By Nana O 
Researchers at Washington University School of Medicine in St. Louis, in collaboration with scientists at Northwestern University, have unveiled a groundbreaking noninvasive treatment strategy for glioblastoma, one of the most formidable and lethal forms of brain cancer. This innovative approach leverages precisely engineered nanostructures, delivered via simple nasal drops, to carry potent anti-cancer compounds directly into the brain and stimulate the body’s own immune system to combat the tumor. In preclinical studies conducted on mice, this novel method demonstrated remarkable success in treating glioblastoma, offering a significant advancement over current treatment paradigms and avoiding the invasiveness of other emerging therapies. The pivotal findings of this research were published this month in the prestigious scientific journal Proceedings of the National Academy of Sciences (PNAS).
The Unyielding Challenge of Glioblastoma
Glioblastoma multiforme (GBM) is a devastating diagnosis, representing the most common and aggressive primary malignant brain tumor in adults. Originating from astrocytes, a type of glial cell that supports and nourishes neurons, GBM is characterized by its rapid growth, diffuse infiltration into healthy brain tissue, and an exceedingly poor prognosis. The median survival rate for patients diagnosed with glioblastoma, even with aggressive multimodal treatment including surgery, radiation, and chemotherapy, remains grim, often measured in months rather than years.
A primary impediment to effective glioblastoma treatment has historically been the formidable challenge of delivering therapeutic agents across the blood-brain barrier (BBB), a highly selective physiological barrier that protects the central nervous system from circulating toxins but also significantly restricts the passage of most drugs. This inherent difficulty has led to a constant search for novel drug delivery systems and treatment modalities that can overcome this biological hurdle.
Dr. Alexander H. Stegh, a professor and vice chair of research in the Taylor Family Department of Neurosurgery at WashU Medicine, and a co-corresponding author of the study, articulated the driving force behind this research. "We wanted to change this reality and develop a noninvasive treatment that activates the immune response to attack glioblastoma," he stated. "With this research, we’ve shown that precisely engineered nanostructures, called spherical nucleic acids, can safely and effectively activate powerful immune pathways within the brain. This redefines how cancer immunotherapy can be achieved in otherwise difficult-to-access tumors." Dr. Stegh also holds the crucial role of research director at The Brain Tumor Center at Siteman Cancer Center, a leading institution based at Barnes-Jewish Hospital and WashU Medicine.
Harnessing the Immune System: The STING Pathway
Glioblastoma is often described as a "cold tumor" by oncologists, a classification that signifies its remarkable ability to evade detection and destruction by the immune system. Unlike "hot tumors," which are characterized by a robust infiltration of immune cells and a heightened inflammatory response, glioblastoma tumors tend to create an immunosuppressive microenvironment, effectively shielding themselves from immune surveillance.
This lack of immune responsiveness has spurred significant research into strategies that can "warm up" these tumors, making them more susceptible to immunotherapy. One promising avenue of investigation focuses on activating a cellular signaling pathway known as STING, which stands for stimulator of interferon genes. The STING pathway plays a critical role in innate immunity, acting as a sensor for foreign or damaged DNA within cells. When activated, it triggers a cascade of inflammatory responses, including the production of interferons, which can alert and mobilize various immune cells to target and eliminate threats.
Previous studies had indicated that drugs capable of activating the STING pathway could prime the immune system to recognize and attack glioblastoma. However, a significant limitation of these existing STING agonists was their inherent instability, leading to rapid degradation in the body. Consequently, to achieve therapeutic concentrations at the tumor site, these drugs had to be administered directly into the brain through highly invasive surgical procedures. Given that multiple doses are often required for optimal efficacy, this approach presents substantial burdens and risks for patients already facing a life-threatening illness.
Akanksha Mahajan, PhD, a postdoctoral research associate in Dr. Stegh’s laboratory and the first author of the PNAS study, highlighted the motivation to develop a less burdensome treatment. "We really wanted to minimize patients having to go through that when they are already ill, and I thought that we could use the spherical nucleic acid platforms to deliver these drugs in a noninvasive way," she explained.
The Ingenuity of Nanostructures: Spherical Nucleic Acids
To overcome the limitations of previous STING-activating therapies, the research team sought a novel delivery system that was both effective and noninvasive. This led to a crucial collaboration with Dr. Chad A. Mirkin, PhD, director of the International Institute for Nanotechnology and a distinguished professor of Chemistry at Northwestern University. Dr. Mirkin is a pioneer in the field of nanotechnology and the inventor of spherical nucleic acids (SNAs).
SNAs are a class of nanoscale particles characterized by a dense shell of nucleic acid strands (DNA or RNA) surrounding a core material. This unique architecture confers several advantages over conventional drug delivery systems, including enhanced stability, improved cellular uptake, and potent biological activity. The dense arrangement of nucleic acids on the surface of the SNA allows for a high payload of therapeutic molecules and facilitates efficient interaction with cellular targets.
In this study, the combined research teams designed a specialized form of SNAs. These nanostructures featured a core of gold nanoparticles, which are biocompatible and have well-established properties for drug conjugation and imaging. The surface of these gold cores was densely decorated with short DNA fragments specifically engineered to activate the STING pathway within targeted immune cells. The choice of gold as a core material also offers potential advantages for imaging and tracking the nanostructures within the body.
A Novel Pathway: Nose-to-Brain Delivery
The innovative aspect of this research lies not only in the nanostructure design but also in the chosen route of administration. Recognizing the direct anatomical connection between the nasal passages and the brain, the researchers explored intranasal delivery as a means to bypass the blood-brain barrier and deliver the nanotherapeutic directly to the central nervous system. Intranasal delivery has been investigated for various brain-targeted therapies, but its application for activating immune responses against brain tumors using nanoscale therapeutics had not been previously demonstrated.
