Rare genetic condition sheds light on body's cancer defences
A rare inherited condition has brought scientists a step closer to understanding how cells safeguard themselves from becoming cancerous.
People with Bloom's syndrome - which is caused by inheriting faulty versions of a gene called BLM - are highly prone to developing cancer and must be monitored for the disease from a young age.
Although scientists knew the BLM gene played a role in stopping normal cells from becoming cancerous, it was not known how.
But in tomorrow's edition of Nature1, Cancer Research UK scientists report that BLM stops a DNA repair process in cells from introducing errors that could cause cancer.
Cells are equipped with a number of repair kits for their DNA when it gets damaged, to protect them from cancer. But the repair process isn't perfect and can lead to errors - some of which may lead to cancerous growth.
Researchers at the Cancer Research UK Oxford Cancer Centre found that the BLM gene is key to keeping one of these DNA repair processes under control. In people with Bloom's syndrome - who have no normal copy of BLM - errors creep into their DNA through this repair process, giving them their susceptibility to cancer.
Cancer Research UK's Professor Ian Hickson, who led the team of researchers, says: "Bloom's is a very rare condition that causes cancer to develop far earlier in life than normal. The disease has been of special interest to cancer scientists for many years for the insights it could yield into the biology of cancer.
"People with Bloom's syndrome have no working copy of the BLM gene. We have managed to unravel why that gene is so important to preventing cancer.
"It stops one of the cell's own DNA repair processes from causing potentially dangerous errors. Without BLM, the cell's repair machinery becomes its own worst enemy."
BLM works as part of a repair process called homologous recombination. Chromosomes wrap around each other in order to exchange lost information, and BLM helps them unwrap. When BLM does not function, the chromosomes do not unwrap properly and errors occur.
Professor Robert Souhami, Cancer Research UK's Director of Clinical and External Affairs, says: "Studies into rare inherited conditions such as Bloom's syndrome can give us unique insight into cancer in all its forms. This study offers us an intriguing understanding of one of the fundamental processes involved at the very beginning of a cancer's development.
"The more we understand about the steps leading to cancer, the closer we will be to modifying those processes to stop the disease in its early stages."
- Nature426 pp.870-874
Notes to Editor
Bloom's syndrome is a genetic disease caused by inheriting two faulty copies of the BLM gene.
Patients with Bloom's syndrome show a range of symptoms, including a small body size, sun-sensitive facial reddening, infertility, immunodeficiency and a strong predisposition to the full range of human cancers.
The mutation responsible for causing Bloom's syndrome is most common among Ashkenazi Jews. The syndrome appears in around 2 of every 100,000 newborn Ashkenazi Jews, and is much less common in other populations.