Letter

The future of mammary stem cell biology: the power of in vivo transplants

Geoffrey J Lindeman¹ , Jane E Visvader¹ , Matthew J Smalley² and Connie J Eaves³

¹VBCRC Laboratory, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria, Australia

²Breakthrough Toby Robins Breast Cancer Research Centre, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London, SW3 6JB, UK

³Terry Fox Laboratory, British Columbia Cancer Agency, 675 West 10th Avenue, Vancouver, British Columbia, V5Z 1L3, Canada

author email corresponding author email

Breast Cancer Research 2008, 10:402doi:10.1186/bcr1986

Published:	29 May 2008

See related letter by Smith and Medina, http://breast-cancer-research.com/content/10/3/403 and related review by Smith and Medina, http://breast-cancer-research.com/content/10/1/203

First paragraph (this article has no abstract)

The recent review by Smith and Medina [1] of in vivo transplantation models and their role in investigating mammary stem cell (MaSC) biology provides comprehensive coverage of the history and complexity of the 'gold standard' MaSC assay in mice. This includes a description of the pioneering studies that showed that mammary epithelial outgrowths can be generated in cleared mammary fat pads transplanted with explants or admixtures of mammary cells [2]. However, this approach clearly does not lend itself to prospective analysis of isolated subpopulations in order to identify which cells possess in vivo regenerative activity. More recently, success in obtaining complex mammary gland structures from transplanted suspensions of single cells has now made this possible [3-7]. Moreover, the regenerated structures have been shown to contain daughter cells with the same in vivo repopulating activity of the original stem cell transplanted [4,6]. A major contribution from this advance has been the demonstration that the MaSCs thus defined are highly enriched in the CD49f^hi/CD29^hi/CD24^+/mod/Sca-1^- subset [4-6]. Nevertheless, it is important to recognize that these stem cells represent under 10% of this basal population. This population also contains mature myoepithelial cells and, in all likelihood, other basal cell intermediates that are yet to be identified.