Nucleolin-targeted Extracellular Vesicles As A Versatile Platform For MicroRNA/siRNA Delivery To Breast Cancer

Small interfering RNAs(siRNA)/microRNAs(miRNA)have promising therapeutic potential,yet their clinical application has been hampered by the lack of appropriate delivery systems.Herein,we employed extracellular vesicles(EVs)as a targeted delivery system for small RNAs.EVs are cell-derived small vesicles that participate in cell-to-cell communication for protein and RNA delivery.We used the aptamer AS1411-modified EVs for targeted delivery of siRNA/microRNA to breast cancer tissues.Tumor targeting was facilitated via AS1411 binding to nucleolin,which is highly expressed on the surface membrane of breast cancer cells.This delivery vesicle targeted let-7 miRNA delivery to MDA-MB-231 cells in vitro as confirmed with fluorescent microscopic imaging and flow cytometry.Also,intravenously delivered AS1411-EVs loaded with miRNA let-7 labeled with the fluorescent marker,Cy5,selectively targeted tumor tissues in tumor-bearing mice and inhibited tumor growth.Importantly,the modified EVs were well tolerated and showed no evidence of nonspecific side effects or immune response.Furthermore,we chose the microRNA let-7 and siRNA-VEGF as behalf of microRNA and siRNA to determine the complex’s effect on breast cancer cells in vitro and in vivo.The result of Q-PCR and Western Blot Assays showed the expression of K-RAS and cMyc which the target gene of mircroRNA let-7,and VEGF which the target gene of siRNA-VEGF,have down regulation.Moreover,the tumor growth in mice was significantly inhibited after treatment of let-7 by using AS1411-EVs as targeted delivery.Thus,the RNAi nanoplatform is versatile and can deliver siRNA or miRNA to breast cancer cells both in vitro and in vivo.Our results suggest that the AS1411-EVs have a great potential as drug delivery vehicles to treat cancers.