Effect of raloxifene on IGF-I and IGFBP-3 in postmenopausal women with breast cancer

Effects of raloxifene administration on serum levels of insulin-like growth factor-1 and insulin-like growth factor-binding protein 3 levels: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

To ascertain the clinical magnitude of raloxifene administration on insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-binding protein 3 (IGFBP-3) levels.

METHODS

A systematic comprehensive search was performed without language limitation up to 14 December 2020. We included only trials that assessed the effect of raloxifene on IGF-1 and IGFBP-3 in adults. Meta-analysis was performed using the Stata software (Stata Corp. College Station, Texas, USA).

RESULTS

Seven arms were included, encompassing postmenopausal women with type 2 diabetes mellitus, postmenopausal women with breast cancer, healthy postmenopausal women, and healthy elderly men. Raloxifene therapy significantly reduced IGF-1 levels (WMD: -2.92 nmol/L, 95% CI: -3.49, -2.35, p < 0.001) compared to placebo. Raloxifene dosage ˃60 mg/day (WMD: -3.29 ng/mL, 95% CI: -3.50 to -3.08, I² = 0.0%) decreased IGF-1 levels more than 60 mg/day (WMD: -2.29 ng/mL, 95% CI: -2.90 to -1.69, I² = 16%). Moreover, intervention duration ˃26 weeks (WMD: -3.48 ng/mL, 95% CI: -5.26 to -1.69, I² = 0.0%) reduced IGF-1 levels more than ˂26 weeks (WMD: -2.55 ng/mL, 95% CI: -3.31 to -1.79, I² = 92%). In contrast, overall results from the random-effects model did not suggest a significant change in IGFBP-3 levels upon raloxifene therapy.

CONCLUSION

Raloxifene therapy significantly reduced serum levels of IGF-1 levels but without changes in IGFPB-3 levels.

The effects of lycopene supplementation on serum insulin-like growth factor 1 (IGF-1) levels and cardiovascular disease: A dose-response meta-analysis of clinical trials

BACKGROUND

The results of human studies assessing the efficacy of lycopene on insulin-like growth factor 1 (IGF-1) levels are inconsistent. Thus, we performed a systematic review and meta-analysis to examine the effects of lycopene supplementation on serum IGF-1 levels and cardiovascular disease.

METHODS

The literature published up to January 2020 was searched using the electronic databases Scopus, PubMed/Medline, Web of Science, Embase and Google Scholar.

RESULTS

Seven qualified trials were included in the current meta-analysis. IGF-1 levels were non-significantly decreased in lycopene group compared to the control (WMD: -6.74 ng/mL, 95 % CI: -23.01 to 9.52, p = 0.42; I² = 94.3 %). Subgroup analysis revealed a significantly decrease in IGF-1 levels upon lycopene supplementation at doses ≥15 mg/d (WMD: -6.40 ng/mL), intervention period <12 weeks (WMD: -6.49 ng/mL), and subjects aged ≥60 years (WMD: -24.98 mg/dl). In addition, lycopene intake significantly reduced IGF-1 levels upon healthy conditions (WMD: -25.59 ng/mL) when compared with cancer patients (WMD: 0.35 ng/mL). In addition, the effect of lycopene supplementation was significant in patients diagnosed with cardiac disorders.

CONCLUSION

Overall, lycopene intake was not associated with reduced serum IGF-1 levels. However, association was significant when lycopene was administrated at doses >15 mg/d, for <12 weeks, as well as for healthy conditions and patients aged ≥60 years. In addition, lycopene supplementation exhibited potential health benefits in the management of patients with cardiac disorders.

Effect of Bazedoxifene and Conjugated Estrogen (Duavee) on Breast Cancer Risk Biomarkers in High-Risk Women: A Pilot Study

Interventions that relieve vasomotor symptoms while reducing risk for breast cancer would likely improve uptake of chemoprevention for perimenopausal and postmenopausal women. We conducted a pilot study with 6 months of the tissue selective estrogen complex bazedoxifene (20 mg) and conjugated estrogen (0.45 mg; Duavee) to assess feasibility and effects on risk biomarkers for postmenopausal breast cancer. Risk biomarkers included fully automated mammographic volumetric density (Volpara), benign breast tissue Ki-67 (MIB-1 immunochemistry), and serum levels of progesterone, IGF-1, and IGFBP3, bioavailable estradiol and testosterone. Twenty-eight perimenopausal and postmenopausal women at increased risk for breast cancer were enrolled: 13 in cohort A with baseline Ki-67 < 1% and 15 in cohort B with baseline Ki-67 of 1% to 4%. All completed the study with > 85% drug adherence. Significant changes in biomarkers, uncorrected for multiple comparisons, were a decrease in mammographic fibroglandular volume (P = 0.043); decreases in serum progesterone, bioavailable testosterone, and IGF-1 (P < 0.01), an increase in serum bioavailable estradiol (P < 0.001), and for women from cohort B a reduction in Ki-67 (P = 0.017). An improvement in median hot flash score from 15 at baseline to 0 at 6 months, and menopause-specific quality-of-life total, vasomotor, and sexual domain scores were also observed (P < 0.001). Given the favorable effects on risk biomarkers and patient reported outcomes, a placebo-controlled phase IIB trial is warranted.

