Like any other cells in the body, tumour cells are influenced by blood vessels and the normal cells and molecules that surround and feed the tumour cells – the tumour microenvironment. In order to become established and to grow and spread, tumours need to develop specific capabilities: they must be able to move; remove obstructions to their growth and movement, such as the surrounding extracellular matrix; overcome the immune system and blood-borne cells of the immune system so that they can survive in blood vessels; and establish successfully in their new tissue environment.

In order to achieve these functions, tumours recruit host machinery and proteins involved in normal cell growth including transcription factors. The tumour microenvironment provides the signals that activate transcription factors. Therefore understanding how the tumour microenvironment affects cancer cell behaviour and how it contributes to a cancer cell’s response to ionising radiation is essential in understanding how to prevent the establishment, growth and progression of cancers and how to exploit the tumour microenvironment for therapeutic gain.