ERBB2 and breast cancer: We have used the MMTV-NIC (Neu-IRES-Cre) model (Ursini-Siegel et al., 2008), which employs a bicistronic transcript to co-express activated ErbB2/Neu (HER2) with MMTV-Cre recombinase, resulting in the formation of activated ErbB2/Neu-driven mammary tumours.