Estrogens and selective estrogen receptor modulators in acromegaly

Despite recent advances in acromegaly treatment by surgery, drugs, and radiotherapy, hormonal control is still not achieved by some patients. The impairment of IGF-1 generation by estrogens in growth hormone deficient patients is well known. Patients on oral estrogens need higher growth hormone doses in order to achieve normal IGF-1 values. In the past, estrogens were one of the first drugs used to treat acromegaly. Nevertheless, due to the high doses used and the obvious side effects in male patients, this strategy was sidelined with the development of more specific drugs, as somatostatin receptor ligands and dopamine agonists. In the last 15 years, the antagonist of growth hormone receptor became available, making possible IGF-1 control of the majority of patients on this particular drug. However, due to its high cost, pegvisomant is still not available in many centers around the world. In this setting, the effect of estrogens and also of selective estrogen receptor modulators on IGF-1 control was reviewed, and proved to be an ancillary tool in the management of acromegaly. This review describes data concerning their efficacy and place in the treatment algorithm of acromegaly.

Administration of omega-3 fatty acids and Raloxifene to women at high risk of breast cancer: interim feasibility and biomarkers analysis from a clinical trial

BACKGROUND/OBJECTIVES

The antiestrogen, Raloxifene (Ral) is an effective breast cancer chemopreventive agent. Omega-3 fatty acids (n-3FA) may inhibit mammary carcinogenesis. On the basis of their mechanisms of action, we test the hypothesis that a combination of n-3FA and Ral may be superior in reducing select biomarkers of breast cancer risk in women.

SUBJECTS/METHODS

Postmenopausal women at increased risk for breast cancer (breast density ≥ 25%) were randomized to: (1) no intervention; (2) Ral 60 mg; (3) Ral 30 mg; (4) n-3FA (Lovaza) 4 g and (5) Lovaza 4 g+Ral 30 mg for 2 years. Reduction in breast density is the primary end point of the study. We report preliminary data on feasibility, compliance and changes in secondary end points related to IGF-I signaling, estrogen metabolism, oxidative stress and inflammation in the first group of 46 women who completed 1 year of the study.

RESULTS

All interventions were well tolerated with excellent compliance (96 ± 1% overall) by pill count and also supported by the expected rise in both serum n-3FA and n-3FA/Omega-6 fatty acids (n-6FA) ratio in women randomized to groups 4 and 5 (P<0.05). Lovaza decreased serum triglycerides and increased high-density lipoprotein (HDL) cholesterol compared with control (P<0.05 for both). Ral reduced serum IGF-1 in a dose-dependent manner (P<0.05) while Lovaza did not. Lovaza had no effect on IGF-1 or IGFBP-3. None of the other biomarkers were affected by our treatment.

CONCLUSION

The combination of Lovaza and Ral is a feasible strategy that may be recommended in future breast cancer chemoprevention trials.

Differential effects of raloxifene and estrogen on body composition in growth hormone-replaced hypopituitary women

CONTEXT

GH deficiency causes reduction in muscle and bone mass and an increase in fat mass (FM), the changes reversed by GH replacement. The beneficial effects of GH on fat oxidation and protein anabolism are attenuated more markedly by raloxifene, a selective estrogen receptor modulator, compared with 17β-estradiol. Whether this translates to a long-term detrimental effect on body composition is unknown.

OBJECTIVE

Our objective was to compare the effects of 17β-estradiol and raloxifene on FM, lean body mass (LBM), and bone mineral density (BMD) during GH replacement.

DESIGN

This was an open-label randomized crossover study.

PATIENTS AND INTERVENTION

Sixteen hypopituitary women received GH (0.5 mg/d) replacement for 24 months. One group received 17β-estradiol (2 mg/d) for the first 6 months before crossover to raloxifene (60 mg/d) for the remaining 18 months; the other received the reversed sequence.

