Mutations in the BRCA1 breast cancer gene appear to be linked with the loss of a protein important for braking cell growth, scientists reported on Sunday.

The breakthrough could lead to more effective therapies for women with an aggressive and especially deadly cancer that does not respond to current advanced drugs.

Scientists have known for more than a decade that women with certain alterations in the BRCA1 gene were at high risk for breast cancer. What they have not understood is exactly how a mutation in this gene leads to cancer.

Researchers at Columbia University, working with at team at Sweden's Lund University, now believe mutations in the BRCA1 gene can leave cells incapable of repairing routine DNA damage. When such damage occurs in a protein called PTEN, which regulates the growth of cells, cell growth is unchecked and tumors form.

Women with faulty copies of BRCA1 or BRCA2 have a 50 to 85 percent chance of getting breast cancer. Mutations in these genes account for 5 to 10 percent of breast cancer cases.

(Agencies via Xinhua News Agency December 11, 2007)