Induction of Estrogen Receptor-α and -β Activities by Selective Estrogen Receptor Modifiers

Objective:To investigate the induction of estr ogen receptor(ER)-α and -β activities by selective estrogen receptor modifie rs (SERMs). Methods:Breast cancer cell lines MDA-MB 231 were transf ected with the vector expressing ERα, β(pSVhER α/β) in combination with a lu ciferase reporter gene vector(ER-Etk-Luc). The transfected cells were separate ly treated with estrogen and several SERMs at a dose of 1 nmol·L -1 for 2 4 hours. To assess the luciferase expression in cells transfected with ERα or β, the commercially available luciferase reporter gene assay was used. Results:ERα activities were strikingly up-regulated in the presence of raloxifen, 4OH-tamoxifen and tamoxifen citrate as 17β estradi ol, while ERβ activities were much more weakly induced in the presence of ralox ifen, 4OH-tamoxifen and tamoxifen citrate. Conclusion:Our results indicate that the antiestrogenic activity of SERMs is brought about chiefly via upregulation of estrogen receptor -α while the estrogen β receptor was induced only to a much lessor extent.