IGF system components as prognostic markers in breast cancer

Proteomic analysis of combined IGF1 receptor targeted therapy and chemotherapy identifies signatures associated with survival in breast cancer patients

Clinical, epidemiological and experimental data identified the insulin-like growth factor-1 receptor (IGF1R) as a candidate therapeutic target in oncology. While this paradigm is based on well-established biological facts, including the potent anti-apoptotic and cell survival capabilities of the receptor, most Phase III clinical trials designed to target the IGF1R led to disappointing results. The present study was aimed at evaluating the hypothesis that combined treatment composed of selective IGF1R inhibitor along with classical chemotherapy might be more effective than individual monotherapies in breast cancer treatment. Analyses included comprehensive measurements of the synergism achieved by various combination regimens using the CompuSyn software. In addition, proteomic analyses were conducted to identify the proteins involved in the synergistic killing effect at a global level. Data presented here demonstrates that co-treatment of IGF1R inhibitor along with chemotherapeutic drugs markedly improves the therapeutic efficiency in breast cancer cells. Of clinical relevance, our analyses indicate that high IGF1R baseline expression may serve as a predictive biomarker for IGF1R targeted therapy. In addition, we identified a ten-genes signature with potential predictive value. In conclusion, the use of a series of bioinformatics tools shed light on some of the biological pathways that might be responsible for synergysm in cancer therapy.

Expression of insulin-like growth factor-1 receptor in circulating tumor cells of patients with breast cancer is associated with patient outcomes

In patients with breast cancer, markers of aggressiveness such as dysregulation of the insulin-like growth factor receptor (IGF1R) system and E-cadherin loss are commonly observed. Reduced IGF1R expression is correlated with decreased E-cadherin levels and increased cell motility. We assessed IGF1R and E-cadherin expression in circulating tumor cells (CTCs) in patients with breast cancer. Peripheral blood mononuclear cells of early (n = 87)- and metastatic (n = 126)-stage breast cancer patients (obtained prior to adjuvant and first-line chemotherapy) were evaluated using double immunofluorescence (IF) staining for cytokeratin (CK) and IGF1R. Triple IF using CK, IGF1R, and E-cadherin antibodies was performed in selected CTC(+) patients. IGF1R(+) CTCs were more frequently observed in early disease than in metastatic disease (86% vs 68% of CTCs, P = 0.04) stage, whereas IGF1R(-) CTCs were more common in metastatic than in early disease (32% vs 14% of CTCs, P = 0.002). 100% of CTC(+) patients with early disease, compared to 79% of those with metastatic disease, harbored IGF1R(+) CTCs (P = 0.007). Patients with early disease and exclusively IGF1R(+) CTCs had longer disease-free (P = 0.02) and overall survival (P = 0.001) compared to patients with both IGF1R(+) and IGF1R(-) CTC populations. 67% of early-stage CTC(+) patients evaluated had exclusively IGF1R(+)/E-cadherin(+) CTCs, 33% also had IGF1R(-)/E-cadherin(-) CTCs, and none had exclusively IGF1R(-)/E-cadherin(-) CTCs compared to 17%, 75%, and 8% of metastatic patients, respectively (P = 0.027). Similarly, in paired samples of patients with early disease that progressed to metastatic disease, the proportion of IGF1R(+)/E-cadherin(+) CTCs was reduced and IGF1R(-)/E-cadherin(-) CTCs were increased in the metastatic stage compared to early disease stage. IGF1R(+) CTCs are commonly detected in breast cancer, and their frequency decreases in the metastatic disease stage. IGF1R(+)/E-cadherin(+) CTCs also decrease in metastatic patients. IGF1R(+) CTCs are associated with favorable outcomes in early disease stage, suggesting that IGF1R expression is correlated with reduced metastatic potential in breast cancer.

Insulin-like Growth Factor 1 Signaling Axis Meets p53 Genome Protection Pathways

Clinical, epidemiological, and experimental evidence indicate that the insulin-like growth factors (IGFs) are important mediators in the biochemical chain of events that lead from a phenotypically normal to a neoplastic cell. The IGF1 receptor (IGF1R), which mediates the biological actions of IGF1 and IGF2, exhibits potent pro-survival and antiapoptotic activities. The IGF1R is highly expressed in most types of cancer and is regarded as a promising therapeutic target in oncology. p53 is a transcription factor with tumor suppressor activity that is usually activated in response to DNA damage and other forms of cellular stress. On the basis of its protective activities, p53 is commonly regarded as the guardian of the genome. We provide evidence that the IGF signaling axis and p53 genome protection pathways are tightly interconnected. Wild-type, but not mutant, p53 suppresses IGF1R gene transcription, leading to abrogation of the IGF signaling network, with ensuing cell cycle arrest. Gain-of-function, or loss-of-function, mutations of p53 in tumor cells may disrupt its inhibitory activity, thus generating oncogenic molecules capable of transactivating the IGF1R gene. The interplay between the IGF1 and p53 pathways is also of major relevance in terms of metabolic regulation, including glucose transport and glycolysis. A better understanding of the complex physical and functional interactions between these important signaling pathways will have major basic and translational relevance.

The impact of IGF-1R expression on the outcomes of patients with breast cancer: a meta-analysis

Purpose

The value of insulin-like growth factor 1 receptor (IGF-1R) for predicting survival of patients with breast cancer remains controversial. The purpose of this study was to perform a meta-analysis of the published data to attempt to clarify the impact of IGF-1R.

Methods

Studies published between January 1, 1990 and October 1, 2014 were identified using an electronic search to aggregate the available survival results. Studies were included if they reported detecting IGF-1R expression in the primary breast cancer and analyzed patient survival data according to IGF-1R status. The principal outcome measures were hazard ratios (HRs) for survival of IGF-1R-positive patients. Combined HRs and 95% confidence intervals (CIs) were estimated using fixed- or random-effects models according to between-study heterogeneity.

Results

Ten studies, involving 5,406 patients, satisfied our inclusion criteria. Data from five studies provided the impact of IGF-1R on overall survival (OS), three studies the impact on breast cancer-specific survival (BCSS), and seven studies the impact on disease-free survival (DFS). The results of meta-analysis showed that for DFS, membranous IGF-1R positivity was not a significant predictor. The combined HR for OS/BCSS was 0.63 (95% CI: 0.42–0.95, P=0.03), indicating that membranous IGF-1R positivity was a significant predictor of better survival. IGF-1R cytoplasmic positivity was significantly associated with longer DFS and OS/BCSS (combined HR: 0.56, 95% CI: 0.35–0.89, P=0.01; combined HR: 0.55, 95% CI: 0.35–0.85, P=0.008, respectively). The results of subgroup analysis suggested that membranous IGF-1R positivity in hormone-receptor-positive breast cancer was correlated with favorable DFS (combined HR: 0.61, 95% CI: 0.41–0.92, P=0.02) and OS/BCSS (combined HR: 0.73, 95% CI: 0.57–0.93, P=0.01). Membranous IGF-1R positivity in triple-negative breast cancer predicted worse DFS (combined HR: 1.86, 95% CI: 1.03–3.34, P=0.04). Membranous IGF-1R positivity in Her-2-positive or ER (estrogen receptor)-negative breast cancer was not found to be a significant prognostic indicator.

Conclusion

The results of this meta-analysis suggest that IGF-1R expression has different prognostic values for patients with breast cancers of different molecular subtypes. It was a favorable prognostic indicator in unselected breast cancers and hormone-receptor-positive cancers, but indicated poor survival in triple-negative breast cancers.

Characterization of effector components from the humoral and cellular immune response stimulated by melanoma cells exhibiting modified IGF-1 expression

Modified melanoma B16 cells inhibited in their IGF-1 expression (B16MOD), on the contrary to the IGF-1 fully expressed parental wild-type (B16WT) counterpart, were shown to stimulate humoral as well as cellular immune responses. Among humoral components, the neutralizing and complement-fixing antibodies of IgM and essentially IgG2 (a+b) isotypes exhibited in vitro and in vivo effects upon tumour growth, while the IgG1 antibody isotype promoted enhanced tumour proliferation. As for the cellular immunity, it was found that the T CD8(+) lymphocyte subpopulation remained the main potent and long lasting immune active effector regulating tumour growth.

IGF-1 and BRCA1 signalling pathways in familial cancer

The insulin-like growth factor (IGF) system has a direct effect on cellular proliferation and survival, and interacts with genetic and environmental factors implicated in causing cancer. Experimental, clinical, and epidemiological evidence show that the IGF signalling pathways are important mediators in the biochemical and molecular chain of events that lead from a phenotypically normal cell to one harbouring neoplastic traits. BRCA1 and BRCA2 have an important role in the development of hereditary and sporadic breast and ovarian cancer. Recent evidence suggests that risk of cancer conferred by BRCA mutations can be modified by genetic and environmental factors, including ambient concentrations of IGF-1 and polymorphisms in IGF system components. This Review addresses interactions between the IGF and BRCA1 signalling pathways, and emphasises the convergence of IGF-1-mediated cell survival, proliferative pathways, and BRCA1-mediated tumour protective pathways. Understanding the complex interactions between these signalling pathways might improve our understanding of basic molecular oncology processes and help to identify new molecular targets, predictive biomarkers, and approaches for optimising cancer therapies.

