Estrogen-responsive Human Breast Cancer Cell Research Articles

Secosteroid–quinoline hybrids as new anticancer agents

An elegant approach to unknown secosteroid–quinoline hybrids is disclosed. A series of 13,17-secoestra-1,3,5(10)-trien-17-oic acid [N′-(iso)quinolylmethylene]hydrazides was prepared and these novel type of secosteroids was screened for antiproliferative activity against estrogen-responsive human breast cancer cell line MCF-7. Most of the synthesized compounds showed a cytotoxic effect superior to that of reference drug cisplatin; the lead compound exhibits the highest activity with the IC50 value of about 0.8 μM and is 7 times more active than cisplatin. A high selectivity index was observed for the hit 13,17-secoestra-1,3,5(10)-trien-17-oic acid [N′-quinolylmethylene]hydrazides 2a and 2c. Compounds 2a and 2c evaluated in luciferase reporter assays exhibited high antiestrogenic potency which was superior to that of tamoxifen. These hit compounds were characterized by high activity against MCF-7 cells that retained towards multidrug-resistant NCI/ADR-RES cells.

In vitro and in vivo antiproliferative activity of organo-nickel SCS-pincer complexes on estrogen responsive MCF7 and MC4L2 breast cancer cells. Effects of amine fragment substitutions on BSA binding and cytotoxicity.

A family of organonickel complexes has been prepared, fully characterized, and tested for their antiproliferative activity against estrogen-responsive human breast cancer cells (MCF7). The three SCS-type pincer ligands HL1, HL2, and HL3 and their corresponding Ni(ii) complexes NiL1, NiL2, and NiL3 have been synthesized and fully characterized, including by single crystal diffraction studies for the complexes. The complexes possess square planar geometry with two symmetrical 5-membered nickellacycles. Fluorescence spectroscopy, circular dichroism measurements, molecular modeling, colorimetric based assay and tumor transplantation studies were used to evaluate the protein binding and antiproliferative activities of these organometallic complexes both in vitro and in vivo. Fluorescence quenching was used to investigate bovine serum albumin (BSA) interaction at different temperatures (293, 303 and 313 K), and the results were analyzed using the classical Stern-Volmer equation, allowing us to propose a dynamic quenching mechanism. Studies in vitro on the antiproliferative activity of the three organonickel complexes against estrogen-responsive human breast cancer cells (MCF7) showed promising antitumor activity for NiL1 containing pyrrolidine fragments. In vivo administration of this compound significantly inhibits tumor growth in estrogen-dependent MC4L2 cancer cells in female BALB/c mice.

α-Keto tetrahydrofuran lignan glucosides from the Bangladeshi medicinal plant Terminalia citrina inhibit estradiol (E2) induced proliferation in cancer cells

EtOAc extract from the leaves of Terminalia citrina collected in Bangladesh were separated, and seven previously undescribed α-keto tetrahydrofuran lignan glucosides (terminalosides Q to W) were isolated and characterized. NOESY analysis of 1H NMR spectra and ECD spectroscopic data analysis revealed the absolute stereochemistry of the tetrahydrofuran ring of the isolated constituents as being a (7S,8R,8′S)- configuration in terminalosides Q to U and a (7R,8R,8′S)- configuration in terminalosides V and W. All of the isolated compounds were evaluated for their estrogenic and anti-estrogenic properties using two types of estrogen-responsive human breast cancer cell lines (MCF-7 and T47D). Terminaloside R, which has a dioxymethylene group in its aromatic ring, inhibited 90% of estradiol-enhanced cell proliferation in T47D and MCF-7 cells at concentrations of 0.01 μM and 0.1 μM, respectively. On the other hand, terminaloside T, the analogous compound which has two oxymethyl groups in place of dioxymethylene, suppressed 90% of cell proliferation selectively in T47D cells at a concentration of 0.01 μM. However, terminaloside W, the 7R-stereoisomer of terminaloside R, only showed moderate activity.

