(485h) Mab-Exo-AAV-Mediated Targeted Gene Therapy to Treat Triple-Negative Breast Cancer

Triple-negative breast cancers (TNBCs) are highly aggressive, metastatic, and heterogeneous, and they often regrow with over 50% of recurrence rate and poor survival after primary treatment and standard chemotherapies. Targeted gene therapy that causes direct cell death could be a promising treatment strategy for TNBCs. Our previous studies and the Cancer Genome Atlas Program (TCGA) database revealed that CD276 is overexpressed on the cell surface of TNBC as an ideal target for targeted therapy. We also established the platforms of adeno-associated virus (AAV)-mediated in vivo gene expression and monoclonal antibody (mAb) surface tagged exosomes (mAb-Exo) for gene delivery. This study aims at developing and evaluating an innovative mAb-Exo-AAV to deliver our mitochondrial LumiOpto therapeutic genes to treat TNBCs. Specifically, Viral Producing Cells engineered from HEK293 were transfected with plasmids of pAAV-LumiOpto, pAAV Rep-Cap and pHelper in stirred-tank bioreactor to produce Exo-AAV, followed by liquid chromatography purification equipped with Core 400 size exclusion column and HiTrap desalting column. The anti-CD276 mAb was produced and conjugated with Exo-AAV via DSPE-PEG-NHS to construct CD276 mAb-Exo-AAV, which was characterized using Dynamic Light scattering, Nanosight, and Zeta-Analysis, and transmission electron microscope (TEM). The In Vivo Imaging System (IVIS), confocal microscope imaging and Western blotting were used to confirm the TNBC-targeting specificity, transduction efficacy, and in vivo gene expression in xenograft mouse models. Finally, the anti-cancer efficacy was confirmed in primary xenograft mouse models and metastatic models. Taken together, an innovative gene therapy and delivery vehicle were developed successfully to treat TNBCs.