"This is the first time that it has been shown that we can increase immune cell activation in glioblastoma tumors when we deliver nanoscale therapeutics from the nose to the brain," Mahajan stated, underscoring the novelty and significance of their findings.
Visualizing the Journey: Tracking Nanodrops to the Brain
To validate their approach, the researchers meticulously tracked the fate of the nanodrops following intranasal administration in mice models of glioblastoma. A key component of their strategy involved incorporating a molecular tag into the spherical nucleic acids that emitted a fluorescent signal detectable under near-infrared light. This allowed for real-time visualization of the nanostructures’ distribution within the animal’s body.
Following intranasal administration, the researchers observed the fluorescently tagged nanodrops traveling along the olfactory nerve pathway, a direct route connecting the nasal cavity to the olfactory bulb in the brain. This confirmed the intended nose-to-brain transport. Crucially, the immune response triggered by the nanomedicine was found to be concentrated within specific immune cells residing in and around the glioblastoma tumors. Some level of immune activation was also detected in nearby lymph nodes, suggesting a systemic priming of the immune system.
An important finding was the limited spread of the therapy throughout the rest of the body. This localized distribution is highly desirable, as it minimizes the potential for off-target effects and systemic toxicity, thereby enhancing the overall safety profile of the treatment. Further histological examinations confirmed that immune cells within the tumor microenvironment had indeed activated the STING pathway, equipping them with the enhanced capacity to recognize and mount a more potent attack against the cancer cells.
Synergistic Treatment: Eradicating Tumors and Preventing Recurrence
The therapeutic potential of this nanotherapy was further amplified when it was combined with other immunomodulatory agents. Specifically, when the STING-activating nanostructures were administered in conjunction with drugs designed to activate T lymphocytes—a critical type of immune cell involved in adaptive immunity—the results were exceptionally promising. This dual-action, two-dose treatment regimen was able to not only eliminate established glioblastoma tumors in the mouse models but also establish a long-lasting immune memory, effectively preventing the cancer from recurring. These outcomes represented a substantial improvement over the efficacy observed with current STING-targeting therapies.
Despite these encouraging results, Dr. Stegh cautioned that activating the STING pathway alone may not be sufficient to achieve a complete cure for glioblastoma. He explained that glioblastoma tumors are adept at employing multiple sophisticated mechanisms to suppress or evade immune responses. To address this, his research group is actively exploring strategies to incorporate additional immune-stimulating functionalities directly into their nanostructure designs. This could pave the way for single-treatment modalities capable of simultaneously targeting multiple immunosuppressive pathways within the tumor microenvironment.
"This is an approach that offers hope for safer, more effective treatments for glioblastoma and potentially other immune treatment-resistant cancers, and it marks a critical step toward clinical application," Dr. Stegh concluded, expressing optimism about the future translational potential of this work.
Funding and Disclosure
This pioneering research was made possible through substantial funding from various prestigious sources, underscoring the national and international significance of this endeavor. Key financial support was provided by the National Cancer Institute (NCI) of the National Institutes of Health (NIH) through grant numbers P50CA221747 and R01CA275430. Additional support from the NIH was provided via grants R01CA120813, R01NS120547, and R01CA272639. Further contributions came from the Melanoma Research Foundation, the Chicago Cancer Baseball Charities at the Lurie Cancer Center of Northwestern University, and grants from industry partners Cellularity, Alnylam, and AbbVie. The sophisticated imaging capabilities at Siteman Cancer Center’s Small Animal Cancer Imaging core were supported by NIH instrumentation grants S10OD027042 and S10OD025264, as well as the NCI Cancer Center grant P30CA091842. PET and MRI imaging services were funded by the Robert H. Lurie Comprehensive Cancer Center Grant P30CA060553. The content of this publication is solely the responsibility of the authors and does not necessarily reflect the official views of the NIH.
The researchers have also disclosed potential competing interests. Dr. Alexander Stegh is a shareholder in Exicure Inc., a company actively developing SNA therapeutic platforms. Dr. Chad Mirkin is a shareholder in Flashpoint, a company focused on developing SNA-based therapeutics. Both Dr. Stegh and Dr. Mirkin are listed as co-inventors on patent US20150031745A1, which details the use of SNA nanoconjugates for crossing the blood-brain barrier. These disclosures are standard practice in scientific publishing and aim to ensure transparency regarding any potential conflicts of interest.
Broader Implications and Future Directions
The implications of this research extend beyond glioblastoma. The ability to noninvasively deliver potent immunomodulatory agents directly to the brain via nasal drops could revolutionize the treatment of a wide range of neurological disorders and brain cancers that have historically been refractory to therapeutic intervention. The success of the SNA platform in targeting the STING pathway and activating immune responses opens doors for developing similar nanotherapeutic strategies for other "cold" tumors, both within and outside the central nervous system.
The combination therapy demonstrated in the study—STING activation coupled with T-cell stimulation—represents a promising blueprint for overcoming tumor-induced immune suppression. Future research will likely focus on refining the nanostructure design to incorporate multiple therapeutic payloads, enabling a more comprehensive attack on the multifaceted defenses employed by aggressive cancers. Furthermore, the development of more sophisticated tracking and imaging techniques will be crucial for optimizing dosing and monitoring treatment response in preclinical and, eventually, clinical settings.
This breakthrough marks a significant stride toward translating cutting-edge nanotechnology and immunology into tangible, patient-centered therapies, offering a renewed sense of optimism for individuals facing the devastating prognosis of glioblastoma and other challenging cancers. The journey from laboratory discovery to clinical application is often long and complex, but the innovative approach developed by the Washington University and Northwestern University teams represents a critical and hopeful step forward.