Homoisoflavanones with estrogenic activity from the rhizomes of Polygonatum sibiricum

A new homoisoflavanone, (3R)-5-hydroxy-7-methoxyl-3-(2′-hydroxy-4′- methoxybenzyl)-chroman-4-one (1), together with six known analogs, were isolated from the rhizomes of Polygonatum sibiricum. Their structures were elucidated on the basis of extensive spectroscopic analysis. All compounds were tested for their estrogenic activity using the MCF-7 estrogenresponsive human breast cancer cell lines. At a dose of 0.1 μmol/L, compounds 1–7 exhibited significant proliferative effects on MCF-7 cells compared with E2. The molecular docking study results indicated that the activity of compounds 3, 5, 6, and 7 may be the binding with ERR.

Furofuran Lignan Glucosides with Estrogen-Inhibitory Properties from the Bangladeshi Medicinal Plant Terminalia citrina.

Extracts from the leaves of the Bangladeshi medicinal plant Terminalia citrina were prepared, and 13 new furofuran lignan glucosides, terminalosides A-K (1-4, 6-12), 2-epiterminaloside D (5), and 6-epiterminaloside K (13), were characterized using various spectroscopic techniques. Twelve of the isolates were found to contain rare tetraoxygenated aryl groups in their structures. Analysis of the NMR chemical shifts for the oxymethine signals in the furofuran ring suggested a pragmatic approach to determining the relative configuration of these compounds. The ECD and NOESY spectroscopic data obtained allowed for the deduction of the absolute configurations and conformations of the compounds. The isolates were tested for their estrogenic/antiestrogenic activity using the MCF-7 and T47D estrogen-responsive human breast cancer cell lines. Terminalosides B (2) and G (8) exhibited inhibitory effects for both cell lines, and estradiol-enhanced cell proliferation was suppressed by 90% at concentrations lower than 10 μM. Terminaloside E (6) showed inhibitory activity against the T47D cell line, whereas terminalosides C (3), F (7), and I (10) and 6-epiterminaloside K (13) displayed antiestrogenic activity against MCF-7 cells.

Phenolic constituents of the Bangladeshi medicinal plant Pothos scandens and their anti-estrogenic, hyaluronidase inhibition, and histamine release inhibitory activities

Extracts from the stem and roots of the Bangladeshi medicinal plant Pothos scandens L. (Araceae) were isolated, and three hemiterpene glucoside aromatic esters, pothobanosides A (1), B (2), and C (3), and a phenylisobutanoid, pothobanol (4), along with 14 known compounds, were characterized. The isolates were tested for their estrogenic/anti-estrogenic activity using the estrogen-responsive human breast cancer cell lines MCF-7 and T47D, and syringoyl derivatives (2, 3, and canthoside B) showed strong inhibitory activity against both cell lines. Their less oxygenated analogs (1, and markhamioside F) were almost inactive. The isolates were also evaluated for hyaluronidase and histamine release inhibitory activities, and pothobanoside A (1) showed significant hyaluronidase inhibitory activity among the isolated compounds, which was similar to that of the positive control rosmarinic acid. Because hyaluronidase produces an angiogenic response that has been implicated in tumor invasiveness and metastasis, 1 could be valuable as an anti-tumor compound with a different mechanism of action from related compounds (2, 3). Pothobanoside C (3) and pothobanol (4) were also found to inhibit histamine release to a similar degree to the positive control epigallocatechin 3-O-(3″-O-methyl)-gallate. The histamine release inhibitory potency of these isolates may support the traditional uses of this plant in folk medicine.

Design, synthesis and bioevaluation of novel 6-(4-Hydroxypiperidino)naphthalen-2-ol-based potential Selective Estrogen Receptor Modulators for breast cancer.

In a study directed towards development of novel Selective Estrogen Receptor Modulators (SERMs), 1-(4-(2-(dialkylamino)ethoxy)benzyl)-6-(4-hydroxypiperidin-1-yl)-2-naphthol and corresponding aryl methyl ethers were synthesized and bioevaluated against the estrogen-responsive human MCF-7 breast cancer cell line. The phenolic analogs displayed little or no activity, but aryl methyl ether analogs showed significant cytotoxic potency. Also, representative compounds from the aryl methyl ether series showed significant binding and antagonistic activity against ERα. Two representative compounds were also evaluated for invitro membrane permeability, plasma stability as well as in-vivo toxicity in mice. The compounds displayed well-acceptable drug-like invitro membrane permeability as well as plasma stability and were well-tolerated in experimental mice at 300mg/kg dose.

