Regulation of insulin-like growth factors by antiestrogen

Assessment of IGF-1 expression in the peripheral blood of women with recurrent breast cancer

Breast cancer is the most common malignancy affecting women worldwide. The insulin-like growth factor 1 (IGF-1) gene encodes a protein responsible for a wide variety of physiological processes, including differentiation and cell proliferation. Despite several studies on tumor tissues, no study has evaluated IGF-1 expression in the peripheral blood of women with recurrent breast cancer.In this cross-sectional study, IGF-1 expression in the peripheral blood of 146 women with breast cancer treated approximately 5 years ago was quantified by quantitative reverse transcription polymerase chain. The women were divided into 2 groups: non-recurrence (n = 85) and recurrence (n = 61). Statistical analysis of the data was performed using ANOVA, Mann-Whitney, and Chi-squared tests (P < .05).The results showed no significant difference in IGF-1 expression between the non-recurrence and recurrence groups (P = .988). In the subgroups of patients with lymph node involvement, no statistically significant difference was observed in IGF-1 expression between women with recurrence and those non-recurrence (P = .113). In patients without lymph node metastases, IGF-1 messenger ribonucleic acid (mRNA) expression levels were significantly higher in the non-recurrence group than in the recurrence group (P = .019). Furthermore, using the median IGF-1 mRNA expression as the cutoff point, it was obtained a statistically significant difference in tumor histological grade among women with recurrent breast cancer (P = .042).These data showed significantly higher IGF-1 expression in women without lymph node metastases in the non-recurrence group compared with the recurrence group. In addition, a significant difference was observed in median IGF-1 mRNA expression in relation to tumor histological grade in women with recurrent breast cancer.

Growth Hormone Secretagogue Treatment in Hypogonadal Men Raises Serum Insulin-Like Growth Factor-1 Levels

Realizing the reported misuse of human growth hormone (GH), investigation of a safe alternative mechanism for increasing endogenous GH is needed. Several GH secretagogues are available, including GH-releasing peptides (GHRPs) GHRP-2 and GHRP-6, and the GH-releasing hormone analog, sermorelin (SERM). Insulin-like growth factor 1 (IGF-1) serves as a surrogate marker for GH. Here, the effect of GHRP/SERM therapy on IGF-1 levels is evaluated. A retrospective review of medical records was performed for 105 men on testosterone (T) therapy seeking increases in lean body mass and fat loss who were prescribed 100 mcg of GHRP-6, GHRP-2, and SERM three times daily. Compliance with therapy was assessed, and 14 men met strict inclusion criteria. Serum hormone levels of IGF-1, T, free T (FT), estradiol (E), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were evaluated. Mean (SD) age of the cohort was 33.2 (2.9) years, and baseline IGF-1 level was 159.5 (26.7) ng/mL. Mean (SD) duration of continuous GHRP/SERM treatment was 134 (88) days. Mean posttreatment IGF-1 level was 239.0 (54.6) ng/mL (p < .0001). Three of the 14 men were on an aromatase inhibitor and/or tamoxifen prior to treatment and another 4 men were coadministered an aromatase inhibitor and/or tamoxifen during treatment. Inhibition of E production or estrogen receptor blockade resulted in smaller increases in IGF-1 levels. GHRP/SERM therapy increases serum IGF-1 levels with strict compliance to thrice-daily dosing. The results suggest that combination therapy may be beneficial in men with wasting conditions that can improve with increased GH secretion.

Antihormonal agents as a strategy to improve the effect of chemo-radiation in cervical cancer: in vitro and in vivo study

Background

Over the past few years, the concurrent use of cisplatin-based chemotherapy and radiation therapy has dramatically improved the local response and increased overall survival in early-stage cervical cancer. However, for the advanced stages of the disease this standard treatment has proved insufficient. We investigated the capacity of Mifepristone and ICI 182,780, which are anti-progestin and anti-estrogen drugs, respectively, to act as chemo-radiosensitizing agents in cervical cancer cells and cervix xenografts.

