Scientists have developed a trimodal ultrasound technique to track glioblastoma tumors in awake mice, revealing how the deadly brain cancer physically remodels surrounding tissue. Researchers at Caltech and other institutions engineered tumor cells with bacterial gas vesicles, allowing non-invasive imaging of tumor growth, vascular changes, and neural activity.
Engineering Tumor Cells for Advanced Ultrasound Imaging
Studying malignant brain tumors in living subjects has long presented a major technical hurdle for researchers. Optical imaging provides fine detail but lacks the ability to penetrate deep into brain tissue, while standard magnetic resonance imaging struggles to capture brain function in awake, moving animals. To overcome these limitations, a research team led by chemical engineer Mikhail Shapiro of Caltech developed a specialized ultrasound technique published in iScience.
Making glioblastoma stand out in ultrasound scans required biological engineering. Certain bacteria naturally produce microscopic gas-filled bubbles known as gas vesicles. The researchers grew human glioblastoma cells and equipped them with the bacterial genes responsible for this effervescent trait. After testing the modified cells in a hydrogel phantom to verify visibility, the team implanted them directly into living brain tissue.
Tracking Tumor Progression and Vascular Remodeling in Mice
To watch the cancer establish its environment, the research team implanted the engineered human glioblastoma cells in the left thalamus of three mice. Over an 11-day observation window, the investigators used trimodal ultrasound repeatedly to monitor the tumors taking root and expanding.
- The first mode utilized the bacterial gas vesicles to render the tumor itself visible within the scan.
- The second mode monitored fluctuations in blood volume linked directly to local brain activity.
- The third mode deployed tiny bubbles injected into the bloodstream to map the surrounding vascular network in high detail.
Gliomas represent a particularly aggressive category of malignant growths originating from glial cells in the central nervous system. Glioblastoma stands as the most severe form, characterized by a stark 5-year survival rate of just 5 to 7 percent. Part of what makes these tumors so lethal is their tendency to tangle with healthy tissue, commandeering normal brain functions to sustain their own expansion.
Neural Activity and Cognitive Decline in Human Glioblastoma Patients
While the Caltech team monitored physical remodeling in mice, separate research led by neurosurgeon Shawn Hervey-Jumper and postdoctoral scholar Saritha Krishna at UC San Francisco investigated how glioblastoma affects human cognition in findings published in Nature. Scientists have established that brain tumors operate within a positive-feedback loop, producing substances that act as neurotransmitters. These chemicals hyperactivate nearby neurons, which in turn fuels further cancer cell growth.
To observe this dynamic in human behavior, the UCSF team worked with volunteers whose glioblastoma tumors had infiltrated the brain region responsible for speech control. Just before performing surgery, Hervey-Jumper placed a grid of micro-electrodes directly onto the surface of the speech cortex. Patients were shown pictures and asked to name them while the team recorded neural responses, comparing them against normal, non-tumor brain regions from the same individuals.
The data revealed that tumor-infiltrated areas recruited a much wider network of brain regions simply to identify everyday objects. This functional degradation mirrors an orchestra losing its synchrony.
“A brain tumor isn’t just sitting there dying. It’s being regulated by the nervous system. It’s having conversations with the cells around it and actively integrating into brain circuits, remodeling the way they behave.”
Shawn Hervey-Jumper, neurosurgeon at UC San Francisco, via Ucsf
Potential Treatment Avenues and the Role of Gabapentin
The discovery that tumors actively converse with neural circuits offers fresh targets for intervention.
Glioblastoma has historically resisted conventional cancer therapies, making the identification of hidden weaknesses a priority for neuro-oncology researchers.
Researchers note that understanding how these malignancies integrate into brain networks transforms the fundamental approach to studying and treating the disease.
“This study opens the door to a whole world of treatment possibilities for these patients and a new way of thinking about brain cancer.”
Shawn Hervey-Jumper, neurosurgeon at UC San Francisco, via Ucsf
By identifying these hidden weaknesses, researchers hope to develop more effective therapies that fundamentally change how neuro-oncologists approach the treatment of glioblastoma for their patients.