Hops (Humulus lupulus) Inhibits Oxidative Estrogen Metabolism and Estrogen-Induced Malignant Transformation in Human Mammary Epithelial cells (MCF-10A)

Abstract

Long-term exposure to estrogens including those in traditional hormone replacement therapy (HRT) increases the risk of developing hormone-dependent cancers. As a result, women are turning to over-the-counter (OTC) botanical dietary supplements such as black cohosh (Cimicifuga racemosa) and hops (Humulus lupulus) as natural alternatives to HRT. The two major mechanisms which likely contribute to estrogen and/or HRT cancer risk are: the estrogen receptor (ER) mediated hormonal pathway; and, the chemical carcinogenesis pathway involving formation of estrogen quinones that damage DNA and proteins, hence initiating and promoting carcinogenesis. Since OTC botanical HRT alternatives are in widespread use they may have the potential for chemopreventive effects on estrogen carcinogenic pathways in vivo. Therefore the effect of OTC botanicals on estrogen-induced malignant transformation of MCF-10A cells was studied. Cytochrome P450 catalyzed hydroxylation of estradiol at the 4-position leads to an o-quinone believed to act as the proximal carcinogen. LC-MS/MS analysis of estradiol metabolites showed that 4-hydroxylation was inhibited by hops, whereas black cohosh was without effect. Estrogen-induced expression of CYP450 1B1 and CYP450 1A1 was attenuated by the hops extract. Two phenolic constituents of hops (xanthohumol, XH; and 8-prenylnaringenin, 8-PN) were tested: 8-PN was a potent inhibitor whereas XH had no effect. Finally, estrogen-induced malignant transformation of MCF-10A cells was observed to be significantly inhibited by hops (5 μg/mL) and 8-PN (50 nM). These data suggest that hops extracts possess cancer chemopreventive activity through attenuation of estrogen metabolism mediated by 8-PN.

Differential Gene Regulation and Tumor-Inhibitory Activities of Alpha-, Delta-, and Gamma-Tocopherols in Estrogen-Mediated Mammary Carcinogenesis

“…Recent studies shed light on the role of natural products in the inhibition of estrogen dependent breast cancer (5,6). Dietary components and bioactive natural compounds have been reported to inhibit mammary carcinogenesis by reduction of estrogen-induced oxidative stress as well as downregulation of ER-mediated signaling (7).…”

SERMs Attenuate Estrogen-Induced Malignant Transformation of Human Mammary Epithelial Cells by Upregulating Detoxification of Oxidative Metabolites

“…MCF-10A cells were obtained from American Type Culture Collection (Manassas, VA) and maintained in phenol red and estrogen-free Dulbecco's modified Eagle's medium and F12 medium (DMEM/F12) supplemented with 1% penicillin-streptomycin, 5% fetal bovine serum, cholera toxin (0.1 μg/mL), epidermal growth factor (20 ng/mL), hydrocortisone (0.5 μg/mL), insulin (10 μg/L) and 5% CO 2 at 37 °C as described previously (27). MCF-10A cells were authenticated using single tandem repeat analysis (STR).…”

“…Estrogen metabolites were analyzed in MCF-10A cell as previously described (27). Briefly, MCF-10A cells were incubated with E 2 (1 μM) in the presence or absence of SERMs (1 μM) for 6 days.…”

“…Since, DMA and Ral showed a significant inhibition of estrogen metabolism at 1 μM in MCF-10A cells, a dose response was performed for these two SERMs: DMA and Ral (0.1 - 2.5 μM) were tested in the presence of E 2 (1 μM). Sample preparation and analysis was done using the method described by Xu et al (30) with minor modifications as previously described (27). Enzymatic hydrolysis of cell media was done as previously described (30) with minor modifications.…”

Looking Forward to 2013—Saluting the Exceptional Year in 2012

“…We featured natural agentrelated studies, including several early-phase clinical trials and provocative preclinical articles, such as a study from the Karen Liby group of a triterpenoid in delaying the development of mammary cancer in mutant BRCA1 mice (16). Highlighting the diversity of prevention work published this past year in CaPR, other provocative primary reports include one on the effects of modifying gut microbiotica to prevent viral hepatitis and liver cancer (17), another on hops extracts to prevent mammary cancer (18), and one on pathway activation mapping and networks analyses in human skin premalignancy progression (19).…”