Long-term toxicities of selective estrogen-receptor modulators and antiaromatase agents

Published literature indicates that the selective estrogen-receptor modulators (SERMs) tamoxifen and raloxifene (Evista) have favorable effects on bone density, lipid profiles, and the incidence of second breast cancers, and unfavorable effects on the incidence of venous thrombosis and hot flushes. Tamoxifen increases the risk of endometrial cancer, but raloxifene does not. The effects of SERMs on sexual function and cognition are unclear. Because the selective antiaromatase agents are relatively new, the long-term effects of these agents on normal tissues are less well established. It appears that the nonsteroidal agents (anastrozole [Arimidex], letrozole [Femara]) and steroidal (exemestane [Aromasin]) antiaromatase agents may have different effects on normal tissues. Preliminary data demonstrate that anastrozole increases the risk of arthralgias and produces a decrease in bone density. In contrast, exemestane appears to favorably affect bone density and lipid profile, similar to tamoxifen and raloxifene. The incidence of contralateral breast cancer is decreased in women on adjuvant anastrozole, but data for the other antiaromatase agents are not yet available. Hot flushes have been reported with the use of selective aromatase inhibitors, but their incidence seems to be comparable to what is reported with SERMs. Antiaromatase agents do not appear to cause venous thrombosis. More information about the effects of the antiaromatase agents on normal tissue will become available as data from ongoing adjuvant and chemoprevention trials are reported. Clinically, we should be conscious of the differences between antiaromatase agents and SERMs and their impact on women's health.     

Safety profiles of aromatase inhibitors and selective estrogen-receptor modulators in the treatment of early breast cancer

For the medical treatment of early breast cancer, aromatase inhibitors (AIs) such as anastrozole, letrozole, and exemestane are more effective than selective estrogen-receptor modulators (SERMs) such as tamoxifen (TAM). However, the adverse events associated with AIs are different from those associated with SERMs. Hot flushes, gynecological disorders, and thrombosis are more frequent in patients treated with TAM than in those treated with AIs. Conversely, osteoporosis, fractures, joint symptoms, and myalgia are more common in patients receiving AIs. Osteoporosis and bone fractures resulting from osteoporosis are important issues for patients treated with AIs. The precise management of bone health, in strict accordance with clinical guidelines, is vital in patients receiving AIs. AI-related joint symptoms are also one of the most important considerations for patients taking AIs. AI-related joint symptoms are the most common reason for the discontinuation of AIs. Confirmed management strategies for AI-related joint symptoms are unavailable at present. In patients receiving AIs, long-term adverse events (for example, those occurring as a result of changing lipid metabolism) remain unclear. There is a clear need to elucidate AI-related adverse events over the long term and to establish management strategies for AI-related adverse events, such that AIs can be used safely in patients with breast cancer over long periods of time.     

Selective oestrogen receptor modulators/new antioestrogens: a clinical perspective

Following tamoxifen, the first selective oestrogen receptor modulator (SERM), a number of other antioestrogens have been developed. The first-generation SERMs exhibit cross-resistance with tamoxifen and have agonist effects on the uterus. Toremifene has equal efficacy to tamoxifen and may be useful as a tamoxifen alternative. Efficacy results for droloxifene and idoxifene were disappointing and their clinical development ceased. Response rates for second-generation SERMs such as raloxifene and arzoxifene are also not high, although raloxifene shows promise in the chemoprevention of breast cancer. Paradoxically, high-dose oestrogens are proving to be effective breast cancer treatment with similar responses to tamoxifen in postmenopausal women with advanced disease, although these drugs are not well tolerated. Fulvestrant is a new type of oestrogen receptor (ER) antagonist with no agonist effects, which binds, blocks and degrades the ER. Fulvestrant produces high response rates compared with the SERMs, is not cross-resistant with SERMs or aromatase inhibitors (AIs) and is equally as effective as the AI anastrozole in the treatment of postmenopausal women with advanced breast cancer who have progressed after prior antioestrogen therapy. Pure antioestrogens such as the ER antagonist fulvestrant provide opportunities for therapeutic sequencing with tamoxifen and AIs and offer exciting possibilities for the future treatment of breast cancer.     

