MDA-MB-231/RFP-Luciferase cells are derived from the human breast cancer cell line MDA-MB-231 by stably integration of a constitutive RFP-Firefly luciferase stably expression construct. MDA-MB-231 cells are high invasive and able to metastasize. MDA-MB-231 cells are classified as triple-negative breast cancer cells, meaning they do not express estrogen receptors (ER), progesterone receptors (PR), or HER2, which makes them a valuable model for studying this challenging subtype of breast cancer. MDA-MB-231/RFP-Luciferase cells stably stably express RFP and Firefly luciferase, can be used for in vitro assays and in vivo imaging.