|
One mystery for breast cancer experts is why gene mutations that cause cancer when inherited don't seem to play a role in those that don't run in families. Now, scientists think a newly identified protein holds some of the answers. The discovery marks one of the first steps in dissecting the so-called BRCA pathway, which could shed light on certain cancers.
In the mid-1990s, researchers identified two genes that put women at high risk of breast and ovarian cancer. Inheriting the mutated genes, called BRCA1 and BRCA2, ratchets up cancer risk, but the genes haven't seemed important in nonheritable cancers. If mutated BRCA genes trigger cancer in women born with them, scientists wondered, why wouldn't they play a role in breast and ovarian cancer generally?
Cancer biologist Tony Kouzarides of Cancer Research UK and oncologists Luke Hughes-Davies and Carlos Caldas of the University of Cambridge tackled this question by starting with a small region of BRCA2. Members of a cancer-afflicted Scandinavian family lack this section of the gene, which is one of many mutations that can boost the risk of cancer. Kouzarides's group identified a protein that latched onto that region and named the protein EMSY (after Hughes-Davies's sister, an oncology nurse).
The team found that EMSY somehow affects the function of the BRCA2 gene, although the details aren't yet clear. When Kouzarides's group studied hundreds of tumor samples from sporadic cases, they found 1.5 to 4 times normal levels of EMSY in 13% of breast cancers and 17% of aggressive ovarian cancers. Almost no amplification of EMSY was found in other cancer cells they examined, such as those from colon tumors or sarcomas, the group reports in the 26 November issue of Cell.
EMSY "seems to be in the same pathway" as BRCA2, and the link is convincing, says Daniel Haber, director of the cancer center at Massachusetts General Hospital in Boston. Still, he cautions, "I don't think that EMSY by itself is going to explain all cases" of sporadic breast and ovarian cancer. Other genes and proteins, some unrelated to BRCA, may also be key, he says. Now, scientists just need to find them.
--JENNIFER COUZIN
Related sites
Science News article, "The Twists and Turns in BRCA's Path"
A nonprofit organization for BRCA carriers and families
National Alliance of Breast Cancer Organizations
Ovarian Cancer National Alliance
| 