LOH at 6q and 10q in fractionated circulating DNA of ovarian cancer patients is predictive for tumor cell spread and overall survival

Background

We recently showed that LOH proximal to M6P/IGF2R locus (D6S1581) in primary ovarian tumors is predictive for the presence of disseminated tumor cells (DTC) in the bone marrow (BM). For therapy-monitoring, it would be highly desirable to establish a blood-based biomarker. Therefore, we quantified circulating DNA (cirDNA) in sera of 63 ovarian cancer patients before surgery and after chemotherapy, measured incidence of LOH at four cancer-relevant chromosomal loci, correlated LOH with tumor cell spread to the BM and evaluated prognostic significance of LOH.

Methods

cirDNA was fractionated into high- and low molecular-weight fraction (HMWF, LMWF) for LOH-profiling, utilizing PCR-based fluorescence microsatellite analysis. BM aspirates were analyzed for DTC by immunocytochemistry using the pan-cytokeratin antibody A45-B/B3.

Results

cirDNA levels in the HMWF before surgery were predictive for residual tumor load (p = 0.017). After chemotherapy, we observed a significant decline of cirDNA in the LMWF (p = 0.0001) but not in the HMWF. LOH was prevalently detected in the LMWF with an overall frequency of 67%, only moderately ablating after chemotherapy (45%). Before surgery, LOH in the LMWF at marker D10S1765 and D13S218 significantly correlated with tumor grading and FIGO stage (p = 0.033, p = 0.004, respectively). In both combined fractions, LOH at D6S1581 additionally associated with overall survival (OS) (p = 0.030). Moreover, solely LOH at D10S1765 in LMWF after therapy correlated with DTC in BM after therapy (p = 0.017).

Conclusion

We demonstrate the applicability and necessity of DNA-fractionation prior to analyzing circulating LOH and identify LOH at D10S1765 and D6S1581 as novel blood-based biomarkers for ovarian cancer, being relevant for therapy-monitoring.

Quantitative determination of insulin-like growth factor 1 receptor mRNA in formalin-fixed paraffin-embedded tissues of invasive breast cancer

BACKGROUND

Insulin-like growth factor 1 receptor (IGF1R) has recently received much attention due to its role in initiation and progression of breast cancer. Previously analysis of its gene expression has been restricted to fresh-frozen (FF) samples, but application of this technique to routinely processed formalin-fixed paraffin-embedded (FFPE) samples could facilitate larger retrospective studies correlating IGF1R expression with prognosis and therapeutic response.

METHODS

A series of 77 paired FFPE and FF specimens of breast tumors was used to evaluate the possibility of quantifying IGF1R gene expression with FFPE samples and to compare the results obtained from FFPE and FF samples. The feasibility and prognostic value of analyzing IGF1R gene expression using FFPE samples was evaluated in a cohort of 260 primary breast tumors.

RESULTS

Total RNA was extracted from 95.4% of the FFPE samples with concentration at least 30 ng/μL. Real-time PCR based on Taqman methodology was successful in 90% of the FFPE samples. IGF1R gene expression showed strong correlation not only between FFPE and FF (Spearman ρ = 0.74), but also with IGF1R protein expression in both types of specimen. Kaplan-Meier analysis showed that higher IGF1R mRNA expression was associated with longer recurrence-free survival (P = 0.009) and breast cancer-specific survival (P = 0.0002).

CONCLUSIONS

Quantitative analysis of IGF1R gene expression in FFPE tissues can be feasibly and reliably conducted, and provides information relevant to the characteristics and outcome of invasive breast cancer.

Loss of heterozygosity proximal to the M6P/IGF2R locus is predictive for the presence of disseminated tumor cells in the bone marrow of ovarian cancer patients before and after chemotherapy

Disseminated tumor cells (DTC) in the bone marrow (BM) are present in about 35% of ovarian cancers before surgery and after chemotherapy and are associated with worse prognosis. A molecular biomarker in the primary tumor predicting tumor cell spread would be highly desirable. The purpose of the study was to investigate loss of heterozygosity (LOH) in primary ovarian tumors at four ovarian cancer-relevant chromosomal loci involved in apoptosis, platinum sensitivity, or DNA-repair, to assess the prognostic value of LOH and to correlate LOH with DTC occurrence before surgery and after chemotherapy. Primary tumor DNA of 88 patients was analyzed for LOH at four polymorphic microsatellite markers using PCR-based fluorescence microsatellite analysis. BM aspirates were analyzed for DTC by immunocytochemistry using the pan-cytokeratin antibody A45-B/B3. LOH at the entire marker set correlated with tumor grading (P = 0.0001) and histology (P = 0.004). LOH at marker D10S1765 correlated with FIGO stage (P = 0.046) and grading (P = 0.05), whereas LOH at D17S855 significantly associated with grading (P = 0.023) and histology (P = 0.012), respectively. DTC were detected in 49% of patients before surgery and in 50% of patients after chemotherapy. Interestingly, LOH proximal to D6S1581 significantly correlated with DTC presence before surgery (P = 0.05) and after chemotherapy (P = 0.022). Conclusively, our data suggest that allelic loss at D6S1581 (proximal to M6P/IGF2R locus) serves as a molecular biomarker for the presence of DTC in the BM before and after chemotherapy.

ErbB2 enhances mammary tumorigenesis, oncogene-independent recurrence and metastasis in a model of IGF-IR-mediated mammary tumorigenesis

Background

The type I insulin-like growth factor receptor (IGF-IR) and ErbB2 (Her-2) are receptor tyrosine kinases implicated in human breast cancer. Both proteins are currently the subject of targeted therapeutics that are used in the treatment of breast cancer or which are in clinical trials. The focus of this study was to utilize our inducible model of IGF-IR overexpression to explore the interaction of these two potent oncogenes.

Results

ErbB2 was overexpressed in our RM11A cell line, a murine tumor cell line that overexpresses human IGF-IR in an inducible manner. ErbB2 conferred an accelerated tumor onset and increased tumor incidence after injection of RM11A cells into the mammary glands of syngeneic wild type mice. This was associated with increased proliferation immediately after tumor cell colonization of the mammary gland; however, this effect was lost after tumor establishment. ErbB2 overexpression also impaired the regression of established RM11A tumors following IGF-IR downregulation and enhanced their metastatic potential.

Conclusion

This study has revealed that even in the presence of vast IGF-IR overexpression, a modest increase in ErbB2 can augment tumor establishment in vivo, mediate resistance to IGF-IR downregulation and facilitate metastasis. This supports the growing evidence suggesting a possible advantage of using IGF-IR and ErbB2-directed therapies concurrently in the treatment of breast cancer.

Identification of Insulin-Like Growth Factor-I Receptor (IGF-IR) Gene Promoter-Binding Proteins in Estrogen Receptor (ER)-Positive and ER-Depleted Breast Cancer Cells

The insulin-like growth factor I receptor (IGF-IR) has been implicated in the etiology of breast cancer. Overexpression of the IGF-IR gene is a typical feature of most primary breast cancers, whereas low IGF-IR levels are seen at advanced stages. Hence, evaluation of IGF-IR levels might be important for assessing prognosis. In the present study, we employed a proteomic approach based on DNA affinity chromatography followed either by mass spectroscopy (MS) or Western blot analysis to identify transcription factors that may associate with the IGF-IR promoter in estrogen receptor (ER)-positive and ER-depleted breast cancer cells. A biotinylated IGF-IR promoter fragment was bound to streptavidin magnetic beads and incubated with nuclear extracts of breast cancer cells. IGF-IR promoter-binding proteins were eluted with high salt and analyzed by MS and Western blots. Among the proteins that were found to bind to the IGF-IR promoter we identified zinc finger transcription factors Sp1 and KLF6, ER-α, p53, c-jun, and poly (ADP-ribosylation) polymerase. Furthermore, chromatin immune-precipitation (ChIP) analysis confirmed the direct in vivo binding of some of these transcription factors to IGF-IR promoter DNA. The functional relevance of binding data was assessed by cotransfection experiments with specific expression vectors along with an IGF-IR promoter reporter. In summary, we identified nuclear proteins that are potentially responsible for the differential expression of the IGF-IR gene in ER-positive and ER-depleted breast cancer cells.

Targeting the IGF1 axis in cancer proliferation

The IGF network of ligands, cell-surface receptors and IGF-binding proteins has important roles at multiple levels, including the cellular, organ and organism levels. The IGF system mediates growth, differentiation and developmental processes, and is also involved in various metabolic activities. Dysregulation of IGF system expression and action is linked to diverse pathologies, ranging from growth deficits to cancer development. Targeting of the IGF axis emerged in recent years as a promising therapeutic approach in conditions in which the IGF system is involved. Specific IGF1 receptor (IGF1R) targeting, in particular, produced the best experimental and clinical results so far, and generated significant optimism in the field. This review provides a basic analysis of the role of the IGF1R in cancer biology and explores the functional interactions between the IGF signaling pathways and various cancer genes (e.g., oncogenes, tumor suppressors). In addition, we review a number of specific malignancies in which the IGF system is involved and summarize recent data on preclinical and clinical studies employing IGF1R-targeted modalities.

