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PubMed2000

Phytoestrogens as hormone replacement therapy: an evidence-based approach.

Postmenopausal women have sought nonestrogen alternatives to hormone replacement in order to avoid possible risks and side effects of the therapy. Selective estrogen receptor modulators have been developed to tailor therapy to a specific risk/benefit profile that will best fit the patient. More women have looked to phytoestrogens, such as the isoflavones found in the soy plant, to tailor their menopausal therapy in a "natural" way. This review examines the evidence regarding the risks and benefits of isoflavones as hormone replacement therapy. Controlled trials have shown a reduction in postmenopausal hot flashes when subjects' diets were supplemented with soy. There is less evidence for a benefit in vaginal dryness symptoms. Furthermore, dietary supplementation also appears to lower total and low-density lipoprotein cholesterol in hypercholesterolemic subjects. A synthetic isoflavone, ipriflavone, has been shown in controlled trials to prevent postmenopausal bone loss, though there is much less evidence that soy isoflavones will accomplish this goal. Finally, although unopposed estrogen replacement may promote breast and endometrial cancer, there is no evidence that phytoestrogens will do the same. In contrast, great interest has been taken in the potential cancer-protective effects of phytoestrogens, though prospective evidence in postmenopausal women is not available. Although data regarding the use of isoflavone extracts are incomplete, dietary supplementation with soy foods appears to be a safe and possibly beneficial option for postmenopausal women.

Journal Article↗

PubMed1998

Clinically favorable effects of raloxifene on bone mineral density and serum lipids: population assessment via bivariate analysis.

Introduction: Raloxifene is a nonsteroidal benzothiophene derivative that is classified as a selective estrogen receptor modulator (SERM). It has clinical promise because of its actions as an estrogen-agonist on bone and serum lipids and an estrogen-antagonist on the breast and uterus.Objectives: To determine the percentage of women who respond to raloxifene therapy with regard to bone mineral density (BMD) and serum low density lipoprotein cholesterol (LDL-C) concentration in a large population of healthy postmenopausal women.Methods: Pooled 24-month interim data from two multicenter, placebo-controlled, double-blind phase III studies were used in this analysis. The study population included 1145 healthy women, 45-60 years of age and 2-8 years postmenopausal, randomized to receive either placebo, raloxifene (RLX) 30 mg/day, RLX 60 mg/day, or RLX 150 mg/day. Changes in BMD, measured by dual x-ray absorptiometry, and serum LDL-C concentration, measured by enzymatic assay, were analyzed simultaneously by plotting the median percentage change (baseline to endpoint) in BMD of the lumbar spine and total hip on the y-axis against the corresponding median percentage change in serum LDL-C on the x-axis for each subject in the placebo group and each of the raloxifene groups. The data localized to one of four quadrants on the plot, the upper-left quadrant representing clinically favorable shifts (increased BMD and decreased LDL-C) and the lower-right quadrant representing clinically unfavorable shifts (decreased BMD and increased LDL-C). The bivariate mean, 50th and 95th percentile ellipses, and the percentage of patients improving in one, both, or neither of the measured parameters are displayed.Results: At the end of 24 months, the bivariate mean and the 50th and 95th percentile ellipses of the placebo group for lumbar spine BMD and LDL-C were shifted to the clinically unfavorable quadrant of the plot, reflecting a decrease in BMD and an increase in LDL-C. In contrast, the bivariate mean for all raloxifene groups had shifted to the clinically favorable quadrant of the plot, reflecting an increase in BMD and a decrease in LDL-C. There was a statistically significant difference (Hotelling-Lawley test, P <.001) in the bivariate mean for all doses of raloxifene compared to placebo. Only 19.1% of subjects in the placebo group exhibited improvement in both lumbar spine BMD and LDL-C, whereas 43.5%, 47.4%, and 49.8% of subjects in the RLX 30, RLX 60, and RLX 150 group, respectively, exhibited improvement in both of these variables. Furthermore, 35.9% of subjects in the placebo group exhibited no improvement in either lumbar spine BMD or LDL-C, whereas only 13.7%, 10.1%, and 11.6% of subjects in the RLX 30, RLX 60, and RLX 150 groups, respectively, exhibited no improvement in either of these variables. Similar results were obtained comparing total hip BMD and LDL-C.Conclusions: Compared with placebo, raloxifene has beneficial effects on BMD and LDL-C in a large sample of healthy postmenopausal women. Thus, insofar as these intermediate endpoints predict disease outcomes, long-term therapy with raloxifene may be beneficial in the prevention of osteoporosis and cardiovascular diseases.

