A Genetic System for Identification of Mammary Stem Cells
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: It has been proposed that mammary stem cells or cells with similar properties to mammary stem cells contribute to breast cancer. These so called mammary “cancer stem cells” have been speculated to be quiescent or possess drug efflux pumps, which would make them resist to commonly used chemotherapeutic agents. Thus, current treatments might temporarily reduce tumor bulk, but leave dormant cancer stem cells to regenerate the tumor upon their reentry into the cell cycle. If this hypothesis is correct, identifying cancer stem cells may allow earlier detection, more accurate prognoses, and development of potentially curative therapies. However, current technology and strategies yield mammary stem cells that are not sufficiently pure to enable their characterization. To overcome this obstacle, we developed a novel genetic approach to enable rapid characterization of mammary stem cells using signaling pathways these cells likely require. Successful completion of the project would enable functional identification of stem cells in the normal mouse mammary gland and mouse models of breast cancer.
 
 
 
 
 
 
 
 My first aim is to gain a better understanding of the developmental pathways involved in mammary development, and to localize the cells in which these pathways are active. It was previously demonstrated that Wnt signaling is critical for mammary development. Wnt proteins comprise a family of highly conserved secreted molecules that regulate proliferation, maintenance of stem cells, and many other functions. Therefore, I will characterize the expression of Wnt signaling pathway components during mammary development by analyzing the expression of several Wnt target genes. I will also study p63 (a member of the p53 tumor suppressor family), integrins (cell adhesion proteins), and other proteins thought to be important for mammary formation. I will perform these analyses using immunochemical techniques. To test whether Wnt signaling is involved in mammary stem cell function, we developed a genetic strategy using live cell fluorescence with a Wnt-inducible gene promoter to track, purify, and characterize individual cells in mouse embryos and adults. This system enables us to determine whether the cells with active Wnt signaling are dividing or are quiescent. Importantly, if the stem cells are not in cycle, our genetic strategy will enable us to identify and isolate them and to then test whether particular growth pathways affect their functionality using transplantation assays.
 
 
 
 
 
 
 
 Existing studies of mammary and other tissue stem cells have used isolation techniques that rely on the expression of proteins (CD markers) on the surface of the cells. Using this technique, it has taken 20 years to purify blood stem cells to a level of only about 50%, while that of mammary stem cells is only 2-5%. Such a low level of purity makes it difficult to pinpoint the identity of mammary stem cells, as their unique features are masked by the contaminating cells. We hope that our new mouse model-based technology will ultimately be translated into useful human, clinical applications by definitively determining whether mammary stem cells or cells with similar properties contribute to breast tumorigenesis.