Mesenchymal stem cell-derived small extracellular vesicles as a delivery vehicle of oncolytic reovirus

Aim: The oncolytic reovirus has demonstrated efficacy against various cancer types in preclinical and clinical studies. However, its anti-tumor activity is limited. This study aimed to develop a novel drug delivery system (DDS) using small extracellular vesicles (sEVs) derived from human adipose-derived mesenchymal stem cells to enhance the therapeutic potential of reovirus. Materials and methods: sEVs, which offer distinct advantages over traditional systems such as nanoparticles due to their natural biocompatibility, low immunogenicity, ability to cross biological barriers, and cell-derived targeting properties, were engineered to encapsulate reovirus particles (sEVs-reo). The anti-tumor activity of sEVs-reo was evaluated using colorectal cancer cell lines HCT116 and SW480. Additionally, resistance to neutralizing antibodies, internalization by cancer cells, and efficacy against junctional adhesion molecule-A(JAM-A)-knockout colon cancer cells resistant to reovirus, generated via CRISPR/Cas9, were assessed. Key findings: sEVs-reo encapsulated reovirus particles effectively, and at a concentration of 0.5 mu g/ml, reduced viable tumor cells by 60.3 % in HCT116 and 42.5 % in SW480. Remarkably, sEVs-reo exhibited significant efficacy even in the presence of neutralizing antibodies, including anti-a1 antibodies and serum from reovirusinfected mice. sEVs-reo were rapidly internalized by cancer cells within 4 h while exhibiting reduced immunogenicity relative to reovirus, and demonstrated significant anti-tumor activity against JAM-A-deficient colon cancer cells. Significance: This study demonstrates that sEVs-reo can address key challenges associated with oncolytic virotherapy. These findings support potential of sEVs as a novel and effective DDS for reovirus in colon cancer treatment, while offering a versatile platform to enhance the efficacy of other oncolytic viruses.