Scientists have taken a step forward in their effort to understand why a key gene may increase the risks of developing breast cancer.
One in nine women will develop breast cancer
They have discovered how the gene, called Aurora2, works.
This gene is over-expressed in 16% of all breast cancers and in up to 94% of the most common form of the disease, invasive ductal adenocarcinoma.
The scientists believe their discovery could help in the development of new drugs to fight breast cancer.
Researchers from the UK charity Breakthrough Breast Cancer and the University of California San Francisco studied Aurora2.
They found that some versions of this gene were less able to interact with other genes in cells in the breast.
This increases the risks that the cell may turn cancerous.
Scientists believe that identifying women with this version of Aurora2 could also identify those at increased risk of developing breast cancer.
They also believe it could help in the development of new drugs targeted at those women in this high-risk group.
Dr Spiros Linardopoulos, head of Breakthrough's novel drug targeting team, said: "Although genes like Aurora2 carry a lower risk of causing breast cancer than well-known, high-risk susceptibility genes like BRCA1 and 2, they may be a more common cause of cancer in the population."
Professor Alan Ashworth, director of the Breakthrough Research Centre, said: "Understanding more about the genes involved in breast cancer and the biology of the breast... is essential if we are to find better diagnostic techniques and safer, targeted treatments.
"The analysis of the role of Aurora2 is a significant and welcome step in that direction."
Breast cancer is now the most common cancer in UK women, accounting for 1 in 4 of all female cancers.
Around 40,000 new cases of breast cancer are diagnosed in the UK each year and approximately 14,000 women die of the disease every year.
One in nine women will develop breast cancer at some point during their life.
The study is published in the journal Nature Genetics.