ERBB2 and breast carcinoma: More recently, we established a unique transgenic mouse model of ErbB2-driven breast cancer in which mammary epithelial expression of ErbB2/Neu is coupled to the Cre recombinase using an intervening internal ribosome entry site (IRES) element neu-ires-cre (NIC; Ursini-Siegel et al., 2008).