ERBB2 and cancer: To exclude the possibility of subtype-specific effects, we also used a hormone receptor–positive (HR+) orthotopic MCF-7 cancer model in NOD/SCID mice and a human epidermal growth factor receptor 2–enriched (HER2-enriched), transgenic, spontaneous mouse mammary tumor virus–polyoma middle T antigen (MMTV-PyMT) mouse model on FVB/NJ background (20, 21).