en ايمونولوژي Immunology پژوهشي Research <p><strong>Background: </strong>Phytoestrogens, a group of plant-derived polyphenolic compounds have recently come into considerable attention due to the increasing information on their potential adverse effects in human health<strong>. </strong>Some of<strong>&nbsp;</strong>phytoestrogens show estrogenic activity that may be carcinogenic for human. In the present study, we investigated the transcriptional effects of variety of phytoestrogens<strong>&nbsp;</strong>on the bovine oxytocin and the thymidine kinase-ERE promoter by estrogen receptor &alpha; in MDA-MB 231 breast cancer cell line.</p> <p><strong>Materials and Methods: </strong>Cells were seeded for transfections into 12- well plates at a density of 100000 cells per well were transfected with a total of 3 &mu;g of plasmid DNA using calcium phosphate coprecipitation. Estrogen and some phytoestrogens (naringenin, 8-prenyl-naringenin and 6-( 1, 1 - dimethylallyl ) naringenin were used for the stimulation of transfected cells.</p> <p><strong>Results: </strong>Findings of our study clearly demonstrated the subtype-selective activation of estrogen receptor (ER)&alpha; and (ER)&beta; by the p hytoestrogen naringenin (activating estrogen receptor &beta;) and its substituted forms 8-prenyl-naringenin and 6-( 1, 1 - dimethylallyl ) naringenin (activating estrogen receptor &alpha;) , on the ERE-controlled promoter as well as on the oxytocin gene promoter.</p> <p><strong>Conclusion: </strong>The study revealed that some p hytoestrogen s show estrogenic activity by classical or non-classical mechanisms as well as exhibit estrogenic activity by undetermined mechanisms in transfected MDA-MB 231 cell line.</p> <p></p> Phytoestrogens, Naringenin, Oxytocin, Transfection 28 35 http://rmm.mazums.ac.ir/browse.php?a_code=A-10-615-6&slc_lang=en&sid=1 Ehsan Zayerzadeh 10031947532846006101 10031947532846006101 Yes Department of Biology, Faculty of Food Industry and Agriculture, Standard Research Institute, Karaj, Iran. Mohammad Kazem Koohi 10031947532846006102 10031947532846006102 No Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. Azadeh Fardipour mkkoohi@ut.ac.ir 10031947532846006103 10031947532846006103 No Department of Quality Control, Razi Vaccine and Serum Research Institute, Karaj, Iran