Glioblastoma biomarkers in urinary extracellular vesicles reveal the potential for a ‘liquid gold’ biopsy

Biomarkers that reflect glioblastoma tumour activity and treatment response are urgently needed to guide clinical management, particularly for recurrent disease. As the urinary system is a major clearance route of circulating extracellular vesicles (EVs; 30–1000 nm nanoparticles), we explored whether sampling urinary EVs (uEVs) could serve as a simple and non-invasive liquid biopsy approach for measuring glioblastoma-associated biomarkers. Fifty urine specimens (15–60 ml) were collected from 24 catheterised glioblastoma patients immediately prior to primary (n = 17) and recurrence (n = 7) surgeries, following gross total resection (n = 9), and from age/gender-matched healthy participants (n = 14). EVs isolated by differential ultracentrifugation were characterised and proteomes analysed by high-resolution data-independent acquisition liquid chromatography tandem mass spectrometry (DIA-LC-MS/MS). Overall, 6857 proteins were confidently identified in urinary EVs (p ≤ 0.01), including 94 EV marker proteins. Glioblastoma-specific proteomic signatures were determined, and putative uEV biomarkers corresponding to tumour burden and recurrence were identified (fold change ≥ 2, adjusted p ≤ 0.05, AUC > 0.9). DIA-LC-MS/MS characterisation of uEVs substantiates them as a viable source of glioblastoma biomarkers. The promising ‘liquid gold’ biomarker candidates described warrant further investigation.

Susannah M. Hallal, Ägota Tüzes, Liam A. Sida, Elissa Xian, Daniel Madani, Krishna Muralidharan, Brindha Shivalingam, Michael E. Buckland, Laevinya Satgunaseelan, Kimberly L. Alexander