The insulin-like growth factor-I receptor as an oncogene

The insulin-like growth factor-I receptor (IGF-IR) mediates the biological actions of both IGF-I and IGF-II. The IGF-IR is expressed in most transformed cells, where it displays potent antiapoptotic, cell-survival, and transforming activities. IGF-IR expression is a fundamental prerequisite for the acquisition of a malignant phenotype, as suggested by the finding that IGF-IR-null cells (derived from IGF-IR knock-out embryos) are unable to undergo transformation when exposed to cellular or viral oncogenes. This review article will focus on the underlying molecular mechanisms that are responsible for the normal, physiological control of IGF-IR gene expression, as well as the cellular pathways that underlie its aberrant expression in cancer. Examples from the clinics will be presented, including a description of how the IGF system is involved in breast, prostate, pediatric, and gynecological cancers. Finally, current attempts to target the IGF-IR as a therapeutic approach will be described.

Crosstalk between IGF1R and estrogen receptor signaling in breast cancer

After the discovery that depriving certain breast tumors of estrogen promoted tumor regression, therapeutic strategies aimed at depriving tumors of this hormone were developed. The tumorigenic properties of estrogen are regulated through the estrogen receptor-alpha (ER), making understanding the mechanisms that activate this receptor highly relevant. In addition to estrogen activating the ER, other growth factor pathways, such as the insulin-like growth factors (IGFs), can activate the ER. This review will examine the interaction between these two pathways. Estrogen can activate the growth stimulatory properties of the IGF pathway via ER's genomic and non-genomic functions. Further, blockade of ER function can inhibit IGF-mediated mitogenesis and blocking IGF action can inhibit estrogen stimulation of breast cancer cells. Collectively, these observations suggest that the two growth regulatory pathways are tightly linked and a more thorough understanding of the mechanism of this crosstalk could lead to improved therapeutic strategies in breast cancer.

The aromatase inhibitor letrozole and inhibitors of insulin-like growth factor I receptor synergistically induce apoptosis in in vitro models of estrogen-dependent breast cancer

Introduction

Endocrine-dependent, estrogen receptor positive breast cancer cells proliferate in response to estrogens, synthesized by the cytochrome p450 aromatase enzyme. Letrozole is a potent nonsteroidal aromatase inhibitor that is registered for the treatment of postmenopausal women with advanced metastatic breast cancers and in the neoadjuvant, early, and extended adjuvant indications. Because crosstalk exists between estrogen receptor and insulin-like growth factor I receptor (IGF-IR), the effect of combining a selective IGF-IR inhibitor (NVP-AEW541) with letrozole was assessed in two independent in vitro models of estrogen-dependent breast cancer.

Methods

MCF7 and T47D cells stably expressing aromatase (MCF7/Aro and T47D/Aro) were used as in vitro models of aromatase-driven breast cancer. The role of the IGF-IR pathway in breast cancer cells stimulated only by 17β-estradiol or androstenedione was assessed by proliferation assays. The combination of letrozole and NVP-AEW541 was assessed for synergy in inhibiting cell proliferation using Chou-Talalay derived equations. Finally, combination or single agent effects on proliferation and apoptosis were assessed using proliferation assays, flow cytometry, and immunoblotting.

Results

Both MCF7 and T47D cells, as well as MCF7/Aro and T47D/Aro, exhibited sensitivity to inhibition of 17β-estradiol dependent proliferation by NVP-AEW541. Letrozole combined with NVP-AEW541 synergistically inhibited androstenedione-dependent proliferation in aromatase-expressing cells with combination index values of 0.6 or less. Synergistic combination effects correlated with higher levels of apoptosis as compared with cells treated with the single agent alone. Treatment with either agent also appeared to inhibit IGF-IR signalling via phosphoinositide 3-kinase. Notably, IGF-IR inhibition had limited effect on estrogen-dependent proliferation in the cell lines, but was clearly required for survival, suggesting that the combination of letrozole and IGF-IR inhibition sensitizes cells to apoptosis.

Conclusion

Inhibition of the IGF-IR pathway and aromatase was synergistic in two independent estrogen-dependent in vitro models of breast cancer. Moreover, synergism of NVP-AEW541 and letrozole correlated with induction of apoptosis, but not cell cycle arrest, in the cell lines tested. Combination of IGF-IR inhibitors and letrozole may hold promise for the treatment of patients with estrogen-dependent breast cancers.

Insulin-like growth factor system gene expression in cervical scrapes from women with squamous intraepithelial lesions and cervical cancer

BACKGROUND

There is ample evidence that the insulin-like growth factors (IGF) system is involved in the development of several types of cancer. The aim of this study was to evaluate the expression levels of IGF-I, IGF-II, IGF binding protein 3 (IGFBP-3) and IGF-I receptor (IGF-IR) in exfoliated cervical cells in cervical carcinogenesis.

METHODS

mRNA levels of IGF-I, IGF-II, IGFBP-3 and IGF-IR were assessed by real-time PCR in 105 cervical scrapes obtained from 16 patients diagnosed with low-grade squamous intraepithelial lesions (LSIL), 24 with high-grade SIL (HSIL), 23 with cervical cancer, and 42 from controls with normal Papanicolau (Pap) test.

RESULTS

IGF-I mRNA levels were very low and no significant differences were seen between control and other groups. IGF-II mRNA levels were significantly lower in LSIL than in control group (median [arbitrary units]: 0.38 vs. 2.42, P=0.006) but its expression in HSIL and cervical cancer was similar to the one observed in controls. IGFBP-3 mRNA levels were significantly lower in cancer than in controls (median [arbitrary units]: 0.43 vs. 0.73, P=0.03). We observed a decrease in IGF-IR gene expression as the SIL degree increased (median for controls, LSIL, HSIL, and cervical carcinoma [arbitrary units]: 31.24, 9.08, 8.95, and 3.56, respectively). IGF-IR mRNA levels were significantly lower in HSIL and cervical cancer in comparison with controls (P=0.043 and P<0.001, respectively).

CONCLUSIONS

The present observations suggest that a reduced expression of IGFBP-3 and IGF-IR can be associated with progression to cervical cancer; the specific role played by the IGF-IR in this process remains unclear.

Elevated insulin-like growth factor-I receptor (IGF-IR) levels in primary breast tumors associated with BRCA1 mutations

The insulin-like growth factors (IGFs) play a pivotal role in breast cancer. Inherited predisposition to breast and ovarian cancer is associated with germline BRCA1/BRCA2 mutations. To evaluate the impact of BRCA1 mutations on IGF-IR gene expression, we performed an immunohistochemical analysis of IGF-IR in primary breast tumors from BRCA1 mutation carriers and non-carriers. Results obtained revealed a significant elevation in IGF-IR levels in tumors from BRCA1 mutation carriers compared with non-carriers. To assess the potential inhibitory role of BRCA1 on IGF-IR levels, we infected the BRCA1-deficient HCC1937 cell line with a BRCA1-encoding adenoviral vector. Results of Western blots showed that BRCA1 induced a large reduction in endogenous IGF-IR levels. Furthermore, results of chromatin immunoprecipitation assays indicated that the mechanism of action of BRCA1 involves interaction with Sp1, a potent transactivator of the IGF-IR gene. In conclusion, our data suggests that the IGF-IR gene is a physiologically relevant downstream target for BRCA1 action.

Stimulation of anti-melanoma immune effectors via modified tumour cells exhibiting inhibited IGF-I and low CD9

Modified melanoma cells (B16-F0.MOD) characterized by inhibited IGF-I, CD9 low but not their wild-type counterparts (B16-F0.WT), IGF-I positive, CD9 high, were shown to be immunogenic for syngeneic hosts. C57BL/6 syngeneic recipients vaccinated with B16-F0.MOD cells developed immune effectors that were observed at the humoral as well as cellular levels. These immune effectors were shown to be capable of controlling in vitro tumour growth and in vivo tumour progression.

Modulated expression of cell surface molecules and in vivo outgrowth of modified melanoma cells

Modulation of cell surface molecules involved in immune recognition and cellular interactions (class I major histocompatibility complex or MHC-I, B7.1 or CD80, integrin alpha4 or CD49d, tetraspanins CD9, CD81) was examined in modified B16 melanoma cells displaying either inhibited IGF-I expression or transfected OVA encoding gene. It was shown that inhibiting IGF-I expression or inserting OVA encoding gene did not lead to modification relevant to the presence of MHC-I or B7.1. However downregulation of tetraspanin CD9 was observed in modified IGF-I but not in OVA encoding gene inserted melanoma cells. Expression of tetraspanin CD81 and integrin alpha4/CD49d remained unchanged. Inoculated into syngeneic recipients, the modified melanoma cells exhibited significant delayed outgrowth with a reduction in the percentage of lethal tumors observed essentially in hosts injected with inhibited IGF-I expression cells.