MAIN OUTCOME MEASURES

Serum IGF-I and IGF-binding protein-3 concentrations, and FM, LBM, lumbar spine and femoral neck BMD were analyzed at baseline and at 6, 12, and 24 months within and between subjects.

RESULTS

GH therapy significantly increased mean IGF-I during 17β-estradiol and raloxifene cotreatments equally, but elevated IGF-binding protein-3 to a greater extent during raloxifene cotreatment. GH cotreatment with 17β-estradiol increased LBM and lumbar spine and femoral neck BMD and reduced FM to a greater extent than with raloxifene.

CONCLUSIONS

In hypopituitary women, raloxifene at therapeutic doses significantly attenuated the beneficial effects of GH on body composition compared with 17β-estradiol. Raloxifene has no metabolic advantage over 17β-estradiol during GH replacement.

Modulatory effect of raloxifene and estrogen on the metabolic action of growth hormone in hypopituitary women

CONTEXT

The metabolic action of GH is attenuated by estrogens administered via the oral route. Selective estrogen receptor modulators lower IGF-I to a lesser degree than 17beta-estradiol in GH-deficient women, and their effect on fat and protein metabolism is unknown.

OBJECTIVE

The aim of the study was to compare the modulatory effects of 17beta-estradiol and raloxifene, a selective estrogen receptor modulator, on the metabolic action of GH.

DESIGN

We conducted an open-label, two-group, randomized, two-period crossover study.

PATIENTS AND INTERVENTION

Ten hypopituitary women received GH therapy alone (0.5 mg/d) and GH plus 17beta-estradiol (E(2); 2 mg/d). Eleven hypopituitary women received GH therapy alone and GH plus raloxifene (R; 60 mg/d). The treatment duration was 1 month, with a 4-wk washout period.

MAIN OUTCOME MEASURES

IGF-I, IGFBP-3, resting energy expenditure, and fat oxidation were quantified by indirect calorimetry. We measured whole body leucine turnover from which leucine rate of appearance and leucine incorporation into protein were estimated.

RESULTS

GH significantly stimulated all outcome measures. During GH treatment, addition of R significantly reduced mean IGF-I but not IGFBP-3, whereas E(2) reduced both IGF-I and IGFBP-3 levels. Cotreatment with R but not E(2) significantly attenuated the stimulatory effects of GH on fat oxidation. There was a strong trend (P = 0.08) toward a greater reduction in leucine incorporation into protein after R compared to E(2) cotreatment.

CONCLUSIONS

The modulatory effects of E(2) and R at therapeutic doses on GH action are different. R during GH therapy exerts a greater inhibitory effect on lipid oxidation and protein anabolism compared to E(2).

Raloxifene: a review of its use in the prevention of invasive breast cancer

Raloxifene (Evista) is a second-generation selective estrogen receptor modulator (SERM) that functions as an estrogen antagonist on breast and uterine tissues, and an estrogen agonist on bone. It is available in many countries worldwide for the treatment and prevention of osteoporosis in postmenopausal women, and has also been approved in the US for reducing the risk of invasive breast cancer in postmenopausal women with osteoporosis or postmenopausal women at increased risk of invasive breast cancer.Raloxifene reduces the risk of invasive breast cancer in postmenopausal women at high risk of invasive breast cancer and in postmenopausal women with osteoporosis. In addition, it is a well established agent for the prevention and treatment of osteoporosis. There was no significant difference between raloxifene and tamoxifen in the reduction in the risk of invasive breast cancer achieved in postmenopausal women at high risk of such cancer. Raloxifene was associated with an increased, albeit rare, risk of venous thromboembolism across several placebo-controlled trials and an increased risk of fatal stroke in one placebo-controlled trial in postmenopausal woman at increased risk for major coronary events. However, raloxifene was associated with a lower risk of venous thromboembolic events and cataracts than tamoxifen in a head-to-head trial. The choice of chemoprevention agent must consider a risk-benefit assessment for each individual patient. In this context, raloxifene is a valuable option for the prevention of invasive breast cancer in postmenopausal women with osteoporosis or at high risk of invasive breast cancer.

