Scientists have pinpointed a new target in the battle against cancer. They believe that stem cells - the precursors of normal skin, blood and other types of tissue in the body - frequently play a crucial role in the spread of tumours.
Cancer Research UK (CRUK), Britain's biggest cancer charity, has set up a consortium of research groups to develop drugs that could deactivate affected stem cells. Such medicines would stop these cells from dividing to create new tumours.
Researchers involved in the project said last week that they hoped to highlight new drugs within two years. Clinical trials could begin using the most promising of these. Cancers of the skin and blood are considered to be prime targets for the new medicines.
"Stem cells are responsible for renewing tissue in the body," said Dr Clive Stanway, chief officer of Cancer Research Technology, the charity's commercial arm. "But sometimes they are subverted by cancerous processes. You can give a cancer patient radiotherapy or cut out their tumour surgically - but you can still leave a few affected stem cells behind. The person appears cured. Then the stem cells start dividing again and the tumour reappears."
Stem cells come in two varieties: embryonic stem cells, created at conception, from which all cells in the body are ultimately derived; and adult stem cells, which lie dormant until switched on when new tissue is needed. The new campaign will be concerned only with adult stem cells.
Professor Fiona Watt, deputy director of the CRUK's Cambridge Research Institute, said: "Essentially, these drugs would tell these cells to stop growing and multiplying."
Drugs are being tested by CRUK researchers to find those that are best able to switch off cell division and the spread of cancer.