Triple-negative breast cancer: molecular characteristics and potential therapeutic approaches

The term triple-negative breast cancer (TNBC) defines breast tumors that do not express estrogen receptors, progesterone receptor or epidermal growth factor receptor HER2 on immunohistochemical analysis. TNBC accounts for 12-17% of all types of breast cancer. Molecular profiling indicated that triple-negative breast cancer represents a heterogeneous subgroup of breast cancer. Triple-negative breast cancer shares histological and genetic abnormalities with basal-like subtype of breast cancer; however, this overlap is incomplete. Breast cancer found in BRCA1 mutation carriers is also frequently TNBC. Triple-negative breast cancer does not benefit from hormonal therapies or treatments targeted against HER2. The results of ongoing studies as well as the results of clinical trials suggest that poly(ADP-ribose) polymerase inhibitors, EGFR, Hedgehog, Notch, Wnt/beta-catenin, VEGF signaling inhibitors, and mTOR, Src, and Bcr/Abl kinase inhibitors used alone or in combination with other anticancer drugs might be effective in triple-negative breast cancer treatment. In this review, current knowledge on molecular characteristics of triple-negative breast cancer and its subtypes' treatment options is presented.