US researchers have identified a gene which has a role in the development of an aggressive form of breast cancer.
Scientists from the University of Michigan Comprehensive Cancer Center found that the gene, FOXP3, inhibits the growth of tumours in mice.
When the gene was deactivated, 90 per cent of the mice developed cancerous tumours.
Furthermore, around 80 per cent of the breast cancer tissue analysed did not express FOXP3 at all.
The researchers also found that FOXP3 represses HER-2, a protein associated with more aggressive forms of breast cancer.
Yang Liu, one of the authors of the study and co-director of the cancer immunology program at the Comprehensive Cancer Center, said: "FOXP3 defects promote cancer development."
He added: "We do not know whether this is a genetic defect that puts women at higher risk. For treatment, this gene could be quite important, but for diagnosis, it’s too early to tell."
FOXP3 is just one of two genes linked to cancer which have been found on the X chromosome.
This means a single mutation can silence the gene.