Correlation of insulin-like growth factor-binding protein-3 messenger RNA with protein expression in primary breast cancer tissues: detection of higher levels in tumors with poor prognostic features

Construction and validation of a novel IGFBP3-related signature to predict prognosis and therapeutic decision making for Hepatocellular Carcinoma

Background

IGFBP3 plays a pivotal role in carcinogenesis by being anomalously expressed in some malignancies. However, the clinical value of IGFBP3 and the role of IGFBP3-related signature in HCC remain unclear.

Methods

Multiple bioinformatics methods were used to determine the expression and diagnostic values of IGFBP3. The expression level of IGFBP3 was validated by RT-qPCR and IHC. A IGFBP3-related risk score (IGRS) was built via correlation analysis and LASSO Cox regression analysis. Further analyses, including functional enrichment, immune status of risk groups were analyzed, and the role of IGRS in guiding clinical treatment was also evaluated.

Results

IGFBP3 expression was significantly downregulated in HCC. IGFBP3 expression correlated with multiple clinicopathological characteristics and demonstrated a powerful diagnostic capability for HCC. In addition, a novel IGRS signature was developed in TCGA, which exhibited good performance for prognosis prediction and its role was further validated in GSE14520. In TCGA and GSE14520, Cox analysis also confirmed that the IGRS could serve as an independent prognostic factor for HCC. Moreover, a nomogram with good accuracy for predicting the survival of HCC was further formulated. Additionally, enrichment analysis showed that the high-IGRS group was enriched in cancer-related pathways and immune-related pathways. Additionally, patients with high IGRS exhibited an immunosuppressive phenotype. Therefore, patients with low IGRS scores may benefit from immunotherapy.

Conclusions

IGFBP3 can act as a new diagnostic factor for HCC. IGRS signature represents a valuable predictive tool in the prognosis prediction and therapeutic decision making for Hepatocellular Carcinoma.

Identifying key multifunctional components shared by critical cancer and normal liver pathways via SparseGMM

Despite the abundance of multimodal data, suitable statistical models that can improve our understanding of diseases with genetic underpinnings are challenging to develop. Here, we present SparseGMM, a statistical approach for gene regulatory network discovery. SparseGMM uses latent variable modeling with sparsity constraints to learn Gaussian mixtures from multiomic data. By combining coexpression patterns with a Bayesian framework, SparseGMM quantitatively measures confidence in regulators and uncertainty in target gene assignment by computing gene entropy. We apply SparseGMM to liver cancer and normal liver tissue data and evaluate discovered gene modules in an independent single-cell RNA sequencing (scRNA-seq) dataset. SparseGMM identifies PROCR as a regulator of angiogenesis and PDCD1LG2 and HNF4A as regulators of immune response and blood coagulation in cancer. Furthermore, we show that more genes have significantly higher entropy in cancer compared with normal liver. Among high-entropy genes are key multifunctional components shared by critical pathways, including p53 and estrogen signaling.

Roles of IGFBP-3 in cell migration and growth in an endophytic tongue squamous cell carcinoma cell line

Insulin-like growth factor binding protein-3 (IGFBP-3) is a member of the IGFBP family that has high affinity for IGFs and functions as either an oncogene or tumor suppressor in various types of cancer. We previously found that IGFBP3 mRNA levels are higher in endophytic-type human tongue squamous cell carcinoma (TSCC) that is more invasive and more prone to metastasis than exophytic and superficial types. This finding prompted us to investigate the roles of IGFBP-3 in TSCC using SAS cells, which were originally derived from endophytic-type TSCC. Specifically, we used SAS cells that express a fluorescent ubiquitination-based cell-cycle indicator (Fucci). RNA-sequencing analysis indicated that IGFBP-3 is associated with cell migration and cell growth. In fact, IGFBP-3 knockdown downregulates cell migration and causes cells to arrest in G₁. This migratory potential appears to be cell cycle–independent. IGFBP-3 knockdown also reduced levels of secreted IGFBP-3; however, decreased migratory potential was not rescued by exogenous recombinant human IGFBP-3. Furthermore, ERK activity was downregulated by IGFBP-3 depletion, which suggests that MEK/ERK signaling may be involved in IGFBP-3-mediated cell migration. We therefore conclude that intracellular IGFBP-3 enhances cell migration independently of the cell cycle in TSCC with a higher metastatic potential.

Interaction between GRP78 and IGFBP-3 Affects Tumourigenesis and Prognosis in Breast Cancer Patients

Insulin-like growth factor binding protein 3 (IGFBP-3) plays a key role in breast cancer progression and was recently shown to bind to the chaperone protein glucose-regulated protein 78 (GRP78); however, the clinical significance of this association remains poorly investigated. Here we report a direct correlation between the expression of GRP78 and IGFBP-3 in breast cancer cell lines and tumour sections. Kaplan-Meier survival plots revealed that patients with low GRP78 expression that are positive for IGFBP-3 had poorer survival rates than those with low IGFBP-3 levels, and we observed a similar trend in the publicly available METABRIC gene expression database. With breast cancer cells, in vitro IGFBP-3 enhanced induced apoptosis, however when GRP78 expression was silenced the actions of IGFBP-3 were switched from increasing to inhibiting ceramide (C2)-induced cell death and promoted cell invasion. Using immunofluorescence and cell surface biotinylation, we showed that knock-down of GRP78 negated the entry of IGFBP-3 into the cells. Together, our clinical and experimental results suggest that loss of GRP78 reduces IGFBP-3 entry into cells switching its actions to promote tumorigenesis and predicts a poor prognosis in breast cancer patients.

Biomarker Modulation Study of Celecoxib for Chemoprevention in Women at Increased Risk for Breast Cancer: A Phase II Pilot Study

In preclinical studies, celecoxib has been associated with reduced risk of breast cancer. In this study, the aim was to assess the biomodulatory effect of celecoxib on blood and benign breast tissue biomarkers in women at increased risk for breast cancer. Women at increased risk for breast cancer [5-year Gail risk score of >1.67%, history of atypical hyperplasia, lobular carcinoma in situ, or previous estrogen receptor (ER)-negative breast cancer] were treated with celecoxib at 400 mg orally twice daily for 6 months. Participants underwent random periareolar fine needle aspiration and blood draw at baseline and at 6 months for analysis of biomarkers: serum levels of insulin-like growth factor 1 (IGF-1), IGF-binding protein 1 (IGFBP-1), and IGFBP-3; tissue expression of Ki-67 and ER; as well as cytology. Forty-nine patients were eligible for analysis. Median IGFBP-1 levels increased significantly from 6.05 ng/mL at baseline to 6.93 ng/mL at 6 months (P = 0.04), and median IGFBP-3 levels decreased significantly from 3,593 ng/mL to 3,420 ng/mL (P = 0.01). We also detected favorable changes in cytology of 52% of tested sites after 6 months of celecoxib therapy. No changes in tissue Ki-67 and ER expression levels were observed. No grade 3 or 4 toxicity was recorded. Celecoxib was well tolerated and induced favorable changes in serum biomarkers as well as cytology in this pilot phase II trial. A phase IIb placebo-controlled study with celecoxib could be considered for women at increased risk for breast cancer.

Blocking transmembrane219 protein signaling inhibits autophagy and restores normal cell death

Autophagy plays a vital role in tumor therapy and survival of dormant tumor cells. Here we describe a novel function of a protein known as Transmembrane 219 (TM219) as an autophagy activator. TM219 is a small membrane protein expressed in all known human tissues except the thymus. We used biochemical approaches to identify calmodulin and calmodulin dependent protein kinase II as a part of TM219 protein complex. Then, we employed in vitro reconstitution system and fluorescence anisotropy to study the requirements of TM219 to bind calmodulin in vitro. We also used this system to study the effects of a synthetic peptide derived from the sequence of the short cytoplasmic tail of TM219 (SCTT) on calmodulin-TM219 receptor interactions. We conjugated SCTT peptide with a pH Low Insertion peptide (pHLIP) for optimal cellular delivery. We finally tested the effects of SCTT-pHLIP on triple negative human breast cancer cells in three dimension culture. Our data defined a novel function of TM219 protein and an efficient approach to inhibit it.