Selective estrogen receptor modulators as a new therapeutic drug group: concept to reality in a decade

This article provides an overview of the historical development, current research, clinical benefits, and potential future applications of the selective estrogen receptor modulators (SERMs), tamoxifen and raloxifene. The understanding of the mechanism of action of SERMs led not only to the development of tamoxifen, the first widely used antiestrogen for breast cancer treatment, but also to its application as a chemopreventive agent. The SERM principle of antiestrogenic actions in the breast but estrogenlike actions in bone is reviewed in clinical practice through analysis of the current applications and the potential for expanding the role of SERMs. The current view of the molecular mechanism of SERM action is summarized to identify potential target sites for future research. The clinical success of tamoxifen and raloxifene for the prevention and treatment of breast cancer and osteoporosis, respectively, has encouraged the development of a range of new agents that target breast cancer, osteoporosis, coronary heart disease, and endometrial safety.     

Melatonin modulation of estrogen-receptor expression in mcf-7 human breast-cancer cells

MCF-7 human breast cancer cells, which are estrogen receptor (ER)-positive and responsive to the mitogenic actions of estrogen, were used to examine the possible association between the growth-inhibitory activity of melatonin and its ability to modulate the estrogen-response pathway. Melatonin at physiologic concentrations (10(-8)-10(-11) M) significantly decreased estrogen binding activity and the expression of immunoreactive ER in a dose-specific and time-dependent manner. However, melatonin did not alter receptor affinity and was unable to compete with estrogen for binding to the ER. Studies in a yeast trancriptional assay system confirmed that melatonin does not directly bind to the ER to modulate ER expression. Thus, it appears that the antimitotic actions of melatonin may be mediated, at least in part, through the suppression of the estrogen-response pathway of MCF-7 cells.     

Coffee consumption modifies risk of estrogen-receptor negative breast cancer

Introduction  

Breast cancer is a complex disease and may be sub-divided into hormone-responsive (estrogen receptor (ER) positive) and non-hormone-responsive subtypes (ER-negative). Some evidence suggests that heterogeneity exists in the associations between coffee consumption and breast cancer risk, according to different estrogen receptor subtypes. We assessed the association between coffee consumption and postmenopausal breast cancer risk in a large population-based study (2,818 cases and 3,111 controls), overall, and stratified by ER tumour subtypes.     

Selective estrogen receptor modulators: discrimination of agonistic versus antagonistic activities by gene expression profiling in breast cancer cells

Selective estrogen receptor modulators (SERMs) such as tamoxifen are effective in the treatment of many estrogen receptor-positive breast cancers and have also proven to be effective in the prevention of breast cancer in women at high risk for the disease. The comparative abilities of tamoxifen versus raloxifene in breast cancer prevention are currently being compared in the Study of Tamoxifen and Raloxifene trial. To better understand the actions of these compounds in breast cancer, we have examined their effects on the expression of approximately 12,000 genes, using Affymetrix GeneChip microarrays, with quantitative PCR verification in many cases, categorizing their actions as agonist, antagonist, or partial agonist/antagonist. Analysis of gene stimulation and inhibition by the SERMs trans-hydroxytamoxifen (TOT) and raloxifene (Ral) or ICI 182,780 (ICI) and by estradiol (E2) in estrogen receptor-containing MCF-7 human breast cancer cells revealed that (a) TOT was the most E2-like of the three compounds, (b) all three compounds either partially or fully antagonized the action of E2 on most genes, with the order of antagonist activity being ICI > Ral > TOT, (c) TOT and Ral, but not ICI, displayed partial agonist/partial antagonist activity on a number of E2-regulated genes, (d) several stimulatory cell cycle-related genes were down-regulated exclusively by ICI, (e) the estrogen-like activity of Ral nearly always overlapped with that of TOT, indicating that Ral has little unique agonist activity different from that of TOT, and (f) some genes were specifically up-regulated by TOT but not Ral, ICI, or E2. Hence, gene expression profiling can discern fundamental differences among SERMs and provides insight into the distinct biologies of TOT, Ral, and ICI in breast cancer.     

