Abstract
Mammary stem cells (MaSCs) contribute to mammary epithelium development and homeostasis. They have been proposed as cells of origin for breast cancer. Here, we describe an organoid culture protocol for ex vivo expansion of MaSCs from mouse tissues. These organoids maintain the self-renewal of gland-reconstituting MaSCs and can be used to model tumorigenesis by introducing patient-relevant cancer drivers and mutations. Similar organoid culture can be used for long-term expansion of luminal stem/progenitor cells from normal glands and tumor-initiating cells from mammary tumors. For complete details on the use and execution of this protocol, please refer to Christin et al. (2020) and Zhang et al. (2016).