Journal Article↗

PubMed1998

Raloxifene effects on vasomotor and other climacteric symptoms in postmenopausal women.

Introduction and Objectives: Raloxifene, a novel selective estrogen receptor modulator (SERM), is under investigation for the prevention of osteoporosis in postmenopausal women. Like traditional estrogen replacement therapy, raloxifene has beneficial effects on bone and on serum lipids whereas, in contrast to estrogen's adverse effects in the breast and uterus, raloxifene is an estrogen antagonist in the breast and is nonstimulatory in the uterus. This study examines the effects of raloxifene 60 mg/day compared with placebo on: 1) the incidence of vasomotor symptoms: hot flashes (flushing) and sweating (including night sweats), 2) the severity and time course of hot flashes, and 3) the relation of hot flashes to baseline subject characteristics and study discontinuations. Additionally, the study explores the effects of raloxifene 60 mg/day compared with placebo on other climacteric symptoms that affect the quality of life of postmenopausal women, such as depression, insomnia, mood lability and genitourinary complaints.Methods: Integrated data from five randomized, placebo-controlled studies involving 1,165 healthy, postmenopausal women, with up to 30 months of study drug exposure, were analyzed. The incidence and severity of hot flashes and other climacteric symptoms were compared in patients treated with placebo or raloxifene (60 mg/day) via open-ended, non-directed subject self-assessment questionnaires. Data were analyzed for subgroup-by-therapy interactions using many baseline subject characteristics such as age, body mass index, smoking, alcohol, and years post-menopause, as well as preexisting conditions such as hot flashes, sweating, insomnia, depression, and history of hysterectomy. The overall incidence of other climacteric symptoms were reported as adverse events.Results: The increase in overall incidence of hot flashes in raloxifene-treated (24.6%) and placebo-treated (18.3%) subjects was modest, but statistically significant. However, this difference was significant only during the first 6 months of therapy, raloxifene (20.1%) compared with placebo (14.4%). After 6 months of treatment, there was no statistically significant difference in the incidence of hot flashes between the two treatment groups. The majority of hot flashes in raloxifene-treated subjects were subject-assessed as "mild-to-moderate" in severity (89%). The incidence of hot flashes reported as "severe" did not differ significantly in raloxifene- or placebo-treated subjects. Subgroup analyses revealed the overall incidence of hot flashes to be highest for both raloxifene and placebo-treated subjects, in younger (age < 55 years) women (P =.004), in women who had previously experienced hot flashes (P =.031), and in women having had hysterectomies (P <.001). Within each of these subgroups, there was no statistical difference in the incidence of hot flashes between the raloxifene and placebo groups. Between the two treatment groups, there was no difference in the overall incidence of subject discontinuations from study due to hot flashes. The occurrence of the other common vasomotor symptom, sweating (which includes night sweats), was not statistically different for the raloxifene- or placebo-treated subjects.Genitourinary complaints are often symptoms related to vaginal dryness, such as dyspareunia and decreased libido, as well as other symptoms of vaginitis and leukorrhea. No statistically significant differences occurred for raloxifene- or placebo-treated subjects in reports of these genitourinary symptoms. Similarly, for the other common climacteric symptoms; depression, insomnia, and mood lability, no significant differences in incidence between the raloxifene and placebo treatment groups were observed.Conclusions: Raloxifene (60 mg/day) treatment modestly increased the incidence of hot flashes compared with placebo, however, this difference was only statistically significant during the first 6 months of treatment. There were no differences in the severity of hot flashes between treatment groups, and this symptom did not adversely affect subjects' study participation. In both the raloxifene and placebo treatment groups, young postmenopausal women (age < 55), those with baseline hot flashes, and those with histories of hysterectomy were most likely to experience hot flashes. Raloxifene therapy did not affect the occurrence of other climacteric symptoms commonly affecting the quality of life of women after menopause.

Journal Article↗

PubMed1998

Raloxifene HCl is not stimulatory in the endometrium as assessed by the blaustein criteria and an estrogenicity scoring system.

