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Nikitin SE, Fåk B, Krämer KW, Fennell T, Normand B, Läuchli AM, Rüegg C. Thermal Evolution of Dirac Magnons in the Honeycomb Ferromagnet CrBr_{3}. Phys Rev Lett 2022; 129:127201. [PMID: 36179160 DOI: 10.1103/physrevlett.129.127201] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 08/17/2022] [Indexed: 06/16/2023]
Abstract
CrBr_{3} is an excellent realization of the two-dimensional honeycomb ferromagnet, which offers a bosonic equivalent of graphene with Dirac magnons and topological character. We perform inelastic neutron scattering measurements using state-of-the-art instrumentation to update 50-year-old data, thereby enabling a definitive comparison both with recent experimental claims of a significant gap at the Dirac point and with theoretical predictions for thermal magnon renormalization. We demonstrate that CrBr_{3} has next-neighbor J_{2} and J_{3} interactions approximately 5% of J_{1}, an ideal Dirac magnon dispersion at the K point, and the associated signature of isospin winding. The magnon lifetime and the thermal band renormalization show the universal T^{2} evolution expected from an interacting spin-wave treatment, but the measured dispersion lacks the predicted van Hove features, pointing to the need for more sophisticated theoretical analysis.
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Affiliation(s)
- S E Nikitin
- Quantum Criticality and Dynamics Group, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - B Fåk
- Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, F-38042 Grenoble Cedex 9, France
| | - K W Krämer
- Department of Chemistry, Biochemistry and Pharmacy, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - T Fennell
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - B Normand
- Laboratory for Theoretical and Computational Physics, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - A M Läuchli
- Laboratory for Theoretical and Computational Physics, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Ch Rüegg
- Quantum Criticality and Dynamics Group, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Hönggerberg, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
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2
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Jiménez JL, Crone SPG, Fogh E, Zayed ME, Lortz R, Pomjakushina E, Conder K, Läuchli AM, Weber L, Wessel S, Honecker A, Normand B, Rüegg C, Corboz P, Rønnow HM, Mila F. A quantum magnetic analogue to the critical point of water. Nature 2021; 592:370-375. [PMID: 33854247 DOI: 10.1038/s41586-021-03411-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/26/2021] [Indexed: 02/02/2023]
Abstract
At the liquid-gas phase transition in water, the density has a discontinuity at atmospheric pressure; however, the line of these first-order transitions defined by increasing the applied pressure terminates at the critical point1, a concept ubiquitous in statistical thermodynamics2. In correlated quantum materials, it was predicted3 and then confirmed experimentally4,5 that a critical point terminates the line of Mott metal-insulator transitions, which are also first-order with a discontinuous charge carrier density. In quantum spin systems, continuous quantum phase transitions6 have been controlled by pressure7,8, applied magnetic field9,10 and disorder11, but discontinuous quantum phase transitions have received less attention. The geometrically frustrated quantum antiferromagnet SrCu2(BO3)2 constitutes a near-exact realization of the paradigmatic Shastry-Sutherland model12-14 and displays exotic phenomena including magnetization plateaus15, low-lying bound-state excitations16, anomalous thermodynamics17 and discontinuous quantum phase transitions18,19. Here we control both the pressure and the magnetic field applied to SrCu2(BO3)2 to provide evidence of critical-point physics in a pure spin system. We use high-precision specific-heat measurements to demonstrate that, as in water, the pressure-temperature phase diagram has a first-order transition line that separates phases with different local magnetic energy densities, and that terminates at an Ising critical point. We provide a quantitative explanation of our data using recently developed finite-temperature tensor-network methods17,20-22. These results further our understanding of first-order quantum phase transitions in quantum magnetism, with potential applications in materials where anisotropic spin interactions produce the topological properties23,24 that are useful for spintronic applications.
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Affiliation(s)
- J Larrea Jiménez
- Laboratory for Quantum Matter under Extreme Conditions, Institute of Physics, University of São Paulo, São Paulo, Brazil.,Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - S P G Crone
- Institute for Theoretical Physics, University of Amsterdam, Amsterdam, The Netherlands.,Delta Institute for Theoretical Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - E Fogh
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - M E Zayed
- Department of Physics, Carnegie Mellon University in Qatar, Doha, Qatar
| | - R Lortz
- Department of Physics, Hong Kong University of Science and Technology, Kowloon, Hong Kong
| | - E Pomjakushina
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, Villigen-PSI, Switzerland
| | - K Conder
- Laboratory for Multiscale Materials Experiments, Paul Scherrer Institute, Villigen-PSI, Switzerland
| | - A M Läuchli
- Institut für Theoretische Physik, Universität Innsbruck, Innsbruck, Austria
| | - L Weber
- Institut für Theoretische Festkörperphysik, RWTH Aachen University, Aachen, Germany
| | - S Wessel
- Institut für Theoretische Festkörperphysik, RWTH Aachen University, Aachen, Germany
| | - A Honecker
- Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, CY Cergy Paris Université, Cergy-Pontoise, France
| | - B Normand
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Paul Scherrer Institute, Villigen-PSI, Switzerland
| | - Ch Rüegg
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.,Paul Scherrer Institute, Villigen-PSI, Switzerland.,Institute for Quantum Electronics, ETH Zürich, Hönggerberg, Switzerland.,Department of Quantum Matter Physics, University of Geneva, Geneva, Switzerland
| | - P Corboz
- Institute for Theoretical Physics, University of Amsterdam, Amsterdam, The Netherlands.,Delta Institute for Theoretical Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - H M Rønnow
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
| | - F Mila
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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3
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Mena M, Hänni N, Ward S, Hirtenlechner E, Bewley R, Hubig C, Schollwöck U, Normand B, Krämer KW, McMorrow DF, Rüegg C. Thermal Control of Spin Excitations in the Coupled Ising-Chain Material RbCoCl_{3}. Phys Rev Lett 2020; 124:257201. [PMID: 32639763 DOI: 10.1103/physrevlett.124.257201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 05/27/2020] [Indexed: 06/11/2023]
Abstract
We have used neutron spectroscopy to investigate the spin dynamics of the quantum (S=1/2) antiferromagnetic Ising chains in RbCoCl_{3}. The structure and magnetic interactions in this material conspire to produce two magnetic phase transitions at low temperatures, presenting an ideal opportunity for thermal control of the chain environment. The high-resolution spectra we measure of two-domain-wall excitations therefore characterize precisely both the continuum response of isolated chains and the "Zeeman-ladder" bound states of chains in three different effective staggered fields in one and the same material. We apply an extended Matsubara formalism to obtain a quantitative description of the entire dataset, Monte Carlo simulations to interpret the magnetic order, and finite-temperature density-matrix renormalization-group calculations to fit the spectral features of all three phases.
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Affiliation(s)
- M Mena
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - N Hänni
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
- Physikalisches Institut, University of Bern, Siedlerstrasse 5, CH-3012 Bern, Switzerland
| | - S Ward
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva 4, Switzerland
| | - E Hirtenlechner
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institut Laue Langevin, CS 20156, F-38042 Grenoble, France
| | - R Bewley
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - C Hubig
- Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-University Munich, 80333 München, Germany
- Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany
| | - U Schollwöck
- Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-University Munich, 80333 München, Germany
| | - B Normand
- Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - K W Krämer
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - D F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
| | - Ch Rüegg
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva 4, Switzerland
- Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland
- Institute of Physics, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland
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4
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Allenspach S, Biffin A, Stuhr U, Tucker GS, Ohira-Kawamura S, Kofu M, Voneshen DJ, Boehm M, Normand B, Laflorencie N, Mila F, Rüegg C. Multiple Magnetic Bilayers and Unconventional Criticality without Frustration in BaCuSi_{2}O_{6}. Phys Rev Lett 2020; 124:177205. [PMID: 32412274 DOI: 10.1103/physrevlett.124.177205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 03/18/2020] [Indexed: 06/11/2023]
Abstract
The dimerized quantum magnet BaCuSi_{2}O_{6} was proposed as an example of "dimensional reduction" arising near the magnetic-field-induced quantum critical point (QCP) due to perfect geometrical frustration of its interbilayer interactions. We demonstrate by high-resolution neutron spectroscopy experiments that the effective intrabilayer interactions are ferromagnetic, thereby excluding frustration. We explain the apparent dimensional reduction by establishing the presence of three magnetically inequivalent bilayers, with ratios 3∶2∶1, whose differing interaction parameters create an extra field-temperature scaling regime near the QCP with a nontrivial but nonuniversal exponent. We demonstrate by detailed quantum Monte Carlo simulations that the magnetic interaction parameters we deduce can account for all the measured properties of BaCuSi_{2}O_{6}, opening the way to a quantitative understanding of nonuniversal scaling in any modulated layered system.
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Affiliation(s)
- S Allenspach
- Neutrons and Muons Research Division, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | - A Biffin
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - U Stuhr
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - G S Tucker
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - S Ohira-Kawamura
- J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - M Kofu
- J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - D J Voneshen
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
| | - M Boehm
- Institut Laue Langevin, 6 Rue Jules Horowitz BP156, 38024 Grenoble Cedex 9, France
| | - B Normand
- Neutrons and Muons Research Division, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
| | - N Laflorencie
- Laboratoire de Physique Théorique, CNRS and Université de Toulouse, 31062 Toulouse, France
| | - F Mila
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Ch Rüegg
- Neutrons and Muons Research Division, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
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5
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Wehinger B, Fiolka C, Lanza A, Scatena R, Kubus M, Grockowiak A, Coniglio WA, Graf D, Skoulatos M, Chen JH, Gukelberger J, Casati N, Zaharko O, Macchi P, Krämer KW, Tozer S, Mudry C, Normand B, Rüegg C. Giant Pressure Dependence and Dimensionality Switching in a Metal-Organic Quantum Antiferromagnet. Phys Rev Lett 2018; 121:117201. [PMID: 30265101 DOI: 10.1103/physrevlett.121.117201] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Indexed: 06/08/2023]
Abstract
We report an extraordinary pressure dependence of the magnetic interactions in the metal-organic system [CuF_{2}(H_{2}O)_{2}]_{2}pyrazine. At zero pressure, this material realizes a quasi-two-dimensional spin-1/2 square-lattice Heisenberg antiferromagnet. By high-pressure, high-field susceptibility measurements we show that the dominant exchange parameter is reduced continuously by a factor of 2 on compression. Above 18 kbar, a phase transition occurs, inducing an orbital re-ordering that switches the dimensionality, transforming the quasi-two-dimensional lattice into weakly coupled chains. We explain the microscopic mechanisms for both phenomena by combining detailed x-ray and neutron diffraction studies with quantitative modeling using spin-polarized density functional theory.
