Expression of a protease-resistant insulin-like growth factor-binding protein-4 inhibits tumour growth in a murine model of breast cancer

Insulin-like growth factor family and prostate cancer: new insights and emerging opportunities

Prostate cancer is the second most commonly diagnosed cancer in men. The mammalian insulin-like growth factor (IGF) family is made up of three ligands (IGF-I, IGF-II, and insulin), three receptors (IGF-I receptor (IGF-1R), insulin receptor (IR), and IGF-II receptor (IGF-2R)), and six IGF-binding proteins (IGFBPs). IGF-I and IGF-II were identified as potent mitogens and were previously associated with an increased risk of cancer development including prostate cancer. Several reports showed controversy about the expression of the IGF family and their connection to prostate cancer risk due to the high degree of heterogeneity among prostate tumors, sampling bias, and evaluation techniques. Despite that, it is clear that several IGF family members play a role in prostate cancer development, metastasis, and androgen-independent progression. In this review, we aim to expand our understanding of prostate tumorigenesis and regulation through the IGF system. Further understanding of the role of IGF signaling in PCa shows promise and needs to be considered in the context of a comprehensive treatment strategy.

The role of pregnancy associated plasma protein-A in triple negative breast cancer: a promising target for achieving clinical benefits

Pregnancy associated plasma protein-A (PAPP-A) plays an integral role in breast cancer (BC), especially triple negative breast cancer (TNBC). This subtype accounts for the most aggressive BC, possesses high tumor heterogeneity, is least responsive to standard treatments and has the poorest clinical outcomes. There is a critical need to address the lack of effective targeted therapeutic options available. PAPP-A is a protein that is highly elevated during pregnancy. Frequently, higher PAPP-A expression is detected in tumors than in healthy tissues. The increase in expression coincides with increased rates of aggressive cancers. In BC, PAPP-A has been demonstrated to play a role in tumor initiation, progression, metastasis including epithelial-mesenchymal transition (EMT), as well as acting as a biomarker for predicting patient outcomes. In this review, we present the role of PAPP-A, with specific focus on TNBC. The structure and function of PAPP-A, belonging to the pappalysin subfamily, and its proteolytic activity are assessed. We highlight the link of BC and PAPP-A with respect to the IGFBP/IGF axis, EMT, the window of susceptibility and the impact of pregnancy. Importantly, the relevance of PAPP-A as a TNBC clinical marker is reviewed and its influence on immune-related pathways are explored. The relationship and mechanisms involving PAPP-A reveal the potential for more treatment options that can lead to successful immunotherapeutic targets and the ability to assist with better predicting clinical outcomes in TNBC.

IGF-dependent dynamic modulation of a protease cleavage site in the intrinsically disordered linker domain of human IGFBP2

Functional regulation via conformational dynamics is well known in structured proteins but less well characterized in intrinsically disordered proteins and their complexes. Using NMR spectroscopy, we have identified a dynamic regulatory mechanism in the human insulin-like growth factor (IGF) system involving the central, intrinsically disordered linker domain of human IGF-binding protein-2 (hIGFBP2). The bioavailability of IGFs is regulated by the proteolysis of IGF-binding proteins. In the case of hIGFBP2, the linker domain (L-hIGFBP2) retains its intrinsic disorder upon binding IGF-1, but its dynamics are significantly altered, both in the IGF binding region and distantly located protease cleavage sites. The increase in flexibility of the linker domain upon IGF-1 binding may explain the IGF-dependent modulation of proteolysis of IGFBP2 in this domain. As IGF homeostasis is important for cell growth and function, and its dysregulation is a key contributor to several cancers, our findings open up new avenues for the design of IGFBP analogs inhibiting IGF-dependent tumors.

Statins inhibit proliferation and induce apoptosis in triple-negative breast cancer cells

TP53 (p53) is mutated in 80–90% of cases of triple-negative breast cancer (TNBC). Statins, which are widely used to treat elevated cholesterol, have recently been shown to degrade mutant p53 protein and exhibit anti-cancer activity. The aim of this work was to evaluate the potential of statins in the treatment of TNBC. The anti-proliferative effects of 2 widely used statins were investigated on a panel of 15 cell lines representing the different molecular subtypes of breast cancer. Significantly lower IC50 values were found in triple-negative (TN) than in non-TN cell lines (atorvastatin, p < 0.01; simvastatin p < 0.05) indicating greater sensitivity. Furthermore, cell lines containing mutant p53 were more responsive to both statins than cell lines expressing wild-type p53, suggesting that the mutational status of p53 is a potential predictive biomarker for statin response. In addition to inhibiting proliferation, simvastatin was also found to promote cell cycle arrest and induce apoptosis. Using an apoptosis array capable of detecting 43 apoptosis-associated proteins, a novel protein shown to be upregulated by simvastatin was the IGF-signalling modulator, IGBP4, a finding we confirmed by Western blotting. Finally, we found synergistic growth inhibition between simvastatin and the IGF-1R inhibitor, OSI-906 as well as between simvastatin and doxorubicin or docetaxel. Our work suggests repurposing of statins for clinical trials in patients with TNBC. Based on our findings, we suggest that these trials investigate statins in combination with either doxorubicin or docetaxel and include p53 mutational status as a potential predictive biomarker.

Low expression of IGFBP4 and TAGLN accelerate the poor overall survival of osteosarcoma

Osteosarcoma is a common malignant bone tumor characterized by the production of osteoid stroma by the tumor. However, effect of IGFBP4 and TAGLN on the survival of osteosarcoma is unclear. The GEO database was used to identify the differentially expressed genes (DEGs) between control samples and osteosarcoma. Genes for biological process (BP), cellular composition (CC), and molecular function (MF) were examined using DAVID, Metascape, and GSEA. GSE14359 and GSE36001 were downloaded in the GEO database. GEO2R was used to find DEGs between control samples and osteosarcoma. The cytoHubb also found the hub genes of IGFBP4 and TAGLN. The Kaplan–Meier method was used to analyze overall survival. A total of 134 patients with osteosarcoma were enrolled in this study. The RNA levels of IGFBP4 and TAGLN were evaluated by RT-qPCR. The correlation between IGFBP4 and TAGLN expression and their associations with clinical indicators were analyzed using Spearman's rho test and Pearson's Chi-squared test. Univariate and multivariate Cox regression analyses were used to determine the potential prognostic factors. And the animal model was used to verify the role of hub genes on the osteosarcoma by the RT-qPCR and immunofluorescence. Support Vector Machine (SVM) was performed to construct the correlation among the expression of IGFBP4, TAGLN, and osteosarcoma. Through bioinformatics, IGFBP4 and TAGLN were identified as the hub genes of osteosarcoma. And osteosarcoma patients with high expression levels of IGFBP4 (HR = 0.56, P = 0.013) and TAGLN (HR = 0.52, P = 0.012) had better overall survival times than those with low expression levels. The results showed that pathologic grade (P = 0.017), tumor metastasis (P < 0.001), and enneking stage (P < 0.001) were significantly correlated with IGFBP4. Also, pathologic grade (P = 0.002), tumor metastasis (P < 0.001), and enneking stage (P < 0.001) were significantly related to the TAGLN. Spearman’s correlation coefficient displayed that IGFBP4 were significantly correlated with the tumor metastasis (ρ = − 0.843, P < 0.001), enneking stage (ρ = − 0.500, P < 0.001), and TAGLN (ρ = 0.821, P < 0.001). IGFBP4 (HR = 0.252, 95% CI 0.122–0.517, P < 0.001) and TAGLN (HR = 0.155, 95% CI 0.089–0.269, P < 0.001) were significantly associated with overall survival. Based on the qPCR and immunofluorescence, IGFBP4 and TAGLN were down-regulated in the osteosarcoma tissue than the control group. And the SVM presented that there exists strong relationship among the expression of IGFBP4, TAGLN, and osteosarcoma. IGFBP4 and TAGLN may be attractive molecular targets for osteosarcoma, opening a new avenue for research into the disease.

Characterisation of the Stromal Microenvironment in Lobular Breast Cancer

Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer, and it exhibits a number of clinico-pathological characteristics distinct from the more common invasive ductal carcinoma (IDC). We set out to identify alterations in the tumor microenvironment (TME) of ILC. We used laser-capture microdissection to separate tumor epithelium from stroma in 23 ER + ILC primary tumors. Gene expression analysis identified 45 genes involved in regulation of the extracellular matrix (ECM) that were enriched in the non-immune stroma of ILC, but not in non-immune stroma from ER+ IDC or normal breast. Of these, 10 were expressed in cancer-associated fibroblasts (CAFs) and were increased in ILC compared to IDC in bulk gene expression datasets, with PAPPA and TIMP2 being associated with better survival in ILC but not IDC. PAPPA, a gene involved in IGF-1 signaling, was the most enriched in the stroma compared to the tumor epithelial compartment in ILC. Analysis of PAPPA- and IGF1-associated genes identified a paracrine signaling pathway, and active PAPP-A was shown to be secreted from primary CAFs. This is the first study to demonstrate molecular differences in the TME between ILC and IDC identifying differences in matrix organization and growth factor signaling pathways.

