Comparison of the effects of EM-652 (SCH57068), tamoxifen, toremifene, droloxifene, idoxifene, GW-5638 and raloxifene on the growth of human ZR-75-1 breast tumors in nude mice

Changes in Health-related Parameters Associated with Sports Performance Enhancement Drugs

The purpose of this study was to evaluate changes in health-related parameters caused by the administration of anabolic-androgenic steroids and "fat-burning drugs" during a 6-month competition preparation period. The physiological, biochemical, and anthropometric parameters studied included serum cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, aspartate aminotransferase, alanine transaminase, bilirubin, body mass, and percentage of total body fat. Changes in the parameters studied were analyzed at monthly intervals during six months of preparation for competition. The study revealed a continuous increase in body mass, accompanied by a decrease in body fat percentage to the physiologically essential level. Total cholesterol levels remined in the desirable concentration range. The mean levels of triglycerides fluctuated between borderline high and high. Mean high-density lipoprotein cholesterol levels remained within the low range, while low-density lipoprotein cholesterol fluctuated between near-optimal / above-optimal, borderline high, and high levels. Serum levels of aspartate aminotransferase and alanine transaminase remained within the high concentration. The bilirubin concentration remained in the desirable range. The blood nitrogen urea concentration fluctuated between normal and elevated levels. Sports-enhancing drugs analyzed in this study do not have an immediate detrimental impact on the selected biochemical, physiological, and anthropometric parameters that define health.

GLL398, an oral selective estrogen receptor degrader (SERD), blocks tumor growth in xenograft breast cancer models

PURPOSE

Selective estrogen receptor degrader (SERD) has proven clinically effective in treating advanced or metastatic breast cancer since the approval of fulvestrant by FDA in 2002. Recent expansion of indications as a first line monotherapy and as combination therapy with CDK4/6 inhibitors further extends its clinical utility as an efficacious breast cancer endocrine regimen. However, the poor pharmacokinetic properties of fulvestrant and its injection-only administration route has driven continued efforts to develop orally bioavailability SERD that could potentially improve clinical response to SERD treatment. GLL398, a boron-modified GW5638 analog, showed superior oral bioavailability, while retaining both antiestrogenic activity and ER degrading efficacy at a potency level comparable to the more active metabolite of GW5638, GW7604.

METHODS

Here we used molecular modeling, ER (Y537S) binding assay, MCF-7 Xenograft tumor, and patient-derived xenograft (PDX) tumor model to conduct further studies on the pharmacology and metabolism of GLL398.

RESULTS

Consistent with GLL398's robust activities in breast cancer cells that either are tamoxifen resistant or express constitutively active, mutant ESR1 (Y537S), it was found to bind the mutant ER^Y537S with high affinity. Molecular modeling of the binding mode of GLL398 to ER also found its molecular interactions consistent with the experimentally determined high binding affinity towards WT ER and ER^Y537S. To test the in vivo efficacy of GLL398, mice bearing MCF-7-derived xenograft breast tumors and patient-derived xenograft tumors harboring ER^Y537S were treated with GLL398 which potently inhibited tumor growth in mice.

CONCLUSIONS

This study demonstrates GLL398 is an oral SERD that has therapeutic efficacy in clinically relevant breast tumor models.

Selective Estrogen-Receptor Modulators and Aromatase Inhibitors: Promising New Medical Therapies for Endometriosis?

Endometriosis is an estrogen-dependent disease and estrogen-related pathways are imbalanced in women with endometriosis. One of the key enzymes in estrogen synthesis is aromatase. Inhibiting this pathway at several points is a promising idea for the treatment of endometriosis. The third generation of aromatase inhibitors is becoming more potent in efficacy, with fewer side effects than previous generations, but cotreatment with other hormones is needed to inhibit ovarian stimulation. Other components that promote estrogen synthesis such as COX-2 can also be potentially targeted. Selective estrogen-receptor modulators could also be interesting in view of their tissue-specific effect. However, all these new drugs are still in an early phase of development. At present, it is too early to conclude that aromatase inhibitors, COX-2 inhibitors or selective estrogen-receptor modulators really present any added value compared with the existing drugs that can be used to achieve hormonal suppression in the medical treatment of endometriosis.

