title: Dual-targeted contrast agent for US assessment of tumor angiogenesis in vivo.
abstract: OBJECTIVE
  To develop and validate a dual-targeted ultrasonographic (US) imaging agent with microbubbles (MBs) that attaches to both vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) and alpha(v)beta(3) integrin and to compare the US imaging signal obtained from dual-targeted MBs (MB(D)) with that from single-targeted MBs (MB(S)) in a murine model of tumor angiogenesis.
  
  
  METHODS
  Animal protocols were approved by the institutional Administrative Panel on Laboratory Animal Care. Single- and dual-targeted US imaging agents were prepared by attaching anti-VEGFR2, anti-alpha(v)beta(3) integrin, or both antibodies to the shell of perfluorocarbon-filled MBs. Binding specificities of targeted MBs compared with isotype-matched immunoglobulin G-labeled control MBs (MB(C)) and nontargeted nonlabeled MBs (MB(N)) were tested with VEGFR2-positive and alpha(v)beta(3) integrin-positive cells (mouse SVR cells) and control cells (mouse 4T1 cells). In vivo imaging signals of contrast material-enhanced US by using anti-VEGFR2-targeted MBs (MB(V)), anti-alpha(v)beta(3) integrin-targeted MBs (MB(I)), MB(D), and MB(C) were quantified in 49 mice bearing SK-OV-3 tumors (human ovarian cancer). Tumor tissue was stained for VEGFR2, alpha(v)beta(3) integrin, and CD31.
  
  
  RESULTS
  Attachment of MB(D) to SVR cells (mean, 0.74 MBs per cell +/- 0.05 [standard deviation]) was significantly higher than attachment to 4T1 cells (mean, 0.04 +/- 0.03), and attachment to SVR cells was higher for MB(D) than for MB(V) (mean, 0.58 +/- 0.09), MB(I) (mean, 0.42 +/- 0.21), MB(C) (mean, 0.11 +/- 0.13), and MB(N) (mean, 0.01 +/- 0.01) (P < .05). Imaging signal in the murine tumor angiogenesis model was significantly higher (P < .001) for MB(D) (mean, 16.7 +/- 7.2) than for MB(V) (mean, 11.3 +/- 5.7), MB(I) (mean, 7.8 +/- 5.3), MB(C) (mean, 2.8 +/- 0.9), and MB(N) (mean, 1.1 +/- 0.4). Immunofluorescence confirmed expression of VEGFR2 and alpha(v)beta(3) integrin on tumor vasculature.
  
  
  CONCLUSIONS
  Dual-targeted contrast-enhanced US directed at both VEGFR2 and alpha(v)beta(3) integrin improves in vivo visualization of tumor angiogenesis in a human ovarian cancer xenograft tumor model in mice.
  
  
  BACKGROUND
  http://radiology.rsnajnls.org/cgi/content/full/248/3/936/DC1.
authors: Molecular Imaging Program at Stanford, Department of Radiology and Bio-X Program, Stanford University School of Medicine, the James H Clark Center, 318 Campus Dr, East Wing, 1st Floor, Stanford, CA 94305-5427, USA.
authors: Jürgen K
authors: JK
authors: Willmann
authors: Amelie M
authors: AM
authors: Lutz
authors: Ramasamy
authors: R
authors: Paulmurugan
authors: Manishkumar R
authors: MR
authors: Patel
authors: Pauline
authors: P
authors: Chu
authors: Jarrett
authors: J
authors: Rosenberg
authors: Sanjiv S
authors: SS
authors: Gambhir
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000378:metabolism*; D016503:Drug Delivery Systems / Q000379:methods; D005260:Female; D006801:Humans; D007089:Image Enhancement; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D045423:Microbubbles; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging* / Q000378:metabolism*; D010051:Ovarian Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D003287:Contrast Media; D039302:Integrin alphaVbeta3; D040301:Vascular Endothelial Growth Factor Receptor-2