Pure selective estrogen receptor modulators, new molecules having absolute cell specificity ranging from pure antiestrogenic to complete estrogen-like activities

The effect of estrogenic compounds on psychosis-like behaviour in female rats

17β-estradiol treatment has shown benefit against schizophrenia symptoms, however long-term use may be associated with negative side-effects. Selective estrogen receptor modulators, such as raloxifene and tamoxifen, have been proposed as suitable alternatives to 17β-estradiol. An isomer of 17β-estradiol, 17α-estradiol, is considered less carcinogenic, and non-feminising in males, however little is known about its potential as a treatment for schizophrenia. Moreover, the mechanism underlying the therapeutic action of estrogens remains unclear. We aimed to investigate the ability of these estrogenic compounds to attenuate psychosis-like behaviour in rats. We used two acute pharmacologically-induced assays of psychosis-like behaviour: psychotomimetic drug-induced hyperlocomotion and disruption of prepulse inhibition (PPI). Female Long Evans rats were either intact, ovariectomised (OVX), or OVX and chronically treated with 17β-estradiol, 17α-estradiol, raloxifene or tamoxifen. Only 17β-estradiol treatment attenuated locomotor hyperactivity induced by the indirect dopamine receptor agonist, methamphetamine. 17β-estradiol- and tamoxifen-treated rats showed attenuated methamphetamine- and apomorphine (dopamine D1/D2 receptor agonist)-induced disruption of PPI. Raloxifene-treated rats showed attenuated apomorphine-induced PPI disruption only. Baseline PPI was significantly reduced following OVX, and this deficit was reversed by all estrogenic compounds. Further, PPI in OVX rats was increased following administration of apomorphine. This study confirms a protective effect of 17β-estradiol in two established animal models of psychosis, while tamoxifen showed beneficial effects against PPI disruption. In contrast, 17α-estradiol and raloxifene showed little effect on dopamine receptor-mediated psychosis-like behaviours. This study highlights the utility of some estrogenic compounds to attenuate psychosis-like behaviour in rats, supporting the notion that estrogens have therapeutic potential for psychotic disorders.

Exploring the anti-breast cancer potential of flavonoid analogs

In the course of our search for new antitumor agents for breast cancer, novel flavone derivatives were synthesized, characterized and examined for their antitumor activities against breast cancer cell lines.

Combined blockade of testicular and locally made androgens in prostate cancer: a highly significant medical progress based upon intracrinology

Recently two drugs, namely the antiandrogen MDV-3100 and the inhibitor of 17α-hydroxylase abiraterone have been accepted by the FDA for the treatment of castration-resistant prostate cancer (CRPC) with or without previous chemotherapy, with a prolongation of overall survival of 2.2-4.8 months. While medical (GnRH agonist) or surgical castration reduces the serum levels of testosterone by about 97%, an important concentration of testosterone and dihydrotestosterone remains in the prostate and activates the androgen receptor (AR), thus offering an explanation for the positive data obtained in CRPC. In fact, explanation of the response observed with MDV-3100 or enzalutamide in CRPC is essentially a blockade of the action or formation of intraprostatic androgens. In addition to the inhibition of the action or formation of androgens made locally by the mechanisms of intracrinology, increased AR levels and AR mutations can be involved, especially in very advanced disease. Future developments look at more efficient inhibitors of the action or formation of intraprostatic androgens and starting treatment earlier when blockade of androgens can exert long-term control and even cure prostate cancer treated at a stage before the appearance of metastases. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Specific transcriptional response of four blockers of estrogen receptors on estradiol-modulated genes in the mouse mammary gland

