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International Journal of Cell Biology
Volume 2011, Article ID 451676, 11 pages
Review Article

The Mammary Gland Microenvironment Directs Progenitor Cell Fate In Vivo

Mammary Biology and Tumorigenesis Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA

Received 14 January 2011; Accepted 11 March 2011

Academic Editor: Michael Hortsch

Copyright © 2011 Karen M. Bussard and Gilbert H. Smith. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The mammary gland is a unique organ that continually undergoes postnatal developmental changes. In mice, the mammary gland is formed via signals from terminal end buds, which direct ductal growth and elongation. Intriguingly, it is likely that the entire cellular repertoire of the mammary gland is formed from a single antecedent cell. Furthermore, in order to produce progeny of varied lineages (e.g., luminal and myoepithelial cells), signals from the local tissue microenvironment influence mammary stem/progenitor cell fate. Data have shown that cells from the mammary gland microenvironment reprogram adult somatic cells from other organs (testes, nerve) into cells that produce milk and express mammary epithelial cell proteins. Similar results were found for human tumorigenic epithelial carcinoma cells. Presently, it is unclear how the deterministic power of the mammary gland microenvironment controls epithelial cell fate. Regardless, signals generated by the microenvironment have a profound influence on progenitor cell differentiation in vivo.