Potential Biomarkers Found in Glioblastoma Small Extracellular Vesicles

Tumor small extracellular vesicles (sEVs), which are accessible in biofluids such as blood, contain valuable biomarkers for glioblastoma (GBM) patient diagnosis and follow-up.

Glioblastoma is the most common primary tumor of the central nervous system and is almost always fatal. The aggressive invasion of glioblastoma cells into the surrounding normal brain makes complete surgical removal impossible, significantly increases resistance to the standard therapy regimen, and virtually assures tumor recurrence. Treatment of glioblastoma usually comprises surgical removal of the tumor followed by radiation treatment and chemotherapy using the drug temozolomide (TMZ). However, the penetration of the tumor into adjacent brain tissue prevents the surgical removal of all tumor cells, which usually develop resistance to TMZ.

Small extracellular vesicles (sEVs) produced by both GBM and stromal cells are central in the inter-cellular communication that is taking place within the tumor microenvironment. EVs, which include exosomes, microvesicles, and apoptotic bodies, are cell-derived lipid-bilayer-enclosed structures, with sizes ranging from 30 to 5,000 nanometers. In the past decade, EVs have emerged as important mediators of cell communication because they serve as vehicles for the intercellular transmission of biological signals (proteins or nucleic acids) capable of altering cell function and physiology.

Investigators at the University of Sussex (United Kingdom) undertook the current study to describe the protein content of sEVs produced by different GBM cell lines and patient-derived stem cells.

Results revealed that the content of the sEVs mirrored the phenotypic signature of the respective GBM cells, leading to the description of potential informative sEV-associated biomarkers for GBM subtyping, such as CD44. Coupled with noninvasive liquid biopsy techniques, the use of sEV biomarkers is esxpected to provide insights for the development of new diagnostic and therapeutic methods as well as personalized treatment strategies.

Senior author Dr. Georgios Giamas, professor of cancer cell signaling at the University of Sussex, said, "At the moment, the outlook for glioblastoma patients is bleak. As the most aggressive type of brain tumor, survival rate is low. Our research provides more information about the markers which can signal the presence of glioblastoma - and the fact we have been able to identify ones that are associated with extracellular vesicles, suggests that there could be a way to use bodily fluids to test for the tumor in future."

The GBM sEVs paper was published in the August 19, 2019, online edition of the journal Communications Biology.

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