Circulating Insulin-Like Growth Factor 1-Related Biomarkers and Risk of Lethal Prostate Cancer

Background

Experimental and epidemiologic evidence supports the role of circulating insulin-like growth factor-1 (IGF-1) levels with the risk of prostate cancer. Most circulating IGF-1 is bound to specific binding proteins, and only about 5% circulates in a free form. We explored the relation of free IGF-1 and other components of the IGF system with lethal prostate cancer.

Methods

Using prospectively collected samples, we undertook a nested case-only analysis among 434 men with lethal prostate cancer and 524 men with indolent, nonlethal prostate cancer in the Physicians’ Health Study and the Health Professionals Follow-up Study. Prediagnostic plasma samples were assayed for free IGF-1 and total IGF-1, acid labile subunit, pregnancy-associated plasma protein A (PAPP-A), and intact and total IGF binding protein 4. We estimated odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for the associations between IGF-1–related biomarkers and lethal prostate cancer using unconditional logistic regression models adjusted for age, height, and body mass index.

Results

Men in the highest quartile of PAPP-A levels had 42% higher odds of lethal prostate cancer (pooled adjusted OR = 1.42, 95% CI = 1.04 to 1.92) compared with men in the lowest 3 quartiles. There were no statistically significant differences in the other plasma analytes. The positive association between PAPP-A and lethal prostate cancer was present among men with intact PTEN but not among those with tumor PTEN loss (2-sided P_interaction = .001).

Conclusions

Our study provides suggestive evidence that among men who later develop prostate cancer, higher plasma PAPP-A levels measured prior to diagnosis are associated with increased risk of lethal compared with indolent disease.

The Role of IGF/IGF-1R Signaling in Hepatocellular Carcinomas: Stemness-Related Properties and Drug Resistance

Insulin-like Growth Factor (IGF)/IGF-1 Receptor (IGF-1R) signaling is known to regulate stem cell pluripotency and differentiation to trigger cell proliferation, organ development, and tissue regeneration during embryonic development. Unbalanced IGF/IGF-1R signaling can promote cancer cell proliferation and activate cancer reprogramming in tumor tissues, especially in the liver. Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death, with a high incidence and mortality rate in Asia. Most patients with advanced HCC develop tyrosine kinase inhibitor (TKI)-refractoriness after receiving TKI treatment. Dysregulation of IGF/IGF-1R signaling in HCC may activate expression of cancer stemness that leads to TKI refractoriness and tumor recurrence. In this review, we summarize the evidence for dysregulated IGF/IGF-1R signaling especially in hepatitis B virus (HBV)-associated HCC. The regulation of cancer stemness expression and drug resistance will be highlighted. Current clinical treatments and potential therapies targeting IGF/IGF-1R signaling for the treatment of HCC will be discussed.

Discovery of a novel small-molecule inhibitor of Fam20C that induces apoptosis and inhibits migration in triple negative breast cancer

The family with sequence similarity 20, member C (Fam20C), a Golgi casein kinase, has been recently regarded as a potential therapeutic target for the treatment of triple negative breast cancer (TNBC). Lacking enzyme activity center has been becoming an obstacle to the development of small-molecule inhibitors of Fam20C. Herein, we combined in silico high-throughput screening with chemical synthesis methods to obtain a new small-molecule Fam20C inhibitor 3r, which exhibited desired anti-proliferative activities against MDA-MB-231 cells and also inhibited migration. Subsequently, the enzymatic assay, molecular docking, and molecular dynamics (MD) simulations were carried out for validating that 3r could bind to Fam20C. In addition, 3r was found to induce apoptosis via the mitochondrial pathway in MDA-MB-231 cells as well as to inhibit cell migration. Moreover, we demonstrated that 3r inhibited tumor growth in vivo and thereby having a good therapeutic potential on TNBC. Taken together, these results suggest that 3r may be a novel Fam20C inhibitor with anti-proliferative and apoptosis-inducing activities, which would shed light on discovering more small-molecule drugs for the future TNBC therapy.

Wnt signaling in breast cancer: biological mechanisms, challenges and opportunities

Wnt signaling is a highly conserved signaling pathway that plays a critical role in controlling embryonic and organ development, as well as cancer progression. Genome-wide sequencing and gene expression profile analyses have demonstrated that Wnt signaling is involved mainly in the processes of breast cancer proliferation and metastasis. The most recent studies have indicated that Wnt signaling is also crucial in breast cancer immune microenvironment regulation, stemness maintenance, therapeutic resistance, phenotype shaping, etc. Wnt/β-Catenin, Wnt-planar cell polarity (PCP), and Wnt-Ca2+ signaling are three well-established Wnt signaling pathways that share overlapping components and play different roles in breast cancer progression. In this review, we summarize the main findings concerning the relationship between Wnt signaling and breast cancer and provide an overview of existing mechanisms, challenges, and potential opportunities for advancing the therapy and diagnosis of breast cancer.

Aberrant pregnancy-associated plasma protein-A expression in breast cancers prognosticates clinical outcomes

Elevated levels of pregnancy-associated plasma protein-A (PAPP-A) have been implicated in the pathogenesis of various malignancies, including breast cancers. Breast cancer is one of the most frequent carcinomas and is the second most common cancer type detected in women of child-bearing age. Throughout pregnancy PAPP-A is produced and secreted by the placental syncytiotrophoblast cells; co-incidentally pregnancy-associated breast cancers often have an aggressive clinical course. The components of the PAPP-A/IGF axis was assessed in a panel of breast cancer cell lines. Using neutralising antibodies the impact of PAPP-A/IGF axis on cell motility was evaluated. PAPP-A was expressed in four of the twelve breast cancer cell lines tested. Blocking PAPP-A and IGFBP4 with neutralising antibodies significantly decreased motiliy of MDA-MB-231 cells. Upregulation of PAPP-A expression in breast tumours resulted in a trend towards worse overall survival. Notably, PAPP-A expression also positively correlated with epithelial-to-mesenchymal transition markers. In conclusion, these results indicate that PAPP-A plays an important role in breast cancer progression and it may be a promising therapeutic target in breast cancer.

IGF-binding proteins 3 and 4 are regulators of sprouting angiogenesis

PURPOSE

We have previously identified insulin-like growth factor 2 (IGF2) and insulin-like growth factor 1 receptor (IGF1R) as essential proteins for tip cell maintenance and sprouting angiogenesis. In this study, we aim to identify other IGF family members involved in endothelial sprouting angiogenesis.

METHODS

Effects on sprouting were analyzed in human umbilical vein endothelial cells (HUVECs) using the spheroid-based sprouting model, and were quantified as mean number of sprouts per spheroid and average sprout length. RNA silencing technology was used to knockdown gene expression. Recombinant forms of the ligands (IGF1 and IGF2, insulin) and the IGF-binding proteins (IGFBP) 3 and 4 were used to induce excess effects. Effects on the tip cell phenotype were analyzed by measuring the fraction of CD34⁺ tip cells using flow cytometry and immunohistochemistry in a 3D angiogenesis model. Experiments were performed in the presence and absence of serum.

RESULTS

Knockdown of IGF2 inhibited sprouting in HUVECs, in particular when cultured in the absence of serum, suggesting that components in serum influence the signaling of IGF2 in angiogenesis in vitro. We then determined the effects of IGFBP3 and IGFBP4, which are both present in serum, on IGF2-IGF1R signaling in sprouting angiogenesis in the absence of serum: knockdown of IGFBP3 significantly reduced sprouting angiogenesis, whereas knockdown of IGFBP4 resulted in increased sprouting angiogenesis in both flow cytometry analysis and immunohistochemical analysis of the 3D angiogenesis model. Other IGF family members except INSR did not affect IGF2-IGF1R signaling.

CONCLUSIONS

Serum components and IGF binding proteins regulate IGF2 effects on sprouting angiogenesis. Whereas IGFBP3 acts as co-factor for IGF2-IGF1R binding, IGFBP4 inhibits IGF2 signaling.

Role of stanniocalcin-1 in breast cancer

Breast cancer is a highly heterogeneous disease consisting of five disease subtypes with distinct histological characteristics, clinical behaviors and prognostic features. Stanniocalcin-1 (STC1) is a secreted glycoprotein hormone that has been demonstrated to regulate calcium and phosphate homeostasis. Mammalian STC1 is expressed in various tissues and is implicated in multiple physiological and pathophysiological processes. In addition, growing evidence has suggested that STC1 serves an oncogenic role in a number of different types of tumor. However, the role of STC1 in breast cancer is complex, considering that some studies have shown that it exerts an oncogenic role, whereas other studies have demonstrated the opposite. The aim of the present review article is to evaluate the currently available data on mammalian STC1 and discuss its potential roles in each subtype of breast cancer.

