or embedded in membrane-mimicking environments. Therefore, a largely unanswered question is how ABC exporters operate in situ, namely in the native membrane context of a metabolically active cell. This review focuses on novel mechanistic insights into type I ABC exporters gained through a unique combination of structure determination, biochemical characterization, generation of conformation-specific nanobodies/sybodies and double electron-electron resonance.
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Affiliation(s)
- Enrica Bordignon
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Markus A Seeger
- Institute of Medical Microbiology, University of Zurich, Switzerland
| | - Laura Galazzo
- Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
| | - Gianmarco Meier
- Institute of Medical Microbiology, University of Zurich, Switzerland
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17
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Kozák E, Szikora B, Iliás A, Jani PK, Hegyi Z, Matula Z, Dedinszki D, Tőkési N, Fülöp K, Pomozi V, Várady G, Bakos É, Tusnády GE, Kacskovics I, Váradi A. Creation of the first monoclonal antibody recognizing an extracellular epitope of hABCC6. FEBS Lett 2020; 595:789-798. [PMID: 33159684 DOI: 10.1002/1873-3468.13991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 10/12/2020] [Accepted: 10/16/2020] [Indexed: 11/11/2022]
Abstract
Mutations in the ABCC6 gene result in calcification diseases such as pseudoxanthoma elasticum or Generalized Arterial Calcification of Infancy. Generation of antibodies recognizing an extracellular (EC) epitope of ABCC6 has been hampered by the short EC segments of the protein. To overcome this limitation, we immunized bovine FcRn transgenic mice exhibiting an augmented humoral immune response with Human Embryonic Kidney 293 cells cells expressing human ABCC6 (hABCC6). We obtained a monoclonal antibody recognizing an EC epitope of hABCC6 that we named mEChC6. Limited proteolysis revealed that the epitope is within a loop in the N-terminal half of ABCC6 and probably spans amino acids 338-347. mEChC6 recognizes hABCC6 in the liver of hABCC6 transgenic mice, verifying both specificity and EC binding to intact hepatocytes.
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Affiliation(s)
- Eszter Kozák
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary.,Department of Immunology, Eötvös Loránd University of Budapest, Hungary
| | - Bence Szikora
- Department of Immunology, Eötvös Loránd University of Budapest, Hungary.,ImmunoGenes Ltd., Budakeszi, Hungary
| | - Attila Iliás
- Department of Immunology, Eötvös Loránd University of Budapest, Hungary
| | | | - Zoltán Hegyi
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Zsolt Matula
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Dóra Dedinszki
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Natália Tőkési
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Krisztina Fülöp
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Viola Pomozi
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - György Várady
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Éva Bakos
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Gabor E Tusnády
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
| | - Imre Kacskovics
- Department of Immunology, Eötvös Loránd University of Budapest, Hungary.,ImmunoGenes Ltd., Budakeszi, Hungary
| | - Andras Váradi
- Institute of Enzymology, Research Center for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary
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18
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Cryo-EM structures reveal distinct mechanisms of inhibition of the human multidrug transporter ABCB1. Proc Natl Acad Sci U S A 2020; 117:26245-26253. [PMID: 33020312 DOI: 10.1073/pnas.2010264117] [Citation(s) in RCA: 126] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ABCB1 detoxifies cells by exporting diverse xenobiotic compounds, thereby limiting drug disposition and contributing to multidrug resistance in cancer cells. Multiple small-molecule inhibitors and inhibitory antibodies have been developed for therapeutic applications, but the structural basis of their activity is insufficiently understood. We determined cryo-EM structures of nanodisc-reconstituted, human ABCB1 in complex with the Fab fragment of the inhibitory, monoclonal antibody MRK16 and bound to a substrate (the antitumor drug vincristine) or to the potent inhibitors elacridar, tariquidar, or zosuquidar. We found that inhibitors bound in pairs, with one molecule lodged in the central drug-binding pocket and a second extending into a phenylalanine-rich cavity that we termed the "access tunnel." This finding explains how inhibitors can act as substrates at low concentration, but interfere with the early steps of the peristaltic extrusion mechanism at higher concentration. Our structural data will also help the development of more potent and selective ABCB1 inhibitors.
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19
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Gupta SK, Singh P, Ali V, Verma M. Role of membrane-embedded drug efflux ABC transporters in the cancer chemotherapy. Oncol Rev 2020; 14:448. [PMID: 32676170 PMCID: PMC7358983 DOI: 10.4081/oncol.2020.448] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 03/20/2020] [Indexed: 12/12/2022] Open
Abstract
One of the major problems being faced by researchers and clinicians in leukemic treatment is the development of multidrug resistance (MDR) which restrict the action of several tyrosine kinase inhibitors (TKIs). MDR is a major obstacle to the success of cancer chemotherapy. The mechanism of MDR involves active drug efflux transport of ABC superfamily of proteins such as Pglycoprotein (P-gp/ABCB1), multidrug resistance-associated protein 2 (MRP2/ABCC2), and breast cancer resistance protein (BCRP/ABCG2) that weaken the effectiveness of chemotherapeutics and negative impact on the future of anticancer therapy. In this review, the authors aim to provide an overview of various multidrug resistance (MDR) mechanisms observed in cancer cells as well as the various strategies developed to overcome these MDR. Extensive studies have been carried out since last several years to enhance the efficacy of chemotherapy by defeating these MDR mechanisms with the use of novel anticancer drugs that could escape from the efflux reaction, MDR modulators or chemosensitizers, multifunctional nanotechnology, and RNA interference (RNAi) therapy.
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Affiliation(s)
- Sonu Kumar Gupta
- Department of Biochemistry, School of Basic & Applied Sciences, Central University of Punjab, Punjab, India
| | - Priyanka Singh
- Department of Biochemistry, School of Basic & Applied Sciences, Central University of Punjab, Punjab, India
| | - Villayat Ali
- Department of Biochemistry, School of Basic & Applied Sciences, Central University of Punjab, Punjab, India
| | - Malkhey Verma
- Department of Biochemistry, School of Basic & Applied Sciences, Central University of Punjab, Punjab, India
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20
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Thangapandian S, Kapoor K, Tajkhorshid E. Probing cholesterol binding and translocation in P-glycoprotein. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2020; 1862:183090. [PMID: 31676371 PMCID: PMC6934093 DOI: 10.1016/j.bbamem.2019.183090] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 09/15/2019] [Accepted: 09/17/2019] [Indexed: 01/01/2023]
Abstract
P-glycoprotein (Pgp) is a biomedically important member of the ABC transporter superfamily that mediates multidrug resistance in various cancer types. Substrate binding and transport in Pgp are modulated by the presence of cholesterol in the membrane. Structural information on cholesterol binding sites and mechanistic details of its redistribution are, however, largely unknown. In this study, a set of 40 independent molecular dynamics (MD) simulations of Pgp embedded in cholesterol-rich lipid bilayers are reported, totaling 8 μs, enabling extensive sampling of cholesterol-protein interactions in Pgp. Clustering analyses of the ensemble of cholesterol molecules (∼5740) sampled around Pgp in these simulations reveal specific and asymmetric cholesterol-binding regions formed by the transmembrane (TM) helices TM1-6 and TM8. Notably, not all the putative cholesterol binding sites identified by MD can be predicted by the primary sequence based cholesterol-recognition amino acid consensus (CRAC) or inverted CRAC (CARC) motifs, an observation that we attribute to inadequacy of these motifs to account for binding sites formed by remote amino acids in the sequence that can still be spatially adjacent to each other. Binding of cholesterol to Pgp occurs more frequently through its rough β-face formed by the two protruding methyl groups, whereas the opposite smooth α-face prefers packing alongside the membrane lipids. One full and two partial cholesterol flipping events between the two leaflets of the bilayer mediated by the surface of Pgp are also captured in these simulations. All flipping events are observed in a region formed by helices TM1, TM2, and TM11, featuring two full and two partial CRAC/CARC motifs, with Tyr49 and Tyr126 identified as key residues interacting with cholesterol during this event. Our study is the first to report direct observation of unconventional cholesterol translocation on the surface of Pgp, providing a secondary transport model for the known flippase activity of ABC exporters of cholesterol. This article is part of a Special Issue entitled: Molecular biophysics of membranes and membrane proteins.
