Artemisinin Disrupts Estrogen Receptor-Alpha and Cell Growth

Institution: University of California, Berkeley
Investigator(s): Gary Firestone, Ph.D. -
Award Cycle: 2006 (Cycle 12) Grant #: 12IB-0166 Award: $100,000
Award Type: IDEA
Research Priorities
Detection, Prognosis and Treatment>Innovative Treatment Modalities: search for a cure



Initial Award Abstract (2006)
A critical challenge in the treatment of breast cancer is the need to develop therapeutic agents that selectively inhibit growth of breast cancer cells with reduced side effects. There has been only a limited amount of research directed at the identification and characterization of natural ingredients in plants that can be used in breast cancer prevention and treatment. Natural plant compounds provide potential sources of new classes of chemotherapeutic agents to control breast cancer with reduced side effects. One such promising phytochemical is Artemisinin, a sesquiterpene lactone that was isolated from a Chinese plant Artemisia annua (commonly known as qinghaosu or sweet wormwood) and has been used as a Chinese herbal medicine for the last 2000 years to treat fever. Since the 1970s Artemisinin has been extensively as an anti-malaria drug that is effective against multi-drug resistant strains of malarial parasites. We have discovered a previously unknown property of Artemisinin in that treatment of human breast cancer cells with this plant compound disrupts estrogen responsiveness and stops cell growth, and we propose to understand the molecular mechanism of this process.

Artemisinin acts in breast cancer cells by inhibiting the production of the estrogen receptor-alpha (ERα) gene without altering the level of the related estrogen receptor-beta gene (ERα). Our hypothesis is that Artemisinin–regulated cellular pathways selectively inhibit the production of ERα and arrest the growth of estrogen responsive breast cancer cells by altering the function of nuclear cellular proteins (transcription factors) that are used by breast cancer cells to enhance the synthesis of the ERα gene.

We plan to use molecular and cellular approaches to identify the Artemisinin–regulated proteins from human breast cancer cells that alter the production of ERα, and thereby disrupt estrogen responsiveness and growth of human breast cancer cells. We will identify the region of the ERα gene promoter that is bound by Artemisinin responsive breast cancer cell nuclear proteins (called transcription factors) to control production of that gene. We also will assay Artemisinin–regulated changes in the ability of these transcription factors to bind to the ERα gene DNA in intact breast cancer cells. Breast cancercells will be generated in which the cellular production of the Artemisinin–regulated components will either disrupted or enhanced, and assess the subsequent effects on the Artemisinin–regulated ERα production and growth arrest.

Given the limited information about the role of Artemisinin–type compounds in the treatment of breast cancer, our study will provide the necessary first experimental information needed for a detailed understanding of how Artemisinin can disrupt estrogen responsiveness and growth of breast cancer cells.


Final Report (2008)
A critical challenge in the treatment of breast cancer is the need to develop therapeutic agents that selectively inhibit growth or induce apoptosis of breast cancer cells with reduced side effects. Natural plant compounds provide a potential source of such chemotherapeutic agents that act on various types of human breast cancers. One such promising natural compound is Artemisinin, a sesquiterpene lactone that was isolated from a Chinese plant Artemisia annua (commonly known as qinghaosu or sweet wormwood) that has been used by Chinese traditional medicine practitioners for at least two thousand years to treat fever and has been used since the 1970s as an effective anti-malaria drug.

We have discovered a previously unknown property of artemisinin in that treatment of estrogen responsive human breast cancer cell lines with this phytochemical induces a G1 cell cycle arrest that is accompanied with a disruption in estrogen responsiveness. We have observed that artemisinin strongly and selectively inhibits transcription of the estrogen receptor-alpha (ER-alpha) gene without any apparent effect on expression of its isoform estrogen receptor-beta (ER-beta). We hypothesize that artemisinin activated signaling pathways ablate ER-alpha mediated responsiveness and estrogen-dependent growth of breast cancer cells by selectively disrupting transcription factor function on the estrogen receptor-alpha promoter. By mutagenesis of the ER-alpha promoter, and analysis of transfected promoter-luciferase reporter plasmids, we have uncovered an artemisinin-regulated region of the ER-alpha that accounts for the artemisinin sensitivity of the estrogen receptor-alpha gene expression. As a functional test, we have demonstrated that artemisinin disrupts estrogen responsiveness and growth of human breast cancer cells, as well as demonstrated that artemisinin and anti-estrogens cooperatively inhibit growth of estrogen responsive breast cancer cells.

Our work shows that artemisinin switches highly proliferative human breast cancer cells from expressing a high ER-alpha:ER-beta ratio to a condition in which expression of ER-beta is significantly greatly to that of ER-alpha, which parallels the physiological state linked to anti-proliferative events in both normal mammary tissue and in breast cancer. Our results provide evidence for the new concept that the control of ER-alpha expression is an important and selective target of a subset of transcriptionally acting natural phytochemicals with potent anti-proliferative responses in human breast cancer cells. Therefore, our mechanistic studies directed at an understanding of the actions of artemisinin on estrogen receptor-alpha expression will provide valuable pre-clinical information in the development of artemisinin-based compounds for novel anti-breast cancer therapeutic strategies.


Symposium Abstract (2007)
MCF7 cells are an estrogen responsive human breast cancer cell line that expresses both estrogen receptor subtypes, estrogen receptor-alpha (ERα) and estrogen receptor-beta (ERβ). Treatment of MCF7 cells with artemisinin (Art), an anti-malarial phytochemical from the sweet wormwood plant, effectively blocked estrogen stimulated cell cycle progression induced by either β-estradiol (E2), an agonist for both estrogen receptor subtypes, or by propyl pyrazole triol (PPT), a selective ERα agonist. Art strongly down-regulated ERα protein and transcripts without altering expression or activity of ERβ. Transfection of MCF7 cells with ERα promoter-linked luciferase reporter plasmids revealed that the Art down-regulation of ERα promoter activity accounted for the loss of ERα expression. Furthermore, Art treatment ablated the estrogenic induction of endogenous progesterone receptor transcripts by either E2 or PPT, and inhibited the estrogenic stimulation of a luciferase reporter plasmid driven by consensus estrogen response elements (ERE). In vitro ERE binding assays revealed that Art treatment resulted in the loss of ERE bound ERα, whereas, the levels of ERE bound ERβ were not altered. Treatment of MCF7 cells with a combination of suboptimal combinations of Art and a pure antiestrogen, faslodex resulted in an enhanced reduction of ERα protein levels and in an enhanced G1 cell cycle arrest compared to the effects of either compound alone. Our results show that Art switches proliferative human breast cancer cells from expressing a high ERα:ERβ ratio to a condition in which expression of ERβ predominates, which parallels the physiological state linked to anti-proliferative events in both normal mammary epithelium and in breast cancer.


Artemisinin selectively decreases functional levels of estrogen receptor-alpha and ablates estrogen-induced proliferation in human breast cancer cells.
Periodical:Carcinogenesis
Index Medicus: Carcinogenesis
Authors: Sundar SN, Marconett CN, Doan VB, Willoughby JA Sr, Firestone GL
Yr: 2008 Vol: 29 Nbr: 122252-8 Abs: Pg: