ROANOKE TIMES
Copyright (c) 1997, Roanoke Times
DATE: Tuesday, March 25, 1997 TAG: 9703250086
SECTION: VIRGINIA PAGE: C-3 EDITION: METRO
DATELINE: RESTON
SOURCE: ASSOCIATED PRESS
The variation may roughly double the risk of breast cancer and could be responsible for 30 percent of all cases of the disease.
A common variation of a gene that controls estrogen production appears to influence when girls go through puberty and whether they get breast cancer someday.
Researchers estimate that having this genetic variation, which is carried by 40 percent of women, may roughly double the risk of breast cancer and could be responsible for 30 percent of all cases of the disease.
The gene, called CYP17, is one of several that regulate the body's production of estrogen, the sex hormone that plays a major role in breast cancer.
The latest research, conducted by Dr. Brian E. Henderson and colleagues from the University of Southern California, was presented Monday at a conference sponsored by the American Cancer Society.
So far, the search for the genes that cause breast cancer has focused largely on two that are very rare but substantially increase the risk. These genes, called BRCA1 and BRCA2, may raise the risk of breast cancer 20 times or more, especially in younger women, but they probably account for only about 4 percent of all breast cancer.
Researchers are also looking for genes that are far more common but much less likely to trigger breast cancer. Among these is CYP17.
This gene holds the code for making an enzyme known as cytochrome P450c17. It's involved in one step in the complex chemical pathway in the body that leads to production of a form of estrogen called estradiol.
Everybody gets two copies of the gene, and it comes in at least two slightly different forms, which the researchers call A1 and A2. The researchers have preliminary evidence that women who get at least one copy of A2 produce more estradiol, start having menstrual periods at a younger age and have an increased risk of breast cancer that spreads to other parts of their bodies.
Henderson said that sorting out this and other genes involved in breast cancer may someday help doctors assess women's risk of the disease while they are still healthy.
But for now, he said, ``the most important thing about this work is understanding the biological underpinnings of breast cancer.''
Henderson and colleagues studied 174 women with breast cancer and 285 healthy women with no history of the disease.
They found that women with at least one copy of A2 started menstruating at age 13, while those with two copies of A1 started an average of five months later.
Doctors have long known that the sooner a girl reaches this landmark of puberty, the greater her chances of breast cancer later in life.
LENGTH: Medium: 58 linesby CNB