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Affiliation(s)
- B Wehinger
- Department of Quantum Matter Physics, University of Geneva, 24, Quai Ernest Ansermet, CH-1211 Genève, Switzerland
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - C Fiolka
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - A Lanza
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - R Scatena
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - M Kubus
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - A Grockowiak
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, USA
| | - W A Coniglio
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, USA
| | - D Graf
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, USA
| | - M Skoulatos
- Heinz-Maier-Leibnitz Zentrum and Physics Department, Technische Universität München, Lichtenbergstrasse 1, 85748 Garching, Germany
| | - J-H Chen
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
- Theoretical Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - J Gukelberger
- Theoretical Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Département de Physique and Institut Quantique, Université de Sherbrooke, Sherbrooke, Québec, J1K 2R1, Canada
| | - N Casati
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - O Zaharko
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - P Macchi
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - K W Krämer
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - S Tozer
- National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, USA
| | - C Mudry
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - B Normand
- Neutrons and Muons Research Division, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - Ch Rüegg
- Department of Quantum Matter Physics, University of Geneva, 24, Quai Ernest Ansermet, CH-1211 Genève, Switzerland
- Neutrons and Muons Research Division, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
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6
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Kuonen F, Kuonen I, Dontenwill M, Rüegg C, Oro A, Gilliet M, Gaide O. 844 Identification of a novel pathway linking TGF-β, fibronectin and integrin α5β1 that promotes invasion in basal cell carcinoma. J Invest Dermatol 2018. [DOI: 10.1016/j.jid.2018.03.855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Gao S, Zaharko O, Tsurkan V, Prodan L, Riordan E, Lago J, Fåk B, Wildes AR, Koza MM, Ritter C, Fouquet P, Keller L, Canévet E, Medarde M, Blomgren J, Johansson C, Giblin SR, Vrtnik S, Luzar J, Loidl A, Rüegg C, Fennell T. Dipolar Spin Ice States with a Fast Monopole Hopping Rate in CdEr_{2}X_{4} (X=Se, S). Phys Rev Lett 2018; 120:137201. [PMID: 29694199 DOI: 10.1103/physrevlett.120.137201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Indexed: 06/08/2023]
Abstract
Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr_{2}Se_{4} is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy_{2}Ti_{2}O_{7}. In this Letter we use diffuse neutron scattering to show that both CdEr_{2}Se_{4} and CdEr_{2}S_{4} support a dipolar spin ice state-the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy_{2}Ti_{2}O_{7}, i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er^{3+} ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr_{2}X_{4} (X=Se, S) are primarily due to much faster monopole hopping. Our work suggests that CdEr_{2}X_{4} offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples.
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Affiliation(s)
- Shang Gao
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | - O Zaharko
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - V Tsurkan
- Experimental Physics V, University of Augsburg, D-86135 Augsburg, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028 Chisinau, Republic of Moldova
| | - L Prodan
- Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028 Chisinau, Republic of Moldova
| | - E Riordan
- School of Physics and Astronomy, Cardiff University, CF24 3AA Cardiff, United Kingdom
| | - J Lago
- Department of Inorganic Chemistry, Universidad del País Vasco (UPV-EHU), 48080 Bilbao, Spain
| | - B Fåk
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - A R Wildes
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - M M Koza
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - C Ritter
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - P Fouquet
- Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France
| | - L Keller
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - E Canévet
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Physics, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - M Medarde
- Laboratory for Scientific Developments and Novel Materials, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - J Blomgren
- RISE Acreo AB, SE-411 33 Göteborg, Sweden
| | | | - S R Giblin
- School of Physics and Astronomy, Cardiff University, CF24 3AA Cardiff, United Kingdom
| | - S Vrtnik
- Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - J Luzar
- Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - A Loidl
- Experimental Physics V, University of Augsburg, D-86135 Augsburg, Germany
| | - Ch Rüegg
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | - T Fennell
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
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8
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Ward S, Mena M, Bouillot P, Kollath C, Giamarchi T, Schmidt KP, Normand B, Krämer KW, Biner D, Bewley R, Guidi T, Boehm M, McMorrow DF, Rüegg C. Bound States and Field-Polarized Haldane Modes in a Quantum Spin Ladder. Phys Rev Lett 2017; 118:177202. [PMID: 28498681 DOI: 10.1103/physrevlett.118.177202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Indexed: 06/07/2023]
Abstract
The challenge of one-dimensional systems is to understand their physics beyond the level of known elementary excitations. By high-resolution neutron spectroscopy in a quantum spin-ladder material, we probe the leading multiparticle excitation by characterizing the two-magnon bound state at zero field. By applying high magnetic fields, we create and select the singlet (longitudinal) and triplet (transverse) excitations of the fully spin-polarized ladder, which have not been observed previously and are close analogs of the modes anticipated in a polarized Haldane chain. Theoretical modeling of the dynamical response demonstrates our complete quantitative understanding of these states.
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Affiliation(s)
- S Ward
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | - M Mena
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | - P Bouillot
- Department of Medical Imaging and Information Sciences, Interventional Neuroradiology Unit, University Hospitals of Geneva, CH-1211 Geneva, Switzerland
- Laboratory for Hydraulic Machines, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - C Kollath
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
- HISKP, University of Bonn, Nussallee 14-16, 53115 Bonn, Germany
| | - T Giamarchi
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
| | - K P Schmidt
- Theoretische Physik I, Staudtstrasse 7, FAU Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - B Normand
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - K W Krämer
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
| | - D Biner
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
| | - R Bewley
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxford OX11 0QX, United Kingdom
| | - T Guidi
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxford OX11 0QX, United Kingdom
| | - M Boehm
- Institut Laue Langevin, 6 rue Jules Horowitz BP156, 38024 Grenoble CEDEX 9, France
| | - D F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - Ch Rüegg
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland
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9
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Biffin A, Rüegg C, Embs J, Guidi T, Cheptiakov D, Loidl A, Tsurkan V, Coldea R. Magnetic Field Dependence of Excitations Near Spin-Orbital Quantum Criticality. Phys Rev Lett 2017; 118:067205. [PMID: 28234545 DOI: 10.1103/physrevlett.118.067205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Indexed: 06/06/2023]
Abstract
The spinel FeSc_{2}S_{4} has been proposed to realize a near-critical spin-orbital singlet (SOS) state, where entangled spin and orbital moments fluctuate in a global singlet state on the verge of spin and orbital order. Here we report powder inelastic neutron scattering measurements that observe the full bandwidth of magnetic excitations and we find that spin-orbital triplon excitations of an SOS state can capture well key aspects of the spectrum in both zero and applied magnetic fields up to 8.5 T. The observed shift of low-energy spectral weight to higher energies upon increasing applied field is naturally explained by the entangled spin-orbital character of the magnetic states, a behavior that is in strong contrast to spin-only singlet ground state systems, where the spin gap decreases upon increasing applied field.
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Affiliation(s)
- A Biffin
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Ch Rüegg
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
- Department of Quantum Matter Physics, University of Geneva, 1211 Geneva, Switzerland
| | - J Embs
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - T Guidi
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
| | - D Cheptiakov
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - A Loidl
- Experimental Physics 5, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
| | - V Tsurkan
- Experimental Physics 5, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, D-86159 Augsburg, Germany
- Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028 Chisinau, Republic of Moldova
| | - R Coldea
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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Zayed ME, Rüegg C, Strässle T, Stuhr U, Roessli B, Ay M, Mesot J, Link P, Pomjakushina E, Stingaciu M, Conder K, Rønnow HM. Correlated decay of triplet excitations in the Shastry-Sutherland compound SrCu2(BO3)2. Phys Rev Lett 2014; 113:067201. [PMID: 25148346 DOI: 10.1103/physrevlett.113.067201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Indexed: 06/03/2023]
Abstract
The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu(2)(BO(3))(2) is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature, while the integrated spectral weight can be explained by an isolated dimer model up to 10 K. Analyzing this anomalous spectral line shape in terms of damped harmonic oscillators shows that the observed damping is due to a two-component process: one component remains sharp and resolution limited while the second broadens. We explain the underlying mechanism through a simple yet quantitatively accurate model of correlated decay of triplons: an excited triplon is long lived if no thermally populated triplons are nearby but decays quickly if there are. The phenomenon is a direct consequence of frustration induced triplon localization in the Shastry-Sutherland lattice.
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Affiliation(s)
- M E Zayed
- Department of Mathematics, Statistics and Physics, College of Arts and Science, Qatar University, P.O. Box 2713, Doha, Qatar and Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland and Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Ch Rüegg
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland and DPMC-MaNEP, University of Geneva, CH-1211 Geneva, Switzerland and London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - Th Strässle
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - U Stuhr
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - B Roessli
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M Ay
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - J Mesot
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland and Laboratory for Neutron and Synchrotron Spectroscopy, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland and Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - P Link
- Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-2), D-85747 Garching, Germany
| | - E Pomjakushina
- Laboratory for Developments and Methods, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - M Stingaciu
- Laboratory for Developments and Methods, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - K Conder
- Laboratory for Developments and Methods, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - H M Rønnow
- Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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11
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Mena M, Perry RS, Perring TG, Le MD, Guerrero S, Storni M, Adroja DT, Rüegg C, McMorrow DF. Spin-wave spectrum of the quantum ferromagnet on the pyrochlore lattice Lu2V2O7. Phys Rev Lett 2014; 113:047202. [PMID: 25105649 DOI: 10.1103/physrevlett.113.047202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Indexed: 06/03/2023]
Abstract
Neutron inelastic scattering has been used to probe the spin dynamics of the quantum (S=1/2) ferromagnet on the pyrochlore lattice Lu(2)V(2)O(7). Well-defined spin waves are observed at all energies and wave vectors, allowing us to determine the parameters of the Hamiltonian of the system. The data are found to be in excellent overall agreement with a minimal model that includes a nearest-neighbor Heisenberg exchange J = 8.22(2) meV and a Dzyaloshinskii-Moriya interaction (DMI) D = 1.5(1) meV. The large DMI term revealed by our study is broadly consistent with the model originally used to explain the magnon Hall effect in this compound [Onose et al., Science 329, 297 (2010) and Ideue et al., Phys. Rev. B 85, 134411 (2012)]. However, our ratio of D/J = 0.18(1) is roughly half of their value, and is much larger than those found in other theoretical studies [Xiang et al., Phys. Rev. B 83, 174402 (2011) and Mook et al., Phys. Rev. B 89,134409 (2014)].