The prognostic values of insulin-like growth factor binding protein in breast cancer

Insulin-like growth factor binding proteins (IGFBPs) are a family of proteins binding to insulin-like growth factors, generally consisting 6 high-affinity IGFBPs, namely IGFBP1 through IGFBP6. IGFBP family members have been indicated to be involved in the development and progression of tumors and may be useful prognostic biomarkers in various malignancies. However, the prognostic role of individual IGFBPs, especially at the mRNA level in breast cancer patients remains elusive.We accessed the prognostic roles of IGFBPs family (IGFBP1-6) in breast cancer through the "Kaplan-Meier plotter" online database and OncoLnc database.Our results showed that the high expression of IGFBP1 mRNA was associated with favorable relapsed free survival (RFS) in all breast cancer patients. The high expression of IGFBP2 mRNA was associated with favorable overall survival (OS) and RFS in all breast cancer patients. The high expression of IGFBP3 mRNA was significantly correlated to worsen RFS in all breast cancer patients. The high expression of IGFBP4 mRNA was associated with favorable OS, RFS, distant metastasis-free survival, and post-progression survival in all breast cancer patients.Our results indicated that expression of IGFBPs mRNA may have prognostic values in breast cancer patients, and have a benefit for developing tools to predict the prognosis more accurately.

Contrasting effects of IGF binding protein-3 expression in mammary tumor cells and the tumor microenvironment

IGFBP-3 has both stimulatory and inhibitory effects on cancer progression. The growth of EO771 mammary carcinoma cells as syngeneic tumors in C57BL/6 mice is reduced in Igfbp3-null (BP3KO) mice, suggesting that systemic IGFBP-3 enhances tumor progression. In this study we assessed the growth of EO771 cells expressing human IGFBP-3 in BP3KO mice. Cells expressing hIGFBP-3 showed decreased proliferation in vitro and increased levels of IGF-1 receptor (IGF1R) protein but not mRNA, consistent with sequestration of endogenous IGF by IGFBP-3. The growth rate of these cells was restored by exposure to IGF-1 or analogues with reduced affinity for IGFBP-3 (long Arg³-IGF-1) or IGF1R (Leu²⁴-IGF-1). In EO771 cells implanted orthotopically into mice, hIGFBP-3 expression by the cells inhibited tumor establishment in BP3KO but not wild-type mice. For tumors that successfully established, final weight was not affected significantly by hIGFBP-3 expression. However, final tumor weight was inversely related to intratumoral T cell counts, and sera from BP3KO mice with tumors showed low-titer immunoreactivity against IGFBP-3. The contrasting effects on tumor establishment and progression of IGFBP-3 expressed by mammary carcinoma cells, compared to systemic stromal and circulating IGFBP-3, highlights the complexity of growth regulation by IGFBP-3 in mammary tumors.

Enhancement of mammary tumour growth by IGFBP-3 involves impaired T cell accumulation

Epidemiological studies show an association between obesity and poor breast cancer prognosis. We previously demonstrated that global IGFBP-3 deficiency, in IGFBP-3-null mice, resulted in a 50% reduction in mammary tumour growth over 3 weeks relative to tumours in wild-type (WT) C57BL/6 mice. This growth reduction was ameliorated by high fat feeding-induced obesity. This study aimed to examine how IGFBP-3 promotes tumour growth by influencing the immune tumour microenvironment in healthy and obese mice. Syngeneic EO771 cells, which lack detectable IGFBP-3 expression, were grown as orthotopic tumours in WT and IGFBP-3-null C57BL/6 mice placed on either a control chow or a high-fat diet (HFD), and examined by quantitative PCR and immunohistochemistry. In WT mice, increased stromal expression of IGFBP-3 was positively associated with tumour growth, supporting the hypothesis that IGFBP-3 in the microenvironment promotes tumour progression. Examining markers of immune cell subsets, gene expression of Ifng, Cd8a, Cd8b1 and Tnf and CD8 measured by immunohistochemistry were elevated in tumours of IGFBP-3-null mice compared to WT, indicating an accumulation of CD8+ T cells, but this increase was absent if the IGFBP-3-null mice had been exposed to HFD. Expression of these genes was negatively associated with tumour growth. Although similar among groups overall, Nkg2d and Tnfsf10 tumoural expression was associated with decreased tumour growth. Overall, the results of this study provide an immune-based mechanism by which host IGFBP-3 may promote breast tumour growth in the EO771 murine breast cancer model, and suggest that targeting IGFBP-3 might make a novel contribution to immune therapy for breast cancer.

Significant Changes in Circulating Plasma Levels of IGF1 and IGFBP3 after Conventional or Dose-Intensified Adjuvant Treatment of Breast Cancer Patients with one to three Positive Lymph Nodes

The insulin-like growth factor 1 (IGF1) and its binding protein IGFBP3 (insulin-like growth factor binding protein 3) play a pivotal role during the growth and development of tissues. The purpose of this study was to evaluate the influence of anthracycline- and taxane-containing adjuvant chemotherapy in breast cancer patients on the circulating plasma levels of IGF1 and its main binding protein, IGFBP3. This investigation was part of a prospective randomized phase III study in which breast cancer patients were treated with either conventional or dose-intensified adjuvant chemotherapy. The factors were quantified in the plasma of 151 patients with a commercially available sandwich enzyme immunoassay. Before therapy, both parameters were within the normal range in most patients (n=145 and n=144). After therapy, both factors had increased significantly by 29% (IGF1) and 19% (IGFBP3), with the highest increase being observed in the dose-intensified group. Correlations with patient and tumor characteristics revealed a relatively higher increase in both parameters in premenopausal patients, patients with lower-grade tumors, more positive lymph nodes, larger tumor volume, and positive hormone receptor status. No correlation was found with the HER2 expression of the tumors.

Aiming for the Insulin-like Growth Factor-1 system in breast cancer therapeutics

Despite the major discoveries occurred in oncology the recent years, breast malignancies remain one of the most common causes of cancer-related deaths for women in developed countries. Development of HER2-targeting drugs has been considered a breakthrough in anti-cancer approaches and alluded to the potential of targeting growth factors in breast cancer (BrCa) therapeutics. More than twenty-five years have passed since the Insulin-like Growth Factor-1 (IGF-1) system was initially recognized as a potential target candidate in BrCa therapy. To date, a growing body of studies have implicated the IGF-1 signaling with the BrCa biology. Despite the promising experimental evidence, the impression from clinical trials is rather disappointing. Several reasons may account for this and the last word regarding the efficacy of this system as a target candidate in BrCa therapeutics is probably not written yet. Herein, we provide the theoretical basis, as well as, a comprehensive overview of the current literature, regarding the different strategies targeting the various components of the IGF-1/IGF-1R axis in several pathophysiological aspects of BrCa, including the tumor micro-environment and cancer stemness. In addition, we review the rationale for targeting the IGF-1 system in the different BrCa molecular subtypes and in treatment resistant breast tumors with a focus on both the molecular mechanisms and on the clinical perspectives of such approaches in specific population subgroups. We also discuss the future challenges, as well as, the development of novel molecules and strategies targeting the system and suggest potential improvements in the field.

Triple-negative breast cancer and its association with obesity

Triple-negative breast cancer (TNBC) is a subtype of breast cancer that lacks expression of the estrogen and progesterone receptor and does not overexpress human epidermal growth factor 2 receptor protein. TNBC is associated with special characteristics, including aggressiveness, poor prognosis and poor response to treatment, and has been attracting increasing attention worldwide. Obesity is a well-documented factor exerting a significant effect on the development of breast cancer, including TNBC. The purpose of the present review was to focus on the association between obesity and TNBC and provide a summary of novel research findings. The aim was to highlight the association between TNBC and obesity and provide an overview of novel outlooks on clinical issues, biological rationale, novel targeted therapies and prognosis, in order to draw attention to the significance of weight management, primary prevention, early diagnosis and treatment of this intractable disease.

Involvement of p53 in insulin-like growth factor binding protein-3 regulation in the breast cancer cell response to DNA damage

Chemotherapy drugs that induce apoptosis by causing DNA double-strand breaks, upregulate the tumor suppressor p53. This study investigated the regulation of the growth-regulatory protein insulin-like growth factor binding protein-3 (IGFBP-3), a p53 target, by DNA-damaging agents in breast cancer cells. IGFBP-3 was upregulated 1.4- to 13-fold in response to doxorubicin and etoposide in MCF-10A, Hs578T, MCF-7 and T47D cells, which express low to moderate basal levels of IGFBP-3. In contrast, IGFBP-3 was strongly downregulated by these agents in cells with high basal levels of IGFBP-3 (MDA-MB-231, MDA-MB-436 and MDA-MB-468). In MDA-MB-468 cells containing the R273H p53 mutation, reported to display gain-of-function properties, chemotherapy-induced suppression of IGFBP-3 was not reversed by the p53 reactivating drug, PRIMA-1, or by p53 silencing, suggesting that the decrease in IGFBP-3 following DNA damage is not a mutant p53 gain-of-function response. SiRNA-mediated downregulation of endogenous IGFBP-3 modestly attenuated doxorubicin-induced apoptosis in MDA-MB-468 and Hs578T cells. IGFBP-3 downregulation in some breast cancer cell lines in response to DNA-damaging chemotherapy may have clinical implications because suppression of IGFBP-3 may modulate the apoptotic response. These observations provide further evidence that endogenous IGFBP-3 plays a role in breast cancer cell responsiveness to DNA damaging therapy.

Targeting Insulin-Like Growth Factor Binding Protein-3 Signaling in Triple-Negative Breast Cancer

Insulin-like growth factor binding protein-3 (IGFBP-3) is a key regulatory molecule of the IGF axis and can function in a tissue-specific way as both a tumor suppressor and promoter. Triple-negative breast cancer (TNBC) has high tumor expression of IGFBP-3 associated with markers of poor prognosis and, although accounting for 15-20% of all breast cancers, is responsible for disproportionate rates of morbidity and mortality. Because they lack estrogen and progesterone receptors and overexpression of HER2, TNBC are resistant to treatments that target these molecules, making the development of new therapies an important goal. In addition to frequent high expression of IGFBP-3, these tumors also express EGFR highly, but targeting EGFR signaling alone in TNBC has been of little success. Identification of a functional growth-stimulatory interaction between EGFR and IGFBP-3 signaling prompted investigation into cotargeting these pathways as a novel therapy for TNBC. This involves inhibition of both EGFR kinase activity and a mediator of IGFBP-3's stimulatory bioactivity, sphingosine kinase-1 (SphK1), and has shown promise in a preclinical setting. Functional interaction between EGFR and IGFBP-3 may also promote chemoresistance in TNBC, and delineating the mechanisms involved may identify additional targets for development of therapies in cancers that express both IGFBP-3 and EGFR.

The role of the insulin-like growth factor-1 system in breast cancer

IGF-1 is a potent mitogen of major importance in the mammary gland. IGF-1 binding to the cognate receptor, IGF-1R, triggers a signaling cascade leading to proliferative and anti-apoptotic events. Although many of the relevant molecular pathways and intracellular cascades remain to be elucidated, a growing body of evidence points to the important role of the IGF-1 system in breast cancer development, progression and metastasis. IGF-1 is a point of convergence for major signaling pathways implicated in breast cancer growth. In this review, we provide an overview and concise update on the function and regulation of IGF-1 as well as the role it plays in breast malignancies.

Differences in IGF-axis protein expression and survival among multiethnic breast cancer patients

There is limited knowledge about the biological basis of racial/ethnic disparities in breast cancer outcomes. Aberrations in IGF signaling induced by obesity and other factors may contribute to these disparities. This study examines the expression profiles of the insulin-like growth factor (IGF)-axis proteins and the association with breast cancer survival across a multiethnic population. We examined the expression profiles of the IGF1, IGF1R, IGFBP2 (IGF-binding proteins), and IGFBP3 proteins in breast tumor tissue and their relationships with all-cause and breast cancer-specific survival up to 17 years postdiagnosis in a multiethnic series of 358 patients in Hawaii, USA. Native Hawaiians, Caucasians, and Japanese were compared. Covariates included demographic and clinical factors and ER/PR/HER2 (estrogen receptor/progesterone receptor/human epidermal growth factor receptor-2) status. In Native Hawaiian patients, IGFBP2 and IGFBP3 expression were each independently associated with overall and breast cancer mortality (IGFB2: HR_mort = 10.96, 95% CI: 2.18–55.19 and HR_mort = 35.75, 95% CI: 3.64–350.95, respectively; IGFBP3: HR_mort = 5.16, 95% CI: 1.27–20.94 and HR_mort = 8.60, 95% CI: 1.84–40.15, respectively). IGF1R expression was also positively associated with all-cause mortality in Native Hawaiians. No association of IGF-axis protein expression and survival was observed in Japanese or Caucasian patients. The interaction of race/ethnicity and IGFBP3 expression on mortality risk was significant. IGF-axis proteins may have variable influence on breast cancer progression across different racial/ethnic groups. Expression of binding proteins and receptors in breast tumors may influence survival in breast cancer patients by inducing aberrations in IGF signaling and/or through IGF-independent mechanisms. Additional studies to evaluate the role of the IGF-axis in breast cancer are critical to improve targeted breast cancer treatment strategies.

Vasohibin‑2 promotes proliferation in human breast cancer cells via upregulation of fibroblast growth factor‑2 and growth/differentiation factor‑15 expression

Vasohibin‑2 (VASH2) is an angiogenic factor, and has been previously reported to be a cancer‑related gene, with cytoplasmic and karyotypic forms. In the current study VASH2 expression in human breast cancer tissue and adjacent non‑cancerous tissue was investigated with immunohistochemistry. MCF‑7 and BT474 human breast cancer cells were transfected with lentiviral constructs to generate in vitro VASH2 overexpression and knockdown models. In addition, BALB/cA nude mice were inoculated subcutaneously with transfected cells to generate in vivo models of VASH2 overexpression and knockdown. The effect of VASH2 on cell proliferation was investigated using a bromodeoxyuridine assay in vitro and immunohistochemistry of Ki67 in xenograft tumors. Growth factors were investigated using a human growth factor array, and certain factors were further confirmed by an immunoblot. The results indicated that the expression level of cytoplasmic VASH2 was higher in breast cancer tissues with a Ki67 (a proliferation marker) level of ≥14%, compared with tissues with a Ki67 level of <14%. VASH2 induced proliferation in vitro and in vivo. Four growth factors activated by VASH2 were identified as follows: Fibroblast growth factor 2 (FGF2), growth/differentiation factor‑15 (GDF15), insulin‑like growth factor‑binding protein (IGFBP)3 and IGFBP6. FGF2 and GDF15 may contribute to VASH2‑induced proliferation. The current study identified a novel role for VASH2 in human breast cancer, and this knowledge suggests that VASH2 may be a novel target in breast cancer treatment.

IGF binding proteins in cancer: mechanistic and clinical insights

The six members of the family of insulin-like growth factor (IGF) binding proteins (IGFBPs) were originally characterized as passive reservoirs of circulating IGFs, but they are now understood to have many actions beyond their endocrine role in IGF transport. IGFBPs also function in the pericellular and intracellular compartments to regulate cell growth and survival - they interact with many proteins, in addition to their canonical ligands IGF-I and IGF-II. Intranuclear roles of IGFBPs in transcriptional regulation, induction of apoptosis and DNA damage repair point to their intimate involvement in tumour development, progression and resistance to treatment. Tissue or circulating IGFBPs might also be useful as prognostic biomarkers.

Inhibition of insulin-like growth factor-binding protein-3 signaling through sphingosine kinase-1 sensitizes triple-negative breast cancer cells to EGF receptor blockade

The type I EGF receptor (EGFR or ErbB1) and insulin-like growth factor-binding protein-3 (IGFBP-3) are highly expressed in triple-negative breast cancer (TNBC), a particularly aggressive disease that cannot be treated with conventional therapies targeting the estrogen or progesterone receptors (ER and PR), or HER2. We have shown previously in normal breast epithelial cells that IGFBP-3 potentiates growth-stimulatory signaling transduced by EGFR, and this is mediated by the sphingosine kinase-1 (SphK1)/sphingosine 1-phosphate (S1P) system. In this study, we investigated whether cotargeting the EGFR and SphK1/S1P pathways in TNBC cells results in greater growth inhibition compared with blocking either alone, and might therefore have novel therapeutic potential in TNBC. In four TNBC cell lines, exogenous IGFBP-3 enhanced ligand-stimulated EGFR activation, associated with increased SphK1 localization to the plasma membrane. The effect of exogenous IGFBP-3 on EGFR activation was blocked by pharmacologic inhibition or siRNA-mediated silencing of SphK1, and silencing of endogenous IGFBP-3 also suppressed EGF-stimulated EGFR activation. Real-time analysis of cell proliferation revealed a combined effect of EGFR inhibition by gefitinib and SphK1 inhibition using SKi-II. Growth of MDA-MB-468 xenograft tumors in mice was significantly inhibited by SKi-II and gefitinib when used in combination, but not as single agents. We conclude that IGFBP-3 promotes growth of TNBC cells by increasing EGFR signaling, that this is mediated by SphK1, and that combined inhibition of EGFR and SphK1 has potential as an anticancer therapy in TNBC in which EGFR and IGFBP-3 expression is high.

Insulin-like growth factor binding protein-3 (IGFBP-3): Novel ligands mediate unexpected functions

In addition to its important role in the regulation of somatic growth by acting as the major circulating transport protein for the insulin-like growth factors (IGFs), IGF binding protein-3 (IGFBP-3) has a variety of intracellular ligands that point to its function within major signaling pathways. The discovery of its interaction with the retinoid X receptor has led to the elucidation of roles in regulating the function of several nuclear hormone receptors including retinoic acid receptor-α, Nur77 and vitamin D receptor. Its interaction with the nuclear hormone receptor peroxisome proliferator-activated receptor-γ is believed to be involved in regulating adipocyte differentiation, which is also modulated by IGFBP-3 through an interaction with TGFβ/Smad signaling. IGFBP-3 can induce apoptosis alone or in conjunction with other agents, and in different systems can activate caspases -8 and -9. At least two unrelated proteins (LRP1 and TMEM219) have been designated as receptors for IGFBP-3, the latter with a demonstrated role in inducing caspase-8-dependent apoptosis. In contrast, IGFBP-3 also has demonstrated roles in survival-related functions, including the repair of DNA double-strand breaks through interaction with the epidermal growth factor receptor and DNA-dependent protein kinase, and the induction of autophagy through interaction with GRP78. The ability of IGFBP-3 to modulate the balance between pro-apoptotic and pro-survival sphingolipids by regulating sphingosine kinase 1 and sphingomyelinases may be integral to its role at the crossroads between cell death and survival in response to a variety of stimuli. The pleiotropic nature of IGFBP-3 activity supports the idea that IGFBP-3 itself, or pathways with which it interacts, should be investigated as targets of therapy for a variety of diseases.

Resveratrol regulates the cell viability promoted by 17β-estradiol or bisphenol A via down-regulation of the cross-talk between estrogen receptor α and insulin growth factor-1 receptor in BG-1 ovarian cancer cells

Endocrine disrupting chemicals (EDCs) and estrogens appear to promote development of estrogen-dependent cancers, including breast and ovarian carcinomas. In this study, we evaluated the cell viability effect of BPA on BG-1 human ovarian cancer cells, along with the growth inhibitory effect of resveratrol (trans-3,4,5-trihydroxystilbene; RES), a naturally occurring phytoestrogen. In addition, we investigated the underlying mechanism(s) of BPA and RES in regulating the interaction between estrogen receptor alpha (ERα) and insulin-like growth factor-1 receptor (IGF-1R) signals, a non- genomic pathway induced by 17β-estradiol (E2). BPA induced a significant increase in BG-1 cell growth and up-regulated mRNA levels of ERα and IGF-1R. In parallel with its mRNA level, the protein expression of ERα was induced, and phosphorylated insulin receptor substrate-1 (p-IRS-1), phosphorylated Akt1/2/3, and cyclin D1 were increased by BPA or E2. However, RES effectively reversed the BG-1 cell proliferation induced by E2 or BPA by inversely down-regulating the expressions of ERα, IGF-1R, p-IRS-1, and p-Akt1/2/3, and cyclin D1 at both transcriptional and translational levels. Taken together, these results suggest that RES is a novel candidate for prevention of tumor progression caused by EDCs, including BPA via effective inhibition of the cross-talk of ERα and IGF-1R signaling pathways.

Protein expression changes during human triple negative breast cancer cell line progression to lymph node metastasis in a xenografted model in nude mice

Triple negative breast cancers (TNBC) lacking hormone receptors and HER-2 amplification are very aggressive tumors. Since relevant differences between primary tumors and metastases could arise during tumor progression as evidenced by phenotypic discordances reported for hormonal receptors or HER-2 expression, in this analysis we studied changes that occurred in our TNBC model IIB-BR-G throughout the development of IIB-BR-G-_MTS6 metastasis to the lymph nodes (LN) in nude mice, using an antibody-based protein array to characterize their expression profile. We also analyzed their growth kinetics, migration, invasiveness and cytoskeleton structure in vitro and in vivo.

In vitro IIB-BR-G-_MTS6 cells grew slower but showed higher anchorage independent growth. In vivo IIB-BR-G-_MTS6 tumors grew significantly faster and showed a 100% incidence of LN metastasis after s.c. inoculation, although no metastasis was observed for IIB-BR-G. CCL3, IL1β, CXCL1, CSF2, CSF3, IGFBP1, IL1α, IL6, IL8, CCL20, PLAUR, PlGF and VEGF were strongly upregulated in IIB-BR-G-_MTS6 while CCL4, ICAM3, CXCL12, TNFRSF18, FIGF were the most downregulated proteins in the metastatic cell line. IIB-BR-G-_MTS6 protein expression profile could reflect a higher NFκB activation in these cells. In vitro, IIB-BR-G displayed higher migration but IIB-BR-G-_MTS6 had more elevated matrigel invasion ability. In agreement with that observation, IIB-BR-G-_MTS6 had an upregulated expression of MMP1, MMP9, MMP13, PLAUR and HGF. IIB-BR-G-_MTS6 tumors presented also higher local lymphatic invasion than IIB-BR-G but similar lymphatic vessel densities. VEGFC and VEGFA/B expression were higher both in vitro and in vivo for IIB-BR-G-_MTS6. IIB-BR-G-_MTS6 expressed more vimentin than IB-BR-G cells, which was mainly localized in the cellular extremities and both cell lines are E-cadherin negative.

Our results suggest that IIB-BR-G-_MTS6 cells have acquired a pronounced epithelial-to-mesenchymal transition phenotype. Protein expression changes observed between primary tumor-derived IIB-BR-G and metastatic IIB-BR-G-_MTS6 TNBC cells suggest potential targets involved in the control of metastasis.

Signalling pathways of insulin-like growth factors (IGFs) and IGF binding protein-3

Although the insulin-like growth factor (IGF) system is essential for normal growth and development, its dysregulation has been implicated in a range of pathological states. The peptide growth factors IGF-I and IGF-II exert their effects by binding to cell-surface heterotetrameric tyrosine kinase receptors and activating multiple intracellular signalling cascades, leading to changes in the expression of proteins essential for cell proliferation, survival and differentiation. The IGF system comprises multiple ligands, receptors and high-affinity IGF binding proteins (IGFBPs), with added complexity arising from crosstalk between its receptors and other key growth-regulatory pathways such as those activated by steroid hormones, integrins and other receptor tyrosine kinases. The IGFBPs are also increasingly recognised for their intrinsic growth-regulatory activity, and the ability of IGFBP-3 to modulate signalling pathways of nuclear hormone and growth factor receptors, as well as novel receptors, is believed to play a role both in normal physiology and in disease.

Involvement of insulin-like growth factor-binding protein-3 in the effects of histone deacetylase inhibitor MS-275 in hepatoma cells

Insulin-like growth factor-binding protein-3 (IGFBP-3) expression is frequently suppressed in liver cancers and can be reactivated by histone deacetylase (HDAC) inhibition. This study examined the role of IGFBP-3 in mediating the effects of the HDAC inhibitor MS-275 in liver cancer cells and identified IGFBP-3-dependent proteins that regulate proliferation and migration. In HepG2 cells, MS-275 inhibited DNA synthesis, cell cycle activity, and cell viability concomitantly with increased binding of acetylated histone H3 to IGFBP-3 promoter sequences and induction of IGFBP-3 expression. IGFBP-3 down-regulation by siRNA significantly reversed the inhibition of cell viability and DNA synthesis by MS-275, indicating an intermediary role for IGFBP-3. Induction of the cyclin-dependent kinase inhibitor p21 by MS-275 was attenuated by IGFBP-3 down-regulation, providing an explanation for IGFBP-3-dependent effects of MS-275 on cell cycle activity. In contrast, MS-275 stimulated HepG2 cell migration, an effect also inhibited by IGFBP-3 down-regulation. Among genes whose induction by MS-275 was attenuated by IGFBP-3 down-regulation, LYVE1 and THBS2 (thrombospondin-2) were identified as mediators of IGFBP-3-dependent effects of MS-275. Silencing of either protein had no effect on the inhibition of HepG2 viability by MS-275 but reversed its stimulatory effect on cell migration. We conclude that among genes up-regulated by MS-275, IGFBP-3 is a key mediator of effects on hepatoma cell growth and migration, involving IGFBP-3-dependent proteins p21 (proliferation) and LYVE1 and THBS2 (migration). The enhanced cell motility that accompanies reactivation of IGFBP-3 expression in liver cancer by HDAC inhibition suggests the possibility of increased metastatic spread despite inhibited cell proliferation.

Differential impacts of insulin-like growth factor-binding protein-3 (IGFBP-3) in epithelial IGF-induced lung cancer development

The IGF axis has been implicated in the risk of various cancers. We previously reported a potential role of tissue-derived IGF in lung tumor formation and progression. However, the role of IGF-binding protein (IGFBP)-3, a major IGFBP, on the activity of tissue-driven IGF in lung cancer development is largely unknown. Here, we show that IGF-I, but not IGF-II, protein levels in non-small-cell lung cancer (NSCLC) were significantly higher than those in normal and hyperplastic bronchial epithelium. We found that IGF-I and IGFBP-3 levels in NSCLC tissue specimens were significantly correlated with phosphorylated IGF-IR (pIGF-IR) expression. We investigated the impact of IGFBP-3 expression on the activity of tissue-driven IGF-I in lung cancer development using mice carrying lung-specific human IGF-I transgene (Tg), a germline-null mutation of IGFBP-3, or both. Compared with wild-type (BP3(+/+)) mice, mice carrying heterozygous (BP3(+/-)) or homozygous (BP3(-/-)) deletion of IGFBP-3 alleles exhibited decreases in circulating IGFBP-3 and IGF-I. Unexpectedly, IGF(Tg) mice with 50% of physiological IGFBP-3 (BP3(+/-); IGF(Tg)) showed higher levels of pIGF-IR/IR and a greater degree of spontaneous or tobacco carcinogen [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone]-induced lung tumor development and progression than did the IGF(Tg) mice with normal (BP3(+/+;) IGF(Tg)) or homozygous deletion of IGFBP-3 (BP3(-/-); IGF(Tg)). These data show that IGF-I is overexpressed in NSCLC, leading to activation of IGF-IR, and that IGFBP-3, depending on its expression level, either inhibits or potentiates IGF-I actions in lung carcinogenesis.

IGFBP-3 can either inhibit or enhance EGF-mediated growth of breast epithelial cells dependent upon the presence of fibronectin

Progression of breast cancer is associated with remodeling of the extracellular matrix, often involving a switch from estrogen dependence to a dependence on EGF receptor (EGFR)/HER-2 and is accompanied by increased expression of the main binding protein for insulin-like growth factors (IGFBP-3). We have examined the effects of IGFBP-3 on EGF responses of breast epithelial cells in the context of changes in the extracellular matrix. On plastic and laminin with MCF-10A normal breast epithelial cells, EGF and IGFBP-3 each increased cell growth and together produced a synergistic response, whereas with T47D breast cancer cells IGFBP-3 alone had no effect, but the ability of EGF to increase cell proliferation was markedly inhibited in the presence of IGFBP-3. In contrast on fibronectin with MCF-10A cells, IGFBP-3 alone inhibited cell growth and blocked EGF-induced proliferation. With the cancer cells, IGFBP-3 alone had no effect but enhanced the EGF-induced increase in cell growth. The insulin-like growth factor-independent effects of IGFBP-3 alone on cell proliferation were completely abrogated in the presence of an EGFR, tyrosine kinase inhibitor, Iressa. Although IGFBP-3 did not affect EGFR phosphorylation [Tyr(1068)], it was found to modulate receptor internalization and was associated with activation of Rho and subsequent changes in MAPK phosphorylation. The levels of fibronectin and IGFBP-3 within breast tumors may determine their dependence on EGFR and their response to therapies targeting this receptor.

Insulin-like growth factor binding protein-3 gene methylation and protein expression in gastric adenocarcinoma

OBJECTIVE

The aim of this study was to evaluate IGFBP-3 protein expression, its correlation with gene promoter methylation pattern in gastric carcinogenesis and with clinicopathological characteristics.

DESIGN

Forty-three normal gastric mucosa and 94 adenocarcinoma samples were investigated through methylation specific PCR, after bisulfite modification. Immunohistochemistry was analyzed using peroxidase in 54 gastric cancer and 20 normal gastric mucosa samples.

RESULTS

IGFBP-3 expression was higher in tumor samples than in normal mucosa (p<0.0001). Intestinal type presented a higher frequency of protein expression than diffuse type (p=0.0412). Methylation frequency of IGFBP-3 promoter in gastric samples revealed, respectively, 95.7% and 97.7% in neoplastic and non-neoplastic samples. The frequency of IGFBP-3 methylation did not differ between tumor and normal samples (95.7% versus 97.7%, p=0.7810). We did not observe a significant correlation between IGFBP-3 promoter methylation and protein expression.

CONCLUSION

In summary, our study did not observe any influence of IGFBP-3 promoter methylation on protein expression. Moreover we propose that IGFBP-3 immunostaining in gastric tissue may be a useful marker for malignancy.

IGFBP2 and IGFBP3 protein expressions in human breast cancer: association with hormonal factors and obesity

PURPOSE

The insulin-like growth factor (IGF) signaling system is involved in breast cancer initiation and progression. The prognostic relevance of tumor expression patterns of IGFI-related proteins remains poorly understood. This study associates the expression of selected IGF proteins with breast tumor and patient characteristics.

EXPERIMENTAL DESIGN

IGFI, IGFI receptor, IGF-binding protein (IGFBP)2, and IGFBP3 expression was measured in 855 primary breast carcinomas by immunohistochemistry using tissue microarrays. We investigated the association of tumor and nodal stage, grade, hormone receptor status, HER2 gene amplification, menopausal status, body mass index, and survival with IGF protein expression.

RESULTS

In contrast to IGFI, the expression of IGFI receptor, IGFBP2, and IGFBP3 was associated with estrogen receptor status. In addition, IGFBP3 was positively correlated with body mass index and premenopausal status. Importantly, IGFBP2 was an independent and positive predictor of overall survival (hazard ratio, 0.48; 95% confidence interval, 0.24-0.95; P = 0.04). There was a weak suggestion for IGFBP2 and overweight to modify each other's effect on survival.

CONCLUSIONS

According to these results, which need confirmation in larger patient series, the prognostic relevance of IGFBP2 and IGFBP3 protein expressions in breast cancer may depend on the hormonal context and body weight.

Effects of endogenous insulin-like growth factor binding protein-3 on cell cycle regulation in breast cancer cells

High tissue insulin-like growth factor binding protein-3 (IGFBP-3) expression in breast cancers is associated in some studies with rapid growth and poor outcome. This study examined the effects of endogenous IGFBP-3 in Hs578T breast cancer cells, which are IGF-unresponsive and grow aggressively despite relatively high IGFBP-3 expression. IGFBP-3 downregulation using siRNA was associated with increases in DNA synthesis, the percentage of cells in S phase and viable cell numbers, accompanied by increases in cyclins A and D1, a decrease in p27 expression, and increased phosphorylation of retinoblastoma (Rb) on Ser795. Downregulation of IGFBP-3 inhibited extracellular signal-regulated kinase (ERK) activation and cell migration in a monolayer wound healing assay. These results indicate that endogenous IGFBP-3 is anti-proliferative and pro-migratory in Hs578T cells and that these effects are IGF-independent. Poor outcome in breast tumours expressing high levels of IGFBP-3 may be due to the effects of IGFBP-3 on cell migration rather than cell growth.

Insulin-like growth factor binding protein-3 has dual effects on gastrointestinal stromal tumor cell viability and sensitivity to the anti-tumor effects of imatinib mesylate in vitro

Background

Imatinib mesylate has significantly improved survival and quality of life of patients with gastrointestinal stromal tumors (GISTs). However, the molecular mechanism through which imatinib exerts its anti-tumor effects is not clear. Previously, we found up-regulation of insulin-like growth factor binding protein-3 (IGFBP3) expression in imatinib-responsive GIST cells and tumor samples. Because IGFBP3 regulates cell proliferation and survival and mediates the anti-tumor effects of a number of anti-cancer agents through both IGF-dependent and IGF-independent mechanisms, we hypothesized that IGFBP3 mediates GIST cell response to imatinib. To test this hypothesis, we manipulated IGFBP3 levels in two imatinib-responsive GIST cell lines and observed cell viability after drug treatment.

