Cell lineage tracing links ERα loss in Erbb2-positive breast cancers to the arising of a highly aggressive breast cancer subtype

HER2-positive (HER2+) breast cancers (BrCs) contain approximately equal numbers of ERα+HER2+ and ERα-HER2+ cases. An enduring obstacle is the unclear cell lineage-related characteristics of these BrCs. Although ERα+HER2+ BrCs could lose ERα to become ERα-HER2+ BrCs, direct evidence is missing. To investigate ERα dependencies and their implications during BrC growth and metastasis, we generated ERαCreRFP-T mice that produce an RFP-marked ERα+...