Another Breast Cancer Gene ID'd
June 12, 2001 -- BRCA1 and BRCA2: In the world of breast cancer, these two genes have attained notoriety as the breast cancer susceptibility genes. That is, mutations in these two genes are known to increase disease risk. Now scientists have identified another "breast cancer gene," and it was found in a majority of the women studied.
In the June 13 issue of The Journal of the American Medical Association, California scientists report that a common form of the TGF-beta1 gene significantly increases breast cancer risk in older, white women.
The TGF-beta1 gene codes for a specific protein called transforming growth factor beta 1. When present in high amounts, this protein inhibits the growth of tumor cells. The scientists have identified different versions, or genotypes, of the gene. One genotype -- which happens to be the less common one -- is associated with a markedly reduced risk of breast cancer. The other genotype, however, leads to reduced production of the protein, thereby allowing tumor cells to grow unchecked.
"We have identified a gene that is associated with a reduced risk of breast cancer in older women. We understand a great deal about how the protein [works]," the senior study author Warren S. Browner, MD, MPH, tells WebMD. "If our results are confirmed by others, the next steps will be to develop treatments to mimic the action of that protein and to determine whether those treatments reduce the risk of breast cancer." Browner is scientific director of the Research Institute at California Pacific Medical Center and an adjunct professor of medicine and of epidemiology and biostatistics at the University of California, San Francisco.
According to the study, women with the T29 genotype have an increased risk of breast cancer. The findings, however, are limited to older, white women, as the researchers evaluated 3,000 white women over age 65. Nonetheless, the risk of breast cancer was two to three times higher in those women with T29.
"[This] study confirms a link between a very common ... alteration in the gene ... and the risk of breast cancer development in older women," Richard Press, MD, PhD, a pathologist at Oregon Health Sciences University in Portland, tells WebMD after reviewing the study.
About 85% of these women have the T29 alteration, Press explains.
So does this mean women will have an additional way to screen for breast cancer? Possibly, but not right away, according to breast cancer experts.
"Our study describes an interesting but preliminary finding," study author Elad Ziv, MD, a postdoctoral fellow in internal medicine at the Veterans Affairs Medical Center in San Francisco, tells WebMD. But not enough is known about this gene to recommend women be screened for it. In fact, scientists suspect that the T29 genotype is not the only factor triggering breast cancer in older women. Rather, they propose that several abnormal genes and environmental factors may be involved.