ESR1 and breast cancer: Indeed, when ChIA-PET was used to investigate the relationship between TFs mediated by hormones, namely the estrogen-receptor-alpha (ER-alpha), chromatin interactions and the transcriptome in the context of breast cancer, it was suggested that the coordinated regulation of sets of genes could be aided by their co-localization in space mediated by the RNA Polymerase II and that the perturbation of this arrangement can lead to transcriptional alterations of even secondary genes [199,221].