title: Vascular endothelial growth factor receptor type 2-targeted contrast-enhanced US of pancreatic cancer neovasculature in a genetically engineered mouse model: potential for earlier detection.
abstract: OBJECTIVE
  To test ultrasonographic (US) imaging with vascular endothelial growth factor receptor type 2 (VEGFR2)-targeted microbubble contrast material for the detection of pancreatic ductal adenocarcinoma (PDAC) in a transgenic mouse model of pancreatic cancer development.
  
  
  METHODS
  Experiments involving animals were approved by the Institutional Administrative Panel on Laboratory Animal Care at Stanford University. Transgenic mice (n = 44; Pdx1-Cre, KRas(G12D), Ink4a(-/-)) that spontaneously develop PDAC starting at 4 weeks of age were imaged by using a dedicated small-animal US system after intravenous injection of 5 × 10(7) clinical-grade VEGFR2-targeted microbubble contrast material. The pancreata in wild-type (WT) mice (n = 64) were scanned as controls. Pancreatic tissue was analyzed ex vivo by means of histologic examination (with hematoxylin-eosin staining) and immunostaining of vascular endothelial cell marker CD31 and VEGFR2. The Wilcoxon rank sum test and linear mixed-effects model were used for statistical analysis.
  
  
  RESULTS
  VEGFR2-targeted US of PDAC showed significantly higher signal intensities (26.8-fold higher; mean intensity ± standard deviation, 6.7 linear arbitrary units [lau] ± 8.5; P < .001) in transgenic mice compared with normal, control pancreata of WT mice (mean intensity, 0.25 lau ± 0.25). The highest VEGFR2-targeted US signal intensities were observed in smaller tumors, less than 3 mm in diameter (30.8-fold higher than control tissue with mean intensity of 7.7 lau ± 9.3 [P < .001]; and 1.7-fold higher than lesions larger than 3 mm in diameter with mean intensity of 4.6 lau ± 5.8 [P < .024]). Ex vivo quantitative VEGFR2 immunofluorescence demonstrated that VEGFR2 expression was significantly higher in pancreatic tumors (P < .001; mean fluorescent intensity, 499.4 arbitrary units [au] ± 179.1) compared with normal pancreas (mean fluorescent intensity, 232.9 au ± 83.7).
  
  
  CONCLUSIONS
  US with clinical-grade VEGFR2-targeted microbubbles allows detection of small foci of PDAC in transgenic mice.
authors.affiliation: From the Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford School of Medicine, Stanford University, 300 Pasteur Dr, Room H1307, Stanford, CA 94305 (M.A.P., S.B.M., J.R., J.K.W.); Department of Pathology, University of California at San Francisco, San Francisco, Calif (E.S.S.); Department of Developmental Biology, Institute for Stem Cell Biology and Regenerative Medicine, Howard Hughes Medical Institute, Stanford School of Medicine, Stanford University, Stanford, Calif (J.J.L.); Department of Medicine, University of Washington, Seattle, Wash (T.A.B.); and Bracco Suisse SA, Geneva, Switzerland (F.T.).
authors.forename: Marybeth A
authors.initials: MA
authors.lastname: Pysz
authors.forename: Steven B
authors.initials: SB
authors.lastname: Machtaler
authors.forename: E Scott
authors.initials: ES
authors.lastname: Seeley
authors.forename: John J
authors.initials: JJ
authors.lastname: Lee
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Brentnall
authors.forename: Jarrett
authors.initials: J
authors.lastname: Rosenberg
authors.forename: François
authors.initials: F
authors.lastname: Tranquart
authors.forename: Jürgen K
authors.initials: JK
authors.lastname: Willmann
mesh_terms: D000818:Animals; D021441:Carcinoma, Pancreatic Ductal / Q000098:blood supply* / Q000737:chemistry / Q000000981:diagnostic imaging*; D003287:Contrast Media; D004195:Disease Models, Animal; D055088:Early Detection of Cancer / Q000379:methods*; D051379:Mice; D008822:Mice, Transgenic; D045423:Microbubbles; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging*; D010190:Pancreatic Neoplasms / Q000098:blood supply* / Q000737:chemistry / Q000000981:diagnostic imaging*; D014463:Ultrasonography; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000032:analysis*
chemical_list: D003287:Contrast Media; D040301:Vascular Endothelial Growth Factor Receptor-2