Novel agents for the endocrine therapy of breast cancer are needed, especially in order to take advantage of the multiple consecutive responses observed in metastatic progressing breast cancer following previous hormone therapy, thus delaying the use of cytotoxic chemotherapy with its frequent poor tolerance and serious side effects. Acolbifene (ACOL) is a novel and unique antiestrogen which represents a unique opportunity to achieve the most potent and specific blockade of estrogen action in the mammary gland and uterus while exerting estrogen-like beneficial effects in other tissues, especially the bones. To better understand the specificity of action of ACOL, we have used Affymetrix GeneChips containing 45,000 probe sets to analyze 34,000 genes to determine the specificity of this compound compared to the pure antiestrogen fulvestrant, as well as to the mixed antagonists/agonists tamoxifen and raloxifene to block the effect of estradiol (E(2)) and to induce effects of their own on the genomic profile in the mouse mammary gland. The genes modulated by E(2) were those identified in two separate experiments and validated by quantitative real-time PCR (qPCR). Three hours after the single subcutaneous injection of E(2) (0.05 μg), the simultaneous administration of ACOL, fulvestrant, tamoxifen, and raloxifene blocked by 98, 61, 43, and 92 % the number of E(2)-upregulated genes, respectively. On the other hand, 70, 10, 25, and 55 % of the genes down-regulated by E(2) were blocked by the same compounds. Of the 128 genes modulated by E(2), 49 are associated with tumorigenesis while 22 are known to be associated with breast cancer. When used alone, ACOL modulated the smallest number of genes also influenced by E(2), namely 4 %, thus possibly explaining potential utilities of this compound in breast cancer prevention and therapy.

Blockade of testicular and adrenal androgens in prostate cancer treatment

Prostate cancer is the most hormone sensitive of all cancers. However, any hormonal therapeutic strategy must take into account the fact that two almost equivalent sources of androgens act in the prostate, namely testosterone of testicular origin, and the locally produced androgens testosterone and dihydrotestosterone (DHT) derived from dehydroepiandrosterone of adrenal origin. Combined androgen blockade--medical or surgical castration plus a pure antiandrogen--would, therefore, be the logical first-line treatment for prostate cancer, although castration or an antiandrogen alone is still chosen in the majority of cases. Although long-term control, or even cure, is possible when combined androgen blockade is used when the tumor is localized, resistance to treatment invariably develops in patients when start of treatment is delayed until the disease has become metastatic. This observation can be explained either by elevated levels of the androgen receptor, which can increase the response to low levels of androgens and also modify the response to antiandrogens; or by local biosynthesis of androgens. Research to identify new and more potent antiandrogens, as well as blockers of peripheral and adrenal androgen biosynthesis--such as abiraterone--could be of great importance.

Synthesis and structure-activity relationships of analogs of EM-652 (acolbifene), a pure selective estrogen receptor modulator. Study of nitrogen substitution

EM-652 (acolbifene) analogs have been synthesized as selective estrogen receptor modulators. Substitution on the nitrogen atom of these 2H-1-benzopyran derivatives has been studied for its influence on antiestrogenic activity. Binding to the rat estrogen receptor, inhibition of estradiol-stimulated proliferation of T-47D breast cancer cells, as well as antiuterotrophic and uterotrophic activities in ovariectomized mice have been evaluated. 2H-1-Benzopyran 1b (EM-343, racemic form of EM-652), which contains a piperidine ring, shows the best pharmacological profile; RBA = 380, IC50 value = 0.110 nM (in T-47D cells), as well as 63% and 84% antiuterotrophic inhibitions at the 7.5 and 75 nmol doses, respectively.

A Nongenomic Action of 17β-Estradiol as the Mechanism Underlying the Acute Suppression of Secretion of Luteinizing Hormone1

The objective of the present study was to determine the ability of 17beta-estradiol (E(2)) and conjugated forms of E(2) (E(2) conjugated to BSA [E(2)-BSA] and a novel conjugate, E(2) conjugated to a small peptide [E(2)-PEP]) to prevent the GnRH-induced secretion of LH and to determine the role of estradiol receptors (ERs) and ER subtypes (ERalpha, also known as ESR1, and ERbeta, also known as ESR2) in the mediation of the acute action of E(2) in primary cultures of ovine pituitary cells. Preincubation of cells for 15 min with E(2), E(2)-BSA, or E(2)-PEP prevented the GnRH-induced secretion of LH (P < 0.01). Treatment of cells with nonestrogenic steroid hormones did not affect secretion of LH when given alone, nor did these steroids impair the E(2)-induced inhibition of LH secretion (P > 0.1). Likewise, treatment of cells with the ER-antagonists tamoxifen, hydroxytamoxifen, or ICI 182 780 did not affect (P > 0.1) secretion of LH when given alone but did prevent (P < 0.01) the inhibition by E(2) and the E(2)-conjugates on GnRH-induced secretion of LH. When cells were treated with subtype-selective ER agonists, the ERalpha agonist (propylpyrazole-triol), but not the ERbeta agonist (diarylpropionitrile), decreased (P < 0.01) the GnRH-induced secretion of LH. In conclusion, the rapidity by which E(2) prevented GnRH-induced release of LH in ovine pituitary cells suggests that this inhibition is mediated via a nongenomic action of E(2). The inhibition of GnRH-induced secretion of LH proved to be steroid specific and mediated by ERs. It may occur specifically through ERalpha. The fact that E(2)-BSA or E(2)-PEP mimicked the action of E(2) suggests that this effect was mediated by an ER associated with the plasma membrane.

