P. S. Jones, A. Yekula, E. Lansbury, J. L. Small, C. Ayinon, S. Mordecai, F. H. Hochberg, J. Tigges, B. Delcuze, A. Charest, I. Ghiran, L. Balaj, and B. S. Carter. Characterization of plasma-derived protoporphyrin-IX-positive extracellular vesicles following 5-ALA use in patients with malignant glioma. EBioMedicine, 48:23–35, Oct 2019. [PubMed Central:\href https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6838454PMC6838454] [DOI:\href https://dx.doi.org/10.1016/j.ebiom.2019.09.02510.1016/j.ebiom.2019.09.025] [PubMed:\href https://www.ncbi.nlm.nih.gov/pubmed/1249361012493610].


Malignant gliomas are rapidly progressive brain tumors with high mortality. Fluorescence guided surgery (FGS) with 5-aminolevulinic acid (5-ALA) provides fluorescent delineation of malignant tissue, which helps achieve maximum safe resection. 5-ALA-based fluorescence is due to preferential accumulation of the fluorophore protoporphyrin-IX (PpIX) in malignant glioma tissue. Additionally, gliomas cells release extracellular vesicles (EVs) which carry biomarkers of disease. Herein, we performed animal and human studies to investigate whether 5-ALA dosed glioma cells, in vitro and in vivo, release PpIX positive EVs in circulation which can be captured and analyzed.\\ We used imaging flow cytometry (IFC) to characterize PpIX-positive EVs released from 5-ALA-dosed glioma cells, glioma-bearing xenograft models, as well as patients with malignant glioma undergoing FGS.\\ We first show that glioma cells dosed with 5-ALA release 247-fold higher PpIX positive EVs compared to mock dosed glioma cells. Second, we demonstrate that the plasma of glioma-bearing mice (n = 2) dosed with 5-ALA contain significantly higher levels of circulating PpIX-positive EVs than their pre-dosing background (p = 0.004). Lastly, we also show that the plasma of patients with avidly fluorescent tumors (n = 4) undergoing FGS contain circulating PpIX-positive EVs at levels significantly higher than their pre-dosing background (p = 0.00009) and this rise in signal correlates with enhancing tumor volumes (r 2 = 0.888).\\ Our findings highlight the potential of plasma-derived PpIX-positive EV-based diagnostics for malignant gliomas, offering a novel liquid biopsy platform for confirming and monitoring tumor status.