Although not all tumors from TG-Ren.713 mice showed mKate2/GFP expression due to an incomplete overlap of expression between the MMTV and WAP promoters, this novel multi-allelic system has proven a powerful platform for the study of tumor suppressor gene function in the context of HER2-driven breast cancer (SHE and SWL, unpublished data). Here, ERBB2 is linked to breast carcinoma.