phytoestrogens and flavone

Phytoestrogens have a controversial effect on hormone-dependent tumours. Herein, we investigated the effect of the pumpkin seed extract (PSE) on estradiol production and estrogen receptor (ER)-α/ER-β/progesterone receptor (PR) status on MCF7, Jeg3, and BeWo cells. The PSE was prepared and analyzed by mass spectrometry. MCF7, Jeg3, and BeWo cells were incubated with various concentrations of PSE. Untreated cells served as controls. Supernatants were tested for estradiol production with an ELISA method. Furthermore, the effect of the PSE on ER-α/ER-β/PR expression was assessed by immunocytochemistry. The PSE was found to contain both lignans and flavones. Estradiol production was elevated in MCF7, BeWo, and Jeg3 cells in a concentration-dependent manner. In MCF7 cells, a significant ER-α downregulation and a significant PR upregulation were observed. The above results after properly designed animal studies could highlight a potential role of pumpkin seed's lignans in breast cancer prevention and/or treatment.

Topics: Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cucurbita; Down-Regulation; Estradiol; Estrogen Receptor alpha; Estrogen Receptor beta; Female; Flavones; Humans; Immunohistochemistry; Lignans; MCF-7 Cells; Phytoestrogens; Plant Extracts; Receptors, Progesterone; Seeds; Trophoblastic Neoplasms; Up-Regulation

The androgen receptor (AR) plays a critical role in prostate cancer development and progression. This study aimed to use a computerized docking approach to examine the interactions between the human AR and phyto-oestrogens (genistein, daidzein, and flavone) and xeno-oestrogens (bisphenol A, 4-nonylphenol, dichlorodiphenyl trichloroethane [DDT], diethylstilbestrol [DES]). The predicted three-dimensional structure of AR and androgens was established using X-ray diffraction. The binding of four xeno-oestrogens and three phyto-oestrogens to AR was analysed. The steroids estradiol and dihydrotestosterone (DHT) were used as positive controls and thyroxine as negative control. All the ligands shared the same binding site except for thyroxine. The endogenous hormones DHT and 17beta-oestradiol showed the strongest binding with the lowest affinity energy (< -10 kcal mol(-1)). All three phyto-oestrogens and two xeno-oestrogens (bisphenol A and DES) showed strong binding to AR. The affinities of flavone, genistein, and daidzein were between -8.8 and -8.5 kcal mol(-1), while that of bisphenol A was -8.1 kcal mol(-1) and DES -8.3 kcal mol(-1). Another two xeno-oestrogens, 4-nonylphenol and DDT, although they fit within the binding domain of AR, showed weak affinity (-6.4 and -6.7 kcal mol(-1), respectively). The phyto-oestrogens genistein, daidzein and flavone, and the xeno-oestrogens bisphenol A and DES can be regarded as androgenic effectors. The xeno-oestrogens DDT and 4-nonylphenol bind only weakly to AR.

Topics: Benzhydryl Compounds; Computer Simulation; DDT; Diethylstilbestrol; Flavones; Genistein; Humans; Isoflavones; Ligands; Phenols; Phytoestrogens; Receptors, Androgen

While estrogen-related receptors (ERRalpha, ERRbeta, and ERRgamma) share a high amino acid sequence homology with estrogen receptors (ERs), estrogens are not ligands of ERRs. Structure-function studies from this and other laboratories have revealed that ERRs have small ligand-binding pockets and have provided evidence to show that these receptors can activate gene transcription in a constitutive manner. To address the question as to whether there is any agonist for ERRs, our laboratory recently performed virtual ligand screening on ERRalpha that predicted flavone and isoflavone phytoestrogens to be ligands of this receptor. Our mammalian cell transfection and mammalian two-hybrid experiments revealed that three isoflavones (genistein, daidzein, and biochanin A) and one flavone (6,3',4'-trihydroxyflavone) behaved as agonists of ERRs. These phytoestrogens induced the activity of ERRalpha at concentrations that are comparable to those for the activation of ERalpha and ERbeta. In this study, we also used the results of ERRalpha ligand-binding site mutant, F232A, to verify our ERRalpha hypothetical computer model. Our recent ERR research has determined for the first time that flavone and isoflavone phytoestrogens are agonists of ERRs. In addition, our studies have demonstrated that an approach that combines structure-based virtual screening and receptor functional assays can identify novel ligands of orphan nuclear receptors.

Topics: Binding, Competitive; Computer Simulation; Databases, Factual; ERRalpha Estrogen-Related Receptor; Flavones; Flavonoids; Genistein; HeLa Cells; Humans; Isoflavones; Ligands; Luciferases; Models, Molecular; Molecular Structure; Phytoestrogens; Plant Preparations; Receptors, Cytoplasmic and Nuclear; Receptors, Estrogen; Recombinant Fusion Proteins; Structure-Activity Relationship; Transfection