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Affiliation(s)
- Sundar Thangapandian
- NIH Center for Molecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Karan Kapoor
- NIH Center for Molecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Emad Tajkhorshid
- NIH Center for Molecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
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21
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Yuan Y, Zhang J, Qi X, Li S, Liu G, Siddhanta S, Barman I, Song X, McMahon MT, Bulte JWM. Furin-mediated intracellular self-assembly of olsalazine nanoparticles for enhanced magnetic resonance imaging and tumour therapy. NATURE MATERIALS 2019; 18:1376-1383. [PMID: 31636420 PMCID: PMC6872935 DOI: 10.1038/s41563-019-0503-4] [Citation(s) in RCA: 134] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 09/10/2019] [Indexed: 05/15/2023]
Abstract
Among the strategies used for enhancement of tumour retention of imaging agents or anticancer drugs is the rational design of probes that undergo a tumour-specific enzymatic reaction preventing them from being pumped out of the cell. Here, the anticancer agent olsalazine (Olsa) was conjugated to the cell-penetrating peptide RVRR. Taking advantage of a biologically compatible condensation reaction, single Olsa-RVRR molecules were self-assembled into large intracellular nanoparticles by the tumour-associated enzyme furin. Both Olsa-RVRR and Olsa nanoparticles were readily detected with chemical exchange saturation transfer magnetic resonance imaging by virtue of exchangeable Olsa hydroxyl protons. In vivo studies using HCT116 and LoVo murine xenografts showed that the OlsaCEST signal and anti-tumour therapeutic effect were 6.5- and 5.2-fold increased, respectively, compared to Olsa without RVRR, with an excellent 'theranostic correlation' (R2 = 0.97) between the imaging signal and therapeutic response (normalized tumour size). This furin-targeted, magnetic resonance imaging-detectable platform has potential for imaging tumour aggressiveness, drug accumulation and therapeutic response.
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Affiliation(s)
- Yue Yuan
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jia Zhang
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Xiaoliang Qi
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shuoguo Li
- Center for Biological Imaging, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Guanshu Liu
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Soumik Siddhanta
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD, USA
| | - Ishan Barman
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, MD, USA
- Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Xiaolei Song
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael T McMahon
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Jeff W M Bulte
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA.
- Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
- Department of Chemical & Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD, USA.
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22
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Amawi H, Sim HM, Tiwari AK, Ambudkar SV, Shukla S. ABC Transporter-Mediated Multidrug-Resistant Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1141:549-580. [PMID: 31571174 DOI: 10.1007/978-981-13-7647-4_12] [Citation(s) in RCA: 141] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ATP-binding cassette (ABC) transporters are involved in active pumping of many diverse substrates through the cellular membrane. The transport mediated by these proteins modulates the pharmacokinetics of many drugs and xenobiotics. These transporters are involved in the pathogenesis of several human diseases. The overexpression of certain transporters by cancer cells has been identified as a key factor in the development of resistance to chemotherapeutic agents. In this chapter, the localization of ABC transporters in the human body, their physiological roles, and their roles in the development of multidrug resistance (MDR) are reviewed. Specifically, P-glycoprotein (P-GP), multidrug resistance-associated proteins (MRPs), and breast cancer resistance protein (BCRP/ABCG2) are described in more detail. The potential of ABC transporters as therapeutic targets to overcome MDR and strategies for this purpose are discussed as well as various explanations for the lack of efficacy of ABC drug transporter inhibitors to increase the efficiency of chemotherapy.
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Affiliation(s)
- Haneen Amawi
- Department of Pharmacy Practice, Faculty of Pharmacy, Yarmouk University, Irbid, Jordan
| | - Hong-May Sim
- Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore, Singapore
| | - Amit K Tiwari
- Department of Pharmacology and Experimental Therapeutics, College of Pharmacy & Pharmaceutical Sciences, University of Toledo, Toledo, OH, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Suneet Shukla
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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23
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Alam A, Kowal J, Broude E, Roninson I, Locher KP. Structural insight into substrate and inhibitor discrimination by human P-glycoprotein. Science 2019; 363:753-756. [PMID: 30765569 DOI: 10.1126/science.aav7102] [Citation(s) in RCA: 293] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 01/18/2019] [Indexed: 12/19/2022]
Abstract
ABCB1, also known as P-glycoprotein, actively extrudes xenobiotic compounds across the plasma membrane of diverse cells, which contributes to cellular drug resistance and interferes with therapeutic drug delivery. We determined the 3.5-angstrom cryo-electron microscopy structure of substrate-bound human ABCB1 reconstituted in lipidic nanodiscs, revealing a single molecule of the chemotherapeutic compound paclitaxel (Taxol) bound in a central, occluded pocket. A second structure of inhibited, human-mouse chimeric ABCB1 revealed two molecules of zosuquidar occupying the same drug-binding pocket. Minor structural differences between substrate- and inhibitor-bound ABCB1 sites are amplified toward the nucleotide-binding domains (NBDs), revealing how the plasticity of the drug-binding site controls the dynamics of the adenosine triphosphate-hydrolyzing NBDs. Ordered cholesterol and phospholipid molecules suggest how the membrane modulates the conformational changes associated with drug binding and transport.
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Affiliation(s)
- Amer Alam
- Institute of Molecular Biology and Biophysics, ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland
| | - Julia Kowal
- Institute of Molecular Biology and Biophysics, ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland
| | - Eugenia Broude
- Department of Drug Discovery and Biomedical Sciences, College of Pharmacy, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, USA
| | - Igor Roninson
- Department of Drug Discovery and Biomedical Sciences, College of Pharmacy, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, USA
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, ETH Zürich, Otto-Stern-Weg 5, 8093 Zürich, Switzerland.
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24
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The extracellular gate shapes the energy profile of an ABC exporter. Nat Commun 2019; 10:2260. [PMID: 31113958 PMCID: PMC6529423 DOI: 10.1038/s41467-019-09892-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 04/04/2019] [Indexed: 11/08/2022] Open
Abstract
ABC exporters harness the energy of ATP to pump substrates across membranes. Extracellular gate opening and closure are key steps of the transport cycle, but the underlying mechanism is poorly understood. Here, we generated a synthetic single domain antibody (sybody) that recognizes the heterodimeric ABC exporter TM287/288 exclusively in the presence of ATP, which was essential to solve a 3.2 Å crystal structure of the outward-facing transporter. The sybody binds to an extracellular wing and strongly inhibits ATPase activity by shifting the transporter's conformational equilibrium towards the outward-facing state, as shown by double electron-electron resonance (DEER). Mutations that facilitate extracellular gate opening result in a comparable equilibrium shift and strongly reduce ATPase activity and drug transport. Using the sybody as conformational probe, we demonstrate that efficient extracellular gate closure is required to dissociate the NBD dimer after ATP hydrolysis to reset the transporter back to its inward-facing state.
