In the field of estrogen-responsive BC being ERα the master regulator of estrogen signaling including a dense network of cointeractors, many proteomic studies have been carried out with the aim of identifying novel ERα-partners involved in the molecular bases of BC progression and to discover novel biomarkers and putative pharmacological targets [11,73,85,86,87,88,89]. The gene discussed is ESR1; the disease is breast cancer.