stilbenes and afimoxifene

Estrogen therapy was used to treat advanced breast cancer in postmenopausal women for decades until the introduction of tamoxifen. Resistance to long-term estrogen deprivation (LTED) with tamoxifen and aromatase inhibitors used as a treatment of breast cancer inevitably occurs, but unexpectedly low-dose estrogen can cause regression of breast cancer and increase disease-free survival in some patients. This therapeutic effect is attributed to estrogen-induced apoptosis in LTED breast cancer. Here, we describe modulation of the estrogen receptor (ER) liganded with antiestrogens (endoxifen and 4-hydroxytamoxifen) and an estrogenic triphenylethylene (TPE), ethoxytriphenylethylene (EtOXTPE), on estrogen-induced apoptosis in LTED breast cancer cells. Our results show that the angular TPE estrogen (EtOXTPE) is able to induce the ER-mediated apoptosis only at a later time compared with planar estradiol in these cells. Using real-time polymerase chain reaction, chromatin immunoprecipitation, western blotting, molecular modeling, and X-ray crystallography techniques, we report novel conformations of the ER complex with an angular estrogen EtOXTPE and endoxifen. We propose that alteration of the conformation of the ER complexes, with changes in coactivator binding, governs estrogen-induced apoptosis through the protein kinase regulated by RNA-like endoplasmic reticulum kinase sensor system to trigger an unfolded protein response.

Topics: Breast Neoplasms; Cell Proliferation; Cell Survival; Crystallography, X-Ray; Female; Gene Expression Regulation, Neoplastic; Humans; MCF-7 Cells; Receptors, Estrogen; Stilbenes; Tamoxifen

Breast cancer is the second most common cancer and a leading cause of cancer death in women. Specifically, estrogen receptor-α (ERα)-negative breast cancers are clinically more aggressive and normally do not respond to conventional hormone-directed therapies such as tamoxifen. Although epigenetic-based therapies such as 5-aza-2'-deoxycytidine and/or trichostatin A as DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors, respectively, can regulate the expression of ERα, this can often lead to a number of side effects. Plant-based dietary compounds such as resveratrol and pterostilbene in novel combinatorial therapy provides new avenues to target these side effects and provide similar results with a higher level of safety. Here, we report that combinatorial resveratrol and pterostilbene leads to the reactivation of ERα expression in ERα-negative breast cancer cells in a time-dependent manner. Chromatin immunoprecipitation analysis of the ERα promoter in each cell type revealed an increase in enrichment of acetyl-H3, acetyl-H3lysine9 (H3K9) and acetyl-H4 active chromatin markers in the ERα promoter region after combinatorial treatment. This treatment also resulted in a significant change in HDAC and histone acetyl transferase (HAT) enzyme activity in these cells after 3 days of treatments. The combination resulted in a significant decrease in DNMT enzyme activity and 5-methylcytosine levels in MDA-MB-157 breast cancer cells. Moreover, reactivation of ERα expression by resveratrol combined with pterostilbene was found to sensitize ERα-dependent response to 17β-estradiol (E2)-mediated cellular proliferation and antagonist 4-hydroxytamoxifen (4-OHT)-mediated inhibition of cellular proliferation in ERα-negative breast cancer cells. E2 and 4-OHT further affected the ERα-responsive downstream progesterone receptor (PGR) gene in ERα reactivated MDA-MB-157 cells. Collectively, our findings provide a new and safer way of restoring ERα expression by regulating epigenetic mechanisms with the use of phytochemicals in combinatorial therapy. This combination can further provide effective treatment options for hormonal refractory breast cancer with available anti-hormonal therapy.

