Researchers developed a biomimetic nanovesicle that crosses the blood-brain barrier, degrades DNA repair proteins, and restores temozolomide sensitivity in glioblastoma.
(Nanowerk Spotlight) Glioblastoma is an aggressive and lethal brain tumor marked by poor prognosis and limited treatment options. Despite surgical resection followed by radiation and chemotherapy, most patients relapse within months. The median survival remains under two years. One of the central challenges in treating glioblastoma lies in its ability to resist chemotherapeutic agents. Temozolomide (TMZ), the only FDA-approved first-line drug for this disease, initially shows promise. It works by modifying DNA in tumor cells, triggering a form of damage they cannot easily repair.
However, glioblastoma adapts by activating internal repair systems. These systems—including enzymes like MGMT and pathways like homologous recombination (HR) and non-homologous end joining (NHEJ)—allow the tumor to fix the damage and keep growing. As a result, the treatment gradually loses its effect.
Attempts to overcome this resistance have focused on targeting specific DNA repair mechanisms. Some strategies aim to silence MGMT, while others attempt to interfere with regulatory pathways that enable repair. These efforts have shown limited success. A key reason is that glioblastoma does not rely on a single repair route. When one mechanism is blocked, others compensate. This redundancy makes resistance robust. A growing body of research has identified a protein called BRD4 as a central coordinator of these repair responses.
BRD4 is frequently elevated in glioblastoma tumors and is associated with worse outcomes. It promotes the expression of DNA repair proteins like Ku80, RAD51, and MGMT, all of which contribute to the tumor’s ability to survive TMZ treatment.
Inhibiting BRD4 has therefore emerged as a potential way to disable several repair systems at once. Some small-molecule drugs targeting BRD4 are under clinical investigation, but they face two key problems. First, they often require high doses, which can be toxic. Second, their effect is limited to temporarily blocking the protein’s activity rather than removing it entirely.
A newer class of molecules called PROTACs (proteolysis-targeting chimeras) offers a more powerful strategy. Instead of merely blocking BRD4, PROTACs tag it for destruction by the cell’s own protein-degrading machinery. This approach eliminates the protein altogether and can be effective at lower doses. Yet current PROTACs struggle with two major issues: their large size makes them difficult to deliver into cells, and they lack tumor selectivity. In the case of glioblastoma, they also face the additional hurdle of crossing the blood-brain barrier (BBB), which blocks most drugs from reaching brain tissue.
Researchers from South China University of Technology have now developed a delivery system that addresses these challenges. In a study published in Advanced Materials (“Biomimetic Hybrid PROTAC Nanovesicles Block Multiple DNA Repair Pathways to Overcome Temozolomide Resistance Against Orthotopic Glioblastoma”), the team reports a method for transporting a BRD4-targeting PROTAC directly into glioblastoma cells, bypassing the BBB and avoiding off-target effects. Their system combines a nanovesicle with tumor-derived membrane material to achieve both selective targeting and effective drug delivery.
These nanovesicles, called M@TP, carry two agents: temozolomide and a lipid-conjugated form of the BRD4 PROTAC, referred to as PC-ss-Pro. The outer layer of the vesicle is made from fragments of glioblastoma cell membranes, which enables the vesicle to recognize and bind to tumor cells through shared surface proteins. This homotypic targeting ensures that M@TP preferentially accumulates in glioblastoma tissue.
Schematic illustration of the design and mechanism of the biomimetic hybrid liposome system (M@TP) for targeting glioblastoma and overcoming TMZ resistance. a) Mechanism of glutathione (GSH)-mediated activation of the BRD4 PROTAC prodrug (PC-ss-Pro) and the fabrication of M@TP. b) Schematic illustration of M@TP reversing TMZ resistance by blocking multiple DNA repair pathways through BRD4 degradation. (click on image to enlarge)
The inner structure of the vesicle is engineered to respond to the tumor’s internal environment. Conditions inside glioblastoma cells are both acidic and rich in a reducing molecule called glutathione (GSH). The PC-ss-Pro is linked by a disulfide bond that is stable in normal tissues but breaks apart in the presence of GSH. This releases the active PROTAC molecule specifically within the tumor. Once released, the PROTAC binds to BRD4 and recruits an E3 ligase (VHL), triggering BRD4’s degradation. As BRD4 levels fall, the downstream DNA repair proteins it regulates—MGMT, Ku80, and RAD51—are also suppressed. This makes the tumor vulnerable to the DNA damage caused by TMZ, restoring its sensitivity to treatment.
The researchers confirmed these effects in laboratory experiments using glioblastoma cell lines. Cells resistant to TMZ showed elevated BRD4 levels. When treated with the PROTAC alone, these cells experienced a dose-dependent reduction in BRD4. Combining the PROTAC with TMZ lowered the amount of drug required to kill the cells and increased markers of DNA damage and apoptosis. These changes indicate a restored treatment response.
To improve the pharmacokinetics of the system, the team encapsulated both TMZ and PC-ss-Pro in lipid-based vesicles. These vesicles were then fused with membrane fragments from TMZ-resistant glioblastoma cells. The final product, M@TP, was stable in solution and capable of releasing its contents in response to tumor-like conditions. In cell culture, M@TP was taken up more efficiently by glioblastoma cells than vesicles without membrane coating. It also showed greater penetration into 3D tumor spheroids, which better simulate the structure of tumors in living tissue.
An artificial model of the blood-brain barrier was used to evaluate whether M@TP could reach the brain. M@TP crossed this barrier more effectively than uncoated vesicles and appeared to partially loosen the tight junctions between endothelial cells, which may enhance its penetration. When tested in mice with implanted glioblastoma tumors, M@TP accumulated in the tumor more than either free drugs or standard vesicles. It also stayed in circulation longer, giving it more time to reach the tumor. Measurements showed higher concentrations of both TMZ and PROTAC in brain tumors compared to other tissues.
The therapeutic impact was evaluated in mice with resistant glioblastoma tumors. Mice treated with M@TP showed slower tumor growth, longer survival, and fewer signs of toxicity than those treated with control formulations. The treatment reduced levels of BRD4 and key repair proteins in tumor tissue and increased markers of DNA damage. In a model of recurrent glioblastoma following surgery, combining TMZ with M@P (a vesicle carrying only the PROTAC) reduced tumor regrowth and extended survival. This suggests that even in the context of residual disease, BRD4 degradation can help prevent relapse.
The study also assessed how the therapy affects the tumor’s immune environment. Glioblastoma often suppresses immune activity, but treatment with TMZ and M@P increased the presence of immune cells that can attack the tumor. Specifically, there was a rise in CD8+ and CD4+ T cells in both tumor and spleen, along with more mature dendritic cells in lymph nodes.
The treatment also shifted macrophages away from an immune-suppressive profile and toward one associated with inflammation. Blood analysis showed higher levels of immune signaling molecules like TNF-α and IFN-γ. These findings suggest that in addition to disrupting DNA repair, BRD4 degradation may improve immune recognition of the tumor.
By combining drug delivery, protein degradation, and tumor-specific targeting in a single system, this work provides a method for overcoming several barriers in glioblastoma therapy. The design of M@TP allows it to cross the blood-brain barrier, seek out tumor cells, and release its payload under precise conditions. Once inside, it disables key repair mechanisms and makes resistant cells susceptible to chemotherapy again. The inclusion of the tumor membrane coating adds an extra layer of specificity, reducing the chance of affecting healthy brain tissue. The study demonstrates a coordinated approach that restores drug sensitivity, suppresses relapse, and potentially reactivates immune surveillance—all within a single therapeutic platform.
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