(R)-Equol

(R)-Equol is an agonist of both ERα and ERβ with Kis of 27.4 and 15.4 nM, respectively.

Signaling Pathways >> Others >> Estrogen Receptor/ERR

Research Areas >> Cancer

Ki: 27.4 nM (ERα), 15.4 nM (ERβ)[1]

(R)-Equol is an agonist of both ERα and ERβ with Kis of 27.4 and 15.4 nM, respectively[1]. (R)-Equol induces a dose-dependent inhibitory effect on the invasive capacity of MDA-MB-231 cells that is significant at the highest concentration tested (50 μM). Following 48-h exposure to (R)-Equol, invasion is reduced by 62% (p=0.009, versus untreated cells) with 50 μM (R)-Equol. Matrix metalloproteinase-2 (MMP-2) expression is significantly down-regulated following treatment with 50 μM (R)-Equol (p=0.035)[2].

Animals fed (R)-Equol have a significantly reduced number of palpable tumors over time when compare with Controls (P=0.002). Furthermore, the number of palpable tumors formed per rat in the (R)-Equol-fed group is significantly lower than that of rats treated with S-(-)equol (P=0.008). (R)-Equol-fed animals have 43% fewer tumors than the control group and this difference is highly statistically significant (P=0.004). The number of tumors/tumor-bearing animal is significantly lower in the animals fed (R)-Equol compare with Controls (3.3±0.4 versus 5.5±0.5, P=0.004). At necropsy, the mean (±SEM) tumor weight per animal for (R)-Equol fed rats (5.3±1.1 mg) is significantly reduced (P=0.04) when compare with Controls (9.9±1.4 mg). Feeding the (R)-Equol diet results in significantly increased tumor latency (P=0.003)[3].

Cell viability is determined using the well-established MTT assay. Cells are seeded (1.25×105 cells/mL) in 96-well plates in experimental medium (100 μL/well) and incubated for 48 h at 37°C in a 95 % air/5 % CO2 humidified atmosphere. Medium is then replaced with fresh medium containing (R)-Equol (R-equol) (2.5, 10 or 50 μM) or DMSO only as a control. Following 48-h incubation, cell viability is assessed[2].

To investigate the chemopreventive effects of dietary (R)-Equol against chemically induced mammary cancer, female Sprague-Dawley rats bred in-house are fed a soy-free AIN-93G diet from birth to 35 days of age, then separated into different groups. Group 1 (Control group, n=40) continues on this diet, whereas the other group of animals are fed the AIN-93G diet supplemented with 250 mg/kg of (R)-Equol (Group 3, n=41) beginning on day 35 until killing on day 190[3].

[1]. Setchell KD, et al. S-equol, a potent ligand for estrogen receptor beta, is the exclusive enantiomeric form of the soy isoflavone metabolite produced by human intestinal bacterial flora. Am J Clin Nutr. 2005 May;81(5):1072-9.

[2]. Magee PJ, et al. Daidzein, R-(+)equol and S-(-)equol inhibit the invasion of MDA-MB-231 breast cancer cells potentially via the down-regulation of matrix metalloproteinase-2. Eur J Nutr. 2014 Feb;53(1):345-50.

[3]. Brown NM, et al. The chemopreventive action of equol enantiomers in a chemically induced animal model of breast cancer. Carcinogenesis. 2010 May;31(5):886-93.

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