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Scientists have identified a new genetic basis for breast cancer in a discovery that promises to change screening for the many cancers triggered by faulty genes.
They have found mutations in the DNA of four genes they believe play a small-yet-significant role in triggering breast cancer in women.
The discovery could lead to new methods of targeting younger women at higher-than-average risk of breast cancer so that they could be screened with mammography before hitting 50.
Unlike other genetic variations associated with familial breast cancer, the mutations in these four genes are relatively common in the general population and appear to form part of a much bigger community of genes that combine to play a role in breast-cancer predisposition.
However, the wider significance of the genetic discovery is that it brings the day closer when anyone's genome - the entire DNA blueprint - can be screened for the many hundreds of genes believed to increase susceptibility to a wide range of cancers.
Some scientists believe the latest studies, published online in the journals Nature and Nature Genetics, are among the most important in the field of breast cancer since the first susceptibility genes for inherited forms of the disease were identified in the mid-1990s.
"This set of scientific studies points to the future understanding of the genetics of cancer," said Professor Karol Sikora, a leading cancer specialist, who was not directly involved with the latest work.
"In theory, it allows you to look at thousands of people to study their genes and to find associations we didn't see before."
Several teams of scientists took part in the latest studies, with the biggest led by Douglas Easton, professor of cancer epidemiology at Cambridge University, who studied the DNA of nearly 50,000 women, half of whom had breast cancer.
The scientists used "DNA chips" to screen each person's genome for genetic variations that were found to be strongly linked with breast cancer. Small variations in four genes emerged as the most likely associations.
"We're excited by these results because the regions [of DNA] we identified don't contain previously known inherited cancer genes," Professor Easton said.
"This opens the door to new research directions. Only recent advances in technology have allowed us to carry out such a large comparison study."
The scientists are applying the same approach to other cancers, such as prostate, lung and bowel cancers, in the hope of identifying genetic changes that can trigger a higher risk of developing them.
Inherited forms of breast cancer that are known to run in families account for between 5 and 10 per cent of cases. These genes - called BRCA1 and BRCA2 - were the first to be identified in the mid-1990s.
Two of the four new genes are relatively common. For instance, between one in six and one in 16 women are estimated to carry two faulty copies of one of these genes. The three other genes identified are also common among the population but carry a lower risk of disease.
Professor Bruce Ponder, a study leader and director of Cancer Research UK's Cambridge research institute, said the technique had greatly accelerated the rate at which cancer genes could be found.
- INDEPENDENT
