title: In vivo imaging of integrin alpha v beta 3 expression using fluorescence-mediated tomography.
abstract: OBJECTIVE
  Optical imaging would be desirable for cancer diagnostics since it can potentially resolve relevant oncological target structures in vivo. We therefore synthesised an alpha v beta(3) targeted fluorochrome and imaged tumour xenografts with different alpha v beta(3) expression levels using both planar and tomographic optical imaging methods.
  
  
  METHODS
  An alpha v beta(3)-targeted RGD peptide was labelled with a cyanine dye (Cy 5.5). Binding of the optical tracer was tested on M21 melanoma (n=5), HT-1080 fibrosarcoma (n=6) and MCF-7 adenocarcinoma (n=5) cells and their tumour xenografts. All optical imaging studies were performed using two-dimensional planar fluorescence reflectance imaging (FRI) technology and three-dimensional fluorescence-mediated tomography (FMT).
  
  
  RESULTS
  In vitro, the peptide-dye conjugate showed a clear binding affinity to alpha v beta(3)-positive M21 and HT-1080 cells while alpha v beta(3)-negative MCF-7 cells and pre-dosing with the free RGD peptide revealed little to no fluorescence. In vivo, tumour xenografts were clearly visualised by FRI and FMT up to 24 h post injection. FMT allowed quantification of the fluorochrome distribution in deeper tissue sections showing an average fluorochrome concentration of 417.61 +/- 105.82 nM Cy 5.5 (M21), 353.68 +/- 54.02 nM Cy 5.5 (HT-1080) and 262.83 +/- 155.36 nM Cy 5.5 (MCF-7) in the target tissue 60 min after tracer administration. Competition with the free RGD peptide resulted in a reduction in the fluorochrome concentration in M21 tumour tissue (294.35 +/- 84.27 nM).
  
  
  CONCLUSIONS
  RGD-Cy 5.5 combined with novel tomographic optical imaging methods allows non-invasive imaging of tumour-associated alpha v beta(3) expression and may thus be a promising strategy for sensitive evaluation of tumour target expression.
authors.affiliation: Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.|Interdisciplinary Center for Clinical Research (IZKF Muenster, FG3), University of Münster, Münster, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: von Wallbrunn
authors.affiliation: Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.|Departments of Nuclear Medicine and Clinical Radiology, University of Münster, Münster, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Höltke
authors.affiliation: Department of Hematology and Oncology, University of Münster, Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Zühlsdorf
authors.affiliation: Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Heindel
authors.affiliation: Interdisciplinary Center for Clinical Research (IZKF Muenster, FG3), University of Münster, Münster, Germany.|Department of Nuclear Medicine, University of Münster, Münster, Germany.|Interdisciplinary Center for Clinical Research (IZKF Muenster, ZPG 4b), University of Münster, Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schäfers
authors.affiliation: Department of Clinical Radiology, University of Münster, Albert-Schweitzer-Strasse 33, 48129, Münster, Germany. bremerc@uni-muenster.de.|Interdisciplinary Center for Clinical Research (IZKF Muenster, FG3), University of Münster, Münster, Germany. bremerc@uni-muenster.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bremer
mesh_terms: D000818:Animals; D002232:Carbocyanines / Q000494:pharmacology; D045744:Cell Line, Tumor; D002469:Cell Separation; D003952:Diagnostic Imaging / Q000379:methods; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D005453:Fluorescence; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000096:biosynthesis*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009842:Oligopeptides / Q000378:metabolism; D014054:Tomography / Q000379:methods*
chemical_list: C098793:CY5.5 cyanine dye; D002232:Carbocyanines; D039302:Integrin alphaVbeta3; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid