Binding properties and distribution of insulin-like growth factor binding protein-related protein 3 (IGFBP-rP3/NovH), an additional member of the IGFBP Superfamily

Insulin-Like Growth Factor-1 (IGF-1) and Its Monitoring in Medical Diagnostic and in Sports

Insulin-like growth factor-1 (IGF-1) is the principal mediator of growth hormone (GH), plays a crucial role in promoting cell growth and differentiation in childhood and continues to have an anabolic effect in adults. IGF-1 is part of a wide network of growth factors, receptors and binding proteins involved in mediating cellular proliferation, differentiation and apoptosis. Bioavailability of IGF-1 is affected by insulin-like growth factor binding proteins (IGFBPs) which bind IGF-1 in circulation with an affinity equal to or greater than that of the IGF-1 receptor (IGF-1R). The six IGFBPs serve as carrier proteins and bind approximately 98% of all circulating IGF-1. Other proteins known to bind IGF-1 include ten IGFBP-related proteins (IGFBP-rPs), albeit with lower affinities than the IGFBPs. IGF-1 expression levels vary in a number of clinical conditions suggesting it has the potential to provide crucial information as to the state of an individual’s health. IGF-1 is also a popular doping agent in sport and has featured in many high-profile doping cases in recent years. However, the existence of IGFBPs significantly reduces the levels of immunoreactive IGF-1 in samples, requiring multiple pre-treatment steps that reduce reproducibility and complicates interpretation of IGF-1 assay results. Here we provide an overview of the IGF network of growth factors, their receptors and the entirety of the extended family of IGFBPs, IGFBP-rPs, E peptides as well as recombinant IGF-1 and their derivatives. We also discuss issues related to the detection and quantification of bioavailable IGF-1.

CCN3 is dynamically regulated by treatment and disease state in multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is an immune-mediated disease that damages myelin in the central nervous system (CNS). We investigated the profile of CCN3, a known regulator of immune function and a potential mediator of myelin regeneration, in multiple sclerosis in the context of disease state and disease-modifying treatment.

METHODS

CCN3 expression was analysed in plasma, immune cells, CSF and brain tissue of MS patient groups and control subjects by ELISA, western blot, qPCR, histology and in situ hybridization.

RESULTS

Plasma CCN3 levels were comparable between collective MS cohorts and controls but were significantly higher in progressive versus relapsing-remitting MS and between patients on interferon-β versus natalizumab. Higher body mass index was associated with higher CCN3 levels in controls as reported previously, but this correlation was absent in MS patients. A significant positive correlation was found between CCN3 levels in matched plasma and CSF of MS patients which was absent in a comparator group of idiopathic intracranial hypertension patients. PBMCs and CD4+ T cells significantly upregulated CCN3 mRNA in MS patients versus controls. In the CNS, CCN3 was detected in neurons, astrocytes and blood vessels. Although overall levels of area immunoreactivity were comparable between non-affected, demyelinated and remyelinated tissue, the profile of expression varied dramatically.

CONCLUSIONS

This investigation provides the first comprehensive profile of CCN3 expression in MS and provides rationale to determine if CCN3 contributes to neuroimmunological functions in the CNS.

IGF-Binding Proteins, Adiponectin, and Survival in Metastatic Colorectal Cancer: Results From CALGB (Alliance)/SWOG 80405

Background

Energy balance-related biomarkers are associated with risk and prognosis of various malignancies. Their relationship to survival in metastatic colorectal cancer (mCRC) requires further study.

Methods

Baseline plasma insulin-like growth factor (IGF)-1, IGF-binding protein (IGFBP)-3, IGFBP-7, C-peptide, and adiponectin were measured at time of trial registration in a prospective cohort of patients with mCRC participating in a National Cancer Institute–sponsored trial of first-line systemic therapy. We used Cox proportional hazards regression to adjust for confounders and examine associations of each biomarker with overall survival (OS) and progression-free survival (PFS). P values are 2-sided.

Results

Median follow-up for 1086 patients was 6.2 years. Compared with patients in the lowest IGFBP-3 quintile, patients in the highest IGFBP-3 quintile experienced an adjusted hazard ratio (HR) for OS of 0.57 (95% confidence interval [CI] = 0.42 to 0.78; P_nonlinearity < .001) and for PFS of 0.61 (95% CI = 0.45 to 0.82; P_trend = .003). Compared with patients in the lowest IGFBP-7 quintile, patients in the highest IGFBP-7 quintile experienced an adjusted hazard ratio for OS of 1.60 (95% CI = 1.30 to 1.97; P_trend < .001) and for PFS of 1.38 (95% CI = 1.13 to 1.69; P_trend < .001). Plasma C-peptide and IGF-1 were not associated with patient outcomes. Adiponectin was not associated with OS; there was a nonlinear U-shaped association between adiponectin and PFS (P_nonlinearity = .03).

