Researchers probe link between pregnancy, low breast cancer rates

CALGARY- Ashley Hart was just 24 years old and a month away from her wedding when she received some shocking news.

“I was diagnosed May 30, 2011,” she recalls. “The cancer was in my lymph nodes and I had the tumour in my breast.”

At the time, Hart couldn’t understand why she had cancer at such a young age, but genetic testing revealed she has the  BRCA-1 gene mutation.  Women with this mutation have a 45-90 per cent higher risk of developing breast cancer within their lifetime, and for Hart it meant her cancer would likely return.

“I got scared,” she admits. “They felt a little bit like ticking time bombs and so I didn’t feel like waiting.  I had already had cancer so in August 2012 I had a bilateral mastectomy.”

Right now, surgery is the best way for women with the BRCA gene mutations to cut their cancer risk, but that could soon change.

According to researchers at the Harvard Stem Cell Institute, women with BRCA mutations also have a high number of a mammary gland progenitor marker known as p27.

“These are cells that divide and maintain the milk duct epithelium,” Dr. Kornelia Polyak explains. “When you have to produce milk there’s a huge proliferation and these cells are the ones that divide and differentiate and it looks like the number remains low after pregnancy.”

As a result, women who have babies before the age of 25 have a low number of these cells, and are less likely to develop breast cancer.

Dr. Polyak’s team is now testing the tissues of thousands of women collected over a 20 year period to see how accurately the p27 markers are able to predict breast cancer. If the test proves accurate, the commercial development of a clinical test for breast cancer risk could follow within a few months.

At the same time, Dr. Polyak is testing a drug that appears to mimic the effect pregnancy has on the p27 mammary gland cells. The team’s ultimate goal is to see if this drug can be used to cut a woman’s risk of breast cancer.

“That’s what we would like to be able to test,” Polyak explains, “Right now, particularly for those high risk women, its only double mastectomy which is effective prevention, but if we could deplete these cells that would be another strategy.”