ROANOKE TIMES
Copyright (c) 1995, Roanoke Times
DATE: Thursday, December 21, 1995 TAG: 9512210088
SECTION: NATIONAL/INTERNATIONAL PAGE: A-12 EDITION: METRO
DATELINE: NEW YORK
SOURCE: Associated Press|
An international team of scientists has identified a second major breast cancer gene that makes some women highly susceptible to the disease.
In families with a strong history of breast cancer, women who inherit a defective version of the gene run about an 80 percent lifetime risk of getting the disease.
The gene is called BRCA2, and its discovery follows the identification of BRCA1 last year. Together, the genes account for perhaps 90 percent of breast cancers from inherited susceptibility, with BRCA2 responsible for maybe 40 percent.
Last year, scientists announced that they had narrowed the search for BRCA2 to a small area of chromosome 13. The new study says researchers have captured a chunk of the gene itself.
The work is reported in today's issue of the journal Nature by Dr. Michael Stratton of the Institute of Cancer Research in Surrey, England, P. Andrew Futreal of the Duke University Medical Center in Durham, N.C., and others. The paper has 38 authors from six countries.
In another development Wednesday, Myriad Genetics Inc. of Salt Lake City announced that its scientists have recovered the entire BRCA2 gene. The company said it plans to use it in combination with BRCA1 to develop a test for predisposition to hereditary breast cancer.
Only about 5 percent to 10 percent of breast cancer cases are thought to come from inheriting a faulty gene. The cause of the vast majority of cases of breast cancer is not known, although scientists are investigating possible hormonal and other triggers.
Scientists hope studying inherited breast cancer genes will teach them about the basic biology of breast cancer, which someday could pay off with new treatments and ways to prevent the disease.
More immediately, the finding will let members of the relatively few families affected by BRCA2 find out if they carry the gene, which also raises the risk of breast cancer in men.
But the researchers who wrote the report in Nature said it's too soon to start testing the general population for the presence of a defective BRCA2 gene.
They report that the gene was mutated in members of six families with strong histories of the disease, but not in healthy women.
Like BRCA1, the newfound gene seems to suppress cancer when it is working normally. But when BRCA2 is defective, this brake is lost.
Everybody inherits two copies of BRCA2, one from each parent. If one copy is defective when inherited, then ``every cell in your breast is already primed'' for cancer because the single remaining copy can become damaged within the woman's body, Futreal said.
He also said scientists are working feverishly to see if such damage to BRCA2 also plays a role in noninherited breast cancer.
While BRCA2 has the effect of suppressing cancer, scientists don't know what its normal job is, Stratton said.
Stratton and Futreal said it's too early to screen the public for BRCA2. Scientists don't know whether other genes or environmental factors modify the breast cancer risk from a faulty BRCA2 gene, Stratton said.
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