An overview of current and emerging SERMs

Selective estrogen receptor modulators (SERMs) are compounds that exhibit tissue-specific estrogen receptor (ER) agonist or antagonist activity, and are used for various indications, including treatment of breast cancer, osteoporosis, and menopausal symptoms. Endometrial safety has been a key differentiator between SERMs in clinical practice. For example, tamoxifen exhibits ER agonist activity in the uterus, resulting in an increased risk of endometrial hyperplasia and malignancy, whereas raloxifene and bazedoxifene have neutral effects on the uterus. Based on their efficacy and long-term safety, SERMs are increasingly being prescribed for women who cannot tolerate other treatment options and for younger women at an increased risk of fracture who may remain on therapy for long periods of time. Continuing advances in the understanding of SERM mechanisms of action and structural interactions with the ER may lead to the development of new agents and combinations of agents to provide optimal treatments to meet the varying needs of postmenopausal women. One such example is the tissue selective estrogen complex, which partners a SERM with 1 or more estrogens, with the aim of blending the desired estrogen-receptor agonist activities of estrogens on vasomotor symptoms, vulvar-vaginal atrophy, and loss of bone mass with the tissue selectivity of a SERM.

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.

Effect of toremifene and ospemifene, compared to acolbifene, on estrogen-sensitive parameters in rat and human uterine tissues

BACKGROUND

Although the first generation selective estrogen receptor modulator (SERM) tamoxifen (TAM) is well known for its uterotrophic activity, this study compares the stimulatory effect of the TAM derivatives toremifene (TORE) and ospemifene (OSPE) on estrogen-sensitive parameters in rat and human uterine tissues.

MATERIAL AND METHODS

Ovariectomized female rats were treated daily orally for 10 days with 0.75 mg/rat of TORE, OSPE or acolbifene (ACOL, a pure estrogen antagonist in the uterus and mammary gland), which was used for comparison. Human endometrial carcinoma Ishikawa cells were incubated for 5 days with increasing doses of compounds, in the absence or presence of 1 nM estradiol (E2).

RESULTS

TORE and OSPE revealed 52% and 56% increases, respectively, in uterine weight, whereas ACOL had no effect. Similar effects were observed on vaginal weight. Endometrial epithelial height increased from 15.82±0.20 to 48.94± 2.12 and 42.14±1.95 μm with TORE and OSPE, respectively, whereas ACOL had no effect. Alkaline phosphatase activity, an estrogen-sensitive parameter in Ishikawa cells, was increased by 144% and 135% with OH-TORE and OH-OSPE, respectively. Owing to their intrinsic estrogenic activity, at maximal concentrations, OH-TORE and OH-OSPE blocked the stimulatory effect of E2 by only 89% compared to 100% with ACOL.

CONCLUSIONS

The present in vitro and in vivo data show similar stimulatory effects of 4-hydroxytoremifene (OH-TORE) and OH-OSPE on estrogen-sensitive parameters. ACOL, a third generation SERM, has no effect on any of these parameters. Such data add to the potential uterine safety limitations of triphenylethylene-derived SERMs for long-term use in humans.

Comparative effects of estradiol, methyl-piperidino-pyrazole, raloxifene, and ICI 182 780 on gene expression in the murine uterus

Selective estrogen receptor modulators (SERMs) are potentially useful in treating various endometrial disorders, including endometrial cancer, as they block some of the detrimental effects of estrogen. It remains unclear whether each SERM regulates a unique subset of genes and, if so, whether the combination of a SERM and 17beta-estradiol has an additive or synergistic effect on gene expression. We performed microarray analysis with Affymetrix Mouse Genome 430 2.0 short oligomer arrays to determine gene expression changes in uteri of ovariectomized mice treated with estradiol (low and high dose), methyl-piperidino-pyrazole (MPP), ICI 182 780, raloxifene, and combinations of high dose of estradiol with one of the SERM and dimethyl sulfoxide (DMSO) vehicle control. The nine treatments clustered into two groups, with MPP, raloxifene, and high dose of estradiol in one, and low dose of estradiol, ICI + estradiol, ICI, MPP + estradiol, and raloxifene + estradiol in the second group. Surprisingly, combining a high dose of estradiol with a SERM markedly increased (P<0.02) the number of regulated genes compared with each individual treatment. Analysis of expression for selected genes in uteri of estradiol and SERM-treated mice by quantitative (Q)RT-PCR generally supported the microarray results. For some cancer-associated genes, including Klk1, Ihh, Cdc45l, and Cdca8, administration of MPP or raloxifene with estradiol resulted in greater expression than estradiol alone (P<0.05). By contrast, ICI 182 780 suppressed more genes governing DNA replication compared with MPP and raloxifene treatments. Therefore, ICI 182 780 might be superior to MPP and raloxifene to treat estrogen-induced endometrial cancer in women.

