Ligand-dependent induction of luciferase activity in breast cancer cells transfected with pSp13-luc was also induced by E2 and structurally-diverse estrogenic endocrine disruptors and responses varied with respect to ERα (wild = type/mutations) and expression of Sp1, Sp3 and Sp4 [60]. This evidence concerns the gene ESR1 and breast carcinoma.