Methods

The effect of chemo-radiation alone or combined with Mifepristone or ICI 182,780 was evaluated in HeLa cells and with tumor growth in cervix xenografts. After concomitant chemo-radiotherapy, the effect of each of these antihormonal agents on apoptosis (determined by Annexing V assay) and the cell cycle phases were determined by flow cytometry. The expression of angiogenic factor VEGF in tumor samples was determined using quantitative RT-PCR analysis of VEGF gene expression.

Results

Compared to radiation alone or radiation/cisplatin therapy, there was significantly higher cytotoxicity and a greater antitumoral effect with the combined application of radiation/cisplatin and Mifepristone or ICI 182,780. Analyses of the apoptosis and cell cycle demonstrated changes only with ICI, not with Mifepristone, when was applied in combination with radiation/cisplatin. The analysis of VEGF mRNA expression levels in tumors at the end of the study demonstrated a significant inhibition, compared to radiation only or the radiation/cisplatin treatment, after concurrent chemo-radiotherapy and each one of the antihormonal drugs.

Conclusion

Mifepristone and ICI 182,780 may be potentially promising chemo-radiosensitizing compounds to be used in combination with ionizing irradiation and cisplatin in the treatment of patients with advanced cervical 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.

Insulin-like growth factor-I and estrogen interactions in breast cancer

There is increasing evidence that estradiol and insulin-like growth factor-I (IGF-I) act through a complex cross-talk mechanism to stimulate the proliferation of normal mammary epithelium to increase the risk of breast cancer. The emerging model of cross-talk suggests that estradiol regulates the expression of IGF-I and the IGF receptor I. The subsequent binding of IGF-I to its receptor initiates an intracellular signal transduction pathway that activates transcription factors, including the estrogen receptor. Recent studies show that the effects of IGF-I on estrogen receptor activity are mediated in part by the protein kinase A and phosphatidylinositol-3-kinase/Akt pathways.

Mitogenic properties of insulin-like growth factors I and II, insulin-like growth factor binding protein-3 and epidermal growth factor on human breast epithelial cells in primary culture

Insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II) are growth factors implicated in mammary gland development and are believed to be involved in breast cancer. However, the interactions between components of the IGF system and breast epithelial cells, which give rise to breast cancer, are not well understood. We have investigated the mitogenic properties of IGF-I, IGF-II, IGF binding protein-3 (IGFBP-3) and epidermal growth factor (EGF) on human breast epithelial cells (HBEC) in primary culture. We show that, under serum-free conditions, HBEC are stimulated to grow in response to IGF-I and IGF-II in a dose-dependent manner. IGF-I and EGF, a potent stimulator of HBEC growth in primary culture and also associated with breast cancer, appear to stimulate HBEC in a synergistic manner. IGFBP-3 inhibits the stimulation by IGF-I, IGF-II and IGF-I plus EGE In addition, it appears that IGFBP-3 has an inhibitory effect on HBEC growth that is IGF-independent. This study is the first to address the effects of IGF-I, IGF-II and IGFBP-3 alone and in combination with EGF on HBEC growth in primary culture. Characterizing the role of the IGF system in normal breast biology is significant because the system has been implicated in breast cancer and a number of the anti-estrogens used in treatment are believed to function through the IGF system.

IGF status is altered by tamoxifen in patients with breast cancer

AIMS

An increased concentration of insulin-like growth factor 1 (IGF-1) is an independent risk factor for premenopausal breast cancer. Tamoxifen is thought initially to reduce concentrations of IGF-1 and increase concentrations of the IGF binding proteins. The aim of this study was to compare concentrations of IGF-1, IGF binding protein 1 (IGF-BP1), and IGF-BP3 in patients with breast cancer (n = 14) with those seen in control subjects (n = 23) and to assess the effect of tamoxifen on IGF status in these patients.

METHODS

Non-fasting blood samples were collected from patients with breast cancer before surgery and after nine, 18, and 27 months of tamoxifen treatment. The baseline concentrations were compared with those of age and sex matched healthy control subjects.

