CD24 and breast cancer: Freshly isolated MMTV-PyMT Ccr6WT and Ccr6−/− mammary cells from pre-neoplastic mice at 8–9 weeks-old were assayed by flow cytometry for expression of cell surface markers CD24 and CD29 [32] (representative plots shown in Fig. 4a), which were previously used to define stem cells in the MMTV-PyMT [33, 34] and other breast cancer mouse models [35, 36].