Selective estrogen receptor modulators (SERMS)

Hormone receptors and, specifically, estrogen receptors were described about four decades ago. For estrogens, there are two receptors, estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta). The two receptors are coded by different genes and their tissue expression varies across organs. ERalpha is predominantly expressed in reproductive tissues (uterus, breast, ovaries) liver and central nervous system, whereas ERbeta is expressed in other tissues such as bone, endothelium, lungs, urogenital tract, ovaries, central nervous system and prostate. More than seventy molecules that belong to the SERMS class have been described. There are 5 chemical groups: triphenylethylenes, benzotiophenes, tetrahydronaphtylenes, indoles and benzopyrans. All of these non-hormonal compounds are capable of activating the ER, reduce bone turnover rate and, as an antiresorptive, clearly improve bone density. Estrogens reduce bone turnover rate and, as an antiresorptive, clearly improve bone density. They are also beneficial for the relief of menopausal symptoms. An ongoing debate that extends over the decades, relates to to overall benefit/risk profile of estrogen or estrogen-progestin therapy since these therapies can increase the risk of serious health disorders, such as breast cancer. SERMs have increased our understanding of hormone-receptor regulatory mechanisms. Their development has permitted a targeted efficacy profile avoiding some of the side effects of the hormone therapy. Their clinical utility relies today mostly on the effects on breast cancer and bone.

Drug Insight: breast cancer prevention and tissue-targeted hormone replacement therapy

The first-generation selective estrogen receptor modulator (SERM) tamoxifen has been the mainstream hormone therapy in breast cancer. Tamoxifen benefits all stages of the disease, but its use increases the risk of uterine cancer and thromboembolic events and it can only be administered for 5 years. Aromatase inhibitors are superior to tamoxifen at advanced stages of disease and as adjuvants; however, because they increase fractures, aromatase inhibitors are unlikely to be used to prevent disease. Raloxifene, a second-generation SERM, leads, like tamoxifen, to approximately 50% fewer cases of invasive breast cancer in high risk women, with a lower incidence of thromboembolic events. Several other SERMs are in development to improve tissue specificity, efficacy and tolerance. Raloxifene shows protection against vertebral fractures similar to bisphosphonates; however, no significant effect has been observed on nonvertebral fractures. Many SERMs are in development for prevention and treatment of osteoporosis. As breast cancer metastasizes early and advanced disease cannot be cured, prevention is essential. To avoid the concerns about the use of traditional hormone replacement therapy, dehydroepiandrosterone--a tissue-targeted precursor of sex steroid formation--offers hope of a physiological tissue-targeted hormone replacement that, combined with a SERM, would simultaneously prevent breast and uterine cancer.

The combination of the rexinoid, LG100268, and a selective estrogen receptor modulator, either arzoxifene or acolbifene, synergizes in the prevention and treatment of mammary tumors in an estrogen receptor-negative model of breast cancer

PURPOSE

We tested whether a selective estrogen receptor modulator (SERM) and a rexinoid are active for prevention and treatment in the mouse mammary tumor virus-neu mouse model of estrogen receptor-negative breast cancer.

EXPERIMENTAL DESIGN

For prevention, mice were fed a powdered control diet, the SERM arzoxifene (Arz, 20 mg/kg diet), the rexinoid LG100268 (268, 30 mg/kg diet), or the combination for 60 weeks. In a second prevention study, mice were fed Arz (6 mg/kg diet), 268 (30 mg/kg diet), the combination of Arz and 268, the SERM acolbifene (Acol, 3 mg/kg diet), or the combination of Acol and 268 for 52 weeks. For the treatment studies, mice with tumors were fed combinations of a SERM and 268 for 4 weeks.