Introduction: Raloxifene, a selective estrogen receptor modulator (SERM), acts as an estrogen agonist in the bone and on serum lipids and an estrogen antagonist in breast tissue. The effect of raloxifene on the endometrium of postmenopausal women is a key factor in determining its clinical application.Objectives: The objectives are to determine and compare the histologic outcomes of endometrial samples from healthy postmenopausal women receiving either a high dose of raloxifene or hormone replacement therapy (HRT).Design: The current study is a 24-month, multicenter, double-blind, randomized study of 136 healthy postmenopausal women randomized to receive either raloxifene 150 mg/day (RLX) or continuous combined HRT (Premarin(R) 0.625 mg/day and Provera(R) 2.5 mg/day).Materials and Methods: Endometrial samples obtained by Pipelle biopsy at baseline and endpoint were evaluated using Blaustein's criteria (Kurman RJ, editor Blaustein's pathology of the female genital tract. 1994), which is composed of descriptive diagnostic categories and a newly developed estrogenicity scoring system to quantify subtle morphologic changes in the postmenopausal endometrium (Boss et al. Am J Obstet Gynecol, in press). All subjects with adequate baseline and post-baseline endometrial samples were included in the analyses. The results from the 12-month interim analyses are reported and the Blaustein's criteria and the estrogenicity scoring system are compared.Results: Overall, 95.2% of the baseline biopsies were normal. At endpoint 30.6% of the subjects in the HRT group with normal baseline biopsies developed proliferative endometrium and 2.8% developed a polyp, while none in the RLX group developed either. Histological evaluation of stromal and glandular features revealed substantially lower estrogenicity scores in the RLX group. As shown in the table, a high degree of agreement was observed between the estrogen effect grades and the Blaustein's descriptive diagnostic categories at endpoint as shown by a Spearman correlation coefficient of 0.75 and a Kappa coefficient of 0.91.Conclusion: Results from the 12-month interim analyses reveal that, in contrast to HRT, raloxifene does not have stimulatory effects on the endometrium. Also, there is high degree of agreement between Blaustein's criteria and the estrogenicity scoring system used to evaluate endometrial histology.

Journal Article↗

PubMed2001

Potent estrogen agonists based on carborane as a hydrophobic skeletal structure. A new medicinal application of boron clusters.

BACKGROUND: Carboranes (dicarba-closo-dodecaboranes) are a class of carbon-containing polyhedral boron-cluster compounds having remarkable thermal stability and exceptional hydrophobicity. Applications of the unique structural and chemical properties offered by icosahedral carboranes in boron neutron capture therapy have received increasing attention over the past 30 years. However, these features of carboranes may allow another application as a hydrophobic pharmacophore in biologically active molecules that interact hydrophobically with receptors. RESULTS: We have designed candidate estrogen-receptor-binding compounds having carborane as a hydrophobic skeletal structure and synthesized them. The most potent compound bearing a carborane cage exhibited activity at least 10-fold greater than that of 17beta-estradiol in the luciferase reporter gene assay. Estrogen receptor-alpha-binding data for the compound were consistent with the results of the luciferase reporter gene assay. The compound also showed potent in vivo effects on the recovery of uterine weight and bone loss in ovariectomized mice. CONCLUSION: Further development of the potent carborane-containing estrogenic agonists described here, having a new skeletal structure and unique characteristics, should yield novel therapeutic agents, especially selective estrogen receptor modulators. Furthermore, the suitability of the spherical carborane cage for binding to the cavity of the estrogen receptor-alpha ligand-binding domain should provide a basis for a similar approach to developing novel ligands for other steroid receptors.

Animals↗

PubMedDate not supplied

Hormone replacement therapy and breast cancer: revisiting the issues.

