Molecular Marker Predicts Breast Cancer Development

Women with proliferating cells within mammary epithelium cells significantly more likely to develop breast cancer.

A molecular marker found in normal breast tissue could predict the level of risk for women developing breast cancer, a recent study found.

Prior research has shown that women with BRCA1 or BRCA2 mutations were at a high risk of developing breast cancer. Additionally, women who did not have children before their 30s had a higher amount of mammary gland progenitor cells.

The current study, published in Cancer Research, examined biopsies taken from 302 participants, with some taken as many as 4 decades ago, who were diagnosed with benign breast disease.

Researchers compared the tissue of 233 women who did not end up developing cancer later on to 69 women who did.

The results of the study revealed that women with a higher percentage of Ki67, a molecular marker that identifies proliferating cells within the mammary epithelium cells, were 5 times more likely to develop cancer. These cells undergo drastic changes during a woman’s life, and is where a majority of breast cancer cells originate.

“Instead of only telling women that they don't have cancer, we could test the biopsies and tell women if they were at high risk or low risk for developing breast cancer in the future,” said senior co-author Kornelia Polyak, a Harvard Stem Cell Institute principle faculty member.

Although physicians currently test breast tumors for Ki67 levels, this is the first time researchers were able to link Ki67 to precancerous tissue and use it as a predictive tool.

“Currently, we are not able to do a very good job at distinguishing women at high and low risk of breast cancer,” said senior co-author Rulla Tamimi. “By identifying women at high risk of breast cancer, we can better develop individualized screening and also target risk reducing strategies.”

At this time, the best tool for early detection is mammograms, however, they do have some risks. False-positive, negative results, and over-diagnosis may lead to psychological distress, delayed treatment, or even overtreatment, according to the National Cancer Institute.

Although a single mammogram is unlikely to cause harm, repeated screens could potentially cause cancer due to machines using low dose radiation.

“If we can minimize unnecessary radiation for women at low risk, that would be good,” Tamimi said.

Researchers are looking to reproduce the results in an independent cohort of women, but they believe screening for Ki67 levels is something that could easily be applied to the current medical setting.