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Updated: Aug 8, 2026

Mammosphere Assay Reveals Api5-Induced Stemness in Non-Tumorigenic Breast Epithelial Cell Lines
Published on: February 24, 2026
Mammary stem cells come of age, prospectively
1Laboratory of Mammary Biology and Tumorigenesis, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA. gs4d@nih.gov
Abstract:
Two recent reports have contributed direct evidence for the existence of a pluripotent mouse mammary epithelial stem cell. In both reports, the investigators have prospectively isolated an enriched fraction of mammary stem cells using fluorescence-activated cell sorting from freshly dispersed epithelial cells. This fraction of cells, upon transplantation in limiting dilution (in some cases as a single cell), produces complete mammary development within the host mammary fat pad. These studies extend and confirm earlier work that demonstrated that retroviral-tagged mammary fragments produce complete functional mammary glands comprising their clonal progeny upon fat-pad transplantation. This technical advance opens the possibility to use similar methodologies to isolate and characterize human breast epithelial stem cells, and elucidate their role in regeneration and neoplasia.
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Adult stem cells are tissue-specific; hence, they divide to develop the tissue from which they originate. One type of adult stem cell is the epithelial stem cell, which gives rise to the keratinocytes in the multiple layers of epithelial cells in the epidermis of the skin. Adult bone marrow has three distinct types of stem cells:...