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Affiliation(s)
- M Mena
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom and Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - R S Perry
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom and Centre for Science at Extreme Conditions, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, Scotland
| | - T G Perring
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom and ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, United Kingdom
| | - M D Le
- Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany
| | - S Guerrero
- Condensed Matter Theory, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - M Storni
- Condensed Matter Theory, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
| | - D T Adroja
- ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, United Kingdom
| | - Ch Rüegg
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland and DPMC-MaNEP, University of Geneva, CH-1211 Geneva 4, Switzerland
| | - D F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
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12
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Nichita C, Ciarloni L, Monnier-Benoit S, Hosseinian S, Dorta G, Rüegg C. A novel gene expression signature in peripheral blood mononuclear cells for early detection of colorectal cancer. Aliment Pharmacol Ther 2014; 39:507-17. [PMID: 24428642 DOI: 10.1111/apt.12618] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 12/06/2013] [Accepted: 12/22/2013] [Indexed: 02/06/2023]
Abstract
BACKGROUND Early detection and treatment of colorectal adenomatous polyps (AP) and colorectal cancer (CRC) is associated with decreased mortality for CRC. However, accurate, non-invasive and compliant tests to screen for AP and early stages of CRC are not yet available. A blood-based screening test is highly attractive due to limited invasiveness and high acceptance rate among patients. AIM To demonstrate whether gene expression signatures in the peripheral blood mononuclear cells (PBMC) were able to detect the presence of AP and early stages CRC. METHODS A total of 85 PBMC samples derived from colonoscopy-verified subjects without lesion (controls) (n = 41), with AP (n = 21) or with CRC (n = 23) were used as training sets. A 42-gene panel for CRC and AP discrimination, including genes identified by Digital Gene Expression-tag profiling of PBMC, and genes previously characterised and reported in the literature, was validated on the training set by qPCR. Logistic regression analysis followed by bootstrap validation determined CRC- and AP-specific classifiers, which discriminate patients with CRC and AP from controls. RESULTS The CRC and AP classifiers were able to detect CRC with a sensitivity of 78% and AP with a sensitivity of 46% respectively. Both classifiers had a specificity of 92% with very low false-positive detection when applied on subjects with inflammatory bowel disease (n = 23) or tumours other than CRC (n = 14). CONCLUSION This pilot study demonstrates the potential of developing a minimally invasive, accurate test to screen patients at average risk for colorectal cancer, based on gene expression analysis of peripheral blood mononuclear cells obtained from a simple blood sample.
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Affiliation(s)
- C Nichita
- Gastroenterology and Hepatology Department, Centre Hospitalier Universitaire Vaudois (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
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13
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Lanza A, Fiolka C, Fisch M, Casati N, Skoulatos M, Rüegg C, Krämer KW, Macchi P. New magnetic frameworks of [(CuF2(H2O)2)x(pyz)]. Chem Commun (Camb) 2014; 50:14504-7. [DOI: 10.1039/c4cc06696k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The magnetic exchange in mono- or bi-layer Cu-based coordination polymers is tuned by pressure.
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Affiliation(s)
- A. Lanza
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern, Switzerland
- Swiss Light Source, Paul Scherrer Institute
- CH-5232 Villigen, Switzerland
| | - C. Fiolka
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern, Switzerland
| | - M. Fisch
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern, Switzerland
- Swiss Light Source, Paul Scherrer Institute
- CH-5232 Villigen, Switzerland
| | - N. Casati
- Swiss Light Source, Paul Scherrer Institute
- CH-5232 Villigen, Switzerland
| | - M. Skoulatos
- Laboratory for Neutron Scattering and Imaging
- Paul Scherrer Institute
- CH-5232 Villigen, Switzerland
| | - C. Rüegg
- Laboratory for Neutron Scattering and Imaging
- Paul Scherrer Institute
- CH-5232 Villigen, Switzerland
- DPMC-MaNEP
- University of Geneva
| | - K. W. Krämer
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern, Switzerland
| | - Piero Macchi
- Department of Chemistry and Biochemistry
- University of Bern
- 3012 Bern, Switzerland
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14
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Casola F, Shiroka T, Feiguin A, Wang S, Grbić MS, Horvatić M, Krämer S, Mukhopadhyay S, Conder K, Berthier C, Ott HR, Rønnow HM, Rüegg C, Mesot J. Field-induced quantum soliton lattice in a frustrated two-leg spin-1/2 ladder. Phys Rev Lett 2013; 110:187201. [PMID: 23683239 DOI: 10.1103/physrevlett.110.187201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Indexed: 06/02/2023]
Abstract
Based on high-field (31)P nuclear magnetic resonance experiments and accompanying numerical calculations, it is argued that in the frustrated S=1/2 ladder compound BiCu(2)PO(6) a field-induced soliton lattice develops above a critical field of μ(0)H(c1)=20.96(7) T. Solitons result from the fractionalization of the S=1, bosonlike triplet excitations, which in other quantum antiferromagnets are commonly known to experience Bose-Einstein condensation or to crystallize in a superstructure. Unlike in spin-Peierls systems, these field-induced quantum domain walls do not arise from a state with broken translational symmetry and are triggered exclusively by magnetic frustration. Our model predicts yet another second-order phase transition at H(c2)>H(c1), driven by soliton-soliton interactions, most likely corresponding to the one observed in recent magnetocaloric and other bulk measurements.
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Affiliation(s)
- F Casola
- Laboratorium für Festkörperphysik, ETH Hönggerberg, CH-8093 Zürich, Switzerland.
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15
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Boseggia S, Springell R, Walker HC, Rønnow HM, Rüegg C, Okabe H, Isobe M, Perry RS, Collins SP, McMorrow DF. Robustness of basal-plane antiferromagnetic order and the J(eff)=1/2 state in single-layer iridate spin-orbit Mott insulators. Phys Rev Lett 2013; 110:117207. [PMID: 25166574 DOI: 10.1103/physrevlett.110.117207] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Indexed: 06/03/2023]
Abstract
The magnetic structure and electronic ground state of the layered perovskite Ba(2)IrO(4) have been investigated using x-ray resonant magnetic scattering. Our results are compared with those for Sr(2)IrO(4), for which we provide supplementary data on its magnetic structure. We find that the dominant, long-range antiferromagnetic order is remarkably similar in the two compounds and that the electronic ground state in Ba(2)IrO(4), deduced from an investigation of the x-ray resonant magnetic scattering L(3)/L(2) intensity ratio, is consistent with a J(eff)=1/2 description. The robustness of these two key electronic properties to the considerable structural differences between the Ba and Sr analogues is discussed in terms of the enhanced role of the spin-orbit interaction in 5d transition metal oxides.
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Affiliation(s)
- S Boseggia
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom and Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - R Springell
- Royal Commission for the Exhibition of 1851 Research Fellow, Interface Analysis Centre, University of Bristol, Bristol BS2 8BS, United Kingdom
| | - H C Walker
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - H M Rønnow
- Laboratory for Quantum Magnetism, ICMP, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Ch Rüegg
- Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and DPMC-MaNEP, University of Geneva, CH-1211 Geneva, Switzerland
| | - H Okabe
- National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - M Isobe
- National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - R S Perry
- Scottish Universities Physics Alliance, School of Physics, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - S P Collins
- Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - D F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
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16
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Ward S, Bouillot P, Ryll H, Kiefer K, Krämer KW, Rüegg C, Kollath C, Giamarchi T. Spin ladders and quantum simulators for Tomonaga-Luttinger liquids. J Phys Condens Matter 2013; 25:014004. [PMID: 23221064 DOI: 10.1088/0953-8984/25/1/014004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Magnetic insulators have proven to be usable as quantum simulators for itinerant interacting quantum systems. In particular the compound (C(5)H(12)N)(2)CuBr(4) (for short: (Hpip)(2)CuBr(4)) was shown to be a remarkable realization of a Tomonaga-Luttinger liquid (TLL) and allowed us to quantitatively test the TLL theory. Substitution weakly disorders this class of compounds and thus allows us to use them to tackle questions pertaining to the effect of disorder in TLL as well, such as that of the formation of the Bose glass. In this paper we present, as a first step in this direction, a study of the properties of the related (Hpip)(2)CuCl(4) compound. We determine the exchange couplings and compute the temperature and magnetic field dependence of the specific heat, using a finite temperature density matrix renormalization group procedure. Comparison with the measured specific heat at zero magnetic field confirms the exchange parameters and Hamiltonian for the (Hpip)(2)CuCl(4) compound, giving the basis needed to begin studying the disorder effects.
