Glioblastoma is the most common and lethal form of primary brain cancer in adults. Despite surgery, radiation and chemotherapy, patients typically survive only around 14 months after diagnosis, and fewer than 5% live five years, according to figures cited in Molecular Therapy Oncology. That grim outlook has pushed researchers toward experimental approaches, including oncolytic viruses, which are engineered or naturally occurring viruses that infect and destroy cancer cells while sparing healthy tissue.
The treatment has shown promise in laboratory and early clinical settings, but complete remissions in patients remain rare. A new preprint posted on bioRxiv, titled ‘Unravelling resistance mechanisms of oncolytic viruses in glioblastoma,’ set out to understand why some tumours evade the therapy.
What the researchers did
According to the preprint’s abstract, the research team took 14 glioblastoma cell lines derived directly from patient tumours and exposed them to six different oncolytic viruses. This process generated virus-resistant tumour subpopulations, which the researchers could then study to identify what allowed those cells to survive.
The stated goal was to find new markers of resistance beyond the interferon-mediated antiviral response, a well-known cellular defence system that many viruses, including oncolytic ones, must overcome to be effective. Because the study has only been released as a preprint, it has not yet been peer-reviewed, and the full results beyond the abstract could not be independently verified.
A pattern seen elsewhere
A related, peer-reviewed study published in Molecular Therapy Oncology used a comparable panel of 14 patient-derived glioblastoma cell lines, testing them against 15 clinically relevant oncolytic viruses. That research found two distinct clusters of viruses with opposing patterns of tumour-killing activity, linked to different molecular subtypes of glioblastoma. Activity correlated with gene-expression patterns tied to interferon signalling, brain cell development, and the extracellular matrix, the structural scaffolding surrounding cells.
That finding points to intratumoral heterogeneity, the tendency of a single tumour to contain genetically distinct subpopulations of cells, as a key reason why oncolytic virus therapy can fail even when it initially appears to work. A treatment that kills most of a tumour can still leave behind resistant subclones that regrow.
Intratumoral heterogeneity in GBM is cited as a driver of therapeutic escape and the emergence of OV-resistant tumour subclones, according to the research brief compiled from the preprint and related literature.
Other resistance clues
Separate, previously published research offers additional pieces of the puzzle. A 2021 study found that a protein called CCN1, present in the tumour’s surrounding microenvironment, is associated with resistance to herpes simplex virus type 1, a virus commonly used as a base for oncolytic therapies. More recently, in 2025, researchers reported that inhibiting a protein called BRD9 could help overcome resistance to oncolytic virus treatment in glioblastoma, published in Cell Reports Medicine.
Taken together, these studies suggest that glioblastoma’s resistance to oncolytic viruses is not driven by a single mechanism but by multiple, overlapping factors tied to tumour genetics and its surrounding environment. The new bioRxiv preprint adds to that growing body of work, though its specific findings will need to be confirmed once the full paper undergoes peer review.
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