Causes of Triple-Negative Breast Cancer

Following a breast cancer diagnosis, doctors typically study the characteristics of the tumor in order to determine the best course of treatment. Among the medical tests performed on breast cancer tissue is screening for the presence of specific proteins on the surface of the cell, called receptors. These receptors allow the cancer cell to proliferate in response to certain factors, driving cancer growth. Many forms of breast cancer develop due to the presence of an estrogen receptor, progesterone receptor, or a protein called HER2--all of which drive cancer growth. Triple-negative breast cancer does not contain any of these proteins, and instead contains other proteins and gene mutations that cause cancer growth.

BRCA1 Mutations
Patients with triple-negative breast cancer often carry mutations to a gene called BRCA1. According to a study published in the "Journal of Clinical Oncology" in 2006, around 90 percent of women with BRCA1 mutations develop triple-negative breast cancer. BRCA1 acts as a tumor suppressor--when the gene is functional, it protects healthy cells from turning into cancer cells. Specifically, these genes play a role in preventing genetic mutations that drive cancer growth. Therefore, patients with dysfunctional BRCA genes are left vulnerable to cancer growth, and typically develop breast or ovarian cancer. Patients witha family history of breast cancer may undergo genetic testing to check for BRCA1 mutations, and may receive therapy to prevent the future development of breast cancer.

EGFR Overproduction
Another common cause of triple-negative breast cancer growth is the overproduction of a protein called EGFR. This protein is typically located on the surface of cancer cells, and responds to specific factors in the blood and tissue. When EGFR binds to specific factors, the protein becomes activated, and signals for the cancer cell to divide. When triple-negative breast cancer cells overproduce EGFR, the cancer cell always receives a signal to divide, and this constant division drives tumor growth. Dr. Lisa Carey, writing for "UBM Medica," indicates that inhibiting the function of EGFR in cancer cells may present a treatment option for triple-negative breast cancer.

Low 53BP1
Another cause of triple-negative breast cancer cell growth is the loss of a protein called 53BP1. This protein interacts with other factors within the cell that control cell growth. Under normal conditions, 53BP1 functions to maintain a cell growth arrest--it helps prevent the cell from dividing. In cancer development, a loss of 53BP1 allows the cell to constantly proliferate, and this proliferation eventually leads to tumor growth. A study published in "Nature Structure and Molecular Biology" in 2010 indicates that patients with triple-negative breast cancer typically have low levels of 53BP1 protein in their cancer cells. In the future, drugs that increase the amount of 52BP1 in cancer cells may eventually prove an effective therapy for triple-negative breast cancer.