RESULTS

IGF-1, IGF-BP3, and IGF-BP1 concentrations were not significantly different in cases and controls. Tamoxifen treatment significantly increased IGF-BP1 after 18 and 27 months (baseline: mean, 21.6 ng/ml; SD, 16.6; 18 months: mean, 52.0 ng/ml; SD, 41.8; p = 0.019; 27 months: mean, 40.7 ng/ml; SD, 24.9; p = 0.043) and IGF-BP3 after nine, 18, and 27 months (baseline: mean, 3119 ng/ml; SD, 507; nine months: mean, 3673 ng/ml; SD, 476; p = 0.004; 18 months: mean, 3445 ng/ml; SD, 634; p = 0.034; 27 months: 3409 ng/ml; SD, 501; p = 0.043) when compared with baseline values. IGF-1 was not altered significantly from baseline at any time point. However, the IGF-1 to IGF-BP3 ratio was significantly decreased at both nine and 18 months (baseline: mean, 0.058; SD, 0.014; nine months: mean, 0.039; SD, 0.008; p = 0.033; 18 months: mean, 0.044; SD, 0.012; p = 0.01). This ratio was not significantly different from baseline at 27 months (mean, 0.054; SD, 0.01; p = 0.08).

CONCLUSIONS

Tamoxifen increases IGF-BP3 and IGF-BP1 concentrations. It also decreases the IGF-1 to IGF-BP3 ratio but this effect may be limited after long term use. Longer follow up, with larger numbers of patients, should determine when, and for how long, tamoxifen can reduce circulating IGF-1.

Role of insulin-like growth factor-I in regulating estrogen receptor-alpha gene expression

The role of insulin-like growth factor-I (IGF-I) in regulating estrogen receptor-alpha (ER-alpha) gene expression and activity was investigated in the human breast cancer cell line MCF-7. Treatment of cells with 40 ng/ml IGF-I resulted in a 60% decrease in ER-alpha protein concentration by 3 h, and the amount of ER-alpha remained suppressed for 24 h. A multiple-dose ligand-binding assay demonstrated that the decrease in ER-alpha protein corresponded to a similar decrease of 50% in estradiol-binding sites with no effect on the binding affinity of ER-alpha. The dissociation constant of the estradiol-ER-alpha complex in the absence of IGF-I (K(d) = 3 x 10(-10) +/- 0.5 x 10(-10) M) was similar to the dissociation constant in the presence of IGF-I (K(d) = 6 x 10(-10) +/- 0.3 x 10(-10) M). The decrease in ER-alpha protein concentration was paralleled by an 80% decrease in the steady-state amount of ER-alpha mRNA by 3 h. The IGF-I induced decrease in ER-alpha mRNA was due to the inhibition of ER-alpha gene transcription. When an 128-base pair ER-alpha-promoter-CAT construct was transfected into MCF-7 cells, treatment with IGF-I resulted in a 40% decrease in CAT activity. In contrast to the effects on ER-alpha, treatment with IGF-I induced two endogenous estrogen-regulated genes, progesterone receptor and pS2, by 4- and twofold, respectively. The pure antiestrogen ICI-164, 384 blocked this induction, suggesting that ER-alpha mediates the effects of IGF-I. Transient co-transfections of wild-type ER-alpha and an estrogen response element-CAT reporter into COS-1 cells demonstrated that IGF-I increased reporter gene activity. This effect was also blocked by ICI 164,384. Protein kinase A and phosphatidylinositol 3-kinase inhibitors blocked the IGF-I effects on ER-alpha expression and activity, suggesting that these kinases may be involved in the cross-talk between the IGF-I and ER-alpha pathways.

Expression of sex steroid receptors and IGF-1 mRNA in breast tissue--effects of hormonal treatment