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25
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Dasari R, Błauż A, Medellin DC, Kassim RM, Viera C, Santarosa M, van der Westhuyzen AE, van Otterlo WAL, Olivas T, Yildiz T, Betancourt T, Shuster CB, Rogelj S, Rychlik B, Hudnall T, Frolova LV, Kornienko A. Microtubule-Targeting 7-Deazahypoxanthines Derived from Marine Alkaloid Rigidins: Exploration of the N3 and N9 Positions and Interaction with Multidrug-Resistance Proteins. ChemMedChem 2019; 14:322-333. [PMID: 30562414 PMCID: PMC6476547 DOI: 10.1002/cmdc.201800658] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Revised: 12/17/2018] [Indexed: 12/12/2022]
Abstract
Our laboratories have been investigating synthetic analogues of marine alkaloid rigidins that possess promising anticancer activities. These analogues, based on the 7-deazahypoxanthine skeleton, are available in one- or two-step synthetic sequences and exert cytotoxicity by disrupting microtubule dynamics in cancer cells. In the present work we extended the available structure-activity relationship (SAR) data to N3- and N9-substituted derivatives. Although N3 substitution results in loss of activity, the N9-substituted compounds retain nanomolar antiproliferative activities and the anti-tubulin mode of action of the original unsubstituted compounds. Furthermore, our results also demonstrate that multidrug-resistance (MDR) proteins do not confer resistance to both N9-unsubstituted and -substituted compounds. It was found that sublines overexpressing ABCG2, ABCC1, and ABCB1 proteins are as responsive to the rigidin analogues as their parental cell lines. Thus, the study reported herein provides further impetus to investigate the rigidin-inspired 7-deazahypoxanthines as promising anticancer agents.
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Affiliation(s)
- Ramesh Dasari
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, 78666, USA
| | - Andrzej Błauż
- Cytometry Lab, Department of Molecular Biophysics, Faculty of Biology and Environmental Protection, University of Łódź, ul. Pomorska 141/143, 90-236, Łódź, Poland
| | - Derek C Medellin
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, 78666, USA
| | - Roaa M Kassim
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
| | - Carlos Viera
- Departments of Chemistry and Biology, New Mexico Tech, Socorro, NM, 87801, USA
| | - Maximo Santarosa
- Departments of Chemistry and Biology, New Mexico Tech, Socorro, NM, 87801, USA
| | - Alet E van der Westhuyzen
- Department of Chemistry and Polymer Science, University of Stellenbosch, 7602, Stellenbosch, South Africa
| | - Willem A L van Otterlo
- Department of Chemistry and Polymer Science, University of Stellenbosch, 7602, Stellenbosch, South Africa
| | - Taryn Olivas
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, 78666, USA
| | - Tugba Yildiz
- Materials Science and Engineering Program, Texas State University, San Marcos, TX, 78666, USA
| | - Tania Betancourt
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, 78666, USA
- Materials Science and Engineering Program, Texas State University, San Marcos, TX, 78666, USA
| | - Charles B Shuster
- Department of Biology, New Mexico State University, Las Cruces, NM, 88003, USA
| | - Snezna Rogelj
- Departments of Chemistry and Biology, New Mexico Tech, Socorro, NM, 87801, USA
| | - Błażej Rychlik
- Cytometry Lab, Department of Molecular Biophysics, Faculty of Biology and Environmental Protection, University of Łódź, ul. Pomorska 141/143, 90-236, Łódź, Poland
| | - Todd Hudnall
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, 78666, USA
| | - Liliya V Frolova
- Departments of Chemistry and Biology, New Mexico Tech, Socorro, NM, 87801, USA
| | - Alexander Kornienko
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, TX, 78666, USA
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26
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Thorne JL, Battaglia S, Baxter DE, Hayes JL, Hutchinson SA, Jana S, Millican-Slater RA, Smith L, Teske MC, Wastall LM, Hughes TA. MiR-19b non-canonical binding is directed by HuR and confers chemosensitivity through regulation of P-glycoprotein in breast cancer. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:996-1006. [DOI: 10.1016/j.bbagrm.2018.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 07/09/2018] [Accepted: 08/23/2018] [Indexed: 12/25/2022]
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27
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Liu YC, Li YY, Yao XJ, Qi HL, Wei XX, Liu JN. Binding Performance of Human Intravenous Immunoglobulin and 20( S)-7-Ethylcamptothecin. Molecules 2018; 23:E2389. [PMID: 30231526 PMCID: PMC6225142 DOI: 10.3390/molecules23092389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 08/20/2018] [Accepted: 09/12/2018] [Indexed: 11/25/2022] Open
Abstract
A previous study showed that intravenous immunoglobulin (IVIG) could preserve higher levels of biologically active lactone moieties of topotecan, 7-ethyl-10-hydroxycamptothecin (SN-38) and 10-hydroxycamptothecin at physiological pH 7.40. As one of camptothecin analogues (CPTs), the interaction of 7-ethylcamptothecin and IVIG was studied in vitro in this study. It was shown that the main binding mode of IVIG to 7-ethylcamptothecin was hydrophobic interaction and hydrogen bonding, which is a non-specific and spontaneous interaction. The hydrophobic antigen-binding cavity of IgG would enwrap the drug into a host-guest inclusion complex and prevent hydrolysis of the encapsulated drug, while the drug is adjacent to the chromophores of IgG and may exchange energy with chromophores and quench the fluorescence of the protein. Also, the typical β-sheet structure of IVIG unfolded partially after binding to 7-ethylcamptothecin. Additionally, the binding properties of IVIG and six CPTs with different substituents at A-ring and/or B-ring including camptothecin, topotecan, irinotecan, 10-hydroxycamptothecin, 7-ethylcamptothecin and SN-38 were collected together and compared each other. Synergizing with anti-cancer drugs, IVIG could be used as a transporter protein for 7-ethylcamptothecin and other CPTs, allowing clinicians to devise new treatment protocols for patients.
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Affiliation(s)
- Yong-Chun Liu
- College of Chemistry and Chemical Engineering, Longdong University, Qingyang 745000, China.
- Longdong University & FLUOBON Collaborative Innovation Center, Longdong University, Qingyang 745000, China.
| | - Ying-Ying Li
- College of Chemistry and Chemical Engineering, Longdong University, Qingyang 745000, China.
- Longdong University & FLUOBON Collaborative Innovation Center, Longdong University, Qingyang 745000, China.
| | - Xiao-Jun Yao
- College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
| | - Hui-Li Qi
- College of Chemistry and Chemical Engineering, Longdong University, Qingyang 745000, China.
- Longdong University & FLUOBON Collaborative Innovation Center, Longdong University, Qingyang 745000, China.
| | - Xiao-Xia Wei
- College of Chemistry and Chemical Engineering, Longdong University, Qingyang 745000, China.
- Longdong University & FLUOBON Collaborative Innovation Center, Longdong University, Qingyang 745000, China.
| | - Jian-Ning Liu
- College of Chemistry and Chemical Engineering, Longdong University, Qingyang 745000, China.
