(-)-Epigallocatechin-3-gallate downregulates estrogen receptor alpha function in MCF-7 breast carcinoma cells.
BACKGROUND
(-)-Epigallocatechin-3-gallate (EGCG) is the most active catechin present in green tea, demonstrated to have chemopreventive action and to kill cancer cells selectively. As a previous study found that catechins could compete with 17-beta-estradiol for binding to estrogen receptor alpha (ERalpha), we asked whether EGCG could regulate ERalpha action.


METHODS
We used MCF-7, a breast carcinoma cell line having a high level of ERalpha expression. The cells were treated with various EGCG concentrations and cell viability was evaluated by MTT assay. ERalpha and pS2 expression were analyzed by RT-PCR after RNA extraction. To better define EGCG action in relation to ERalpha, we studied EGCG cytotoxicity on MCF-7 resistant to tamoxifen (MCF-7tam), MCF-7 treated with 10(-7)M ICI 182,780 for 8 days and on MDA-MB-231, a cell line that lacked ERalpha by flow cytometry (FCM).


RESULTS
Both ERalpha and pS2 mRNA were expressed in samples treated with low EGCG concentration (30 microg/ml). At this concentration, no cell change was detectable. In contrast, pS2 expression was lost in samples treated with 100 microg/ml EGCG for 24h, indicating ERalpha alteration. EGCG cytotoxicity was lower when ERalpha was not present (MDA-MB-231) or inactivated (by tamoxifen or ICI 182,780).


CONCLUSIONS
Functionally active ERalpha may have a role in EGCG cytotoxicity, increasing the sensitivity to the drug. As higher EGCG concentrations also killed cells resistant to tamoxifen or treated by 10(-7)M ICI 182,780, EGCG ought to be better investigated in breast carcinoma cells treated with drugs targeted to steroid receptors, as a potential complement of therapy.
Farabegoli
Fulvia
F
Department of Experimental Pathology, University of Bologna, V.S. Giacomo 14, 40126 Bologna, Italy. fulvia.farabegoli@unibo.it
Barbi
Cristiana
C
Lambertini
Elisabetta
E
Piva
Roberta
R
D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D005260:Female; D006801:Humans; D013629:Tamoxifen / Q000494:pharmacology; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D016588:Anticarcinogenic Agents; D047628:Estrogen Receptor alpha; C051838:TFF1 protein, human; D000071163:Trefoil Factor-1; D025521:Tumor Suppressor Proteins; D013629:Tamoxifen; D002392:Catechin; C045651:epigallocatechin gallate