Insulin-like growth factor binding proteins and angiogenesis: from cancer to cardiovascular disease

Angiogenesis is a tightly regulated activity that is vital during embryonic development and for normal physiological repair processes and reproduction in healthy adults. Pathological angiogenesis is a driving force behind a variety of diseases including cancer and retinopathies, and inhibition of angiogenesis is a therapeutic option that has been the subject of much research, with several inhibitory agents now available for medical therapy. Conversely, therapeutic angiogenesis has been mooted as having significant potential in the treatment of ischemic conditions such as angina pectoris and peripheral arterial disease, but so far there has been less translation from lab to bedside. The insulin-like growth factor binding proteins (IGFBP) are a family of seven proteins essential for the binding and transport of the insulin-like growth factors (IGF). It is being increasingly recognised that IGFBPs have a significant role beyond simply modulating IGF activity, with evidence of both IGF dependent and independent actions through a variety of mechanisms. Moreover, the action of the IGFBPs can be stimulatory or inhibitory depending on the cell type and environment. Specifically the IGFBPs have been heavily implicated in angiogenesis, both pathological and physiological, and they have significant promise as targeted cell therapy agents for both pathological angiogenesis inhibition and therapeutic angiogenesis following ischemic injury. In this short review we will explore the current understanding of the individual impact of each IGFBP on angiogenesis, and the pathways through which these effects occur.

Serum Levels of Activins, Follistatins, and Growth Factors in Neoplasms of the Breast: A Case-Control Study

CONTEXT

Breast cancer is the most common malignancy in women. Noninvasive biomarkers are needed for its early diagnosis and/or prognosis.

OBJECTIVE

The aim of this case-control study was the comparison of serum activins, follistatins, and members of the IGF family levels in women with benign vs malignant breast neoplasms vs apparently healthy controls.

DESIGN AND PATIENTS

Women with breast benign (n = 100) or malignant tumors (n = 145) and disease-free controls (n = 100) were recruited. Women with breast cancer were subsequently subdivided into recently diagnosed/treatment-naive (n = 112) and chemotherapy-treated (n = 33). Anthropometric, demographic, biochemical, and histological data were recorded.

SETTING

A breast cancer clinic in Thessaloniki, Greece.

MAIN OUTCOME MEASURES

Serum levels of activin A, activin B, follistatin, follistatin-like (FSTL)-3, total IGF-1, total and intact insulin-like growth factor binding protein (IGFBP)-4 and pregnancy-associated plasma protein-A (PAPP-A) were measured with highly specific ELISA kits.

RESULTS

In adjusted comparisons, substantial differences in FSTL-3, total and intact IGFBP-4, PAPP-A, and total IGF-1 were observed between groups. In logistic regression analysis, primarily total IGFBP-4 levels were independently associated with the overall presence of breast malignancy. FSTL-3 was the only variable that could distinguish between a benign vs malignant breast mass. In linear regression analysis, FSTL-3 was independently associated with tumor size.

CONCLUSIONS

We showed that members of the IGF-1/IGFBP-4/PAPP-A axis and FSTL-3 may serve as surrogate markers in breast cancer. Future mechanistic and longitudinal studies and/or clinical trials are needed to explore the efficacy of these molecules as noninvasive biomarkers and their possible therapeutic potential in breast cancer.

Recombinant PAPP-A resistant insulin-like growth factor binding protein 4 (dBP4) inhibits angiogenesis and metastasis in a murine model of breast cancer

BACKGROUND

The Insulin-like growth factor (IGF) pathway plays a role in tumour development and progression. In vivo, IGF1 activity is regulated by the IGF binding proteins (IGFBPs). IGFBP4 inhibits the activity of IGF1 but proteolytic cleavage by pregnancy-associated plasma protein-A (PAPP-A) releases active IGF1. A modified IGFBP4, dBP4, which was resistant to PAPP-A cleavage but retained IGF1 binding capacity, was engineered, expressed in Human Embryonic Kidney (HEK) 293 cells and purified. This study examined the effects of dBP4 on IGF1-induced cell migration, invasion and angiogenesis in vitro. The effect of intra-tumour injections of dBP4 on tumour angiogenesis and metastasis was examined using the 4T1.2luc orthotopic model of breast cancer.

METHODS

PAPP-A resistance and IGF binding capacity of dBP4 were characterized by Western blot and surface plasmon resonance, respectively. 4T1.2luc are mouse mammary adenocarcinoma cells transfected with luciferase to allow in vivo imaging. The effect of dBP4 on IGF1-induced Akt activation in 4T1.2luc cells was assessed by Western blot. Cell migration and invasion assays were performed using 4T1.2luc cells. Angiokit™ assays and Matrigel® implants were used to assess the effects of dBP4 on angiogenesis in vitro and in vivo, respectively. An orthotopic breast cancer model - 4T1.2luc cells implanted in the mammary fat pad of BALB/c mice - was used to assess the effect of intra tumour injection of purified dBP4 on tumour angiogenesis and metastasis. Tumour growth and lung metastasis were examined by in vivo imaging and tumour angiogenesis was evaluated by CD31 immunohistochemistry.

RESULTS

Our engineered, PAPP-A resistant IGFBP4 (dBP4) retained IGF1 binding capacity and inhibited IGF1 activation of Akt as well as IGF1-induced migration and invasion by 4T1.2 mammary adenocarcinoma cells. dBP4 inhibited IGF1-induced angiogenesis in vitro and in Matrigel implants in vivo. Direct intra-tumour injection of soluble dBP4 reduced angiogenesis in 4T1.2 luc mammary tumours tumour and reduced lung metastasis.

CONCLUSION

A PAPP-A resistant IGFBP4, dBP4, inhibits angiogenesis and metastasis in 4T1.2 mammary fat pad tumours. This study highlights the therapeutic potential of dBP4 as an approach to block the tumour-promoting actions of IGF1.

Pregnancy-Associated Plasma Protein A (PAPP-A) Concentration in Population of Healthy Young People: Interactions with Tobacco Smoke and Anti-oxidative Status

Pregnancy-associated plasma protein A (PAPP-A) is a high-molecular zinc-binding metalloproteinase that was first detected in the serum of pregnant women. It can also be detected in men and non-pregnant women. Recently, a growing interest in determining the concentration of PAPP-A as a marker of oxidative stress and atherosclerotic processes has been observed. Among the factors that could potentially influence the PAPP-A formation is the exposure to tobacco smoke. Some components of tobacco smoke have an immediate effect on the body and also direct influence on the cardiovascular system. The aim of this study was to evaluate the relation between PAPP-A concentration and either passive or active exposure to tobacco smoke in the population of medicine students (n = 152). The relation between PAPP-A concentration and chosen markers of inflammatory response and anti-oxidative processes was analyzed. The samples of serum, urine, and saliva were collected and main nicotine metabolites in urine samples were determined using ELISA technique. Comparison of the PAPP-A concentrations in the study group revealed that in the group of active smokers, the concentration of the protein was significantly higher than in the group of passive smokers (p = .04) and the group of not-exposed students (p = .006). PAPP-A concentration showed significant positive correlation with the values of FRAP and main nicotine metabolites. The evident influence of both active and passive tobacco smoke exposure on PAPP-A levels in the studied population of young people who in general are not included in the group of high-risk cardiovascular incidents, shows how important early prevention of anti-health behaviors is.

IGFBP-4 and PAPP-A in normal physiology and disease

Insulin-like growth factor (IGF) binding protein-4 (IGFBP-4) is a modulator of the IGF system, exerting both inhibitory and stimulatory effects on IGF-induced cellular growth. IGFBP-4 is the principal substrate for the enzyme pregnancy-associated plasma protein-A (PAPP-A). Through IGF-dependent cleavage of IGFBP-4 in the vicinity of the IGF receptor, PAPP-A is able to increase IGF bioavailability and stimulate IGF-mediated growth. Recently, the stanniocalcins (STCs) were identified as novel inhibitors of PAPP-A proteolytic activity, hereby adding additional members to the seemingly endless list of proteins belonging to the IGF family. Our understanding of these proteins has advanced throughout recent years, and there is evidence to suggest that the role of IGFBP-4 and PAPP-A in defining the relationship between total IGF and IGF bioactivity can be linked to a number of pathological conditions. This review provides an overview of the experimental and clinical findings on the IGFBP-4/PAPP-A/STC axis as a regulator of IGF activity and examines the conundrum surrounding extrapolation of circulating concentrations to tissue action of these proteins. The primary focus will be on the biological significance of IGFBP-4 and PAPP-A in normal physiology and in pathophysiology with emphasis on metabolic disorders, cardiovascular diseases, and cancer. Finally, the review assesses current new trajectories of IGFBP-4 and PAPP-A research.

