New Estrogenic Prenylflavone from Epimedium brevicornum Inhibits the Growth of Breast Cancer Cells

Abstract

Estrogens maintain female sexual health. The hormone also drives the growth of estrogen receptor (ER) positive breast tumors, and ER modulators, like tamoxifen, are used to reduce tumor recurrence. To identify phytoestrogens with possible health benefits, we screened several Traditional Chinese Medicines and encountered an extract from the leaves of Epimedium brevicornum (EB), with strong (EC₅₀ : 1.3 μg/mL) and specific ER-stimulatory activity. It increased estrogen-responsive human breast cancer cell proliferation at low doses, but paradoxically caused profound inhibition of growth at higher doses. Using bioassay-guided fractionation, we isolated and characterized a new prenylflavone, breviflavone B, which exerted biphasic stimulatory and inhibitory effects on breast cancer cell proliferation, mimicking the effects of EB. In contrast to estradiol and genistein, high doses (> 2 μM) of breviflavone B almost eliminated ERα protein; a process that may be mediated through increased proteasome degradation. Pre-clinical studies are needed to explore whether these prenylflavones are of value in estrogen-deficiency states and for prophylaxis of breast cancer.

Key words

Epimedium brevicornum - Berberidaceae - prenylflavone - estrogen - receptor - anti-proliferation - breast - cancer

References

• 1 Cos P, De Bruyne T, Apers S, Vanden Berghe D, Pieters L, Vlietinck A J. Phytoestrogens: recent developments.  Planta Medica. 2003;  69 589-99
• 2 Hoffmann J, Bohlmann R, Heinrich N, Hofmeister H, Kroll J, Kunzer H. et al . Characterization of new estrogen receptor destabilizing compounds: effects on estrogen-sensitive and tamoxifen-resistant breast cancer.  J Natl Cancer Inst. 2004;  96 210-8
• 3 Tham D M, Gardner C D, Haskell W L. Potential health benefits of dietary phytoestrogens: a review of the clinical, epidemiological, and mechanistic evidence.  J Clin Endocrinol Metab. 1996;  83 2223-35
• 4 Pharmacopoeia of the People’s Republic of C hina. Pharmacopoeia Commission of PRC, English edition. Vol I Beijing; Chemical Industry Press 1997: pp 93-4
• 5 Wu H, Lien E J, Lien L L. Chemical and pharmacological investigations of Epimedium species: a survey.  Progress in Drug Research. 2003;  60 1-57
• 6 Chen C C, Huang Y L, Sun C M, Shen C C. New prenylflavones from the leaves of Epimedium sagittatum .  J Nat Prod. 1996;  59 412-4
• 7 Lee M K, Choi Y J, Sung S H, Shin D I, Kim J W, Kim Y C. Antihepatotoxic activity of icariin, a major constituent of Epimedium koreanum .  Planta Medica. 1995;  61 523-6
• 8 Chen K M, Ge B F, Ma H P, Zheng R L. The serum of rats administered flavonoid extract from Epimedium sagittatum but not the extract itself enhances the development of rat calvarial osteoblast-like cells in vitro .  Pharmazie. 2004;  59 61-4
• 9 Kuroda M, Mimaki Y, Sashida Y, Umegaki E, Yamazaki M, Chiba K. et al . Flavonol glycosides from Epimedium sagittatum and their neurite outgrowth activity on PC12 hcells.  Planta Medica. 2000;  66 575-7
• 10 Lin C C, Ng L T, Hsu F F, Shieh D E, Chiang L C. Cytotoxic effects of Coptis chinensis and Epimedium sagittatum extracts and their major constituents (berberine, coptisine and icariin) on hepatoma and leukaemia cell growth.  Clin Exp Pharmacol Physiol. 2004;  31 65-9
• 11 Liang H R, Vuorela P, Vuorela H, Hiltunen R. Isolation and immunomodulatory effect of flavonol glycosides from Epimedium hunanense .  Planta Medica. 1997;  63 316-9
• 12 Ngan F, Shaw P, But P, Wang J. Molecular authentication of Panax species.  Phytochemistry. 1999;  50 787-91
• 13 Loy C J, Sim K S, Yong E L. Filamin-A localizes to the nucleus to regulate androgen receptor and coactivator functions.  Proc Natl Acad Sci USA. 2003;  100 4562-67
• 14 ang Q, Lu J, Yong E L. Ligand- and coactivator-mediated transactivation function (AF2) of the androgen receptor ligand-binding domain is inhibited by the cognate hinge region.  J Biol Chem. 2001;  276 7493-9
• 15 Li W K, Xiao P G, Zhang R Y. A difuranoflavone from Epimedium koreanum .  Phytochemistry. 1995;  38 807-8
• 16 Sigstad E, Catalan C, Diaz J, Herz W. Chromanones, benzofurans and other constituents from Ophryosporus lorentzii .  Phytochemistry. 1996;  42 1443-5
• 17 Kitaoka M, Kadokawa H, Sugano M, Ichikawa K, Taki M, Takaishi S. et al . Prenylflavonoids: a new class of non-steroidal phytoestrogen (Part 1). Isolation of 8-isopentenylnaringenin and an initial study on its structure-activity relationship.  Planta Medica. 1998;  64 511-5
• 18 Milligan S R, Kalita J C, Pocock V, Van De Kauter V, Stevens J F, Deinzer M L. et al . The endocrine activities of 8-prenylnaringenin and related hop (Humulus lupulus L.) flavonoids.  J Clin Endocrinol Metab. 2000;  85 4912-5
• 19 Schaefer O, Humpel M, Fritzemeier K H, Bohlmann R, Schleuning W D. 8-Prenyl naringenin is a potent ERalpha selective phytoestrogen present in hops and beer.  J Steroid Biochem Mol Biol. 2003;  84 359-60
• 20 Ruh M F, Zacharewski T, Connor K, Howell J, Chen I, Safe S. Naringenin: a weakly estrogenic bioflavonoid that exhibits antiestrogenic activity.  Biochem Pharmacol. 1995;  50 1485-93
• 21 Wijayaratne A L, McDonnell D P. The human estrogen receptor-alpha is a ubiquitinated protein whose stability is affected differentially by agonists, antagonists, and selective estrogen receptor modulators.  J Biol Chem. 2001;  276 35 684-92