CNS: sex steroids and SERMs

The central nervous system (CNS) is one of the main target tissues for sex steroid hormones, which act both through genomic mechanisms, modulating synthesis, release, and metabolism of many neuropeptides and neurotransmitters, and through nongenomic mechanisms, influencing electrical excitability, synaptic function, and morphological features. The identification of the brain as a de novo source of neurosteroids modulating cerebral function, suggests that the modifications in mood and cognitive performances occurring in postmenopausal women could also be related to a modification in the levels of neurosteroids, particularly allopregnanolone and DHEA, GABA-A agonist, and antagonist, respectively. The selective estrogen receptor modulators (SERMs) are compounds that activate the estrogen receptors with different estrogenic and antiestrogenic tissue-specific effects. In addition to the effects of the classic steroid hormones on the CNS, the study of selective estrogen receptor modulators impact on the neuroendocrine system has recently provided encouraging results, indicating that raloxifene analog LY 117018 and the new generation SERM EM-652 have an estrogen-like action on beta-endorphin and on allopregnanolone in ovariectomized rats, while they exert an anti-estrogenic effect in fertile rats and in ovariectomized rats treated with estrogens. In addition, raloxifene administration in postmenopausal women plays an estrogen-like effect on circulating beta-EP and allopregnanolone levels, and it restores the response of beta-EP and allopregnanolone to neuroendocrine tests. In conclusion, the positive effects of HRT on mood and cognition in postmenopausal women occur via the modulation of neuroendocrine pathways and probably also of neurosteroidogenesis. The effects of raloxifene on mood and cognition encourage the efforts in the research of an ideal estrogen replacement therapy, showing all the positive effects of estrogens and fewer side effects.

The combination of a novel selective estrogen receptor modulator with an estrogen protects the mammary gland and uterus in a rodent model: the future of postmenopausal women's health?

The Women's Health Initiative Study and other reports have created major uncertainty among postmenopausal women and physicians concerning hormone replacement therapy. We have thus investigated the possibility of replacing the progestin in hormone replacement therapy by a novel selective estrogen receptor (ER) modulator having potent and pure antiestrogenic activity in the mammary gland and uterus. As measured by changes in histology and Cdc47 labeling in the rat model, the present study shows that the stimulatory effect of estradiol in the mammary gland and uterus is efficiently blocked by simultaneous administration of the novel selective ER modulator EM-652, but bone mineral density is preserved and serum cholesterol is decreased. After the administration of 14C-labeled EM-652, we observed that there is no detectable radioactivity in the brain. Moreover, ER alpha immunoreactivity remained constant in the hypothalamus after EM-652 treatment, whereas ER alpha became almost undetectable in the mammary gland and uterus. The present data show the poor or absent access of EM-652 to the brain, whereas the effects of estrogens are efficiently neutralized in the mammary gland and uterus. Such data support the exciting possibility of a novel approach that could meet most of the needs of women's health at menopause, namely control of hot flushes and prevention of breast, uterine, and ovarian cancer as well as osteoporosis and potentially helping brain function and preventing Alzheimer's disease with no identifiable risk or negative effect.

