Novel Method Enables Isolation of Nearly Pure Population of Mammary Gland Stem Cells

The surface protein marker CD1d is highly expressed on mammary gland stem cells (MaSCs), and the presence of this protein was used in a novel method to isolate a remarkably pure MaSC population.

CD1d is a member of the CD1 (cluster of differentiation 1) family of glycoproteins expressed on the surface of various human antigen-presenting cells. They are nonclassical major histocompatibility complex (MHC) proteins, related to the class I MHC proteins, and are involved in the presentation of lipid antigens to T-cells.

The partial purification of mouse MaSCs using a combination of cell surface markers has improved understanding of their role in normal development and breast tumorigenesis. However, despite the significant improvement in techniques for MaSC enrichment, there is presently no methodology that adequately isolates pure MaSCs.

To correct this lack, investigators at Cold Spring Harbor Laboratory (NY, USA) utilized the fact that MaSCs replicate very slowly to develop a method for their purification based on incorporation of a green fluorescent protein into the nuclei of various mammary cells including MaSCs. Since MaSCs replicate less often than other cell types, they retain more of the green fluorescent protein and can be isolated by cell sorting techniques that recognize CD1d.

The investigators reported in the April 11, 2013, online edition of the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) that working with a remarkably pure MaSC population, they were able to functionally characterize a set of MaSC-enriched genes and discovered factors controlling MaSC survival.

"With this advancement, we are now able to profile normal and cancer stem cells at a very high degree of purity, and perhaps point out which genes should be investigated as the next breast cancer drug targets," said senior author Dr. Gregory Hannon, professor of molecular biology at Cold Spring Harbor Laboratory.

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