From adjuvant therapy to breast cancer prevention: BCPT and STAR

Drug Repurposing, a Fast-Track Approach to Develop Effective Treatments for Glioblastoma

Glioblastoma (GBM) remains one of the most difficult tumors to treat. The mean overall survival rate of 15 months and the 5-year survival rate of 5% have not significantly changed for almost 2 decades. Despite progress in understanding the pathophysiology of the disease, no new effective treatments to combine with radiation therapy after surgical tumor debulking have become available since the introduction of temozolomide in 1999. One of the main reasons for this is the scarcity of compounds that cross the blood-brain barrier (BBB) and reach the brain tumor tissue in therapeutically effective concentrations. In this review, we focus on the role of the BBB and its importance in developing brain tumor treatments. Moreover, we discuss drug repurposing, a drug discovery approach to identify potential effective candidates with optimal pharmacokinetic profiles for central nervous system (CNS) penetration and that allows rapid implementation in clinical trials. Additionally, we provide an overview of repurposed candidate drug currently being investigated in GBM at the preclinical and clinical levels. Finally, we highlight the importance of phase 0 trials to confirm tumor drug exposure and we discuss emerging drug delivery technologies as an alternative route to maximize therapeutic efficacy of repurposed candidate drug.

Cancer Chemoprevention: Preclinical In Vivo Alternate Dosing Strategies to Reduce Drug Toxicities

Cancer chemopreventive agents inhibit the formation of precursor lesions and/or the progression of these lesions to late stage disease. This approach to disease control has the potential to reduce the physical and financial costs of cancer in society. Several drugs that have been approved by the FDA for other diseases and have been extensively evaluated for their safety and pharmacokinetic/pharmacodynamic characteristics have the potential to be repurposed for use as cancer chemopreventive agents. These agents often mechanistically inhibit signaling molecules that play key roles in the carcinogenic process. The safety profile of agents is a primary concern when considering the administration of drugs for chemoprevention, as the drugs will be given chronically to high-risk, asymptomatic individuals. To decrease drug toxicity while retaining efficacy, several approaches are currently being explored. In this short review, we describe studies that use preclinical in vivo models to assess efficacy of alternative drug dosing strategies and routes of drug administration on chemopreventive drug efficacy. In vivo drug dosing strategies that reduce toxicity while retaining efficacy will pave the way for future cancer prevention clinical trials.

Risk of developing breast cancer by utilizing Gail model

The Gail model has been widely used to quantify an individual woman's risk of developing breast cancer by using important clinical parameters, usually for clinical counselling purposes or to determine eligibility for mammography and genetic tests. The aim of the present study was to estimate the five-year and lifetime breast cancer risk among women in Rasht, Iran. In this cross-sectional study, 314 women were evaluated at Alzahra Women Hospital in 2007. Participants were ≥35 years of age without a history of breast cancer. Risk estimation was performed using the computerized Gail model. A five-year risk >1.66% was considered high-risk; 5.1% of women were high-risk. The mean five-year breast cancer risk was 0.8% (SD±1). Mean breast cancer risk up to the age of 90 years (lifetime risk) was 9.0% (SD±3.9%); 16.2% of the participants had a five-year risk higher than the average woman of the same age, and 18.2% had the same risk. Also for the lifetime risk, 11.1% of the women had higher risk and 1.6% had the same risk as the average woman. Routine use of the Gail model is recommended for identifying women at high average risk for increasing the survival of women from breast cancer.

Role of SUMOylation in full antiestrogenicity

The selective estrogen receptor downregulator (SERD) fulvestrant can be used as second-line treatment for patients relapsing after treatment with tamoxifen, a selective estrogen receptor modulator (SERM). Unlike tamoxifen, SERDs are devoid of partial agonist activity. While the full antiestrogenicity of SERDs may result in part from their capacity to downregulate levels of estrogen receptor alpha (ERα) through proteasome-mediated degradation, SERDs are also fully antiestrogenic in the absence of increased receptor turnover in HepG2 cells. Here we report that SERDs induce the rapid and strong SUMOylation of ERα in ERα-positive and -negative cell lines, including HepG2 cells. Four sites of SUMOylation were identified by mass spectrometry analysis. In derivatives of the SERD ICI164,384, SUMOylation was dependent on the length of the side chain and correlated with full antiestrogenicity. Preventing SUMOylation by the overexpression of a SUMO-specific protease (SENP) deSUMOylase partially derepressed transcription in the presence of full antiestrogens in HepG2 cells without a corresponding increase in activity in the presence of agonists or of the SERM tamoxifen. Mutations increasing transcriptional activity in the presence of full antiestrogens reduced SUMOylation levels and suppressed stimulation by SENP1. Our results indicate that ERα SUMOylation contributes to full antiestrogenicity in the absence of accelerated receptor turnover.

