In addition, we have reported that a fragment of this region [potentially regulated by the intense trafficking of the receptors (26–28)] possesses specific activities, including pro-estrogenic (25), pro-apoptotic (29) actions, while it modulates the migratory activity of human breast cancer cells in vitro (30), interacting with specific isoforms of ERα (31). The gene discussed is ESR1; the disease is breast carcinoma.