Non-cationic RGD-containing protein carrier for tumor-targeted siRNA delivery

Abstract Despite the recent successes in siRNA therapeutics, targeted delivery beyond the liver remains the major hurdle for the widespread application of siRNA in vivo. Current cationic liposome or polymer-based delivery agents are restricted to the liver and suffer from off-target effect, poor clearance, low serum stability, and high toxicity. In this study, we have genetically engineered a non-cationic tumor-targeted universal siRNA nanocarrier. This protein nanocarrier consists of three function domains: dsRNA binding domain (dsRBD) (from human protein kinase R) for any siRNA binding, 18-histidines for endosome escape, and two RGD peptides at N-and C-termini for targeting tumor and tumor neovasculature. We showed that cloned dual-RGD-dsRBD-18his (dual-RGD) protein protects siRNA against RNases, induces effective siRNA endosomal escape, specific targets on integrin αvβ3 expressing cells in vitro, and homes siRNA to tumor in vivo. The delivered siRNA leads target gene knockdown in the cell lines and tumor xenografts with low toxicity. This multifunctional, biomimetic, charge-neutral siRNA carrier is biodegradable, low toxic, suitable for mass production by fermentation, and serum stable, holding great potential to provide a widely applicable siRNA carrier for tumor-targeted siRNA delivery.