A long and fateful journey
Blog posted by: Martin Christlieb
What could be worse than cancer? Cancer that has spread. The average survival across all cancer types is about 50%. Most of the failures will occur in people whose tumours have spread (metastasised).
How does a tumour spread? If we knew the answer to that we would have another set of opportunities to fight back.
A tumour is composed of millions of cells that compete with each other for space and resources. As the tumour grows the competition intensifies until one or more cells discover how to move. These cells are now at an advantage; they can move away from the crowded tumour towards richer and less competitive environments.
How does a cell learn to move? The answer lies in our DNA. At various points in our lives our cells need to move to build or repair us. Just because most of our healthy cells don’t move doesn’t mean the template for doing it is lost; just suppressed.
Moving is a complex business. The tumour cell must detach itself from its neighbours. As it moves it must slide or cut its way through a network of proteins designed to hold cells together in the correct shape for our bodies.
Our travelling tumour cell is small; twenty of them would fit side-by-side into a millimetre, so it may have a long journey to undertake. Despite the distances, the cell may eventually meet a blood vessel, which is made of cells bound together into a tube. Our tumour cell must cut the bonds between vessel cells and squeeze inside.
Once inside the blood vessel, the cell is swept away by blood flowing at up to a metre a second. Blood flows fast in large arteries, but slows down in smaller vessels (capillaries). In a capillary our tumour cell may be moving slowly enough to attach to the wall then once attached, the process of cutting the bonds between vessel cells and squeezing out can begin.
Our tumour cell has now arrived in a new part of the body, but the job is not yet done. In order to establish a new colony of cells (a metastasis) the cell must remake the local environment; a small nest to multiply in.
If we understood each step of this journey we would be in a much better position to make a difference to exactly that group of patients who we currently can’t help.