Breast Cancer Stem Cells: Understanding and Opportunities for Therapeutics

Cancer stem cells (CSCs) are defined as rare immortal cell population within a tumor that can self-renew and give rise to several different cell types that establish the tumor and contribute to cancer therapy resistance. CSC follows asymmetric cell division that generates un-identical cell types during embryogenesis which ultimately helps these cells to maintain the homeostasis. The CSCs contribute to the development of tumor heterogeneity that is recognized by the existence of the diverse cell population within the tumor which poses a serious challenge for diagnosis and therapy. Breast cancer is one of the most heterogeneous tumors due to the high degree of diversity between and within tumors and a leading cause of cancer-related deaths in the women worldwide. Breast cancer stem cells (BCSCs) have been implicated in therapy resistance that significantly influences the overall clinical outcome of the breast cancer. The BCSCs phenotypes of tumors found to be unresponsive to chemotherapy and paclitaxel treatment. Interestingly these drugs induce the BCSCs phenotype in breast cancer cells in vitro. In addition, BCSCs escape chemotherapy and promote drug resistance by accumulate mutation, and accelerate self-renewal process after drug delivery[1]. Moreover, enhanced expression of CD44 /CD24-, a CSC marker were detected in primary tumors after chemotherapy[2]. Further, resistance to endocrine therapy was associated with elevated BCSCs[3]. In addition, the BCSCs were demonstrated to be resistance to radiotherapy in animal model[4]. Altogether, this evidence suggests that BCSC promotes therapy resistance, thus targeting this cancer cell population can be an effective therapeutic strategy for breast cancer treatment.