title: In vivo near-infrared fluorescence imaging of integrin alphavbeta3 in an orthotopic glioblastoma model.
abstract: OBJECTIVE
  Expression of cell adhesion molecule integrin alpha(v)beta(3) is significantly up-regulated during tumor growth, and sprouting of tumor vessels and correlates well with tumor aggressiveness. The purpose of this study was to visualize tumor integrin alpha(v)beta(3) expression in vivo by using near-infrared fluorescence (NIRF) imaging of Cy5.5-linked cyclic arginine-glycine-aspartic acid (RGD) peptide in an orthotopic brain tumor model.
  
  
  METHODS
  U87MG glioma cells transfected with the firefly luciferase gene were stereotactically injected into nude mice in the right frontal lobe. Bioluminescence imaging (BLI) using D: -luciferin substrate and small animal magnetic resonance imaging (MRI) using gadolinium contrast enhancement were conducted weekly after tumor cell inoculation to monitor intracranial tumor growth. Integrin alpha(v)beta(3) expression was assessed by using a three-dimensional optical imaging system (IVIS 200) 0-24 hours after administration of 1.5 nmol monomeric Cy5.5-RGD via the tail vein. Animals were injected intravenously with both Texas Red-tomato lectin and Cy5.5-RGD prior to sacrifice to visualize peptide localization to tumor vasculature using histology.
  
  
  RESULTS
  Fluorescence microscopy demonstrated specific Cy5.5-RGD binding to both U87MG tumor vessels and tumor cells with no normal tissue binding. NIRF imaging showed highest tumor uptake and tumor to normal brain tissue ratio two hours postinjection (2.64 +/- 0.20). Tumor uptake of Cy5.5-RGD was effectively blocked by using unlabeled c(RGDyK), and injection of Cy5.5 dye alone showed nonspecific binding.
  
  
  CONCLUSIONS
  Optical imaging via BLI and NIRF offer a simple, effective, and rapid technique for noninvasive in vivo monitoring and semiquantitative analysis of intracranial tumor growth and integrin alpha(v)beta(3) expression. This study suggests that NIRF via fluorescently labeled RGD peptides may provide enhanced surveillance of tumor angiogenesis and anti-integrin treatment efficacy in orthotopic brain tumor models.
authors.affiliation: Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Hsu
authors.forename: Lewis C
authors.initials: LC
authors.lastname: Hou
authors.forename: Anand
authors.initials: A
authors.lastname: Veeravagu
authors.forename: Joan M
authors.initials: JM
authors.lastname: Greve
authors.forename: Hannes
authors.initials: H
authors.lastname: Vogel
authors.forename: Victor
authors.initials: V
authors.lastname: Tse
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D005260:Female; D005909:Glioblastoma / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence / Q000379:methods*; D009368:Neoplasm Transplantation; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D023041:Xenograft Model Antitumor Assays / Q000379:methods*
chemical_list: D039302:Integrin alphaVbeta3