RESULTS

The rexinoid 268 and the SERMs Arz and Acol, as individual drugs, delayed the development of estrogen receptor-negative tumors. Moreover, the combination of a SERM and 268 was strikingly synergistic, as no tumors developed in any mouse fed the combination of 268 and a SERM. Moreover, this drug combination also induced significant tumor regression when used therapeutically. These drugs did not inhibit transgene expression in vitro or in vivo, and the combination of Arz and 268 inhibited proliferation and induced apoptosis in the tumors.

CONCLUSION

The combination of a rexinoid and SERM should be considered for future clinical trials.

The effects of atamestane and toremifene alone and in combination compared with letrozole on bone, serum lipids and the uterus in an ovariectomized rat model

We compared the effects of atamestane (ATA) and toremifene (TOR) alone and in combination, with letrozole (LET) on bone, serum lipids and the uterus in ovariectomized (OVX) rats after 16 weeks of treatment. Compared to OVX controls lumbar vertebral and femoral BMD as well as mechanical strength and trabecular bone volume were significantly greater in animals given ATA, TOR or ATA + TOR. The effects of ATA were not reversed by the androgen receptor blocker, flutamide (FLT). Serum cholesterol, low-density lipoprotein cholesterol and triglycerides were reduced by TOR and ATA + TOR whereas they remained unchanged in animals receiving ATA, ATA + FLT, and LET. The uterine epithelium in OVX animals was equally stimulated by TOR and ATA + TOR and unaffected by ATA or LET. Intact animals had significant atrophy of the uterine epithelium when receiving ATA. In summary, TOR alone or in combination with ATA had a predictable stimulatory effect on bone and the uterine epithelium while reducing key parameters of lipid metabolism. In contrast, ATA but not LET had an unexpected stimulatory effect on the OVX rat's bone and this was not reversed by the anti-androgen FLT leaving this finding unexplained for now. ATA is distinct from LET on end-organ function and this favorable profile makes clinical testing of this steroidal aromatase inhibitor of interest in the clinical setting.

Effects of raloxifene on normal breast tissue from premenopausal women

The objective of this study was to evaluate the effects of raloxifene on normal breast tissue. A randomized, double-blind study was carried out in 30 ovulatory, premenopausal women of 18-40 years of age, who had been diagnosed with fibroadenoma of the breast. The patients were divided into two groups: Group A (placebo, n = 16) and Group B (raloxifene 60 mg, n = 14). The medication was given for 22 days, beginning on the first day of the menstrual cycle. An excisional biopsy was carried out on the 23rd day during which a sample of normal breast tissue was collected to evaluate the presence of the proliferating cell marker Ki-67. Student's t-test was used for the statistical analysis of data (p < 0.05). Mean percentage of stained nuclei in groups A and B was 10.96 +/- 1.27 and 1.21 +/- 0.26, respectively (p < 0.001). Raloxifene significantly reduced the proliferative activity of normal breast tissue in premenopausal women.

Selective estrogen receptor modulators (SERMs): mechanisms of anticarcinogenesis and drug resistance

Despite the beneficial effects of estrogens in women's health, there is a plethora of evidence that suggest an important role for these hormones, particularly 17beta-estradiol (E(2)), in the development and progression of breast cancer. Most estrogenic responses are mediated by estrogen receptors (ERs), either ERalpha or ERbeta, which are members of the nuclear receptor superfamily of ligand-dependent transcription factors. Selective estrogen receptor modulators (SERMs) are ER ligands that in some tissues (i.e. bone and cardiovascular system) act like estrogens but block estrogen action in others. Tamoxifen is the first SERM that has been successfully tested for the prevention of breast cancer in high-risk women and is currently approved for the endocrine treatment of all stages of ER-positive breast cancer. Raloxifene, a newer SERM originally developed for osteoporosis, also appears to have preventive effect on breast cancer incidence. Numerous studies have examined the molecular mechanisms for the tissue selective action of SERMs, and collectively they indicate that different ER ligands induce distinct conformational changes in the receptor that influence its ability to interact with coregulatory proteins (i.e. coactivators and corepressors) critical for the regulation of target gene transcription. The relative expression of coactivators and corepressors, and the nature of the ER and its target gene promoter also affect SERM biocharacter. This review summarizes the therapeutic application of SERMs in medicine; particularly breast cancer, and highlights the emerging understanding of the mechanism of action of SERMs in select target tissues, and the inevitable development of resistance.