Pregnancy-associated plasma protein a in cancer: expression, oncogenic functions and regulation

Pregnancy-associated plasma protein A (PAPPA) is a protease that plays important roles in pregnancy, but interestingly acts as an oncogene outside of pregnancy. This review summarizes the oncogenic roles of PAPPA, including its expression levels in multiple malignancies, regulatory and signaling interactions, and pro-tumor functions, which include promoting tumor cell proliferation, invasion, migration and metastasis. These PAPPA activities are linked to IGFBP-4 proteolysis, increased IFG bioavailability, and activation of the NF-κB, PI3K/AKT and ERK signaling pathways. Therefore, PAPPA could be used as a biomarker for monitoring cancer development and progression as well as a potential therapeutic target.

Pregnancy-associated plasma protein-A is positively correlated with first-trimester skin microvascular reactivity

OBJECTIVE

To investigate the relationship between levels of circulating maternal pregnancy-associated plasma protein-A (PAPP-A) and first-trimester maternal vascular function.

METHODS

This was a cross-sectional study of 53 healthy, non-smoking, nulliparous pregnant women in Stockholm, Sweden. PAPP-A levels and vascular function were assessed during gestational weeks 11-14. Forearm skin microcirculation was investigated by laser Doppler perfusion imaging during iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) to assess endothelium-dependent and -independent microvascular vasodilatation, respectively. Microvascular endothelial function index was calculated as peak ACh/peak SNP. Endothelium-dependent and -independent vasodilatation in the brachial artery was evaluated, respectively, by postischemic hyperemia-induced flow-mediated vasodilatation (FMD) and by response to sublingual intake of glyceryl trinitrate (GTN).

RESULTS

PAPP-A was correlated with skin microvascular endothelial function index (β = 1.008 (95% CI, 0.34-1.68), r²  = 0.17, P = 0.004). PAPP-A also correlated inversely with FMD (β = -0.052 (95% CI, -0.094 to -0.011), r²  = 0.13, P = 0.014) but did not relate to forearm endothelial function index (i.e. FMD/GTN). The results were retained in multivariate analyses including known confounding factors.

CONCLUSIONS

First-trimester endothelium-dependent skin microvascular reactivity was positively related to PAPP-A levels. If confirmed, these novel findings suggest that first-trimester skin microvascular reactivity could be a useful early pregnancy marker of placental function. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

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.

Overexpression of lncRNA IGFBP4-1 reprograms energy metabolism to promote lung cancer progression

BACKGROUND

Reprogrammed energy metabolism as an emerging hallmark of cancer has recently drawn special attention since it facilitate cell growth and proliferation. Recently, long noncoding RNAs (lncRNAs) have been served as key regulators implicated in tumor development and progression by promoting proliferation, invasion and metastasis. However, the associations of lncRNAs with cellular energy metabolism in lung cancer (LC) need to be clarified.

METHODS

Here, we conducted bioinformatics analysis and found insulin-like growth factor binding protein 4-1 (IGFBP4-1) as a new candidate lncRNA located in the upstream region of IGFBP4 gene. The expression levels of lnc-IGFBP4-1, mRNA levels of IGFBP4 in 159 paired lung cancer samples and adjacent, histological normal tissues by qRT-PCR. Over-expression and RNA interference (RNAi) approaches were adopted to investigate the biological functions of lnc-IGFBP4-1. The intracellular ATP level was measured using the Cell Titer-Glo Luminescent Cell Viability Assay kit, and changes in metabolic enzymes were examined in cancer cells and normal pulmonary epithelial cells with qRT-PCR.

RESULTS

Our results showed that lnc-IGFBP4-1 was significantly up-regulated in LC tissues compared with corresponding non-tumor tissues (P < 0.01), and its expression level was significantly correlated with TNM stage (P < 0.01) and lymph node metastasis (P < 0.05). Further investigation showed that overexpression of lnc-IGFBP4-1 significantly promoted LC cell proliferation in vitro and in vivo, while downregulation of endogenous lnc-IGFBP4-1 could inhibited cell proliferation and induce apoptosis. Moreover, we found lnc-IGFBP4-1 could influences ATP production levels and expression of enzymes including HK2, PDK1 and LDHA, in addition, decline in both ATP production and these enzymes in response to 2-DG and 2-DG-combined Rho123, respectively, was observed in lnc-IGFBP4-1-overespressing LC cells, indicative of an enhanced aerobic glycolysis rate. Finally, lnc-IGFBP4-1 was observed to negatively correlate with gene IGFBP4, and lower expression level of IGFPB4 was found after lnc-IGFBP4-1-overexpression was transfected into PC9 cells, higher expression level of IGFPB4 was also found after lnc-IGFBP4-1-downregulation was transfected into GLC-82 cells, which indicates that IGFBP4 may exert its targeting function regulated by lnc-IGFBP4-1.

CONCLUSIONS

Taken together, these findings provide the first evidence that lnc-IGFBP4-1 is significantly up-regulated in LC tissues and plays a positive role in cell proliferation and metastasis through possible mechanism of reprogramming tumor cell energy metabolism, which suggests that lnc-IGFBP4-1 may be a promising biomarker in LC development and progression and as a potential therapeutic target for LC intervention.

Targeted Gene Deletion Using DNA-Free RNA-Guided Cas9 Nuclease Accelerates Adaptation of CHO Cells to Suspension Culture

Chinese hamster ovary (CHO) cells are the preferred host for the production of a wide array of biopharmaceuticals. Thus, efficient and rational CHO cell line engineering methods have been in high demand to improve quality and productivity. Here, we provide a novel genome engineering platform for increasing desirable phenotypes of CHO cells based upon the integrative protocol of high-throughput RNA sequencing and DNA-free RNA-guided Cas9 (CRISPR associated protein9) nuclease-based genome editing. For commercial production of therapeutic proteins, CHO cells have been adapted for suspension culture in serum-free media, which is highly beneficial with respect to productivity and economics. To engineer CHO cells for rapid adaptation to a suspension culture, we exploited strand-specific RNA-seq to identify genes differentially expressed according to their adaptation trajectory in serum-free media. More than 180 million sequencing reads were generated and mapped to the currently available 109,152 scaffolds of the CHO-K1 genome. We identified significantly downregulated genes according to the adaptation trajectory and then verified their effects using the genome editing method. Growth-based screening and targeted amplicon sequencing revealed that the functional deletions of Igfbp4 and AqpI gene accelerate suspension adaptation of CHO-K1 cells. The availability of this strand-specific transcriptome sequencing and DNA-free RNA-guided Cas9 nuclease mediated genome editing facilitates the rational design of the CHO cell genome for efficient production of high quality therapeutic proteins.

Clinical studies in humans targeting the various components of the IGF system show lack of efficacy in the treatment of cancer

The insulin-like growth factors (IGFs) system regulates cell growth, differentiation and energy metabolism and plays crucial role in the regulation of key aspects of tumor biology, such as cancer cell growth, survival, transformation and invasion. The current focus for cancer therapeutic approaches have shifted from the conventional treatments towards the targeted therapies and the IGF system has gained a great interest as anti-cancer therapy. The proliferative, anti-apoptotic and transformation effects of IGFs are mainly triggered by the ligation of the type I IGF receptor (IGF-IR). Thus, aiming at developing novel and effective cancer therapies, different strategies have been employed to target IGF system in human malignancies, including but not limited to ligand or receptor neutralizing antibodies and IGF-IR signaling inhibitors. In this review, we have focused on the clinical studies that have been conducted targeting the various components of the IGF system for the treatment of different types of cancer, providing a description and the challenges of each targeting strategy and the degree of success.

The Non-coding Mammary Carcinoma Susceptibility Locus, Mcs5c, Regulates Pappa Expression via Age-Specific Chromatin Folding and Allele-Dependent DNA Methylation

In understanding the etiology of breast cancer, the contributions of both genetic and environmental risk factors are further complicated by the impact of breast developmental stage. Specifically, the time period ranging from childhood to young adulthood represents a critical developmental window in a woman’s life when she is more susceptible to environmental hazards that may affect future breast cancer risk. Although the effects of environmental exposures during particular developmental Windows of Susceptibility (WOS) are well documented, the genetic mechanisms governing these interactions are largely unknown. Functional characterization of the Mammary Carcinoma Susceptibility 5c, Mcs5c, congenic rat model of breast cancer at various stages of mammary gland development was conducted to gain insight into the interplay between genetic risk factors and WOS. Using quantitative real-time PCR, chromosome conformation capture, and bisulfite pyrosequencing we have found that Mcs5c acts within the mammary gland to regulate expression of the neighboring gene Pappa during a critical mammary developmental time period in the rat, corresponding to the human young adult WOS. Pappa has been shown to positively regulate the IGF signaling pathway, which is required for proper mammary gland/breast development and is of increasing interest in breast cancer pathogenesis. Mcs5c-mediated regulation of Pappa appears to occur through age-dependent and mammary gland-specific chromatin looping, as well as genotype-dependent CpG island shore methylation. This represents, to our knowledge, the first insight into cellular mechanisms underlying the WOS phenomenon and demonstrates the influence developmental stage can have on risk locus functionality. Additionally, this work represents a novel model for further investigation into how environmental factors, together with genetic factors, modulate breast cancer risk in the context of breast developmental stage.

