Blocking a Mitochondrial Fission Protein Could Strip Head and Neck Cancers of Radiation Resistance

Radiation therapy remains a cornerstone of treatment for head and neck squamous cell carcinoma, one of the most common and difficult-to-treat malignancies worldwide, yet many tumors stubbornly survive the barrage of DNA-damaging radiation aimed at them. A new study published in the Journal of Translational Medicine points to an unexpected accomplice in this resistance: the constant remodeling of mitochondria, the cellular power plants that do far more than generate energy. Researchers led by Yannan Zheng, Tingting Li, and Yifei Li of Southern Medical University report that a protein called dynamin-related protein 1, or DRP1, which governs the splitting of mitochondria into smaller fragments, becomes elevated in cancer cells that have learned to shrug off radiation. When the team disabled DRP1, either genetically or with drugs, previously resistant tumors became dramatically more vulnerable to radiation, both in laboratory dishes and in living mice. The findings offer a preclinical blueprint for a strategy that could one day make radiation work better for patients whose cancers currently evade it.

The investigation began with a straightforward question: what molecular differences separate cancer cells that die under radiation from those that persist? To find out, the researchers performed RNA sequencing transcriptomic profiling, comparing parental head and neck squamous cell carcinoma cell lines with sublines that had been made radioresistant through repeated exposure. Among the genes that stood out as strongly upregulated in the resistant cells was DRP1, the master regulator of mitochondrial fission. Mitochondria are dynamic organelles that continuously divide and fuse, and this flux, sometimes described as mitochondrial plasticity, allows cells to adapt their energy metabolism to stress. In radioresistant cancer cells, that adaptability appears to depend heavily on DRP1-driven fission, which keeps mitochondria fragmented and metabolically flexible in the face of radiation-induced injury.

The clinical relevance of this observation was reinforced by two independent lines of evidence. In publicly available head and neck cancer datasets, patients whose tumors expressed higher levels of DRP1 had poorer overall survival. The team then validated the finding in an exploratory institutional cohort of patients treated with postoperative adjuvant or definitive radical radiotherapy, where elevated DRP1 again tracked with adverse radiotherapy-related outcomes. While these associations are correlational and require confirmation in larger prospective studies, they suggested that DRP1 is not merely a laboratory curiosity but a marker linked to how real patients fare under radiation treatment.

Mechanistically, the study revealed a striking chain of events that connects mitochondrial shape to radiation sensitivity. Radiation kills cells largely by generating reactive oxygen species, highly reactive molecules that shred DNA beyond repair. The researchers found that when DRP1 was knocked down in cancer cells, mitochondria underwent hyperfusion, fusing into elongated networks instead of fragmenting. This shift triggered a dramatic surge in radiation-induced reactive oxygen species, overwhelming the cell’s antioxidant defenses and leaving behind substantially more residual DNA damage after irradiation. In other words, fragmented mitochondria appear to act as a buffer that helps cancer cells absorb and neutralize the oxidative blast of radiation; remove that buffer, and the oxidative assault lands with full force.

To confirm that oxidative stress was truly the engine of this radiosensitization, the researchers added N-acetyl-L-cysteine, a well-known antioxidant precursor of glutathione, to the experiments. The antioxidant attenuated the radiosensitizing effect of DRP1 loss, supporting the interpretation that the excess reactive oxygen species generated in DRP1-depleted cells is what drives them toward death after radiation. Untargeted metabolomics then mapped the broader metabolic consequences of DRP1 depletion, revealing changes in metabolite abundance and pathway enrichment related to amino acid metabolism, glutathione synthesis, and bioenergetic homeostasis. Together, these data sketch a coherent picture: DRP1 maintains the metabolic and antioxidant machinery that radioresistant cells rely on, and dismantling that machinery leaves tumors exposed.