Effect of antiestrogens and aromatase inhibitor on basal growth of the human breast cancer cell line MCF-7 in serum-free medium

Antiestrogens are efficient inhibitors of estrogen-mediated growth of human breast cancer. Besides inhibiting estradiol-stimulated growth, antiestrogens may have a direct growth-inhibitory effect on estrogen receptor (ER) positive cells and thus be more efficient than aromatase inhibitors, which will only abrogate estrogen-dependent tumor growth. To address this issue, we have used the human breast cancer cell line MCF-7/S9 as a model system which is maintained in a chemically defined medium without serum and estrogen. The addition of estradiol results in an increase in cell growth rate. Thus, the MCF-7/S9 cell line is estrogen-responsive but not estrogen-dependent. Three different types of antiestrogens, namely tamoxifen, ICI 182,780 and EM-652 were found to exert a significant and dose-dependent inhibition of basal growth of MCF-7/S9 cells. The growth-inhibitory effect of the three antiestrogens was prevented by simultaneous estradiol treatment. Antiestrogen treatment also reduced the basal pS2 mRNA expression level, thus indicating spontaneous estrogenic activity in the cells. However, treatment with the aromatase inhibitor had no effect on basal cell growth, excluding that endogenous estrogen synthesis is involved in basal growth. These data demonstrate that in addition to their estrogen antagonistic effect, antiestrogens have a direct growth-inhibitory effect which is ER-mediated. Consequently, in the subset of ER positive breast cancer patients with estrogen-independent tumor growth, antiestrogen therapy may be superior to treatment with aromatase inhibitors which only inhibit estrogen formation but do not affect cancer cell growth in the absence of estrogens.

Genomic and nongenomic mechanisms of nitric oxide synthesis induction in human endothelial cells by a fourth-generation selective estrogen receptor modulator

Cardiovascular disease is the leading cause of morbidity and mortality in postmenopausal women. EM-652 (acolbifene) is a fourth-generation selective ER modulator (SERM) exerting complete antiestrogenic effects on the breast and uterus. EM-652 potently inhibits bone resorption and induces positive lipid modifications in estrogen-deficient animals. As most of the cardioprotective actions of estrogen are exerted directly at the vascular level, we studied the effects of EM-652 on endothelial production of nitric oxide (NO) in vitro and in vivo. EM-652 triggers NO release by human umbilical vein endothelial cells through nongenomic mechanisms, rapidly activating endothelial nitric oxide synthase (eNOS) via an ER-dependent sequential activation of MAPKs and PI3K/Akt pathways independently from gene transcription or protein synthesis. Moreover, EM-652 increases eNOS protein levels during prolonged treatments. Upon pharmacological comparison, EM-652 is markedly more potent than the SERMs raloxifene and tamoxifen in increasing NO synthesis from endothelial cells. In ovariectomized and fertile rats, EM-652 increases aortic eNOS expression and enzymatic activity at low, but not at higher, dosages. The present data show that EM-652 (acolbifene) has estrogen-like activity on the vascular wall, directly increasing NO production through genomic and nongenomic mechanisms in vitro and in vivo.

Effects of the new generation selective estrogen receptor modulator EM-652 and oral administration of estradiol valerate on circulating, brain, and adrenal beta-endorphin and allopregnanolone levels in intact fertile and ovariectomized rats

OBJECTIVE

To investigate the effects of oral estradiol valerate (EV); EM-652, a new-generation selective estrogen receptor modulator; and both agents on central and peripheral beta-endorphin (beta-EP) and allopregnanolone levels in fertile and ovariectomized rats.

DESIGN

Prospective study.

SETTING

Animal laboratory in an academic research environment.

ANIMALS

Thirteen groups of eight Wistar female rats received oral EV (0.01 or 0.05 mg/kg of body weight daily), EM-652 (0.1, 1, or 5 mg/kg daily), or EV (0.05 mg/kg daily) and EM-652 (0.1, 1, or 5 mg/kg/daily) for 14 days.

INTERVENTION(S)

beta-Endorphin levels content in the hypothalamus, hippocampus, anterior and neurointermediate pituitary, and plasma were measured. Allopregnanolone levels in the hypothalamus, hippocampus, anterior pituitary, adrenal glands, and serum were measured.

MAIN OUTCOME MEASURE(S)

beta-Endorphin and allopregnanolone levels.

RESULT(S)

In ovariectomized rats, administration of EV or EM-652 reverses changes in beta-EP and allopregnanolone levels induced by ovariectomy. Administration of EM-652 plus EV prevents the increase in beta-EP and allopregnanolone levels induced by EV in the hippocampus, hypothalamus, and pituitary but not in the adrenal glands and serum.

CONCLUSIONS

In ovariectomized rats, EM-652 has an estrogen-like action that becomes antiestrogenic in the presence of EV administration. In fertile animals, EM-652 exerts estrogen-like or slight antiestrogenic effects.