Exosome–Based Cell Free Vaccine: An Alternative To DC- Based Cancer Immunotherapy

In addition to cytokines and growth factors, all cells secrete a large amount of membrane vesiclesinto the extracellular environment that modulate the function of the other cells. The mostprominent of the extracellular vesicles are exosomes. Exosomes are nano vesicles (30–100 nm)derived from the late endosomal membrane structures and play an important role in intercellularcommunication by transferring cargo molecules including proteins, lipids and genetic materials(such as mRNA, microRNA and other non-coding RNAs). It has been observed that a wide range ofcell types secrete exosomes, including macrophages, dendritic cells (DCs), B cells, cytotoxic Tlymphocytes (CTLs), platelets, mastocytes, fibroblasts, epithelial cells, and tumor cells. DCs are themost potent antigen presenting cells for activation of tumor specificc CTLs which identify andeliminate cancer cells. In case of DC vaccine, mostly, peptides, RNA or whole tumor cell lysate areused as an antigen for pulsing DCs and activated DCs can elicit a specific CTL response againsttumor cells. Also recent studies showed that tumor-derived exosomes can be implemented as a newsource of tumor antigen for DC stimulation and induction of immune response.It is shown that DC–derived exosomes (Dex) have similar biology to DCs and have the capacity to induce potent immuneresponses. Moreover, Dex is more stable than DCs because of their lipid composition. As well theyare enriched in active peptide-MHC II complexes and are not reliant on chemotactic signaling hencethey can access their target organ easily. These characteristics give Dex an advantage over DC cellbased cancer immunotherapy. Although Dex is considered as an important candidate for clinicaltrial but their effect has only been shown on malignant tumors including non-small cell lungcarcinoma and metastatic melanoma.In conclusion exosome based cell free vaccine can be used as anew approach in cancer therapy and its effect on other cancers should be more investigated.