Tomato lycopene extract supplementation decreases insulin-like growth factor-I levels in colon cancer patients

Epidemiological studies have shown that high serum levels of insulin-like growth factor-I are associated with an increased risk of colon and other types of cancer. The aim of this study was to determine whether short intervention with dietary tomato lycopene extract will affect serum levels of the insulin-like growth factor system components in colon cancer patients. The study had a double-blind, randomized, placebo-controlled design. Colon cancer patients (n=56), candidates for colectomy, were recruited from the local community a few days to a few weeks before surgery. Personal and medical data were recorded. Plasma concentrations of insulin-like growth factor-I and II and insulin-like growth factor-I-binding protein-3 were assayed by routine laboratory methods. Lycopene was assayed by high-performance liquid chromatography. Plasma lycopene levels increased by twofold after supplementation with tomato lycopene extract. In the placebo-treated group, there was a small nonsignificant increase in lycopene plasma levels. The plasma concentration of insulin-like growth factor-I decreased significantly by about 25% after tomato lycopene extract supplementation as compared with the placebo-treated group (P<0.05). No significant change was observed in insulin-like growth factor-I-binding protein-3 or insulin-like growth factor-II, whereas the insulin-like growth factor-I/insulin-like growth factor-I-binding protein-3 molar ratio decreased significantly (P<0.05). Given that high plasma levels of insulin-like growth factor-I have been suggested as a risk factor for various types of cancer including colon cancer, the results support our suggestion that tomato lycopene extract has a role in the prevention of colon and possibly other types of cancer.

Evaluation of insulin-like growth factor-I in postmenopausal women with breast cancer treated with raloxifene

Background

The objective of this study was to evaluate serum IGF-I levels in postmenopausal women with breast cancer treated primarily with raloxifene.

Methods

Twenty-two postmenopausal patients with operable, stage I or II, estrogen receptor-positive carcinomas participated in this study. Following confirmation of diagnosis, the patients received 60 mg of raloxifene for 28 days prior to definitive surgery. Blood samples were collected for evaluation of serum IGF-I levels prior to initiating medication and following a 28-day treatment course. Student's t-test for paired samples was used in the statistical analysis. Significance was established at p < 0.05.

Results

Mean serum IGF-I levels pre- and post-raloxifene treatment were 143.7 ± 9.7 ng/ml and 94.8 ± 7.6 ng/ml, respectively. This reduction in serum IGF-I levels following treatment with raloxifene was statistically significant (p < 0.001).

Conclusion

Raloxifene significantly reduced serum IGF-I levels in postmenopausal women with breast cancer.

Regulation of growth hormone signaling by selective estrogen receptor modulators occurs through suppression of protein tyrosine phosphatases

Activation of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 5 (STAT5) pathway by GH is terminated by the suppressors of cytokine signaling (SOCSs) and protein tyrosine phosphatases, Src homology 2 domain-containing protein tyrosine phosphatase (SHP)-1 and SHP-2. Based on our recent report that estrogen inhibits GH signaling by stimulating SOCS-2 expression, we investigated the effects of selective estrogen receptor modulators (SERMs) on GH signaling in human embryonic kidney (HEK293) and breast cancer (MDA-MB-231) cells expressing human GH receptor and estrogen receptor-alpha. 17beta-estradiol (E(2)) suppressed GH activation of a STAT5-responsive luciferase reporter and JAK2 phosphorylation in both cell models. 4-hydroxytamoxifen and raloxifene augmented these actions of GH in HEK293 cells but not breast cancer cells. SOCS-2 expression in both cell types was stimulated by E(2) but unaffected by SERMs. In HEK293 cells, SHP-1 was inhibited by raloxifene and 4-hydroxytamoxifen, whereas the latter additionally inhibited SHP-2. The phosphatases were unaffected by E(2). In breast cancer cells, phosphatase activity was not altered by SERMs or E(2). In summary, estrogen inhibited the JAK2/STAT5 signaling of GH and stimulated SOCS-2 expression in both HEK293 and breast cancer cells. By contrast, SERMs augmented GH signaling by reducing SHP activities in HEK293 cells and had no effect on both in breast cancer cells. We provide the first evidence for a novel mechanism regulating GH signaling, in which SERMs enhance GH activation of the JAK2/STAT5 pathway in a cell-type-dependent manner by attenuating protein tyrosine phosphatase activities.

