title: Effects of S-equol and natural S-equol supplement (SE5-OH) on the growth of MCF-7 in vitro and as tumors implanted into ovariectomized athymic mice.
abstract: Hormone replacement therapy (HRT) for treatment of menopausal symptoms is controversial because of reported breast cancer resulting from estrogen treatment and consequent estrogenic stimulation. S-equol, a natural metabolite of the soy isoflavone daidzein produced by intestinal bacteria, has been shown to ameliorate menopausal symptoms, with relatively low concomitant estrogenic receptor stimulation. Although synthesis of equol produces the racemate, the S-isomer may be produced in commercial amounts by bacterial fermentation of soy germ, during the production of the supplement SE5-OH. This study aims to investigate the effects of S-equol and SE5-OH on the growth of MCF-7 in vitro and in vivo. In vitro, purified S-equol, and the isoflavonoid mixture present in SE5-OH stimulated estrogenic transcriptional activity and proliferation of MCF-7-E10 cells, similar to that observed for genistein (another soy isoflavone), but at concentrations from 10(4)-fold to 10(6)-fold higher than seen with 17β-estradiol (E2). Ovariectomized (OVX) mice implanted with MCF-7-E10 cells were fed diets containing 250 or 500 ppm of purified S-equol, isoflavonoid mixture, or genistein. There were no significant differences in tumor growth between the treatment groups and control group. These results suggest that S-equol and natural S-equol in the supplement (SE5-OH), do not promote the progression of breast cancer.
authors.affiliation: Saga Nutraceuticals Research Institute, Otsuka Pharmaceutical Co., Ltd., 5006-5 Yoshinogari-cho, Kanzaki-gun, Saga 842-0195, Japan. a_onoda@research.otsuka.co.jp
authors.forename: Atsuko
authors.initials: A
authors.lastname: Onoda
authors.forename: Tomomi
authors.initials: T
authors.lastname: Ueno
authors.forename: Shigeto
authors.initials: S
authors.lastname: Uchiyama
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Hayashi
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Kato
authors.forename: Norio
authors.initials: N
authors.lastname: Wake
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D060754:Equol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010052:Ovariectomy; D011960:Receptors, Estrogen / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology; D023041:Xenograft Model Antitumor Assays
chemical_list: D011960:Receptors, Estrogen; D060754:Equol