OBJECTIVE: To assess current ideas about the benefits and risks of estrogen and hormone replacement therapy (ERT/HRT) in postmenopausal women. DATA SOURCES: MEDLINE searches, supplemented by various texts, of the literature on HRT, ERT, and selective estrogen receptor modulators (SERMs): tamoxifen, toremifene, and raloxifene. DATA SYNTHESIS: HRT is primarily used for improving quality of life in women suffering from vasomotor symptoms associated with menopause. HRT is beneficial in postmenopausal women for preventing cardiovascular disease, osteoporosis, and Alzheimer's disease. Review of meta-analyses of clinical trials showed that ERT/HRT ever-users (patients who have ever used ERT/HRT) did not have an increased risk of breast cancer, but current users did have an increased risk, with some studies reporting increasing risk with duration of ERT. No relationship was found between dose or the addition of progestin to ERT and increased breast cancer risk. Overall breast cancer mortality rates associated with HRT were decreased in current users. In general, HRT does not increase the risk of breast cancer in women with a family history of the disease, compared with those without a family history. New HRT strategies that could potentially prevent breast cancer are now being developed. The SERMs tamoxifen and toremifene appear to have positive clinical effects on bone and serum lipids; they are currently being investigated for use as breast cancer chemopreventive agents. Raloxifene, a new SERM used for the prevention of osteoporosis, is an alternative for women who cannot tolerate HRT. Unfortunately, these SERMS have anti-estrogenic effects and thus cause vasomotor adverse effects such as hot flashes and vaginal dryness. In addition, SERMs do not protect against heart disease or prevent osteoporosis as well as does HRT. CONCLUSION: Presently, SERMs will not become first-line HRT, as the positive effects of ERT/HRT may outweigh any potentially increased risk of breast cancer. The development of new agents with pharmacodynamic profiles similar to that of ERT/HRT but lacking its adverse effects would be greatly beneficial for postmenopausal women.

Alzheimer Disease↗

PubMed1999

Droloxifene does not blunt bone anabolic effects of prostaglandin E2, but maintains prostaglandin E2-restored bone in aged, ovariectomized rats.

Droloxifene (DRO) is a selective estrogen receptor modulator that prevents bone loss by inhibition of bone turnover associated with estrogen deficiency in both growing and aged female rats. The purposes of this study were to test: (a) whether DRO can maintain prostaglandin E2 (PGE2)-restored bone after discontinuation of PGE2 in aged, ovariectomized (ovx) rats; (b) if an inhibition of bone turnover by DRO reduces bone anabolic effects of PGE2; and (c) whether bone mass restored by PGE2 plus DRO can be maintained after discontinuation of both agents. Female rats at 12 months of age were sham-operated (sham) or ovx. Three months postsurgery, ovx rats were treated with either PGE2 (3 mg/kg per day, subcutaneously [s.c.]) alone, or PGE2 plus DRO (10 mg/kg per day, per os [p.o.]) for 2 months. Thereafter, the PGE2 or PGE2 plus DRO treatment was withdrawn and the rats were then treated with either vehicle or DRO for another 1.5 months. Using dual-energy X-ray absorptiometry (DXA), total lumbar vertebral bone mineral density (LV-BMD) was determined in vivo at months 0, 3, 5, and 6.5. At the end of the study, the rats were autopsied, and BMD of total femur, femoral shaft, distal femoral metaphysis, and proximal femur was determined ex vivo by DXA. Standard static and dynamic bone histomorphometric parameters were determined on the fourth lumbar vertebral body (L-4). At 3, 5, or 6.5 months postsurgery, LV-BMD decreased significantly (-15%, -19%, and -19%, respectively) in the vehicle-treated ovx rats compared with sham. Beginning at 3 months post-ovx, PGE2 alone or in combination with DRO for 2 months completely restored LV-BMD back to the sham level. There was no difference in LV-BMD in PGE2 alone or PGE2 plus DRO. Upon cessation of PGE2 treatment, a significant decrease in LV-BMD was observed in the PGE2-alone group (-12%). On the other hand, when DRO treatment was given after discontinuation of PGE2, the PGE2-restored LV-BMD was completely maintained. In the PGE2 plus DRO group, no loss in LV-BMD was observed after cessation of either PGE2 alone or both PGE2 and DRO. However, treatment with DRO following 2 months of PGE2 plus DRO further increased LV-BMD (+10%). At the end of the study, ex vivo femoral BMD data confirmed the observation in lumbar vertebrae. Histomorphometric results of L-4 indicated that loss in bone mass after cessation of PGE2 in PGE2 alone group was associated with increased bone turnover. Treatment with DRO in the maintenance phase inhibited bone turnover and prevented bone loss induced by withdrawal of PGE2. Trabecular bone mass was maintained in the PGE2 plus DRO followed by vehicle group and further increased in the PGE2 plus DRO followed by DRO groups. We found that: (a) DRO is efficacious in maintaining PGE2-restored bone after discontinuation of PGE2; (b) DRO did not blunt the anabolic effects of PGE2; (c) bone loss occurred after cessation of treatment in the PGE2-alone group, whereas it was maintained after cessation of treatment in PGE2 plus DRO group; and (d) an additional anabolic effect was found in ovx rats treated with PGE2 plus DRO followed by DRO.

