title: Noninvasive assessment of gene transfer and expression by in vivo functional and morphologic imaging in a rabbit tumor model.
abstract: OBJECTIVE
  To evaluate the importance of morphology in quantifying expression after in vivo gene transfer and to compare gene expression after intra-arterial (IA) and intra-tumoral (IT) delivery of adenovirus expressing a SSTR2-based reporter gene in a large animal tumor model.
  
  
  METHODS
  Tumor directed IA or IT delivery of adenovirus containing a human somatostatin receptor type 2A (Ad-CMV-HA-SSTR2A) gene chimera or control adenovirus (Ad-CMV-GFP) was performed in VX2 tumors growing in both rabbit thighs. Three days later, ¹¹¹In-octreotide was administered intravenously after CT imaging using a clinical scanner. ¹¹¹In-octreotide uptake in tumors was evaluated the following day using a clinical gamma-camera. Gene expression was normalized to tumor weight with and without necrosis. This procedure was repeated on nine additional rabbits to investigate longitudinal gene expression both 5 days and 2 weeks after adenovirus delivery. CT images were used to evaluate tumor morphology and excised tissue samples were analyzed to determine ¹¹¹In-octreotide biodistribution ex vivo.
  
  
  RESULTS
  VX2 tumors infected with Ad-CMV-HA-SSTR2 had greater ¹¹¹In-octreotide uptake than with control virus (P<0.05). Intra-arterial and intra-tumoral routes resulted in similar levels of gene expression. Longitudinally, expression appeared to wane at 2 weeks versus 5 days after delivery. Areas of necrosis did not demonstrate significant uptake ex vivo. Morphology identified areas of necrosis on contrast enhanced CT and upon excluding necrosis, in vivo biodistribution analysis resulted in greater percent injected dose per gram (P<0.01) and corresponded better with ex vivo biodistribution(r = 0.72, P<0.01, Coefficient of the x-variable = .72) at 2 weeks than without excluding necrosis (P<0.01).
  
  
  CONCLUSIONS
  Tumor specificity and high transgene expression can be achieved in tumors via both tumor directed intra-arterial and intra-tumoral delivery in a large animal tumor model. Using clinical machines, morphologic imaging contributes to functional imaging for quantifying SSTR2-based reporter expression in vivo.
authors.affiliation: Department of Experimental Diagnostic Imaging, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America.
authors.forename: Murali K
authors.initials: MK
authors.lastname: Ravoori
authors.forename: Lin
authors.initials: L
authors.lastname: Han
authors.forename: Sheela P
authors.initials: SP
authors.lastname: Singh
authors.forename: Katherine
authors.initials: K
authors.lastname: Dixon
authors.forename: Jyoti
authors.initials: J
authors.lastname: Duggal
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Rajesh
authors.initials: R
authors.lastname: Uthamanthil
authors.forename: Sanjay
authors.initials: S
authors.lastname: Gupta
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Wright
authors.forename: Vikas
authors.initials: V
authors.lastname: Kundra
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D015153:Blotting, Western; D018196:Carcinoma, Adenosquamous / Q000235:genetics / Q000473:pathology* / Q000628:therapy; D004333:Drug Administration Routes; D015902:Gamma Cameras; D018014:Gene Transfer Techniques; D017930:Genes, Reporter / Q000502:physiology; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000008:administration & dosage*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D007269:Injections, Intra-Arterial; D015552:Injections, Intralesional; D009336:Necrosis; D015282:Octreotide / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D011817:Rabbits; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000235:genetics* / Q000378:metabolism; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon; D019076:Transgenes / Q000502:physiology; D047368:Tumor Burden; D014407:Tumor Cells, Cultured
chemical_list: D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C094279:indium-111-octreotide; D049452:Green Fluorescent Proteins; C093733:somatostatin receptor 2; D015282:Octreotide