Abstract 566: Withaferin A causes autophagy in normal as well as cancerous human breast cells

Abstract Withaferin A (WA), a promising anticancer constituent of traditional Indian (Ayurvedic) medicinal plant Withania somnifera, inhibits growth of MDA-MB-231 (estrogen-independent) and MCF-7 (estrogen-responsive) human breast cancer cells in culture and MDA-MB-231 xenografts in vivo in association with apoptosis induction. We have shown recently that WA-induced apoptosis in human breast cancer cells is initiated by reactive oxygen species (ROS) resulting from inhibition of mitochondrial respiration. Because ROS are frequently implicated in induction of autophagy, which is an evolutionary conserved process for bulk-degradation of macromolecules including organelles, we raised the question of whether WA treatment causes autophagy. In the present study, we have addressed this question using MDA-MB-231 and MCF-7 human breast cancer cells, a spontaneously immortalized and non-tumorigenic normal human mammary epithelial cell line (MCF-10A), and MDA-MB-231 xenografts from control and WA-treated mice. WA treatment resulted in autophagy induction in cancerous (MCF-7 and MDA-MB-231) as well as normal mammary epithelial cells (MCF-10A) as judged by transmission electron microscopy, cleavage of microtubule-associated protein 1 light chain 3 (LC3), formation of acidic vesicular organelles, and punctate pattern of LC3 localization. Immunohistochemical analysis revealed markedly higher expression of LC3 in MDA-MB-231 xenografts from female athymic mice administered i.p. with 4 mg/kg WA compared with control. Autophagy is a protective mechanism against apoptosis by several agents. Interestingly, inhibition of WA-induced autophagy either by a pharmacological agent (3-methyladenine) or siRNA knockdown of critical autophagy regulating proteins ATG5 or Beclin1 did not have any meaningful impact on growth inhibition or apoptotic cell death resulting from WA exposure in MDA-MB-231 or MCF-7 cells. Collectively, these results indicate that WA induces autophagy in breast cancer cells regardless of estrogen receptor expression and this response is not unique to cancerous breast cells. In addition, unlike many other agents, autophagy induction by WA has no influence on its ability to inhibit cell growth or cause apoptosis at least in breast cancer cells. This investigation was supported by US PHS grant CA142604 awarded by the National Cancer Institute. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 566. doi:1538-7445.AM2012-566

Antiproliferative effects of artemisinin on human breast cancer cells requires the downregulated expression of the E2F1 transcription factor and loss of E2F1-target cell cycle genes

Artemisinin, a sesquiterpene phytolactone derived from Artemisia annua, is a potent antimalarial compound with promising anticancer properties, although the mechanism of its anticancer signaling is not well understood. Artemisinin inhibited proliferation and induced a strong G1 cell cycle arrest of cultured MCF7 cells, an estrogen-responsive human breast cancer cell line that represents an early-stage cancer phenotype, and effectively inhibited the in-vivo growth of MCF7 cell-derived tumors from xenografts in athymic nude mice. Artemisinin also induced a growth arrest of tumorigenic human breast cancer cell lines with preneoplastic and late stage cancer phenotypes, but failed to arrest the growth of a nontumorigenic human mammary cell line. Concurrent with the cell cycle arrest of MCF7 cells, artemisinin selectively downregulated the transcript and protein levels of the CDK2 and CDK4 cyclin-dependent kinases, cyclin E, cyclin D1, and the E2F1 transcription factor. Analysis of CDK2 promoter-luciferase reporter constructs showed that the artemisinin ablation of CDK2 gene expression was accounted for by the loss of CDK2 promoter activity. Chromatin immunoprecipitation revealed that artemisinin inhibited E2F1 interactions with the endogenous MCF7 cell CDK2 and cyclin E promoters. Moreover, constitutive expression of exogenous E2F1 prevented the artemisinin-induced cell cycle arrest and downregulation of CDK2 and cyclin E gene expression. Taken together, our results demonstrate that the artemisinin disruption of E2F1 transcription factor expression mediates the cell cycle arrest of human breast cancer cells and represents a critical transcriptional pathway by which artemisinin controls human reproductive cancer cell growth.