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.

Endocrinology and hormone therapy in breast cancer: selective oestrogen receptor modulators and downregulators for breast cancer - have they lost their way?

Although tamoxifen has been an effective treatment for breast cancer, several novel anti-oestrogen compounds have been developed with a reduced agonist profile on breast and gynaecological tissues. These include selective oestrogen receptor modulators (SERMs; both 'tamoxifen-like' and 'fixed-ring' SERMs) and selective oestrogen receptor downregulators (SERDs), although none has been proved superior in efficacy to tamoxifen in various advanced breast cancer trials. Thus, many have questioned whether a need for SERMs in breast cancer still exists, although chemoprevention remains a possible niche setting. In contrast, SERDs may have useful efficacy following aromatase inhibitors because of their unique mechanism of action, and clinical trials to determine their optimal use or sequence are ongoing.

The selective estrogen receptor modulator SCH 57068 prevents bone loss, reduces serum cholesterol and blocks estrogen-induced uterine hypertrophy in ovariectomized rats

Our objective was to determine the effects of SCH 57068 alone and with 17 beta-estradiol (E(2)) on bone, lipids and uteri in ovariectomized (OVX) rats. In OVX animals lumbar vertebral and femoral bone mineral density (BMD) were significantly higher after 12 weeks of treatment with SCH 57068 than in untreated OVX controls. Similarly BMD was superior in OVX + E(2) + SCH 57068 treated animals than in OVX + E(2) controls. SCH 57068 also significantly reduced the increase in bone turnover markers, serum pyridinoline and serum osteocalcin levels, induced by OVX, and increased mechanical bone strength. SCH 57068 also significantly reduced the rise in serum cholesterol and low-density lipoprotein cholesterol induced by OVX. SCH 57068 had no stimulatory effect on uterine epithelium when given alone in OVX rats. SCH 57068 (1 and 2.5 mg/kg) reduced uterine weight and blocked endometrial stimulation induced by E(2). In summary, SCH 57068 adds to the positive effects of E(2) on bone and lipid metabolism but blocks the stimulatory effects of E(2) on the uterus. Potentially, E(2) + SCH 57068 could be combined for the treatment and prevention of breast cancer or as a novel hormone replacement therapy.

The influence of tumor size and environment on gene expression in commonly used human tumor lines

Background

The expression profiles of solid tumor models in rodents have been only minimally studied despite their extensive use to develop anticancer agents. We have applied RNA expression profiling using Affymetrix U95A GeneChips to address fundamental biological questions about human tumor lines.

Methods

To determine whether gene expression changed significantly as a tumor increased in size, we analyzed samples from two human colon carcinoma lines (Colo205 and HCT-116) at three different sizes (200 mg, 500 mg and 1000 mg). To investigate whether gene expression was influenced by the strain of mouse, tumor samples isolated from C.B-17 SCID and Nu/Nu mice were also compared. Finally, the gene expression differences between tissue culture and in vivo samples were investigated by comparing profiles from lines grown in both environments.

Results

Multidimensional scaling and analysis of variance demonstrated that the tumor lines were dramatically different from each other and that gene expression remained constant as the tumors increased in size. Statistical analysis revealed that 63 genes were differentially expressed due to the strain of mouse the tumor was grown in but the function of the encoded proteins did not link to any distinct biological pathways. Hierarchical clustering of tissue culture and xenograft samples demonstrated that for each individual tumor line, the in vivo and in vitro profiles were more similar to each other than any other profile. We identified 36 genes with a pattern of high expression in xenograft samples that encoded proteins involved in extracellular matrix, cell surface receptors and transcription factors. An additional 17 genes were identified with a pattern of high expression in tissue culture samples and encoded proteins involved in cell division, cell cycle and RNA production.

