ERBB2 and breast cancer: To evaluate the role of MDA-7/IL-24 in breast cancer in immune-competent mice and to gain a further understanding of the mechanism of action of MDA-7/IL-24 in breast cancer, we performed in vivo experiments using three transgenic models - MMTV-PyMT mice, MMTV-MDA-7 mice and MMTV-MDA-7/MMTV-Erbb2 mice.