Expression of nuclear insulin receptor substrate 1 in breast cancer

BACKGROUND

Insulin receptor substrate 1 (IRS-1), a cytoplasmic protein transmitting signals from the insulin and insulin-like growth factor 1 receptors, has been implicated in breast cancer. Previously, it was reported that IRS-1 can be translocated to the nucleus and modulate oestrogen receptor alpha (ERalpha) activity in vitro. However, the expression of nuclear IRS-1 in breast cancer biopsy specimens has never been examined.

AIMS

To assess whether nuclear IRS-1 is present in breast cancer and non-cancer mammary epithelium, and whether it correlates with other markers, especially ERalpha. Parallel studies were carried out for the expression of cytoplasmatic IRS-1.

METHODS

IRS-1 and ERalpha expression was assessed by immunohistochemical analysis. Data were evaluated using Pearson's correlation, linear regression and receiver operating characteristic analysis.

RESULTS

Median nuclear IRS-1 expression was found to be low in normal mammary epithelial cells (1.6%) and high in benign tumours (20.5%), ductal grade 2 carcinoma (11.0%) and lobular carcinoma (approximately 30%). Median ERalpha expression in normal epithelium, benign tumours, ductal cancer grade 2 and 3, and lobular cancer grade 2 and 3 were 10.5, 20.5, 65.0, 0.0, 80 and 15%, respectively. Nuclear IRS-1 and ERalpha positively correlated in ductal cancer (p<0.001) and benign tumours (p<0.01), but were not associated in lobular cancer and normal mammary epithelium. In ductal carcinoma, both nuclear IRS-1 and ERalpha negatively correlated with tumour grade, size, mitotic index and lymph node involvement. Cytoplasmic IRS-1 was expressed in all specimens and positively correlated with ERalpha in ductal cancer.

CONCLUSIONS

A positive association between nuclear IRS-1 and ERalpha is a characteristic for ductal breast cancer and marks a more differentiated, non-metastatic phenotype.

The insulin-like growth factor-I receptor gene: a downstream target for oncogene and tumor suppressor action

The insulin-like growth factor-I receptor (IGF-IR) mediates the biological actions of both IGF-I and IGF-II. The IGF-IR is expressed in most transformed cells, where it displays potent antiapoptotic and cell-survival activities. IGF-IR levels are tightly regulated by the concerted action of secreted (e.g. peptide and steroid hormones, growth factors and cytokines) and cellular (e.g. transcription factors, oncogenes and tumor suppressors) factors. The mode of action of many tumor suppressors involves transcriptional suppression of the IGF-IR gene, with a subsequent reduction in cell-surface IGF-IR concentrations and IGF-I action. Loss-of-function mutation of tumor suppressors, a common theme in human cancer, can lead to aberrant regulation of IGF-IR gene expression.

Promoter-specific transcription of insulin-like growth factor-II in epithelial ovarian cancer

OBJECTIVES

The IGF-II gene has four promoters (P1-P4); each initiates promoter-specific transcription. Studies have shown that IGF-II promoters normally active during fetal growth, but silent in postnatal life, are reactivated in cancer. In a previous study, we found IGF-II transcription evaluated at a common translated region was associated with ovarian cancer progression. This study was conducted to further determine which IGF-II promoters were responsible for the association.

METHODS

Promoter-specific transcription at each IGF-II promoter was analyzed in 201 ovarian tumor samples using quantitative RT-PCR. Cox regression analysis was performed to determine the association of IGF-II promoter-specific expression with patient survival.

RESULTS

P3 and P4 transcripts were detected more frequently and at significantly higher levels than the transcripts of P1 and P2. P3 and P4 transcripts were strongly correlated with the common IGF-II translated region and were significantly higher in patients with late stage disease, large residual tumor, suboptimal debulking or serous histology compared to those with early stage, small residual tumor, optimal debulking or non-serous histology. Survival analysis showed that patients with high P3 or P4 expression had a 2-fold increase in risk for death compared to those with low P3 or P4. These associations remained significant after adjustment for patient age at surgery, disease stage, tumor grade and histology. P1 and P2 transcripts, however, were not associated with disease characteristics or survival.

CONCLUSIONS

These findings suggest that IGF-II transcription from P3 and P4 promoters is important in ovarian cancer and evaluation of IGF-II promoter-specific transcription may have clinical implications in ovarian cancer prognosis and treatment.

Transcriptional regulation of the insulin-like growth factor-I receptor gene in breast cancer

The insulin-like growth factor-I receptor (IGF-IR) has an important role in normal mammary gland growth and morphogenesis. In addition, the IGF-IR has been implicated in the initiation and progression of breast cancer. Previous studies have indicated that acquisition of the malignant phenotype in breast cancer is initially IGF-IR dependent. Most breast cancer-derived cell lines and primary tumors express high levels of IGF-IR mRNA and protein, whereas metastatic stages are usually associated with a decrease in IGF-IR levels. Transcription of the IGF-IR gene is controlled by complex interactions involving DNA-binding and non DNA-binding transcription factors. This review highlights selected examples of tumor suppressors, including BRCA1, p53, and WT1, whose mechanism of action involves regulation of IGF-IR gene expression.

An association between a common variant (G972R) in the IRS-1 gene and sex hormone levels in post-menopausal breast cancer survivors

Insulin receptor substrate-1 (IRS-1) is a key downstream signaling molecule common to both the insulin and IGF signaling pathways that can interact with the estrogen pathway to regulate breast cell growth. We investigated whether a putative functional variant for IRS-1 (G972R) influences circulating levels of sex hormones, sex hormone binding globulin (SHBG), C-peptide, and insulin-like growth factor 1 (IGF-1) levels among post-menopausal African-American and non-Hispanic white breast cancer patients enrolled in the Health, Eating, Activity, and Lifestyle (HEAL) Study. Circulating levels of sex hormones and growth factors can influence breast cancer recurrence and survival. Serum estrone, estradiol, testosterone, SHBG, IGF-1 and C-peptide were measured in 468 patients at 30+ months post diagnosis. Non-protein bound hormone levels (free estradiol, free testosterone) were calculated. In African-American patients, the IRS-1 variant was associated with increased serum levels of estrone (p = 0.02), free estradiol (p = 0.04), total testosterone (p = 0.04), free testosterone (p = 0.006) and decreased levels of sex hormone-binding globulin (p = 0.02). No association was present for white patients. Our findings provide suggestive evidence that IRS-1 G972R variant may be associated with circulating levels of sex hormones and SHBG in African American breast cancer survivors.

Expression of IGF-I, IGF-II, and IGF-IR in gallbladder carcinoma. A systematic analysis including primary and corresponding metastatic tumours

AIMS

The insulin-like growth factor (IGF) system has been implicated in tumour development and progression. This study was designed to analyse the expression of the IGF-I receptor (IGF-IR) and its ligands (IGF-I, IGF-II) in gallbladder cancer.

METHODS

IGF-I, IGF-II, and IGF-IR immunoreactivity was investigated in 57 gallbladder carcinomas and corresponding lymph node (n = 11) and hepatic (n = 7) metastases using a tissue microarray technique and correlated with tumour stage, grade, and patient outcome.

RESULTS

Cancer tissue allowing a reliable evaluation of IGF-I, IGF-II, and IGF-IR was present in 55 of 57 primary tumours and 17 of 18 metastases. IGF-I and IGF-II immunoreactivity was seen in 25 and 14 of the 55 primary tumours, in addition to six and three of the 17 metastases, respectively. No associations with tumour stage, grade, or prognosis were detected. IGF-IR was expressed in 52 of 55 primary tumours and all 17 metastases. IGF-IR staining intensity decreased with tumour cell dedifferentiation. Moreover, IGF-IR expression in less than 50% of cancer cells was an independent marker of poor prognosis in multivariate analysis (risk ratio, 4.0; 95% confidence interval, 1.4 to 11.2; p = 0.01).

CONCLUSIONS

The expression of IGF-IR and its ligands provides evidence for the existence of an auto/paracrine loop of tumour cell stimulation in gallbladder cancer and makes this type of cancer a candidate for therapeutic strategies aimed at interfering with the IGF pathway. The recognition of IGF-IR as a new independent prognostic biomarker may help to identify patients who might benefit from adjuvant treatment.

Inhibition of CCN6 (WISP3) expression promotes neoplastic progression and enhances the effects of insulin-like growth factor-1 on breast epithelial cells

INTRODUCTION

CCN6/WISP3 belongs to the CCN (Cyr61, CTGF, Nov) family of genes that contains a conserved insulin-like growth factor (IGF) binding protein motif. CCN6 is a secreted protein lost in 80% of the aggressive inflammatory breast cancers, and can decrease mammary tumor growth in vitro and in vivo. We hypothesized that inhibition of CCN6 might result in the loss of a growth regulatory function that protects mammary epithelial cells from the tumorigenic effects of growth factors, particularly IGF-1.

METHOD

We treated human mammary epithelial (HME) cells with a CCN6 hairpin short interfering RNA.

