Since PRLR and EGFR are expressed in breast tumors and STAT5 was found essential for unliganded ERα dimer association with the complex at the PRLR promoter [13, 19], we envisioned commonalities in the mechanism that participate in the E2/ERα induction of PRLR gene transcription/expression to that observed for PRL and EGF in MCF-7 cells. Here, ESR1 is linked to breast neoplasm.