Abstract 357: Dual Anti-Angiogenesis Therapy by Ultrasound-mediated Gene Delivery Decreases Perfusion and Limits Tumor Growth
Background and Hypothesis: Anti-angiogenesis therapies represent an important modality to treat malignant tumors, but can be limited by systemic toxicity. We hypothesized that dual anti-angiogenesis therapy using ultrasound-mediated delivery of shRNA plasmid DNA targeted against VEGFR2 and Tie-2 on tumor vasculature would reduce tumor size and perfusion.
Methods: On day 0, rodent adenocarcinoma cells (250,000 ATCC cells) in 250 μl of matrigel were injected subcutaneously into the left hind limb of F344 rats (n=17). At day 7, 500 μg each of shRNA plasmid targeted against VEGFR2 and Tie-2 along with 1.4 × 109 microbubbles (MicroMarker™ Contrast Agent) were delivered intravenously to tumors during intermittent high power ultrasound (2.0 W/cm2, duty cycle 20%) via the Sonigene System (Vevo 770, Visualsonics) (n=9). Tumor perfusion was evaluated using contrast-enhanced ultrasound (CEU). Tumor size and volume was assessed by imaging and ex vivo volumetric analysis. Post-mortem tissue was collected for histology and PCR.
Results: Tumor dimensions increased in both groups of animals over time, but were less pronounced for shRNA-treated tumors. At day 14, tumor volume in shRNA-treated animals was lower compared to control animals (2.0±0.9 mL vs 3.8±1.1 mL, p<0.05). The % increase in CEU-derived tumor blood volume and blood flow from day 7 to day 14 was significantly greater for control tumors as compared to shRNA-treated tumors (blood volume: 1.5±0.6 vs 0.7±0.4, p<0.01; blood flow 1.3±0.7 vs 0.5±0.5, p<0.05). In shRNA-treated tumors, VEGFR2 and Tie-2 expression by PCR was reduced compared to control animals.
Conclusions: Dual gene transfer of shRNA plasmid targeting VEGFR2 and Tie-2 by ultrasound-mediated delivery reduces angiogenesis and limits tumor growth in an adenocarcinoma tumor model.