Conclusions

Among patients with mCRC, high plasma IGFBP-3 and low IGFBP-7 were associated with longer OS and PFS. Extreme levels of adiponectin were associated with shorter PFS. These findings suggest potential avenues for prognostic and therapeutic innovation.

Dynamic CCN3 expression in the murine CNS does not confer essential roles in myelination or remyelination

Remyelination is a natural regenerative process driven by oligodendrocytes that occurs following myelin damage. Understanding this process holds therapeutic value for demyelinating diseases such as multiple sclerosis, in which remyelination can fail. CCN3 is a matricellular protein previously reported to enhance oligodendrocyte progenitor differentiation and myelination in vitro and ex vivo. Here, we show that despite extensive and dynamic expression in the murine CNS in homeostasis and following toxin-induced myelin damage, CCN3 is not required for myelination or remyelination in vivo. Yet, the anatomically distinct expression pattern suggests unidentified roles of CCN3 in a range of neurological processes. This investigation provides a framework for future investigations of the expression and role of CCN proteins in the CNS.

CCN3 is a matricellular protein that promotes oligodendrocyte progenitor cell differentiation and myelination in vitro and ex vivo. CCN3 is therefore a candidate of interest in central nervous system (CNS) myelination and remyelination, and we sought to investigate the expression and role of CCN3 during these processes. We found CCN3 to be expressed predominantly by neurons in distinct areas of the CNS, primarily the cerebral cortex, hippocampus, amygdala, suprachiasmatic nuclei, anterior olfactory nuclei, and spinal cord gray matter. CCN3 was transiently up-regulated following demyelination in the brain of cuprizone-fed mice and spinal cord lesions of mice injected with lysolecithin. However, CCN3^−/− mice did not exhibit significantly different numbers of oligodendroglia or differentiated oligodendrocytes in the healthy or remyelinating CNS, compared to WT controls. These results suggest that despite robust and dynamic expression in the CNS, CCN3 is not required for efficient myelination or remyelination in the murine CNS in vivo.

Diabetes, Obesity, and Breast Cancer

The rates of obesity and diabetes are increasing worldwide, whereas the age of onset for both obesity and diabetes are decreasing steadily. Obesity and diabetes are associated with multiple factors that contribute to the increased risk of a number of different cancers, including breast cancer. These factors are hyperinsulinemia, elevated IGFs, hyperglycemia, dyslipidemia, adipokines, inflammatory cytokines, and the gut microbiome. In this review, we discuss the current understanding of the complex signaling pathways underlying these multiple factors involved in the obesity/diabetes-breast cancer link, with a focus particularly on the roles of the insulin/IGF system and dyslipidemia in preclinical breast cancer models. We review some of the therapeutic strategies to target these metabolic derangements in cancer. Future research directions and potential therapeutic strategies are also discussed.

Serum insulin-like growth factor (IGF)-I and IGF binding protein-3 in relation to terminal duct lobular unit involution of the normal breast in Caucasian and African American women: The Susan G. Komen Tissue Bank

Lesser degrees of terminal duct lobular unit (TDLU) involution, as reflected by higher numbers of TDLUs and acini/TDLU, are associated with elevated breast cancer risk. In rodent models, the insulin-like growth factor (IGF) system regulates involution of the mammary gland. We examined associations of circulating IGF measures with TDLU involution in normal breast tissues among women without precancerous lesions. Among 715 Caucasian and 283 African American (AA) women who donated normal breast tissue samples to the Komen Tissue Bank between 2009 and 2012 (75% premenopausal), serum concentrations of IGF-I and binding protein (IGFBP)-3 were quantified using enzyme-linked immunosorbent assay. Hematoxilyn and eosin-stained tissue sections were assessed for numbers of TDLUs ("TDLU count"). Zero-inflated Poisson regression models with a robust variance estimator were used to estimate relative risks (RRs) for association of IGF measures (tertiles) with TDLU count by race and menopausal status, adjusting for potential confounders. AA (vs. Caucasian) women had higher age-adjusted mean levels of serum IGF-I (137 vs. 131 ng/mL, p = 0.07) and lower levels of IGFBP-3 (4165 vs. 4684 ng/mL, p < 0.0001). Postmenopausal IGFBP-3 was inversely associated with TDLU count among AA (RR_T3vs.T1  = 0.49, 95% CI = 0.28-0.84, p-trend = 0.04) and Caucasian (RR_T3vs.T1 =0.64, 95% CI = 0.42-0.98, p-trend = 0.04) women. In premenopausal women, higher IGF-I:IGFBP-3 ratios were associated with higher TDLU count in Caucasian (RR_T3vs.T1 =1.33, 95% CI = 1.02-1.75, p-trend = 0.04), but not in AA (RR_T3vs.T1 =0.65, 95% CI = 0.42-1.00, p-trend = 0.05), women. Our data suggest a role of the IGF system, particularly IGFBP-3, in TDLU involution of the normal breast, a breast cancer risk factor, among Caucasian and AA women.

