ERBB2 and breast cancer: To determine whether it was technically feasible to activate or to delete genes in a tamoxifen-inducible and Cre-mediated manner in mammary cancers, we generated parous female mice that carried the MMTV-neu oncogene in addition to the MMTV-Flp Rosa26CAG-FSF-CreERT2 CAG-LSL-GFP transgenes.