Topics: Breast Neoplasms; Cell Line, Tumor; DNA Methylation; Epigenesis, Genetic; Estrogen Receptor alpha; Female; Humans; Promoter Regions, Genetic; Resveratrol; Stilbenes; Tamoxifen

Resveratrol, a naturally occurring stilbene, has been categorized as a phytoestrogen due to its ability to compete with natural estrogens for binding to estrogen receptor alpha (ERα) and modulate the biological responses exerted by the receptor. Biological effects of resveratrol (RES) on estrogen receptor alpha (ERα) remain highly controversial, since both estrogenic and anti-estrogenic properties were observed.. Here, we provide insight into the structural basis of the agonist/antagonist effects of RES on ERα ligand binding domain (LBD). Using atomistic simulation, we found that RES bound ERα monomer in antagonist conformation, where Helix 12 moves away from the ligand pocket and orients into the co-activator binding groove of LBD, is more stable than RES bound ERα in agonist conformation, where Helix 12 lays over the ligand binding pocket. Upon dimerization, the agonistic conformation of RES-ERα dimer becomes more stable compared to the corresponding monomer but still remains less stable compared to the corresponding dimer in antagonist conformation. Interestingly, while the binding pocket and the binding contacts of RES to ERα are similar to those of pure agonist diethylstilbestrol (DES), the binding energy is much less and the hydrogen bonding contacts also differ providing clues for the partial agonistic character of RES on ERα.. Our Molecular Dynamics simulation of RES-ERα structures with agonist and antagonist orientations of Helix 12 suggests RES action is more similar to Selective Estrogen Receptor Modulator (SERM) opening up the importance of cellular environment and active roles of co-regulator proteins in a given system. Our study reveals that potential co-activators must compete with the Helix 12 and displace it away from the activator binding groove to enhance the agonistic activity.

Topics: Animals; Binding Sites; Diethylstilbestrol; Dimerization; Estradiol; Estrogen Receptor alpha; Fulvestrant; Humans; Hydrogen Bonding; Ligands; Models, Molecular; Molecular Dynamics Simulation; Phytoestrogens; Protein Conformation; Protein Structure, Secondary; Protein Structure, Tertiary; Resveratrol; Stilbenes; Tamoxifen

Endothelial dysfunction precedes cardiovascular disease and is accompanied by mitochondrial dysfunction. Here we tested the hypothesis that diesel exhaust particulate extracts (DEPEs), prepared from a truck run at different speeds and engine loads, would inhibit genomic estrogen receptor activation of nuclear respiratory factor-1 (NRF-1) transcription in human umbilical vein endothelial cells (HUVECs). Additionally, we examined how DEPEs affect NRF-1-regulated TFAM expression and, in turn, Tfam-regulated mtDNA-encoded cytochrome c oxidase subunit I (COI, MTCO1) and NADH dehydrogenase subunit I (NDI) expression as well as cell proliferation and viability. We report that 17β-estradiol (E(2)), 4-hydroxytamoxifen (4-OHT), and raloxifene increased NRF-1 transcription in HUVECs in an ER-dependent manner. DEPEs inhibited NRF-1 transcription, and this suppression was not ablated by concomitant treatment with E(2), 4-OHT, or raloxifene, indicating that the effect was not due to inhibition of ER activity. While E(2) increased HUVEC proliferation and viability, DEPEs inhibited viability but not proliferation. Resveratrol increased NRF-1 transcription in an ER-dependent manner in HUVECs, and ablated DEPE inhibition of basal NRF-1 expression. Given that NRF-1 is a key nuclear transcription factor regulating genes involved in mitochondrial activity and biogenesis, these data suggest that DEPEs may adversely affect mitochondrial function leading to endothelial dysfunction and resveratrol may block these effects.

Topics: Cell Proliferation; Cell Survival; Cells, Cultured; Drug Antagonism; Electron Transport Complex IV; Estradiol; Human Umbilical Vein Endothelial Cells; Humans; Mitochondria; Nuclear Respiratory Factor 1; Particulate Matter; Raloxifene Hydrochloride; Resveratrol; Stilbenes; Tamoxifen; Transcription, Genetic; Vehicle Emissions

