Scientists Find Four New Breast Cancer Genes

Scientists have found four new genes that may play a role in breast cancer -- a finding which could one day improve screening for the disease which strikes one in nine women.

But perhaps just as important is the method used by Cancer Research UK and an international group of scientists in mounting the large-scale hunt for these genetic culprits -- a genome-wide search that may revolutionize how researchers look for disease-causing genes in the future.

University of Cambridge scientist Dr. Douglas Easton and his colleagues looked at the genetic makeup of nearly 50,000 women to find these new genes. What they found was that women at a high risk of cancer consistently showed differences in the general neighborhood of these four genes -- suggesting that they play a role in breast cancer development.

The study is published in the current issue of the journal Nature.

"This is an outstanding discovery," says Dr. Harpal Kumar, Cancer Research UK's chief executive, in a press release on the study issued Sunday.

"These findings will open doors for cancer researchers across the globe to unearth even more genes linked to cancer, and ultimately this will benefit patients," Kumar said.

"What electrifies the scientific community about these discoveries is that they point towards novel pathways or mechanisms that may help us unlock the secrets of this deadly disease," said Dr. Francis Collins, director of the National Human Genome Research Institute.

New Genes Common

Because a woman's genetic background clearly increases her risk of breast cancer, scientists are constantly searching for the genes that cause it.

The four new breast cancer genes are very common, with a high proportion of the population carrying at-risk genes. For example, Easton and his colleagues estimate that 14 percent of the female population in the United Kingdom carries one of these genes.

But the researchers say that the increases in risk associated with the newly identified genes are likely small compared to the risk associated with previously identified breast cancer genes BrCA1 and BrCA2, which increase a woman's lifetime risk of breast cancer to between 50 percent and 85 percent.

Since these genes confer such a small increase in breast cancer risk, they are not appropriate for genetic testing at this point.

"For most women it doesn't really change any particular advice or anything," Easton said. "People should not generate anxiety in tests for these genes."

In fact, these four genes may just be a drop in the bucket considering the vast number of genes that likely contribute in some way to a woman's risk of breast cancer.

"There is no single breast cancer gene just as there is no single diabetes gene or prostate cancer gene," notes Dr. Teri Manolio, director of population genetics at the National Human Genome Research Institute. "What we have is many genes of small effect that, working together and with specific -- and as yet largely unknown -- environmental exposures, cause a woman to develop breast cancer."

Still, as more breast cancer genes are found, a comprehensive test to search for a multiple low-risk genes could prove useful.

"Looking at many risky genes may be better able to predict one's chance of getting breast cancer than looking at any single index alone," comments Debu Tripathy, clinical professor of internal medicine at University of Texas Southwestern Medical Center.

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