Crucially, the team showed that the phenomenon is not confined to genetic manipulation. Two pharmacological inhibitors, Mdivi-1, a widely studied fission blocker, and P110, a more selective peptide inhibitor that targets the interaction between DRP1 and its mitochondrial receptor, reproduced the key phenotypes of DRP1 knockdown in vitro. Clonogenic survival assays, which measure a cell’s ability to divide and form colonies after radiation, showed reduced survival when the inhibitors were combined with radiation. Radiation-induced DNA damage accumulated to a greater extent, and mitochondrial metabolism shifted in ways consistent with the loss of fission-dependent plasticity. The fact that two chemically distinct inhibitors produced matching results strengthens the case that DRP1 itself, rather than an off-target effect, underlies the radiosensitization.

The most compelling evidence came from animal models. In mice bearing subcutaneous xenografts derived from CAL27 IR-R, a head and neck cancer subline engineered through acquired radioresistance, adding Mdivi-1 to radiotherapy enhanced the antitumor effect compared with radiation alone. The researchers then turned to a complementary and arguably more clinically faithful model: a syngeneic orthotopic MOC-1 tongue tumor model, in which immunocompetent mice carry tumors in the tongue itself, mimicking the anatomical and immune context of human head and neck cancer. Once again, the combination of Mdivi-1 and radiation outperformed radiation alone. Histological examination of major organs at the study endpoint revealed no overt evidence of treatment-related injury, an early but encouraging signal regarding tolerability.

The concept of targeting mitochondrial dynamics in cancer is part of a broader shift in oncology research away from attacking tumors solely through their genomes and toward exploiting their metabolic vulnerabilities. Radiation oncology has long sought reliable radiosensitizers, agents that can be given alongside radiation to tip the balance from survival to death in tumor cells while sparing normal tissue. Many candidates have faltered in translation, often because their mechanisms are too narrow or their toxicity windows too slim. A fission inhibitor offers a different logic: rather than adding damage, it removes a defense, preventing cancer cells from flexibly reconfiguring their mitochondria to detoxify the reactive oxygen species that radiation generates. Because the strategy was effective in both an acquired-resistance model and an immunocompetent orthotopic model, it addresses two of the most common reasons preclinical radiosensitizers fail clinically.

Important caveats remain before this approach reaches patients. The clinical cohort linking DRP1 to outcomes was exploratory, and the safety findings in mice, while reassuring, represent only an initial assessment at a single study endpoint. Mdivi-1 itself has off-target effects described in the broader literature, which is why the confirmation with the more selective P110 peptide matters, and clinical-grade DRP1 inhibitors would need careful development. Dosing, scheduling relative to radiation fractions, and potential effects on normal tissues that depend on mitochondrial remodeling all require further study. Still, the internal consistency of the work, from transcriptomics through metabolomics, mechanistic cell biology, pharmacology, and two independent in vivo models, gives the hypothesis unusual robustness at the preclinical stage.

If subsequent studies confirm these results, DRP1 could join a growing list of metabolic regulators whose inhibition converts resistant tumors into treatable ones. For patients with head and neck squamous cell carcinoma, where radioresistance is a primary cause of treatment failure and options after recurrence are limited, a drug that strips away mitochondrial plasticity could meaningfully expand the therapeutic window of radiation. The study, funded by the National Natural Science Foundation of China and regional research programs in Guangdong, was conducted under institutional ethical approval for both animal experiments and patient tissue use. Its authors describe the findings as a preclinical rationale for further investigation of DRP1-targeted radiosensitization strategies, and the field will now watch to see whether this mitochondrial vulnerability can be translated into a clinical advantage.

Subject of Research: DRP1-mediated mitochondrial fission as a driver of radioresistance in head and neck squamous cell carcinoma

Article Title: Targeting DRP1 to limit mitochondrial plasticity overcomes radiation resistance in head and neck squamous cell carcinoma

Article References: Targeting DRP1 to limit mitochondrial plasticity overcomes radiation resistance in head and neck squamous cell carcinoma. (n.d.). https://doi.org/10.1186/s12967-026-09083-0

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09083-0

Keywords: head and neck squamous cell carcinoma, radioresistance, DRP1, mitochondrial fission, mitochondrial dynamics, reactive oxygen species, oxidative stress, DNA damage, radiosensitization, Mdivi-1, P110, metabolomics