Breast cancer stem cells: Potential therapeutic targets

Recent results have increased our understanding of normal stem cells and the signalling pathways that regulate them during the development of the mammary gland. Tumours in many tissues are now thought to develop from dysregulated stem or progenitor cells that may be recognised by cell surface protein expression or patterns of biological behaviour such as dye efflux or the capacity to grow as tumours in vivo or spheres in vitro. Many stem cell pathways are dysregulated in cancers, including the Notch signalling pathway, which is involved in the development of the breast and is aberrantly activated in invasive and pre-invasive breast cancers. Recent studies have shown a connection with increased levels of Notch pathway activation and enrichment for breast CSCs, and stem cell self-renewal pathways such as Notch may represent novel therapeutic targets in both pre-invasive and invasive breast cancer.