To examine whether microRNAs differentially regulated through morphogenesis are also deregulated in cancer, we examined miRNA expression in four mouse tumour models compared to normal total mammary epithelium: spontaneous Tp53−/− tumours [34], transgenic C3 SV40 tag model [35], transgenic MMTV-Neu [36] and transgenic MMTV-PyMT [37]. Here, ERBB2 is linked to neoplasm.