Design, synthesis and bioevaluation of novel candidate selective estrogen receptor modulators

In an systematic attempt to develop novel Selective Estrogen Receptor Modulators (SERMs), chiral 1-((4-(2-(dialkylamino)ethoxy)phenyl)(2-hydroxynaphthalen-1-yl)methyl)piperidin-4-ols were designed based on an accepted pharmacophore model. Simpler prototypes, viz. racemic 1-((2-hydroxynaphthalen-1-yl)arylmethyl)piperidin-4-ols, were first synthesized to develop kinetic resolution to pure enantiomers. Simultaneously, a series of racemic 1-((4-(2-(dialkylamino)ethoxy)phenyl)(2-hydroxynaphthalen-1-yl)methyl)piperidin-4-ols were evaluated against estrogen-responsive human MCF-7 breast cancer cells, but the compounds were found to be moderately active. The lack of potency could be due to the molecular bulk resulting in inadequate fit at the receptor. Subsequently, the molecular motif was modified to achiral 1-(4-(2-(dialkylamino)ethoxy)benzyl)naphthalen-2-ols by removing the piperidinol moiety. Bioevaluation of this new series of compounds displayed significantly enhanced cytotoxicity against MCF-7 cells. A representative compound for this series showed estrogen receptor alpha binding activity and the action is that of an antagonist.

Estrogenic and anti-estrogenic compounds from the Thai medicinal plant, Smilax corbularia (Smilacaceae)

From the rhizomes of Smilax corbularia Kunth. (Smilacaceae), 11 compounds, (2 R,3 R)-2″-acetyl astilbin, (2 R,3 R)-3″-acetyl astilbin, (2 R,3 R)-4″-acetyl astilbin, (2 R,3 R)-3″-acetyl engeletin, (2 R,3 S)-4″-acetyl isoastilbin, 2-(4-hydroxyphenyl)-3,4,9,10-tetrahydro-3,5-dihydroxy-10-(3,4-dihydroxyphenyl)-(2 R,3 R,10 R)-2H,8H-benzo [1,2-b:3,4-b′] dipyran-8-one, 2-(4-hydroxyphenyl)-3,4,9,10-tetrahydro-3,5-dihydroxy-10-(3,4-dihydroxyphenyl)-(2 R,3 R,10 S)-2H, 8H-benzo [1,2-b:3,4-b′] dipyran-8-one, 3,4-dihydro-7-hydroxy-4-(3,4-dihydroxyphenyl)-5-[(1 E)-2-(4-hydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, 3,4-dihydro-7-hydroxy-4-(3,4-dihydroxy-phenyl)-5-[(1 E)-2-(3,4-dihydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, 3,4-dihydro-7-hydroxy-4-(4-hydroxy-3-methoxyphenyl)-5-[(1 E)-2-(4-hydroxyphenyl) ethenyl]-2H-1-benzopyran-2-one, and 5,7,3′,4′-tetrahydroxy-3-phenylcoumarin along with 34 known compounds were isolated and characterized as 19 flavonoids, 14 catechin derivatives, 6 stilbene derivatives, and 6 miscellaneous substances. All isolates had their estrogenic and anti-estrogenic activities determined using the estrogen-responsive human breast cancer cell lines MCF-7 and T47D. The major constituents were recognized as flavanonol rhamnosides by the suppressive effect on estradiol induced cell proliferation at a concentration of 1 μM. Meanwhile, flavanonol rhamnoside acetates demonstrated estrogenic activity in both MCF-7 and T47D cells at a concentration of 100 μM, and they enhanced the effects of co-treated E2 on T47D cell proliferation at concentrations of more than 0.1 μM.

Antiestrogenic Constituents of the Thai Medicinal Plants Capparis flavicans and Vitex glabrata

Antiestrogenic compounds were investigated from Thai indigenous plants for galactogogues since estrogen is reported to suppress lactation in breastfeeding women. The aerial parts of the Thai medicinal plant Capparis flavicans, which has traditionally been used to promote lactation, gave the new compound capparoside A (1), along with 28 known compounds. The leaves of Vitex glabrata belong to the same genus as the chaste tree (Vitex agnus-castus), which is used traditionally to support lactation, and afforded the new compounds khainaoside A (14), khainaoside B (15), and khainaoside C (16), together with six known compounds. The isolates were tested for their biological activity using the estrogen-responsive human breast cancer cell lines MCF-7 and T47D. Syringaresinol (3) and principin (6), from C. flavicans, and khainaoside A (14) showed the most potent inhibitory effects on estrogen-enhanced cell proliferation among all compounds isolated. These results suggest that the lactation-promoting properties of C. flavicans might be related to the inhibitory effect on excess estrogen of women who experience insufficient breastfeeding and highlight the possibility of using V. glabrata leaves for their antiestrogenic properties.