Absorptiometry, Photon↗

PubMed2005

Treatment of menopause-related mood disturbances.

More than 1.7 million American women are expected to reach menopause each year. Recent Canadian statistics show that a 50-year-old woman can now expect to live until her mid-80s, which implies living at least one-third of her life after menopause. The menopausal transition is typically marked by intense hormonal fluctuations, accompanied by vasomotor symptoms (eg, hot flashes, night sweats), sleeps disturbance, and changes in sexual function, as well as increased risk for osteoporosis, cardiovascular disease, and cognitive decline. More importantly, recent studies have demonstrated a significant association between menopausal transition and a higher risk for developing depression. In the post-Women's Health Initiative Study era, physicians and patients are questioning the safety and efficacy of long-term hormone therapy use. This article reviews the current literature on the benefits and risks of using hormone therapy for the treatment of menopause-related mood disturbances and alternate strategies currently available for the management of menopause-related problems, including antidepressants, complementary and alternative medicine, and selective estrogen receptor modulators.

Estrogen Replacement Therapy↗

PubMed2001

Selected reaction monitoring LC-MS determination of idoxifene and its pyrrolidinone metabolite in human plasma using robotic high-throughput, sequential sample injection.

The generation of large numbers of samples during early drug discovery has increased the demand for rapid and selective methods of analysis. Liquid chromatography-tandem mass spectrometry (LC-MS-MS), because of its sensitivity, selectivity, and robustness, has emerged as a powerful tool in the pharmaceutical industry for many analytical needs. This work presents a high-throughput selected reaction monitoring LC-MS bioanalytical method for the determination of idoxifene, a selective estrogen receptor modulator, and its pyrrolidinone metabolite in clinical human plasma samples. The described method uses short, small-bore columns, high flow rates, and elevated HPLC column temperatures to perform LC separations of idoxifene and its metabolite within 10 s/sample. Sequential injections were accomplished with a 215/889 multiple probe liquid handler (Gilson, Inc.), which aspirates eight samples simultaneously and performs its rinse cycle parallel to sample injection, resulting in minimum lag time between injections. This high-throughput method was applied to the determination of idoxifene and its metabolite in clinical human plasma samples. Sample preparation employed liquid/liquid extraction in the 96-well format. Method validation included determination of intra- and interassay accuracy and precision values, recovery studies, autosampler stability, and freeze-thaw stability. The LOQ obtained was 10 ng/mL for idoxifene and 30 ng/mL for the metabolite. Using idoxifene-d5 as an internal standard, idoxifene showed acceptable accuracy and precision values at QC level 1 (QC1, 15 ng/mL), level 2 (QC2, 100 ng/mL), and level 3 (QC3, 180 ng/mL) (85.0% accuracy +/- 12.0% precision, 95.1 +/- 4.9%, and 90.3 +/- 4.7%, respectively). The pyrrolidinone metabolite also showed acceptable accuracy and precision values (using no internal standard for quantitation) at QC1 (60 ng/mL), QC2 (100 ng/mL), and QC3 (180 ng/mL) (104.9 +/- 14.4%, 91.1 +/- 13.0%, and 90.8 +/- 12.2%, respectively). The validated method was applied to the analysis of 613 human clinical plasma samples. An average run time of 23 s/sample (approximately 37 min/ 96-well plate or over 3,700 sample/day) was achieved. The successful validation presented indicates that rapid methods of analysis can efficiently and reliably contribute to the fast sample turnaround required for high sample number generating processes.

Chromatography, Liquid↗

PubMed2005

Evaluation of estrogenic/antiestrogenic activity of ellagic acid via the estrogen receptor subtypes ERalpha and ERbeta.

