Six more genes tied to breast cancer

THEY BELIEVE they may have found a complex genetic pathway that causes cancer in many families, and hope their finding may help identify people most at risk, and perhaps lead to the development of targeted drugs to treat them.

Dr. Alan D’Andrea of the Dana-Farber Cancer Institute and Harvard Medical School in Boston had been studying Fanconi anemia, an inherited disorder that causes bone marrow failure in children.

Patients develop anemia and bone marrow failure by the age of 5, and if they survive, often develop cancer later on.

Last year D’Andrea’s international team reported they had linked six genes associated with Fanconi anemia with the BRCA1 breast cancer gene, and this week they report in the journal Science that they have made a link with BRCA2 as well. They also showed the eight genes interact.

“By studying a rare disease we have unexpectedly identified these six cancer genes and demonstrated that they are directly related to BRCA1 and BRCA2, the major breast cancer susceptibility genes,” D’Andrea said in a telephone interview.

“Now that we know these eight genes cooperate in a common cellular pathway, we can begin to study them systematically.”

GENETIC RISKS

Women with mutations in BRCA1 have about a 50 percent risk of getting cancer sometime in their lifetimes. BRCA1 and BRCA2 gene mutations account for between 4 percent and 10 percent of all cases of breast and ovarian cancer.

D’Andrea’s team found the six Fanconi anemia genes help control BRCA1 and BRCA2. Five of them work together to make an enzyme that is supposed to help repair damaged DNA, but which is faulty in people with two “bad” copies of the genes.

The six genes may be involved in the many cases of inherited breast cancer that cannot be blamed on faulty BRCA1 and BRCA2, D’Andrea said.

“Just as women today can be tested for BRCA1 and BRCA2 mutations to determine if they have an inherited predisposition for breast cancer, testing for mutations in these other six genes may soon become a routine part of gauging inherited breast cancer risk,” he said.

“Women and their doctors can then use the information in deciding how to keep that risk at a minimum.”

D’Andrea said his team stumbled on the association.

Doctors checking into the genetic causes of a rare children's cancer syndrome said on Thursday they had shown a cluster of six genes lies behind not only the childhood cancer, but many cases of breast cancer.

“When we looked at breast cancer cells from a woman under a microscope, we found a striking resemblance to Fanconi anemia cells we had been studying,” he said.

“The chromosomes of the cells were broken in a characteristic manner. Based on that similarity, we were motivated to look at the BRCA2 gene.”