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Breast cancer risk amplified by additional genes in combo with BRCA mutation

April 17th, 2008 posted by Josh Hill

Many women with a faulty breast cancer gene could be at greater risk of the disease due to extra risk-amplifying genes, according to research published this month in the American Journal of Human Genetics.

Researchers at the University of Pennsylvania School of Medicine join an international consortium of research groups that looked at more than 10,000 women carrying a BRCA1 or BRCA2 mutation for breast-cancer risk.

“These results suggest that knowledge of a BRCA1 or BRCA2 mutation is necessary, but not sufficient, to fully understand cancer risk in women who carry these mutations,” says co-author and head of the North American coalition Timothy R. Rebbeck, PhD, Professor of Epidemiology at Penn. “This paper demonstrated that other genes, and possibly exposures, could provide important information that may refine our ability to predict cancer in this high-risk population. Because carriers of BRCA1 or BRCA2 mutations are relatively rare in the population, the only way to undertake studies of this type is by forming large consortia.” Rebbeck is also the Associate Director for Population Science at Penn’s Abramson Cancer Center.

“This is the first time we have found evidence that common changes in other genes can amplify the risk of breast cancer in women known to have faulty BRCA genes,” says lead author Professor Doug Easton, director of Cancer Research UK’s Genetic Epidemiology Unit at the University of Cambridge. “This is the first step in finding a set of genes that modify the risk in BRCA carriers, and may influence how we monitor women with a family history of the disease.”

The international team of scientists have found that common versions of two genes – FGFR2 and TNRC9 – known to increase breast cancer risk in the general population – also increase the risk in women carrying damaged versions of the BRCA2 gene.

Around one in eighteen women will develop breast cancer by the age of 65. On average, half of women carrying a faulty BRCA2 gene will develop the disease by the age of 70.

This study found that particular combinations of the FGFR2 and TNRC9 genes modify breast cancer risk in BRCA2 mutation carriers. One percent of BRCA2 mutation carriers have the highest risk combination of FGFR2 and TNRC9 genes. Seven in every 10 women in this category are predicted to develop breast cancer.

Around twenty percent of the BRCA2 mutation carriers have the lowest risk combination of the FGFR2 and TNRC9 genes. The researchers found that their risk is lowered so four in every 10 women in this category are expected to develop the disease.

These findings are the first step in a series of studies hunting for breast cancer susceptibility genes, which aims to better monitor and treat women with a family history of the disease.

Source: University of Pennsylvania School of Medicine

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    Changes in certain genes increase the risk of breast cancer. These genes include BRCA1, BRCA2, and others. Tests can sometimes show the presence of specific gene changes in families with many women who have had breast cancer. Health care providers may suggest ways to try to reduce the risk of breast cancer, or to improve the detection of this disease in women who have these changes in their genes.
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    The past century has seen many medical breakthroughs and detecting mutations in gene is definitely one of the most amazing of them. Women at high breast cancer risk can now take up a genetic testing to know whether they are BRCA2 positive. Hopefully, someday scientists will work out a procedure to correct the abnormalities in genes causing cancer. But for now, there are a number of preventive measures to choose from.

    For a woman, testing BRCA2 positive means she is at much higher-than-average risk of developing breast cancer in her lifetime. It means that a woman is 3 to 7 time more likely to develop breast cancer than any other woman without any gene abnormalities. It also means that she is at 16% to 60% more risk of developing ovarian cancer in her lifetime. Being BRCA2 positive also means that there are 50% chances of passing the abnormalities to the children.

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