Results

In the GIST882 cell line, imatinib treatment induced endogenous IGFBP3 expression, and IGFBP3 down-modulation by neutralization or RNA interference resulted in partial resistance to imatinib. In contrast, IGFBP3 overexpression in GIST-T1, which had no detectable endogenous IGFBP3 expression after imatinib, had no effect on imatinib-induced loss of viability. Furthermore, both the loss of IGFBP3 in GIST882 cells and the overexpression of IGFBP3 in GIST-T1 cells was cytotoxic, demonstrating that IGFBP3 has opposing effects on GIST cell viability.

Conclusion

This data demonstrates that IGFBP3 has dual, opposing roles in modulating GIST cell viability and response to imatinib in vitro. These preliminary findings suggest that there may be some clinical benefits to IGFBP3 therapy in GIST patients, but further studies are needed to better characterize the functions of IGFBP3 in GIST.

Potentiation of growth factor signaling by insulin-like growth factor-binding protein-3 in breast epithelial cells requires sphingosine kinase activity

We have investigated the mechanism underlying potentiation of epidermal growth factor receptor (EGFR) and type 1 insulin-like growth factor receptor (IGFR1) signaling by IGF-binding protein-3 (IGFBP-3) in MCF-10A breast epithelial cells, focusing on a possible involvement of the sphingosine kinase (SphK) system. IGFBP-3 potentiated EGF-stimulated EGF receptor activation and DNA synthesis, and this was blocked by inhibitors of SphK activity or small interference RNA-mediated silencing of SphK1, but not SphK2, expression. Similarly, IGFR1 phosphorylation and DNA synthesis stimulated by LR3-IGF-I (an IGF-I analog not bound by IGFBP-3), were enhanced by IGFBP-3, and this was blocked by SphK1 silencing. SphK1 expression and activity were stimulated by IGFBP-3 approximately 2-fold over 24 h. Silencing of sphingosine 1-phosphate receptor 1 (S1P1) or S1P3, but not S1P2, abolished the effect of IGFBP-3 on EGF-stimulated EGFR activation. The effects of IGFBP-3 could be reproduced with exogenous S1P or medium conditioned by cells treated with IGFBP-3, and this was also blocked by inhibition of S1P1 and S1P3. These data indicate that potentiation of growth factor signaling by IGFBP-3 in MCF-10A cells requires SphK1 activity and S1P1/S1P3, suggesting that S1P, the product of SphK activity and ligand for S1P1 and S1P3, is the "missing link" mediating IGF and EGFR transactivation and cell growth stimulation by IGFBP-3.

DNA copy number variation and gene expression analyses reveal the implication of specific oncogenes and genes in GBM

To understand the pathogenesis of glioblastoma multiforme (GBM) we used high-resolution comparative genomic hybridization arrays and gene expression microarrays to identify DNA copy number alterations and gene expression changes in comparable sets of GBM samples. Gains were detected at chromosomes 1, 2, 7, 9, 12, 19, and 20 and losses at 6, 9, and 10. Gene expression analyses identified specific genes overexpressed in GBM mapping at amplified chromosomal regions. Among these genes we found genes involved in angiogenesis, extracellular matrix remodeling and several oncogenes. DNA copy number analysis along with gene expression profiles provides a powerful strategy to understand tumor progression and identification of genes involved in GBM pathogenesis.

IGF binding proteins (IGFBPs) and regulation of breast cancer biology

The IGFBP family comprises six proteins with high affinity for the IGFs. Changes in the balance of the components of the IGF system may contribute to the progression of breast cancer. In tumours the abundance of IGFBPs relates to the estrogen receptor status and their production in the breast is controlled by hormones, principally estrogen and progesterone. Important interactions occur between IGFBPs and key growth regulators such as TGF-beta, PTEN and EGF which are reviewed. The conflicting observations between the effects of IGFBPs on the risk of breast cancer, in particular IGFBP-3, obtained from epidemiology studies in comparison to in vivo observations are highlighted and potential explanations provided. The functional activity of IGFBPs can also be affected by proteolysis, phosphorylation and glycosylation and the implications of these are described. The IGFs are generally present at levels far in excess of that required for maximal receptor stimulation, and the IGFBPs are critical regulators of their cellular actions. IGFBPs can affect cell function in an IGF-dependent or independent manner. The key mechanisms underlying the intrinsic actions of the IGFBPs are still in debate. IGF bioactivity locally in the breast is influenced not only by local tissue expression and regulation of IGFs, IGFBPs and IGFBP proteases, but also by these factors delivered from the circulation. Finally, the therapeutic potential of IGFBPs-2 and -3 are considered together with key questions that still need to be addressed.

IGFBP3 suppresses retinopathy through suppression of oxygen-induced vessel loss and promotion of vascular regrowth

Vessel loss precipitates many diseases. In particular, vessel loss resulting in hypoxia induces retinal neovascularization in diabetic retinopathy and in retinopathy of prematurity (ROP), major causes of blindness. Here we define insulin-like growth factor binding protein-3 (IGFBP3) as a new modulator of vascular survival and regrowth in oxygen-induced retinopathy. In IGFBP3-deficient mice, there was a dose-dependent increase in oxygen-induced retinal vessel loss. Subsequent to oxygen-induced retinal vessel loss, Igfbp3(-/-) mice had a 31% decrease in retinal vessel regrowth versus controls after returning to room air. No difference in serum insulin-like growth factor 1 (IGF1) levels was observed among groups. Wild-type mice treated with exogenous IGFBP3 had a significant increase in vessel regrowth. This correlated with a 30% increase in endothelial progenitor cells in the retina at postnatal day 15, indicating that IGFBP3 could be serving as a progenitor cell chemoattractant. In a prospective clinical study, we measured IGFBP3 (and IGF1) plasma levels weekly and examined retinas in all premature infants born at gestational ages <32 weeks at high risk for ROP. The mean level of IGFBP3 at 30-35 weeks postmenstrual age (PMA) for infants with proliferative ROP (ROP stages 3>, n = 13) was 802 microg/liter, and for infants with no ROP (ROP stage 0, n = 38) the mean level was 974 microg/liter (P < 0.03). These results suggest that IGFBP3, acting independently of IGF1, helps to prevent oxygen-induced vessel loss and to promote vascular regrowth after vascular destruction in vivo in a dose-dependent manner, resulting in less retinal neovascularization.

IGFBP3 mRNA expression in benign and malignant breast tumors

Introduction

Most previous studies have focused on evaluating the association between circulating insulin-like growth factor binding protein 3 (IGFBP-3) levels and breast cancer risk. Emerging evidence over the past few years suggests that IGFBP-3 may act directly on mammary epithelial cells.

Methods

To understand the role of IGFBP-3 in breast tumorigenesis, we investigated IGFBP3 mRNA expression levels in benign and malignant breast tumors and their adjacent normal tissues using real-time quantitative PCR.

Results

Cancer tissues had significantly lower IGFBP3 expression than benign tumor tissues (p < 0.001). IGFBP3 expressions in both tumor and adjacent tissues were higher in patients who had proliferative benign tumors than in those who had non-proliferative benign tumors. Among patients with benign breast disease, IGFBP3 expression in the tumor was significantly higher than that in their adjacent normal tissue. There were no apparent associations of IGFBP3 expression in cancer tissues with either overall survival or disease-free survival in a cohort of 521 patients with breast cancer.

Conclusion

Our findings suggest that the expression level of IGFBP3 in breast tissues may be involved in breast tumorigenesis.

Expression of insulin-like growth factor binding protein-2 by MCF-7 breast cancer cells is regulated through the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway

IGF binding protein-2 (IGFBP-2) has been implicated in the development and spread of a number of tumor types, and its abrogation in experimental models of cancer is associated with decreased tumor growth. This suggests that targeted inhibition of IGFBP-2 expression in some cancers may have therapeutic benefit. In this study, we investigated signaling pathways involved in extracellular IGFBP-2 expression in an IGF- and estrogen-responsive breast cancer cell line, MCF-7. IGFBP-2 was present at approximately 150 ng per 10(6) cells in serum-free MCF-7-conditioned medium and constituted the predominant IGFBP. Inhibition of the phosphatidylinositol 3-kinase signaling pathway using LY294002, or the downstream signaling intermediate mammalian target of rapamycin using rapamycin, markedly reduced IGFBP-2 in conditioned medium to approximately 25% of untreated levels (P < 0.001); there was no effect of inhibition of p38 MAPK, and an inhibitor of p44/42 MAPK activation, PD98059, caused only a slight reduction in extracellular IGFBP-2. IGFBP-2 levels were increased 25-30% by estradiol, whereas IGF-I (100 ng/ml) increased IGFBP-2 levels 2-fold (P < 0.001) by a type 1 IGF receptor (IGFR1)-dependent mechanism. Estradiol enhanced the effect of IGF-I on IGFBP-2 levels, and this was associated with increased phosphorylation of IGFR1. Basal, IGF-, or estradiol-stimulated IGFBP-2 was abrogated by LY294002 and rapamycin and an inhibitor of IGFR1 tyrosine kinase activity, AG1024. Modulation of intracellular hypoxia-inducible factor-1alpha had no effect on IGFBP-2 expression. These findings indicate that IGFBP-2 is regulated predominantly through the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin pathway, the target of a number of anticancer agents currently in clinical trial and use.

