New Approaches for the Treatment of Triple Negative Breast Cancer

Abstract

Triple‐negative breast cancer (TNBC) is the most refractory subtype of breast cancer to current treatments and accounts disproportionately for the majority of breast cancer‐related deaths. Research has not yet identified specific therapies for TNBC and chemotherapy remains the conventional therapy in the clinic. While conventional chemotherapy regimens have demonstrated success at reducing bulk tumor burden, they have been shown to enrich cancer stem cells (CSCs). CSCs promote chemoresistance, metastasis, heterogeneous tumor regeneration and disease relapse. Owing to tumor plasticity and the conversion between CSC and non-CSC subpopulations development of a strategy capable of inhibiting both non-CSC and CSC subpopulations is crucial for TNBC therapy. In this compilation of my main research projects, several new approaches for the treatment of TNBC were identified which target not only the bulk tumor population but also the CSC populations residing within the tumor: 1. Co-suppression of Wnt, HDAC, and ESR1 using clinically relevant low‐dose inhibitors effectively repressed both bulk and CSC subpopulations and converted CSCs to non‐CSCs in TNBC cells. 2. Co-inhibition of mTORC1, HDAC, and ESR1 was capable of reducing both bulk and CSC subpopulations as well as the conversion of fractionated non-CSC to CSCs in in a human TNBC xenograft model and hampered tumorigenesis following treatment. 3. Inhibition of Wnt and YAP retarded tumor growth of TNBC cells in either epithelial or mesenchymal states, and both CD44high/CD24low and ALDH+ CSC subpopulations were diminished in a human xenograft model reducing tumorigenicity following treatment.