The role of breast cancer stem cells in chemoresistance and metastasis in triple‐negative breast cancer

Triple negative breast cancer (TNBC) remains an aggressive disease due to the lack of targeted therapies and relatively low rate of response to chemotherapy, which is currently the main treatment modality for TNBC. Breast cancer stem cells (BCSCs) are a small subpopulation of breast tumors and recognized as drivers of tumorigenesis. TNBC tumors are characterized as being enriched for BCSCs. Studies have demonstrated the role of BCSCs as the source of metastatic disease and chemoresistance in TNBC. Multiple targets against BCSCs are now under investigation, with the considerations of either selectively targeting BCSCs or co‐targeting BCSCs and non‐BCSCs (majority of tumor cells). This review article provides a comprehensive overview of recent advances in the role of BCSCs in TNBC and the identification of cancer stem cell biomarkers, paving the way for the development of new targeted therapies. The review also highlights the resultant discovery of cancer stem cell targets in TNBC and offers summaries of ongoing clinical trials treating chemo-resistant breast cancer. We aim to better understand the mutational landscape of BCSCs and explore potential molecular signaling pathways targeting BCSCs to overcome chemoresistance and prevent metastasis in TNBC, ultimately to improve the overall survival of patients with this devastating disease.