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Affiliation(s)
- S Ward
- Laboratory for Neutron Scattering, Paul Scherrer Institut, Switzerland
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18
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Buchegger F, Viertl D, Baechler S, Dunet V, Kosinski M, Poitry-Yamate C, Rüegg C, Prior JO. 68Ga-NODAGA-RGDyK for αvβ3 integrin PET imaging. Preclinical investigation and dosimetry. Nuklearmedizin 2011; 50:225-33. [PMID: 21989840 DOI: 10.3413/nukmed-0416-11-06] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 10/08/2011] [Indexed: 11/20/2022]
Abstract
AIM To visualize neovasculature and/or tumour integrin αvβ3 we selected the binding moiety Arg-Gly-Asp-D-Tyr-Lys (RGDyK) coupled to NODAGA for labeling with 68Ga. METHODS NODAGA-RGDyK (ABX) was labeled with the 68Ga eluate from the 68Ge generator IGG100 using the processor unit PharmTracer. Biodistribution was measured in female Hsd mice sacrificed 10, 30, 60 and 90 min after i.v. injection of 68Ga-NODAGA-RGDyK for OLINDA dosimetry extrapolated to humans. Tumour targeting was studied in SCID mice bearing A431 and other tumour transplants using microPET and biodistribution measurements. RESULTS Effective half-life of 68Ga-NODAGA-RGDyK was ~25 min for total body and most organs except liver and spleen that showed stable activity retention. With a bladder voiding interval of 0.5 h the calculated effective dose (ED) was 0.012 and 0.016 mSv/MBq for males and females, respectively. Rapid uptake within 10 min was observed in A431 tumours with dynamic PET followed by a slow release. Biodistribution measurements showed a 68Ga-NODAGA-RGDyK uptake in A431 tumours of 3.4±0.4 and 2.7±0.3%ID/g at 1 and 2 h, respectively. Similar uptakes were observed in a mouse and human breast and ovarian cancer xenografts. Co-injection of excess (5 mg/kg) unlabeled NODAGA-RGDyK with the radiotracer reduced tumour uptake at one hour to 0.23±0.01%ID/g, but similarly decreased uptake in normal organs as well. When unlabeled peptide was injected 15 min after 68Ga-NODAGA-RGDyK, uptake diminished particularly in tumour and adrenals, suggestive of a different binding mode compared with other normal tissues. CONCLUSION NODAGA-RGDyK was reliably labeled with 68Ga and revealed a predicted ED of 0.014 mSv/MBq. Tumour uptake was rapid and significant and was chased with unlabeled RGDyK in a similar manner as adrenal uptake.
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Affiliation(s)
- F Buchegger
- Department of Nuclear Medicine, University Hospital of Lausanne, Lausanne, Switzerland.
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Carrascosa C, Obula RG, Missiaglia E, Lehr HA, Delorenzi M, Frattini M, Rüegg C, Mariotti A. MFG-E8/lactadherin regulates cyclins D1/D3 expression and enhances the tumorigenic potential of mammary epithelial cells. Oncogene 2011; 31:1521-32. [PMID: 21841820 DOI: 10.1038/onc.2011.356] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Milk fat globule-EGF factor 8 (MFG-E8) is a glycoprotein highly expressed in breast cancer that contributes to tumor progression through largely undefined mechanisms. By analyzing publicly available gene expression profiles of breast carcinomas, we found that MFG-E8 is highly expressed in primary and metastatic breast carcinomas, associated with absent estrogen receptor expression. Immunohistochemistry analysis of breast cancer biopsies revealed that MFG-E8 is expressed on the cell membrane as well as in the cytoplasm and nucleus. We also show that increased expression of MFG-E8 in mammary carcinoma cells increases their tumorigenicity in immunodeficient mice, and conversely, its downregulation reduces their in vivo growth. Moreover, expression of MFG-E8 in immortalized mammary epithelial cells promotes their growth and branching in three-dimensional collagen matrices and induces the expression of cyclins D1/D3 and N-cadherin. A mutant protein unable to bind integrins can in part exert these effects, indicating that MFG-E8 function is only partially dependent on integrin activation. We conclude that MFG-E8-dependent signaling stimulates cell proliferation and the acquisition of mesenchymal properties and contributes to mammary carcinoma development.
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Affiliation(s)
- C Carrascosa
- Division of Experimental Oncology, Centre Pluridisciplinaire d'Oncologie, Lausanne Cancer Center, University of Lausanne, Epalinges, Switzerland
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Colzani M, Waridel P, Laurent J, Faes E, Rüegg C, Quadroni M. Metabolic Labeling and Protein Linearization Technology Allow the Study of Proteins Secreted by Cultured Cells in Serum-Containing Media. J Proteome Res 2009; 8:4779-88. [DOI: 10.1021/pr900476b] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- M. Colzani
- Protein Analysis Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland, Division of Experimental Oncology, Multidisciplinary Oncology Center (CePO), Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland, and National Center of Competence in Research (NCCR) Molecular Oncology, ISREC, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - P. Waridel
- Protein Analysis Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland, Division of Experimental Oncology, Multidisciplinary Oncology Center (CePO), Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland, and National Center of Competence in Research (NCCR) Molecular Oncology, ISREC, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - J. Laurent
- Protein Analysis Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland, Division of Experimental Oncology, Multidisciplinary Oncology Center (CePO), Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland, and National Center of Competence in Research (NCCR) Molecular Oncology, ISREC, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - E. Faes
- Protein Analysis Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland, Division of Experimental Oncology, Multidisciplinary Oncology Center (CePO), Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland, and National Center of Competence in Research (NCCR) Molecular Oncology, ISREC, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - C. Rüegg
- Protein Analysis Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland, Division of Experimental Oncology, Multidisciplinary Oncology Center (CePO), Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland, and National Center of Competence in Research (NCCR) Molecular Oncology, ISREC, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - M. Quadroni
- Protein Analysis Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland, Division of Experimental Oncology, Multidisciplinary Oncology Center (CePO), Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Lausanne, Switzerland, and National Center of Competence in Research (NCCR) Molecular Oncology, ISREC, School of Life Sciences, EPFL, Lausanne, Switzerland
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Thielemann B, Rüegg C, Rønnow HM, Läuchli AM, Caux JS, Normand B, Biner D, Krämer KW, Güdel HU, Stahn J, Habicht K, Kiefer K, Boehm M, McMorrow DF, Mesot J. Direct observation of magnon fractionalization in the quantum spin ladder. Phys Rev Lett 2009; 102:107204. [PMID: 19392156 DOI: 10.1103/physrevlett.102.107204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Indexed: 05/27/2023]
Abstract
We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)2CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in the saturated phase contrast sharply with a spinon continuum at intermediate fields characteristic of the Luttinger-liquid phase. By tuning the magnetic field, we drive the fractionalization of magnons into spinons and, in this deconfined regime, observe both commensurate and incommensurate continua.
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Affiliation(s)
- B Thielemann
- Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, CH-5232 Villigen, Switzerland
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Rüegg C, Kiefer K, Thielemann B, McMorrow DF, Zapf V, Normand B, Zvonarev MB, Bouillot P, Kollath C, Giamarchi T, Capponi S, Poilblanc D, Biner D, Krämer KW. Thermodynamics of the spin Luttinger liquid in a model ladder material. Phys Rev Lett 2008; 101:247202. [PMID: 19113659 DOI: 10.1103/physrevlett.101.247202] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 10/24/2008] [Indexed: 05/27/2023]
Abstract
The phase diagram in temperature and magnetic field of the metal-organic, two-leg, spin-ladder compound (C5H12N)2CuBr4 is studied by measurements of the specific heat and the magnetocaloric effect. We demonstrate the presence of an extended spin Luttinger-liquid phase between two field-induced quantum critical points and over a broad range of temperature. Based on an ideal spin-ladder Hamiltonian, comprehensive numerical modeling of the ladder specific heat yields excellent quantitative agreement with the experimental data across the entire phase diagram.
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Affiliation(s)
- Ch Rüegg
- London Centre for Nanotechnology, University College London, London WC1E 6BT, United Kingdom
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23
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Rüegg C, Normand B, Matsumoto M, Furrer A, McMorrow DF, Krämer KW, Güdel HU, Gvasaliya SN, Mutka H, Boehm M. Quantum magnets under pressure: controlling elementary excitations in TlCuCl3. Phys Rev Lett 2008; 100:205701. [PMID: 18518554 DOI: 10.1103/physrevlett.100.205701] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Indexed: 05/26/2023]
Abstract
We follow the evolution of the elementary excitations of the quantum antiferromagnet TlCuCl3 through the pressure-induced quantum critical point, which separates a dimer-based quantum disordered phase from a phase of long-ranged magnetic order. We demonstrate by neutron spectroscopy the continuous emergence in the weakly ordered state of a low-lying but massive excitation corresponding to longitudinal fluctuations of the magnetic moment. This mode is not present in a classical description of ordered magnets, but is a direct consequence of the quantum critical point.
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Affiliation(s)
- Ch Rüegg
- London Centre for Nanotechnology, University College London, London WC1E 6BT, United Kingdom
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24
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Lorenz T, Heyer O, Garst M, Anfuso F, Rosch A, Rüegg C, Krämer K. Diverging thermal expansion of the spin-ladder system (C5H12N)2CuBr4. Phys Rev Lett 2008; 100:067208. [PMID: 18352512 DOI: 10.1103/physrevlett.100.067208] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Indexed: 05/26/2023]
Abstract
We present high-resolution measurements of the c(*)-axis thermal expansion and magnetostriction of piperidinium copper bromide (C5H12N)2CuBr4. The experimental data at low temperatures are well accounted for by a two-leg spin-ladder Hamiltonian. The thermal expansion shows a complex behavior with various sign changes and approaches a 1/square root T divergence at the critical fields. All low-temperature features are semiquantitatively explained within a free-fermion model; full quantitative agreement is obtained with quantum Monte Carlo simulations.
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Affiliation(s)
- T Lorenz
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany.
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25
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Bieler G, Hasmim M, Monnier Y, Imaizumi N, Ameyar M, Bamat J, Ponsonnet L, Chouaib S, Grell M, Goodman SL, Lejeune F, Rüegg C. Distinctive role of integrin-mediated adhesion in TNF-induced PKB/Akt and NF-κB activation and endothelial cell survival. Oncogene 2007; 26:5722-32. [PMID: 17369858 DOI: 10.1038/sj.onc.1210354] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Tumor necrosis factor (TNF) is a pro-inflammatory cytokine exerting pleiotropic effects on endothelial cells. Depending on the vascular context it can induce endothelial cell activation and survival or death. The microenvironmental cues determining whether endothelial cells will survive or die, however, have remained elusive. Here we report that integrin ligation acts permissive for TNF-induced protein kinase B (PKB/Akt) but not nuclear factor (NF)-kappaB activation. Concomitant activation of PKB/Akt and NF-kappaB is essential for the survival of endothelial cells exposed to TNF. Active PKB/Akt strengthens integrin-dependent endothelial cell adhesion, whereas disruption of actin stress fibers abolishes the protective effect of PKB/Akt. Integrin-mediated adhesion also represses TNF-induced JNK activation, but JNK activity is not required for cell death. The alphaVbeta3/alphaVbeta5 integrin inhibitor EMD121974 sensitizes endothelial cells to TNF-dependent cytotoxicity and active PKB/Akt attenuates this effect. Interferon gamma synergistically enhanced TNF-induced endothelial cell death in all conditions tested. Taken together, these observations reveal a novel permissive role for integrins in TNF-induced PKB/Akt activation and prevention of TNF-induced death distinct of NF-kappaB, and implicate the actin cytoskeleton in PKB/Akt-mediated cell survival. The sensitizing effect of EMD121974 on TNF cytotoxicity may open new perspectives to the therapeutic use of TNF as anticancer agent.