Tamoxifen downregulation of miR-451 increases 14-3-3ζ and promotes breast cancer cell survival and endocrine resistance

Many estrogen receptor (ER)-positive breast cancers respond well initially to endocrine therapies, but often develop resistance during treatment with selective ER modulators (SERMs) such as tamoxifen. We have reported that the 14-3-3 family member and conserved protein, 14-3-3ζ, is upregulated by tamoxifen and that high expression correlated with an early time to disease recurrence. However, the mechanism by which tamoxifen upregulates 14-3-3ζ and may promote the development of endocrine resistance is not known. Our findings herein reveal that the tamoxifen upregulation of 14-3-3ζ results from its ability to rapidly downregulate microRNA (miR)-451 that specifically targets 14-3-3ζ. The levels of 14-3-3ζ and miR-451 were inversely correlated, with 14-3-3ζ being elevated and miR-451 being at a greatly reduced level in tamoxifen-resistant breast cancer cells. Of note, downregulation of miR-451 was selectively elicited by tamoxifen but not by other SERMs, such as raloxifene or ICI182,780 (Fulvestrant). Increasing the level of miR-451 by overexpression, which decreased 14-3-3ζ, suppressed cell proliferation and colony formation, markedly reduced activation of HER2, EGFR and MAPK signaling, increased apoptosis, and, importantly, restored the growth-inhibitory effectiveness of SERMs in endocrine-resistant cells. Opposite effects were elicited by miR-451 knockdown. Thus, we identify tamoxifen downregulation of miR-451, and consequent elevation of the key survival factor 14-3-3ζ, as a mechanistic basis of tamoxifen-associated development of endocrine resistance. These findings suggest that therapeutic approaches to increase expression of this tumor suppressor-like miR should be considered to downregulate 14-3-3ζ and enhance the effectiveness of endocrine therapies. Furthermore, the selective ability of the SERM tamoxifen but not raloxifene to regulate miR-451 and 14-3-3ζ may assist in understanding differences in their activities, as seen in the STAR (Study of Tamoxifen and Raloxifene) breast cancer prevention trial and in other clinical trials.

During hormone depletion or tamoxifen treatment of breast cancer cells the estrogen receptor apoprotein supports cell cycling through the retinoic acid receptor α1 apoprotein

Introduction

Current hormonal adjuvant therapies for breast cancer including tamoxifen treatment and estrogen depletion are overall tumoristatic and are severely limited by the frequent recurrence of the tumors. Regardless of the resistance mechanism, development and progression of the resistant tumors requires the persistence of a basal level of cycling cells during the treatment for which the underlying causes are unclear.

Methods

In estrogen-sensitive breast cancer cells the effects of hormone depletion and treatment with estrogen, tamoxifen, all-trans retinoic acid (ATRA), fulvestrant, estrogen receptor α (ER) siRNA or retinoic acid receptor α (RARα) siRNA were studied by examining cell growth and cycling, apoptosis, various mRNA and protein expression levels, mRNA profiles and known chromatin associations of RAR. RARα subtype expression was also examined in breast cancer cell lines and tumors by competitive PCR.

Results

Basal proliferation persisted in estrogen-sensitive breast cancer cells grown in hormone depleted conditioned media without or with 4-hydroxytamoxifen (OH-Tam). Downregulating ER using either siRNA or fulvestrant inhibited basal proliferation by promoting cell cycle arrest, without enrichment for ErbB2/3+ overexpressing cells. The basal expression of RARα1, the only RARα isoform that was expressed in breast cancer cell lines and in most breast tumors, was supported by apo-ER but was unaffected by OH-Tam; RAR-β and -γ were not regulated by apo-ER. Depleting basal RARα1 reproduced the antiproliferative effect of depleting ER whereas its restoration in the ER depleted cells partially rescued the basal cycling. The overlapping tamoxifen-insensitive gene regulation by apo-ER and apo-RARα1 comprised activation of mainly genes promoting cell cycle and mitosis and suppression of genes involved in growth inhibition; these target genes were generally insensitive to ATRA but were enriched in RAR binding sites in associated chromatin regions.

Conclusions

In hormone-sensitive breast cancer, ER can support a basal fraction of S-phase cells (i) without obvious association with ErbB2/3 expression, (ii) by mechanisms unaffected by hormone depletion or OH-Tam and (iii) through maintenance of the basal expression of apo-RARα1 to regulate a set of ATRA-insensitive genes. Since isoform 1 of RARα is genetically redundant, its targeted inactivation or downregulation should be further investigated as a potential means of enhancing hormonal adjuvant therapy.

Breast cancer prevention trials: large and small trials

Breast cancer is the most common cancer among women in the United States, with 192,870 new cases and 40,170 deaths due to this disease estimated to have occurred 2009. An emphasis on prevention has been increasing in view of a persisting high incidence of disease. Seventy percent of breast cancers are estrogen receptor (ER)-positive, and are therefore presumed to be hormone-responsive and potentially treatable or preventable by anti-estrogenic agents. To date, the large, phase III randomized controlled breast cancer prevention trials have tested and are testing only hormonal drugs designed to antagonize the carcinogenic effect of endogenous estrogen; these agents are either selective estrogen receptor modulators (SERMs) or aromatase inhibitors (AIs). The SERMs, tamoxifen and raloxifene, have been shown in these large trials to reduce the risk of ER-positive breast cancers; prevention trials of AIs are ongoing. Interest is now focusing on developing agents with a broader spectrum of preventive activity, particularly with regard to ER-negative subtypes of breast cancer. A number of phase I and II trials using tissue-derived surrogate endpoint biomarkers (SEBs) as outcomes have been implemented. These smaller trials address prevention not only of ER-negative but also ER-positive breast cancers, since approximately 50% of the latter have been shown to be resistant to the estrogen-targeting drugs used in the large trials. Issues of importance in these smaller trials include choice of agent, selection of appropriate trial participants, trial design, method of access to breast tissue in women without cancer, selection and monitoring of SEBs, and monitoring of drug toxicity.

Landmarks in the history of cancer epidemiology

The application of epidemiology to cancer prevention is relatively new, although observations of the potential causes of cancer have been reported for more than 2,000 years. Cancer was generally considered incurable until the late 19th century. Only with a refined understanding of the nature of cancer and strategies for cancer treatment could a systematic approach to cancer prevention emerge. The 20th century saw the elucidation of clues to cancer causation from observed associations with population exposures to tobacco, diet, environmental chemicals, and other exogenous factors. With repeated confirmation of such associations, researchers entertained for the first time the possibility that cancer, like many of the infectious diseases of the time, might be prevented. By the mid-20th century, with antibiotics successfully addressing the majority of infectious diseases and high blood pressure treatment beginning to affect the prevalence of heart disease in a favorable direction, the focus of much of epidemiology shifted to cancer. The early emphasis was on exploring, in greater depth, the environmental, dietary, hormonal, and other exogenous exposures for their potential associations with increased cancer risk. The first major breakthrough in identifying a modifiable cancer risk factor was the documentation of an association between tobacco smoking and lung cancer. During the past four decades, epidemiologic studies have generated population data identifying risk factors for cancers at almost every body site, with many cancers having multiple risk factors. The development of technologies to identify biological molecules has facilitated the incorporation of these molecular manifestations of biological variation into epidemiologic studies, as markers of exposure as well as putative surrogate markers of cancer outcome. This technological trend has, during the past two decades, culminated in emphasis on the identification of genetic variants and their products as correlates of cancer risk, in turn, creating opportunities to incorporate the discipline of molecular/genetic epidemiology into the study of cancer prevention. Epidemiology will undoubtedly continue contributing to cancer prevention by using traditional epidemiologic study designs to address broad candidate areas of interest, with molecular/genetic epidemiology investigations honing in on promising areas to identify specific factors that can be modified with the goal of reducing risk.

Raloxifene in breast cancer prevention

BACKGROUND

Raloxifene is a benzothiophene, selective estrogen receptor modulator with estrogen-agonist effects in the skeleton and the cardiovascular system but estrogen-antagonist effects in the uterus and the mammary gland. This compound was first approved in different countries for the prevention and treatment of osteoporosis.

OBJECTIVE/METHODS

We performed a literature search to review available preclinical and clinical data that has led to the recent FDA approval of raloxifene as a chemopreventive agent for breast cancer in postmenopausal women.

RESULTS/CONCLUSIONS

Different placebo-controlled trials indicated that raloxifene is effective in reducing invasive breast cancer risk in postmenopausal women. In a recent comparative study, a similar efficacy between raloxifene and tamoxifen for breast cancer prevention was demonstrated, but raloxifene showed a more favorable safety profile.

Translational approaches for the prevention of estrogen receptor-negative breast cancer

Breast cancer prevention has focused heavily on endocrine interventions using selective estrogen receptor modulators and aromatase inhibitors. Tamoxifen, the stereotypical selective estrogen receptor modulator, significantly reduces the breast cancer incidence in high-risk women. Selective estrogen receptor modulators and aromatase inhibitors, however, only prevent the development of estrogen receptor-positive breast cancer and have no effect in reducing the risk of estrogen receptor-negative breast cancer, which has poor prognosis. Thus, preventive therapies for estrogen receptor-negative breast cancer are clearly needed. Recently, a number of novel chemopreventive agents targeting nonendocrine pathways have been developed and shown to prevent estrogen receptor-negative mammary tumorigenesis in animal models. These agents include rexinoids, selective cyclooxygenase-2 inhibitors, tyrosine kinase inhibitors, and others. In this review, we discuss the effects of selective estrogen receptor modulators and aromatase inhibitors, as well as novel agents targeting nonendocrine pathways. We also discuss the promise of combining these agents for the effective prevention of all forms of breast cancer.

