ID4 and neoplasm: qrtPCR analysis of the tumours was carried out using a panel of genes associated with the three main mammary epithelial cell lineages (basal: Fzd7, Id4, Jag1, Jag2, Krt14, Krt15, Notch4, Runx2 and Tp63; luminal ER negative: Foxc1 and Sox6; luminal ER positive: Esr1, Foxa1 and Msx2; and both luminal populations: Cd24a, Notch1, Notch2, Notch3 and Krt18) [15] and with NOTCH signalling (Dtx1, Fabp7, Fbxw7, Jag1, Jag2, Hes1, Hes2, Heyl, Notch1-4 and Nrarp).