Testing tumors for the breast cancer gene BRCA1 could be a powerful way of predicting how patients will respond to chemotherapy, scientists from Breast Cancer Campaign and Cancer Research UK report.

The BRCA1 gene plays an important role in stopping cancer developing, and women who inherit a damaged version of the gene have a high risk of developing breast cancer. BRCA1 may also get switched off in as many as 30 percent of tumors, even in patients who inherited a normal version of the gene.

Now researchers have found that tumor cells react differently to chemotherapy depending on how well BRCA1 is working within them. The findings could yield a new test to help doctors decide which treatment to use on breast cancer patients, and the researchers will soon put the results to test as part of a patient trial.

The main researchers on the project were Dr. Jennifer Quinn, Dr. Paul Harkin and Dr. Richard Kennedy, all based at the Cancer Research Centre, Queen's University Belfast.

The research team found that a functional BRCA1 gene made breast cancer cells 10 to 1,000 times more resistant to one type of drug that works by damaging DNA within cancer cells.

In contrast, functional BRCA1 made cells over 1,000 times more sensitive to a second type of drug that works by blocking cell division.

These results suggest that testing tumors to find out if BRCA1 is working properly could help doctors decide which type of chemotherapy treatment to use. Cancers in which BRCA1 is working properly may be treated more successfully by drugs blocking cell division. And cancers in which BRCA1 is faulty or has ceased to work properly could be better treated with drugs that damage cancer cell DNA.

Targeting chemotherapy in this way could make the treatment more effective and reduce its side effects, and could be particularly important for those patients who inherit a defective copy of BRCA1.

Cancer Research UK's Dr. Paul Harkin, the senior researcher on the study, says: "Our results were quite dramatic. Essentially, cancer cells with functional BRCA1 are highly resistant to one type of chemotherapy but extremely sensitive to another.

"For scientists like myself it's very exciting, because knowing a tumor's BRCA1 status may be invaluable in deciding which type of chemotherapy to use."

Fellow researcher Dr. Jennifer Quinn, of Breast Cancer Campaign, says: "Breast cancers can differ greatly from one woman to the next, so finding ways of matching a treatment to a patient is one of the key areas of current research.

"Our study is part of a movement towards a new approach to breast cancer, in which women will be treated on the basis of information gathered about their individual tumors."

SOURCE:
Cancer Research UK (http://www.cancerresearchuk.org)