LB06 - Mesenchymal stem cells shuttle micrornas via extracellular vesicles and prime resistant GBM to caspase mediated apoptosis

Abstract

Mesenchymal stem cell (MSC)-based therapies have yielded beneficial effects in a broad range of animal models of disease and human clinical trials. MSC shed extracellular vesicles and microvesicles into the extracellular space that contain small non-coding RNA molecules, microRNAs (miR). In this study, we engineered MSC to shed exosomes containing microRNA that control cell proliferation and apoptosis in tumors and investigated their potential to prime resistant tumor cells to apoptosis in glioblastoma (GBM) brain tumors. We show that exosomes isolated from engineered MSC are enriched in miR-1 and miR-7and are efficiently transferred into the GMB stem cells (GSC) via exosomes. In order to develop a therapeutic strategy utilizing miRs,,we created constitutive and regulatable miR-7 expression vectors and utilized pharmacological inhibition of caspases and genetic loss of function to study the effect of forced expression of miR-7 on death receptor (DR) pathways in a cohort of death receptor ligand (DRL) resistant established GBM and patient-derived primary GSC. We show that expression of miR-7 results in the up-regulation of death receptor (DR) 5 and primes DRL resistant GBM cells to DRL, tumor necrosis factor apoptosis inducing ligand (TRAIL) mediated apoptotic cell death. In an effort to explore the mechanism underlying the cross talk between miR-7 targeted cell proliferation pathway and TRAIL/death receptor (DR) 4/5 mediated extrinsic apoptotic pathway; we show the interaction between various downstream players involving the NF-kB signaling and their role in up-regulating death receptors thereby priming them to DRLmediated apoptotic cell death. In vivo, we show that miR-7 significantly decreases tumor volumes and when combined with MSC-S-TRAIL, impairs tumor progression and significantly prolongs of mice bearing patient-derived GBM. In conclusion, our findings shed light on the presence anti-tumorgenic miRs in MSC shed exosomes and a unique role of miR-7 in priming resistant GBM cells to DRL mediated apoptosis. This study serves as a foundation for developing therapies utilizing engineered MSC to deliver a combination of microRNA and receptor targeted ligands for cancer therapy.