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Background: In glioblastoma (GB), tissue is required for accurate diagnosis and subtyping. Tissue can be obtained through resection or (stereotactic) biopsy, but these invasive procedures provide risks for patients. Extracellular vesicles (EVs) are small, cell-derived vesicles that contain miRNAs, proteins, and lipids, and possible candidates for liquid biopsies. GB-derived EVs can be found in the blood of patients, but it is difficult to distinguish them from circulating non-tumor EVs. 5-aminolevulinic acid (5-ALA) is orally administered to GB patients to facilitate tumor visualization and maximal resection, as it is metabolized to fluorescent protoporphyrin IX (PpIX) that accumulates in glioma cells. In this study, we assessed whether PpIX accumulates in GB-derived EVs and whether these EVs could be isolated and characterized to enable a liquid biopsy in GB. Methods: EVs were isolated from the conditioned media of U87 cells treated with 5-ALA by differential ultracentrifugation. Blood samples were collected and processed from healthy controls and patients undergoing 5-ALA guided surgery for GB. High-resolution flow cytometry (hFC) enabled detection and sorting of PpIX-positive EVs, which were subsequently analyzed by digital droplet PCR (ddPCR).Results:PpIX-positive EVs could be detected in conditioned cell culture media as well as in patient samples after administration of 5-ALA. By using hFC, we could sort the PpIX-positive EVs for further analysis with ddPCR, which indicated the presence of EVs and GB-associated miRNAs. Conclusion: GB-derived EVs can be isolated from the plasma of GB patients by using 5-ALA induced fluorescence. Although many challenges remain, our findings show new possibilities for the development of blood-based liquid biopsies in GB patients.

Introduction: Glioma cells exert influence over the tumor-microenvironment in part through the release of extracellular vesicles (EVs), membrane-enclosed structures containing proteins, lipids, and RNAs. In this study, we evaluated the function of Ras-associated protein 27a (Rab27a) in glioma and evaluated the feasibility of assessing its role in EV release in glioma cells in vitro and in vivo. Methods: Rab27a was knocked down via a short hairpin RNA (shRNA) stably expressed in mouse glioma cell line GL261, with a scrambled shRNA as control. EVs were isolated by ultracentrifugation and quantified with Nanoparticle Tracking Analysis (NTA) and Tunable Resistive Pulse Sensing (TRPS). CellTiter-Glo viability assays and cytokine arrays were used to evaluate the impact of Rab27a knockdown. GL261.shRab27a cells and GL261.shControl were implanted into the left striatum of eight mice to assess tumor growth and changes in the tumor microenvironment. Results:Knockdown of Rab27a in GL261 glioma cells decreased the release of small EVs isolated at 100,000 × g in vitro (p = 0.005), but not the release of larger EVs, isolated at 10,000 × g. GL261.shRab27a cells were less viable compared to the scramble control in vitro (p < 0.005). A significant increase in CCL2 expression in shRab27a GL261 cells was also observed (p < 0.001). However, in vivo there was no difference in tumor growth or overall survival between the two groups, while shRab27a tumors showed lower proliferation at the tumor borders. Decreased infiltration of IBA1 positive macrophages and microglia, but not FoxP3 positive regulatory T cells was observed. Conclusion: Rab27a plays an important role in the release of small EVs from glioma cells, and also in their viability and expression of CCL2 in vitro. As interference in Rab27a expression influences glioma cell viability and expression profiles, future studies should be cautious in us

Background A phase I/II trial for glioblastoma with the oncolytic adenovirus Delta24-RGD was recently completed. Delta24-RGD conditionally replicates in cells with a disrupted retinoblastomapathway and enters cells via av beta 3/5 integrins. Glioblastomas are differentially sensitive to Delta24-RGD. HDAC inhibitors (HDACi) affect integrins and share common cell death pathways with Delta24-RGD. We studied the combination treatment effects of HDACi and Delta24-RGD in patient-derived glioblastoma stem-like cells (GSC), and we determined the most effective HDACi. Methods SAHA, Valproic Acid, Scriptaid, MS275 and LBH589 were combined with Delta24-RGD in fourteen distinct GSCs. Synergy was determined by Chou Talalay method. Viral infection and replication were assessed using luciferase and GFP encoding vectors and hexon-titration assays. Coxsackie adenovirus receptor and av beta 3 integrin levels were determined by flow cytometry. Oncolysis and mechanisms of cell death were studied by viability, caspase-3/7, LDH and LC3B/p62, phospho-p70S6K. Toxicity was studied on normal human astrocytes. MGMT promotor methylation status, TCGA classification, Rb-pathway and integrin gene expression levels were assessed as markers of responsiveness. Results Scriptaid and LBH589 acted synergistically with Delta24-RGD in approximately 50% of the GSCs. Both drugs moderately increased ava3 integrin levels and viral infection in responding but not in non-responding GSCs. LBH589 moderately increased late viral gene expression, however, virus titration revealed diminished viral progeny production by both HDACi, Scriptaid augmented caspase-3/7 activity, LC3B conversion, p62 and phosphop70S6K consumption, as well as LDH levels. LBH589 increased LDH and phosphop70S6K consumption. Responsiveness correlated with expression of various Rb-pathway genes and integrins. Combination treatments induced limited toxicity to human astrocytes. Conclusion LBH589 and Scriptaid combined with Delta24-RGD revealed s

Background: The survival of glioma patients with the current treatments is poor. Early clinical trails with replicating adenoviruses demonstrated the feasibility and safety of the use of adenoviruses as oncolytic agents. Antitumor efficacy has been moderate due to inefficient virus replication and spread. Previous studies have shown that truncation of the adenovirus i-leader open reading frame enhanced cytopathic activity of HAdV-5 in several tumor cell lines. Here we report the effect of an i-leader mutation on the cytopathic activity in glioma cell lines and in primary high-grade glioma cell cultures. Results: A mutation truncating the i-leader open reading frame was created in a molecular clone of replication-competent wild-type HAdV-5 by site-directed mutagenesis. We analyzed the cytopathic activity of this RL-07 mutant virus. A cell-viability assay showed increased cytopathic activity of the RL-07 mutant virus on U251 and SNB19 glioma cell lines. The plaque sizes of RL-07 on U251 monolayers were seven times larger than those of isogenic control viruses. Similarly, the cytopathic activity of the RL-07 viruses was strongly increased in six primary high-grade glioma cell cultures. In glioma cell lines the RL-07 virus was found to be released earlier into the culture medium. This was not due to enhanced viral protein synthesis, as was evident from equivalent E1A, Fiber and Adenovirus Death Protein amounts, nor to higher virus yields. Conclusion: The cytopathic activity of replicating adenovirus in glioblastoma cells is increased by truncating the i-leader open reading frame. Such mutations may help enhancing the antitumor cytopathic efficacy of oncolytic adenoviruses in the treatment of glioblastoma.