ESR1 and cancer: The observed hypomethylation in the far upstream region of BRCA1 (green squares for BRCA1_1 in Figure 1A) was found mainly in estrogen receptor negative tumours like the basal-like tumours further supporting the hypothesis that the genome-wide hypomethylation observed in breast cancer (as well as in any other cancer types) might be more pronounced in this tumour subclass.