Microbubble-Enhanced Focused Ultrasound Improves Targeted Adeno-Associated Virus Delivery in Brain Tumors Quantified by PET Imaging

Abstract Gene therapy using adeno-associated virus (AAV) vectors shows promise for cancer treatment through molecular intervention, yet achieving sufficient and targeted delivery to brain tumors via systemic administration remains limited by the biological barriers. Here, we investigate whether microbubble-enhanced focused ultrasound (MB-FUS) improves targeted delivery of systemically administered AAV9 to orthotopic gliomas, using quantitative PET imaging of 64 Cu-radiolabeled AAV9 vectors and fluorescent reporter expression to assess biodistribution and functional efficacy. At 21 hours after injection, 64 Cu-AAV9 accumulation was 3.2-fold higher in FUS-treated tumors compared to non-FUS-treated tumors (n=3, p=0.004). Quantitative PCR analysis of tumor tissue at the same timepoint confirmed a 6.4-fold increase in genome copies in FUS-treated tumors (p=0.0003). The enhanced vector delivery translated to a 5.3-fold increase in optical reporter protein expression in FUS-treated compared to control tumors (p=0.0002) at 17 days post-treatment. These results establish that MB-FUS enables spatially-targeted AAV delivery with quantifiable enhancement in both acute vector biodistribution and downstream transgene expression. The integration of radiolabeled AAV with PET imaging provides a non-invasive methodology for real-time assessment of vector delivery and optimization of treatment protocol for brain cancer gene therapy. Highlights MB-FUS enables targeted systemic AAV delivery to brain tumors. MB-FUS enhanced vector delivery translates to increased transgene expression in gliomas. PET imaging of radiolabeled AAV allows non-invasive tracking of gene therapy vectors. Real-time imaging validates spatially-controlled gene delivery for brain cancer.