Ellagic acid is a plant-derived polyphenol, possessing antioxidant, antiproliferative, and antiatherogenic properties. Whether this compound has estrogenic/antiestrogenic activity, however, remains largely unknown. To answer this question, we first investigated the ability of ellagic acid to influence the activity of the estrogen receptor subtypes ERalpha and ERbeta in HeLa cells. Cells co-transfected with an estrogen response element (ERE)-driven luciferase (Luc) reporter gene and an ERalpha- or ERbeta-expression vector were exposed to graded concentrations of ellagic acid. At low concentrations (10(-7) to 10(-9) M), this compound displayed a small but significant estrogenic activity via ERalpha, whereas it was a complete estrogen antagonist via ERbeta. Further evaluation revealed that ellagic acid was a potent antiestrogen in MCF-7 breast cancer-derived cells, increasing, like the pure estrogen antagonist ICI182780, IGFBP-3 levels. Moreover, ellagic acid induced nodule mineralization in an osteoblastic cell line (KS483), an effect that was abolished by the estrogen antagonist. Endometrium-derived epithelial cells (Ishikawa) showed no response to the natural compound by using a cell viability assay (MTT). These findings suggest that ellagic acid may be a natural selective estrogen receptor modulator (SERM).

Breast Neoplasms↗

PubMed2003

De novo design, synthesis, and evaluation of novel nonsteroidal phenanthrene ligands for the estrogen receptor.

Although there are many estrogen receptor antagonists with improved tissue selectivity profiles compared with tamoxifen, optimal tissue selectivity has not yet been demonstrated. As such there is still a need for additional diversity and new chemical scaffolds to allow for exploration of improved tissue selectivity. Here, we describe the discovery of a novel phenanthrene scaffold for estrogen receptor ligands utilizing a ligand based de novo design approach. The nanomolar binding of phenanthrenes, 12b,c, 14b,c, and 15 against human recombinant ER(alpha) indicates that our ligand based de novo design approach was successful. From a gene transfection assay, 12b,c, 14b,c, and 15 displayed only antagonistic activity with no observable agonistic activity. The alkyl 9,10-dihydrophenanthrene 16 (presumably a racemic mixture) was a substantially more potent ER binder than the phenanthrenes. It also displayed only antagonistic activity and was effective at inhibiting estradiol stimulated MCF-7 cell proliferation. These results demonstrate that this phenanthrene (and 9,10-dihydrophenanthrene) scaffold warrants further study as potential selective estrogen receptor modulators and/or pure antiestrogens.

Animals↗

PubMed2005

Nonpolar and short side chain groups at C-11beta of estradiol result in antiestrogens.

We have previously found that esters of 11beta-estradiol carboxylates are transformed from an estrogen into an antiestrogen when the 11beta-side chain is increased in length from four to five non-hydrogen atoms (n > or = 5). To understand the structural requirements for this transformation and obtain metabolically stable analogues that are not susceptible to esterase cleavage, we have synthesized other compounds having an 11beta-side chain composed of other functional groups: ketones, amides, ethers, and thiono esters. With the exception of amides, which bind poorly to the estrogen receptor (ER), all of these compounds exhibit antiestrogenic action when the side chain length is n > or = 5. Ethers (n > or = 5), studied in more detail, inhibit the action of estradiol with either ERalpha or ERbeta. In rat uteri they are estrogen antagonists/weak agonists and decrease the concentration of cholesterol in blood (an hepatic estrogenic action). Thus, these short chain and nonpolar 11beta-analogues of estradiol have tissue specific antiestrogenic/estrogenic actions, characteristics of selective estrogen receptor modulators.

Amides↗

PubMed2006

Quantitative profiling of drug-associated proteomic alterations by combined 2-nitrobenzenesulfenyl chloride (NBS) isotope labeling and 2DE/MS identification.

The identification of drug-responsive biomarkers in complex protein mixtures is an important goal of quantitative proteomics. Here, we describe a novel approach for identifying such drug-induced protein alterations, which combines 2-nitrobenzenesulfenyl chloride (NBS) tryptophan labeling with two-dimensional gel electrophoresis (2DE)/mass spectrometry (MS). Lysates from drug-treated and control samples are labeled with light or heavy NBS moiety and separated on a common 2DE gel, and protein alterations are identified by MS through the differential intensity of paired NBS peptide peaks. Using NBS/2DE/MS, we profiled the proteomic alterations induced by tamoxifen (TAM) in the estrogen receptor (ER) positive MCF-7 breast cancer cell line. Of 88 protein spots that significantly changed upon TAM treatment, 44 spots representing 23 distinct protein species were successfully identified with NBS-paired peptides. Of these 23 TAM-altered proteins, 16 (70%) have not been previously associated with TAM or ER activity. We found the NBS labeling procedure to be both technically and biologically reproducible, and the NBS/2DE/MS alterations exhibited good concordance with conventional 2DE differential protein quantitation, with discrepancies largely due to the comigration of distinct proteins in the regular 2DE gels. To validate the NBS/2DE/MS results, we used immunoblotting to confirm GRP78, CK19, and PA2G4 as bona fide TAM-regulated proteins. Furthermore, we demonstrate that PA2G4 expression can serve as a novel prognostic factor for disease-free survival in two independent breast cancer patient cohorts. To our knowledge, this is the first report describing the proteomic changes in breast cancer cells induced by TAM, the most commonly used selective estrogen receptor modulator (SERM). Our results indicate that NBS/2DE/MS may represent a more reliable approach for cellular protein quantitation than conventional 2DE approaches.

