Like every tissue in our body, solid tumours need a blood supply to survive and grow. As the tumour grows, it releases chemical messages into the environment that cause new blood vessels to sprout from nearby existing ones. These new blood vessels are drawn towards the tumour where they feed the cancer cells and allow them to grow. Each time the cancer cells divide more mutations
build up in their genomes. Because different parts of the tumour acquire different
mutations, they behave differently. Sometimes one region of the tumour will grow faster
and more aggressively than others, causing the cancer to spread. All cells in the body, including cancer cells, must attach to the network of proteins that
surrounds them and this is done by proteins called integrins. Integrins tell the cell
about the type of environment they are in, and give the cell instructions about what
to do. In the case of cancer, particular integrins can send signals that tell the cancer cells
to invade the surrounding tissue. Sometimes the invading tumour cells may reach
a blood vessel, squeeze in, and enter the blood stream. The cancer cells take a bumpy journey to a distant part of the body. Sometimes they are able to squeeze out
of the blood vessel into healthy tissue, where they can start forming a secondary tumour.
This ability of cancer cells to invade and spread around the body is called metastasis,
and it represents the biggest challenge in treating cancer. Finding ways to stop cancer
spreading is a major focus of research at the Barts Cancer Institute.