Summary: Researchers have pinpointed a small molecule, miR-181d, that controls a key source of variability inside glioblastoma tumors. Delivering miR-181d into tumors reduced differences between individual cancer cells and made the tumors more responsive to standard chemotherapy.
Source: Brown University Health
Key Facts:
- The challenge: Glioblastoma tumors contain highly heterogeneous cells, so some cells survive therapy while others die, enabling tumor persistence and recurrence.
- The mechanism: MGMT, a DNA-repair enzyme, repairs chemotherapy-induced damage. Its expression varies greatly between cells inside the same tumor.
- The regulator: The microRNA miR-181d acts as a master regulator of MGMT production at the single-cell level.
- The therapeutic approach: Restoring or maintaining miR-181d levels in tumors reduces cell-to-cell variability and increases sensitivity to chemotherapy such as temozolomide.
A study from Brown University Health, published November 10 in Cell Reports, reveals a molecular explanation for why glioblastoma often resists chemotherapy and describes a potential strategy to counteract that resistance. The researchers focused on differences between individual tumor cells rather than on average tumor behavior, and their findings point to a new way to improve treatment outcomes for this aggressive adult brain cancer.
Glioblastoma is difficult to cure in part because cells within a single tumor can behave very differently. These intratumoral differences allow some cells to withstand chemotherapy while others are eliminated, leaving resistant cells to repopulate the tumor. For years investigators have documented this heterogeneity, but the molecular drivers and therapeutic implications of such variability have been less clear.
The team led by senior author Clark Chen, MD, PhD, professor and director of the brain tumor program in the department of neurosurgery at Brown University Health, discovered that miR-181d is a key switch that controls how much of the DNA-repair enzyme MGMT each glioblastoma cell produces. MGMT (methyl-guanine methyl transferase) counters the DNA damage caused by alkylating chemotherapy and therefore enables cancer cells to survive treatment. Because MGMT expression varies widely between cells, some cells repair chemotherapy damage efficiently and persist, driving treatment failure.
The researchers found that treatment with the standard chemotherapy drug temozolomide triggers a cascade that reduces miR-181d levels inside tumor cells. That reduction is linked to increased activity of PNPT1 and requires ATR kinase activation, leading to accelerated degradation of miR-181d. As miR-181d levels fall, the variability of MGMT expression across the cell population increases, producing a wider range of responses to chemotherapy and a greater chance that resistant cells survive. Conversely, introducing miR-181d back into tumor cells suppressed this variability and improved chemotherapy sensitivity in experimental models.
“Instead of looking only at the average tumor response, we examined differences between individual cells within the same tumor,” said Clark Chen. “That shift in perspective revealed a regulatory mechanism that governs transcriptional variability of a clinically important DNA-repair enzyme.”
Gatikrushna Singh, assistant professor of neurosurgery at the University of Minnesota and a key collaborator on the study, emphasized the clinical potential: “This work explains why tumors maintain such internal diversity and supports gene-therapy or microRNA-delivery strategies that could meaningfully improve outcomes for many glioblastoma patients.”
Building on these findings, the research team has begun developing a therapy concept aimed at stabilizing miR-181d levels within tumors to reduce heterogeneity and make chemotherapy more uniformly effective. While further research and clinical testing will be needed, the study establishes a clear biological rationale for miRNA-based approaches to sensitize glioblastoma to existing treatments.
Editorial Notes
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full by editorial staff.
- Additional context and clarifications were added by the editorial team.
About this Glioblastoma Research Article:
- Author: Jessica Wharton
- Source: Brown University Health
- Contact: Jessica Wharton – Brown University Health
- Image: Image credited to Neuroscience News
Original Research: “Single-cell heterogeneity of MGMT expression is regulated by miR-181d in glioblastoma” by Clark Chen et al., Cell Reports. DOI: 10.1016/j.celrep.2025.116516
This collaborative study involved researchers from Brown University Health, the University of Minnesota, VisiCELL Medical Inc., Stanford University, and Johns Hopkins University. Co-authors include Gatikrushna Singh, Shilpi Singh, Iteeshree Mohapatra, Stefan Kim, Mayur Sharma (University of Minnesota); Johnny Akers (VisiCELL Medical Inc.); Thien Nguyen (Stanford University); Efrosini Kokkoli (Johns Hopkins University); and multiple colleagues at Brown University Health.
In brief, the work demonstrates that microRNA-dependent control of MGMT expression contributes to intratumoral heterogeneity and acquired resistance to temozolomide. By preventing miR-181d loss or supplementing miR-181d, the variance in MGMT expression can be reduced, suppressing one pathway to chemotherapy resistance. These findings support further exploration of targeted miRNA delivery as a complementary strategy to enhance the effectiveness of current glioblastoma treatments.