Abstract

Exosome (EV)-mediated Specific Gene Delivery (as mRNA) to Cause Specific Suicide of HER2-positive Breast Cancer by the New Prodrug CNOB

A. C. Matin, Professor, Stanford University

CNOB is a harmless prodrug, which is converted into highly cytotoxic MCHB upon reduction by the enzyme hChrR6. Based on the fact that the c1-c2 domains of lactadherin attach to the surface of EVs, chimeric proteins have been prepared that direct the EVs to the HER2 ligand and make the targeting visualizable. As mRNA is superior to DNA for gene delivery, we use hChrR6 mRNA to load the directed EVs for gene delivery. The “loaded” EVs were initially generated using the mRNA ‘zipcode’ and a special plasmid constructed in collaboration with SBI; but for superior clinically usable approach, it is now done using self-delivering in vitro synthesized hChrR6 mRNA. Addition of 3’UTR of ß-globin to this mRNA enhanced its EV-mediated delivery to HER2+ve cells by over two-fold, generating their greater killing by CNOB. In collaboration with University of Massachusetts, cholesterol interspersed hChrR6 mRNA segments that pair with specific regions of the complete mRNA have been generated to further enhance its direct introduction into the EVs. In preliminary studies, mice with implanted orthotopic HER2+ve tumors responded well to treatment with directed and loaded EVs and CNOB.