Angiotensin II increases gene expression after selective intra-arterial adenovirus delivery in a rabbit model assessed using in vivo SSTR2-based reporter imaging

Angiotensin II increases gene expression after selective intra-arterial adenovirus delivery in a rabbit model assessed using in vivo SSTR2-based reporter imaging

EJNMMI Research, March 2016

26983635

Sheela P. Singh, Murali K. Ravoori, Katherine A. Dixon, Lin Han, Sanjay Gupta, Rajesh Uthamanthil, Kenneth C. Wright, Vikas Kundra

Gene therapy has been hampered by low expression upon in vivo delivery. Using a somatostatin receptor type 2 (SSTR2)-based reporter, we assessed whether angiotensin II (AII) can improve gene expression by adenovirus upon intra-arterial (IA) delivery in a large animal model. A SSTR2-based reporter that can be imaged by a clinically approved radiopharmaceutical was used to assess gene expression. Eight rabbits bearing VX2 tumors in each thigh were randomly injected IA with adenovirus containing a human SSTR2 (Ad-CMV-HA-SSTR2) gene chimera ± AII or control adenovirus containing green fluorescent protein (Ad-CMV-GFP). Three days later, (111)In-octreotide was given IV after computed tomography (CT) imaging using a clinical CT scanner and intravenous contrast. Tumor uptake of (111)In-octreotide was evaluated the next day using a clinical gamma camera. Gene expression was normalized to tumor weight and morphology from CT to obtain in vivo biodistribution. SSTR2-based expression was readily visualized. VX2 tumors infected with Ad-CMV-HA-SSTR2 upon intra-arterial delivery with AII had greater in vivo biodistribution, thus greater gene expression, than those without AII (p < 0.01, n = 6). VX2 tumors infected with Ad-CMV-HA-SSTR2 upon IA delivery had greater biodistribution, thus greater gene expression, than those with the negative control Ad-CMV-GFP (p < 0.02). Similarly, VX2 tumors infected with Ad-CMV-HA-SSTR2 upon IA delivery with AII had greater biodistribution, thus greater gene expression, than those with the negative control Ad-CMV-GFP (p < 0.01). Angiotensin II improves in vivo gene expression by adenovirus upon intra-arterial delivery and thus may improve gene therapy efficacy. In vivo SSTR2-based reporter imaging can be used to compare methodologies for improving gene expression.