New method reveals how brain cancer cells spread

By combining live imaging of brain tissue with artificial intelligence, researchers at Uppsala University have developed a method that reveals how individual glioblastoma cells spread through the brain, how they can switch between different ways of moving, and how they are affected by cancer treatments. An increased understanding of tumour cell invasion might in the long term contribute to more effective therapies.

Glioblastoma is one of the most aggressive forms of brain cancer. One reason it is so difficult to treat is that tumour cells spread into the surrounding healthy brain, beyond the area that can be removed by surgery. These remaining cells can contribute to the cancer returning after treatment.

In a study in the journal Nature Communications, researchers at Uppsala University present GlioTrace, a new method that can follow thousands of individual tumour cells as they move through brain tissue.

“Until now, we have mostly seen snapshots of how glioblastoma spreads. This method combines microscopy with artificial intelligence and allows us to watch the process unfold in living brain tissue. We could also compare tumours from different patients and investigate how they respond to treatment,” says Hitesh Mangukiya, researcher at the Department of Immunology, Genetics and Pathology at Uppsala University and one of the study’s lead authors.

Tumour cells change how they move

The researchers studied glioblastoma cells originating from six patients. The cells were grown as tumours in mouse brains, which were then cut into thin slices and kept alive in the laboratory. Using automated microscopy, the researchers photographed the slices at intervals of no more than two hours for up to five days.

A machine-learning system identified and followed individual tumour cells and the researchers used statistical models to calculate how cells switched between different states. The results revealed clear differences between tumours. Some spread predominantly along blood vessels, while others spread more diffusely through the brain tissue. Individual tumour cells also could change their shape and movement over time, and could even switch between moving along blood vessels and moving independently through the tissue.

“What surprised us most was how flexible the tumour cells are. The same cell can change how it moves over just a few days. To develop treatments that stop tumour cells from spreading, we need to understand this ability to switch between different behaviours,” says Madeleine Skeppås, PhD student at Uppsala University and co-lead author of the study.

Cancer treatments affect how tumour cells spread

The researchers also used GlioTrace to investigate how drugs affect tumour cell movement. Two drug substances reduced the movement and spread of tumour cells in the brain slices. However, the effects differed between the patient-derived tumours and between the different types of migrating cells.

The team also found that in some tumour models, a combination of radiation and chemotherapy increased the proportion of cells with a particular shape. These cells were among the fastest moving and occupied a central position in the network of transitions between cell states. These findings raise the possibility that this type of invasive cell may persist under treatment, but further research is needed to determine whether it is more treatment-resistant or contributes to tumour recurrence.

“Using this method allows us to monitor, for the first time, how thousands of individual tumour cells move through living brain tissue and to see how they adapt their behaviour in real time. It opens up new possibilities to understand and, in the long term, halt the invasion process,” says Sven Nelander, Professor of Integrative Cancer Research at Uppsala University.

A new tool for studying tumour invasion

A central part of GlioTrace is the computational analysis system developed by Madeleine Skeppås together with colleagues at Chalmers University of Technology and the University of Gothenburg. It processes the microscopy images, follows individual cells, identifies their different shapes and estimates how they change over time.

Unlike methods that only image small regions of the brain, GlioTrace can follow tumour cells across entire brain slices using standard microscopes. The analysis software is freely available to other researchers.

“We hope that the method will help us understand how tumour cells interact with their surroundings and identify treatments that can prevent cancer from spreading through the brain. However, for now, GlioTrace is a research method, and further studies are needed before it could be used to guide treatment decisions in patients,” says Hitesh Mangukiya.