Conclusions

The environment a tumor line is grown in can have a significant effect on gene expression but tumor size has little or no effect for subcutaneously grown solid tumors. Furthermore, an individual tumor line has an RNA expression pattern that clearly defines it from other lines even when grown in different environments. This could be used as a quality control tool for preclinical oncology studies.

Activity and Safety of the Antiestrogen EM-800, the Orally Active Precursor of Acolbifene, in Tamoxifen-Resistant Breast Cancer

Purpose

To determine the efficacy and safety of EM-800 (SCH-57050), the precursor of acolbifene, a new, highly potent, orally active, pure antiestrogen in the mammary gland and endometrium, for the treatment of tamoxifen-resistant breast cancer.

Patients and Methods

Forty-three post menopausal/ovariectomized women with breast cancer who had received tamoxifen, either for metastatic disease or as adjuvant to surgery for ≥ 1 year, and had relapsed were treated in a prospective, multicenter, phase II study with EM-800 (20 mg/d [n = 21] or 40 mg/d [n = 22] orally).

Results

Thirty-seven patients had estrogen receptor (ER)-positive tumors (>10 fmol/mg; mean, 146 fmol/mg cytosolic protein), three patients had ER-negative/progesterone receptor-positive tumors, and three patients had undetermined ER status. The objective response rate to EM-800 was 12%, with one complete response and four partial responses. Ten patients (23%) had stable disease for ≥ 3 months, and 7 patients (16%) had stable disease for ≥ 6 months. With a median follow-up of 29 months, median duration of response was 8 months (range, 7 to 71+ months). Treatment with EM-800 was well tolerated. No significant adverse events related to the study drug were observed clinically or biochemically.

Conclusion

EM-800 produced responses in a significant proportion of patients with tamoxifen-resistant breast cancer, thus showing that this highly potent, selective estrogen receptor modulator, which lacks estrogenic activity in the mammary gland and endometrium, has incomplete cross-resistance with tamoxifen, thus suggesting additional benefits in the treatment of breast cancer.

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.

A Novel Pure SERM Achieves Complete Regression of the Majority of Human Breast Cancer Tumors in Nude Mice

BACKGROUND

The objective was to determine if EM-652, a novel selective estrogen receptor modulator (SERM) having highly potent and pure antiestrogenic activity in the mammary gland could cause complete regression of the majority of human breast cancer xenografts in nude mice.

METHODS

Human breast cancer ZR-75-1 xenografts were used as model in nude mice.

RESULTS

EM-652 not only prevented estrogen-induced tumor growth but it reduced tumor size to 20% of the pretreatment value. Complete disappearance of the tumors was observed in 65% (106/163) of tumors. No tumor progressed. Most importantly, 93% of the tumors which had become undetectable under EM-652 treatment did not reappear when exposed to estrogen challenge for 12 weeks, thus achieving an overall 61% cure rate.

CONCLUSIONS

The present data demonstrate that EM-652 is strongly cytotoxic or tumorocidal and not only cytostatic or tumorostatic in estrogen-sensitive breast cancer, thus changing the paradigm of a tumorostatic role of estrogen blockade established with tamoxifen. These findings support the use of such a compound for more efficient breast cancer prevention and therapy.

Prevention of breast cancer using SERMs and aromatase inhibitors

Breast cancer is one of the most common cancers of women in the Western world. Despite modest achievements in the treatment of this disease, there is a substantial unmet medical need to reduce the occurrence of new breast cancers. In several prospective, placebo-controlled trials, the antiestrogen tamoxifen has been shown to reduce the incidence of both invasive cancer and preinvasive breast lesions. Meanwhile, numerous other selective estrogen receptor modulators (SERMs) are being developed and trials comparing tamoxifen to these agents are ongoing. The goal of these studies is not only to show superior chemopreventive efficacy of the newer SERMs, but also an improved side-effect profile. The proof-of-principle demonstrated with tamoxifen suggests that strategies inhibiting estrogen are a logical way forward in breast cancer prevention. Aromatase inhibitors, which antagonize estrogen by blocking its synthesis from androgens, offer an alternative way of preventing the effects of estrogen and its metabolites on the breast. In this paper, the available data on SERMs including tamoxifen and raloxifene in breast cancer prevention and the data pointing to the efficacy of aromatase inhibitors in this setting are outlined.