Scientists are homing in on four new genes they believe are linked to breast cancer.

Tumours with multiple copies of the genes seem to be more aggressive, according to researchers who also report that the group is not found in healthy tissue.

Only a few possible cancer-causing genes have so far been identified, although a small number of women are at high risk because of faulty inherited BRCA1 and BRCA2 genes.

Cancer Research UK scientists at Cambridge University, who reported their latest findings in the journal Oncogene, studied 53 tumours and breast cancer cells grown in the laboratory, and concentrated on a group of genes on chromosome eight. They identified the genes FLJ14299, C8orf2, BRF2 and RAB11FIP as candidates for involvement in the development of at least some forms of breast cancer, of which 41,000 new cases are diagnosed in Britain each year.

Carlos Caldas said the "exciting advance" heralded a new era in the discovery of genes linked to disease, although more needed to be done to understand their exact role in this case.

"Scientists have been trying to pinpoint the genes on chromosome eight involved in breast cancer development for the last two decades and DNA microarrays have allowed us to greatly accelerate the search," he said. "Early indication are that tumours with multiple copies of these genes are more aggressive. If this is confirmed, it might provide a lead for targeted therapies in these cases."