A woman’s lifetime risk of developing breast cancer is affected by both genetic and environmental risk factors that can be further exacerbated by breast developmental stage. Time periods conferring increased risk are referred to as Windows of Susceptibility (WOS) and, generally speaking, the molecular mechanisms responsible for their effect on breast cancer risk are unknown. Our work presented here on the characterization of the rat Mammary Carcinoma Susceptibility 5c, Mcs5c, locus has identified a region within Mcs5c that interacts with the neighboring gene, Pappa, in an age-dependent manner to influence gene expression via genotype-dependent DNA methylation. Importantly, Mcs5c-mediated gene regulation occurs specifically within a WOS, and these finding represent the first identified molecular mechanisms by which a WOS influences the ability of a locus to affect mammary/breast cancer risk. This work highlights the importance developmental stage can have on genetic risk factor function, and we anticipate that the Mcs5c locus will serve as a model for future studies on WOS in combination with genetic and environmental risk factors.

Octylphenol induced gene expression in testes of Frog, Rana chensinensis

Octylphenol (OP) is an endocrine-disrupting chemical (EDC), which can disrupt the reproductive system. To understand the effect of OP, a subtractive cDNA library was constructed using suppression subtractive hybridization (SSH) to identify alterations of gene transcription in the testes of the frog Rana chensinensis after OP exposure. Two hundred positive clones were selected and 134 sequences of gene fragments were produced from the subtractive library randomly. These genes were identified to be involved in metabolic process, cellular process, biological regulation, stimulus, immune system and female pregnancy process. In order to verify the efficiency of the subtractive cDNA library, PSG9 and PAPP-A were analyzed further as two representatives of differentially expressed transcription genes using semi-quantitative RT-PCR. Our result was the first successful construction of the subtractive cDNA library in frog testes after OP treatment. Based on this cDNA library, OP was shown to affect multiple physiological processes including inducing immune response, disrupting the steroid hormone synthesis and influencing spermatogenesis in the testis by up-regulation of specific genes.

Pregnancy associated plasma protein-A links pregnancy and melanoma progression by promoting cellular migration and invasion

Melanoma is the most common cancer diagnosed in pregnant women and an aggressive course with poorer outcomes is commonly described during pregnancy or shortly after childbirth. The underlying mechanisms for this are not understood. Here, we report that melanoma migration, invasiveness and progression are promoted by pregnancy-associated plasma protein-A (PAPPA), a pregnancy-associated metalloproteinase produced by the placenta that increases the bioavailability of IGF1 by cleaving it from a circulating complex formed with IGFBP4. We show that PAPPA is widely expressed by metastatic melanoma tumors and is elevated in melanoma cells exhibiting mesenchymal, invasive and label-retaining phenotypes. Notably, inhibition of PAPPA significantly reduced invasion and migration of melanoma cells in vitro and in vivo within the embryonic chicken neural tube. PAPPA-enriched pregnancy serum treatment enhanced melanoma motility in vitro. Furthermore, we report that IGF1 can induce the phenotypic and functional effects of epithelial-to-mesenchymal transition (EMT) in melanoma cells. In this study, we establish a clear relationship between a pregnancy-associated protein PAPPA, melanoma and functional effects mediated through IGF1 that provides a plausible mechanism for accelerated melanoma progression during pregnancy. This opens the possibility of targeting the PAPPA/IGF1 axis therapeutically.

Abnormal IGF-Binding Protein Profile in the Bone Marrow of Multiple Myeloma Patients

Insulin-like growth factor (IGF) signalling plays a key role in homing, progression, and treatment resistance in multiple myeloma (MM). In the extracellular environment, the majority of IGF molecules are bound to one of six IGF-binding proteins (IGFBP1-6), leaving a minor fraction of total IGF free and accessible for receptor activation. In MM, high IGF-receptor type 1 expression levels correlate with a poor prognosis, but the status and role of IGF and IGFBPs in the pathobiology of MM is unknown. Here we measured total IGF1, IGF2, and intact IGFBP levels in blood and bone marrow samples from MM (n = 17), monoclonal gammopathy of undetermined significance (MGUS) (n = 37), and control individuals (n = 15), using ELISA (IGFs) and 125I-IGF1 Western Ligand Blotting (IGFBPs). MGUS and MM patients displayed a significant increase in intact IGFBP-2 (2.5-3.8 fold) and decrease in intact IGFBP-3 (0.6-0.5 fold) in the circulation compared to control individuals. Further, IGFBP-2 as well as total IGFBP levels were significantly lower in bone marrow compared to circulation in MM and MGUS only, whereas IGF1, IGF2, and IGFBP-3 were equally distributed between the two compartments. In conclusion, the profound change in IGFBP profile strongly suggests an increased IGF bioavailability in the bone marrow microenvironment in MGUS and MM, despite no change in growth factor concentration.

Interaction of AIM with insulin-like growth factor-binding protein-4

Apoptosis inhibitor of macrophages (AIM/cluster of differentiation 5 antigen-like/soluble protein α) has been shown to inhibit cellular apoptosis; however, the underlying molecular mechanism has not been elucidated. Using yeast two-hybrid screening, the present study uncovered that AIM binds to insulin-like growth factor binding protein-4 (IGFBP-4). AIM interaction with IGFBP-4, as well as IGFBP-2 and -3, but not with IGFBP-1, -5 and -6, was further confirmed by co-immunoprecipitation (co-IP) using 293 cells. The binding activity and affinity between AIM and IGFBP-4 in vitro were analyzed by co-IP and biolayer interferometry. Serum depletion-induced cellular apoptosis was attenuated by insulin-like growth factor-I (IGF-I), and this effect was abrogated by IGFBP-4. Of note, in the presence of AIM, the inhibitory effect of IGFBP-4 on the anti-apoptosis function of IGF-I was attenuated, possibly through binding of AIM with IGFBP-4. In conclusion, to the best of our knowledge, the present study provides the first evidence that AIM binds to IGFBP-2, -3 and -4. The data suggest that this interaction may contribute to the mechanism of AIM-mediated anti-apoptosis function.

Relevance of IGFBP2 proteolysis in glioma and contribution of the extracellular protease ADAMTS1

Expression of IGFBP2 (Insulin-like Growth Factor Binding Protein 2) has been positively correlated with glioma progression. Although the proteolysis of IGFBP2 has been widely recognized, with consequences as a major modulator of IGFII signaling, the relevance of this post-translational modification has not been well studied in tumors. Using an in vivo proteomic approach by Isotope-Coded Protein Label (ICPL), we identified IGFBP2 as a target of the extracellular protease ADAMTS1 (A Disintegrin And Metalloproteinase with ThromboSpondin motifs 1). Notably, the proteolytic pattern of IGFBP2 was also detected in human glioma culture cells and, more importantly, in all glioma samples evaluated. In addition, high expression of ADAMTS1 correlates with higher levels of cleaved IGFBP2 in glioblastoma multiforme cases. Using gene expression public databases, we confirmed that IGFBP2 is a poor prognosis marker for gliomas, and we also observed an important contribution of ADAMTS1.Finally, we showed the impact of ADAMTS1 on IGFII-mediated IGF1R phosphorylation and cellular migration. Our results support a functional interaction between IGFBP2 and ADAMTS1 and suggest the need to evaluate post-translational modifications of IGFBP2 in glioma, in order to approach new therapies.

Insulin-like growth factor system in cancer: novel targeted therapies

Insulin-like growth factors (IGFs) are essential for growth and survival that suppress apoptosis and promote cell cycle progression, angiogenesis, and metastatic activities in various cancers. The IGFs actions are mediated through the IGF-1 receptor that is involved in cell transformation induced by tumour. These effects depend on the bioavailability of IGFs, which is regulated by IGF binding proteins (IGFBPs). We describe here the role of the IGF system in cancer, proposing new strategies targeting this system. We have attempted to expand the general viewpoint on IGF-1R, its inhibitors, potential limitations of IGF-1R, antibodies and tyrosine kinase inhibitors, and IGFBP actions. This review discusses the emerging view that blocking IGF via IGFBP is a better option than blocking IGF receptors. This can lead to the development of novel cancer therapies.

