Researchers identify location of breast density genes

In collaboration with the Press Association

US scientists have identified a region of the human genome that is associated with having denser breast tissue, a known risk factor for breast cancer.

Women with dense breasts - where the tissue contains a relatively small proportion of fat - are three to five times more likely to develop breast cancer than women with less dense breasts, research has shown.

The finding, which is published in the journal Cancer Research, could enable doctors to identify women at higher risk of breast cancer, as the genes could be used as a predictive 'DNA marker' for the disease.

Researchers at the Mayo Clinic and H Lee Moffitt Cancer Centres studied the DNA of 889 people from 89 families in Minnesota, who were taking part in a multi-generational study that began in 1944.

They were able to identify a region on a single chromosome - chromosome 8 - that appears to be significantly associated with increased breast density.

The region is thought to contain around 45 known genes.

Dr Celine Vachon, an epidemiologist at the Mayo Clinic and lead investigator on the study, said that it "provides further evidence that this trait does appear to be genetically influenced".

"At this point, we have not identified a gene or genes for breast density but a promising location to investigate further," the researcher noted.

"One or more of the 45 candidate genes in this region could explain a large proportion of mammographic breast density and, potentially, breast cancer.

"Identification of genes for breast density will improve our understanding of how breast density influences breast cancer development in women."

The researchers also revealed that a gene which encodes the prolactin receptor may be a possible contributor to dense breasts.

Prolactin is a hormone that helps to enlarge the mammary glands during pregnancy and is involved in milk production. Levels of prolactin have also previously been linked to breast density in postmenopausal women.