Circulating Insulin-Like Growth Factor-I and Binding Protein-3 and the Risk of Breast Cancer

Four meta-analyses and literature reviews have concluded that a positive association exists between circulating levels of insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) and breast cancer risk for premenopausal but not postmenopausal women. Recently, a large prospective study reported an association with IGF-I and IGFBP-3 concentration for breast cancer diagnosed after, but not before, the age of 50 years; and in a large cohort of primarily premenopausal women, IGF-I and IGFBP-3 were not associated with breast cancer risk. We did a case-cohort study within the Melbourne Collaborative Cohort Study, which included a random sample of 1,901 women (subcohort) and 423 breast cancer cases diagnosed during a mean of 9.1 years of follow-up. IGF-I and IGFBP-3 concentrations were measured in plasma collected at baseline. The association between quartiles of IGF concentration and breast cancer risk was tested using a Cox model adjusted for known and potential confounders. The hazard ratio (HR) for breast cancer comparing the fourth with the first quartiles was 1.20 [95% confidence interval (95% CI), 0.87-1.65] for IGF-I and 1.09 (95% CI, 0.78-1.53) for IGFBP-3. Both associations varied with age: for IGF-I, the HRs for breast cancer comparing the fourth with the first quartiles were 0.60 (95% CI, 0.25-1.45) before age 50 and 1.61 (95% CI, 1.04-2.51) after age 60 (test for the log-linear trend of HR according to age, P = 0.05); for IGFBP-3, the HRs were 0.79 (95% CI, 0.34-1.83) before age 50 and 1.62 (95% CI, 1.03-2.55) after age 60 (test for log-linear trend, P = 0.08). IGF-I and IGFBP-3 were positively associated with breast cancer risk in older women but not in younger women. More prospective studies are needed to clarify the age dependence of the association between IGF-I and IGFBP-3 and breast cancer.

Insulin-like growth factors and breast cancer therapy

Despite improvements in breast cancer therapy in recent years, additional therapies need to be developed. New therapies may have activity by themselves or may have utility in combination with other agents. Population, preclinical, and basic data suggest the insulin-like growth factor (IGF) system functions to maintain the malignant phenotype in breast cancer. Since the IGFs act via transmembrane tyrosine kinase receptors, targeting of the key receptors could provide a new pathway in breast cancer. In addition, IGF action enhances cell survival, so combination of anti-IGF therapy with conventional cytotoxic drugs could lead to synergistic effects. In this review, we will discuss the rationale for targeting the IGF system, potential methods to disrupt IGF signaling, and identify potential interactions between IGF inhibitors and other anti-tumor strategies. We will also identify important issues to consider when designing clinical trials.

Absence of the full-length breast cancer-associated gene-1 leads to increased expression of insulin-like growth factor signaling axis members

The breast cancer-associated gene-1 (BRCA1) plays many important functions in multiple biological processes/pathways. Mice homozygous for a targeted deletion of full-length BRCA1 (Brca1Delta11/Delta11) display both increased tumorigenesis and premature aging, yet molecular mechanisms underlying these defects remain elusive. Here, we show that Brca1 deficiency leads to increased expression of several insulin-like growth factor (IGF) signaling axis members in multiple experimental systems, including BRCA1-deficient mice, primary mammary tumors, and cultured human cells. Furthermore, we provide evidence that activation of IGF signaling by BRCA1 deficiency can also occur in a p53-independent fashion. Our data indicate that BRCA1 interacts with the IRS-1 promoter and inhibits its activity that is associated with epigenetic modification of histone H3 and histone H4 to a transcriptional repression chromatin configuration. We further show that BRCA1-deficient mammary tumor cells exhibit high levels of IRS-1, and acute suppression of Irs-1 using RNA interference significantly inhibits growth of these cells. Those observations provide a molecular insight in understanding both fundamental and therapeutic BRCA1-associated tumorigenesis and aging.

Is there an estrogenic component in the metabolic syndrome?

One of the major upcoming concerns leading to health related problems in the industrialized societies is the metabolic syndrome which is characterized by central obesity, hypertension, raised fasting glucose and triglyceride levels. The focus of this review is on a potential estrogenic linkage between the metabolic mechanisms involved into the development of this disease cluster and specific estrogen related regulatory pattern. The candidate molecules for this link are insulin and insulin-like growthfactor, C-reactive protein, peroxisome-proliferation-activatingreceptorgamma, and leptin which all seem to interact with each other and show a responsiveness to changing estrogen levels. From this perspective they might also represent target molecules for a phytochemical intervention with phytoestrogens.

Raloxifene increases serum leptin levels in postmenopausal women: a prospective study

OBJECTIVE

The purpose of this study was to investigate the effect of raloxifene on leptin and insulin-like growth factor-I levels and their relation with the biochemical markers of bone metabolism in postmenopausal women.

