How medicines work

Cancer is not a single disease – there are many types of cancers. What is more scientists are now discovering that cancers mutate and change over time – so the cancer an individual is diagnosed with is not the same as the cancer they many have two years later. Cancer can affect young people and old alike, but it is largely a disease of older people. So as people are living longer, the numbers of people affected by cancer are also increasing all the time.

Cancer cells reproduce without being affected by the normal mechanisms that control the cell cycle and limit their growth. Cancer cells:

• no longer need an external stimulus to divide
• are not sensitive to the normal signals that stop growth and division
• fail to undergo apoptosis (programmed cell death) in different ways such as producing proteins to protect them from apoptosis or inactivating the proteins involved in apoptosis
• may produce chemicals that stop the T-cells of the immune system from recognising them. This means cancer cells are not destroyed by the immune system
• invade healthy tissues by producing chemicals that dissolve protective proteins
• are capable of metastasis
• can stimulate the formation of new blood vessels to provide the resources they need to grow

In recent years our ability to sequence the human genome has increased dramatically. A process that took years can now be completed in days and costs thousands rather than millions of pounds.

Scientists are using these new techniques in many different ways to try and understand more about the causes of cancer and how it can most effectively be treated. For example:

• Studies of large groups of people such as the 100,000 Genomes project gives scientists the chance to compare the genomes of many people and identify genetic combinations that are linked to a rare disease or to an increased risk of different types of cancer. This helps them pinpoint exactly what changes result in the formation of the cancers. This in turn opens up the possibility of developing medicines specifically targeted to those changes in the cells.
• When an individual is diagnosed with cancer, the scientists are analysing the genome of both the individual affected and the cancer cells. They are repeating this genome analysis regularly – and finding that the cancer mutates and changes over time. This may explain why specific chemotherapy drugs work for a time, but then become ineffective. If the cancer has changed, it may need a change of drugs to treat it effectively.