NEW DATA ON BREAST CANCER GENE
by Sean Henahan, Access Excellence
NASHVILLE- The BRCA1 gene, previously implicated in the
development of rare familial forms of breast cancer, also
appears to play a role in much more common types of
non-inherited breast cancers, report researchers from Vanderbilt
University Medical Center
The discovery last year of the location of the BRCA1 gene was
the culmination of a furious competition by more than a dozen
laboratories around the world. However, mutations in this gene
were reported to be associated with only some five percent of
The new study indicates that BRCA1 is involved in the
development of sporadic breast cancers in a way that does not
involve mutations of the gene. The researchers found BRCA1's
normal function is to slow cell growth, and that less BRCA1 is
expressed in non-familial types. This could be a vital clue,
since cancer is a process of unchecked cell growth.
"BRCA1 is not just associated with hereditary breast
cancer. This is important because the inherited form of breast
cancer accounts for fewer than 5 percent of all breast cancer
cases. In cancer genetics, you can find hereditary cancer genes.
Then you hope that the same genes are involved in the more common
sporadic cancer, said Dr. Jeffrey T. Holt, associate professor of
Cell Biology and Pathology, Vanderbilt University.
Dr. Holt and colleagues had previously developed a new method
for isolating breast cells (normal, precancerous and cancerous)
from connective and other tissue. This led to the development of
permanent genetic libraries which were used in the present
The researchers found that expression of the BRCA1 gene was
decreased up to tenfold in invasive breast cancers compared to
normal tissue. To test the hypothesis that expression of BRCA1
inhibits cell growth, the researchers manipulated both normal and
cancerous breast cells so there would be no BRCA1 being
expressed. Stopping BRCA1 in breast cells made them grow faster,
BRCA1 proved to be very stable in the normal cell samples.
They level of the gene expression was found to be increased in
precancerous cells. This supports the hypothesis that the breast
cells' movement toward cancer triggers BRCA1 to become more
active as a way to inhibit cell growth. BRCA1 levels then
decrease as the cells become cancerous, allowing cell growth to
progress unchecked. Why this happens is unknown at present
"This paper provides the first hard evidence as to what the
function of BRCA1 may be, and it makes sense with our finding that it is decreased in invasive lesions," said Dr. Roy A. Jensen, assistant professor of Pathology and Cell Biology at Vanderbilt.
BRCA1 is proving to be a very complicated gene, with a great
many mutations, and
developing a screening test for it will be very challenging, Holt
said. However, the latest evidence from this and other studies
suggests that the BRCA1 gene may play a role in the future
diagnosis and treatment of not only inherited breast and ovarian
cancer but also the much more common sporadic forms, Holt said.
The current research appears in the April issue of the
journal Nature Genetics.
BRCA1 also appears to be involved in the development of
ovarian cancer. Another study reported in the same issue of
Nature Genetics concluded that BRCA1 was flawed in at least 10
percent of sporadic cases of ovarian cancer.
Breast cancer is the most common cancer among women and the
second leading cause of death from cancer in women (after lung
cancer). The average woman in the U.S. has a one in nine chance
of developing breast cancer by the age of 85. Ovarian cancer
accounts for five percent of cancers among women.
Transmitted: 95-04-04 20:26:43 EDT
Related information at other Web sites
Breast Cancer Links from CNN
The University of Pennsylvania's Oncolink directory on Breast Cancer