Cell Line, Tumor↗

PubMed2005

Analysis of protein covalent modification by xenobiotics using a covert oxidatively activated tag: raloxifene proof-of-principle study.

Numerous xenobiotics, including therapeutics agents, are substrates for bioactivation to electrophilic reactive intermediates that may covalently modify biomolecules. Selective estrogen receptor modulators (SERMs) are in clinical use for long-term therapy of postmenopausal syndromes and chemoprevention and provide a potential alternative for hormone replacement therapy (HRT). Raloxifene, in common with many SERMs and other xenobiotics, is a polyaromatic phenol that has been shown to be metabolically bioactivated to electrophilic and redox active quinoids. Nucleic acid and glutathione adduct formation have been reported, but little is known about protein covalent modification. A novel COATag (covert oxidatively activated tag) was synthesized in which raloxifene was linked to biotin. The COATag was reactive toward a model protein, human glutathione-S-transferase P1-1, in the presence but not the absence of monooxygenase. The covalent modification of proteins in rat liver microsomal incubations was NADPH-dependent implicating cytochrome P450 oxidase. The COATag facilitated isolation and identification of covalently modified microsomal proteins: cytosolic glucose regulated protein (GRP78/BiP), three protein disulfide isomerases, and microsomal glutathione S-transferase 1. Oxidative metabolism of raloxifene produces reactive intermediates of sufficient lifetimes to covalently modify proteins in tissue microsomes, behavior anticipated for other polyaromatic phenol xenobiotics that can be tested by the COATag methodology. The combined use of a COATag with a simple biotin-linked electrophile (such as an iodoacetamide tag) is a new technique that allows quantification of protein covalent modification via alkylation vs oxidation in response to xenobiotic reactive intermediates. The identification of modified proteins is important for defining pathways that might lead alternatively to either cytotoxicity or cytoprotection.

Animals↗

PubMed2006

Antiestrogens and the formation of DNA damage in rats: a comparison.

Tamoxifen (TAM) has been used as an agent for the treatment and prevention of breast cancer. However, long-term treatment of TAM in women increases the risk of developing endometrial cancer. The secondary cancer may be due to the genotoxicity of TAM. To find safer alternatives, four selective estrogen receptor modulators (SERMs), 4-hydroxytamoxifen (4-OHTAM), toremifene (TOR), raloxifene (RAL), and ICI 182,780, were administered to rats with an equimolar dose of TAM [54 micromol/kg (20 mg/kg)/day, p.o. for 7 days]. To evaluate the genotoxicity of each SERM, the presence of bulky DNA adducts was determined by (32)P-postlabeling/polyacrylamide gel electrophoresis and (32)P-postlabeling/high-performance liquid chromatography. The formation of 7,8-dihydro-8-oxodeoxyguanosine (8-oxodG) was analyzed as a marker of typical oxidative damage, using liquid chromatography electrospray tandem mass spectrometry. Among the SERMs, bulky DNA adducts were detected in the livers of rats treated with TAM; the total amount of TAM-DNA adducts was 26.1 adducts/10(7) nucleotides. However, with a detection limit of approximately 2 adducts/10(9) nucleotides, no bulky DNA adducts were observed with 4-OHTAM, TOR, RAL, or ICI 182,780. In addition, no significant increase of hepatic 8-oxodG lesions was detected in rats treated with any of the antiestrogens. Therefore, TOR, RAL, and ICI 182,780 are likely to be less genotoxic than TAM.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2000

Chemoprevention of breast cancer.

