A gene that was thought to cause only a small proportion of breast cancers now appears to be at the heart of nearly all of them, researchers report.
The finding may lead to new ways to give a prognosis and to treat breast cancer, but there is no immediate action recommended for women who have breast cancer or are concerned about a genetic predisposition to the disease.
Researchers are excited about the finding because it means that the rare forms of breast cancer that run in families appear to be not distinct from the most common forms of breast cancer, but instead linked to them.
The gene in question, known as BRCA-1, was isolated just a year ago, after a heated race among molecular biologists who felt certain that it would provide vital clues to the causes of breast and ovarian cancers. It did. Women who inherited a mutated form of the gene had about a 90 percent chance of developing breast cancer and about a 60 percent chance of developing ovarian cancer in their lifetimes.
But women with familial breast cancers constitute just 5 percent all women with the disease, so the finding seemed of minor importance for the vast majority of women who might contract breast cancer. When researchers examined cancers from women who did not have a strong family history of the disease, the gene seemed normal.
Now, Dr. Wen-Hwa Lee and his colleagues at the University of Texas at San Antonio report that women with breast and ovarian cancers but no family history of the disease have certain abnormalities related to this same gene. The abnormalities have to do with a protein called the BRCA-1 protein; the BRCA-1 gene instructs the cells to make this protein.
L The finding is being published today in the journal Science.
Normally, this protein is successfully produced and does its work in the cell nucleus. In the rare familial breast cancers, the gene produces a faulty form of the protein. In the more common forms of breast cancer, the researchers report that the protein is misplaced, found in the wrong part of the cell.
Dr. Barbara Weber of the University of Pennsylvania School of Medicine said the finding "means that this gene may be what we hoped for -- a tool to really understand why breast cancer happens."