In New Zealand, around one in every 250 women inherits one of the mutations looked at in the study. Photo: 123RF
A global study led by the University of Otago has discovered a gene that, when modified, could reduce the risk of breast cancer.
Finding the new gene also opens the door to developing a drug that reduces the risk of cancer.
The research involved 26,000 women known to have the BRCA-1 and BRCA-2 mutations of the breast cancer genes, the largest study of its kind.
"That instantly made us look to see what gene that was" - University of Otago associate professor Logan Walker
"The discovery came after looking at thousands of women around the world," said associate professor Logan Walker, who led the study.
"It allowed us to look at genetic changes; these genetic changes pointed us in a direction where we could see that for some women who were at a high risk of developing breast cancer, they also inherited another genetic change which lessened that risk.
"That instantly made us look to see what gene that was, what protein that was producing and could we effectively inhibit that protein in a medical sense to reduce risk for those women."
In New Zealand, around one in every 250 women inherits one of these mutations.
Currently, the most effective strategy for these women at high risk of breast cancer is a bilateral mastectomy.
Walker said although surgery was effective, it could cause ongoing psychological and physiological harm to patients, especially to younger women.
Researchers said reducing the levels of protein produced by the new gene, SULT1A1, lowered the chance of a woman getting breast cancer - especially if she also has a mutation in the BRCA-1 gene.
"When we turned down the activity of the SULT1A1 gene in breast cells, the cells grew more slowly and were more resistant to DNA damage," Walker said.
Logan Walker. Photo: University of Otago / Supplied
The researchers also discovered that women who have the BRCA-1 gene with segments missing are at the highest risk of developing breast cancer.
Otago's Dr George Wiggins is leading the next step: developing a risk-reducing drug.
"Prophylactic drug treatments are becoming well-established for the prevention of different diseases," said Walker. "For example, aspirin, statins and anti-hypertensive therapies have had a major impact on reducing incidence of cardiovascular disease and extending life expectancy.
"By comparison, progress in therapeutic intervention to prevent breast cancer has been poor. Providing a non-invasive and easily accessible preventative therapy for women at high risk of developing breast cancer would have numerous benefits for the health system, and for the patients and their whānau.
"Such a therapy could give genetically predisposed young women the opportunity to bear and breastfeed their children by delaying or supplanting the need for risk-reducing surgery."
Breast cancer is the most commonly diagnosed cancer in Māori and non-Māori women, with more than 3300 new cases and 600 deaths per year.
"Uptake of risk-reducing surgery can also be a barrier to breast cancer prevention for many individuals, contributing to inequity in health outcomes," Walker said.
"Effective prevention strategies for women at increased risk of breast cancer are vital for controlling and reducing the social and economic impact of this disease."
The study was funded through a grant from the Health Research Council of New Zealand.