Characterization of MCF7-ERβ cell lines. (A) Western blot (WB) analysis demonstrating expression of ERβ in three independent clonal MCF7 cell lines. (B) Immunoflourescence depicting nuclear localization of ERβ protein in stably expressing MCF7 cell lines. (C) Luciferase assays demonstrating transcriptional activation of a transiently transfected ERE by either ERα or ERβ in parental and MCF7-ERβ cell lines using estrogen, the ERα specific agonist PPT or the ERβ specific agonist DPN. * denotes significance at the P < 0.05 level (ANOVA) compared with vehicle controls while # denotes significance for a given treatment between the two cell lines.