The anti-estrogenic drug tamoxifen, which is used therapeutically for treatment and prevention of breast cancer, can lead to the development of thrombosis. We found that tamoxifen rapidly increased intracellular free calcium [Ca2+]i in human platelets from both male and female donors. Thus 10 microM tamoxifen increased [Ca2+]i above the resting level by 197 +/- 19%. Tamoxifen acted synergistically with thrombin, ADP, and vasopressin to increase [Ca2+]i. The anti-estrogen ICI 182780 did not attenuate the effects of tamoxifen to increase [Ca2+]i; however, phospholipase C inhibitor U-73122 blocked this effect. 4-hydroxytamoxifen, a major metabolite of tamoxifen, also increased [Ca2+]i, but other tamoxifen metabolites and synthetic derivatives did not. Three hydroxylated derivatives of triphenylethylene (corresponding to the hydrophobic core of tamoxifen) which are transitional structures between tamoxifen (Ca agonist) and diethylstilbestrol (Ca antagonist) increased [Ca2+]i slightly (6% to 24%) and partially inhibited thrombin-induced [Ca2+]i elevation (68% to 79%). Therefore the dimethylaminoethyl moiety is responsible for tamoxifen being a Ca agonist rather than antagonist. 4-Hydroxytamoxifen and polymer-conjugated derivatives of 4-hydroxytamoxifen increased [Ca2+]i, with similar efficacy. The ability of tamoxifen to increase [Ca2+]i in platelets, leading to platelet activation, and its ability to act synergistically with other platelet agonists may contribute to development of tamoxifen-induced thrombosis.

Topics: Adenosine Diphosphate; Adult; Blood Platelets; Calcium; Calcium Signaling; Diethylstilbestrol; Drug Synergism; Estradiol; Estrenes; Estrogen Antagonists; Ethamoxytriphetol; Female; Fulvestrant; Humans; Male; Middle Aged; Molecular Structure; Phosphodiesterase Inhibitors; Pyrrolidinones; Stilbenes; Structure-Activity Relationship; Tamoxifen; Thrombin; Vasopressins

Vascular endothelial cells (EC) are an important target of estrogen action through both the classical genomic (i.e. nuclear-initiated) activities of estrogen receptors alpha and beta (ERalpha and ERbeta) and the rapid "non-genomic" (i.e. membrane-initiated) activation of ER that stimulates intracellular phosphorylation pathways. We tested the hypothesis that the red wine polyphenol trans-resveratrol activates MAPK signaling via rapid ER activation in bovine aortic EC, human umbilical vein EC, and human microvascular EC. We report that bovine aortic EC, human umbilical vein EC, and human microvascular EC express ERalpha and ERbeta. We demonstrate that resveratrol and estradiol (E(2)) rapidly activated MAPK in a MEK-1, Src, matrix metalloproteinase, and epidermal growth factor receptor-dependent manner. Importantly, resveratrol activated MAPK and endothelial nitric-oxide synthase (eNOS) at nm concentrations (i.e. an order of magnitude less than that required for ER genomic activity) and concentrations possibly achieved transiently in serum following oral red wine consumption. Co-treatment with ER antagonists ICI 182,780 or 4-hydroxytamoxifen blocked resveratrol- or E(2)-induced MAPK and eNOS activation, indicating ER dependence. We demonstrate for the first time that ERalpha-and ERbeta-selective agonists propylpyrazole triol and diarylpropionitrile, respectively, stimulate MAPK and eNOS activity. A red but not a white wine extract also activated MAPK, and activity was directly correlated with the resveratrol concentration. These data suggest that ER may play a role in the rapid effects of resveratrol in EC and that some of the atheroprotective effects of resveratrol may be mediated through rapid activation of ER signaling in EC.

Topics: Angiogenesis Inhibitors; Animals; Aorta; Blotting, Western; Cattle; Cell Nucleus; Cells, Cultured; Dose-Response Relationship, Drug; Endothelial Cells; Endothelium, Vascular; Enzyme Activation; Epidermal Growth Factor; Estradiol; Estrogen Receptor alpha; Estrogen Receptor beta; Flavonoids; Fulvestrant; Humans; MAP Kinase Kinase 1; MAP Kinase Signaling System; Mice; Microcirculation; Models, Biological; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Phenols; Phosphorylation; Polyphenols; Resveratrol; Serine; Signal Transduction; Stilbenes; Tamoxifen; Time Factors; Transfection; Umbilical Veins; Wine