Artemisinin selectively decreases functional levels of estrogen receptor-alpha and ablates estrogen-induced proliferation in human breast cancer cells

MCF7 cells are an estrogen-responsive human breast cancer cell line that expresses both estrogen receptor (ER) alpha and ERbeta. Treatment of MCF7 cells with artemisinin, an antimalarial phytochemical from the sweet wormwood plant, effectively blocked estrogen-stimulated cell cycle progression induced by either 17beta-estradiol (E(2)), an agonist for both ERs, or by propyl pyrazole triol (PPT), a selective ERalpha agonist. Artemisinin strongly downregulated ERalpha protein and transcripts without altering expression or activity of ERbeta. Transfection of MCF7 cells with ERalpha promoter-linked luciferase reporter plasmids revealed that the artemisinin downregulation of ERalpha promoter activity accounted for the loss of ERalpha expression. Artemisinin treatment ablated the estrogenic induction of endogenous progesterone receptor (PR) transcripts by either E(2) or PPT and inhibited the estrogenic stimulation of a luciferase reporter plasmid driven by consensus estrogen response elements (EREs). Chromatin immunoprecipitation assays revealed that artemisinin significantly downregulated the level of endogeneous ERalpha bound to the PR promoter, whereas the level of bound endogeneous ERbeta was not altered. Treatment of MCF7 cells with artemisinin and the pure antiestrogen fulvestrant resulted in a cooperative reduction of ERalpha protein levels and enhanced G(1) cell cycle arrest compared with the effects of either compound alone. Our results show that artemisinin switches proliferative human breast cancer cells from expressing a high ERalpha:ERbeta ratio to a condition in which ERbeta predominates, which parallels the physiological state linked to antiproliferative events in normal mammary epithelium.

METABOLISM OF THE α,β-UNSATURATED KETONES, CHALCONE AND TRANS-4-PHENYL-3-BUTEN-2-ONE, BY RAT LIVER MICROSOMES AND ESTROGENIC ACTIVITY OF THE METABOLITES

When chalcone and trans-4-phenyl-3-buten-2-one (PBO) were incubated with liver microsomes of untreated rats in the presence of NADPH, 4-hydroxychalcone and trans-4-(4-hydroxyphenyl)-3-buten-2-one (4-OH-PBO), respectively, were formed as major metabolites. Two minor metabolites of chalcone, 4'-hydroxychalcone and 2-hydroxychalcone, were also observed. The oxidase activity affording 4-hydroxychalcone was inhibited by SKF 525-A, disulfiram, ketoconazole, and alpha-naphthoflavone. The oxidase activities leading to 4-hydroxychalcone and 4'-hydroxychalcone were enhanced in liver microsomes of 3-methylcholanthrene- and phenobarbital-treated rats, respectively. The activity generating 2-hydroxychalcone was enhanced in liver microsomes of 3-methylcholanthrene- and dexamethasone-treated rats. The oxidation of PBO to 4-OH-PBO was inhibited by SKF 525-A, ketoconazole, disulfiram, and sulfaphenazole. This activity was enhanced in liver microsomes of 3-methylcholanthrene-, acetone- and phenobarbital-treated rats. 4-Hydroxylation, 4'-hydroxylation, and 2-hydroxylation of chalcone were catalyzed by rat recombinant cytochrome P450 1A1, 1A2, and 2C6; by 1A1 and 2C6; and by 1A1 and 3A1, respectively. PBO was oxidized by cytochrome P450 1A1, 1A2, 2C6, and 2E1. Chalcone and PBO were negative in an estrogen reporter assay using estrogen-responsive human breast cancer cell line MCF-7. However, 4-hydroxychalcone, 2-hydroxychalcone, 4'-hydroxychalcone, and 4-OH-PBO exhibited estrogenic activity.