Indirect targeting of IGF receptor signaling in vivo by substrate-selective inhibition of PAPP-A proteolytic activity

The insulin-like growth factor (IGF) signaling pathway is involved in certain human cancers, and the feasibility of directly targeting the IGF receptor has been actively investigated. However, recent evidence from clinical trials suggests that this approach can be problematic. We have developed an alternative strategy to indirectly inhibit the IGF signaling by targeting the metalloproteinase, pregnancy-associated plasma protein-A (PAPP-A). PAPP-A associated with the cell surface cleaves IGF binding protein-4 (IGFBP-4), when IGF is bound to IGFBP-4, and thereby increases IGF bioavailability for receptor activation in an autocrine/paracrine manner. We hypothesized that inhibition of PAPP-A would suppress excessive local IGF signaling in tissues where this is caused by increased PAPP-A proteolytic activity. To test this hypothesis, we developed an inhibitory monoclonal antibody, mAb 1/41, which targets a unique substrate-binding exosite of PAPP-A. This inhibitor selectively and specifically inhibits proteolytic cleavage of IGFBP-4 with an inhibitory constant (Ki) of 135 pM. In addition, it inhibited intracellular signaling of the IGF receptor (AKT phosphorylation) in monolayers of A549 cells, an IGF-responsive lung cancer-derived cell line found to express high levels of PAPP-A. We further showed that mAb 1/41 is effective towards PAPP-A bound to cell surfaces, and that it is capable of inhibiting PAPP-A activity in vivo. Using a murine xenograft model of A549 cells, we demonstrated that mAb 1/41 administered intraperitoneally significantly inhibited tumor growth. Analysis of xenograft tumor tissue recovered from treated mice showed penetration of mAb 1/41, reduced IGFBP-4 proteolysis, and reduced AKT phosphorylation. Our study provides proof of concept that IGF signaling can be selectively reduced by targeting a regulatory proteinase that functions extracellularly, upstream of the IGF receptor. PAPP-A targeting thus represents an alternative therapeutic strategy for inhibiting IGF receptor signaling.

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.

The role of PAPP-A in the IGF system: location, location, location

Although discovered as a placental protein present abundantly in the circulation of pregnant women, pregnancy-associated plasma protein-A (PAPP-A) is widely expressed in multiple tissues. PAPP-A is a highly specific metalloproteinase binding tightly to glycosaminoglycans present on the surface of cells. By cleaving a subset of insulin-like growth factor binding proteins (IGFBPs), PAPP-A thus functions within tissues as a growth-promoting enzyme, releasing bioactive IGF in close proximity to the IGF receptor. IGFBP-4 is believed to be the principal PAPP-A substrate, and the focus in this review is on PAPP-A enzymatic activity and its role in the PAPP-A-IGFBP-4-IGF axis, which is subject to regulation at several different levels. These include e.g., transcriptional control, competing reactions potentially sequestering IGF from IGFBP-4 and hence antagonizing PAPP-A-mediated IGF activation, and proteolytic inhibition of PAPP-A. The latter may involve the protein stanniocalcin-2 (STC2), recently found to potently inhibit PAPP-A activity by forming a covalent complex with PAPP-A. PAPP-A or complex-bound variants may escape from pathological tissues into the circulation. It is emphasized that the potential use of PAPP-A as a diagnostic or predictive biomarker in nonpregnant individuals requires precise knowledge of analyte identity and assay specificity in addition to an appropriate material for standardization. Finally, PAPP-A may serve as a therapeutic target to indirectly inhibit IGF signaling in tissues where this is driven by increased PAPP-A activity. By taking advantage of the intricate interaction between PAPP-A and IGFBP-4, highly specific and selective inhibition of PAPP-A is possible.

Preliminary screening of differentially expressed genes involved in methyl-CpG-binding protein 2 gene-mediated proliferation in human osteosarcoma cells

Methyl-CpG-binding protein 2 (MeCP2) is essential in human brain development and has been linked to several cancer types and neuro-developmental disorders. This study aims to screen the MeCP2 related differentially expressed genes and discover the therapeutic targets for osteosarcoma. CCK8 assay was used to detect the proliferation and SaOS2 and U2OS cells. Apoptosis of cells was detected by flow cytometry analysis that monitored Annexin V-APC/7-DD binding and 7-ADD uptake simultaneously. Denaturing formaldehyde agarose gel electrophoresis was employed to examine the quality of total RNA 18S and 28S units. Gene chip technique was utilized to discover the differentially expressed genes correlated with MeCP2 gene. Differential gene screening criteria were used to screen the changed genes. The gene up-regulation or down-regulation more than 1.5 times was regarded as significant differential expression genes. The CCK8 results indicated that the cell proliferation of MeCP2 silencing cells (LV-MeCP2-RNAi) was significantly decreased compared to non-silenced cells (LV-MeCP2-RNAi-CN) (P < 0.05). MeCP2 silencing could also induce significant apoptosis compared to non-silenced cells (P < 0.05); 107 expression changed genes were screened from a total of 49,395 transcripts. Among the total 107 transcripts, 34 transcripts were up-regulated and 73 transcripts were down-regulated. There were five significant differentially expressed genes, including IGFBP4, HOXC8, LMO4, MDK, and CTGF, which correlated with the MeCP2 gene. The methylation frequency of CpG in IGFBP4 gene could achieve 55%. In conclusion, the differentially expressed IGFBP4, HOXC8, LMO4, MDK, and CTGF genes may be involved in MeCP2 gene-mediated proliferation and apoptosis in osteosarcoma cells.

Estrogen Receptor-β and the Insulin-Like Growth Factor Axis as Potential Therapeutic Targets for Triple-Negative Breast Cancer

Triple-negative breast cancers (TNBCs) lack estrogen receptor-α (ERα), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) amplification and account for almost half of all breast cancer deaths. This breast cancer subtype largely affects women who are premenopausal, African-American, or have BRCA1/2 mutations. Women with TNBC are plagued with higher rates of distant metastasis that significantly diminish their overall survival and quality of life. Due to their poor response to chemotherapy, patients with TNBC would significantly benefit from development of new targeted therapeutics. Research suggests that the insulin-like growth factor (IGF) family and estrogen receptor beta-1 (ERβ1), due to their roles in metabolism and cellular regulation, might be attractive targets to pursue for TNBC management. Here, we review the current state of the science addressing the roles of ERβ1 and the IGF family in TNBC. Further, the potential benefit of metformin treatment in patients with TNBC as well as areas of therapeutic potential in the IGF-ERβ1 pathway are highlighted.

Pregnancy-associated plasma protein-A expression in human breast cancer

OBJECTIVE

Pregnancy-associated plasma protein-A (PAPP-A) is a zinc metalloproteinase in the insulin-like growth factor system that is expressed by tissues outside of pregnancy and involved in normal and dysregulated growth. PAPP-A has been implicated in several cancers. However, studies of PAPP-A expression in breast cancer are limited. In this study, we assessed PAPP-A expression in different subtypes of human malignant breast cancer. Design Formalin-fixed paraffin-embedded tumor samples from 46 female patients with invasive breast cancer were divided into five defined groups [using markers for HER2, estrogen receptor, progesterone receptor, proliferation] that roughly correlate with molecularly defined subtypes (luminal A, luminal B, luminal/HER2 +, HER2 +, triple negative). These samples were analyzed for PAPP-A expression by immunohistochemistry.

RESULTS

PAPP-A staining in tumor tissue was detected in 45 of 46 specimens. There were significantly greater extent and intensity of PAPP-A expression in luminal B specimens with high proliferation index than luminal A specimens (P = 0.01). However, there were no differences between specimens positive or negative for HER2 (P = 0.14) or positive and negative for estrogen receptor (P = 0.31).

CONCLUSION

PAPP-A was detected in almost all breast cancer specimens and a more intense and greater extent of its expression was associated with luminal B specimens compared to luminal A specimens. The role of PAPP-A in breast cancer prognosis, and possibly therapeutics, warrants further investigation.

