MCF7/RFP cells are derived from the human breast cancer cell line MCF7 by stably integration of a constitutive RFP stably expression construct. MCF7 cells are estrogen receptor-positive (ER+), making them a valuable model for studying hormone-dependent breast cancers and testing estrogen-related therapies. MCF7/RFP cells stably stably express RFP, can be used for in vitro assays and in vivo imaging.