The mammosphere platform was employed to assess the potential of denosumab as an anti-CSC agent not only in BRCA1 haploinsufficient cells but also in genetically diverse breast cancer subtypes in which CSC-like states are known to be driven by molecular traits such as epithelial-to-mesenchymal transition (EMT) or HER2-oncogene overexpression (22–30). The gene discussed is ERBB2; the disease is breast cancer.