- Longdong University & FLUOBON Collaborative Innovation Center, Longdong University, Qingyang 745000, China.
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28
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Bossennec M, Di Roio A, Caux C, Ménétrier-Caux C. MDR1 in immunity: friend or foe? Oncoimmunology 2018; 7:e1499388. [PMID: 30524890 PMCID: PMC6279327 DOI: 10.1080/2162402x.2018.1499388] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 07/08/2018] [Indexed: 02/09/2023] Open
Abstract
MDR1 is an ATP-dependent transmembrane transporter primarily studied for its role in the detoxification of tissues and for its implication in resistance of tumor cells to chemotherapy treatment. Several studies also report on its expression on immune cells where it plays a protective role from xenobiotics and toxins. This review provides an overview of what is known on MDR1 expression in immune cells in human, and its implications in different pathologies and their treatment options.
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Affiliation(s)
- Marion Bossennec
- Centre Léon Bérard, Cancer Research Center of Lyon (CRCL), Univ Lyon, Université Claude Bernard Lyon 1, Lyon France.,Immunology Virology Inflammation (IVI) department, Team "Therapeutic targeting of the tumor cells and their immune stroma", Lyon, France
| | - Anthony Di Roio
- Centre Léon Bérard, Cancer Research Center of Lyon (CRCL), Univ Lyon, Université Claude Bernard Lyon 1, Lyon France.,Immunology Virology Inflammation (IVI) department, Team "Therapeutic targeting of the tumor cells and their immune stroma", Lyon, France
| | - Christophe Caux
- Centre Léon Bérard, Cancer Research Center of Lyon (CRCL), Univ Lyon, Université Claude Bernard Lyon 1, Lyon France.,Immunology Virology Inflammation (IVI) department, Team "Therapeutic targeting of the tumor cells and their immune stroma", Lyon, France
| | - Christine Ménétrier-Caux
- Centre Léon Bérard, Cancer Research Center of Lyon (CRCL), Univ Lyon, Université Claude Bernard Lyon 1, Lyon France.,Immunology Virology Inflammation (IVI) department, Team "Therapeutic targeting of the tumor cells and their immune stroma", Lyon, France
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29
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Vahedi S, Lusvarghi S, Pluchino K, Shafrir Y, Durell SR, Gottesman MM, Ambudkar SV. Mapping discontinuous epitopes for MRK-16, UIC2 and 4E3 antibodies to extracellular loops 1 and 4 of human P-glycoprotein. Sci Rep 2018; 8:12716. [PMID: 30143707 PMCID: PMC6109178 DOI: 10.1038/s41598-018-30984-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 07/30/2018] [Indexed: 12/14/2022] Open
Abstract
P-glycoprotein (P-gp), an ATP-dependent efflux pump, is associated with the development of multidrug resistance in cancer cells. Antibody-mediated blockade of human P-gp activity has been shown to overcome drug resistance by re-sensitizing resistant cancer cells to anticancer drugs. Despite the potential clinical application of this finding, the epitopes of the three human P-gp-specific monoclonal antibodies MRK-16, UIC2 and 4E3, which bind to the extracellular loops (ECLs) have not yet been mapped. By generating human-mouse P-gp chimeras, we mapped the epitopes of these antibodies to ECLs 1 and 4. We then identified key amino acids in these regions by replacing mouse residues with homologous human P-gp residues to recover binding of antibodies to the mouse P-gp. We found that changing a total of ten residues, five each in ECL1 and ECL4, was sufficient to recover binding of both MRK-16 and 4E3 antibodies, suggesting a common epitope. However, recovery of the conformation-sensitive UIC2 epitope required replacement of thirteen residues in ECL1 and the same five residues replaced in the ECL4 for MRK-16 and 4E3 binding. These results demonstrate that discontinuous epitopes for MRK-16, UIC2 and 4E3 are located in the same regions of ECL1 and 4 of the multidrug transporter.
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Affiliation(s)
- Shahrooz Vahedi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA
| | - Sabrina Lusvarghi
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA
| | - Kristen Pluchino
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA
| | - Yinon Shafrir
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA
| | - Stewart R Durell
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA
| | - Michael M Gottesman
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892-4256, USA.
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30
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Sigdel KP, Wilt LA, Marsh BP, Roberts AG, King GM. The conformation and dynamics of P-glycoprotein in a lipid bilayer investigated by atomic force microscopy. Biochem Pharmacol 2018; 156:302-311. [PMID: 30121251 DOI: 10.1016/j.bcp.2018.08.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 08/14/2018] [Indexed: 12/17/2022]
Abstract
The membrane-bound P-glycoprotein (Pgp) transporter plays a major role in human disease and drug disposition because of its ability to efflux a chemically diverse range of drugs through ATP hydrolysis and ligand-induced conformational changes. Deciphering these structural changes is key to understanding the molecular basis of transport and to developing molecules that can modulate efflux. Here, atomic force microscopy (AFM) is used to directly image individual Pgp transporter molecules in a lipid bilayer under physiological pH and ambient temperature. Analysis of the Pgp AFM images revealed "small" and "large" protrusions from the lipid bilayer with significant differences in protrusion height and volume. The geometry of these "small" and "large" protrusions correlated to the predicted extracellular (EC) and cytosolic (C) domains of the Pgp X-ray crystal structure, respectively. To assign these protrusions, simulated AFM images were produced from the Pgp X-ray crystal structures with membrane planes defined by three computational approaches, and a simulated 80 Å AFM cantilever tip. The theoretical AFM images of the EC and C domains had similar heights and volumes to the "small" and "large" protrusions in the experimental AFM images, respectively. The assignment of the protrusions in the AFM images to the EC and C domains was confirmed by changes in protrusion volume by Pgp-specific antibodies. The Pgp domains showed a considerable degree of conformational dynamics in time resolved AFM images. With this information, a model of Pgp conformational dynamics in a lipid bilayer is proposed within the context of the known Pgp X-ray crystal structures.
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Affiliation(s)
- K P Sigdel
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, United States
| | - L A Wilt
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602, United States
| | - B P Marsh
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, United States
| | - A G Roberts
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602, United States.
| | - G M King
- Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, United States; Joint with Department of Biochemistry, University of Missouri, Columbia, MO 65211, United States.
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31
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Adamska A, Falasca M. ATP-binding cassette transporters in progression and clinical outcome of pancreatic cancer: What is the way forward? World J Gastroenterol 2018; 24:3222-3238. [PMID: 30090003 PMCID: PMC6079284 DOI: 10.3748/wjg.v24.i29.3222] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 05/31/2018] [Accepted: 06/27/2018] [Indexed: 02/06/2023] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive diseases and is characterized by high chemoresistance, leading to the lack of effective therapeutic approaches and grim prognosis. Despite increasing understanding of the mechanisms of chemoresistance in cancer and the role of ATP-binding cassette (ABC) transporters in this resistance, the therapeutic potential of their pharmacological inhibition has not been successfully exploited yet. In spite of the discovery of potent pharmacological modulators of ABC transporters, the results obtained in clinical trials have been so far disappointing, with high toxicity levels impairing their successful administration to the patients. Critically, although ABC transporters have been mostly studied for their involvement in development of multidrug resistance (MDR), in recent years the contribution of ABC transporters to cancer initiation and progression has emerged as an important area of research, the understanding of which could significantly influence the development of more specific and efficient therapies. In this review, we explore the role of ABC transporters in the development and progression of malignancies, with focus on PDAC. Their established involvement in development of MDR will be also presented. Moreover, an emerging role for ABC transporters as prognostic tools for patients' survival will be discussed, demonstrating the therapeutic potential of ABC transporters in cancer therapy.
