Scientists discover first DNA region to alter breast cancer risk in women with BRCA1 faults

Cancer Research UK scientists have identified a DNA region which can increase or decrease the high breast cancer risk associated with the BRCA1 gene. The region is particularly involved in oestrogen receptor negative breast cancer and has also been linked to an increased risk of ovarian cancer in the general population.

The research is published in Nature Genetics today (Sunday) alongside two other independent studies linking this region and four others to ovarian cancer.

Two independent research groups identified the same region after carrying out genome-wide association studies*. Researchers led by Dr Antonis Antoniou based at the Cancer Research UK Centre for Cancer Genetic Epidemiology at the University of Cambridge, identified the region after searching through the genomes of more than 2,300 women with faults in the BRCA1 gene, to find other sections of DNA which could alter breast cancer risk.

Meanwhile researchers led by Dr Simon Gayther, based at the Cancer Research UK Genetic Epidemiology Unit, at the University of Cambridge and UCL (University College London), pinpointed the same region after carrying out a similar study looking at nearly 9,000 women with ovarian cancer from the general population.

On average, around 65 per cent of women carrying a faulty BRCA1 gene will develop breast cancer – and around 40 per cent ovarian cancer – by the age of 70.

These studies reveal that if a woman with a BRCA1 fault also carries the risk ‘version’ of the 19p13 region, her breast cancer risk may be higher still.

Dr Antonis Antoniou, lead author on the breast cancer study and scientist at the Cancer Research UK Centre for Cancer Genetic Epidemiology, University of Cambridge, said: “We’ve found a DNA region that acts like a volume control – to turn up or down the risk of developing breast cancer from faults in the BRCA1 gene.

“Our discovery is the first step in a much larger study to identify genetic factors that modify breast cancer risk in women carrying BRCA1 mutations, and ultimately could help assess the risk for each woman and monitor for the disease.”

The same DNA stretch was also associated with the risk of developing oestrogen receptor negative breast cancer in women without a faulty BRCA1 gene, and also associated with the risk of developing triple negative breast cancer – oestrogen, progesterone and HER2-negative breast cancer.

In a separate study in Nature Genetics today, the same region was also shown to increase the risk, to a lesser degree, of ovarian cancer in women who don’t carry a BRCA1 fault.

Dr Simon Gayther at UCL, who is lead author on this study and whose work is supported by Cancer Research UK and the Eve Appeal, said: “Our study showed that the same genetic region also plays a role in ovarian cancer, suggesting that it is involved in the same faulty pathway.

”This is important because it suggests that women who carry certain versions of this DNA stretch could benefit from closer monitoring for both breast and ovarian cancers.”

Dr Andrew Berchuck, head of the international Ovarian Cancer Association Consortium (OCAC) steering committee and an author on the study, said: “The critical validation of these findings was performed by large consortia of investigators from around the world, and this research represents a triumph of science without borders for the benefit of all women.”

A third study, led by Dr Paul Pharoah, also at the Cancer Research UK, Centre for Cancer Genetic Epidemiology at the University of Cambridge and UCL, and published in the same journal today, reveals four other separate genetic regions also associated with ovarian cancer risk in the general population.

Dr Lesley Walker, Cancer Research UK’s director of cancer information, said: “We’re dedicated to unravelling cancer risk so we can provide doctors with better tools to identify who is at risk and help select the best treatment.

“This research provides evidence that by carrying out genome wide association studies in certain subgroups – such as people with BRCA1 mutations – we can identify other breast and ovarian cancer risk factors which have previously been missed.”

ENDS

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