This has permitted targeting of breast cancer mutations, such as deletion of key tumour suppressors BRCA1, BRCA2, p53 and PTEN, specifically to the mouse mammary epithelium to provide models for the human disease (Jonkers et al., 2001; Diaz-Cruz et al., 2010; Melchor et al., 2014). This evidence concerns the gene BRCA1 and breast carcinoma.