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Affiliation(s)
- Aleksandra Adamska
- Metabolic Signalling Group, School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth 6102, WA, Australia
| | - Marco Falasca
- Metabolic Signalling Group, School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth 6102, WA, Australia
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32
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Abstract
The ATP binding cassette transporter ABCB1 (also termed P-glycoprotein) is a physiologically essential multidrug efflux transporter of key relevance to biomedicine. Here, we report the conformational trapping and structural analysis of ABCB1 in complex with the antigen-binding fragment of UIC2, a human ABCB1-specific inhibitory antibody, and zosuquidar, a third-generation ABCB1 inhibitor. The structures outline key features underlining specific ABCB1 inhibition by antibodies and small molecules, including a dual mode of inhibitor binding in a fully occluded ABCB1 cavity. Finally, our analysis sheds light on the conformational transitions undergone by the transporter to reach the inhibitor-bound state. The multidrug transporter ABCB1 (P-glycoprotein) is an ATP-binding cassette transporter that has a key role in protecting tissues from toxic insult and contributes to multidrug extrusion from cancer cells. Here, we report the near-atomic resolution cryo-EM structure of nucleotide-free ABCB1 trapped by an engineered disulfide cross-link between the nucleotide-binding domains (NBDs) and bound to the antigen-binding fragment of the human-specific inhibitory antibody UIC2 and to the third-generation ABCB1 inhibitor zosuquidar. Our structure reveals the transporter in an occluded conformation with a central, enclosed, inhibitor-binding pocket lined by residues from all transmembrane (TM) helices of ABCB1. The pocket spans almost the entire width of the lipid membrane and is occupied exclusively by two closely interacting zosuquidar molecules. The external, conformational epitope facilitating UIC2 binding is also visualized, providing a basis for its inhibition of substrate efflux. Additional cryo-EM structures suggest concerted movement of TM helices from both halves of the transporters associated with closing the NBD gap, as well as zosuquidar binding. Our results define distinct recognition interfaces of ABCB1 inhibitory agents, which may be exploited for therapeutic purposes.
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33
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Cho MH, Kim S, Lee JH, Shin TH, Yoo D, Cheon J. Magnetic Tandem Apoptosis for Overcoming Multidrug-Resistant Cancer. NANO LETTERS 2016; 16:7455-7460. [PMID: 27960458 DOI: 10.1021/acs.nanolett.6b03122] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Multidrug resistance (MDR) is a leading cause of failure in current chemotherapy treatment and constitutes a formidable challenge in therapeutics. Here, we demonstrate that a nanoscale magnetic tandem apoptosis trigger (m-TAT), which consists of a magnetic nanoparticle and chemodrug (e.g., doxorubicin), can completely remove MDR cancer cells in both in vitro and in vivo systems. m-TAT simultaneously activates extrinsic and intrinsic apoptosis signals in a synergistic fashion and downregulates the drug efflux pump (e.g., P-glycoprotein) which is one of the main causes of MDR. The tandem apoptosis strategy uses low level of chemodrug (in the nanomolar (nM) range) to eliminate MDR cancer cells. We further demonstrate that apoptosis of MDR cancer cells can be achieved in a spatially selective manner with single-cell level precision. Our study indicates that nanoscale tandem activation of convergent signaling pathways is a new platform concept to overcome MDR with high efficacy and specificity.
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Affiliation(s)
- Mi Hyeon Cho
- Center for Nanomedicine, Institute for Basic Science (IBS) , Seoul 03722, Republic of Korea
- Yonsei-IBS Institute, Yonsei University , Seoul 03722, Republic of Korea
- Department of Chemistry, Yonsei University , Seoul 03722, Republic of Korea
| | - Seulmi Kim
- Center for Nanomedicine, Institute for Basic Science (IBS) , Seoul 03722, Republic of Korea
- Yonsei-IBS Institute, Yonsei University , Seoul 03722, Republic of Korea
- Department of Chemistry, Yonsei University , Seoul 03722, Republic of Korea
| | - Jae-Hyun Lee
- Center for Nanomedicine, Institute for Basic Science (IBS) , Seoul 03722, Republic of Korea
- Yonsei-IBS Institute, Yonsei University , Seoul 03722, Republic of Korea
- Department of Chemistry, Yonsei University , Seoul 03722, Republic of Korea
| | - Tae-Hyun Shin
- Center for Nanomedicine, Institute for Basic Science (IBS) , Seoul 03722, Republic of Korea
- Yonsei-IBS Institute, Yonsei University , Seoul 03722, Republic of Korea
- Department of Chemistry, Yonsei University , Seoul 03722, Republic of Korea
| | - Dongwon Yoo
- Center for Nanomedicine, Institute for Basic Science (IBS) , Seoul 03722, Republic of Korea
- Yonsei-IBS Institute, Yonsei University , Seoul 03722, Republic of Korea
| | - Jinwoo Cheon
- Center for Nanomedicine, Institute for Basic Science (IBS) , Seoul 03722, Republic of Korea
- Yonsei-IBS Institute, Yonsei University , Seoul 03722, Republic of Korea
- Department of Chemistry, Yonsei University , Seoul 03722, Republic of Korea
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34
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Esser L, Shukla S, Zhou F, Ambudkar SV, Xia D. Crystal structure of the antigen-binding fragment of a monoclonal antibody specific for the multidrug-resistance-linked ABC transporter human P-glycoprotein. Acta Crystallogr F Struct Biol Commun 2016; 72:636-41. [PMID: 27487928 PMCID: PMC4973305 DOI: 10.1107/s2053230x16009778] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 06/16/2016] [Indexed: 12/19/2022] Open
Abstract
P-glycoprotein (P-gp) is a polyspecific ATP-dependent transporter linked to multidrug resistance in cancers that plays important roles in the pharmacokinetics of a large number of drugs. The drug-resistance phenotype of P-gp can be modulated by the monoclonal antibody UIC2, which specifically recognizes human P-gp in a conformation-dependent manner. Here, the purification, sequence determination and high-resolution structure of the Fab fragment of UIC2 (UIC2/Fab) are reported. Purified UIC2/Fab binds human P-gp with a 1:1 stoichiometry. Crystals of UIC2/Fab are triclinic (space group P1), with unit-cell parameters a = 40.67, b = 44.91, c = 58.09 Å, α = 97.62, β = 99.10, γ = 94.09°, and diffracted X-rays to 1.6 Å resolution. The structure was determined by molecular replacement and refined to 1.65 Å resolution. The asymmetric unit contains one molecule of UIC2/Fab, which exhibits a positively charged antigen-binding surface, suggesting that it might recognize an oppositely charged extracellular epitope of P-gp.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Amino Acid Motifs
- Animals
- Antibodies, Monoclonal/biosynthesis
- Antibodies, Monoclonal/chemistry
- Antibodies, Monoclonal/isolation & purification
- Antigens/chemistry
- Antigens/metabolism
- Binding Sites
- Cloning, Molecular
- Crystallography, X-Ray
- Gene Expression
- Humans
- Hybridomas/chemistry
- Immunoglobulin Fab Fragments/biosynthesis
- Immunoglobulin Fab Fragments/chemistry
- Immunoglobulin Fab Fragments/isolation & purification
- Mice
- Mice, Inbred BALB C
- Models, Molecular
- Protein Binding
- Protein Interaction Domains and Motifs
- Protein Structure, Secondary
- Recombinant Proteins/biosynthesis
- Recombinant Proteins/chemistry
- Recombinant Proteins/isolation & purification
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Affiliation(s)
- Lothar Esser
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Suneet Shukla
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Fei Zhou
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Suresh V. Ambudkar
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
| | - Di Xia
- National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Bethesda, MD 20892, USA
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35
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Overcoming ABC transporter-mediated multidrug resistance: Molecular mechanisms and novel therapeutic drug strategies. Drug Resist Updat 2016; 27:14-29. [DOI: 10.1016/j.drup.2016.05.001] [Citation(s) in RCA: 452] [Impact Index Per Article: 56.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2015] [Revised: 04/24/2016] [Accepted: 05/06/2016] [Indexed: 12/15/2022]
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36
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A single active catalytic site is sufficient to promote transport in P-glycoprotein. Sci Rep 2016; 6:24810. [PMID: 27117502 PMCID: PMC4846820 DOI: 10.1038/srep24810] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 04/05/2016] [Indexed: 11/23/2022] Open
Abstract
P-glycoprotein (Pgp) is an ABC transporter responsible for the ATP-dependent efflux of chemotherapeutic compounds from multidrug resistant cancer cells. Better understanding of the molecular mechanism of Pgp-mediated transport could promote rational drug design to circumvent multidrug resistance. By measuring drug binding affinity and reactivity to a conformation-sensitive antibody we show here that nucleotide binding drives Pgp from a high to a low substrate-affinity state and this switch coincides with the flip from the inward- to the outward-facing conformation. Furthermore, the outward-facing conformation survives ATP hydrolysis: the post-hydrolytic complex is stabilized by vanadate, and the slow recovery from this state requires two functional catalytic sites. The catalytically inactive double Walker A mutant is stabilized in a high substrate affinity inward-open conformation, but mutants with one intact catalytic center preserve their ability to hydrolyze ATP and to promote drug transport, suggesting that the two catalytic sites are randomly recruited for ATP hydrolysis.