Red wine is enriched in resveratrol, trans-3,5,4'-trihydroxystilbene, a compound in grape skin that inhibits the development of pre-neoplastic lesions in mouse mammary tumor cells in culture and inhibits cancer cell proliferation in vitro. Grapes also contain other bioactive compounds including flavonoids, flavans, and anthocyanins. The estrogenic activities of extracts prepared from one white (Freie Weingärtner Wachau, Grüner Veltliner, Austria) and two red wines (Woodbridge, Cabernet Sauvignon, California; and Lenz Moser Prestige, Blaufränkisch Barrique, Austria) were examined and compared with those induced by estradiol (E(2)) and trans-resveratrol. First, the estrogenic activity of the wine extracts was evaluated in a yeast estrogen screen (YES) assay, in which yeast express copper-inducible estrogen receptor alpha (ERalpha) and an estrogen-response-element (ERE)-driven beta-galactosidase reporter. In YES, the white wine extract showed no estrogenic activity. In contrast, both of the red wine extracts showed estrogenic activity equivalent to that of 0.2 nM E(2). Similarly, the white wine extract showed no transcriptional activity with either ERalpha and ERbeta in transiently transfected CHO-K1 cells. In contrast, both red wine extracts stimulated ERE-reporter activity in a concentration-dependent manner that was inhibited by 4-hydroxytamoxifen (4-OHT), indicating that the observed transcriptional activity was ER-mediated. The red wine extracts showed significantly higher ERbeta versus ERalpha agonist activity. Resveratrol showed no agonist activity in YES but activated ERalpha and ERbeta in CHO-K1 cells in a concentration-dependent manner that was inhibited by 4-OHT. This indicates that resveratrol requires mammalian cell components that are absent in yeast for estrogen agonist activity, whereas the estrogenic activity of wine extracts is directly through ERalpha and does not require mammalian cell factors such as coactivators. The estrogenic activity in red wine found by using YES indicates that estrogenic compounds other than resveratrol are present. Chemical analysis clearly showed that the trans-resveratrol content of the red wine extracts was 1 order of magnitude below the detection limit for YES assay.

Topics: Animals; beta-Galactosidase; Breast Neoplasms; CHO Cells; Cricetinae; Estradiol; Estrogen Receptor alpha; Estrogen Receptor beta; Estrogens; Gene Expression; Genes, Reporter; Humans; Plant Extracts; Receptors, Estrogen; Response Elements; Resveratrol; Saccharomyces cerevisiae; Stilbenes; Tamoxifen; Transcriptional Activation; Transfection; Tumor Cells, Cultured; Vitis; Wine

Tamoxifen is the endocrine treatment of choice for all stages of estrogen receptor (ER)-positive breast cancer, and it is the first drug approved to reduce the incidence of breast cancer in high-risk women. Unfortunately, tamoxifen also possesses some estrogen-like effects in the uterus that cause a modest increase in the risk of endometrial cancer. GW5638 is a tamoxifen derivative with a novel carboxylic acid side chain with no uterotropic activity in the rat (Willson et al., J Med Chem, 1994, 37:1550-1552). We have compared and contrasted the actions of 4-hydroxytamoxifen (4-OHT, the active metabolite of tamoxifen) with GW7604 [the presumed metabolite of GW5638 in breast (MCF-7) and endometrial (ECC-1) cell lines in vitro]. GW7604 did not cause the growth of ECC-1 cells at any concentration (10(-11)-10(-6) M), but 4-OHT was weakly estrogen-like at low concentrations (10(-11)-10(-10) M). Compounds (10(-7) M) blocked the growth promoting action of estradiol (10(-10) M) in both ECC-1 and MCF-7 cells. Western blotting was used to show that GW7604 and raloxifene did not affect ER levels significantly, compared with controls, in MCF-7 cells; whereas the pure antiestrogen ICI182,780 decreased ER levels (P < 0.05). An assay system was used that can classify compounds into tamoxifen-like, raloxifene-like, or pure antiestrogens. The assay depends on the activation of the transforming growth factor alpha (TGFalpha) gene in situ by wild-type or D351Y mutant ER stably transfected into MDA-MB-231 cells (MacGregor-Schafer et al., Cancer Res, 1999, 59:4308-4313). GW7604 inhibited both estradiol (10(-9) M) and 4-OHT (10(-8), 10(-7) M) induction of TGFalpha in a concentration related manner (10(-9)-10(-6) M). GW7604 and raloxifene stimulated TGFalpha with the D351Y ER. In contrast, ICI 182,780 (10(-6) M) did not initiate TGFalpha and blocked the induction of TGFalpha with GW7604, raloxifene, and 4-OHT in D351Y-transfected cells. Using computer-assisted molecular models of ER complexes, we found that the antiestrogenic side chain of 4-OHT weakly interacted with the surface amino acid 351 (aspartate), but the carboxylic acid of GW7604 caused a strong repulsion of aspartate 351. We propose that GW7604 is less estrogen-like than 4-OHT, because it disrupts the surface charge around aa351 required for coactivator docking in the 4-OHT:ER complex. This charge is restored in the D351Y ER, thus converting GW7604 from an antiestrogen to an estrogen-like molecule.