RESULTS

CCN6-deficient cells showed increased motility and invasiveness, and developed features of epithelial-mesenchymal transition (EMT). Inhibition of CCN6 expression promoted anchorage-independent growth of HME cells and rendered them more responsive to the growth effects of IGF-1, which was coupled with the increased phosphorylation of IGF-1 receptor and insulin receptor substrate-1 (IRS-1).

CONCLUSION

Specific stable inhibition of CCN6 expression in HME cells induces EMT, promotes anchorage-independent growth, motility and invasiveness, and sensitizes mammary epithelial cells to the growth effects of IGF-1.

High insulin-like growth factor-2 (IGF-2) gene expression is an independent predictor of poor survival for patients with advanced stage serous epithelial ovarian cancer

OBJECTIVE

Epithelial ovarian cancer is the deadliest gynecologic malignancy, yet its molecular etiology remains poorly understood. Evidence is accumulating to support a role for the insulin-like growth factor family in human carcinogenesis, and recently using microarray expression analysis, we demonstrated over-expression of the insulin-like growth factor-2 (IGF-2) gene in advanced stage epithelial ovarian cancers. The purpose of the current study is to further elucidate the role of the IGF-2 gene in ovarian cancer development and progression.

METHODS

Relative expression of IGF-2 was measured in 109 epithelial ovarian cancers and eight normal ovarian surface epithelial (NOSE) samples, using quantitative real-time polymerase chain reaction. Associations with clinicopathological parameters were examined.

RESULTS

Expression of the IGF-2 gene was more than 300-fold higher in ovarian cancers compared with normal ovarian surface epithelium samples (P <0.001). High IGF-2 expression was associated with advanced stage disease at diagnosis (P <0.001), high-grade cancers (P <0.05) and sub-optimal surgical cytoreduction (P = 0.08). In multivariate analysis, relative IGF-2 expression was an independent predictor of poor survival.

CONCLUSIONS

Expression of the IGF-2 gene is significantly higher in ovarian cancers relative to normal ovarian surface epithelium. Further, high IGF-2 gene expression is associated with high grade, advanced stage disease, and is an independent predictor of poor survival in patients with epithelial ovarian cancer. As such, IGF-2 is a molecular marker and potential therapeutic target for the most aggressive epithelial ovarian cancers.

Low Levels of Insulin-Like Growth Factor Type 1 Receptor Expression at Cancer Cell Membrane Predict Liver Metastasis in Dukes’ C Human Colorectal Cancers

PURPOSE

The aim of this study was to evaluate the prognostic significance of insulin-like growth factor type 1 receptor (IGF-1R) expression in Dukes' C human colorectal cancers (CRCs).

EXPERIMENTAL DESIGN

Immunohistochemical staining for IGF-1R was done on formalin-fixed, paraffin-embedded specimens from 161 patients with curatively resected Dukes' C CRC and at least 5-year follow-up periods. We investigated the association between the levels of IGF-1R expression and the clinicopathologic parameters. To evaluate the accurate prognostic value of IGF-1R expression, we investigated two patterns of recurrence-free survival (RFS) according to the mode of recurrence, the hepatic-RFS (H-RFS), and the nonhepatic-RFS (nH-RFS). The influence of the pattern of IGF-1R immunostaining (membranous or cytoplasmic) on RFS was also estimated.

RESULTS

High (diffuse staining) and low (focal staining) levels of IGF-1R expression were found in 45 (28%) and 116 (72%) specimens, respectively. The recurrence rate was significantly higher in the latter group (49 of 116) than the former group (9 of 45; P = 0.01). H-RFS was significantly longer for the former group than the latter group (P = 0.021), whereas no difference was found in nH-RFS between the two groups (P = 0.121). In multivariate analysis, the level of IGF-1R expression was an independent factor for H-RFS (P = 0.015) as were the depth of invasion and lymph vessel invasion (P = 0.006 and 0.022, respectively). Using a combination of the level of IGF-1R expression and these two factors, the prognostic value was further increased. When IGF-1R staining patterns (membranous or cytoplasmic) were compared, membrane staining of IGF-1R possessed prognostic significance.

CONCLUSIONS

In Dukes' C CRC, focal membrane expression of IGF-1R in the primary tumor can predict a high risk of recurrence, especially liver metastasis. Understanding the mechanisms involved could lead to new therapeutic approaches for advanced CRC.

New targets for therapy in breast cancer: mammalian target of rapamycin (mTOR) antagonists

Mammalian target of rapamycin (mTOR) is a serine-threonine kinase member of the cellular phosphatidylinositol 3-kinase (PI3K) pathway, which is involved in multiple biologic functions such as transcriptional and translational control. mTOR is a downstream mediator in the PI3K/Akt signaling pathway and plays a critical role in cell survival. In breast cancer this pathway can be activated by membrane receptors, including the HER (or ErbB) family of growth factor receptors, the insulin-like growth factor receptor, and the estrogen receptor. There is evidence suggesting that Akt promotes breast cancer cell survival and resistance to chemotherapy, trastuzumab, and tamoxifen. Rapamycin is a specific mTOR antagonist that targets this pathway and blocks the downstream signaling elements, resulting in cell cycle arrest in the G₁ phase. Targeting the Akt/PI3K pathway with mTOR antagonists may increase the therapeutic efficacy of breast cancer therapy.

Identification of genetic alterations related to chemoresistance in epithelial ovarian cancer

OBJECTIVE

After the completion of primary chemotherapy, the majority of advanced ovarian cancer patients have persistent, chemoresistant disease. Comparative genomic hybridization (CGH) has been used to study genetic alterations that may be responsible for chemoresistance in ovarian cancer. CGH is a useful, genomewide screen but resolution is limited to 5-10 Mb. Recently, quantitative microsatellite analysis (QuMA), a TaqMan-based quantitative PCR technology, has been used for higher resolution of DNA copy number abnormalities. Our goal is to identify specific chromosomal aberrations correlated with platinum resistance.

METHODS

Snap-frozen ovarian tissue samples taken from 22 patients with ovarian cancer between 1994 and 1998 were analyzed. Patients whose ovarian cancer actually demonstrated growth during platinum-combination treatment or no objective evidence of regression following four to six cycles of therapy were considered to have clinically defined platinum-resistant disease. QuMA was carried out at the following loci using the ABI Prism 7700 (TaqMan) instrument with a microsatellite repeat probe: D3S1553, D3S1617, D5S464, D5S630, D6S1581, D6S446, D8S557, D19S208, D20S196, DXS1068. Fisher's exact test, exact logistic regression, and the Cochran-Armitage trend test were used. Because of multiple hypothesis testing, the P values were adjusted with the Bonferroni procedure to limit the familywise error rate to at most 5%.

RESULTS

Of the 22 patients, 12 (54.5%) were platinum-sensitive and 10 (45.5%) were platinum-resistant. When comparing sensitive and resistant patients, no statistically significant difference was noted among stage, grade, histology, and age (P = 0.1292, P = 1.0000, P = 1.0000, P = 1.0000, respectively). In the QuMA analysis, 10 of the 14 (71.4%) patients who had a low copy number of D6S1581 were platinum-resistant, while none of the patients with a normal or high copy number of D6S1581 were platinum-resistant. This was statistically significant when the marker data were treated as either a continuous or a categorical variable (P = 0.0410 and P = 0.0170, respectively). No other loci correlated significantly with platinum resistance.

CONCLUSIONS

D6S1581 was the only genetic marker, of those examined, significantly related to chemoresistance. Patients with a loss of D6S1581 are more likely to be platinum-resistant. Identification of genetic alterations associated with platinum resistance detected by QuMA may contribute to a better understanding of clinical behavior and chemotherapy treatment options for patients.

Mammalian target of rapamycin: a new molecular target for breast cancer

The mammalian target of rapamycin (mTOR), a downstream effector of the phosphatidylinositol 3-kinase (PI3K)/Akt (protein kinase B) signaling pathway that mediates cell survival and proliferation, is a prime strategic target for anticancer therapeutic development. By targeting mTOR, the immunosuppressant and antiproliferative agent rapamycin inhibits signals required for cell cycle progression, cell growth, and proliferation. Both rapamycin and novel rapamycin analogues with more favorable pharmaceutical properties, such as CCI-779, RAD 001, and AP23573, are highly specific inhibitors of mTOR. In essence, these agents gain function by binding to the immunophilin FK506 binding protein 12 and the resultant complex inhibits the activity of mTOR. Because mTOR activates both the 40S ribosomal protein S6 kinase (p70s6k) and the eukaryotic initiation factor 4E-binding protein-1, rapamycin-like compounds block the actions of these downstream signaling elements, which results in cell cycle arrest in the G1 phase. Rapamycin and its analogues also prevent cyclin-dependent kinase (CDK) activation, inhibit retinoblastoma protein phosphorylation, and accelerate the turnover of cyclin D1, leading to a deficiency of active CDK4/cyclin D1 complexes, all of which potentially contribute to the prominent inhibitory effects of rapamycin at the G1/S boundary of the cell cycle. Rapamycin and rapamycin analogues have demonstrated impressive growth-inhibitory effects against a broad range of human cancers, including breast cancer, in preclinical and early clinical evaluations. In breast cancer cells, PI3K/Akt and mTOR pathways seem to be critical for the proliferative responses mediated by the epidermal growth factor receptor, the insulin growth factor receptor, and the estrogen receptor. Furthermore, these pathways may be constitutively activated in cancers with many types of aberrations, including those with loss of PTEN suppressor gene function. Therefore, the development of inhibitors of mTOR and related pathways is a rational therapeutic strategy for breast and other malignancies that possess a wide range of aberrant molecular constituents. This review will summarize the principal mechanisms of action of rapamycin and rapamycin derivatives, as well as the potential utility of these agents as anticancer therapeutic agents with an emphasis on breast cancer. The preliminary results of early clinical evaluations with rapamycin analogues and the unique developmental challenges that lie ahead will also be discussed.