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37
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The Metastatic Potential and Chemoresistance of Human Pancreatic Cancer Stem Cells. PLoS One 2016; 11:e0148807. [PMID: 26859746 PMCID: PMC4747523 DOI: 10.1371/journal.pone.0148807] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 01/22/2016] [Indexed: 01/26/2023] Open
Abstract
Cancer stem cells (CSCs) typically have the capacity to evade chemotherapy and may be the principal source of metastases. CSCs for human pancreatic ductal carcinoma (PDAC) have been identified, but neither the metastatic potential nor the chemoresistance of these cells has been adequately evaluated. We have addressed these issues by examining side-population (SP) cells isolated from the Panc-1 and BxPC3 lines of human PDAC cells, the oncogenotypes of which differ. SP cells could be isolated from monolayers of Panc-1, but only from spheroids of BxPC3. Using orthotopic xenografts into the severely immunocompromised NSG mouse, we found that SP cells isolated from both cell lines produced tumors that were highly metastatic, in contrast to previous experience with PDAC cell lines. SP cells derived from both cell lines expressed the ABCG2 transporter, which was demonstrably responsible for the SP phenotype. SP cells gave rise to non-SP (NSP) cells in vitro and in vivo, a transition that was apparently due to posttranslational inhibition of the ABCG2 transporter. Twenty-two other lines of PDAC cells also expressed ABCG2. The sensitivity of PDAC SP cells to the vinca alkaloid vincristine could be greatly increased by verapamil, a general inhibitor of transporters. In contrast, verapamil had no effect on the killing of PDAC cells by gemcitabine, the current first-line therapeutic for PDAC. We conclude that the isolation of SP cells can be a convenient and effective tool for the study of PDAC CSCs; that CSCs may be the principal progenitors of metastasis by human PDAC; that the ABCG2 transporter is responsible for the SP phenotype in human PDAC cells, and may be a ubiquitous source of drug-resistance in PDAC, but does not confer resistance to gemcitabine; and that inhibition of ABCG2 might offer a useful adjunct in a therapeutic attack on the CSCs of PDAC.
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38
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Apáti Á, Szebényi K, Erdei Z, Várady G, Orbán TI, Sarkadi B. The importance of drug transporters in human pluripotent stem cells and in early tissue differentiation. Expert Opin Drug Metab Toxicol 2015; 12:77-92. [DOI: 10.1517/17425255.2016.1121382] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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39
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Discovery of substituted 1,4-dihydroquinolines as novel promising class of P-glycoprotein inhibitors: First structure–activity relationships and bioanalytical studies. Bioorg Med Chem Lett 2015; 25:3005-8. [DOI: 10.1016/j.bmcl.2015.05.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/07/2015] [Accepted: 05/11/2015] [Indexed: 11/21/2022]
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40
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Liang X, Xu X, Wang F, Li N, He J. E-cadherin increasing multidrug resistance protein 1 via hypoxia-inducible factor-1α contributes to multicellular resistance in colorectal cancer. Tumour Biol 2015. [PMID: 26219897 DOI: 10.1007/s13277-015-3811-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
When cancer cells have been cultured as three-dimensional (3D) cultures or in vivo, they decrease sensitivity to anticancer drugs. This is called multicellular resistance, and the mechanism is not fully understood. Here, we report that E-cadherin increasing multidrug resistance protein 1 (MDR1) via hypoxia-inducible factor-1α (HIF-1α) contributes to multicellular resistance in colorectal cancer. The MDR1 protein level was higher in 3D cultures than in monolayer cells. When dispersed cells from 3D cultures were grown as monolayer cells again, the MDR1 protein level decreased to the similar level of cells maintained as monolayer all through. Knockdown of MDR1 significantly decreased multicellular resistance. Knockdown of E-cadherin decreased MDR1 in 3D cultures but did not detectably change MDR1 in monolayer cells. E-cadherin was expressed uniformly in 3D cultures while the MDR1 protein level was higher in the center of 3D cultures than in the peripheral part. Knockdown of E-cadherin decreased E-cadherin uniformly in 3D cultures but mainly decreased MDR1 at the center of 3D cultures. These suggest that knockdown of E-cadherin decreasing MDR1 may be by an indirect mechanism. HIF-1α was remarkably increased in 3D cultures. Knockdown of E-cadherin decreased intercellular junctions, increased intercellular space, and decreased HIF-1α in 3D cultures. Knockdown of HIF-1α decreased MDR1 in 3D cultures. Knockdown of E-cadherin increased β-catenin uniformly in 3D cultures, and knockdown of β-catenin decreased MDR1 what was opposite to knockdown of E-cadherin decreasing MDR1. Our data reveal that knockdown of E-cadherin decreasing MDR1 via HIF-1α is involved in the mechanism of multicellular resistance in colorectal cancer. Though β-catenin is also involved in the mechanism, it does not play a dominant role.
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Affiliation(s)
- Xi Liang
- Department of Oncology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.,Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, 400042, China
| | - Xueqing Xu
- Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Daping Hospital, Third Military Medical University, Chongqing, 400042, China
| | - Fengchao Wang
- Institute of Combined Injury, State Key Laboratory of Trauma, Burns and Combined Injury, Third Military Medical University, Chongqing, 400038, China
| | - Ni Li
- Department of Oncology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China
| | - Jianming He
- Department of Oncology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University, Chongqing, 400038, China.