Topics: Carcinoma; Cell Division; Cinnamates; Endometrial Neoplasms; Estrogen Receptor alpha; Estrogen Receptor Modulators; Estrogens; Female; Gene Expression Regulation; Humans; Models, Molecular; Receptors, Estrogen; RNA, Messenger; Selective Estrogen Receptor Modulators; Stilbenes; Tamoxifen; Transforming Growth Factor alpha; Tumor Cells, Cultured

Antiestrogens such as tamoxifen are one of the most effective methods of treating estrogen receptor (ERalpha) positive breast cancers; however, the effectiveness of this therapy is limited by the almost universal development of resistance to the drug. If antiestrogens are recognized differently by the cell as it has been suggested, then in disease conditions where tamoxifen fails to function effectively, a mechanistically different antiestrogen might yield successful results. Although many antiestrogens have been developed, a direct comparison of their mechanisms of action is lacking, thus limiting their utility. Therefore, to determine if there are mechanistic differences among available antiestrogens, we have carried out a comprehensive analysis of the molecular mechanisms of action of 4-hydroxy-tamoxifen (40HT), idoxifene, raloxifene, GW7604, and ICI 182,780. Using a novel set of peptides that recognize different surfaces on ERalpha, we have found that following binding to ERalpha, each ligand induces a distinct ERalpha-ligand conformation. Furthermore, transcriptional assays indicate that each ERalpha-ligand complex is recognized distinctly by the transcription machinery, and consequently, antiestrogens vary in their ability to inhibit estradiol- and 40HT-mediated activities. Relative binding assays have shown that the affinity of these ligands for ERalpha is not always representative of their inhibitory activity. Using this assay, we have also shown that the pharmacology of each antiestrogen is influenced differently by hormone binding proteins. Furthermore, GW7604, like ICI 182,780, but unlike the other antiestrogens evaluated, decreases the stability of the receptor. Overall, our results indicate that there are clear mechanistic distinctions among each of the antiestrogens studied. However, GW7604 and ICI 182,780 differ more significantly from tamoxifen than idoxifene and raloxifene. These data, which reveal differences among antiestrogens, should assist in the selection of compounds for the clinical regulation of ERalpha function.

Topics: Blood Proteins; Breast Neoplasms; Cell Division; Cinnamates; Drug Stability; Estradiol; Estrogen Antagonists; Estrogen Receptor alpha; Fulvestrant; Gene Expression; Humans; Protein Binding; Protein Conformation; Raloxifene Hydrochloride; Receptors, Estrogen; Stilbenes; Tamoxifen; Transcription, Genetic; Tumor Cells, Cultured

Estradiol induces vascular endothelial growth factor (VEGF) expression in the rat uterus and this may contribute to the hyperemia and increased vascularity produced by estrogens in this target tissue. Triphenylethylene antiestrogens such as tamoxifen have mixed agonist/antagonist activity and their specific effects are tissue and gene specific. These drugs exhibit primarily antiestrogenic actions in mammary tissue and are thus used for the treatment of breast cancer. These drugs are also suggested to be inhibitors of angiogenesis. However, uterine side effects of tamoxifen are thought to stem largely from the agonist activity of the drug in this tissue. Since side effects of tamoxifen such as uterine bleeding and endometrial cancer seem likely to have an angiogenic component, we have examined the effects of this drug, its metabolite, 4-hydroxy-tamoxifen and two additional triphenylethylene antiestrogens, nafoxidine and clomiphene, on the expression of VEGF and another estrogen regulated gene, c-fos, using the rat uterus as an experimental system. All four compounds increase uterine VEGF and c-fos mRNA levels indicating that the triphenylethylene class of antiestrogens are predominantly agonists for the induction of these genes in the uterus.

