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New Gene Suspect in Breast Cancer

Preliminary finding involves older women

TUESDAY, June 12, 2001 (HealthDayNews) -- California researchers have added another gene to the short list of those known or suspected of affecting the risk of breast cancer.

A study of older white women found a substantially increased risk for the disease in those who carried one specific form of the TGF-beta-1 gene. But the link between the gene and the breast cancer is tentative and needs a lot more work, says Dr. Elad Ziv, a postdoctoral fellow at the San Francisco Department of Veterans Affairs Medical Center. He reports the research in the June 13 Journal of the American Medical Association.

"This is a very good candidate gene. Its biology suggests that it is potentially an important factor in breast cancer risk," Ziv says.

The TGF-beta gene (TGF stands transforming growth factor) produces proteins that help regulate cell division and tissue proliferation. Animal studies have found that increased activity of TGF-beta-1 protects against early development of breast cancer and other tumors.

Everyone carries two copies of the gene, one from each parent. The two versions of the gene are designated T and C. Ziv and his colleagues looked at the incidence of cancer in a group of white women over age 65 and the versions, or alleles, of the gene each carried.

About 85 percent of the women in their study had either one or two T versions of the gene, and therefore could have a 60 percent higher risk of breast cancer, say the researchers. "Thus, if this association is real and causal, this allele is associated with a substantial fraction of cancers among older women in the United States," theyt write.

That is a big "if," Ziv says. First, he says, "More studies are necessary among other age groups and other ethnic groups." Second, "there were other candidate genes that turned out to be not what was thought. It is premature to think of this as a final study."

Still, the potential is there. Other genes have been associated with an increased risk of breast cancer, most notably the genes designated BRCA-1 and BRCA-2. Ziv says the versions of those genes associated with breast cancer risk are rare, but women who carry them have a 50 to 80 percent lifetime risk of breast cancer.

Ziv says the TGF-beta-1 gene "is a much more common variation that is associated with a much more moderate risk."

The genetic story of breast cancer is just beginning to be told, Ziv says: "We need more studies of this type, looking at this gene in other populations and other variations of other genes."

Dr. Katrina Armstrong, associate professor of medicine at the University of Pennsylvania School of Medicine and author of an accompanying editorial, says, "This study offers another small step forward, but breast cancer is a very complex disease with a very complex etiology."

"This offers another piece of the puzzle. I would hope that over the next several years we can start putting pieces of the puzzle together so that we can provide clinical information that is meaningful," Armstrong says.

Both environmental and genetic factors are associated with breast cancer risk, and so "we need to start understanding how this gene interacts with other factors that we know increase the risk of breast cancer," she says.

What To Do

While basic genetic research goes on, women should pay attention to established methods of risk reduction and early detection of breast cancer, such as periodic mammograms.

The American Cancer Society and the National Cancer Institute have more on breast cancer, as do these HealthDay articles.

If you have the disease and are interested in clinical trials, visit Veritas Medicine.

SOURCES: Interviews with Elad Ziv, M.D., postdoctoral fellow, Department of Veterans Affairs Medical Center, San Francisco, and Katrina Armstrong, M.D., associate professor of medicine, University of Pennsylvania School of Medicine, Philadelphia; June 13, 2001 Journal of the American Medical Association
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