USE OF ONCOLYTIC VIRUSES TO TREAT GLIOBLASTOMA RELAPSES THROUGH EXPERIMENTAL AND COMPUTATIONAL APPROACHES

Abstract Background: Glioblastoma (GBM) is an aggressive, therapy-resistant brain tumor with limited treatment options and poor prognosis. Oncolytic viruses (OVs), including those in the Measles–Mumps–Rubella (MMR) vaccine and herpes simplex virus (HSV), have shown promise in targeting GBM due to their selective cytotoxicity toward cancer cells. This study explores the anti-cancer efficacy of the MMR vaccine against GBM and investigates the role of CD46—a receptor for various OVs and a complement regulatory protein—as a potential prognostic biomarker and therapeutic modulator during HSV-based virotherapy. Methods: GBM cell lines, primary GBM cells, and normal murine microglial cells were treated with the MMR vaccine to evaluate cell viability, cell cycle progression, and intracellular viral load using RT-PCR and Transmission Electron Microscopy (TEM). Additionally, RNA-sequencing data from GBM patient samples (GDC Data Portal) were analyzed to quantify CD46 expression and assess its correlation with clinical outcomes. Transcriptomic data from HSV-treated GBM samples (GSE288846) were further assessed using differential expression analysis, gene set enrichment analysis (GSEA), functional network enrichment, and xCell immune deconvolution. Results: MMR treatment significantly reduced the viability of GBM cell lines and primary cells within 72 hours, with minimal impact on normal microglial cells. Cell cycle analysis indicated cytopathic effects primarily mediated by measles and mumps viruses, while rubella induced cell cycle arrest. RT-PCR showed higher intracellular viral loads in GBM cells than in normal cells, confirming selective viral sensitivity. CD46 expression was found to be heterogenous across GBM samples but elevated in patients with poor survival outcomes and high infiltration of immunosuppressive immune cells. HSV-based virotherapy downregulated CD46 expression, concurrently activating antiviral and interferon pathways, suggesting a shift toward a more immunogenic tumor microenvironment. Conclusions: The MMR vaccine demonstrates strong oncolytic activity against GBM cells with minimal toxicity to normal cells, supporting its therapeutic potential. Simultaneously, CD46 emerges as a dual-function biomarker and modulator of virotherapy efficacy. Its partial downregulation under HSV treatment underscores its relevance as both an entry receptor and a target to enhance oncolytic virus-based strategies for GBM treatment and relapse prevention.