Engineering Natural Membrane Vesicle Exosomes As Multifunctional Drug Delivery Platform For Targeted Delivery And Tumor Therapy

Exosomes are nano-sized vesicles (50-100nm in diameter) secreted by numerouscell types including immature dendritic cells (imDCs). They are released into theextracellular medium after fusion of vesicle-containing multivesicular bodies (MVBs)with plasma membrane. Due to their special origin, exosomes have been proved to beone of the important means of exchanging membrane-derived proteins between cells,and play significant roles in immune responses. Meanwhile, exosomes-derived by mastcells are discovered to be able to transfer functional RNAs when entering into therecipient cells, indicating that these vesicles might be an natural shuttle to transfercargos between cells. In fact, exosomes have been developed as natural membraneshuttle to delivery nucleic acid drugs specifically to the targeted cells for the therapy ofAlzheimer’s disease (AD) as well as cancer treatment. Though still in its infancy,exosomes, as a new category of natural drug carriers, have multiple advantages amongthe current drug delivery systems. As exosomes can be derived from the patient’s owncells, they can be less immunogenic when administered to the patients themselves afterloading therapeutic cargos. In addition, compared with classical drug delivery systemssuch as polymeric and lipid nanoparticles, exosomes may transfer their cargos directlyinto the recipient cell cytosol by fusing with the target cell membrane with the help ofexosomal membrane proteins, such as tetraspanin CD9, which can bypass theendosomal-lysosomal pathway associated with almost all nanoparticle-based deliverystrategies and avoiding their potential toxicities.Doxorubicin (Dox) has been widely used for breast cancer treatment after initialsurgery to eliminate the solid tumors and prevent residue breast cancer cells metastasisand relapse. However, administration of Dox is associated with dose-dependentcardiomyopathy and congestive heart failure. As a result, a targeted Dox-delivery isurgently needed to address this severe toxicity. Here we used immature dendritic cells(imDCs)-derived exosomes for the chemotherapeutic drug Dox delivery and breastcancer therapy in nude mice. Exosomes purified from imDCs are less immunogenic dueto the lack of immunostimulatory markers such as CD40, CD86and MHC-II, as in mature dendritic cells. The tumor targeting exosomes were generated by engineering theimDCs to express lysosomal-associated membrane protein2(Lamp2b), an wellcharacterized exosomal membrane protein, fused with the a tumor-homingpeptide-iRGD (CRGDK/RGPD/EC). iRGD not only homes to tumors by binding to avintegrins highly expressed tumor vasculature and tumor cells, but also is a promisingtumor targeting peptide for its enhanced tissue-penetrating ability. The iRGD-Exosshowed high affinity with tumor cells, which overexpress the αv subunit of integrins,both in vitro and in vivo. In addition, iRGD-Exos showed rapid fusion with recipientcell membrane (αv integrin positive), a straight forward strategy to deliver the cargosavoiding the common endocytosis mechanism for nanoparaticle-enabled drug deliverystrategy. After loaded Dox by electroporation, iRGD-Exos-Dox showed very promisingtumor targeting effects, with a dramatic inhibition of human breast cancer xenograftgrowth in vivo. This novel drug delivery strategy based on natural membrane vesicle isworth in-depth development to overcome the current challenges faced by nanoparticledrug carriers. Furthermore, exosomes can directly derived from the patient own cells,and the autologous origin would trigger much less immunogenicity effects andpotentially low or no toxic effects against normal cells as showed in the current study,compared to other type common drug carriers used in clinic or developed for clinicalusage. Moreover, as a novel cell-cell communication strategy, exosomes contain a verylarge amount of endogenous bioactive components, some of which hold great promisingfor future development as potent antitumor agents, combined with exogenoustherapeutic agents to synergistically inhibitor tumor growth, invasion and metastasis.Therefore, the current study demonstrated that a multifunctional drug delivery platformbased on natural biological membrane vesicles were successfully developed for targetedtumor therapy with both high activity and low toxicity. Further development of suchintelligent biomaterials is urgently needed to capitalize the huge potential value inclinical applications.