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Affiliation(s)
- G Bieler
- Division of Experimental Oncology, Lausanne Cancer Centre, Epalinges, Switzerland
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26
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Rüegg C, McMorrow DF, Normand B, Rønnow HM, Sebastian SE, Fisher IR, Batista CD, Gvasaliya SN, Niedermayer C, Stahn J. Multiple magnon modes and consequences for the Bose-Einstein condensed phase in BaCuSi2O6. Phys Rev Lett 2007; 98:017202. [PMID: 17358501 DOI: 10.1103/physrevlett.98.017202] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Indexed: 05/14/2023]
Abstract
The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering experiments on single crystals with an energy resolution considerably higher than in an earlier study. We observe multiple magnon modes, indicating clearly the presence of magnetically inequivalent dimer sites. The more complex spin Hamiltonian revealed in our study leads to a distinct form of magnon Bose-Einstein condensate phase with a spatially modulated condensate amplitude.
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Affiliation(s)
- Ch Rüegg
- London Centre for Nanotechnology, Department of Physics and Astronomy, University College London, London, UK
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27
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Hasmim M, Bieler G, Rüegg C. Zoledronate inhibits endothelial cell adhesion, migration and survival through the suppression of multiple, prenylation-dependent signaling pathways. J Thromb Haemost 2007; 5:166-73. [PMID: 17059425 DOI: 10.1111/j.1538-7836.2006.02259.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND Recent evidence indicates that zoledronate, a nitrogen-containing bisphosphonate used to treat conditions of increased bone resorption, may have anti-angiogenic activity. The endothelial cells signaling events modulated by zoledronate remain largely elusive. OBJECTIVES The aim of this work was to identify signaling events suppressed by zoledronate in endothelial cells and responsible for some of its biological effects. METHODS Human umbilical vein endothelial cells (HUVEC) were exposed to zoledronate, isoprenoid analogs (i.e. farnesol and geranylgeraniol) and various inhibitors of signaling, and the effect on adhesion, survival, migration, actin cytoskeleton and signaling events characterized. RESULTS Zoledronate reduced Ras prenylation, Ras and RhoA translocation to the membrane, and sustained ERK1/2 phosphorylation and tumor necrosis factor (TNF) induced JNK phosphorylation. Isoprenoid analogs attenuated zoledronate effects on HUVEC adhesion, actin stress fibers and focal adhesions, migration and survival. Isoprenoid analogs also restored Ras prenylation, RhoA translocation to the membrane, sustained FAK and ERK1/2 phosphorylation and prevented suppression of protein kinase B (PKB) and JNK phosphorylation in HUVEC exposed to TNF in the presence of zoledronate. Pharmacological inhibition of Rock, a RhoA target mediating actin fiber formation, phosphatidylinositol 3-kinase, an activator of PKB, MEK1/2, an activator of ERK1/2, and JNK, recapitulated individual zoledronate effects, consistent with the involvement of these molecules and pathways and their inhibition in the zoledronate effects. CONCLUSIONS This work has demonstrated that zoledronate inhibits HUVEC adhesion, survival, migration and actin stress fiber formation by interfering with protein prenylation and has identified ERK1/2, JNK, Rock, FAK and PKB as kinases affected by zoledronate in a prenylation-dependent manner.
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Affiliation(s)
- M Hasmim
- Division of Experimental Oncology, Centre Pluridisciplinaire d'Oncologie, Lausanne Cancer Center, Epalinges, Switzerland
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28
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Lejeune FJ, Rüegg C. Recombinant human tumor necrosis factor: an efficient agent for cancer treatment. Bull Cancer 2006; 93:E90-100. [PMID: 16935777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Recombinant human TNF (rhTNF) has a selective effect on endothelial cells in tumour angiogenic vessels. Its clinical use has been limited because of its property to induce vascular collapsus. TNF administration through isolated limb perfusion (ILP) for regionally advanced melanomas and soft tissue sarcomas of the limbs was shown to be safe and efficient. When combined to the alkylating agent melphalan, a single ILP produces a very high objective response rate. ILP with TNF and melphalan provided the proof of concept that a vasculotoxic strategy combined to chemotherapy may produce a strong anti-tumour effect. The registered indication of TNF-based ILP is a regional therapy for regionally spread tumours. In soft tissue sarcomas, it is a limb sparing neoadjuvant treatment and, in melanoma in-transit metastases, a curative treatment. Despite its demonstrated regional efficiency TNF-based ILP is unlikely to have any impact on survival. High TNF dosages induce endothelial cells apoptosis, leading to vascular destruction. However, lower TNF dosage produces a very strong effect that is to increase the drug penetration into the tumour, presumably by decreasing the intratumoural hypertension resulting in better tumour uptake. TNF-ILP allowed the identification of the role of alphaVbeta3 integrin deactivation as an important mechanism of antiangiogenesis. Several recent studies have shown that TNF targeting is possible, paving the way to a new opportunity to administer TNF systemically for improving cancer drug penetration. TNF was the first agent registered for the treatment of cancer that improves drug penetration in tumours and selectively destroys angiogenic vessels.
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Affiliation(s)
- F J Lejeune
- Centre hospitalier universitaire Vaudois, Lausanne, Suisse.
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29
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Monnier Y, Andrejevic S, Desbaillets I, Moeckli R, Mirimanoff R, Rüegg C. 112 Stroma irradiation promotes tumor invasion and metastasis through suppression of angiogenesis and selection of highly invasive tumor cells. Radiother Oncol 2006. [DOI: 10.1016/s0167-8140(06)80591-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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30
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Rüegg C, Normand B, Matsumoto M, Niedermayer C, Furrer A, Krämer KW, Güdel HU, Bourges P, Sidis Y, Mutka H. Quantum statistics of interacting dimer spin systems. Phys Rev Lett 2005; 95:267201. [PMID: 16486391 DOI: 10.1103/physrevlett.95.267201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Indexed: 05/06/2023]
Abstract
The compound TlCuCl(3) represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron scattering experiments on single crystals. By comparison with a number of theoretical approaches we demonstrate that the description of Troyer, Tsunetsugu, and Würtz [Phys. Rev. B 50, 13 515 (1994)10.1103/Phys. Rev. B 50, 13515] provides an appropriate quantum statistical model for dimer spin systems at finite temperatures, where many-body correlations become particularly important.
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Affiliation(s)
- Ch Rüegg
- London Centre for Nanotechnology, Department of Physics and Astronomy, University College London, UK.
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31
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Rüegg C, Furrer A, Sheptyakov D, Strässle T, Krämer KW, Güdel HU, Mélési L. Pressure-induced quantum phase transition in the spin-liquid TlCuCl3. Phys Rev Lett 2004; 93:257201. [PMID: 15697931 DOI: 10.1103/physrevlett.93.257201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Indexed: 05/24/2023]
Abstract
The condensation of magnetic quasiparticles into the nonmagnetic ground state has been used to explain novel magnetic ordering phenomena observed in quantum spin systems. We present neutron scattering results across the pressure-induced quantum phase transition and for the novel ordered phase of the magnetic insulator TlCuCl3, which are consistent with the theoretically predicted two degenerate gapless Goldstone modes, similar to the low-energy spin excitations in the field-induced case. These novel experimental findings complete the field-induced Bose-Einstein condensate picture and support the recently proposed field-pressure phase diagram common for quantum spin systems with an energy gap of singlet-triplet nature.
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Affiliation(s)
- Ch Rüegg
- Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
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32
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Rüegg C, Oettli M, Schefer J, Zaharko O, Furrer A, Tanaka H, Krämer KW, Güdel HU, Vorderwisch P, Habicht K, Polinski T, Meissner M. Neutron scattering study of the field-dependent ground state and the spin dynamics in spin-one-half NH4CuCl3. Phys Rev Lett 2004; 93:037207. [PMID: 15323865 DOI: 10.1103/physrevlett.93.037207] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2004] [Indexed: 05/24/2023]
Abstract
Elastic and inelastic neutron scattering experiments have been performed on the dimer spin system NH4CuCl3, which shows plateaus in the magnetization curve at m=1/4 and m=3/4 of the saturation value. Two structural phase transitions at T1 approximately 156 K and at T(2)=70 K lead to a doubling of the crystallographic unit cell along the b direction and as a consequence a segregation into different dimer subsystems. Long-range magnetic ordering is reported below T(N)=1.3 K. The magnetic field dependence of the excitation spectrum identifies successive quantum phase transitions of the dimer subsystems as the driving mechanism for the unconventional magnetization process in agreement with a recent theoretical model.
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Affiliation(s)
- Ch Rüegg
- Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
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33
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Abstract
New blood vessel formation, a process referred to as angiogenesis, is essential for embryonic development and for many physiological and pathological processes during postnatal life, including cancer progression. Endothelial cell adhesion molecules of the integrin family have emerged as critical mediators and regulators of angiogenesis and vascular homeostasis. Integrins provide the physical interaction with the extracellular matrix necessary for cell adhesion, migration and positioning, and induction of signaling events essential for cell survival, proliferation and differentiation. Antagonists of integrin alpha V beta 3 suppress angiogenesis in many experimental models and are currently tested in clinical trials for their therapeutic efficacy against angiogenesis-dependent diseases, including cancer. Furthermore, interfering with signaling pathways downstream of integrins results in suppression of angiogenesis and may have relevant therapeutic implications. In this article we review the role of integrins in endothelial cell function and angiogenesis. In the light of recent advances in the field, we will discuss their relevance as a therapeutic target to suppress tumor angiogenesis.
