title: Determination of the differential estrogenicity of isoflavonoids by E2-ER-ERE-dependent gene expression in recombinant yeast and MCF-7 human breast cancer cells.
abstract: The use of phytoestrogens-containing natural sources as alternative hormone replacement therapy (HRT) has been a subject of debate for decades. Development of assays to characterize these phytoestrogens is required. In this study, differential estrogenicities of five isoflavonoids found in red clover and soy, including biochanin A, daidzein, formononetin, genistein and glycitein were examined in a yeast-based screen system with a classical palindromic estrogen response element (ERE)-ADE2 reporter and in a MCF-7 cell culture system with mRNA levels of ER-dependent genes compared. In a yeast-based assay, five isoflavonoids showed various extents of estrogenic potencies. A collection of primary estrogen receptor (ER)-regulated genes by estradiol (E2), including hTERT, c-MYC, BCL2 and Ha-ras (oncogenic) and quinone reductase (QR), human complement 3 (C3) and COX7RP (non-oncogenic) were selected as marker genes for a MCF-7 cell-based endogenous gene expression assay. The results indicated that the mRNA levels of these E2-ER-ERE-dependent marker genes were regulated differentially by five isoflavonoids, leading to distinct expression patterns, which are also significantly different from that of E2. Moreover, the anti-estrogenic effects of biochanin A and formononetin on E2-induced transcriptions of marker genes in MCF-7 cells were also displayed. Taken together, these results are significant for these naturally occurring isoflavonoids regarding the issues of safety and efficacy.
authors.affiliation: Department of Food Science, China Institute of Technology, Taipei 115, Taiwan.
authors.forename: Chuan-Chuan
authors.initials: CC
authors.lastname: Lin
authors.affiliation: Department of Microbiology, College of Medicine, National Taiwan University, No. 1, Sec. 1, Jen-Ai Road, Taipei 100, Taiwan.
authors.forename: Yun-Luen
authors.initials: YL
authors.lastname: Tsai
authors.affiliation: Department of Food Science, Cook College, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901-8520, USA.
authors.forename: Chi-Tang
authors.initials: CT
authors.lastname: Ho
authors.affiliation: Department of Microbiology, College of Medicine, National Taiwan University, No. 1, Sec. 1, Jen-Ai Road, Taipei 100, Taiwan; Institute of Internal Medicine, National Taiwan University Hospital, Taipei 100, Taiwan. Electronic address: shuchunteng@ntu.edu.tw.
authors.forename: Shu-Chun
authors.initials: SC
authors.lastname: Teng
keywords: Estrogen receptor; Estrogen response element; Estrogenicity; Isoflavaonoid; Oncogene