Hormonal interventions to prevent hormonal cancers: breast and prostate cancers

In 1998, the concept of breast cancer prevention became a reality with the approval of tamoxifen to reduce the risk of developing breast cancer in women at increased risk for the disease. This approval was based on decades of research on selective estrogen receptor modulators providing an understanding of the role of the estrogen receptor in breast cell growth, and an appreciation of the carcinogenic process. Although results from the Breast Cancer Prevention Trial demonstrated a 49% reduction in breast cancer in women at increased risk, there were associated toxicities related to the estrogenic effects of tamoxifen; that is, deep vein thrombosis, pulmonary embolism, and endometrial cancer. In an effort to improve its benefit-risk profile, tamoxifen is now being compared with raloxifene, a selective estrogen receptor modulator approved for the treatment and prevention of osteoporosis. This equivalency prevention Study of Tamoxifen and Raloxifene completed accrual of 19 747 high-risk postmenopausal women in November 2004. Meanwhile, another class of estrogen-directed drugs, the aromatase inhibitors, have shown efficacy in breast cancer adjuvant trials, spawning a number of prevention trials that have recently been initiated. As with breast cancer the hormonal contribution to prostate carcinogenesis was the basis for the Prostate Cancer Prevention Trial which showed that finasteride, an androgen antagonist, reduces the incidence of prostate cancer compared to placebo.

Raloxifene and ICI182,780 increase estrogen receptor-alpha association with a nuclear compartment via overlapping sets of hydrophobic amino acids in activation function 2 helix 12

The basis for the differential repressive effects of antiestrogens on transactivation by estrogen receptor-alpha (ERalpha) remains incompletely understood. Here, we show that the full antiestrogen ICI182,780 and, to a lesser extent, the selective ER modulator raloxifene (Ral), induce accumulation of exogenous ERalpha in a poorly soluble fraction in transiently transfected HepG2 or stably transfected MDA-MB231 cells and of endogenous receptor in MCF7 cells. ERalpha remained nuclear in HepG2 cells treated with either compound. Replacement of selected hydrophobic residues of ERalpha ligand-binding domain helix 12 (H12) enhanced receptor solubility in the presence of ICI182,780 or Ral. These mutations also increased transcriptional activity with Ral or ICI182,780 on reporter genes or on the endogenous estrogen target gene TFF1 in a manner requiring the integrity of the N-terminal AF-1 domain. The antiestrogen-specific effects of single mutations suggest that they affect receptor function by mechanisms other than a simple decrease in hydrophobicity of H12, possibly due to relief from local steric hindrance between these residues and the antiestrogen side chains. Fluorescence anisotropy experiments indicated an enhanced regional stabilization of mutant ligand-binding domains in the presence of antiestrogens. H12 mutations also prevent the increase in bioluminescence resonance energy transfer between ERalpha monomers induced by Ral or ICI182,780 and increase intranuclear receptor mobility in correlation with transcriptional activity in the presence of these antiestrogens. Our data indicate that ICI182,780 and Ral locally alter the ERalpha ligand binding structure via specific hydrophobic residues of H12 and decrease its transcriptional activity through tighter association with an insoluble nuclear structure.

Prospective breast cancer risk prediction model for women undergoing screening mammography

BACKGROUND

Risk prediction models for breast cancer can be improved by the addition of recently identified risk factors, including breast density and use of hormone therapy. We used prospective risk information to predict a diagnosis of breast cancer in a cohort of 1 million women undergoing screening mammography.

METHODS

There were 2,392,998 eligible screening mammograms from women without previously diagnosed breast cancer who had had a prior mammogram in the preceding 5 years. Within 1 year of the screening mammogram, 11,638 women were diagnosed with breast cancer. Separate logistic regression risk models were constructed for premenopausal and postmenopausal examinations by use of a stringent (P<.0001) criterion for the inclusion of risk factors. Risk models were constructed with 75% of the data and validated with the remaining 25%. Concordance of the predicted with the observed outcomes was assessed by a concordance (c) statistic after logistic regression model fit. All statistical tests were two-sided.

