title: Mammary gland stem cells: more puzzles than explanations.
abstract: Mammary gland stem cells (MaSC) have not been identified in spite of extensive research spanning over several decades. This has been primarily due to the complexity of mammary gland structure and its development, cell heterogeneity in the mammary gland and the insufficient knowledge about MaSC markers. At present, Lin (-) CD29 (i) CD49f (i) CD24 (+/mod) Sca- 1 (-) cells of the mammary  gland have been reported to be enriched with MaSCs. We suggest that the inclusion of stem cell markers like Oct4, Sox2,  Nanog and the mammary gland differentiation marker BRCA-1 may further narrow down the search for MaSCs. In addition, we have discussed some of the other unresolved puzzles on the mammary gland stem cells, such as their similarities and/or differences with mammary cancer stem cells, use of milk as source of mammary stem cells and the possibility of in vitro differentiation of embryonic stem (ES) cells into functional mammary gland structures in this review. Nevertheless, it is the lack of identity for a MaSC that is curtailing the advances in some of the above and other related areas.
authors.affiliation: CSIR - Centre for Cellular and Molecular Biology, Uppal Road, Habsiguda, Hyderabad 500 007, India.
authors.forename: Suneesh
authors.initials: S
authors.lastname: Kaimala
authors.forename: Swathi
authors.initials: S
authors.lastname: Bisana
authors.forename: Satish
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D006801:Humans; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000378:metabolism; D042361:Mammary Glands, Human / Q000166:cytology* / Q000378:metabolism*; D051379:Mice; D014411:Neoplastic Stem Cells / Q000166:cytology / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*