STUDY DESIGN

Sixty-four women were given 60 mg/d raloxifene for 6 months. Serum leptin, insulin-like growth factor-I, alkaline phosphatase, calcium, osteocalcin, and collagen type I cross-link C-telopeptide levels were measured before and after the treatment. The patients were grouped as obese (body mass index, > or =25 kg/m2) or non-obese (body mass index, <25 kg/m2).

RESULTS

The mean basal leptin level was significantly higher (P < .001), and the mean cross-link C-telopeptide level was significantly lower (P = .001) in obese patients. Raloxifene therapy increased leptin levels (P < .001) and decreased insulin-like growth factor-I, alkaline phosphatase, and cross-link C-telopeptide levels significantly (P < .001). There was a strong negative correlation between leptin and cross-link C-telopeptide (r = -0.703; P < .001). Insulin-like growth factor-I was not correlated with any parameter.

CONCLUSION

Raloxifene increases serum leptin levels while decreasing bone resorption in postmenopausal women.

Anti-growth factor activities of benzothiophenes in human breast cancer cells

We have tested the effects of two Eli-Lilly compounds, LY 117, 018 and raloxifene, on E2-regulated and IGF-I-induced proliferation or AP-1 activity in human breast cancer cells. We now demonstrate that both molecules have strong antiestrogenic and anti-growth factor inhibitory effects in MCF7 cells. They were as potent as ICI 182, 780 and more efficient than OH-Tam to prevent estradiol action whereas their inhibition on IGF-I stimulation was less than with ICI 182, 780 and equivalent to that of OH-Tam. Moreover, raloxifene was the most efficient molecule to prevent IGF-I-induced AP-1 activity, with a significant effect observed with a concentration as low as 5 x 10(-11)M in the presence of IGF-I alone. Similar dose-response curves were obtained with a combined treatment of IGF-I and E2 with a 2log shift. Their action on IGF-I-induced proliferation was completely abrogated in MCF7 transfectants in which the expression of an antiestrogen-regulated protein tyrosine phosphatase, PTPL1, was abolished by antisense RNA transfection. Accordingly, they were both able to dose-dependently regulate the expression of PTPL1 and to interfere with the PI3-K/Akt pathway by drastically decreasing Akt phosphorylation exclusively in wild-type PTPL1 expressing cells. Our data altogether demonstrate that raloxifene has a potent inhibitory effect on IGF-I action, with a drastic effect on AP-1 triggered responses as well as on Akt phosphorylation, suggesting that it might be a useful therapeutic agent in tumors in which these signalling pathways become constitutively active.

Factors associated with circulating levels of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in 740 women at risk for breast cancer

Prospective studies have shown an association between elevated plasma levels of insulin-like growth factor-I (IGF-I) and/or decreased levels of its major circulating carrier protein insulin-like growth factor binding protein-3 (IGFBP-3) and increased risk of major cancers. Identifying the factors which affect these biomarkers is of particular interest as subjects at increased risk could benefit from lifestyle changes, and/or chemoprevention intervention. We evaluated the association between constitutional, hormonal and clinical factors and IGF-I and IGFBP-3 in 740 women, including 376 unaffected women and 364 women with intraepithelial neoplasia (IEN) or early invasive breast cancer enrolled in breast cancer chemoprevention trials, conducted at a single institution. Age, body mass index (BMI), height, waist to hip girth ratio (WHR), parity, menopausal status, age at menarche, number of affected first degree relatives, number of biopsies and breast cancer status were considered in the analysis. Women with early breast cancer had 21% higher IGF-I levels (p = 0.033) and 19% higher IGF-I/IGFBP-3 molar ratio (p = 0.047) than unaffected women. In unaffected women, age was negatively associated with IGF-I (p = 0.002) and IGF-I/IGFBP-3 (p = 0.001), while age at menarche was negatively associated with IGFBP-3 levels (p = 0.043). In women with IEN or early breast cancer, IGF-I levels were negatively associated with age (p < 0.001), and positively associated with prior biopsies for benign disease (p = 0.013), while age, parity and menopausal status were significant predictors of IGF-I/IGFBP-3 molar ratio. We conclude that circulating IGF-I levels are higher in women with prior breast cancer compared to unaffected women, and that IGF-I and/or IGFBP-3 levels are influenced by age and by reproductive and hormonal factors. These findings support their putative role as breast cancer risk biomarker.