RESULTS

Statistically significant risk factors for breast cancer diagnosis among premenopausal women included age, breast density, family history of breast cancer, and a prior breast procedure. For postmenopausal women, the statistically significant factors included age, breast density, race, ethnicity, family history of breast cancer, a prior breast procedure, body mass index, natural menopause, hormone therapy, and a prior false-positive mammogram. The model may identify high-risk women better than the Gail model, although predictive accuracy was only moderate. The c statistics were 0.631 (95% confidence interval [CI] = 0.618 to 0.644) for premenopausal women and 0.624 (95% CI = 0.619 to 0.630) for postmenopausal women.

CONCLUSION

Breast density is a strong additional risk factor for breast cancer, although it is unknown whether reduction in breast density would reduce risk. Our risk model may be able to identify women at high risk for breast cancer for preventive interventions or more intensive surveillance.

Toremifene--a promising therapy for the prevention of prostate cancer and complications of androgen deprivation therapy

Deregulation of the estrogen axis in humans prompts a series of tissue-specific events. In the breast and prostate, alterations in estrogen signalling lead to genotypic and phenotypic molecular alterations that result in dysplastic cellular appearance, deregulated cell growth and carcinoma. In bone, decreased estrogen leads to increased osteoclastogenesis and bone resorption, decreased bone mineral density and a significant fracture risk. Toremifene is a selective estrogen receptor modulator that exerts pharmacological activity in the breast, bone and prostate. An intense interest in developing this agent for prostate cancer chemoprevention is based on the reduction of premalignant and malignant prostate lesions in a transgenic model of prostate cancer. Biological and clinical activity was demonstrated in Phase II trials by the prevention of progression to prostate cancer in men with high-grade prostate intraepithelial neoplasia and through suppression of bone turnover biomarkers and increased bone mineral density in men on androgen deprivation therapy for prostate cancer.

Efficacy of new retinoids in the prevention of mammary cancers and correlations with short-term biomarkers

A number of retinoid X receptor (RXR) agonists have proven to be highly effective in preventing methylnitrosourea (MNU) induced mammary cancers. However, these agonists have side effects; particularly causing an increase in serum triglyceride levels. A series of ligands for RXR were designed based on computer modeling to the ligand binding domain (LBD) of the RXR receptors and on structure-activity relationships. The chemopreventive effects of these retinoids were evaluated in the relatively long-term MNU model. As a short-term assay to predict their efficacy, the ability of the retinoids to modulate cell proliferation and apoptosis was also determined in mammary cancers after only 7 days of treatment. The five UAB retinoids evaluated included two Class I UAB retinoids (UAB20, UAB112) and three Class II UAB retinoids (UAB30, 4-methyl-UAB30 and the benzosuberone-analog of UAB30). The previously evaluated RXR agonist targretin and the pan-agonist 9-cis-retinoic acid (9-cis-RA), which interacts with both RAR and RXR receptors, were included as positive agonists known to prevent cancer in the MNU model. In the prevention studies, in which the agents were administered beginning 5 days after MNU until the end of the study, targretin (150 mg/kg diet) and 4-methyl-UAB30 (200 mg/kg diet) were highly effective in decreasing cancer numbers by 75-85%. UAB30 (200 mg/kg diet) and 9-cis-RA (60 mg/kg diet) gave intermediate inhibitions of 60 and 45%, respectively. Targretin (15 mg/kg diet), UAB20 (200 mg/kg diet) and the benzosuberone analog of UAB30 (200 mg/kg diet) showed limited activity by decreasing cancer multiplicity 25-30%, while UAB112 had no effect on mammary cancer multiplicity. A direct correlation was observed between the long-term chemopreventive efficacy of these agents and their ability to decrease cell proliferation in mammary cancers after short-term treatment. Furthermore, the highly effective agents (4-methyl-UAB30 and targretin at 150 mg/kg diet) increased apoptosis 3-5 times, while agents with moderate or limited preventive efficacy failed to significantly increase apoptosis. Although the more effective retinoid treatments increased serum triglycerides 2.5- to 4.0-fold, one moderately effective agent (UAB30) had no significant effect on lipid levels. In summary, a short-term in vivo method has been identified for screening newly synthesized retinoids both for chemopreventive efficacy and for their adverse effect on serum triglycerides.

Tamoxifen for the prevention of breast cancer: current status of the National Surgical Adjuvant Breast and Bowel Project P-1 study

BACKGROUND

Initial findings from the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial (P-1) demonstrated that tamoxifen reduced the risk of estrogen receptor-positive tumors and osteoporotic fractures in women at increased risk for breast cancer. Side effects of varying clinical significance were observed. The trial was unblinded because of the positive results, and follow-up continued. This report updates our initial findings.

METHODS

Women (n = 13,388) were randomly assigned to receive placebo or tamoxifen for 5 years. Rates of breast cancer and other events were compared by the use of risk ratios (RRs) and 95% confidence intervals (CIs). Estimates of the net benefit from 5 years of tamoxifen therapy were compared by age, race, and categories of predicted breast cancer risk. Statistical tests were two-sided.