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41
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Punfa W, Suzuki S, Pitchakarn P, Yodkeeree S, Naiki T, Takahashi S, Limtrakul P. Curcumin-loaded PLGA nanoparticles conjugated with anti- P-glycoprotein antibody to overcome multidrug resistance. Asian Pac J Cancer Prev 2015; 15:9249-58. [PMID: 25422208 DOI: 10.7314/apjcp.2014.15.21.9249] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The encapsulation of curcumin (Cur) in polylactic-co-glycolic acid (PLGA) nanoparticles (Cur- NPs) was designed to improve its solubility and stability. Conjugation of the Cur-NPs with anti-P-glycoprotein (P-gp) antibody (Cur-NPs-APgp) may increase their targeting to P-gp, which is highly expressed in multidrug- resistance (MDR) cancer cells. This study determined whether Cur-NPs-APgp could overcome MDR in a human cervical cancer model (KB-V1 cells) in vitro and in vivo. MATERIALS AND METHODS First, we determined the MDR- reversing property of Cur in P-gp-overexpressing KB-V1 cells in vitro and in vivo. Cur-NPs and Cur-NPs-APgp, in the range 150-180 nm, were constructed and subjected to an in vivo pharmacokinetic study compared with Cur. The in vitro and in vivo MDR-reversing properties of Cur-NPs and Cur-NPs-APgp were then investigated. Moreover, the stability of the NPs was determined in various solutions. RESULTS The combined treatment of paclitaxel (PTX) with Cur dramatically decreased cell viability and tumor growth compared to PTX treatment alone. After intravenous injection, Cur-NPs-APgp and Cur-NPs could be detected in the serum up to 60 and 120 min later, respectively, whereas Cur was not detected after 30 min. Pretreatment with Cur-NPs-APgp, but not with NPs or Cur-NPs, could enhance PTX sensitivity both in vitro and in vivo. The constructed NPs remained a consistent size, proving their stability in various solutions. CONCLUSIONS Our functional Cur-NPs-APgp may be a suitable candidate for application in a drug delivery system for overcoming drug resistance. The further development of Cur-NPs-APgp may be beneficial to cancer patients by leading to its use as either as a MDR modulator or as an anticancer drug.
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Affiliation(s)
- Wanisa Punfa
- Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand E-mail :
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42
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Yuan Y, Wang L, Du W, Ding Z, Zhang J, Han T, An L, Zhang H, Liang G. Intracellular Self-Assembly of Taxol Nanoparticles for Overcoming Multidrug Resistance. Angew Chem Int Ed Engl 2015; 54:9700-4. [DOI: 10.1002/anie.201504329] [Citation(s) in RCA: 165] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Indexed: 12/19/2022]
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43
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Yuan Y, Wang L, Du W, Ding Z, Zhang J, Han T, An L, Zhang H, Liang G. Intracellular Self-Assembly of Taxol Nanoparticles for Overcoming Multidrug Resistance. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201504329] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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44
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Ween MP, Armstrong MA, Oehler MK, Ricciardelli C. The role of ABC transporters in ovarian cancer progression and chemoresistance. Crit Rev Oncol Hematol 2015; 96:220-56. [PMID: 26100653 DOI: 10.1016/j.critrevonc.2015.05.012] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 04/08/2015] [Accepted: 05/18/2015] [Indexed: 02/06/2023] Open
Abstract
Over 80% of ovarian cancer patients develop chemoresistance which results in a lethal course of the disease. A well-established cause of chemoresistance involves the family of ATP-binding cassette transporters, or ABC transporters that transport a wide range of substrates including metabolic products, nutrients, lipids, and drugs across extra- and intra-cellular membranes. Expressions of various ABC transporters, shown to reduce the intracellular accumulation of chemotherapy drugs, are increased following chemotherapy and impact on ovarian cancer survival. Although clinical trials to date using ABC transporter inhibitors have been disappointing, ABC transporter inhibition remains an attractive potential adjuvant to chemotherapy. A greater understanding of their physiological functions and role in ovarian cancer chemoresistance will be important for the development of more effective targeted therapies. This article will review the role of the ABC transporter family in ovarian cancer progression and chemoresistance as well as the clinical attempts used to date to reverse chemoresistance.
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Affiliation(s)
- M P Ween
- Lung Research, Hanson Institute and Department of Thoracic Medicine, Royal Adelaide Hospital, Adelaide
| | - M A Armstrong
- Data Management and Analysis Centre, University of Adelaide, Australia
| | - M K Oehler
- Gynaecological Oncology Department, Royal Adelaide Hospital, Australia; School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Australia
| | - C Ricciardelli
- School of Paediatrics and Reproductive Health, Robinson Research Institute, University of Adelaide, Australia.
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45
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Kartal-Yandim M, Adan-Gokbulut A, Baran Y. Molecular mechanisms of drug resistance and its reversal in cancer. Crit Rev Biotechnol 2015; 36:716-26. [DOI: 10.3109/07388551.2015.1015957] [Citation(s) in RCA: 198] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Melis Kartal-Yandim
- Department of Molecular Biology and Genetics, İzmir Institute of Technology, Urla, İzmir, Turkey and
| | - Aysun Adan-Gokbulut
- Department of Molecular Biology and Genetics, İzmir Institute of Technology, Urla, İzmir, Turkey and
| | - Yusuf Baran
- Department of Molecular Biology and Genetics, İzmir Institute of Technology, Urla, İzmir, Turkey and
- Faculty of Life and Natural Sciences, Abdullah Gul University, Kayseri, Turkey
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46
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Abstract
Since over 50 years, 5-fluorouracil (5-FU) is in use as backbone of chemotherapy treatment regimens for a wide range of cancers including colon, breast, and head and neck carcinomas. However, drug resistance and severe toxicities such as mucositis, diarrhea, neutropenia, and vomiting in up to 40% of treated patients often lead to dose limitation or treatment discontinuation. Because the oral bioavailability of 5-FU is unpredictable and highly variable, 5-FU is commonly administered intravenously. To overcome medical complications and inconvenience associated with intravenous administration, the oral prodrugs capecitabine and tegafur have been developed. Both fluoropyrimidines are metabolically converted intracellularly to 5-FU, which then needs metabolic activation to exert its damaging activity on RNA and DNA. The low response rates of 10-15% of 5-FU monotherapy can be improved by combination regimens of infusional 5-FU and leucovorin together with oxaliplatin (FOLFOX) or irinotecan (FOLFIRI), thereby increasing response rates to 30-40%. The impact of metabolizing enzymes in the development of fluoropyrimidine toxicity and resistance has been studied in great detail. In addition, membrane drug transporters, which are critical determinants of intracellular drug concentrations, may play a role in occurrence of toxicity and development of resistance against fluoropyrimidine-based therapy as well. This review therefore summarizes current knowledge on the role of drug transporters with particular focus on ATP-binding cassette transporters in fluoropyrimidine-based chemotherapy response.
