Artemisinin selectively decreases functional levels of estrogen receptor-alpha and ablates estrogen-induced proliferation in human breast cancer cells.
MCF7 cells are an estrogen-responsive human breast cancer cell line that expresses both estrogen receptor (ER) alpha and ERbeta. Treatment of MCF7 cells with artemisinin, an antimalarial phytochemical from the sweet wormwood plant, effectively blocked estrogen-stimulated cell cycle progression induced by either 17beta-estradiol (E(2)), an agonist for both ERs, or by propyl pyrazole triol (PPT), a selective ERalpha agonist. Artemisinin strongly downregulated ERalpha protein and transcripts without altering expression or activity of ERbeta. Transfection of MCF7 cells with ERalpha promoter-linked luciferase reporter plasmids revealed that the artemisinin downregulation of ERalpha promoter activity accounted for the loss of ERalpha expression. Artemisinin treatment ablated the estrogenic induction of endogenous progesterone receptor (PR) transcripts by either E(2) or PPT and inhibited the estrogenic stimulation of a luciferase reporter plasmid driven by consensus estrogen response elements (EREs). Chromatin immunoprecipitation assays revealed that artemisinin significantly downregulated the level of endogeneous ERalpha bound to the PR promoter, whereas the level of bound endogeneous ERbeta was not altered. Treatment of MCF7 cells with artemisinin and the pure antiestrogen fulvestrant resulted in a cooperative reduction of ERalpha protein levels and enhanced G(1) cell cycle arrest compared with the effects of either compound alone. Our results show that artemisinin switches proliferative human breast cancer cells from expressing a high ERalpha:ERbeta ratio to a condition in which ERbeta predominates, which parallels the physiological state linked to antiproliferative events in normal mammary epithelium.
Sundar
Shyam N
SN
Department of Molecular and Cell Biology and the Cancer Research Laboratory, University of California at Berkeley, Berkeley, CA 94720, USA.
Marconett
Crystal N
CN
Doan
Victor B
VB
Willoughby
Jamin A
JA
Firestone
Gary L
GL
D000970:Antineoplastic Agents / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D020847:Estrogen Receptor Modulators / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D047629:Estrogen Receptor beta / Q000096:biosynthesis / Q000187:drug effects; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D047468:Immunoprecipitation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis / Q000187:drug effects; D011980:Receptors, Progesterone / Q000187:drug effects / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects
D000970:Antineoplastic Agents; D037621:Artemisinins; D020847:Estrogen Receptor Modulators; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D004967:Estrogens; D012333:RNA, Messenger; D011980:Receptors, Progesterone; C031327:artemisinin
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