Identification of pregnancy-associated plasma protein A as a migration-promoting gene in malignant pleural mesothelioma cells: a potential therapeutic target

Despite recent advances in treatment, malignant pleural mesothelioma (MPM) remains a deadly disease. Targeted therapy generated broad interests and is highly expected for the treatment of MPM, yet promising preclinical results have not been translated into substantial clinical benefits for the patients. In this study, we tried to identify the genes which play functional roles in cell migration as well as to test whether they can be used as novel targets for molecular targeted therapy for MPM in preclinical model. In our study, pregnancy-associated plasma protein A (PAPPA) was identified as a gene whose expression level is correlated with MPM cell migration by correlation analysis combining MPM cell migration ability and their gene expression profiles. Highly migratory cells were selected from MPM cell lines, MSTO-211H, NCI-H290 and EHMES-1 in vitro and up-regulation of PAPPA in these cells were confirmed. In vitro, PAPPA was demonstrated to stimulate the MPM cell migration via cleavage of insulin-like growth factor-binding protein-4 and subsequent release of IGF-1. Gene silencing of PAPPA in MPM cells led to reduced migration, invasion and proliferation. Furthermore, PAPPA shRNA transfected NCI-H290 when orthotopically inoculated into pleural cavity of severe combined immunodeficiency recipient mice, failed to develop tumors and produce bloody pleural effusion as control shRNA transfected cells did. Our study suggests that PAPPA plays a functional role in promoting MPM cell migration and it might serve as a potential therapeutic target for the treatment of MPM.

Exogenous administration of protease-resistant, non-matrix-binding IGFBP-2 inhibits tumour growth in a murine model of breast cancer

BACKGROUND

Insulin-like growth factors (IGF-I and IGF-II) signal via the type 1 IGF receptor (IGF-1R) and IGF-II also activates the insulin receptor isoform A (IR-A). Signalling via both receptors promotes tumour growth, survival and metastasis. In some instances IGF-II action via the IR-A also promotes resistance to anti-IGF-1R inhibitors. This study assessed the efficacy of two novel modified IGF-binding protein-2 (IGFBP-2) proteins that were designed to sequester both IGFs. The two modified IGFBP-2 proteins were either protease resistant alone or also lacked the ability to bind extracellular matrix (ECM).

METHODS

The modified IGFBP-2 proteins were tested in vitro for their abilities to inhibit cancer cell proliferation and in vivo to inhibit MCF-7 breast tumour xenograft growth.

RESULTS

Both mutants retained low nanomolar affinity for IGF-I and IGF-II (0.8-2.1-fold lower than IGFBP-2) and inhibited cancer cell proliferation in vitro. However, the combined protease resistant, non-matrix-binding mutant was more effective in inhibiting MCF-7 tumour xenograft growth and led to inhibition of angiogenesis.

CONCLUSIONS

By removing protease cleavage and matrix-binding sites, modified IGFBP-2 was effective in inhibiting tumour growth and reducing tumour angiogenesis.

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.

Control of adipose tissue expandability in response to high fat diet by the insulin-like growth factor-binding protein-4

Adipose tissue expansion requires growth and proliferation of adipocytes and the concomitant expansion of their stromovascular network. We have used an ex vivo angiogenesis assay to study the mechanisms involved in adipose tissue expansion. In this assay, adipose tissue fragments placed under pro-angiogenic conditions form sprouts composed of endothelial, perivascular, and other proliferative cells. We find that sprouting was directly stimulated by insulin and was enhanced by prior treatment of mice with the insulin sensitizer rosiglitazone. Moreover, basal and insulin-stimulated sprouting increased progressively over 30 weeks of high fat diet feeding, correlating with tissue expansion during this period. cDNA microarrays analyzed to identify genes correlating with insulin-stimulated sprouting surprisingly revealed only four positively correlating (Fads3, Tmsb10, Depdc6, and Rasl12) and four negatively correlating (Asph, IGFbp4, Ppm1b, and Adcyap1r1) genes. Among the proteins encoded by these genes, IGFbp4, which suppresses IGF-1 signaling, has been previously implicated in angiogenesis, suggesting a role for IGF-1 in adipose tissue expandability. Indeed, IGF-1 potently stimulated sprouting, and the presence of activated IGF-1 receptors in the vasculature was revealed by immunostaining. Recombinant IGFbp4 blocked the effects of insulin and IGF-1 on mouse adipose tissue sprouting and also suppressed sprouting from human subcutaneous adipose tissue. These results reveal an important role of IGF-1/IGFbp4 signaling in post-developmental adipose tissue expansion.

Extracellular matrix signatures of human mammary carcinoma identify novel metastasis promoters

The extracellular matrix (ECM) is a major component of tumors and a significant contributor to cancer progression. In this study, we use proteomics to investigate the ECM of human mammary carcinoma xenografts and show that primary tumors of differing metastatic potential differ in ECM composition. Both tumor cells and stromal cells contribute to the tumor matrix and tumors of differing metastatic ability differ in both tumor- and stroma-derived ECM components. We define ECM signatures of poorly and highly metastatic mammary carcinomas and these signatures reveal up-regulation of signaling pathways including TGFβ and VEGF. We further demonstrate that several proteins characteristic of highly metastatic tumors (LTBP3, SNED1, EGLN1, and S100A2) play causal roles in metastasis, albeit at different steps. Finally we show that high expression of LTBP3 and SNED1 correlates with poor outcome for ER⁻/PR⁻breast cancer patients. This study thus identifies novel biomarkers that may serve as prognostic and diagnostic tools.

DOI:http://dx.doi.org/10.7554/eLife.01308.001

Metastasis is the process whereby tumor cells spread within the body and is the cause of most deaths from cancer. This complex process involves several steps: first the cancer cells invade the tissues that surround the tumor; second, the cancer cells enter the blood stream and travel throughout the body; and third, the cancer cells seed the growth of new tumors in distant organs.

Within tissues, the extracellular matrix forms a complex scaffold of proteins that surrounds cells, to support and organize them: it also provides signals that control how much cells can multiply, how likely cells are to stick together or migrate, and even a cell’s chances of survival. Pathologists have used an accumulation of extracellular matrix proteins in tumors as a sign that the outcome of the disease will likely be unfavorable for a patient, and that treatment will be challenging. However, we still do not have a clear picture of the composition of the tumor extracellular matrix and we do not know all the details of how it affects tumor growth and metastasis.

Now, Naba et al. have explored these questions by injecting different types of human breast tumor cells into mice. Some of the cells were capable of spreading throughout the body and were said to have a high ‘metastatic potential’; others were less capable of spreading and were said to have a low metastatic potential. Naba et al. then analyzed the proteins that made up the extracellular matrix of the tumors that grew in the mice. Some proteins were found in both types of tumor; whereas some proteins were only found in the tumors with low metastatic potential and some were only found in the highly metastatic tumors. Naba et al. also demonstrated that both cancer cells and non-cancer cells—which are also found within the tumors—contributed to the production of the extracellular matrix in the tumor. Moreover, and somewhat surprisingly, the contributions from the non-cancer cells in the two types of tumors were also different.

Computational analysis predicted that the production of several extracellular matrix proteins in the highly metastatic tumors was under the control of signaling pathways that are involved in cancer progression. Furthermore, Naba et al. also demonstrated that several of the extracellular matrix proteins specific to highly metastatic tumors were required for the cancer to spread. These proteins are involved in different stages of the metastatic process, and some of them are commonly over-produced in tumors from patients with some of the worst chances of recovery.

If similar results are consistently observed in clinical samples from humans, the work of Naba et al. could help doctors to discriminate between tumors that will spread and those that will not, which should lead to improved patient care. The proteins and pathways associated with the highly metastatic tumors could be also investigated as potential drug targets.

DOI:http://dx.doi.org/10.7554/eLife.01308.002

Development of a recombinant antibody towards PAPP-A for immunohistochemical use in multiple animal species

The metalloproteinase, pregnancy-associated plasma protein-A (PAPP-A), is increasingly recognized as a modulator of insulin-like growth factor (IGF) signaling; it cleaves IGF binding proteins causing the release of bioactive IGF. Accumulating evidence supports an important role of PAPP-A in both normal physiology and under different pathological conditions. However, antibodies for the detection of PAPP-A in non-human tissues have been lacking, although needed for use with several animal models which are currently being developed. To develop a monoclonal antibody suitable for the immunohistochemical detection of PAPP-A, we therefore selected a phage-derived scFv antibody, PAC1, specifically recognizing an epitope of PAPP-A, which is highly conserved between multiple animal species. We first converted this antibody into bivalent IgG, and verified its ability to recognize PAPP-A in sections of formalin-fixed and paraffin-embedded tissue. For increased sensitivity, affinity maturation to sub-nanomolar affinity was then carried out. The resulting recombinant antibody, PAC1-D8-mIgG2a, detects PAPP-A specifically and sensitively in human tissue. In addition, this antibody allows detection of PAPP-A in non-human species. We demonstrate its usefulness for the visualization of PAPP-A in murine and porcine tissues.

