In normal and cancer breast epithelial cells, we can find no evidence for E2-induced nuclear co-localisation between the heterologous or homologous alleles of TFF1 and GREB1 (Figure 1, Figure 2, Figure 3, and Figure 5) or indeed for any allele combination of another pair of ERα-regulated genes, PGR and CTSD located in cis on the same chromosome as each other (Figure 4). Here, CTSD is linked to cancer.