Targeting multiple signaling pathways as a strategy for managing prostate cancer: multifocal signal modulation therapy

The aberrant behavior of cancer reflects upregulation of certain oncogenic signaling pathways that promote proliferation, inhibit apoptosis, and enable the cancer to spread and evoke angiogenesis. Theoretically, it should be feasible to decrease the activity of these pathways-or increase the activity of pathways that oppose them-with noncytotoxic agents. Since multiple pathways are dysfunctional in most cancers, and cancers accumulate new oncogenic mutations as they progress, the greatest and most durable therapeutic benefit will likely be achieved with combination regimens that address several targets. Thus, a multifocal signal modulation therapy (MSMT) of cancer is proposed. This concept has already been documented by researchers who have shown that certain combinations of signal modulators-of limited utility when administered individually-can achieve dramatic suppression of tumor growth in rodent xenograft models. The present essay attempts to guide development of MSMTs for prostate cancer. Androgen ablation is a signal-modulating measure already in standard use in the management of delocalized prostate cancer. The additional molecular targets considered here include the type 1 insulin-like growth factor receptor, the epidermal growth factor receptor, mammalian target of rapamycin, NF-kappaB, hypoxia-inducible factor-1alpha, hsp90, cyclooxygenase-2, protein kinase A type I, vascular endothelial growth factor, 5-lipoxygenase, 12-lipoxygenase, angiotensin II receptor type 1, bradykinin receptor type 1, c-Src, interleukin-6, ras, MDM2, bcl-2/bclxL, vitamin D receptor, estrogen receptor-beta, and PPAR-. Various nutrients and phytochemicals suspected to have potential utility in prostate cancer prevention and therapy, but whose key molecular targets are still unknown, might reasonably be incorporated into MSMTs for prostate cancer; these include lycopene, selenium, green tea polyphenols, genistein, and silibinin. MSMTs can be developed systematically by testing various combinations of signal-modulating agents, in concentrations that can feasibly be achieved and maintained clinically, on human prostate cancer cell lines; combinations that appear promising can then be tested in xenograft models and, ultimately, in the clinic. Some signal modulators can increase response to cytotoxic drugs by upregulating effectors of apoptosis. When MSMTs fail to raise the spontaneous apoptosis rate sufficiently to achieve tumor stasis or regression, incorporation of appropriate cytotoxic agents into the regimen may improve the clinical outcome.

GH receptor antagonist: mechanism of action and clinical utility

This review focuses on the development of GH receptor antagonist as a novel agent for treatment of acromegaly, its mechanism of action and potential areas of use. A brief overview of acromegaly, its diagnosis and existing medical, surgical and radiotherapy options of treatment is necessary to justify the addition of yet another therapeutic modality to the already vast therapeutic armamentarium.

Role of raloxifene in breast cancer prevention in postmenopausal women: clinical evidence and potential mechanisms of action

BACKGROUND

Raloxifene is a selective estrogen-receptor modulator (SERM) indicated for the prevention and treatment of osteoporosis in postmenopausal women. In the Multiple Outcomes of Raloxifene Evaluation (MORE) study, an osteoporosis treatment trial, raloxifene therapy was associated with a reduced incidence of invasive, estrogen receptor (ER)-positive breast cancer compared with placebo (relative risk, 0.16; 95% CI, 0.09-0.30).

OBJECTIVE

This review summarizes available preclinical and clinical data pertaining to a potential role for raloxifene in the prevention of breast cancer, and examines the mechanisms of action by which raloxifene may exert an effect.

METHODS

Relevant articles were identified through a search of MEDLINE for English-language studies published between 1966 and January 2003. Search terms included raloxifene, keoxifene, tamoxifen, SERM, estrogen, estrogen receptor, breast, mammary, growth factors, and apoptosis. The reference lists of identified articles were reviewed for additional publications.

RESULTS

Both preclinical and clinical data suggest a role for raloxifene in the prevention of breast cancer. Like tamoxifen, raloxifene acts as an estrogen antagonist in breast tissue through competitive binding to the ER. Raloxifene may also inhibit breast tissue proliferation through mechanisms independent of the ER.

CONCLUSIONS

Given raloxifene's mechanism of action and the preclinical evidence for its role in breast cancer prevention, a clinically favorable effect seems feasible. Results of ongoing clinical studies will provide evidence to support or refute the clinical findings of MORE and thus raloxifene's role in the breast cancer prevention.

Effects of conjugated equine estrogen vs. raloxifene on serum insulin-like growth factor-i and insulin-like growth factor binding protein-3: a 2-year, double-blind, placebo-controlled study

OBJECTIVE

To assess and compare the effect of conjugated estrogen and of the selective estrogen receptor modulator raloxifene on serum levels of insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) and on the IGF-I/IGFBP-3 ratio.