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Affiliation(s)
- C Rüegg
- Laboratory of the Centre Pluridisciplinaire d'Oncologie, University of Lausanne, Medical School, and Swiss Institute for Experimental Cancer Research (ISREC), 155 Chemin des Boveresses, 1066 Epalinges, Switzerland.
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34
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Rüegg C, Cavadini N, Furrer A, Güdel HU, Krämer K, Mutka H, Wildes A, Habicht K, Vorderwisch P. Bose-Einstein condensation of the triplet states in the magnetic insulator TlCuCl3. Nature 2003; 423:62-5. [PMID: 12721623 DOI: 10.1038/nature01617] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2002] [Accepted: 03/17/2003] [Indexed: 11/09/2022]
Abstract
Bose-Einstein condensation denotes the formation of a collective quantum ground state of identical particles with integer spin or intrinsic angular momentum. In magnetic insulators, the magnetic properties are due to the unpaired shell electrons that have half-integer spin. However, in some such compounds (KCuCl3 and TlCuCl3), two Cu2+ ions are antiferromagnetically coupled to form a dimer in a crystalline network: the dimer ground state is a spin singlet (total spin zero), separated by an energy gap from the excited triplet state (total spin one). In these dimer compounds, Bose-Einstein condensation becomes theoretically possible. At a critical external magnetic field, the energy of one of the Zeeman split triplet components (a type of boson) intersects the ground-state singlet, resulting in long-range magnetic order; this transition represents a quantum critical point at which Bose-Einstein condensation occurs. Here we report an experimental investigation of the excitation spectrum in such a field-induced magnetically ordered state, using inelastic neutron scattering measurements of TlCuCl3 single crystals. We verify unambiguously the theoretically predicted gapless Goldstone mode characteristic of the Bose-Einstein condensation of the triplet states.
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Affiliation(s)
- Ch Rüegg
- Laboratory for Neutron Scattering, ETH Zürich & Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
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35
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Rüegg C, Dormond O, Foletti A. Suppression of tumor angiogenesis through the inhibition of integrin function and signaling in endothelial cells: which side to target? Endothelium 2003; 9:151-60. [PMID: 12380640 DOI: 10.1080/10623320213635] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Tumor angiogenesis is an essential step in tumor progression and metastasis formation. Suppression of tumor angiogenesis results in the inhibition of tumor growth. Recent evidence indicates that vascular integrins, in particular alpha V beta 3, are important regulators of angiogenesis, including tumor angiogenesis. Integrin alpha V beta 3 antagonists, such as blocking antibodies or peptides, suppress tumor angiogenesis and tumor progression in many preclinical tumor models. The potential therapeutic efficacy of extracellular integrin antagonists in human cancer is currently being tested in clinical trials. Selective disruption of the tumor vasculature by high doses of tumor necrosis factor (TNF) and interferon gamma (IFN-gamma), and the antiangiogenic activity of nonsteroidal anti-inflammatory drugs are associated with the suppression of integrin alpha V beta 3 function and signaling in endothelial cells. Furthermore, expression of isolated integrin cytoplasmic domains disrupts integrin-dependent adhesion, resulting in endothelial cell detachment and apoptosis. These results confirm the critical role of vascular integrins in promoting endothelial cell survival and angiogenesis and suggest that intracellular targeting of integrin function and signaling may be an alternative strategy to extracellular integrin antagonists for the therapeutic inhibition of tumor angiogenesis.
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Affiliation(s)
- C Rüegg
- Centre Pluridisciplinaire d'Oncologie, University of Lausanne Medical School, Switzerland.
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36
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37
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Puente Navazo MD, Valmori D, Rüegg C. The alternatively spliced domain TnFnIII A1A2 of the extracellular matrix protein tenascin-C suppresses activation-induced T lymphocyte proliferation and cytokine production. J Immunol 2001; 167:6431-40. [PMID: 11714809 DOI: 10.4049/jimmunol.167.11.6431] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Several lines of evidences have suggested that T cell activation could be impaired in the tumor environment, a condition referred to as tumor-induced immunosuppression. We have previously shown that tenascin-C, an extracellular matrix protein highly expressed in the tumor stroma, inhibits T lymphocyte activation in vitro, raising the possibility that this molecule might contribute to tumor-induced immunosuppression in vivo. However, the region of the protein mediating this effect has remained elusive. Here we report the identification of the minimal region of tenascin-C that can inhibit T cell activation. Recombinant fragments corresponding to defined regions of the molecule were tested for their ability to inhibit in vitro activation of human peripheral blood T cells induced by anti-CD3 mAbs in combination with fibronectin or IL-2. A recombinant protein encompassing the alternatively spliced fibronectin type III domains of tenascin-C (TnFnIII A-D) vigorously inhibited both early and late lymphocyte activation events including activation-induced TCR/CD8 down-modulation, cytokine production, and DNA synthesis. In agreement with this, full length recombinant tenascin-C containing the alternatively spliced region suppressed T cell activation, whereas tenascin-C lacking this region did not. Using a series of smaller fragments and deletion mutants issued from this region, we have identified the TnFnIII A1A2 domain as the minimal region suppressing T cell activation. Single TnFnIII A1 or A2 domains were no longer inhibitory, while maximal inhibition required the presence of the TnFnIII A3 domain. Altogether, these data demonstrate that the TnFnIII A1A2 domain mediate the ability of tenascin-C to inhibit in vitro T cell activation and provide insights into the immunosuppressive activity of tenascin-C in vivo.
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MESH Headings
- Alternative Splicing/immunology
- Cytokines/antagonists & inhibitors
- Cytokines/biosynthesis
- Cytotoxicity, Immunologic/genetics
- Cytotoxicity, Immunologic/immunology
- Down-Regulation/genetics
- Down-Regulation/immunology
- Fibronectins/genetics
- Fibronectins/physiology
- Humans
- Immunosuppressive Agents/pharmacology
- Lymphocyte Activation/genetics
- Lymphocyte Activation/immunology
- Peptide Fragments/genetics
- Peptide Fragments/physiology
- Protein Isoforms/genetics
- Protein Isoforms/physiology
- Protein Structure, Tertiary/genetics
- Receptor-CD3 Complex, Antigen, T-Cell/antagonists & inhibitors
- Receptor-CD3 Complex, Antigen, T-Cell/biosynthesis
- Recombinant Proteins/genetics
- Recombinant Proteins/pharmacology
- Repetitive Sequences, Amino Acid/genetics
- Repetitive Sequences, Amino Acid/immunology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- Tenascin/genetics
- Tenascin/physiology
- Tumor Cells, Cultured
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Affiliation(s)
- M D Puente Navazo
- Centre Pluridisciplinaire d'Oncologie, University of Lausanne Medical School, Lausanne, Switzerland
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38
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Abstract
There is solid epidemiological evidence demonstrating that the regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) reduces the risk of developing colorectal cancer, and to a lesser extent gastric and esophageal cancers[1]. Importantly, NSAIDs suppress colon polyp formation and progression in patients diagnosed with familial adenomatous polyposis coli (APC)[2]. In many animal studies, NSAIDs have been shown to prevent tumor formation and slow tumor progression, thus confirming and extending the clinical observations[3,4,5]. Recent findings have demonstrated that NSAIDs inhibit angiogenesis, suggesting that the tumor suppressive activity of these drugs may be due, at least in part, to their ability to inhibit tumor angiogenesis[6]. The study of the mechanism by which NSAIDs suppress tumor angiogenesis, is matter of intense research.
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Affiliation(s)
- C Rüegg
- Laboratory of the Centre Pluridisciplinaire d'Oncologie, University of Lausanne Medical School, Swiss Institute for Experimental Cancer Research, Epalinges, Switzerland.
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39
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Dermond O, Rüegg C. Inhibition of tumor angiogenesis by non-steroidal anti-inflammatory drugs: emerging mechanisms and therapeutic perspectives. Drug Resist Updat 2001; 4:314-21. [PMID: 11991685 DOI: 10.1054/drup.2001.0219] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Chronic intake of non steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced risk of developing gastrointestinal tumors, in particular colon cancer. Increasing evidence indicates that NSAID exert tumor-suppressive activity on pre-malignant lesions (polyps) in humans and on established experimental tumors in mice. Some of the tumor-suppressive effects of NSAIDs depend on the inhibition of cyclooxygenase-2 (COX-2), a key enzyme in the synthesis of prostaglandins and thromboxane, which is highly expressed in inflammation and cancer. Recent findings indicate that NSAIDs exert their anti-tumor effects by suppressing tumor angiogenesis. The availability of COX-2-specific NSAIDs opens the possibility of using this drug class as anti-angiogenic agents in combination with chemotheapy or radiotherapy for the treatment of human cancer. Here we will briefly review recent advances in the understanding of the mechanism by which NSAIDs suppress tumor angiogenesis and discuss their potential clinical application as anti-cancer agents.
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Affiliation(s)
- O Dermond
- Centre Pluridisciplinaire d'Oncologie (CePO), University of Lausanne Medical School, Lausanne, CH-1011, Switzerland
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40
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Dormond O, Foletti A, Paroz C, Rüegg C. NSAIDs inhibit alpha V beta 3 integrin-mediated and Cdc42/Rac-dependent endothelial-cell spreading, migration and angiogenesis. Nat Med 2001; 7:1041-7. [PMID: 11533708 DOI: 10.1038/nm0901-1041] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Cyclooxygenase-2 (COX-2), a key enzyme in arachidonic acid metabolism, is overexpressed in many cancers. Inhibition of COX-2 by nonsteroidal anti-inflammatory drugs (NSAIDs) reduces the risk of cancer development in humans and suppresses tumor growth in animal models. The anti-cancer effect of NSAIDs seems to involve suppression of tumor angiogenesis, but the underlying mechanism is not completely understood. Integrin alpha V beta 3 is an adhesion receptor critically involved in mediating tumor angiogenesis. Here we show that inhibition of endothelial-cell COX-2 by NSAIDs suppresses alpha V beta 3-dependent activation of the small GTPases Cdc42 and Rac, resulting in inhibition of endothelial-cell spreading and migration in vitro and suppression of fibroblast growth factor-2-induced angiogenesis in vivo. These results establish a novel functional link between COX-2, integrin alpha V beta 3 and Cdc42-/Rac-dependent endothelial-cell migration. Moreover, they provide a rationale to the understanding of the anti-angiogenic activity of NSAIDs.