RESULTS

After 7 years of follow-up, the cumulative rate of invasive breast cancer was reduced from 42.5 per 1000 women in the placebo group to 24.8 per 1000 women in the tamoxifen group (RR = 0.57, 95% CI = 0.46 to 0.70) and the cumulative rate of noninvasive breast cancer was reduced from 15.8 per 1000 women in the placebo group to 10.2 per 1000 women in the tamoxifen group (RR = 0.63, 95% CI = 0.45 to 0.89). These reductions were similar to those seen in the initial report. Tamoxifen led to a 32% reduction in osteoporotic fractures (RR = 0.68, 95% CI = 0.51 to 0.92). Relative risks of stroke, deep-vein thrombosis, and cataracts (which increased with tamoxifen) and of ischemic heart disease and death (which were not changed with tamoxifen) were also similar to those initially reported. Risks of pulmonary embolism were approximately 11% lower than in the original report, and risks of endometrial cancer were about 29% higher, but these differences were not statistically significant. The net benefit achieved with tamoxifen varied according to age, race, and level of breast cancer risk.

CONCLUSIONS

Despite the potential bias caused by the unblinding of the P-1 trial, the magnitudes of all beneficial and undesirable treatment effects of tamoxifen were similar to those initially reported, with notable reductions in breast cancer and increased risks of thromboembolic events and endometrial cancer. Readily identifiable subsets of individuals comprising 2.5 million women could derive a net benefit from the drug.

Assessing the economic impact of chronic conditions in postmenopausal women

The ageing of the US population and the recognised importance of preventative care has led to a growing body of research regarding the morbidity and mortality associated with chronic diseases in postmenopausal women. According to the National Institute of Health, postmenopausal women have a significant increase in risk for a number of debilitating diseases, including osteoporosis, breast cancer and cardiovascular disease. In addition, recently published studies prompted patients, clinicians and payers to re-examine the risks and benefits of a well-accepted therapy to treat postmenopausal symptoms. The objective of this paper is to provide a framework for assessing the economic impact of disorders affecting postmenopausal women, with a particular focus on osteoporosis, breast cancer and cardiovascular disease. This framework considers the prevalence of these conditions, the profiles of women suffering from each of them and prevailing patterns of treatment for these disorders. Taken together, these factors are used to analyse the overall economic impact of postmenopausal disorders and to provide an expert opinion in this context.

Factors affecting breast cancer risk reduction practices among California physicians

BACKGROUND

Little is known about the incorporation of breast cancer risk reduction therapies into clinical practice.

METHODS

We assessed factors related to physicians' performance of breast cancer risk reduction practices through a self-administered survey. Subjects were California physicians in family medicine, internal medicine, or obstetrics/gynecology, identified through the AMA Masterfile. Physicians reported their breast cancer risk reduction practices (initiating patient counseling, referring patients for genetic evaluation, and prescribing tamoxifen or raloxifene) as well as barriers to counseling.

RESULTS

Of 1647 eligible physicians, 822 responded. Eighty-six percent reported initiating counseling, 45% referred a patient for genetic evaluation, 31% prescribed raloxifene, and 11% prescribed tamoxifen for breast cancer prevention in the past year. The leading frequent barriers to counseling were "not enough time" (40.3%) and "insufficiently informed about risk reduction options" (19.1%). Multivariate analysis showed that a training and role factors scale was negatively associated with all risk reduction practices, and number of breast cancer diagnoses per year was positively associated with referring for genetic evaluation and prescribing chemoprevention.

CONCLUSIONS

Physicians in primary care specialties report participation in several breast cancer risk reduction activities. Issues related to physician training and role in risk reduction affect the implementation of these practices.

Prevention of Hormone-Related Cancers: Breast Cancer

Carcinogenesis in the breast is a hormonally dependent process. Evidence implicating estrogen as a key breast carcinogen comes from various lines of investigation. Traditional epidemiologic studies demonstrate associations between estrogen exposure, both exogenous and endogenous, and increased breast cancer risk. Ongoing genetic epidemiologic studies also show associations between specific polymorphisms in estrogen-metabolizing genes and risk, albeit inconsistently. The application of these findings to the treatment and, more recently, the prevention of breast cancer has led to the development of agents that either (1) inhibit estrogen action at the estrogen receptor (selective estrogen receptor modulators (SERMs]); or (2) inhibit estrogen-synthesizing enzymes, thereby abrogating synthesis of this hormone (aromatase inhibitors). Large phase III trials have evaluated the ability of such agents to reduce the incidence of breast cancer in women at increased risk of the disease. The National Surgical Adjuvant Breast and Bowel Project (NSABP) P-1: Breast Cancer Prevention Trial (BCPT) demonstrated the superiority of the SERM tamoxifen to placebo in reducing breast cancer risk, leading to the Food and Drug Administration approval of tamoxifen for risk reduction. The implementation of tamoxifen for this indication has not become widespread in clinical practice, however, for a variety of reasons that we discuss. Results from the NSABP Study of Tamoxifen and Raloxifene, which compares the risk-reducing efficacy as well as toxicity of these two SERMs in a similar high-risk population, will be available in the near future. Based on promising data involving reduction of contralateral breast cancer risk in adjuvant studies, several aromatase inhibitors, including letrozole, anastrozole, and exemestane, are being incorporated into trials evaluating their efficacy as preventive agents in women at increased risk.

