New Breast Cancer Gene Found

But BRIP1 accounts for only a fraction of familial cases, researchers say

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By Kathleen Doheny
HealthDay Reporter

MONDAY, Oct. 9, 2006 (HealthDay News) -- Scientists say they've spotted a new breast cancer susceptibility gene that might someday help women ascertain their risk for the disease.

Women with mutations in the gene, called BRIP1, have twice the normal risk of breast cancer, British researchers report in the November issue of Nature Genetics.

"Others have proposed that it might be associated with breast cancer, but we are the first to actually show it," said Dr. Nazneen Rahman, a professor of cancer genetics at the Institute of Cancer Research in Sutton, England.

Still, BRIP1 probably plays only a minor role in breast cancer risk generally, the researchers added, since the mutation itself is uncommon. The increase in risk associated with this gene is small in relation to the risk associated with mutations in other breast cancer genes, such as the better-known BRCA1 and BRCA2.

While mutations in BRIP1 increased a woman's risk for breast malignancy twofold, other gene mutations raise it much more. According to background information in the new study, mutations in BRCA1, 2, and another gene, TP53, increase the carrier's risk of breast cancer by 10- to 20-fold by age 60. Women with BRCA mutations have up to an 80 percent chance of developing breast cancer in their lifetimes, estimates the American Cancer Society. Mutations in other genes -- such as CHEK2, ATM and the newly identified BRIP1 gene -- are associated with a more modest risk increase.

In their study, Rahman's team screened more than 1,200 breast cancer patients who also had a family history of either breast or ovarian cancer for mutations in the BRIP1 gene. None of the women had mutations in either BRCA1 or 2.

Rahman's team found that nineof the women had mutations in the BRIP1 gene. In a control group of healthy women without breast cancer, just two of the nearly 2,100 women tested had the mutation.

The likelihood that a woman with mutations in BRIP1 would also have mutations in the other breast cancer-related genes is unlikely, Rahman said, "as all of these [mutations] are relatively rare."

Less than 1 percent of American women have a BRCA1 or BRCA2 mutation, according to the American Cancer Society. BRCA1 and 2 genes normally function as tumor-suppressing genes, so mutations in either can make them incapable of preventing breast malignancies.

The new study adds valuable information for researchers, although it doesn't mean women should get tested for the new mutation, said Andrew Godwin, director of the Clinical Molecular Genetics Laboratory and the Biosample Repository at Fox Chase Cancer Center, Philadelphia.

Previous research, he said, found that this gene "did not appear to have mutations that lead to an increased risk of breast cancer." But the previous study was much smaller, he said, and, in the case of the Rahman research, "because they screened so many people, they found a different type of mutation in this BRIP1" compared to the previous research.

While the frequency of this newly identified mutation in the population is low, the new research helps breast cancer researchers determine just how many of these genetic mutations are involved in the disease, Godwin said.

"Susceptibility genes" that have been identified so far account for up to 25 percent of familial breast cancer risk, Rahman said. So, there's still a long way to go to completely solve the puzzle.

The take-home point for women: "In breast cancer families without BRCA 1 or BRCA 2 gene mutations, there are likely to be several different genes, each with small (for example twofold) effects which will be acting together with each other and other non-genetic factors," Rahman said.

She agreed with Godwin that women shouldn't automatically be screened for this the BRIP1 mutation. Much more research is needed before that routinely happens, Rahman said.

More information

To learn more about breast cancer susceptibility genes, visit the American Cancer Society.

SOURCES: Andrew Godwin, Ph.D., director, Clinical Molecular Genetics Laboratory and the Biosample Repository, Fox Chase Cancer Center, Philadelphia; Nazneen Rahman, M.D., Ph.D., professor, cancer genetics, Institute of Cancer Research, Sutton, Surrey, U.K.; November 2006, Nature Genetics

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