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Characterization of Human Mammary Epithelial Stem Cells

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Annual summary 15 Sep 2006-14 Sep 2010

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The mammary epithelium of normal adult female mice contains stem cells with extensive in vivo regenerative and self-renewal potential. Indirect evidence has suggested that analogous cells exist in the mammary glands of adult women, and are candidate targets for the first transforming mutations that lead to the evolution of breast cancer stem cells. The objective of this grant was to determine whether these hypothesized normal human mammary stem cells might be detected and quantified by a robust and specific assay that could be used to enable the purification and phenotypic properties of these cells, and to derive information about their frequency and how they are regulated. During the 3 years of this grant plus 1 year extension, I established conditions that allow human mammary gland structures to be reproducibly generated in subrenal xenografts in highly immunodeficient mice, starting with small innocula of dissociated human mammary cells. The regenerated glands are similar in morphology and cellular organization to normal human mammary glands, bounded by a basement membrane with an outer layer of myo-epithelial cells and an inner layer of polarized luminal cells that can be induced to produce milk. I also established that the presence of regenerated structures can be determined by detecting the in vitro clonogenic progenitors they contain and this endpoint can serve as an objective indicator of the presence of a primitive stem-like cell in the initial cells transplanted. This retrospective functional assay allows limiting dilution analysis of positive xenograft yields to derive mammary stem cell frequencies in differently manipulated populations. Using this approach I found the frequency of stem cells in normal human mammary tissue to be 1 per 5000 cells and their phenotype to be CD49f EpCAM-low CD31- CD45-.

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  • Anatomy and Physiology
  • Medicine and Medical Research

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