The mechanisms behind increased breast tissue proliferation and a possibly increased breast cancer risk in women using hormonal contraception (HC) and hormonal replacement therapy (HRT) are incompletely understood. We analyzed breast tissue from 20 premenopausal and seven postmenopausal women undergoing reduction mammoplasties for estrogen receptor (ER) and progesterone receptor (PR) content as well as mRNA levels for ER, PR and insulin-like growth factor-1 (IGF-1). The receptor values were correlated to IGF-1 mRNA concentrations and levels of steroid and peptide hormones and SHBG. In women using HC, we found significantly lower ER values (p = 0.02) but non-significantly lower ER mRNA levels compared to those in naturally cycling women. PR and PR mRNA were no different. Women on HC displayed a higher breast tissue proliferation (p = 0.05) expressed as Ki-67, MIB-1 positivity, which was correlated with IGF-1 mRNA (r(s) = 0.82, p = 0.04). Since the concentration of sex steroid receptors in breast tissue is comparatively low and steroid receptors are down-regulated during hormonal treatment, mechanisms other than direct sex steroid receptor action are likely to be present. Our results suggest a role for IGF-1 in the proliferative response of breast tissue during exogenous hormonal treatment.

Induction of insulin-like growth factor binding protein expression by ICI 182,780 in a tamoxifen-resistant human breast cancer cell line

Earlier studies in our laboratory demonstrated that the steroidal antiestrogen ICI 182,780 is very effective in abolishing the tamoxifen-resistant proliferation of MCF 7/5-23 cells. In addition, preliminary binding studies showed that ICI 182,780 increased the binding of insulin-like growth factor (IGF)-I to the MCF 7/5-23 cells, although this finding was not the result of an increase in the expression of the insulin-like growth factor-I receptor (IGF-IR). Hence, we reasoned that the inhibition of tamoxifen-resistant cell growth by ICI 182,780 might have been due to increased expression of insulin-like growth factor binding proteins (IGFBPs). We observed the up-regulation of non-insulin-suppressible IGF-I binding in both the tamoxifen-sensitive MCF 7/5-21 cell line (1.5-fold) and the tamoxifen-resistant MCF 7/5-23 cell line (2.5-fold) after 5 days of treatment with ICI 182,780 (10(-7) M) in serum-free medium, suggesting a role for cell-associated IGFBPs. Affinity cross-linking experiments confirmed the presence of an IGF-I:IGFBP complex of approximately 38-kDa in tamoxifen or ICI 182,780-treated cells. Western ligand blots showed higher levels of a soluble 30-kDa IGFBP in media conditioned by either of the subclones that had been treated with ICI 182,780, an effect consistently opposed by estrogen (E2: 10(-9) M). RT-PCR showed higher levels of IGFBP-5 mRNA than any of the other known IGFBPs, suggesting that this was the major IGFBP subtype. The protein was subsequently identified by Western immunoblotting as IGFBP-5. In conclusion, we postulate that this may be a mechanism contributing to the greater potency of ICI 182,780 in the growth inhibition of the MCF 7/5-23, tamoxifen-resistant cell line.

Feasibility, endocrine and anti-tumour effects of a triple endocrine therapy with tamoxifen, a somatostatin analogue and an antiprolactin in post-menopausal metastatic breast cancer: a randomized study with long-term follow-up

Suppression of the secretion of prolactin, growth hormone and insulin-like growth factor 1 (IGF-1) might be important in the growth regulation and treatment of breast cancer. Because oestrogens may counteract the anti-tumour effects of such treatment, the combination of an anti-oestrogen (tamoxifen), a somatostatin analogue (octreotide) and a potent anti-prolactin (CV 205-502) might be attractive. In this respect, we performed a first exploratory long-term study on the feasibility of combined treatment and possible clear differences in endocrine and anti-tumour effects during such combined treatment vs standard treatment with tamoxifen alone. Twenty-two post-menopausal patients with metastatic breast cancer (ER and/or PR positive or unknown) were randomized to receive either 40 mg of tamoxifen per day or the combination of 40 mg of tamoxifen plus 75 microg of CV 205-502 orally plus 3 x 0.2 mg of octreotide s.c. as first-line endocrine therapy. An objective response was found in 36% of the patients treated with tamoxifen alone and in 55% of the patients treated with combination therapy. Median time to progression was 33 weeks for patients treated with tamoxifen and 84 weeks for patients treated with combination therapy, but the numbers are too small for hard conclusions. There was no difference in overall post-relapse survival between the two treatment arms. With respect to the endocrine parameters, there was a significant decrease of plasma IGF-1 levels in both treatment arms, whereas during combined treatment plasma growth hormone tended to decrease and plasma prolactin levels were strongly suppressed; in some patients insulin and transforming growth factor alpha (TGF-alpha) decreased during the triple therapy. Although there was no significant difference in mean decrease of plasma IGF-1 levels between the two treatment arms, combined treatment resulted in a more uniform suppression of IGF-1. Therefore, the addition of a somatostatin analogue and an anti-prolactin may potentially enhance the efficacy of anti-oestrogens in the treatment of breast cancer owing to favourable endocrine and possible direct anti-tumour effects. Large phase III trials using depot formulations (to increase the feasibility) of somatostatin analogues are warranted to demonstrate the potential extra beneficial anti-tumour effects of such combination therapy.