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.

Short-term impact of cancer prevention and screening activities on quality of life

PURPOSE

There are few data on the short-term effects of participating in cancer prevention activities, undergoing genetic risk assessment, or having routine screening. The objective of this article is to systematically review existing research on short-term effects of prevention, genetic counseling and testing, and screening activities on quality of life.

METHODS

We conducted a MEDLINE search for original research studies that were published between January 1, 1985, and December 31, 2002, and conducted in North America or Western Europe. Data were abstracted and summarized using a standardized format.

RESULTS

We reviewed 210 publications. Most studies focused on psychological states (anxiety, depression), symptoms, or general health status. One hundred thirty-one studies used 51 previously validated noncancer instruments. Many researchers (12.6%) also added cancer-specific measures, such as perceived cancer risk or symptom indices. Only one study measured satisfaction or quality of provider-client communication. While one report examined lost workdays, no other economic consequences of short-term outcomes were evaluated. Among seven studies that assessed short-term outcomes preferences, only four specifically used time trade-off or linear rating scale methods. No study used standard gamble or willingness-to-pay methods. The overwhelming majority of research indicated that short-term effects were transient. Only two studies linked short-term effects to long-term cancer-related health behaviors such as repeat screening.

CONCLUSION

There is considerable heterogeneity in short-term outcome measurement. Clinicians need to be aware of potential for short-term, transient adverse effects. The impact of short-term experiences should to be linked to long-term health status and use of services.

Therapeutic targeting in the estrogen receptor hormonal pathway

Estrogens work along with genetic changes to promote the development and growth of breast cancers. Because estrogenic hormones act via the estrogen receptors (ERs), ER-alpha and ER-beta, and the ER is present in more than half of breast tumors, this receptor has been the most widely targeted protein in breast cancer therapy. The presence of the ER in breast tumors predicts improved disease-free survival and response to selective ER modulators (SERMs), such as tamoxifen, or other forms of endocrine therapy. Suppression of ER activity by SERMs has proven to be a great benefit in the treatment of breast cancers and also in the prevention of breast cancer in women at high risk for the disease. The Study of Tamoxifen and Raloxifene trial comparing tamoxifen versus raloxifene effectiveness in breast cancer prevention is currently under way. To understand the balance of beneficial and undesirable effects of SERMs and to optimize their effectiveness, current investigations seek to characterize the genes activated or suppressed by these agents. Elucidation of the gene networks and cell signaling pathways under estrogen and SERM regulation and a clearer definition of the respective roles of ER-alpha and ER-beta and their coregulators in the actions of selective ER ligands, should enable the identification of new gene targets for therapeutic intervention and the development of novel drugs for the optimal treatment and prevention of breast cancer.

Uterine leiomyoma in the Eker rat: A unique model for important diseases of women

Eker rats carry a defect in the Tsc-2 tumor suppressor gene and female Eker rats develop uterine leiomyoma with a high frequency. The presentation, response to hormones and molecular alterations in these mesenchymal smooth muscle tumors, closely resembles their cognate human disease. Female rats and tumor-derived cell lines from Eker rat leiomyomas (ELT lines) have been developed as an in vivo/in vitro model system for preclinical studies to identify novel therapeutic agents for this disease and for studying disease pathogenesis. In addition to serving as a model for uterine leiomyoma, Eker rats have proven valuable for studying lymphangioleiomyomatosis, a related proliferative smooth muscle disease of women.

Arzoxifene as therapy for endometrial cancer

OBJECTIVE

Arzoxifene, an orally active third-generation selective estrogen-receptor modulator (SERM), opposes the action of estrogen on the breast and endometrium but exerts an estrogen-agonist effect on bone and the lipid profile. Since this is an appealing combination for hormonal therapy of estrogen-related cancers, we initiated testing the potential of arzoxifene in women with treatment-refractory endometrial cancer.

METHODS

Two phase I studies were conducted to evaluate the safety and pharmacokinetics of single and multiple doses of arzoxifene. In addition, two multi-institutional phase II trials have been completed on 100 women with metastatic or recurrent endometrial cancer.