Inhibition of cell proliferation, induction of apoptosis, reactivation of DLC1, and modulation of other gene expression by dietary flavone in breast cancer cell lines

BACKGROUND

Dietary flavone was previously shown to increase the expression of deleted in liver cancer-1 gene (DLC-1) in HT-29 colon carcinoma cell line [Herzog A, Kindermann B, Doring F, Daniel H, Wenzel U. Pleiotropic molecular effects of the pro-apoptotic dietary constituent flavone in human colon cancer cells identified by protein and mRNA expression profiling. Proteomics 2004;4:2455-64]. DLC-1 that encodes a Rho GTPase-activating protein, functions as a tumor suppressor gene and is frequently inactivated or down-regulated in several common cancers. Restoration of DLC-1 expression suppresses in vitro tumor cells proliferation and tumorigenicity in vivo.

METHODS

Here, the effect of flavone was examined in several DLC-1-deficient cell lines derived from different types human cancer using assays for cell proliferation, gene expression and transfer.

RESULTS

We show that exposure to 150 microM flavone increased DLC1 expression in breast but not in liver or prostate carcinoma cells or a nonmalignant breast epithelial cell line. Flavone restored the expression of DLC1 in the breast carcinoma cell lines MDA-MB-468, MDA-MB-361, and BT20 as well as in the colon carcinoma cell line HT-29 all of which are DLC-1-negative due to promoter hypermethylation. We further show that flavone inhibited cell proliferation, induced cell cycle arrest at G(2)-M, increased p21(Waf1) gene expression, and caused apoptosis. Microarray analysis of these aggressive and metastatic breast carcinoma cells revealed 29 flavone-responsive genes, among which the DNA damage-inducible GADD genes were up-regulated and the proto-oncogene STMN1 and IGFBP3 were down-regulated.

CONCLUSIONS

Flavone-mediated alterations of genes that regulate tumor cell proliferation, cell cycle, and apoptosis contribute to chemopreventive and antitumoral effects of flavone. Alone or in combination with demethylating agents, flavone may be an effective adjunct to chemotherapy in preventing breast cancer metastasis.

Aberrant promoter methylation of insulin-like growth factor binding protein-3 gene in human cancers

Insulin-like growth factor binding protein-3 (IGFBP-3) is postulated to be a mediator of growth suppression signals. Here, we examined the methylation status of IGFBP-3 to correlate to clinicopathological factors in human cancers. The methylation status of IGFBP-3 was determined by bisulfite DNA sequencing and was correlated with expression semi-quantified by real-time RT-PCR to develop a methylation-specific PCR (MSP) assay for IGFBP-3. Using the MSP assay, we examined the methylation status of IGFBP-3 in gastric cancer (GC), colorectal cancer (CRC), breast cancer (BC) and malignant mesothelioma (MM). IGFBP-3 methylation was detected in 6 of 13 (46%) and 16 of 24 (67%) GC cell lines and tumors, respectively; 4 of 8 (50%) and 15 of 26 (58%) CRC cell lines and tumors, respectively; 3 of 11 (27%) and 7 of 39 (18%) BC cell lines and tumors, respectively and 1 of 5 (20%) and 18 of 56 (32%) MM cell lines and tumors, respectively. Interestingly, the methylation status of MM specimens from Japanese patients (75%, 12 out of 16 patients) was significantly higher than those from the USA (15%, 6 out of 40 patients) (p < 0.0001), suggesting the presence of ethnic differences in the IGFBP-3 methylation status. We also found that IGFBP-3 methylation was preferentially present in GCs arising in the lower-third of the stomach (p = 0.079). In summary, our results showed that IGFBP-3 methylation played an important role in the silencing of its expression, suggesting that IGFBP-3 may act as a tumor suppressor gene in several human cancers examined.

IGF1 and IGFBP3 tagging polymorphisms are associated with circulating levels of IGF1, IGFBP3 and risk of breast cancer

Experimental and observational studies in humans and animals suggest that insulin-like growth factor 1 (IGF1) and its principal binding protein, IGFBP3, may influence breast cancer susceptibility. We have examined the association of nine and four single nucleotide polymorphisms (SNPs) in the IGF1 gene and in the IGFBP3 genes, respectively, with circulating levels of their gene products in a population-based study of 600 middle-aged men and women, and in a breast cancer case-control study, comprised 4647 cases and 4564 controls. All study participants are from the East Anglian region of UK. SNPs were specifically chosen to tag all other known SNPs in each gene. Several SNPs in each gene are associated both with circulating levels of their respective proteins and with risk of breast cancer. In particular, the c allele of IGF1 SNPrs1520220 is associated with increased circulating IGF1 (r2=2.1%, P-trend=0.003) in females and an increased risk of breast cancer: odds ratio (OR) (cc/gg)=1.41; 95% confidence intervals (95% CI) 1.11-1.79, P-trend=0.03. The a allele of IGFBP3 SNP rs2854744 is associated with increased circulating IGFBP3 (r2=9.7%, P<10(-9)) and a decreased risk of breast cancer: OR (aa/cc)=0.87; 95% CI 0.77-0.99, P=0.03. Our data indicate that common variants in the IGF1 and IGFBP3 genes are associated with differences in circulating levels of IGF1 and IGFBP3 and with breast cancer risk. More specifically and consistent with experimental models, our data suggest that higher IGF1 levels may increase the risk of breast cancer but higher IGFBP3 levels may be protective.

Expression of insulin-like growth factor 1 receptor in primary breast cancer: immunohistochemical analysis

Insulin-like growth factor-1 receptor (IGF-1R) has been implicated in regulation in tumor growth. The results of previous studies performed by radioimmunoassay are conflicting, and the prognostic significance of IGF-1R expression in primary breast cancer is still controversial. IGF-1R expression was evaluated in formalin-fixed, paraffin-embedded tissue of 210 primary breast cancer patients by using anti-IGF-1R antibody. The clinicopathologic variables and 5-year disease-free survival were studied, and their correlations between IGF-1R expressions were investigated. IGF-1R overexpression was observed in 43.8% of tumors. IGF-1R overexpression had no correlation with prognosis or with other clinicopathologic parameters, such as age, tumor size, nodal status, histologic grade, hormone receptor status, and human epidermal growth factor 2 status. Though its prognostic value in breast cancer is limited, immunohistochemical evaluation of IGF-1R by using this monoclonal antibody may be useful in translational research using archived material.

Functional promoter upstream p53 regulatory sequence of IGFBP3 that is silenced by tumor specific methylation

BACKGROUND

Insulin-like growth factor binding protein (IGFBP)-3 functions as a carrier of insulin-like growth factors (IGFs) in circulation and a mediator of the growth suppression signal in cells. There are two reported p53 regulatory regions in the IGFBP3 gene; one upstream of the promoter and one intronic. We previously reported a hot spot of promoter hypermethylation of IGFBP-3 in human hepatocellular carcinomas and derivative cell lines. As the hot spot locates at the putative upstream p53 consensus sequences, these p53 consensus sequences are really functional is a question to be answered.

METHODS

In this study, we examined the p53 consensus sequences upstream of the IGFBP-3 promoter for the p53 induced expression of IGFBP-3. Deletion, mutagenesis, and methylation constructs of IGFBP-3 promoter were assessed in the human hepatoblastoma cell line HepG2 for promoter activity.

RESULTS

Deletions and mutations of these sequences completely abolished the expression of IGFBP-3 in the presence of p53 overexpression. In vitro methylation of these p53 consensus sequences also suppressed IGFBP-3 expression. In contrast, the expression of IGFBP-3 was not affected in the absence of p53 overexpression. Further, we observed by electrophoresis mobility shift assay that p53 binding to the promoter region was diminished when methylated.

