Epct-25. Smo Protein Depletion in SHH Medulloblastomas Using Microbubble-Enhanced Ultrasound and Sirna Loaded Cationic Nanoparticles

Abstract

RNA-based therapies offer unique advantages for treating pediatric brain tumors. However, the systemic delivery remains a major problem due to degradation of unmodified RNA in biological fluids, poor brain accumulation, and poor cancer cell uptake or escape from the endosomal lipid bilayer barrier. While nanoparticle encapsulation can prolong circulation time and facilitate cellular uptake, their accumulation in brain tumor remains particularly poor due to their low permeability across the blood-brain barrier and limited intratumoral penetration. Focused ultrasound, when combined with circulating microbubbles (MB-FUS) provides a physical method to transiently modulate the brain tumor microenvironment (TME) and improve nanoparticle delivery. Here, we have examined the delivery of siRNA targeting the Smoothened (SMO) pathway, packaged in 50 nm cationic lipid-polymer hybrid nanoparticles (cLPH:siRNA-SMO), combined with MB-FUS in murine SmoA2 sonic hedgehog (SHH) medulloblastoma. At 30 hours after treatment, we observed the depletion of the SMO protein target, responsible for driving SHH medulloblastoma formation and growth, in mice that had received treatment with MB-FUS and cLPH:siRNA-SMO, but not with cLPH:siRNA-SMO alone. We also confirmed that SMO protein depletion was spatially achieved in the tumor regions with detected cLPH:siRNA-SMO using FISH assay, and that there was 15 fold induction of tumor cell apoptosis compared to tumors in mice that had received cLPH:siRNA-SMO alone. The limited induction of apoptosis was observed with either cLPH:siRNA (non-targeting) or MB-FUS and cLPH:siRNA (non-targeting), suggest that the observed apoptosis induction in the SmoA2 model was the direct result of SMO depletion rather than nonspecific effects of MB-FUS or cLPH:siRNA. Our findings provide a paradigm shift in drug delivery in brain tumors, where physical methods and nanotechnology are tuned together to develop rational strategies for the effective delivery of nucleic acids in brain tumors.

Recent progress in nanomedicines for imaging and therapy of brain tumors

“…In pediatric and adult preclinical brain tumor models, delivery of siRNA with 50 nm cationic lipid-polymer hybrid nanoparticles (LPHs:siRNA), combined with microbubble (MB) enhanced focused ultrasound (MB-FUS) resulted in siRNA delivery with more than 10 times improvement into brain tumor microenvironments and remarkably improved survival benefits. 143 In another example, Lopez-Bertoni, Hernando et al (2018) showed that the development of miRNA-containing polymeric nanoparticles exhibits enhanced crossing of the BBB and shows the inhibition effect on the tumor. Furthermore, in vivo co-delivery of both miR-148a and miR-296-5p as multiplexed nano-miRs inhibited the growth of established orthotopic human GBM xenografts in a mouse model, and reduced tumor burden more significantly compared to miRNA delivered alone.…”