Breast cancer stem cells: are we ready to go from bench to bedside?

Since the discovery of breast cancer stem cells (BCSCs) more than 10 years ago, a body of exciting research has developed. The intrinsic properties of BCSCs, including self-renewal and the ability to give rise to heterogeneous progeny, make BCSCs a likely source of tumour initiation, heterogeneity, progression and metastasis. BCSCs are also inherently resistant to conventional therapies and are therefore thought to contribute to disease recurrence. In this review, we will focus on both the challenges and recent advances in the characterization of BCSCs with respect to phenotype, molecular signature and their role in the behaviour of the different molecular subtypes of breast cancer. Of most importance is our ability to translate our growing knowledge base into the development of targeted therapies with the goal of reducing adverse outcomes in breast cancer patients.