Preparing to move – how cancer can use your immune system as a highway
Dr Jacqui Shields and Dr Angela Riedel at the MRC Cancer Unit explain the science behind these brightly-coloured blobs that show us how cancer cells prepare their road ahead so they can spread around the body.
One of cancer’s deadliest features is its ability to move through your immune system’s ready-made network of vessels and nodes.
Often, we don’t know a cancer has spread through the immune system until it’s too late, but now we may have found something that could help us predict when that’s going to happen: our findings suggest that before cancer cells even begin to move, they emit signals which send the new area into chaos.
We were looking at the lymphatic system – a vital part of our immune system that connects a network of lymph nodes, like those shown in the picture above. Nodes contain different types of immune cells (shown here in red and green) and supporting structural cells (blue) that tell them where to be stored so that when disease strikes the immune cells are in the correct place to respond.
We wanted to know why these lymph nodes – which should be defending us against cancer – end up playing the perfect host to a dangerous enemy.
We made the two pictures above by taking images of thin slices of lymph nodes collected from mice and adding colour to show the different types of cells present. By creating these images, and conducting other analyses, we found that a cancer can send signals through the lymphatic system that interfere with how a node works. The images show a healthy lymph node (left) next to one that has been changed by the signals from a cancer (right).
The signals have altered the node’s structure and caused different immune cells to enter the node or go to the wrong places so they can’t respond properly. The signals also direct the structural cells of the node to stop producing chemicals that are essential for telling the immune cells where to go and keeping them alive. And they change the node’s shape, making it much larger.
Compared to the healthy node, it’s a mess. And it’s a mess that a cancer can exploit to switch off our defences.
If we could detect these changes early in the process of cancer spread – ‘metastasis’ – in people, we might be able to predict which cases are about to spread. But first of all we need to understand exactly how cancer cells create this effect. Then, we might just be able to stop cancer in its tracks.