4T1/Cre cells are derived from the mouse mammary carcinoma 4T1 cell line by stably integration of a constitutive Cre recombinase stably expression construct. The 4T1 mammary carcinoma is a transplantable tumor cell line that is highly tumorigenic and invasive and, unlike most tumor models, can spontaneously metastasize from the primary tumor in the mammary gland to multiple distant sites including lymph nodes, blood, liver, lung, brain, and bone. 4T1 cell line has been widely used in cancer research and drug development. 4T1/Cre cells stably express a nuclear localized Cre recombinase.