Topics: Animals; Blotting, Northern; Clomiphene; Dose-Response Relationship, Drug; Endothelial Growth Factors; Estradiol; Estrogen Antagonists; Estrogens; Female; Lymphokines; Nafoxidine; Ovariectomy; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; RNA, Messenger; Stilbenes; Tamoxifen; Time Factors; Uterus; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Topics: 3',5'-Cyclic-AMP Phosphodiesterases; Calmodulin; Estradiol; Estrogen Antagonists; Nafoxidine; Stilbenes; Structure-Activity Relationship; Tamoxifen

The Ca2+- and phospholipid-dependent phosphotransferase activity of protein kinase C was inhibited by the triphenylethylene compounds clomiphene [drug concentration causing 50% inhibition (IC50) = 25 microM], 4-hydroxytamoxifen (IC50 = 25 microM), and N-desmethyltamoxifen (IC50 = 8 microM). The Ca2+- and phospholipid-independent phosphorylation of protamine sulfate, which is catalyzed by protein kinase C, was not inhibited by the triphenylethylenes, suggesting that they do not interact directly with the active site of protein kinase C. The inhibitory potency of each triphenylethylene was reduced when the phospholipid concentration was increased, providing evidence that these drugs inhibited protein kinase C by interacting with phospholipids. The potencies of the effects of the triphenylethylenes on protein kinase C in the lipid environment of intact cells were evaluated by determining their efficacies in the inhibition of [3H]phorbol 12,13-dibutyrate (PDBu) binding to mouse embryo C3H/10T1/2 cells. Micromolar concentrations of each drug inhibited [3H]PDBu binding in these cells. N-Desmethyltamoxifen, 4-hydroxytamoxifen, and tamoxifen inhibited protein kinase C with the same order of potency as that which has been reported for their inhibition of MCF-7 cell growth by Reddel et al. (1983). N-Desmethyltamoxifen and 4-hydroxytamoxifen were also more potent than tamoxifen in the inhibition of the growth of mouse embryo fibroblast C3H/10T1/2 cells. These correlations suggest that the mechanism of growth inhibition by tamoxifen and its metabolites includes interactions with protein kinase C.

Topics: Animals; Brain; Cells, Cultured; Estrogen Antagonists; Fibroblasts; Mice; Phorbol 12,13-Dibutyrate; Phorbol Esters; Protein Kinase C; Rats; Stilbenes; Structure-Activity Relationship; Tamoxifen

Treatment of MCF 7 human breast cancer cells with three high affinity hydroxylated antiestrogens (Kd for the estrogen receptor = 0.11-0.45 nM) resulted in biphasic inhibition of cell growth. Administration of 0.1-1.0 nM of each drug caused a concentration-dependent decrease in cell number to a maximum of 30-40% of control but no further change was observed as the drug concentration was increased to 1 microM. Between 1.0 and 10 microM, however, a further concentration-dependent decrease in cell proliferation was observed. Among these compounds relative potencies paralleled their affinities for estrogen receptor in the 0.1-10 nM range but at micromolar concentrations this relationship did not hold. It is concluded that antiestrogens inhibit cell proliferation by two distinct mechanisms one of which involves the estrogen receptor and the other a mechanism yet to be defined. The parallel changes in cell cycle kinetic parameters accompanying growth inhibition in both concentration ranges i.e. accumulation of cells in the G1 phase at the expense of S phase cells, suggests that both mechanisms may converge on common pathways critical to cell cycle progression.

Topics: Binding, Competitive; Breast Neoplasms; Cell Division; Cell Line; Clomiphene; Estradiol; Estrogen Antagonists; Humans; Receptors, Estrogen; Stilbenes; Tamoxifen

Topics: Animals; Cell Nucleus; Centrifugation, Density Gradient; Estradiol; Estrogen Antagonists; Female; Nafoxidine; Rats; Receptors, Estrogen; Stilbenes; Tamoxifen; Uterus

Topics: Breast Neoplasms; Cell Line; Centrifugation, Density Gradient; Chromatography, Gel; Estradiol; Female; Humans; Molecular Weight; Receptors, Estrogen; Stilbenes; Tamoxifen; Urea