British scientists hope that their discovery of a second gene for breast cancer, announced yesterday, may lead to treatments for the disease which kills 16,000 women a year in the UK.
The team, funded by the Cancer Research Campaign, won a three-way international race to find the gene, codenamed BRCA2.
Few cases of breast cancer are inherited; about 95 per cent appear to be "sporadic". But by analysing genetic differences in the cases which do run in families, researchers hope to cast light on non- inherited cases.
Although the newly-discovered gene is extremely rare, and thought to cause only 2 per cent of all breast cancer cases, researchers think that it may play a key role in allowing the disease to progress.
By understanding how it works, they might be able to develop treatments for any form of breast cancer.
They discounted the suggestion their work might lead to people choosing abortions based on genetic testing of foetuses, if they were carrying the gene. "Some women in families with this gene decide that they don't want to be tested to see if they have it," said Mike Stratton, who led the team at the Institute of Cancer Research. "Pre-natal tests would need very careful consideration."
The first breast cancer gene, BRCA1, was discovered by an American team at Utah University in 1994 after four years work. The same team, and another in Texas, were also trying to pinpoint the second gene.
BRCA1 and BRCA2 were tracked down by analysing genes from families with a history of breast cancer in female relatives. BRCA2 is particularly associated with early onset of the disease - one woman in the sample developed breast cancer at 19 - and only with breast cancer. BRCA1 is also associated with an inherited tendency to get ovarian, prostate and colon cancer.
While BRCA1 accounts for almost half the 1,000-plus known breast cancer families in the UK, BRCA2 is likely to be responsible for a third. It is also thought to play a key role in breast cancer in men in these families: 100 men die of the disease in the UK annually.
BRCA2's importance has led researchers to think it plays a key role in the development of breast cancer. "The BRCA2 gene has a fault which means that the protein it makes lacks function. It's like the brakes on a car not working," said Mike Stratton, of the Institute of Cancer Research, who led the team tracking down the gene. "That may mean it cannot stop cells replicating, allowing them to form a tumour."
The team now wants to try to find out what role the protein made by the gene plays. "By finding that, we may be able to find the drug strategies that will allow us to treat the cancer," said Dr Stratton.
However, screening everybody for the gene would be virtually impossible, he said.
The Cancer Research Campaign has filed a preliminary patent covering its research on the gene. Diagnostic tests for BRCA1 must pay royalties to Myriad Genetics, a company set up by the American scientists who discovered and patented it.Reuse content