Insulin-like growth factor-I inhibits progesterone receptor expression in breast cancer cells via the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin pathway: progesterone receptor as a potential indicator of growth factor activity in breast cancer

Although interactions between estrogen and growth factor signaling pathways have been studied extensively, how growth factors and progesterone regulate each other is less clear. In this study, we found that IGF-I sharply lowers progesterone receptor (PR) mRNA and protein levels in breast cancer cells. Other growth factors, such as epidermal growth factor, also showed the same effect. The decrease of PR levels was associated with reduced PR activity. Unlike progestins, IGF-I does not utilize the proteasome for down-regulating PR. Instead, the IGF-I-mediated decrease in PR levels is via an inhibition of PR gene transcription. In addition, the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway was found to be specifically involved in this IGF-I effect. Our data also suggest that the IGF-I down-regulation of PR is not mediated via a reduction of estrogen receptor (ER) levels or activity. First, IGF-I induced ligand-independent ER activity while reducing ER-dependent PR levels. Second, whereas PR and cyclin D1 are both ER up-regulated, IGF-I increased cyclin D1 levels while decreasing PR levels. Third, constitutively active PI3K or Akt induced ER activity but reduced PR levels and activity. Taken together, our data indicate that IGF-I inhibits PR expression in breast cancer cells via the PI3K/Akt/mTOR pathway. Because low or absent PR in primary breast cancer is associated with poor prognosis and response to hormone therapy, our results suggest that low PR status may serve as an indicator of activated growth factor signaling in breast tumor cells, and therefore of an aggressive tumor phenotype and resistance against hormonal therapy.

Overexpression of insulin-like growth factor II (IGFII) in ZR-75-1 human breast cancer cells: higher threshold levels of receptor (IGFIR) are required for a proliferative response than for effects on specific gene expression

Previous transfection experiments using a zinc-inducible expression vector have shown that overexpression of insulin-like growth factor II (IGFII) in MCF7 human breast cancer cells can reduce dependence on oestrogen for cell growth in vitro (DALY RJ, HARRIS WH, WANG DY, DARBRE PD. (1991) Cell Growth Differentiation 2, 457-464.). Parallel transfections now performed into another oestrogen-dependent human breast cancer cell line (ZR-75-1) yielded three clones of transfected ZR-75-1 cells that produced levels of zinc-inducible IGFII mRNA and secreted mature IGFII protein similar to those found in the transfected MCF7 cells. However, unlike in MCF7 cells, no resulting effects were found on cell growth in the ZR-75-1 clones, even though the ZR-75-1 clones possessed receptors capable of binding 125I-IGFI and showed a growth response to exogenously added IGFII. Medium conditioned by the ZR-75-1 clones could stimulate growth of untransfected MCF7 cells, indicating that the secreted IGFII protein was bioactive. Furthermore, zinc-induced IGFII was capable of increasing both pS2 mRNA levels and CAT activity from a transiently transfected AP1-CAT gene in the ZR-75-1 clones. Constitutive co-overexpression of the protein processing enzyme PC2 resulted in reduced levels of large forms of zinc-inducible IGFII, but zinc treatment still produced no effect on cell growth rate. Finally, however, constitutive co-overexpression of the type I IGF receptor (IGFIR) did result in zinc-inducible increased basal cell growth and reduced dependence on oestrogen for cell growth. These results demonstrate that while overexpression of IGFII per se was sufficient to deregulate MCF7 cell growth, the ZR-75-1 cells are limited in their proliferative response by their intrinsic receptor levels. However, although the proliferative response was limited, molecular responses (expression of pS2 and AP1-CAT) were not limited, indicating that different cellular responses can have different threshold receptor level requirements.

Insulin-like growth factor I triggers nuclear accumulation of cyclin D1 in MCF-7S breast cancer cells

Stimulation of the breast cancer-derived MCF-7S cell line with insulin-like growth factor I (IGF-I; 20 ng/ml) leads to enhanced expression of cyclin D1, hyperphosphorylation of pRb, DNA synthesis, and cell division. 17beta-Estradiol (E(2); 10(-9) m) is not able to stimulate proliferation of MCF-7S cells, although addition of E(2) to serum-starved cells does result in induction of cyclin D1. However, in combination with submitogenic amounts of IGF-I (2 ng/ml), E(2) induces cell proliferation. We have previously shown that the synergistic action of E(2) and IGF-I emanates from the ability of both hormones to induce cyclin D1 expression and that IGF-I action is required to induce activity of the cyclin D1-CDK4 complex, which triggers cell cycle progression. Here, we show that IGF-I (but not E(2)) is able to induce nuclear accumulation of cyclin D1 by a phosphatidylinositol 3-kinase-dependent mechanism. Nuclear accumulation of cyclin D1 and cell cycle progression were also observed when LiCl, a known inhibitor of GSK3beta, was added to E(2)-stimulated cells. Thus, inhibition of GSK3beta activity appears to trigger nuclear accumulation of cyclin D1 and cell cycle progression. This notion was confirmed by overexpression of constitutively active GSK3beta, which blocks IGF-I-induced nuclear accumulation of cyclin D1 as well as S phase transition.

Functional role of alpha-actinin, PI 3-kinase and MEK1/2 in insulin-like growth factor I receptor kinase regulated motility of human breast carcinoma cells

Within epithelial tissue, cells are held together by specialized lateral junctions. At particular stages of development and in pathological processes such as metastasis, cells break down the intercellular junctions, separate from the epithelial sheet and migrate individually. Despite the importance of these processes, little is understood about the regulatory mechanisms of active cell separation. In view of the effects of insulin-like growth factor I (IGF-I) on mammary gland development and cancer, we developed a model using MCF-7 human breast cancer cells in which the process of cell separation can be induced by IGF-I. The separation was enhanced in MCF-7 cells overexpressing the IGF-IR and blocked in the cells expressing a dead-kinase mutant of this receptor. Activation of the IGF-IR resulted in a rapid formation of motile actin microspikes at the regions of cell-cell contacts, disorganization of mature adherens junctions and the onset of cell migration. In cell separation, the signaling between the IGF-IR kinase and actin required phosphatidylinositol 3 (PI 3)-kinase-generated phospholipids but not MAP kinases and was mediated by alpha-actinin. The activity of MEK1/2 kinases was needed for consecutive cell migration. This work also defined a new function for alpha-actinin. Upon IGF-IR activation, green fluorescence protein (GFP)-labeled alpha-actinin concentrated at the base of actin microspikes. Deletion of the N-terminal actin-binding domain of alpha-actinin prevented this redistribution, indicating that this domain is necessary. Detection of the C-terminal tail of alpha-actinin reduced the number of microspikes, showing that alpha-actinin has a role in the development of microspikes and is not passively reorganized with filamentous actin. We suggest that the signaling pathway from the IGF-IR kinase through the PI-3 kinase to alpha-actinin participates in the rapid organization of actin into microspikes at the cell-cell junctions and leads to active cell separation, whereas signaling through ERK1/2 MAP kinases controls cell migration following cell separation.

Synergistic proliferative action of insulin-like growth factor I and 17 beta-estradiol in MCF-7S breast tumor cells

We have analyzed the mechanism by which the combination of insulin-like growth factor I (IGF-I) and 17 beta-estradiol (E2) induces cell cycle progression in MCF-7S cells. This cell line differs from many other breast cancer-derived cell lines in that E2 (1 nM) does not induce cell cycle progression, whereas the combination of submitogenic concentrations of IGF-I (2 ng/ml) and E2 does. We find that addition of IGF-I to MCF-7S cells leads to a dose-dependent activation of the IGF type I receptor and of the MAP kinase and PI3-kinase signaling pathways. No synergy of IGF-I and E2 was detected in the activation of these signaling cascades. In terms of cell cycle-related molecules, we find that IGF-I dose-dependently raises cyclin D1 levels in serum-starved cells. Subsequent activation of cyclin E/CDK2, hyperphosphorylation of pRb, and DNA synthesis are only induced by mitogenic concentrations of IGF-I (> or =20 ng/ml). Treatment of the cells with E2 also results in the induction of cyclin D1, but in the absence of IGF-I the cells remain arrested in G1 phase. We conclude that in MCF-7S cells, the synergistic action of E2 and IGF-I derives from the ability of both hormones to induce cyclin D1 expression. The action of IGF-I is required in these cells to induce activity of the cyclin D1/CDK4 complex, which triggers progression through the cell cycle.

