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Scientists in Utah, working with others around the world, have isolated a gene that may influence inherited susceptibility to some forms of breast and ovarian cancers.

The discovery of BRCA1 (for breast cancer gene 1) could lead to a blood test for susceptibility to certain breast and ovarian cancers. But research also indicates that these mutations may not be critical in the development of most breast and ovarian cancers.Researchers at Myriad Genetics Inc., based at Research Park, and at the University of Utah collaborated with experts in New York, North Carolina, Indiana, Canada and Sweden. The overwhelming majority of authors of two crucial studies on the genetic defect are Utahns.

Their work is detailed in articles to be printed soon in Science, a magazine published by the American Association for the Advancement of Science, Washington, D.C. Many of the same researchers worked on both projects.

In addition, a group mostly at the U. has discovered the general location of BRCA2 but has not yet isolated it.

David Goldgar of the U. worked on both BRCA1 and BRCA2 proj-ects.

"It's more a coincidence than anything else," he said of the two different genetic discoveries. "Our group at the U., in collaboration with a group in England, has for two years now been trying to find breast cancer genes other than BRCA1."

The two defects may prove to be equally important, he said.

An article titled "Isolation of BRCA1" says the BRCA1 gene influences susceptibility to breast and ovarian cancer. The gene, whose general location has been known for some time, was identified through cloning.

"Identification of BRCA1 will facilitate early diagnosis of breast and ovarian cancer susceptibility in some individuals as well as a better understanding of breast cancer biology," the article adds.

Another report, "BRCA1 Mutations in Primary Breast and Ovarian Carcinomas," shows that the discovery probably won't help in detecting most breast cancers.

Research reported in that article says that BRCA1 encodes a tumor suppressor. The team checked breast cancers and ovarian cancer tumors to see if the BRCA1 gene was defective there.

Three of 32 breast cancers checked had defects in the BRCA1 gene, and one ovarian cancer out of 12 checked had a BRCA1 defect.

"Therefore, mutations of BRCA1 may not be critical in the development of the majority of breast and ovarian cancers," which arise in the absence of a genetic mutation, it says.

This isn't the definitive way to determine if a woman will have breast or ovarian cancer, as other causes besides BRCA1 are believed responsible for most cases.

But isolating the gene means it should be relatively easy to develop a blood test to see if a defective BRCA1 is present.

"When a test is available, presumably women who feel they are at risk because they have a family history (can get) a test that will tell them whether or not they've inherited the gene," Goldgar said.

"That presupposes that the breast cancer in their relatives is due to BRCA1."

In overall cases of breast cancer, he emphasized, a relatively small proportion is caused by defects in BRCA1. This genetic defect is more prevalent in breast cancer developing in younger women than in older women.

Besides the Utahns, research to isolate the BRCA1 gene was carried out by the National Institutes of Health at Research Triangle Park, N.C.; McGill University, Montreal, Quebec; and Eli Lilly and Co., Indianapolis.

Checking for BRCA1 genetic mutations in breast and ovarian tumors were Utah teams, plus the National Institutes of Health; the Department of Occupational Medicine at Tab Linkoping, Sweden; Sloan Kettering Cancer Center, New York City; and Duke University Medical Center, Durham, N.C.