The idea of coupling Cre recombinase expression to that of the oncogene to circumvent this selection process was successfully demonstrated in the MMTV-NIC (Neu-IRES-Cre recombinase) model of ErbB2/Neu breast cancer, in which a mutant Neu transgene is linked to Cre recombinase through an internal ribosome entry sequence (IRES) [8]. This evidence concerns the gene ERBB2 and breast cancer.