Data from Enrichment of a Population of Mammary Gland Cells that Form Mammospheres and Have <i>In vivo</i> Repopulating Activity

The identification of mammary gland stem cells (MGSC) or progenitors is important for the study of normal breast development and tumorigenesis. Based on their immunophenotype, we have isolated a population of mouse mammary gland cells that are capable of forming “mammospheres” in vitro. Importantly, mammospheres are enriched for cells that regenerate an entire mammary gland on implantation into a mammary fat pad. We also undertook cytogenetic analyses of mammosphere-forming cells after prolonged culture, which provided preliminary insight into the genomic stability of these cells. Our identification of new cell surface markers for enriching mammosphere-initiating cells, including endoglin and prion protein, will facilitate the elucidation of the cell biology of MGSC. [Cancer Res 2007;67(17):8131–8]