Despite a recent trend toward improvement in the U.S. breast cancer mortality rate, breast cancer incidence (182,800 new cases anticipated in 2000) and mortality figures (over 40,800 anticipated deaths) remain the highest and second highest, respectively, of all cancers in U.S. women. In 1998, the selective-estrogen-receptor-modulator (SERM) tamoxifen achieved positive results in the Breast Cancer Prevention Trial (BCPT), leading to the Food and Drug Administration (FDA) approval of tamoxifen for risk reduction in women at high risk of breast cancer (the historic first FDA approval of a cancer preventive agent). This brought about a paradigm shift in new approaches for controlling breast cancer toward pharmacologic preventive regimens, called chemoprevention. This paper presents a comprehensive clinical review of breast cancer prevention study, highlighting issues of the extensive study of tamoxifen. These issues include the record of primary tamoxifen results in several breast-cancer risk-reduction settings (primary, adjuvant, and ductal carcinoma in situ [DCIS]); critical secondary BCPT risk-benefit findings (including quality of life issues) and their effects on counseling patients on use of tamoxifen for prevention; ethic minorities; optimal tamoxifen dose/duration; and potential impact on mortality and other issues involved with potential net benefit to society. Other breast-cancer chemoprevention issues reviewed here include women at high genetic risk (especially BRCA1 mutation carriers); raloxifene in breast cancer prevention; other SERMs; SERM resistance; and new agents and combinations currently in development. Very recent developments involving PPAR-gamma ligands, COX-2 inhibitors, and RXR-ligands are discussed in the section on new drug development.

Adult↗

PubMed2001

Divergent effects of raloxifene HCI on the pharmacokinetics and pharmacodynamics of warfarin.

PURPOSE: Evista (raloxifene HCl) is a nonsteroidal selective estrogen receptor modulator that displays estrogen agonist effects on bone and lipid metabolism but estrogen antagonist effects on the breast and endometrium. The potential for drug-drug interaction between raloxifene and warfarin was assessed in 15 healthy postmenopausal women. METHODS: Single doses of warfarin (20 mg) were administered prior to and during 2 weeks of dosing with raloxifene 120 mg/day. Each warfarin dose was followed by pharmacokinetic sampling and prothrombin time measurements. RESULTS: Raloxifene administration resulted in 7.1% and 14.1% decreases in the clearance (CLp/F) and 7.4% and 9.8% decreases in the volume of distribution (Vss/F) of R- and S-warfarin, respectively (all p < or = 0.05). In contrast to the slightly higher plasma concentrations of R- and S-warfarin, raloxifene reduced the maximum prothrombin time (PTmax) by 10% and the area under the PT versus time curve from 0-120 h (AUCPT) by 8% (p < 0.01). CONCLUSIONS: Raloxifene administration may result in a small increase in systemic warfarin exposure that is associated with a diminution, not augmentation, of the pharmacodynamic effect. Due to the small magnitude of this effect, concomitant administration of raloxifene and warfarin is not likely to result in clinically significant drug-drug interaction.

Administration, Oral↗

PubMed2001

The role of hormone replacement therapy in women with a previous diagnosis of breast cancer and a review of possible alternatives.

Estrogen replacement therapy either with (HRT) or without (ERT) accompanying progesterone is routinely offered to well women at the time of menopause, in order to relieve vasomotor symptoms, (hot flashes), reduce urogenital atrophy and reduce the risks of cardiovascular disease, osteoporosis and perhaps colon cancer and Alzheimer's disease. It is generally felt however, that women with a previous diagnosis of breast cancer are not suitable candidates for such therapy since either estrogen or progesterone may be associated with an increased risk of cancer recurrence. There are however, a variety of approaches to menopausal therapy in such women. A careful history must first be taken in order to identify the symptoms or conditions of concern. Vasomotor symptoms can be reduced by the use of other medications such as the antidepressant venlafaxine (Effexor). Estring, a vaginal estrogen ring can be used to reduce genitourinary symptoms, with little systemic estrogen absorption. Osteoporosis can be prevented or treated with calcium supplements, exercise, improved diet, bisphosphonates and/or selective estrogen receptor modulators (SERMs) while cardiovascular risk can be reduced by diet and exercise, as well as the appropriate use of lipid lowering and antihypertensive medications.

Alzheimer Disease↗