London: In a worldwide study of the DNA of 100,000 women, British scientists have discovered two new genetic variants associated with an increased risk of breast cancer.
The team from the Institute of Cancer Research, London, analysed the DNA of around 86,000 women of European, 12,000 of Asian and 2,000 of African ancestries - around half of whom had breast cancer.
The genetic variants are specifically linked to the most common form of breast cancer - oestrogen receptor positive.
"The study zoomed in on an area of our genome that we knew was linked to breast cancer risk and has identified two new genetic variants that add significantly to our knowledge about the genetic causes of the disease," said study leader Nick Orr from the Institute of Cancer Research.
The study's identification of two new genetic risk factors for breast cancer provides important clues about the causes of the disease - implicating a gene called KLF4, which is thought to help control the way cells grow and divide.
Women with the first genetic variant identified, called rs10816625, were 12 percent more likely to develop breast cancer than women without, and those with the second variant, rs13294895, at a nine percent increased risk.
The genetic variants are thought to help control the activity of KLF4, despite lying a long distance away from that gene.
Both were associated with increased risk in European women but only one of them - rs10816625 - in women of Asian ancestry.
"The two new variants uncovered by this study could be factored into potential future screening tools for breast cancer that incorporate all known genetic risk factors for the disease," said professor Paul Workman, chief executive of the Institute of Cancer Research.
The research involved scientists from more than 130 institutions worldwide - including the London School of Hygiene and Tropical Medicine and the University of Cambridge.
The study was published in the journal Human Molecular Genetics.