Selective estrogen receptor modulators inhibit growth and progression of premalignant lesions in a mouse model of ductal carcinoma in situ

Introduction

Ductal carcinoma in situ (DCIS) is a noninvasive premalignant lesion and is considered a precursor to invasive carcinoma. DCIS accounts for nearly 20% of newly diagnosed breast cancer, but the lack of experimentally amenable in vivo DCIS models hinders the development of treatment strategies. Here, we demonstrate the utility of a mouse transplantation model of DCIS for chemoprevention studies using selective estrogen receptor modulators (SERMs). This model consists of a set of serially transplanted lines of genetically engineered mouse mammary intraepithelial neoplasia (MIN) outgrowth (MIN-O) tissue that have stable characteristics. We studied the ovarian-hormone-responsiveness of one of the lines with a particular focus on the effects of two related SERMs, tamoxifen and ospemifene.

Methods

The estrogen receptor (ER) status and ovarian-hormone-dependence of the mouse MIN outgrowth tissue were determined by immunohistochemistry and ovarian ablation. The effects of tamoxifen and ospemifene on the growth and tumorigenesis of MIN outgrowth were assessed at 3 and 10 weeks after transplantation. The effects on ER status, cell proliferation, and apoptosis were studied with immunohistochemistry.

Results

The MIN-O was ER-positive and ovarian ablation resulted in reduced MIN-O growth and tumor development. Likewise, tamoxifen and ospemifene treatments decreased the MIN growth and tumor incidence in comparison with the control (P < 0.01). Both SERMs significantly decreased cell proliferation. Between the two SERM treatment groups, there were no statistically significant differences in MIN-O size, tumor latency, or proliferation rate. In contrast, the ospemifene treatment significantly increased ER levels while tamoxifen significantly decreased them.

Conclusion

Tamoxifen and ospemifene inhibit the growth of premalignant mammary lesions and the progression to invasive carcinoma in a transplantable mouse model of DCIS. The inhibitory effects of these two SERMs are similar except for their effects on ER modulation. These differences in ER modulation may suggest different mechanisms of action between the two related SERMs and may portend different long-term outcomes. These data demonstrate the value of this model system for preclinical testing of antiestrogen or other therapies designed to prevent or delay the malignant transformation of premalignant mammary lesions in chemoprevention.     

Selective estrogen receptor modulators as inhibitors of repopulation of human breast cancer cell lines after chemotherapy.

PURPOSE: Repopulation of surviving tumor cells between courses of chemotherapy might lead to effective drug resistance. Here we study inhibition of repopulation of hormone-responsive human breast cancer cell lines by selective estrogen receptor (ER) modulators (SERMs) during courses of chemotherapy. EXPERIMENTAL DESIGN: Hormone responsive breast cancer cell lines MCF-7 and T47D, and the ER- cell line MDA-231, were treated with either 4-hydroxy tamoxifen (4OHT) or arzoxifene during weekly courses of treatment with 5-fluorouracil (5-FU) or methotrexate (MTX). Clonogenic assays were performed to determine the overall survival of tumor cells after treatment with the SERMs alone, after one to three doses of 5-FU or MTX alone, and after 5-FU or MTX followed by each of the SERMs. RESULTS: Both SERMs inhibited the growth of ER+ cells MCF-7 and T47D but had no effect on the ER-cell line MDA-231. Arzoxifene was more effective than 4OHT. Between courses of treatment with either 5-FU or MTX, repopulation of ER+ cells was specifically inhibited by the SERMs, whereas repopulation of ER- MDA-231 was not affected. CONCLUSIONS: Arzoxifene and 4OHT can inhibit specifically the repopulation of ER+ breast cancer cells between courses of chemotherapy. Scheduling of short-acting SERMs between courses of chemotherapy has the potential to improve therapeutic index.     

Body-size indicators and risk of breast cancer according to menopause and estrogen-receptor status

Associations between the risk of breast cancer and body-size indicators at the time of breast-cancer diagnosis were assessed among 328 pre-menopausal or post-menopausal cases and 417 controls participating in the Kuopio Breast Cancer Study. This case-control study follows the protocol of the international Collaborative Study of Breast and Colorectal Cancer. When the potential confounding factors were taken into account, tallness was related to increased risk of breast cancer, especially in post-menopausal women, whereas no clear association with body-mass index (BMI) was found. Waist-to-hip ratio (WHR) was the most important risk factor in both pre-menopausal and post-menopausal women. The post-menopausal cases with high positive estrogen-receptor status (ER⁺⁺) had the highest weight and BMI; they had also the biggest weight gain since the age of 20. However, the association between WHR and breast cancer appeared to be independent of estrogen-receptor status. Our results suggest that WHR may be a better marker for breast cancer than the degree of adiposity. © 1996 Wiley-Liss, Inc.     

