Triple-Negative Breast Cancer

From an interview with Milan Radovich, Ph.D., Assistant Professor of Surgery, IU School of Medicin

Triple-negative breast cancer is an especially aggressive form of breast cancer.  “Triple-negative” is a term many have heard, but few lay people really know what it is, or what it means to have this type of the disease.  Fifteen percent of all breast cancers diagnosed in the U.S. are triple-negative; pre-menopausal women and women of African descent tend to be more commonly diagnosed with this form.

To understand what triple-negative means, one must first understand that cells have receptors on their surfaces.  Receptors are like molecular “antennae” which receive signals from outside of the cells.  Most breast cancers in the U.S. (75%) overexpress the estrogen and progesterone receptors. In addition to chemotherapy, these patients receive hormone therapy drugs like Tamoxifen and aromatase inhibitors to target these receptors. Triple-negative breast cancers have no estrogen or progesterone receptors, meaning there are no benefits from taking these drugs. This lack of estrogen and progesterone receptors are the first and second “negatives”.  Another type of breast cancer is called “HER2 positive”. HER2 is a protein called “human epidermal growth factor receptor 2”, and in about 30% of breast cancers this protein is overexpressed, causing HER2-positive breast cancer.  HER2-positive is an aggressive breast cancer, but there are some very effective treatments that target it.  The lack of overexpressed HER2 protein removes another treatment target, creating a third negative.  “Triple-negative” means none of the receptors are over-producing, limiting the treatment options and translating to a poorer overall survival rate.

Africans who develop breast cancer are more than likely to have triple-negative disease. There is a suggested genetic component to this, but no one knows what this might be. A major advantage of the planned KTB tissue collection in Kenya is that acquiring tissue from an African nation would help expand the diversity of the normal tissue held in the Bank, which in turn increases the availability of tissue most likely to be used in research projects focused on finding a cause and cure for triple-negative disease.

Black American women are primarily a genetic mixture of African and Caucasian genes, while Kenyans are tribal.  The KTB samples taken from Kenyans will be classified by tribe, which will hopefully help identify distinct genetic populations. Genetics are more homogeneous within tribes. When the tissue is compared to non-African tissue, we will gain more ability to identify the differences.  This will assist in finding the “needle in a haystack” with respect to the genetic composition that predisposes women to develop triple-negative breast cancer.

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