Clinical Significance of Extracellular Vesicles in Plasma from Glioblastoma Patients

Abstract

Purpose: Glioblastoma (GBM) is the most common primary brain tumor. The identification of blood biomarkers reflecting the tumor status represents a major unmet need for optimal clinical management of patients with GBM. Their high number in body fluids, their stability, and the presence of many tumor-associated proteins and RNAs make extracellular vesicles potentially optimal biomarkers. Here, we investigated the potential role of plasma extracellular vesicles from patients with GBM for diagnosis and follow-up after treatment and as a prognostic tool. Experimental Design: Plasma from healthy controls (n ¼ 33), patients with GBM (n ¼ 43), and patients with different central nervous system malignancies (n ¼ 25) were collected. Extracellular vesicles were isolated by ultracentrifugation and characterized in terms of morphology by transmission electron microscopy, concentration, and size by nanoparticle tracking analysis, and protein composition by mass spectrometry. An orthotopic mouse model of human GBM confirmed human plasma extracellular vesicle quantifications. Associations between plasma extracellular vesicle concentration and clinicopathologic features of patients with GBM were analyzed. All statistical tests were two-sided. Results: GBM releases heterogeneous extracellular vesicles detectable in plasma. Plasma extracellular vesicle concentration was higher in GBM compared with healthy controls (P < 0.001), brain metastases (P < 0.001), and extra-axial brain tumors (P < 0.001). After surgery, a significant drop in plasma extracellular vesicle concentration was measured (P < 0.001). Plasma extracellular vesicle concentration was also increased in GBM-bearing mice (P < 0.001). Proteomic profiling revealed a GBM-distinctive signature. Conclusions: Higher extracellular vesicle plasma levels may assist in GBM clinical diagnosis: their reduction after GBM resection, their rise at recurrence, and their protein cargo might provide indications about tumor, therapy response, and monitoring.

Circulating biomarkers in patients with glioblastoma

“…When comparing EV concentrations over different time points, an increase in EV concentrations correlated with tumour recurrence, suggesting that exosomes could help to predict GBM recurrence. 120 Similarly, Andre-Gregoire et al 121 observed a higher concentration of EVs in patients with GBM, as well as showing that EVs from patientderived glioblastoma stem cells, which are thought to be involved in tumour initiation, expansion, resistance to treatments and relapse, had increased cargo relating to cell adhesion after TMZ treatment, indicating that TMZ had the potential to promote the increased release of factors favouring tumour progression. 121 Manda et al 124 123 Also, the presence of EGFRvIII in exosomes correlated with a lower overall survivor pattern-21.1 months-compared with 28.6 months for patients with no EGFRvIII expression in exosomes.…”

“…The authors also concluded that GBM cells shed MVs, and that their contentthat included angiogenic proteins in addition to EGFRvIII-can enhance the angiogenic phenotype of normal brain endothelial cells and proliferation in other glioma cells. 119 Exosomes in glioblastoma Osti et al 120 demonstrated that the concentration of EVs was increased in GBM patients in comparison with healthy controls and patients with other CNS diseases. When comparing EV concentrations over different time points, an increase in EV concentrations correlated with tumour recurrence, suggesting that exosomes could help to predict GBM recurrence.…”

Splicing Dysregulation as Oncogenic Driver and Passenger Factor in Brain Tumors

“…Cortactin has been also implicated in release of extracellular vesicles (EVs) in the TME [98]. EVs are key messengers of intercellular communications that control the establishment and maintenance of TME [99], are actively secreted by GBM cells, and promote their oncogenic features [100][101][102][103]. For instance, GBM-secreted EVs stimulate recipient astrocytes to acquire a pro-tumoral phenotype by delivering several factors, including MYC and MYCN [101].…”

Monitoring Therapy Efficiency in Cancer through Extracellular Vesicles

“…Characterizing the protein cargo of plasma EVs in patients with GBM and healthy controls through a MS-based proteomic analysis revealed a GBM-distinctive signature. These findings indicated that measurement of plasma EV concentrations together with the possibility to characterize their specific cargo can be of assistance in diagnosis, treatment, and follow-up of GBM patients [35].…”

“…Tumor-specific EVs were detected in a syngeneic mouse tumor model [49]. Osti et al [35] ( Table 1) analyzed plasma EVs (microvesicles) in preoperative GBM samples. EVs concentration significantly declined after resection of the primary GBM and raised with tumor relapse.…”