RESULTS

No serious adverse events were observed in the single-dose phase I study, the principal side effect being hot flashes in 5/15 healthy volunteers. In the second phase I study, conducted in 32 women with metastatic breast cancer, one patient had a serious, possibly drug-related adverse reaction (pulmonary embolism). The two multi-institutional trials demonstrated significant activity at 20 mg/day in patients with metastatic or recurrent endometrial cancer. Observed clinical response rates were 25 and 31%, with a median response duration of 19.3 and 13.9 months, respectively. Progression of the disease was stabilized in a substantial number of women. Toxicity was mild, except for two cases of pulmonary embolism that might have been drug related.

CONCLUSIONS

Further investigation is warranted to verify these preliminary response rates and the clinical significance of the stable disease cases, to compare clinical outcomes with those in progestin-treated women, and to elucidate the mechanisms of SERM action in this disease.

Breast cancer chemoprevention: current challenges and a look toward the future

There is a need to develop new prevention agents for breast cancer risk reduction that would have fewer side effects than the approved agent, tamoxifen, and/or would be effective in preventing estrogen receptor-negative or tamoxifen-resistant, estrogen receptor-positive breast cancers. There also is a need to improve the accuracy of present risk assessment models and to incorporate tissue-based biomarkers to supplement risk prediction tools. Candidate risk biomarkers include the serum hormones insulin-like growth factor-1 and its binding protein-3, mammographic breast density, nipple aspirate fluid production, and breast tissue evidence of proliferative breast disease (intraepithelial neoplasia). A variety of techniques have been developed to randomly sample breast tissue to detect precancerous changes and/or detect modulation of proliferation in response to a prevention agent. Based on molecular abnormalities observed in breast intraepithelial neoplasia, a number of drug classes and combinations are suggested as potential chemoprevention approaches. Clinical trial models have been developed to select the appropriate drug dose for subsequent biomarker modulation chemoprevention trials in which the use of surrogate endpoint biomarkers as indicators of efficacy is being explored. If these biomarkers can be validated and shown to reliably predict and monitor response in phase I/II prevention trials, and if favorable modulation is correlated with subsequent decreased cancer incidence, biomarkers may replace cancer incidence as the endpoint in future phase III trials, dramatically reducing the time and expense associated with new prevention drug development.

Risk estimation for breast cancer development; a clinical perspective

Breast cancer is the commonest cancer among women and the second highest cause of cancer death. It remains a significant health problem and represents a significant worry for many women and their physician. During the last years, intensive research has been focused on accurate risk estimation for breast cancer development. The aim of these efforts is to identify the "high-risk" group of women for breast cancer development. Preventive strategies (including intensive surveillance, chemoprevention, or prophylactic mastectomy) may be applied for the women at high risk for breast cancer development. Given the many management options, it seems reasonable that management of the high-risk woman be tailored to the level of risk she is willing to accept. In estimating the risk for breast cancer development, several factors should be taken into account (including age, reproductive factors, such as age at menarche and age at menopause or pregnancy and age at first live birth, history of benign breast lesions or breast cancer in situ [LCIS/DCIS], prior history of breast cancer, history of familiar or hereditary breast cancer, and environmental and lifestyle factors). Recently, quantitative risk estimation is possible by combining multiple risk factors into a comprehensible risk expression; this is of significant clinical importance, since it will reduce the considerable variation in management among health care providers. The Gail and the Claus model are the most widely used models for quantitative risk estimation. However, the clinician should understand that all models have some limitations that should be recalled as they are applied. It should be emphasized that risk assessment is a serious undertaking and should only be performed by those who have in-depth knowledge about risk factors, family pedigree analysis, comparative statistics, genetics susceptibility testing and the science of probability.

Growth-stimulatory and transcriptional activation properties of raloxifene in human endometrial Ishikawa cells

Raloxifene (Ral) has estrogenic activity in bone and cardiovascular tissues, but is antiestrogenic in breast and has limited uterotrophic activity in mice. Here we report that Ral stimulates the growth of human endometrial Ishikawa tumors implanted in the mammary fat pad of nude ovariectomized mice. In cultured Ishikawa cells, Ral has agonist effects on transcription mediated by the progesterone receptor, an endogenous estrogen target gene, and on expression of reporter genes containing estrogen response elements (EREs). Both Ral and tamoxifen (Tam), but not estradiol, stimulated transcription mediated by the activator protein 1 at micromolar concentrations. However, this effect correlated with induction of cellular death at high concentrations of Ral or Tam and was not observed at lower concentrations. Our results suggest that Ral has stimulatory effects in Ishikawa cells on both cellular growth and gene transcription, and that EREs can mediate some of these effects.