Breast Cancer Genetics Takes Big Leap Forward

SUNDAY, May 27 (HealthDay News) -- Researchers say they've moved much closer to untangling the genetic threads that raise a woman's chance for breast cancer.

A set of studies published Sunday in the journalsNatureandNature Geneticsidentified four new breast cancer susceptibility genes, as well as several genetic markers, that are associated with the risk for the disease and that deserve further investigation.

The findings may be the most important genetic discoveries relating to breast cancer genetics since the identification of theBRCA1andBRCA 2susceptibility mutations in 1994, experts say.

"With these three reports, we've doubled or more the number of genes in which inherited variations are known to be associated with an increased risk of breast cancer. It's a big quantum of new knowledge," said David Hunter, lead author of one of the papers and co-author on another.

"What we hope will happen is that each of those genes or gene regions will lead us to better understand the mechanisms and biology behind breast cancer," he said. "And that with that better understanding, we'll be able to develop improved means of prevention and treatment."

Hunter is professor of cancer prevention at the Harvard School of Public Health and an epidemiologist with Brigham & Women's Hospital, both in Boston.

Other experts echoed those sentiments. Because the research involved such a large team of international researchers, it was difficult to identify experts who hadnotbeen involved with the odyssey in one way or another.

"These findings are really very exciting. Ever sinceBRCA 1andBRCA 2, we have been looking for genes associated with breast cancer, and there haven't been many identified," said Heather Spencer Feigelson, a co-author on one of the papers and strategic director of genetic epidemiology at the American Cancer Society in Atlanta. "These are three independent, genome-wide association studies coming out simultaneously that give us some new clues."

"It means a tremendous amount. It's very exciting," added Dr. Stephen Chanock, who was involved in two of the papers and is a senior investigator at the U.S. National Cancer Institute. "This opens a whole series of new doors for therapy and, when we can start to explain it better, prevention."

Mutations in theBRCA1andBRCA2genes, the best-known susceptibility genes identified thus far, increase a woman's risk of developing both breast and ovarian cancer. But these genes account for only a small proportion of total breast cancer cases, because the frequency of the mutations is so low in the general population.

"TheBRCA1and2genes were milestones in cancer research, but they are rare mutations," Chanock said. "If you have one of those, you have a particularly higher risk of developing breast or ovarian cancer, but 95 percent of the population is not affected by these rare but very significant genes."

Other genes have also been implicated in breast cancer susceptibility but, again, most of these are rare.