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Affiliation(s)
- O Dormond
- Centre Pluridisciplinaire d'Oncologie, University of Lausanne Medical School, Lausanne, Switzerland
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Leyton L, Schneider P, Labra CV, Rüegg C, Hetz CA, Quest AF, Bron C. Thy-1 binds to integrin beta(3) on astrocytes and triggers formation of focal contact sites. Curr Biol 2001; 11:1028-38. [PMID: 11470407 DOI: 10.1016/s0960-9822(01)00262-7] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
BACKGROUND Thy-1 is an abundant neuronal glycoprotein in mammals. Despite such prevalence, Thy-1 function remains largely obscure in the absence of a defined ligand. Astrocytes, ubiquitous cells of the brain, express a putative Thy-1 ligand that prevents neurite outgrowth. In this paper, a ligand molecule for Thy-1 was identified, and the consequences of Thy-1 binding for astrocyte function were investigated. RESULTS Thy-1 has been implicated in cell adhesion and, indeed, all known Thy-1 sequences were found to contain an integrin binding, RGD-like sequence. Thy-1 interaction with beta3 integrin on astrocytes was demonstrated in an adhesion assay using a thymoma line (EL-4) expressing high levels of Thy-1. EL-4 cells bound to astrocytes five times more readily than EL-4(-f), control cells lacking Thy-1. Binding was blocked by either anti-Thy-1 or anti-beta3 antibodies, by RGD-related peptides, or by soluble Thy-1-Fc chimeras. However, neither RGE/RLE peptides nor Thy-1(RLE)-Fc fusion protein inhibited the interaction. Immobilized Thy-1-Fc, but not Thy-1(RLE)-Fc fusion protein supported the attachment and spreading of astrocytes in a Mn(2+)-dependent manner. Binding to Thy-1-Fc was inhibited by RGD peptides. Moreover, vitronectin, fibrinogen, denatured collagen (dcollagen), and a kistrin-derived peptide, but not fibronectin, also mediated Mn(2+)-dependent adhesion, suggesting the involvement of beta3 integrin. The addition of Thy-1 to matrix-bound astrocytes induced recruitment of paxillin, vinculin, and focal adhesion kinase (FAK) to focal contacts and increased tyrosine phosphorylation of proteins such as p130(Cas) and FAK. Furthermore, astrocyte binding to immobilized Thy-1-Fc alone was sufficient to promote focal adhesion formation and phosphorylation on tyrosine. CONCLUSIONS Thy-1 binds to beta3 integrin and triggers tyrosine phosphorylation of focal adhesion proteins in astrocytes, thereby promoting focal adhesion formation, cell attachment, and spreading.
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Affiliation(s)
- L Leyton
- ICBM-Faculty of Medicine, University of Chile, Santiago, Chile.
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Oguey D, George PW, Rüegg C. Disruption of integrin-dependent adhesion and survival of endothelial cells by recombinant adenovirus expressing isolated beta integrin cytoplasmic domains. Gene Ther 2000; 7:1292-303. [PMID: 10918500 DOI: 10.1038/sj.gt.3301236] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We explored the possibility of using a genetic approach to inhibit integrin-mediated endothelial cell adhesion and survival. We constructed recombinant adenoviruses (Ads) expressing chimeric proteins consisting of the cytoplasmic and transmembrane domains of integrin beta1 (CH1), beta3 (CH3) or the beta1 transmembrane domain alone (CH2) connected to the extracellular domain of L3T4 placed under the control of the CMV promoter (AdCMV) or the endothelial cell specific Tie-1 promoter (AdTie). All constructs were expressed in a dose- and time-dependent manner with over 90% of cells expressing the constructs within 24 h (AdCMVs) or 72 h (AdTies) after infection. Confluent monolayers of HUVEC infected with AdCMVCH1 or AdCMVCH3 detached from the substrate in a time- and dose-dependent manner with over 95% of the cells being detached 2 days (AdCMVs) or 3 to 4 days (AdTies) after infection. Cell detachment was preceded by the disruption of focal adhesions and reorganization of the actin cytoskeleton and was associated with a reduced ligand-binding activity of beta1, while cell surface density of beta1 integrins remained unchanged. Detached cells failed to re-adhere to different matrix proteins, without, however, any specificity toward beta1 or beta3 integrin-mediated adhesion. Upon detachment, HUVEC rapidly died by apoptosis. These results demonstrate that dominant negative inhibition of integrin function is an effective approach to disrupt endothelial cell adhesion and survival in vitro.
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Affiliation(s)
- D Oguey
- Centre Pluridisciplinaire d'Oncologie, School of Medicine, University of Lausanne, Switzerland
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Olivier P, Bieler G, Müller KM, Hauzenberger D, Rüegg C. Urokinase-type plasminogen activator inhibits alpha 4 beta 1 integrin-mediated T lymphocyte adhesion to fibronectin independently of its catalytic activity. Eur J Immunol 1999; 29:3196-209. [PMID: 10540331 DOI: 10.1002/(sici)1521-4141(199910)29:10<3196::aid-immu3196>3.0.co;2-n] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The urokinase-type plasminogen activator (u-PA)/plasmin system plays an important role in promoting cell migration and invasion, an effect which is largely ascribed to the proteolytic activity of these enzymes. We investigated whether u-PA modulates integrin-dependent T lymphocyte migration and adhesion on fibronectin independently of its plasminogen activator function. Here we report that u-PA reduced the spontaneous and phorbol 12-myristate 13-acetate-induced migration of peripheral blood T lymphocytes on fibronectin by 20-50%, decreased the T lymphocyte and alpha4beta1(+)/alpha5beta1(+) K562 cell adhesion on fibronectin by 30-40%, and completely suppressed integrin alpha4beta1-dependent T lymphocyte and alpha4beta1(+)/alpha5beta1(+) K562 cell adhesion to the LDV-containing 40-kDa fibronectin fragment. The u-PA receptor was not essential for this effect. In contrast, adhesion of alpha4beta1(-)/alpha5beta1(+) K562 cells to an RGD-containing fibronectin fragment was unaffected. A recombinant protein comprising the N-terminal fragment of u-PA, but lacking its proteolytic domain, had the same inhibitory effect. Decreased adhesion was neither associated with a diminished cell surface expression of alpha4beta1 nor with a suppression of alpha4beta1 ligand-binding function. Our results demonstrate that u-PA inhibits alpha4beta1- but not alpha5beta1-mediated lymphocyte/leukocyte adhesion to fibronectin independently of its proteolytic activity. This finding provides additional evidence that matrix proteinases may participate in cell adhesion and migration control independently of their matrix-degrading activity.
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Affiliation(s)
- P Olivier
- Centre Pluridisciplinaire d'Oncologie, School of Medicine, University of Lausanne, Lausanne, Switzerland
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Hauzenberger D, Olivier P, Gundersen D, Rüegg C. Tenascin-C inhibits beta1 integrin-dependent T lymphocyte adhesion to fibronectin through the binding of its fnIII 1-5 repeats to fibronectin. Eur J Immunol 1999; 29:1435-47. [PMID: 10359097 DOI: 10.1002/(sici)1521-4141(199905)29:05<1435::aid-immu1435>3.0.co;2-n] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The extracellular matrix consists of different proteins interacting to form a meshwork-like structure. T lymphocyte adhesion to individual matrix proteins is mainly regulated at the adhesion receptor level, but it is conceivable that the composition of the matrix itself may affect T lymphocyte adhesion to individual proteins. We have addressed the latter point by studying the effect of the matrix protein tenascin-C (TN-C) on T lymphocyte adhesion to fibronectin. Here we report that TN-C inhibits adhesion of T lymphocytes and MOLT-4 lymphoma cells to fibronectin. We demonstrate that a TN-C fragment consisting of fibronectin type III repeats 1-5 (TNfnIII 1-5) but not TNfnIII A-D and TNfnIII 6-8 inhibited alpha5beta1 and alpha4beta1 integrin-mediated T lymphocyte and MOLT-4 adhesion to fibronectin. At concentrations that did not inhibit adhesion, TNfnIII 1-5 still prevented MOLT-4 cells from spreading on fibronectin. Preincubation and co-immobilization of TNfnIII 1-5 with fibronectin was more effective in inhibiting MOLT-4 adhesion to fibronectin than soluble TNfnIII 1-5 present during the adhesion test. Using an enzyme-linked immunosorbent assay we could demonstrate binding of TNfnIII 1-5 to fibronectin and fibronectin fragments. Taken together, these data demonstrate that the TNfnIII 1-5 domain is implicated in the inhibition of T lymphocyte adhesion to fibronectin caused by TN-C, and indicate that this effect involves the binding of TN-C repeats TNfnIII 1-5 to fibronectin.
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Affiliation(s)
- D Hauzenberger
- Laboratory of the Centre Pluridisciplinaire d'Oncologie at the Swiss Institute for Experimental Cancer Research, Epalinges
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Abstract
High-dose TNF-alpha plus chemotherapy, with or without IFN-gamma, can be safely administered regionally through isolated limb perfusion. This procedure produced between 70% and 80% complete remission in cases of in transit melanoma metastases and between 25% and 36% complete remission in cases of inextirpable soft-tissue sarcomas. Dual targeting is involved; TNF-alpha and IFN-gamma induce apoptosis of angiogenic endothelium, while melphalan induces apoptosis of tumour cells.
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Affiliation(s)
- F J Lejeune
- Centre Pluridisciplinaire d'Oncologie, Centre Hospitalier UniversitaireVaudois (CHUV), Rue du Bugnon 46, CH-1011, Lausanne, Switzerland.