New Estrogenic Prenylflavone fromEpimedium brevicornumInhibits the Growth of Breast Cancer Cells

Estrogens maintain female sexual health. The hormone also drives the growth of estrogen receptor (ER) positive breast tumors, and ER modulators, like tamoxifen, are used to reduce tumor recurrence. To identify phytoestrogens with possible health benefits, we screened several Traditional Chinese Medicines and encountered an extract from the leaves of Epimedium brevicornum (EB), with strong (EC50: 1.3 microg/mL) and specific ER-stimulatory activity. It increased estrogen-responsive human breast cancer cell proliferation at low doses, but paradoxically caused profound inhibition of growth at higher doses. Using bioassay-guided fractionation, we isolated and characterized a new prenylflavone, breviflavone B, which exerted biphasic stimulatory and inhibitory effects on breast cancer cell proliferation, mimicking the effects of EB. In contrast to estradiol and genistein, high doses (> 2 microM) of breviflavone B almost eliminated ERalpha protein; a process that may be mediated through increased proteasome degradation. Pre-clinical studies are needed to explore whether these prenylflavones are of value in estrogen-deficiency states and for prophylaxis of breast cancer.

Expression of Wnt genes and frizzled 1 and 2 receptors in normal breast epithelium and infiltrating breast carcinoma

The Wnt genes encode a family of related, secreted proteins which initiate a signal cascade upon binding to cell surface receptor molecules. The signaling pathway has been shown to be critical for normal growth and development in model organisms and is implicated in the genesis of numerous human cancers. Wnt proteins regulate mammary development in the mouse but their precise role in normal breast development and malignant transformation in humans remains poorly defined. In this study, we have examined the expression of several Wnt ligands by in situ anti-sense RNA hybridization in normal and malignant human breast tissue, as well as in several estrogen-responsive and estrogen-independent human breast cancer cell lines. The specific Wnt genes tested included Wnt1, Wnt2, Wnt4, Wnt5a, Wnt5b, Wnt6, Wnt7b and Wnt10b. We have also studied the expression of frizzled receptors 1 and 2 by immunohistochemistry in these tissues. Our results indicate that several of the Wnt ligands, especially Wnt1 and Wnt6, are strongly expressed in both normal and malignant breast tissue and that Wnt7b is down-regulated in breast cancer, compared to normal breast epithelium. The expression of frizzled 1 and 2 receptors was found to be up-regulated in breast cancer. These studies provide additional support to the hypothesis that the Wnt signaling pathway is involved in human breast cancer.

Hsp90/p50cdc37 Is Required for Mixed-lineage Kinase (MLK) 3 Signaling

Mixed-lineage kinase 3 (MLK3) is a mitogen-activated protein kinase (MAPK) kinase kinase that activates MAPK pathways, including the c-Jun NH(2)-terminal kinase (JNK) and p38 pathways. MLK3 and its family members have been implicated in JNK-mediated apoptosis. A survey of human cell lines revealed high levels of MLK3 in breast cancer cells. To learn more about MLK3 regulation and its signaling pathways in breast cancer cells, we engineered the estrogen-responsive human breast cancer cell line, MCF-7, to stably, inducibly express FLAG epitope-tagged MLK3. FLAG.MLK3 complexes were isolated by affinity purification, and associated proteins were identified by in-gel trypsin digestion followed by liquid chromatography/tandem mass spectrometry. Among the proteins identified were heat shock protein 90alpha,beta (Hsp90) and its kinase-specific co-chaperone p50(cdc37). We show that endogenous MLK3 complexes with Hsp90 and p50(cdc37). Further experiments demonstrate that MLK3 associates with Hsp90/p50(cdc37) through its catalytic domain in an activity-independent manner. Upon treatment of MCF-7 cells with geldanamycin, an ansamycin antibiotic that inhibits Hsp90 function, MLK3 levels decrease dramatically. Furthermore, tumor necrosis factor alpha-induced activation of MLK3 and JNK in MCF-7 cells is blocked by geldanamycin treatment. Our finding that geldanamycin treatment does not affect the cellular levels of the downstream signaling components, MAPK kinase 4, MAPK kinase 7, and JNK, suggests that Hsp90/p50(cdc37) regulates JNK signaling at the MAPK kinase kinase level. Previously identified Hsp90/p50(cdc37) clients include oncoprotein kinases and protein kinases that promote cellular proliferation and survival. Our findings reveal that Hsp90/p50(cdc37) also regulates protein kinases involved in apoptotic signaling.

