Breast cancer risk gene may predict odds

Researchers have used new technology to fast track the discovery of a breast cancer risk gene that could assist in the discovery of other cancer genes. Professor Melissa Southey of the University of Melbourne, who led the study, says it was a significant discovery and the first breast cancer risk gene to be discovered using the latest genetic sequencing technology. “The mutations in the newly identified gene XRCC2, although rare, explain another proportion of breast cancers that run in families where there is no known genetic cause and that particularly occur at an early age,” she says. “We identified this gene quite quickly using genetic technology called massively parallel sequencing, which enables sequencing of large amounts of human DNA at high speed. “Due to these results and our methodology we believe that further breast cancer risk genes will be identified at a faster rate than before and potentially for other cancers such as colorectal and prostate cancers,” says Southey, of the Genetic Epidemiology Laboratory, in the department of pathology. Southey says the discovery could help manage the risk of breast cancer for families with a strong history of the disease and no known genetic cause. “This discovery will assist some families to determine individual risk and which family members are at high risk of contracting the disease,” Southey says. The findings are published in the American Journal of Human Genetics. “Unaffected relatives of people with a mutation in this gene could also be offered predictive testing, subsequent genetic counseling and ongoing clinical management on the basis of their mutation status. “People whose breast cancer is associated with XRCC2 mutations could also benefit from specific treatments that target the genetic fault,” she says. Currently, only about 30 percent of the familial risk for breast cancer has been explained, leaving the substantial majority still unaccounted for. “Research indicates that no single gene is likely to account for a large proportion of the remaining unexplained genetic susceptibility to breast cancer,” says Southey. “Although mutations in XRCC2 are rare, it is most likely that the remaining unknown breast cancer susceptibility genes will account for similar small proportions of the disease.” Initially, using massively parallel sequencing, researchers identified XRCC2 mutations in two families, in Melbourne and the Netherlands. This was followed by a larger series of studies using DNA from blood samples of 689 families with multiple members affected by breast cancer, and from 1308 women who were affected at an early age by breast cancer and recruited from the general population, as well as 1120 controls. More XRCC2 mutations were detected in the breast cancer cases but not in the controls. These additional studies were conducted in Melbourne and at the International Agency for Research on Cancer (IARC) in France. Co-first author Daniel Park, who worked with Fabienne Lesueur of IARC, says the study demonstrates the power of massively parallel sequencing for discovering susceptibility genes for common, complex diseases like breast cancer. “Our study approach could be applied to many other common, complex diseases with components of unexplained heritability, such as colorectal and prostate cancers,” he says. Southey oversaw this work with two long-standing collaborators and experts in the field of breast cancer genetics, Sean Tavtigian and David Goldgar at the University of Utah. The research was conducted in a large collaborative network including researchers at institutions in the United States, Australia, and France. Their work was supported by The Cancer Council Victoria, National Institutes of Health, and the National Health and Medical Research Council of Australia.