Extracellular vesicles in glioblastoma: Role in biological processes and in therapeutic applications

Background: Glioblastoma is the most common and malignant form of primary brain cancer; it is characterized by one of the highest mortality among human cancers. Maximal and aggressive surgical resection is the first approach treatment even if not usually definitive, being the tumor characterized by a high proliferative rate and extensive invasion. Early diagnosis, associated to careful monitoring, is pivotal in glioblastoma treatment; Magnetic Resonance Imaging is used for monitoring purpose, but it’s not sensitive enough to detect very small tumors; a valid alternative could be a repeated biopsy, but it is associated to a significant morbidity: less invasive options for diagnosis and therapeutic monitoring are unfailingly researched. Methods: A careful search was performed on PubMed, mainly considering papers in the last 10 years. Conclusion: In recent years it has begun to take hold the knowledge that glioblastoma cells secrete extracellular vesicles (microvesicles and exosomes), which mirror the molecular features of parental cells and are able to escape from tumor microenvironment, reaching cerebrospinal fluid and systemic blood circulation. Such information led to consider the possibility to use extracellular vesicles in biological fluids as markers of glioblastoma pathology and to use them as a more feasible “liquid-biopsy” to gain diagnostic information, follow the disease progression and the response to clinical treatment, just through a blood test or cerebrospinal fluid collection. The most interesting extracellular vesiclesassociated molecules studied as glioblastoma markers are taken into account, as well as approaches aiming to use extracellular vesicles as cell-free vaccines or vehicle of therapeutic molecules.