Host microenvironment in breast cancer development: epithelial-cell-stromal-cell interactions and steroid hormone action in normal and cancerous mammary gland.

Mammary epithelial cells comprise the functional component of the normal gland and are the major target for carcinogenesis in mammary cancer. However, the stromal compartment of the normal gland and of tumors plays an important role in directing proliferative and functional changes in the epithelium. In vivo and in vitro studies of the murine mammary gland have provided insights into novel stroma-dependent mechanisms by which estrogen and progesterone action in the epithelium can be modulated by hepatocyte growth factor (HGF) and the extracellular matrix proteins, collagen type I, fibronectin and laminin. In vitro and in vivo studies of estrogen receptor positive, estrogen-responsive human breast cancer cells have also demonstrated that estrogen responsiveness of tumor cells can also be modulated by extracellular matrix proteins, collagen type I and laminin.

Estrogenic Activity of Stilbene Derivatives

We previously reported that trans-stilbene is metabolically activated to estrogenic compounds by a liver microsomal enzyme system. In this study, we demonstrated the structural requirement for estrogenic activity of various stilbene derivatives including proestrogens. High estrogenic activity in 4,4′-dihydroxystilbene, 4-amino-4′-hydroxystilbene, 4,4′-dihydroxy-α-methylstilbene, hexestrol, and diethylstilbestrol (DES), moderate activity in 4-hydroxystilbene, 4-aminostilbene, 4-hydroxyazobenzene, and 4-hydroxy-4′-nitrostilbene, low activity in 4-nitrostilbene, 4,4′-dihydroxydibenzyl, resveratrol, and 4-hydroxy-α-methylstyrene, and marginal activity in 4,4′-dimethoxystilbene and 4-hydroxymethylstilbene were observed in an estrogen reporter assay using the estrogen-responsive human breast cancer cell line MCF-7 and a binding assay with rat uterus estrogen receptor. In contrast, α-methylstilbene, 4,4′-dimethoxystilbene, 4-hydroxymethylstilbene, dibenzyl, tolan and azobenzene also exhibited estrogenic activities after incubation with liver microsomes of 3-methylcholanthrene- or phenobarbital-treated rats in the presence of NADPH. These results suggest that the structural requirements for the estrogenic activities of stilbene derivatives are a p-hydroxyl group in the A-phenyl ring, vinyl linkage, and a B-phenyl ring for the maximal activity, and hydrophobicity of the linkage for higher activity as observed in DES. p-Nitro and amino groups in the A-phenyl ring are also effective for the estrogenic activity.

Metabolic Activation of Proestrogenic Diphenyl and Related Compounds by Rat Liver Microsomes

In this study, liver microsome-mediated activation of diphenyl (DP), diphenylmethane (DPM) and 2,2-diphenylpropane (DPP) to estrogens was demonstrated. These three compounds were negative in estrogen reporter assay using estrogen-responsive human breast cancer cell line MCF-7. However, they exhibited estrogenic activity after incubation with liver microsomes of 3-methylcholanthrene-treated rats in the cases of DP and DPM, or of phenobarbital-treated rats in the cases of DP and DPP, in the presence of NADPH. When these compounds were incubated with liver microsomes in the presence of NADPH, monohydroxyl and dihydroxyl derivatives were formed. These hydroxylated metabolites, 4-hydroxydiphenyl, 3-hydroxydiphenyl, 2-hydroxydiphenyl, 4-hydroxydiphenylmethane, 2-(4-hydroxyphenyl)-2-phenylpropane (4-OH-DPP), 4,4′-dihydroxydiphenyl, 4,4′-dihydroxydiphenylmethane and 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), all exhibited estrogenic activity in MCF-7 cells. Binding assay of these hydroxylated compounds with rat uterus estrogen receptor was also positive. These results suggest that the estrogenic activities of DP, DPM and DPP were due to the formation of hydroxylated metabolites by the liver cytochrome P450 system.