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47
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Zeino M, Paulsen MS, Zehl M, Urban E, Kopp B, Efferth T. Identification of new P-glycoprotein inhibitors derived from cardiotonic steroids. Biochem Pharmacol 2014; 93:11-24. [PMID: 25451686 DOI: 10.1016/j.bcp.2014.10.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 10/22/2014] [Accepted: 10/22/2014] [Indexed: 12/27/2022]
Abstract
P-glycoprotein (ABCB1, MDR1) is capable of extruding chemotherapeutics outside the cell and its overexpression in certain cancer cells may cause failure of chemotherapy. Many attempts were carried out to identify potent inhibitors of this transporter and numerous compounds were shown to exert inhibitory effects in vitro, but so far none were able to make their way to the clinic due to serious complications. Natural compounds represent a great source of therapeutics, which are believed to be safe and effective. Therefore, we have screened a large library of naturally occurring cardiotonic steroids and their derivatives using high throughput flow cytometry. We were able to identify six compounds capable of modulating P-glycoprotein activity. By using P-glycoprotein ATPase assays, molecular docking in silico studies and resazurin reduction assays, the outcome of this high throughput screening platform has been validated. These novel compounds may serve as candidates to reverse doxorubicin resistance in leukemia cells.
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Affiliation(s)
- Maen Zeino
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz, Germany
| | - Malte S Paulsen
- St. Mary's, Respiratory Infections NHLI, Flow Cytometry Core Facility, Imperial College, London, Great Britain
| | - Martin Zehl
- Department of Pharmacognosy, University of Vienna, Althanstraße 14, 1090 Vienna, Austria; Departments of Pharmaceutical Chemistry, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Ernst Urban
- Departments of Pharmaceutical Chemistry, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Brigitte Kopp
- Department of Pharmacognosy, University of Vienna, Althanstraße 14, 1090 Vienna, Austria
| | - Thomas Efferth
- Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz, Germany.
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48
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Dimeloe S, Frick C, Fischer M, Gubser PM, Razik L, Bantug GR, Ravon M, Langenkamp A, Hess C. Human regulatory T cells lack the cyclophosphamide-extruding transporter ABCB1 and are more susceptible to cyclophosphamide-induced apoptosis. Eur J Immunol 2014; 121:343-56. [PMID: 25251877 DOI: 10.1093/toxsci/kfr071] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
ATP-binding cassette (ABC) transporters, including ABC-transporter B1 (ABCB1), extrude drugs, metabolites, and other compounds (such as mitotracker green (MTG)) from cells. Susceptibility of CD4(+) regulatory T (Treg) cells to the ABCB1-substrate cyclophosphamide (CPA) has been reported. Here, we characterized ABCB1 expression and function in human CD4(+) T-cell subsets. Naïve, central memory, and effector-memory CD4(+) T cells, but not Treg cells, effluxed MTG in an ABCB1-dependent manner. In line with this, ABCB1 mRNA and protein was expressed by nonregulatory CD4(+) T-cell subsets, but not Treg cells. In vitro, the ABCB1-substrate CPA was cytotoxic for Treg cells at a 100-fold lower dose than for nonregulatory counterparts, and, inversely, verapamil, an inhibitor of ABC transporters, increased CPA-toxicity in nonregulatory CD4(+) T cells but not Treg cells. Thus, Treg cells lack expression of ABCB1, rendering them selectively susceptible to CPA. Our findings provide mechanistic support for therapeutic strategies using CPA to boost anti-tumor immunity by selectively depleting Treg cells.
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Affiliation(s)
- Sarah Dimeloe
- Immunobiology, Department of Biomedicine, University Hospital Basel, Basel, Switzerland
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49
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The strong in vivo anti-tumor effect of the UIC2 monoclonal antibody is the combined result of Pgp inhibition and antibody dependent cell-mediated cytotoxicity. PLoS One 2014; 9:e107875. [PMID: 25238617 PMCID: PMC4169599 DOI: 10.1371/journal.pone.0107875] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 08/21/2014] [Indexed: 01/10/2023] Open
Abstract
P-glycoprotein (Pgp) extrudes a large variety of chemotherapeutic drugs from the cells, causing multidrug resistance (MDR). The UIC2 monoclonal antibody recognizes human Pgp and inhibits its drug transport activity. However, this inhibition is partial, since UIC2 binds only to 10-40% of cell surface Pgps, while the rest becomes accessible to this antibody only in the presence of certain substrates or modulators (e.g. cyclosporine A (CsA)). The combined addition of UIC2 and 10 times lower concentrations of CsA than what is necessary for Pgp inhibition when the modulator is applied alone, decreased the EC50 of doxorubicin (DOX) in KB-V1 (Pgp+) cells in vitro almost to the level of KB-3-1 (Pgp-) cells. At the same time, UIC2 alone did not affect the EC50 value of DOX significantly. In xenotransplanted severe combined immunodeficient (SCID) mice co-treated with DOX, UIC2 and CsA, the average weight of Pgp+ tumors was only ∼10% of the untreated control and in 52% of these animals we could not detect tumors at all, while DOX treatment alone did not decrease the weight of Pgp+ tumors. These data were confirmed by visualizing the tumors in vivo by positron emission tomography (PET) based on their increased 18FDG accumulation. Unexpectedly, UIC2+DOX treatment also decreased the size of tumors compared to the DOX only treated animals, as opposed to the results of our in vitro cytotoxicity assays, suggesting that immunological factors are also involved in the antitumor effect of in vivo UIC2 treatment. Since UIC2 binding itself did not affect the viability of Pgp expressing cells, but it triggered in vitro cell killing by peripheral blood mononuclear cells (PBMCs), it is concluded that the impressive in vivo anti-tumor effect of the DOX-UIC2-CsA treatment is the combined result of Pgp inhibition and antibody dependent cell-mediated cytotoxicity (ADCC).
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50
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Loo TW, Clarke DM. Cysteines introduced into extracellular loops 1 and 4 of human P-glycoprotein that are close only in the open conformation spontaneously form a disulfide bond that inhibits drug efflux and ATPase activity. J Biol Chem 2014; 289:24749-58. [PMID: 25053414 DOI: 10.1074/jbc.m114.583021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P-glycoprotein (P-gp) is an ATP-binding cassette drug pump that protects us from toxic compounds and confers multidrug resistance. The protein is organized into two halves. The halves contain a transmembrane domain (TMD) with six transmembrane segments and a nucleotide-binding domain (NBD). The drug- and ATP-binding sites reside at the TMD1/TMD2 and NBD1/NBD2 interfaces, respectively. ATP-dependent drug efflux involves changes between the open inward-facing (NBDs apart, extracellular loops (ECLs) close together) and the closed outward-facing (NBDs close together, ECLs apart) conformations. It is controversial, however, whether the open conformation only exists transiently in intact cells because of the presence of high levels of ATP. To test for the presence of an open conformation in intact cells, reporter cysteines were placed in extracellular loops 1 (A80C, N half) and 4 (R741C, C half). The rationale was that cysteines A80C/R741C would only come close enough to form a disulfide bond in an open conformation (6.9 Å apart) because they are separated widely (30.4 Å apart) in the closed conformation. It was observed that the mutant A80C/R741C cross-linked spontaneously (>90%) when expressed in cells. In contrast to previous reports showing that trapping P-gp in a closed conformation highly activated ATPase activity, here we show that A80C/R741C cross-linking inhibited ATPase activity and drug efflux. Both activities were restored when the cross-linked mutant was treated with a thiol-reducing agent. The results show that an open conformation can be readily detected in cells and that cross-linking of cysteines placed in ECLs 1 and 4 inhibits activity.
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Affiliation(s)
- Tip W Loo
- From the Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - David M Clarke
- From the Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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