Diffuse midline glioma is a fast-growing brain tumour that mostly affects children. There are very few effective treatments, so we urgently need to understand how these tumours interact with the healthy cells around them.

This study looks at immune cells called myeloid cells. Some of these, called microglia, live in the brain all the time. Others travel in the blood and can be drawn into the brain when a tumour sends out certain signals. These blood-derived immune cells are called macrophages, and their normal job is to clear away debris and fight infection. Once inside the brain, however, these recruited macrophages may instead help the tumour survive, spread, and resist treatment.

Using brain tissue supplied by BRAIN UK, we will compare two major types of diffuse midline glioma with another childhood brain tumour and with healthy (non-cancerous) tissue. Using specialised staining techniques in the lab, we can tell apart microglia that belong in the brain from macrophages that have travelled in from the bloodstream. We’ll count these cells, map where they sit in the tissue, and see whether different tumour types attract different patterns of immune cells.

This will give us a clearer picture of how the immune environment differs across childhood brain tumours. The findings will help guide future research into the signals that draw macrophages in, and could point to ways of blocking the interactions that help tumours grow. In the longer term, this could help lead to more precisely targeted treatments for children facing these devastating cancers.