1058. Adeno-Associated Virus Serotype 6 (AAV-6) Vector Mediated Gene Transfer of Soluble VEGF Receptors for the Treatment of Glioblastoma Multiforme
Authors: Thomas C. Harding, Alshad S. Lalani, Jian Min Lin, Satyasri Yendluri, Bo Luan, Kathryn E. Koprivnikar, Guang Tu, Melissa A. Gonzalez-Edick, Wei Wei Wu-Prior, Melinda VanRoey, Byron Roberts, Richard LeCouter, Pete Dickinson, Karin Jooss
Journal: Molecular Therapy (2004)

Glioblastoma Multiforme (GBM) is the most common primary brain tumor leading to more than 12,000 deaths per year in the US. Radiation and chemotherapy has achieved limited success in the treatment of GBM and gene therapy may be a promising new strategy. We have investigated the gene transfer efficiencies of AAV serotypes –2, -5 and –6 encoding GFP in the murine CNS. AAV vectors derived from serotype 6 using the strong constitutive CAG promoter provide the optimum transduction efficiency in both the absence (normal brain) and presence of tumor (murine 4C8 glioma and human U87 glioma) in the murine brain. Following this work, the therapeutic potential of recombinant AAV-6 gene delivery of soluble forms of the human vascular endothelial growth factor receptors (sVEGFR) for blocking glioma growth in vivo following local (intra-tumoral) and systemic administration was investigated. Initially, soluble forms of VEGFR1 (domains 1-7) and VEGFR2 (domains 1-7) were constructed by fusion to an Fc segment of human IgG1, however, both receptors showed minimal efficacy in inhibiting subcutaneous C6 (rat glioma) and U87 glioma tumors following expression in vivo. To address this lack of efficacy, a chimeric soluble VEGF receptor was constructed, comprising of domains from VEGFR1 and VEGFR2 linked to IgG1 Fc, termed sVEGFR1/2. Assays in vitro and in CAM demonstrated that the sVEGFR1/2 molecule has VEGF binding affinities comparable to that of VEGFR1 coupled with the favorable bioavailability of the sVEGFR2 receptor. Furthermore, the sVEGFR1/2 molecule completely prevented tumor progression >80 days post-tumor implantation in comparison to the control group in a murine sub-cutaneous U87 human glioma model and demonstrated similar efficacy in the C6 model. The potency of a recombinant AAV-6 vector encoding the sVEGFR1/2 transgene to treat orthotopic murine 4C8 glial tumors in BFD2F1 immuno-competent mice was then examined. Animals received AAV-VEGFR1/2 delivered intra-tumorally by stereotaxic injection into pre-established (7-day) 4C8 tumors. Thirty days post-tumor implantation, animals treated with AAV6-VEGFR1/2 vector showed > 80% decrease in tumor growth in comparison to control animals as assessed by MRI. Survival was also significantly extended by treatment with the soluble chimeric VEGF receptor expressed from the AAV-6 vector. In addition, the efficacy of systemic sVEGFR1/2 expression following AAV mediated gene transfer to the liver on orthotopic 4C8 tumor growth was compared to local delivery to determine the impact of the blood brain barrier of the efficacy of the transgene. This work suggests that local delivery of a potent anti-VEGF agent by AAV-6 mediated gene transfer may be a novel and effective strategy for blocking the growth of human glioma tumors in vivo and may present a niche in which local gene therapy has advantage over systemic protein therapies.