PAPP-A in cardiac and non-cardiac conditions

Pregnancy-associated plasma protein-A (PAPP-A), a newly discovered member of insulin like growth factors (IGFs) axis, has been reported to be a biomarker in both cardiac and non-cardiac conditions. PAPP-A mainly acts as a protease cleaving IGF inhibitors - IGF binding proteins (IGFBPs), thereby setting free IGFs. In cardiac conditions, PAPP-A plays an important role in progressive atherosclerosis. As a biomarker, PAPP-A is not only sensitive, specific and early for diagnosis of acute coronary syndrome, but also an independent risk factor for all-cause mortality or combined cardiovascular events. In non-cardiac conditions, PAPP-A is a new anti-aging target. PAPP-A knock out (KO) mice have a prolonged lifespan than the wild type. In addition, PAPP-A is also a biomarker associated with malignant cancer and end stage renal disease.

Key questions and answers about pregnancy-associated plasma protein-A

Twenty-five years after it was identified as a circulating protein of unknown function derived from the placenta, pregnancy-associated plasma protein-A (PAPP-A) was discovered to be a novel zinc metalloproteinase expressed by a variety of cell types. Great progress has been made in understanding the biology of PAPP-A and its regulation during recent years, especially in regard to physiological and pathophysiological inflammatory injury responses. However, much remains to be learned about this complex protein and its potential clinical implications outside pregnancy. In this article we address some of the outstanding questions about PAPP-A, in particular about its newly emerging role in the insulin-like growth factor (IGF) system.

IGFBP ratio confers resistance to IGF targeting and correlates with increased invasion and poor outcome in breast tumors

PURPOSE

To improve the significance of insulin-like growth factor-binding protein 5 (IGFBP-5) as a prognostic and potentially predictive marker in patients with breast cancer.

EXPERIMENTAL DESIGN

Increased IGFBP-5 expression was identified in MCF-7 cells resistant (MCF-7R4) to the IGF-1R/insulin receptor (InsR) inhibitor BMS-536924 and its role examined by targeted knockdown and overexpression in multiple experimental models. Protein expression of IGFBP-5 was measured by immunohistochemistry in a cohort of 76 patients with breast cancer to examine correlative associations with invasive tumor fraction and outcome. The use of a combined IGFBP-5/IGFBP-4 (BPR) expression ratio was applied to predict anti-IGF-1R/InsR response in a panel of breast cancer lines and outcome in multiple breast tumor cohorts.

RESULTS

IGFBP-5 knockdown decreased BMS-536924 resistance in MCF-7R4 cells, whereas IGFBP-5 overexpression in MCF-7 cells conferred resistance. When compared with pathologically normal reduction mammoplasty tissue, IGFBP-5 expression levels were upregulated in both invasive and histologically normal adjacent breast cancer tissue. In both univariate and multivariate modeling, metastasis-free survival, recurrence free survival (RFS), and overall survival (OS) were significantly associated with high IGFBP-5 expression. Prognostic power of IGFBP-5 was further increased with the addition of IGFBP-4 where tumors were ranked based upon IGFBP-5/IGFBP-4 expression ratio (BPR). Multiple breast cancer cohorts confirm that BPR (high vs. low) was a strong predictor of RFS and OS.

CONCLUSION

IGFBP-5 expression is a marker of poor outcome in patients with breast cancer. An IGFBP-5/IGFBP-4 expression ratio may serve as a surrogate biomarker of IGF pathway activation and predict sensitivity to anti-IGF-1R targeting.

Insulin-like growth factor binding proteins: a structural perspective

Insulin-like growth factor binding proteins (IGFBP-1 to -6) bind insulin-like growth factors-I and -II (IGF-I and IGF-II) with high affinity. These binding proteins maintain IGFs in the circulation and direct them to target tissues, where they promote cell growth, proliferation, differentiation, and survival via the type 1 IGF receptor. IGFBPs also interact with many other molecules, which not only influence their modulation of IGF action but also mediate IGF-independent activities that regulate processes such as cell migration and apoptosis by modulating gene transcription. IGFBPs-1 to -6 are structurally similar proteins consisting of three distinct domains, N-terminal, linker, and C-terminal. There have been major advances in our understanding of IGFBP structure in the last decade and a half. While there is still no structure of an intact IGFBP, several structures of individual N- and C-domains have been solved. The structure of a complex of N-BP-4:IGF-I:C-BP-4 has also been solved, providing a detailed picture of the structural features of the IGF binding site and the mechanism of binding. Structural studies have also identified features important for interaction with extracellular matrix components and integrins. This review summarizes structural studies reported so far and highlights features important for binding not only IGF but also other partners. We also highlight future directions in which structural studies will add to our knowledge of the role played by the IGFBP family in normal growth and development, as well as in disease.

Insulin-like growth factor binding protein-4 differentially inhibits growth factor-induced angiogenesis

An in-depth understanding of the molecular and cellular complexity of angiogenesis continues to advance as new stimulators and inhibitors of blood vessel formation are uncovered. Gaining a more complete understanding of the response of blood vessels to both stimulatory and inhibitory molecules will likely contribute to more effective strategies to control pathological angiogenesis. Here, we provide evidence that endothelial cell interactions with structurally altered collagen type IV may suppress the expression of insulin-like growth factor binding protein-4 (IGFBP-4), a well documented inhibitor of the IGF-1/IGF-1R signaling axis. We report for the first time that IGFBP-4 differentially inhibits angiogenesis induced by distinct growth factor signaling pathways as IGFBP-4 inhibited FGF-2- and IGF-1-stimulated angiogenesis but failed to inhibit VEGF-induced angiogenesis. The resistance of VEGF-stimulated angiogenesis to IGFBP-4 inhibition appears to depend on sustained activation of p38 MAPK as blocking its activity restored the anti-angiogenic effects of IGFBP-4 on VEGF-induced blood vessel growth in vivo. These novel findings provide new insight into how blood vessels respond to endogenous inhibitors during angiogenesis stimulated by distinct growth factor signaling pathways.

Overexpression of pregnancy-associated plasma protein-A in ovarian cancer cells promotes tumor growth in vivo

Pregnancy-associated plasma protein-A (PAPP-A) is an important regulatory component of the IGF system. Through proteolysis of inhibitory IGF binding proteins (IGFBPs), PAPP-A acts as a positive modulator of local IGF signaling in a variety of biological systems. A role of IGF in the progression of several common forms of human cancer is now emerging, and therapeutic intervention of IGF receptor signaling is currently being explored. However, little is known about the activities of other components of the IGF system in relation to cancer. We hypothesized that PAPP-A acts to enhance tumor growth in vivo. To test this hypothesis, we overexpressed wild-type PAPP-A or a mutant PAPP-A with markedly reduced IGFBP protease activity in SKOV3 cells, a human ovarian carcinoma cell line with low tumorigenic potential. In vitro, SKOV3 clones with elevated PAPP-A expression (PAPP-A-1, PAPP-A-28) showed accelerated anchorage-independent growth in soft agar assays compared to clones overexpressing mutant PAPP-A (E483Q-1, E483Q-5) and vector controls. PAPP-A-28, with the highest PAPP-A expression and IGFBP proteolytic activity, also had markedly increased cell invasion through Matrigel. In vivo, we found significantly accelerated tumor growth rates of PAPP-A-overexpressing SKOV3 clones compared with mutant PAPP-A and controls. Investigation of angiogenesis indicated that overexpression of PAPP-A favored development of mature tumor vasculature and that tumor precursors of PAPP-A-28 in particular had a significantly higher degree of vascularization months before obvious tumor development. In conclusion, our data show that PAPP-A proteolytic activity enhances the tumorigenic potential of ovarian cancer cells and establish a novel tumor growth-promoting role of PAPP-A.

Insulin-like growth factor binding protein-4 gene silencing in lung adenocarcinomas

Gene silencing by promoter hypermethylation plays an important role in molecular pathogenesis. We previously reported that insulin-like growth factor (IGF) binding protein-4 (IGFBP-4), which inhibits IGF-dependent growth, is expressed via early growth response-1 (EGR-1) and is often silenced in cultivated lung cancer cells. The purpose of the present study was to clarify clinicopathological factors associated with IGFBP-4 gene silencing in lung adenocarcinomas. Seventy-six surgically resected adenocarcinomas (20 well-, 35 moderately-, and 21 poorly-differentiated) were subjected to methylation-specific polymerase chain reaction (PCR) analysis for EGR-1-binding sites located in the IGFBP-4 promoter and immunohistochemistry for IGFBP-4, EGR-1, and Ki-67. Thirty-two adenocarcinomas (42%) revealed IGFBP-4 promoter hypermethylation, and the severity inversely correlated with the level of IGFBP-4 expression (P < 0.0001) and tumor differentiation (well versus poor, P = 0.0278; well/moderate versus poor, P = 0.0395). Furthermore, there was a negative correlation between Ki-67 labeling index and IGFBP-4 expression (P = 0.0361). These findings suggest that the expression of IGFBP-4 in adenocarcinoma cells in vivo is downregulated by epigenetic silencing in association with tumor differentiation, resulting in disruption of the mechanism of IGFBP-4-mediated growth inhibition.