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Yilmaz A, Bieler G, Spertini O, Lejeune FJ, Rüegg C. Pulse treatment of human vascular endothelial cells with high doses of tumor necrosis factor and interferon-gamma results in simultaneous synergistic and reversible effects on proliferation and morphology. Int J Cancer 1998; 77:592-9. [PMID: 9679764 DOI: 10.1002/(sici)1097-0215(19980812)77:4<592::aid-ijc20>3.0.co;2-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Regional administration of high doses of tumor necrosis factor (TNF), interferon gamma (IFNgamma) and melphalan to patients with advanced cancers of the limbs, results in rapid and specific tumor necrosis, while the normal adjacent tissues remain unaffected. The tumor vasculature is selectively destroyed by this treatment, and neovascular endothelial cells appear to be an early and specific target of TNF and IFNgamma. To further understand some of the cellular events underlying these in vivo effects, we have investigated the response of human macro- and microvascular endothelial cells in vitro, after exposure to high doses of TNF and IFNgamma (up to 40 x 10(3) U/ml each). TNF and IFNgamma synergistically inhibited endothelial-cell proliferation by up to 80% after 72 hr of treatment. Achievement of synergy required the simultaneous presence of both cytokines. A cytokine pulse as short as 30 min was sufficient to induce maximal growth inhibition measured after 48 hr. Both cytokines also induced progressive and dose-dependent elongation of the endothelial-cell morphology. The effects on endothelial-cell proliferation and morphology were reversible upon removal of the cytokines. Moreover, replating of treated cells onto a fresh substrate immediately resulted in re-acquisition of their normal shape. In contrast to the effect on cell proliferation, there was little or no effect on the rate of endothelial-cell apoptosis. The presented data extend reports on the effects of TNF and IFNgamma on human endothelial cells in vitro, and suggest that the in vivo disruption of the tumor vasculature caused by high doses of TNF and IFNgamma is not due to a direct cytotoxic effect on endothelial cells but occurs through an indirect mechanism.
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Affiliation(s)
- A Yilmaz
- Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, School of Medicine, University of Lausanne, Switzerland
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Marazzi S, Blum S, Hartmann R, Gundersen D, Schreyer M, Argraves S, von Fliedner V, Pytela R, Rüegg C. Characterization of human fibroleukin, a fibrinogen-like protein secreted by T lymphocytes. J Immunol 1998; 161:138-47. [PMID: 9647217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We have recently cloned the human homologue of the murine pT49 cDNA (hpT49h), a transcript encoding a protein homologous to the beta- and gamma-chains of fibrinogen. Here, we report the identification of the hpT49h gene product using mAbs generated against a peptide corresponding to the carboxyl-terminal end of the deduced protein and a recombinant protein fragment expressed in Escherichia coli. mAbs 23A6, 7B12, and 3F4 specifically recognized a protein of 70 kDa in reducing SDS-PAGE in the culture supernatant of 293T cells transiently transfected with the full length hpT49h cDNA and freshly isolated PBMC. Under nonreducing conditions, the material migrated with a molecular mass of 250 to 300 kDa, indicating that the 70-kDa protein forms a disulfide bonded complex. Because of its homology with fibrinogen, we have termed this protein fibroleukin. Fibroleukin is spontaneously secreted in vitro by freshly isolated CD4+ and CD8+ T lymphocytes. RT-PCR analysis revealed preferential expression of fibroleukin mRNA in memory T lymphocytes (CD3+/CD45R0+) compared with naive T lymphocytes (CD3+/CD45RA+). Fibroleukin production by PBMC was rapidly lost in culture. Production could be partially maintained in the presence of IFN-gamma, while T lymphocyte activation had no effect. To demonstrate fibroleukin production in vivo, we analyzed colon mucosa by immunohistology. Fibroleukin staining was detected in the extracellular matrix of the T lymphocyte-rich upper portion of the lamina propria mucosa. While the exact function of fibroleukin remains to be defined, these data suggest that fibroleukin may play a role in physiologic lymphocyte functions at mucosal sites.
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Affiliation(s)
- S Marazzi
- Centre Pluridisciplinaire d'Oncologie, School of Medicine, University of Lausanne, Switzerland
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Rüegg C, Yilmaz A, Bieler G, Bamat J, Chaubert P, Lejeune FJ. Evidence for the involvement of endothelial cell integrin alphaVbeta3 in the disruption of the tumor vasculature induced by TNF and IFN-gamma. Nat Med 1998; 4:408-14. [PMID: 9546785 DOI: 10.1038/nm0498-408] [Citation(s) in RCA: 349] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Administration of tumor necrosis factor (TNF) and gamma interferon (IFN-gamma) to melanoma patients causes selective disruption of the tumor vasculature but the mechanism of this disruption is unknown. Here we report that exposure of human endothelial cells to TNF and IFN-gamma results in a reduced activation of integrin alphaVbeta3, an adhesion receptor that plays a key role in tumor angiogenesis, leading to a decreased alphaVbeta3-dependent endothelial cell adhesion and survival. Detachment and apoptosis of angiogenic endothelial cells was demonstrated in vivo in melanoma metastases of patients treated with TNF and IFN-gamma. These results implicate integrin alphaVbeta3 in the anti-vascular activity of TNF and IFN-gamma and demonstrate a new mechanism by which cytokines control cell adhesion.
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Affiliation(s)
- C Rüegg
- Centre Pluridisciplinaire d'Oncologie, School of Medicine, University of Lausanne, Centre Hospitalier Universitaire Vaudois, Switzerland
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Gérain J, Liénard D, Pampallona S, Baumgartner M, Rüegg C, Buurman WA, Eggermont A, Lejeune F. Systemic release of soluble TNF receptors after high-dose TNF in isolated limb perfusion. Cytokine 1997; 9:1034-42. [PMID: 9417816 DOI: 10.1006/cyto.1997.0247] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Isolated limb perfusion (ILP) with high dose tumour necrosis factor (TNF), interferon gamma and melphalan (TIM) is an efficient treatment for patients with regionally advanced melanoma and sarcoma. In 44 patients, we determined the kinetics of soluble TNF receptors (sTNF-RI and RII) plasma concentrations, and correlated them with systemic TNF and interleukin 6 (IL-6) levels and shock. Seven patients treated conventionally by ILP without cytokine served as controls. Elevated levels of both sTNF-Rs were observed within 30 min after beginning of the TIM-ILP. A first peak of sTNF-Rs levels was observed 3 h after ILP and was followed by a rapid decrease reaching a nadir at 12-14 h post ILP. This first peak was followed by a second, long-lasting elevation of both sTNF-Rs levels persisting for 4 to 5 days after TIM-ILP. Patients treated by ILP without TNF/interferon gamma (IFN-gamma) had no detectable increase in either sTNF-Rs or in circulating TNF, demonstrating that the release of TNF-Rs was dependent upon the administration of TNF/IFN-gamma. High plasma levels of TNF and IL-6 were observed in patients that had more than 5% leakage during the TIM-ILP, but no significant correlation between TNF levels and the peak values of both sTNF-Rs was observed. The levels of TNF and IL-6 were, however, significantly related to each other. TNF systemic levels, but not sTNF-Rs concentrations, correlated significantly with the severity of the shock observed after TIM-ILP. Patients in which sTNF-RII concentration was in excess over circulating TNF, had no shock or grade I shock only, suggesting that sTNF-RII may play a protective, although limited, role in inhibiting activity of circulating TNF.
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Affiliation(s)
- J Gérain
- Centre pluridisciplinaire d'Oncologie, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
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Furrer M, Altermatt HJ, Ris HB, Althaus U, Rüegg C, Liénard D, Lejeune FJ. Lack of antitumour activity of human recombinant tumour necrosis factor-alpha, alone or in combination with melphalan in a nude mouse human melanoma xenograft system. Melanoma Res 1997; 7 Suppl 2:S43-9. [PMID: 9578416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The most promising developments in the field of isolated limb perfusion have centred around the use of the recombinant cytokine tumour necrosis factor-alpha (rTNF-alpha) in combination with melphalan. While the results of clinical trials are impressive, the exact antitumour mechanisms of rTNF-alpha and its role in combination with melphalan remain unclear. Our aim was to study the antitumour activity of human rTNF-alpha with or without the combination of melphalan in a nude mouse human melanoma xenograft system. In a first attempt to define the maximal tolerated single dose of rTNF-alpha in this setting, 15 animals were exposed to increasing doses of rTNF-alpha (60-2500 microg/kg intraperitoneally). All but one animal survived and tumour growth was not influenced by these single dose applications of rTNF-alpha even at the very high doses. Anti-tumour activity of repeated application of melphalan (three times 9 mg/kg in group 2 and three times 6 mg/kg in group 3), of rTNF-alpha alone (nine doses of 50 microg/kg in group 4), and of rTNF-alpha in combination with melphalan (nine doses of 50 microg/kg rTNF-alpha and three times 6 mg/kg melphalan in group 5) was further compared with non-treated animals (group 1). Tumour growth was significantly inhibited in all animals treated with melphalan (group 2, 3 and 5), but was not decreased in animals treated with rTNF-alpha alone (group 4). Mean final tumour volumes and mean tumour weight were not different in group 2 (789 +/- 836 mm3, 0.38 +/- 0.20 g), group 3 (1173 +/- 591 mm3, 0.55 +/- 0.29 g) and group 5 (230 +/- 632 mm3, 0.37 +/- 0.29 g), but significant lower than group 1 (3156 +/- 1512 mm3, 2.35 +/- 0.90 g) and group 4 (3228 +/- 1990 mm3, 2.00 +/- 1.16 g). There were no significant differences between high and low dose melphalan treatment and between melphalan treatment in combination with rTNF-alpha. Histological examination did not show differences between treated and non-treated animals besides slightly inhibited mitotic activities of tumour cells in melphalan-treated animals. While tumour growth of human xenotransplanted melanoma in nude mice could be inhibited by melphalan, we failed to demonstrate any antitumour effect of rTNF-alpha. The combination of melphalan and rTNF-alpha did not enhance the antiproliferative effect of melphalan alone. Human xenotransplanted tumours on nude mice might not be the ideal experimental setting for studies of potential direct antineoplastic activity of rTNF-alpha, and these results support the concept that TNF-alpha exerts its antitumour activity indirectly, possibly by impairing the tumour vasculature and by activating the immune system.
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Affiliation(s)
- M Furrer
- Department of Thoracic and Cardiovascular Surgery, University of Bern, Switzerland
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