Tumor-cell-secreted extracellular vesicles (EVs) can cross the disrupted blood-brain barrier (BBB) into the bloodstream. However, in certain gliomas, the BBB remains intact, which might limit EVs release. To evaluate the ability of tumor-derived EVs to cross the BBB, researchers at the HM Hospitals Research Foundation, Spain used an orthotopic xenotransplant mouse model of human glioma-cancer stem cells featuring an intact BBB. They demonstrated that all types of tumor cells-derived EVs-apoptotic bodies, shedding microvesicles and exosomes-cross the intact BBB and can be detected in the peripheral blood, which provides a minimally invasive method for their detection compared to liquid biopsies obtained from cerebrospinal fluid (CSF). Furthermore, these EVs can be readily distinguished from total murine EVs, since they carry human-specific DNA sequences relevant for GBM biology. In a small cohort of glioma patients, these researchers finally demonstrated that peripheral blood EVs cargo can be successfully used to detect the presence of IDH1G395A, an essential biomarker in the current management of human glioma.
Experimental procedure flowchart
A. Isolated hCSCs from 2 GBM patients were xenotransplanted in athymic mice. After 12 weeks, the animals were transcardially perfused. B. BBB permeability was evaluated using three assays: MRI, Evans Blue staining, and albumin extravasation. C. EVs (ABs, SMVs, and EXOs) were isolated from hCSCs-enriched culture supernatants and from mouse peripheral blood. D. EVs were identified using TEM, tracking analysis, and CD63 tetraspanin quantification. E. To ensure that the analyzed DNA was confined within the EVs, supernatants and plasma were treated with DNase before gDNA isolation; after the isolation, gDNA was pre-amplified before performing PCR analysis with human-specific primers. F. Sequences detected were sequenced to confirm their human origin.