Image-guided Strategies to Improve Neuroblastoma Treatment

Neuroblastoma (NB) is a pediatric malignancy that accounts for 15% of cancer-related childhood mortality. High-risk NB requires an aggressive chemoradiotherapy regimen that causes significant off-target toxicity. In spite of these invasive treatment measures, many patients do not respond adequately or experience relapse after initial therapy. Boosting efficacy and reducing morbidity are therefore key goals of treatment for afflicted children. We hypothesized that these could be achieved by developing strategies to both focus and limit toxic therapies to the region of the tumor. One such approach is the use of targeted image-guided drug delivery (IGDD), which is growing in popularity in personalized therapy to simultaneously improve on-target drug deposition and assess drug pharmacodynamics in individual patients. Over the last two decades, IGDD using focused ultrasound with “microbubble” ultrasound contrast agents (UCAs) has been increasingly explored as a method of targeting a wide variety of diseases, including cancer. This technique, known as sonopermeation, mechanically permeabilizes the vascular endothelium, enabling increased penetration of drugs into target tissue. However, to date, methods of monitoring the vascular bioeffects of sonopermeation in vivo are lacking. UCAs are excellent vascular probes in contrast-enhanced ultrasound (CEUS) imaging and are thus uniquely suited to track the effects of sonopermeation in tumors. Recent studies further suggest that augmenting tumor vascularity permits enhanced drug uptake and distribution within tumor tissue. Methods of transiently increasing tumor perfusion prior to treatment could therefore be beneficial in the treatment of this disease. Here we report the use of gene therapy to regulate nitric oxide synthase (NOS) expression in the tumor vasculature. NOS catalyzes the chemical reaction that generates nitric oxide (NO), a potent endogenous vasodilator. Our goal was to rationally design a state-of-the-art, non-viral platform to efficiently deliver NOS-expressing plasmids to cells lining the tumor blood vessels. To construct this gene delivery vehicle, we utilized cationic UCAs to carry plasmid DNA (pDNA) in circulation and transfect tumor vascular endothelial cells in vivo using focused ultrasound (FUS) energy. Our results suggest that significant drug uptake occurs by improving tumor vascular permeability with microbubble sonopermeation without damaging the vasculature. We have thus conceived a clinically viable methodology for improving neuroblastoma response to treatment by successfully effecting increases in tumor perfusion volume and tumoral blood flow rates.