DESIGN

A 2-year randomized, double-blind, placebo-controlled study.

SETTING

Endocrinology outpatient department.

PATIENT(S)

Fifty-six postmenopausal, hysterectomized women.

INTERVENTION(S)

Women received raloxifene hydrochloride in doses of 60 mg/day (n = 15) or 150 mg/day (n = 13), conjugated equine estrogen (CEE) in doses of 0.625 mg/day (n = 15), or a placebo (n = 13) over the course of 2 years.

MAIN OUTCOME MEASURE(S)

At baseline and after 6, 12, and 24 months of treatment, serum levels of IGF-I, IGFBP-3, and insulin were measured, and an IGF-I/IFGBP-3 ratio was calculated.

RESULT(S)

Both raloxifene and CEE decreased serum IGF-I concentration. In contrast to CEE, which had no effect, both raloxifene doses of 60 and 150 mg/day significantly increased serum IGFBP-3 during the 2 years. Compared with placebo, the decrease in IGF-I/IGFBP-3 ratio was -32.5% (95% CI: -20.1; -44.8%) for CEE; -16.4% (95% CI: -3.6; -29.2%) for raloxifene at 150 mg/day; and -15.4% (95% CI: -1.0; -29.8%) for raloxifene at 60 mg/day. No effect of CEE or raloxifene was found on insulin concentration at any time point.

CONCLUSION(S)

Long-term use of both CEE and raloxifene decreases serum IGF-I and the IGF-I/IGFBP-3 ratio, but, unlike CEE, raloxifene produced a significant yet small increase in IGFBP-3.

Growth factor receptors in breast cancer: potential for therapeutic intervention

Increased expression and activation of receptor tyrosine kinases occurs frequently in human breast carcinomas. Several therapies targeting these receptors are currently in clinical trials. Therapeutic strategies include blockade of individual receptors with monoclonal antibodies and inhibition of tyrosine kinase function. Trastuzumab is the first of these biologic therapies to be approved for patients with human epidermal growth factor receptor 2 (HER2)-overexpressing metastatic breast cancer. Novel trastuzumab-based combinations are being investigated in patients with advanced breast cancer. Large clinical trials have also been launched in the adjuvant setting. Small molecules that inhibit specific tyrosine kinases (e.g., epidermal growth factor receptor, HER2) are in phase I and phase II clinical trials. Other growth-factor-targeted drugs that have reached clinical development include STI571 and antibodies directed at the insulin-like growth factor pathway. Biologic therapies directed against these important receptors are promising. In this review we discuss challenges and opportunities for the development of growth-factor-targeted approaches for the treatment of breast cancer.

Soy isoflavones do not modulate circulating insulin-like growth factor concentrations in an older population in an intervention trial

Insulin-like growth factors (IGF) are essential for normal growth and maintenance of lean muscle mass; however, high insulin-like growth factor-I (IGF-I) and low IGF binding protein-3 (IGFBP-3) levels are also associated with several cancers. To test the hypothesis that long-term soy isoflavone supplementation decreases circulating IGF-I concentrations, we conducted a controlled, parallel-arm, double-blind intervention study with 150 participants (85% men), 50-80 y old. Participants were randomly assigned to consume a soy beverage powder daily for 12 mo. The active treatment group (+ISO) received soy protein containing 83 mg isoflavones, whereas the comparison group (-ISO) received soy protein containing 3 mg isoflavones. Serum IGF-I and IGFBP-3 were measured by ELISA. Mean change in serum IGF-I concentrations was similar in the two groups (+1.4 nmol/L in +ISO, +1.2 nmol/L in -ISO; P = 0.74, 95% confidence interval -1.1, +1.5 nmol/L for the 0.21 nmol/L difference between groups), indicating no effect of the isoflavone intervention. Similarly, the changes in IGFBP-3 and the IGF-I/IGFBP-3 ratio were similar in both groups, again showing no effect of +ISO treatment. A 12 mo, 83 mg/d soy isoflavone intervention did not modulate serum IGF in an older, mostly male population.

Molecular prognostic factors for breast cancer metastasis and survival

The biological characteristics of the tumor are used to estimate prognosis and select appropriate systemic therapy for patients with early-stage breast cancer. Well-established molecular prognostic factors include the estrogen and progesterone receptors, proliferation markers, and the HER2 gene. Novel tumor markers with potential clinical utility include molecules involved in cell transformation, invasion, and metastases. We review the available data supporting the utility of established prognostic and predictive molecular factors, and discuss challenges for integrating novel molecular markers into clinical practice.