Myoepithelial cell perturbations in BRCA mutation carriers and in DCIS (ductal carcinoma in situ)

We describe the gene expression profiles and enhancer landscape of normal myoepithelial cells and perturbations of these in BRCA1 and BRCA2 mutation carriers and in DCIS. We identified a myoepithelial transcription regulatory network orchestrated by p63 and TCF7 and defined the genomic targets of these transcription factors by ChIP-seq. While the majority of myoepithelial cells co-express p63 and TCF7 in normal breast of healthy women, the frequency of these cells is significantly lower in BRCA1 mutation carriers and in DCIS. Downregulation of p63 in MCF10DCIS cells leads to loss of myoepithelial cells and invasive tumors, whereas overexpression of TCF7 enhances tumor growth. Our findings suggest that loss of normal myoepithelial cell function facilitates in situ to invasive carcinoma transition and it may also enhance tumor initiation in BRCA mutation carriers. Overall design: Normal myoepithelial cells and perturbations of these in BRCA1 and BRCA2 mutation carriers and in DCIS