Mammary Stem Cells: Premise, Properties, and Perspectives

Adult mammary stem cells (MaSCs) drive postnatal organogenesis and remodeling in the mammary gland, and their longevity and potential have important implications for breast cancer. However, despite intense investigation the identity, location, and differentiation potential of MaSCs remain subject to deliberation. The application of genetic lineage-tracing models, combined with quantitative 3D imaging and biophysical methods, has provided new insights into the mammary epithelial hierarchy that challenge classical definitions of MaSC potency and behaviors. We review here recent advances - discussing fundamental unresolved properties of MaSC potency, dynamics, and plasticity - and point to evolving technologies that promise to shed new light on this intractable debate. Elucidation of the physiological mammary differentiation hierarchy is paramount to understanding the complex heterogeneous breast cancer landscape.his work was supported by the Medical Research Council ( MR/J001023/1 to C.J.W. and B.L-L.), the Wellcome Trust ( 105377/Z/14/Z to O.B.H.), the National Health and Medical Research Council ( 1071074 to F.M.D.), and a University of Queensland Early Career Researcher Grant ( UQECR1718865 to F.M.D.)