Associations between insulin-like growth factors and their binding proteins and other prognostic indicators in breast cancer

Recent studies have suggested that insulin-like growth factors (IGFs) and insulin-like growth factor binding proteins (IGFBPs) may be implicated in the development and progression of breast cancer. Prostate-specific antigen (PSA), a serine protease, may play a role in the regulation of IGFs' function through cleavage of IGFBP-3, resulting in release of active IGFs from IGFBP-3. As IGFs, IGFBPs and PSA are all present in breast cancer, possible associations among these proteins were speculated. In this study, we have measured PSA, IGF-I, IGF-II, IGFBP-1 and IGFBP-3 in tumour tissue cytosols from 200 women with primary breast cancer, and have examined relationships between IGFs or IGFBPs and PSA along with other markers, including p53 protein, steroid hormone receptors (oestrogen and progesterone), cathepsin-D, epidermal growth factor receptor, Her-2/neu protein, S-phase fraction and DNA ploidy. Correlations or associations between PSA and IGF-I, IGF-II, IGFBP-1 or IGFBP-3 were not observed. IGF-II was positively correlated with both IGFBP-3 and IGFBP-1. IGF-I was not associated with either of the two binding proteins, nor with IGF-II. Both IGF-II and IGFBP-3 were inversely associated with the oestrogen receptor, and IGFBP-3 was also positively associated with S-phase fraction. Our finding of IGF-II and IGFBP-3 in association with unfavourable prognostic indicators of breast cancer suggests that IGFs may be involved in the progression of breast cancer.

Novel endocrine therapies in breast cancer

Endocrine therapy of breast cancer consists of a variety of both medical and surgical ablative treatment modalities, but ablative therapy is increasingly replaced by medical treatment. Most endocrine therapies have more than one endocrine effect, frequently together with direct growth inhibitory actions via receptors. Endocrine therapy can be effective in all phases of the disease, but curative only in early disease while in advanced cancer it can only prolong survival. In the past decade the number of available endocrine agents has been drastically increased. Novel approaches in the endocrine therapy of breast cancer are application of new antiestrogens, antiprogestins, new potent aromatase inhibitors, analogues of luteinizing hormone-releasing hormone (LHRH-A) and somatostatin, inhibitors of prolactin secretion, vitamin A and D analogues, bisphosphonates, growth factor antagonists, tyrosine protein kinase inhibitors, protease inhibitors, inhibitors of angiogenesis, radiolabeled hormones and monoclonal antibodies. New cell biological factors such as oncogenes and suppressorgenes, secretory proteins and membrane receptors can be used not only as prognostic factors but also for prediction of type of response to endocrine and chemotherapy. Thus, these cell biological parameters can be used to select high and low risk patients, type of systemic treatment, and can also be used as targets for new treatment modalities. Future studies on treatment of all stages of disease will increasingly focus on promising combined treatment modalities.

Mechanisms of tamoxifen resistance in the treatment of advanced breast cancer

Multiple mechanisms may render breast cancer cells resistant to treatment with the antiestrogen tamoxifen. This review describes changes in the estrogen receptor (ER) signaling pathway which may lead to tamoxifen resistance: change in uptake or metabolism of tamoxifen, loss of expression of ER, decreased expression of ER, expression of mutant or variant forms of ER, intact ER but loss of cofactors, ligand-independent ER activation, modification of the estrogen response element, altered post-receptor events. Non-ER related alterations are also mentioned.