Are the insulin-like growth factors relevant to cancer?

Recognition of molecular pathways relevant to cancer biology have led to advances in prevention and treatment. Numerous laboratory and clinical investigations have implicated the insulin-like growth factors (IGFs) in tumourigenesis. In this review, the evidence for the involvement of IGFs in cancer is discussed. While these data are persuasive, it is clear that additional methods to regulate IGF action in cancer patients are needed to substantiate the role of this growth factor family in cancer biology.

IGFBP-3 in epithelial ovarian carcinoma and its association with clinico-pathological features and patient survival

Insulin-like growth factor binding protein-3 (IGFBP-3) regulates the mitogenic and anti-apoptotic actions of insulin-like growth factors (IGFs). To study the role of IGFBP-3 in ovarian cancer progression, we measured IGFBP-3 concentrations in tumour tissues from 147 patients with epithelial ovarian carcinoma and examined its associations with clinicopathological features of disease and patient survival. The average age of the patients was 54.6 years (range 25-88 years) and the median follow-up time was 37 months. IGFBP-3 levels were measured with a commercial immunoassay kit. Low IGFBP-3 levels were significantly associated with unfavourable prognostic features of the disease, including advanced stage (P=0.048), large size of residual tumour (P=0.007), and suboptimal debulking outcome (P=0.007). Low IGFBP-3 levels were also associated with a significantly increased risk for disease progression (RR=1.92; 95% confidence interval (CI) 1.05-3.45; P=0.034), but the association was not sustained when other clinical and pathological variables were adjusted for in the analysis. No significant associations were observed between the IGFBP-3 level and patients' overall survival and response to chemotherapy. Findings of the study indicate that IGFBP-3 may play a role in the progression of epithelial ovarian cancer, but that it has no independent value in predicting either disease prognosis or the response of patients to chemotherapy.

Energy balance and cancer: the role of insulin and insulin-like growth factor-I

Recent theories propose that a Western lifestyle may increase cancer risk through alterations in the metabolism of insulin and insulin-like growth factors (IGF: McKeown-Eyssen, 1994; Giovannucci, 1995; Kaaks, 19%; Werner & LeRoith, 1996). Insulin regulates energy metabolism, and increases the bioactivity of IGF-I, by enhancing its synthesis. and by decreasing several of its binding proteins (IGFBP; IGFBP-1 and -2). Insulin and IGF-I both stimulate anabolic processes as a function of available energy and elementary substrates (e.g. amino acids). The anabolic signals by insulin or IGF-I can promote tumour development by inhibiting apoptosis, and by stimulating cell proliferation. Furthermore, both insulin and IGF-I stimulate the synthesis of sex steroids, and inhibit the synthesis of sex hormone-binding globulin (SFIBG), a binding protein that regulates the bioavailability of circulating sex steroids to tissues. The present paper reviews epidemiological findings relating the risk of cancers of the colo-rectum, pancreas, breast, endometrium and prostate to body size (obesity, height) and physical activity, and discusses the relationships between obesity and physical activity and plasma levels of insulin, IGF-I and IGFBP. Subsequent sections review epidemiological findings relating cancer risk to indices of chronic hyperinsulinaemia, and to plasma levels of IGF-I and IGFBP. Conclusions are that chronic hyperinsulinaemia may be a cause of cancers of the colon, pancreas and endometrium, and also possibly of the breast. On the other hand, elevated plasma IGF-I, as total concentrations or relative to levels of IGFBP-3, appears to be related to an increased risk of prostate cancer, breast cancer in young women, and possibly cob-rectal cancer. For cancers of the endometrium, breast and prostate, these findings are discussed in the context of relationships between insulin and IGF-I and levels of bioavailable sex steroids.

Down-regulation of insulin-like growth factor-I receptor and insulin receptor substrate-1 expression in advanced human breast cancer

The ligands, receptors and related signaling proteins of the insulin-like growth factor family are involved in the regulation of breast-cancer cell growth. We investigated the expression pattern of insulin-like growth factor-I receptor (IGF-IR), insulin receptor (IR) and insulin receptor substrate-1 (IRS-1), a core downstream signaling protein, in 69 primary breast-cancer specimens of different grades and in 21 control tissues by immunohistochemistry. In addition, cell proliferation (percentage of Ki67(+) nuclei) and estrogen receptor (ER) expression were determined. IGF-IR, IRS-1 and IR were expressed mainly in epithelial cells. IRS-1 and IGF-IR were expressed at high levels in control tissues and in well and moderately differentiated carcinomas but at low levels in poorly differentiated breast cancers. IR expression did not show a significant correlation with the differentiation grade of the tissues investigated. Statistical analysis (ROC analysis for tumor grade) demonstrated that down-regulation of IGF-IR and IRS-1 correlated better with tumor progression than reduction of ER expression or increase in cell proliferation, IGF-IR showing the best correlation, followed by IRS-1 and, less significant, ER and Ki67. Our findings clearly show that progression of breast cancer is accompanied by a reduction of IGF-IR/IRS-1 expression and that IGF-IR/IRS-1 expression inversely correlates with high proliferation rate in dedifferentiated breast cancers. The strong correlation of IGF-IR and IRS-1 down-regulation with tumor progression suggests the use of IGF-IR and IRS-1 as a novel set of marker proteins for tumor grading.

Antagonists of growth hormone-releasing hormone arrest the growth of MDA-MB-468 estrogen-independent human breast cancers in nude mice

Since antagonists of growth hormone-releasing hormone (GH-RH) inhibit proliferation of various tumors, in this study we investigated the effects of GH-RH antagonists MZ-5-156 or JV-1-36 on growth of estrogen-independent MDA-MB-468 human breast cancers xenografted into nude mice. Both GH-RH antagonists administered at a dose of 20 microg/day induced regression of some and growth-arrest of other tumors, while control tumors continued to grow. After 5 weeks of therapy with MZ-5-156 or JV-1-36, final volume and weight of MDA-MB-468 tumors were significantly decreased (all p values < 0.001) and serum IGF-I levels as well as tumor IGF-I mRNA expression were reduced as compared with controls. High affinity binding sites for IGF-I were detected by the ligand binding method. Gene expression of human IGF-I receptors, as measured by the RT-PCR, was not significantly different in control and treated MDA-MB-468 tumors. In cell culture, IGF-I did not stimulate, GH-RH slightly stimulated, while MZ-5-156 and JV-1-36 inhibited proliferation of MDA-MB-468 cells known to possess defective insulin and IGF-I receptor signaling. The expression of mRNA for human GH-RH was found in five of 8 tumors treated with GH-RH antagonists, and in one of the five control tumors. These results suggest that GH-RH antagonists inhibit MDA-MB-468 breast cancers possibly through mechanisms involving interference with locally produced GH-RH.

Influence of adjuvant chemotherapy with cyclophosphamide, methotrexate and 5-fluorouracil on plasma insulin-like growth factor-I and chosen hormones in breast cancer pre-menopausal patients

OBJECTIVE

: To investigate the effect of chemotherapy on levels of IGF-I in patients with breast cancer.

BACKGROUND

The latest reports on the role of the insulin-like growth factor (IGF)-I in breast cancer pathogenesis emphasize the importance of the effect of therapy on plasma IGF-I concentration and more generally on the hormonal state of the patient.

METHOD

Twenty-four breast cancer patients on adjuvant chemotherapy with cyclophosphamide, methotrexate and 5-fluorouracil (CMF) were studied along with 16 healthy pre-menopausal women.

RESULTS

Plasma IGF-I concentration (determined by RIA method) in breast cancer patients prior to treatment did not differ significantly from that of healthy women, but it was significantly decreased after the first cycle of CMF, and significantly lowered as compared to a group of healthy women.

CONCLUSION

Further research into the significance of these findings is necessary. No interaction was found between mean IGF-I and growth hormone, prolactin, estradiol, progesterone, cortisol, met-enkephalin or melatonin concentrations.

IGF and insulin action in the mammary gland: lessons from transgenic and knockout models

Transgenic and knockout mice have become valuable experimental systems with which to study specific molecular events within the mammary gland of an intact animal. These models have provided a wealth of information about the effects of a number of oncogenes and growth factors. This review focuses on results obtained from the application of transgenic and knockout models to determine the roles of insulin and insulin-like growth factors (IGF) in the regulation of mammary gland development, lactation and tumorigenesis. Transgenic models which overexpress IGF-I or -II display specific alterations in mammary gland development and an increased incidence of mammary tumors. Analysis of mammary gland development in knockout mice which are deficient in IGF-I or the IGF-I receptor supports the conclusion that the IGF system is important for normal mammary gland development. This review discusses these observations in detail and attempts to fit them into a larger picture of IGF and insulin action in the mammary gland.

