BRCA1 and breast cancer: Gene array analysis of these cell lines indicated that genes associated with mammary luminal progenitor cells are enriched in the luminal Py230 MaCSC line compared with the claudin-low MaCSC line Py16-1 (Figure S4A, D, see Additional file 5), in concordance with data that Brca1-deficient mammary tumors also arise from luminal progenitor cells [34].