Increased expression of estrogen-receptor exon-5-deletion variant in relapse tissues of human breast cancer

A substantial percentage (30–70%) of human breast carcinomas that initially respond to endocrine therapy acquire resistance during the treatment. Many patients with tumor progression despite treatment with anti-estrogen tamoxifen show continued expression of estrogen receptors (ER) and/or progesterone receptors (PgR) in the relapse tissue. This indicates that, in these tumors, mechanisms other than loss of ER expression are responsible for treatment failure. We have investigated the occurrence and frequency of the exon-5-deletion variant (d5) of ER in human breast-cancer biopsies and in normal tissues. In all normal and tumor tissues tested, both wild-type (wt) and d5 were detected, indicating that expression of the d5 variant is a naturally occurring polymorphism. However, the primary tumors of patients who relapse within 15 months (n = 13) express higher ratios of d5 than do those of patients with no relapse during the same period (p = 0.4, n = 19), though this difference is statistically not significant. A significant increase in the expression level of d5 was determined in relapse as compared with the respective primary tumor (p = 0.02). These data indicate that increased expression of the ER exon-5-deletion variant in relapse tissues might be due to clonal selection of cells resistant to anti-estrogen treatment. Int. J. Cancer (Pred. Oncol.) 79:44–48, 1998. © 1998 Wiley-Liss, Inc.     

Protease inhibitor antipain reduces nuclear binding of estrogen-receptor complex in MCF-7 breast tumor cells

We have initiated studies to ascertain the effects of proteaseinhibitors on specific steroid hormonal-related events as theyoccur in cultured cells, in an attempt to identify hormone-relatedprocesses perturbed by these inhibitors. We report here thatthe presence of antipain during incubation of cultured MCF-7breast tumor cells with estradiol-containing medium considerablyreduces the extent of nuclear binding of the estradiol-receptorcomplex.     

In vitro regulation of vascular endothelial growth factor by estrogens and antiestrogens in estrogen-receptor positive breast cancer

BACKGROUND: The effects of antiestrogens on angiogenesis in breast cancer are not fully defined. In this study we investigated the in vitro effects of antiestrogens at different concentrations on vascular endothelial growth factor (VEGF) production in estrogen receptor (ER)-positive breast cancer cells. METHODS: The dose-dependent effects of 17beta-estradiol (E2), 4-hydroxytamoxifen (4OHT), and ICI182,780 were analyzed both with reference to growth rates and VEGF protein production using enzyme-linked immunosorbent assay (ELISA) in MCF-7 cells. RESULTS: E2 stimulated both the growth rates and VEGF production of MCF-7 cells in the same manner. Although 4OHT stimulated the growth rates as an agonistic effect in an estrogen-free media at levels ranging from 1 nM to 1 micro M, it did not stimulate VEGF expression at the same levels except for at 1 micro M. Although 4OHT had a weak agonistic effect on VEGF production at 1 micro M in an estrogen-free media, it significantly inhibited E2-stimulated VEGF production at the same level. A cytotoxic effect was observed with 10 micro M 4OHT that paradoxically caused a prominent increase in VEGF production. ICI182,780 had no significant effects on the growth rates or VEGF production in this cell line. CONCLUSIONS: These results support the hypothesis that tamoxifen could inhibit angiogenesis induced by estrogens in ER-positive breast cancer cells.     

Galectins as modulators of tumour progression

Galectins are a family of animal lectins with diverse biological activities. They function both extracellularly, by interacting with cell-surface and extracellular matrix glycoproteins and glycolipids, and intracellularly, by interacting with cytoplasmic and nuclear proteins to modulate signalling pathways. Current research indicates that galectins have important roles in cancer; they contribute to neoplastic transformation, tumour cell survival, angiogenesis and tumour metastasis. They can modulate the immune and inflammatory responses and might have a key role helping tumours to escape immune surveillance. How do the different members of the Galectin family contribute to these diverse aspects of tumour biology?