CONCLUSION

From these observations, we conclude that four out of eleven p53 consensus sequences upstream of the IGFBP-3 promoter are essential for the p53 induced expression of IGFBP-3, and hypermethylation of these sequences selectively suppresses p53 induced IGFBP-3 expression in HepG2 cells.

Insulin-like growth factor (IGF)-I and IGF-II serum concentrations in patients with benign and malignant breast lesions: free IGF-II is correlated with breast cancer size

PURPOSE

Insulin-like growth factors (IGFs) are potent mitogens for breast cancer cells in vitro, and elevated IGF-I serum levels are a risk factor for breast malignancies. This study evaluated IGF-I and IGF-II serum levels in healthy women and in patients with benign and malignant breast lesions and correlated them with tumor size.

EXPERIMENTAL DESIGN

Serum levels of the total and unbound fractions of IGF-I and IGF-II were analyzed in 65 patients with benign and malignant breast lesions and in 38 women without breast disease. ELISAs were used to detect serum IGF levels, with (total IGF) or without (free IGF) prior acid-ethanol extraction.

RESULTS

Total IGF-I serum concentrations were lower in healthy women than in breast cancer patients (P < 0.001) or patients with benign breast lesions (P = 0.010), but no differences were observed in free IGF-I levels. Conversely, healthy women had higher serum levels of free IGF-II than women with breast lesions (P = 0.003), and the free/total IGF-II ratio was significantly reduced in patients with breast disease (P = 0.001). Although IGF-I or IGF-II serum concentrations of breast cancer patients were similar to those of patients with benign lesions, the size of a malignant tumor was correlated to the ratio free/total IGF-II (P = 0.002).

CONCLUSIONS

Malignant breast tumors cannot be distinguished from benign breast lesions by systemic IGF serum levels. However, women with breast lesions have decreased IGF-II concentrations, and free IGF-II levels are clearly correlated to the size of a breast cancer, indicating an involvement in tumor growth.

Immunohistochemical expression of insulin-like growth factor binding protein-3 in invasive breast cancers and ductal carcinoma in situ: implications for clinicopathology and patient outcome

INTRODUCTION

Insulin-like growth factor binding protein-3 (IGFBP-3) differentially modulates breast epithelial cell growth through insulin-like growth factor (IGF)-dependent and IGF-independent pathways and is a direct (IGF-independent) growth inhibitor as well as a mitogen that potentiates EGF (epidermal growth factor) and interacts with HER-2. Previously, high IGFBP-3 levels in breast cancers have been determined by enzyme-linked immunosorbent assay and immunoradiometric assay methods. In vitro, IGFBP-3's mechanisms of action may involve cell membrane binding and nuclear translocation. To evaluate tumour-specific IGFBP-3 expression and its subcellular localisation, this study examined immunohistochemical IGFBP-3 expression in a series of invasive ductal breast cancers (IDCs) with synchronous ductal carcinomas in situ (DCIS) in relation to clinicopathological variables and patient outcome.

METHODS

Immunohistochemical expression of IGFBP-3 was evaluated with the sheep polyclonal antiserum (developed in house) with staining performed as described previously.

RESULTS

IGFBP-3 was evaluable in 101 patients with a variable pattern of cytoplasmic expression (positivity of 1+/2+ score) in 85% of invasive and 90% of DCIS components. Strong (2+) IGFBP-3 expression was evident in 32 IDCs and 40 cases of DCIS. A minority of invasive tumours (15%) and DCIS (10%) lacked IGFBP-3 expression. Nuclear IGFBP-3 expression was not detectable in either invasive cancers or DCIS, with a consistent similarity in IGFBP-3 immunoreactivity in IDCs and DCIS. Positive IGFBP-3 expression showed a possible trend in association with increased proliferation (P = 0.096), oestrogen receptor (ER) negativity (P = 0.06) and HER-2 overexpression (P = 0.065) in invasive tumours and a strong association with ER negativity (P = 0.037) in DCIS. Although IGFBP-3 expression was not an independent prognosticator, IGFBP-3-positive breast cancers may have shorter disease-free and overall survivals, although these did not reach statistical significance.

CONCLUSIONS

Increased breast epithelial IGFBP-3 expression is a feature of tumorigenesis with cytoplasmic immunoreactivity in the absence of significant nuclear localisation in IDCs and DCIS. There are trends between high levels of IGFBP-3 and poor prognostic features, suggesting that IGFBP-3 is a potential mitogen. IGFBP-3 is not an independent prognosticator for overall survival or disease-free survival, to reflect its dual effects on breast cancer growth regulated by complex pathways in vivo that may relate to its interactions with other growth factors.

Insulin-like growth factor binding protein-3 expression is associated with growth stimulation of T47D human breast cancer cells: the role of altered epidermal growth factor signaling

IGF binding protein (IGFBP)-3 has antiproliferative and proapoptotic effects on the growth of human breast cancer cells in vitro. However, clinical studies suggest that high levels of IGFBP-3 in breast tumor tissue are associated with large, highly proliferative tumors. In this study, we examined the effects of stable transfection with human IGFBP-3 cDNA on the growth of T47D human breast cancer cells in vitro and in vivo. Expression of IGFBP-3 initially inhibited the growth of T47D in vitro but was associated with enhanced growth in vivo. Furthermore, IGFBP-3-expressing cells in vitro became growth stimulated at higher passages post transfection, suggesting breast cancer cells may switch their response to IGFBP-3 with increasing tumorigenicity. These stimulatory effects observed in IGFBP-3-expressing cells were associated with an enhanced responsiveness to the proliferative effects of epidermal growth factor (EGF). When EGF receptor (EGFR) kinase activity was blocked using PD153035, high passage IGFBP-3 transfectants were growth inhibited compared with controls treated with inhibitor. These findings suggest that the interaction between IGFBP-3 and the EGFR system is central to whether IGFBP-3 acts as a growth stimulator or inhibitor in breast cancer cells and that therapies targeting EGFR may have increased efficacy in breast tumors expressing high levels of IGFBP-3.

The insulin-like growth factor system in advanced breast cancer

Despite improvements in therapy, the prognosis for advanced breast cancer is poor and a search for new treatment targets and key regulators of tumour growth is warranted. Extensive data are available on the importance of the insulin-like growth factor (IGF) system in growth regulation of breast cancer cell lines in vitro, indicating that the IGF-I receptor (IGF-IR), IGF-I (and IGF-II) function as survival factors, while IGF binding protein (IGFBP)-3 may act as a growth inhibitor. There is a tight link between the growth regulatory pathways of IGFs and oestrogens in oestrogen-receptor(OR)-positive breast cancer cells. In vivo studies indicate a role of IGF-I and IGF-IR in breast cancer development. However, the importance of the IGF system in metastatic and highly aggressive breast tumours in vivo is not clear, and therapeutic strategies designed to interrupt IGF signalling have not yet proved to be an effective treatment modality in patients with metastatic breast cancer.

Insulin-like growth factor binding protein-3 prevents retinoid receptor heterodimerization: implications for retinoic acid-sensitivity in human breast cancer cells

Insulin-like growth factor binding protein-3 (IGFBP-3) has both IGF-dependent and -independent effects on cell growth, which are frequently growth-inhibitory. Interestingly, the development of a more aggressive phenotype in breast cancer cells (BCCs) correlates positively with elevated expression of IGFBP-3 and is often associated with all-trans-retinoic acid (atRA)-resistance. IGFBP-3 was previously demonstrated to interact directly with retinoid X receptor (RXR). In this study we have shown that IGFBP-5 also interacts with RXR and that both IGFBPs interact with retinoic acid receptor (RAR). To investigate whether the presence of IGFBP-3 regulates breast cancer cell responsiveness to atRA, we immuno-neutralized the IGFBP-3 expressed by the atRA-resistant Hs578T and MDA-MB-231 BCCs (which express IGFBP-3 constitutively) and showed that they become more sensitive to the growth-inhibitory effects of atRA. Similarly, in Hs578T cells expressing a reporter gene under the control of an RAR response element (RARE), depletion of IGFBP-3 resulted in the induction of reporter gene expression in response to atRA. In investigating possible mechanisms for IGFBP-3 regulation of atRA-sensitivity, we found that IGFBP-3 blocked the formation of RAR:RXR heterodimers and disrupted the ligand-inducible receptor complex. Thus, IGFBP-3 has the potential to reduce the RARE-mediated transactivation of target genes and modulate the atRA-response in BCCs.