Alcohol intake and late-stage promotion of breast cancer

Breast cancer risk in women rises with increasing alcohol intake and is widely assumed to be mediated by increased oestrogen concentrations. However, observations that mechanisms and risk are likely to differ between pre- and postmenopausal women suggest that the postmenopausal disease in particular, may involve a promoting role for concomitants of hyperinsulinaemia which is commonly associated with alcoholic cirrhosis of the liver. The MEDLINE database and ongoing studies were examined for clinical, epidemiological and laboratory data on; (a) alcohol-related increase in the incidence of breast cancer in relation to menopausal status, oestrogen concentrations and the oestrogen receptor (ER) status of the tumour; (b) activation of insulin-like growth factor 1 receptor (IGF1R) in mammary tissue by alcohol-related hyperinsulinaemia; (c) interaction between ER and IGF1R in breast cancer cell systems. Epidemiological association between alcohol intake and increased breast cancer risk is more clearly seen in postmenopausal than premenopausal women, and a significant risk is associated with intake of more than two drinks (over 30 g) daily over a period of years. Alcohol-related hyperinsulinaemia is reported to increase with increasing degrees of cirrhosis and damage to liver function. Laboratory evidence suggests that hyperinsulinaemia can stimulate expression of IGF1R in mammary tissue, and this protein is likely to have a crucial role in mitogenesis and transformation to an oestrogen-independent malignant phenotype. It is postulated that in women with a history of long-term intake of moderate quantities of alcohol, the concomitants of hyperinsulinaemia may help to stimulate progression in precancerous breast lesions in the years leading up to the menopause and may increase the risk of breast cancer manifesting after the menopause.

Hormone therapy failure in human prostate cancer: analysis by complementary DNA and tissue microarrays

BACKGROUND

The molecular mechanisms underlying the progression of prostate cancer during hormonal therapy have remained poorly understood. In this study, we developed a new strategy for the identification of differentially expressed genes in hormone-refractory human prostate cancer by use of a combination of complementary DNA (cDNA) and tissue microarray technologies.

METHODS

Differences in gene expression between hormone-refractory CWR22R prostate cancer xenografts (human prostate cancer transplanted into nude mice) and a xenograft of the parental, hormone-sensitive CWR22 strain were analyzed by use of cDNA microarray technology. To validate the data from cDNA microarrays on clinical prostate cancer specimens, a tissue microarray of specimens from 26 prostates with benign prostatic hyperplasia, 208 primary prostate cancers, and 30 hormone-refractory local recurrences was constructed and used for immunohistochemical detection of protein expression.

RESULTS

Among 5184 genes surveyed with cDNA microarray technology, expression of 37 (0.7%) was increased more than twofold in the hormone-refractory CWR22R xenografts compared with the CWR22 xenograft; expression of 135 (2.6%) genes was reduced by more than 50%. The genes encoding insulin-like growth factor-binding protein 2 (IGFBP2) and 27-kd heat-shock protein (HSP27) were among the most consistently overexpressed genes in the CWR22R tumors. Immunohistochemical analysis of tissue microarrays demonstrated high expression of IGFBP2 protein in 100% of the hormone-refractory clinical tumors, in 36% of the primary tumors, and in 0% of the benign prostatic specimens (two-sided P =.0001). Overexpression of HSP27 protein was demonstrated in 31% of the hormone-refractory tumors, in 5% of the primary tumors, and in 0% of the benign prostatic specimens (two-sided P =.0001).

CONCLUSIONS

The combination of cDNA and tissue microarray technologies enables rapid identification of genes associated with progression of prostate cancer to the hormone-refractory state and may facilitate analysis of the role of the encoded gene products in the pathogenesis of human prostate cancer.

Do insulin-like growth factors mediate the effect of alcohol on breast cancer risk?

Despite a large number of epidemiologic studies demonstrating an increased risk of breast cancer in association with alcohol consumption, a causal relationship between alcohol intake and breast cancer risk remains to be determined. Several biological mechanisms have been proposed, but none of them explains well the features of the association, i.e. a modest increase in risk, a limited range of dose-response relationship and no further increase in risk among heavy drinkers. A new mechanism underlying a possible biological role of alcohol in breast cancer is proposed in this paper. Moderate consumption of alcohol increases the production of insulin-like growth factors (IGFs) by the liver and elevated IGFs via circulation stimulate or promote the development and/or growth of breast cancer. The effect of alcohol on IGF production declines among heavy drinkers as alcohol-caused liver-function damage results in no further increase in IGF production. Therefore, compared to moderate drinkers, heavy alcohol users do not have a higher risk of breast cancer.

The biology of breast cancer

This article focuses on the major hormones and growth factors for which a critical role in normal mammary growth has been clearly defined. Certainly other hormonal systems and growth factors could also affect breast cancer initiation and progression, but their exact contribution to normal and/or malignant breast cell growth is poorly delineated. Examples of such factors include somatostatin, mammostatin, mammary-derived growth inhibitor (MDGI), mammary-derived growth factor-1 (MDGF-1), inhibins, activins, androgens, glucocorticoids, vitamin D, thyroid hormones, ecosinoids, and oxytocin. Clearly, the hormonal regulation of breast cancer cell growth and survival is multifaceted and very complex. In particular, the effects of estrogens and anti-estrogens on breast cells may depend on their interaction with a wide variety of other pathways. In addition, these interactions may vary among individual breast tumors depending on other genetic changes in the tumor cells that have not been discussed here, such as oncogene activation and loss of tumor suppressors. A more detailed understanding of how cells circumvent a dependency on these pathways is greatly needed in order to identify new biological targets and to design novel therapies for breast cancers that are resistant to anti-estrogen therapy. Such agents could be used alone or in combination with anti-estrogens to improve response to a second course of hormonal therapy.

Insulin-like growth factors in human breast cancer

IGF1 and IGF2 are circulating peptide hormones and locally-acting growth factors with both paracrine and autocrine functions. IGF1 and IGF2 signal through a common tyrosine kinase receptor, the insulin-like growth factor 1 receptor (IGF1R), and have mitogenic, cell survival, and insulin-like actions that are essential for embryogenesis, post-natal growth physiology, and breast development. The activities of IGF1 and 2 are tightly-regulated by a network of binding proteins and targeted degradation mechanisms. This complex regulatory system is disrupted in breast cancer, leading to excess IGF1R signaling. Evidence for this statement includes: a) breast cancers are infiltrated with IGF2 expressing stromal cells; b) mannose 6-phosphate/IGF2 receptor (M6P/IGF2R) is mutated in breast cancer, leading to loss of IGF2 degradation; c) IGF1R is overexpressed by malignant breast epithelial cells, and in some cases IGF1R is amplified; and d) complex changes in IGF binding protein expression occur during breast cancer progression which most likely also affect IGF1 and 2 signaling. The clinical importance of these epigenetic and genetic changes has recently been stressed by the finding that IGF1R signaling alters the apoptotic response of breast cancer cells to genotoxic stress and, in addition, IGF1R activation sensitizes cells to estrogen by inducing phosphorylation of the estrogen receptor. As a consequence of these findings, we propose that IGF analysis of breast cancer samples should shift from prognostic studies to an evaluation of IGF ligands, receptors, and binding proteins as resistance/sensitivity markers for radiation, chemotherapy, and endocrine therapy.

The pleckstrin homology and phosphotyrosine binding domains of insulin receptor substrate 1 mediate inhibition of apoptosis by insulin

Insulin and insulin-like growth factor 1 (IGF-1) evoke diverse biological effects through receptor-mediated tyrosine phosphorylation of insulin receptor substrate (IRS) proteins. We investigated the elements of IRS-1 signaling that inhibit apoptosis of interleukin 3 (IL-3)-deprived 32D myeloid progenitor cells. 32D cells have few insulin receptors and no IRS proteins; therefore, insulin failed to inhibit apoptosis during IL-3 withdrawal. Insulin stimulated mitogen-activated protein kinase in 32D cells expressing insulin receptors (32DIR) but failed to activate the phosphatidylinositol 3 (PI 3)-kinase cascade or to inhibit apoptosis. By contrast, insulin stimulated the PI 3-kinase cascade, inhibited apoptosis, and promoted replication of 32DIR cells expressing IRS-1. As expected, insulin did not stimulate PI 3-kinase in 32DIR cells, which expressed a truncated IRS-1 protein lacking the tail of tyrosine phosphorylation sites. However, this truncated IRS-1 protein, which retained the NH2-terminal pleckstrin homology (PH) and phosphotyrosine binding (PTB) domains, mediated phosphorylation of PKB/akt, inhibition of apoptosis, and replication of 32DIR cells during insulin stimulation. These results suggest that a phosphotyrosine-independent mechanism mediated by the PH and PTB domains promoted antiapoptotic and growth actions of insulin. Although PI 3-kinase was not activated, its phospholipid products were required, since LY294002 inhibited these responses. Without IRS-1, a chimeric insulin receptor containing a tail of tyrosine phosphorylation sites derived from IRS-1 activated the PI 3-kinase cascade but failed to inhibit apoptosis. Thus, phosphotyrosine-independent IRS-1-linked pathways may be critical for survival and growth of IL-3-deprived 32D cells during insulin stimulation.