Role of Omentin, Vaspin, Cardiotrophin-1, TWEAK and NOV/CCN3 in Obesity and Diabetes Development

Adipose tissue releases bioactive mediators called adipokines. This review focuses on the effects of omentin, vaspin, cardiotrophin-1, Tumor necrosis factor-like Weak Inducer of Apoptosis (TWEAK) and nephroblastoma overexpressed (NOV/CCN3) on obesity and diabetes. Omentin is produced by the stromal-vascular fraction of visceral adipose tissue. Obesity reduces omentin serum concentrations and adipose tissue secretion in adults and adolescents. This adipokine regulates insulin sensitivity, but its clinical relevance has to be confirmed. Vaspin is produced by visceral and subcutaneous adipose tissues. Vaspin levels are higher in obese subjects, as well as in subjects showing insulin resistance or type 2 diabetes. Cardiotrophin-1 is an adipokine with a similar structure as cytokines from interleukin-6 family. There is some controversy regarding the regulation of cardiotrophin-1 levels in obese -subjects, but gene expression levels of cardiotrophin-1 are down-regulated in white adipose tissue from diet-induced obese mice. It also shows anti-obesity and hypoglycemic properties. TWEAK is a potential regulator of the low-grade chronic inflammation characteristic of obesity. TWEAK levels seem not to be directly related to adiposity, and metabolic factors play a critical role in its regulation. Finally, a strong correlation has been found between plasma NOV/CCN3 concentration and fat mass. This adipokine improves insulin actions.

Understanding the pathophysiology of postpartum psychosis: Challenges and new approaches

Postpartum psychosis is a severe psychiatric condition which affects 1-2 of every 1000 mothers shortly after childbirth. Whilst there is convincing evidence that the condition is precipitated by a complex combination of biological and environmental factors, as yet the pathophysiological mechanisms remain extremely poorly defined. Here, I critically review approaches that have been, or are being, employed to identify and characterise such mechanisms; I also review a recent animal model approach, and describe a novel biological risk model that it suggests. Clarification of biological risk mechanisms underlying disorder risk should permit the identification of relevant predictive biomarkers which will ensure that “at risk” subjects receive prompt clinical intervention if required.

Insulin-Like Growth Factor-1 Deficiency and Cirrhosis Establishment

Cirrhosis represents the final stage of chronic liver damage, which can be due to different factors such as alcohol, metabolic syndrome with liver steatosis, autoimmune diseases, drugs, toxins, and viral infection, among others. Nowadays, cirrhosis is an important health problem and it is an increasing cause of morbidity and mortality, being the 14th most common cause of death worldwide. The physiopathological pathways that lead to fibrosis and finally cirrhosis partly depend on the etiology. Nevertheless, some common features are shared in this complex mechanism. Recently, it has been demonstrated that cirrhosis is a dynamic process that can be altered in order to delay or revert fibrosis. In addition, when cirrhosis has been established, insulin-like growth factor-1 (IGF-1) deficiency or reduced availability is a common condition, independently of the etiology of chronic liver damage that leads to cirrhosis. IGF-1 deprivation seriously contributes to the progressive malnutrition of cirrhotic patient, increasing the vulnerability of the liver to establish an inflammatory and oxidative microenvironment with mitochondrial dysfunction. In this context, IGF-1 deficiency in cirrhotic patients can justify some of the common characteristics of these individuals. Several studies in animals and humans have been done in order to test the replacement of IGF-1 as a possible therapeutic option, with promising results.

Plasma NOV/CCN3 levels are closely associated with obesity in patients with metabolic disorders

OBJECTIVE

Evidence points to a founder of the multifunctional CCN family, NOV/CCN3, as a circulating molecule involved in cardiac development, vascular homeostasis and inflammation. No data are available on the relationship between plasma NOV/CCN3 levels and cardiovascular risk factors in humans. This study investigated the possible relationship between plasma NOV levels and cardiovascular risk factors in humans.

METHODS

NOV levels were measured in the plasma from 594 adults with a hyperlipidemia history and/or with lipid-lowering therapy and/or a body mass index (BMI) >30 kg/m(2). Correlations were measured between NOV plasma levels and various parameters, including BMI, fat mass, and plasma triglycerides, cholesterol, glucose, and C-reactive protein. NOV expression was also evaluated in adipose tissue from obese patients and rodents and in primary cultures of adipocytes and macrophages.

RESULTS

After full multivariate adjustment, we detected a strong positive correlation between plasma NOV and BMI (r = 0.36 p<0.0001) and fat mass (r = 0.33 p<0.0005). According to quintiles, this relationship appeared to be linear. NOV levels were also positively correlated with C-reactive protein but not with total cholesterol, LDL-C or blood glucose. In patients with drastic weight loss induced by Roux-en-Y bariatric surgery, circulating NOV levels decreased by 28% (p<0.02) and 48% (p<0.0001) after 3 and 6 months, respectively, following surgery. In adipose tissue from obese patients, and in human primary cultures NOV protein was detected in adipocytes and macrophages. In mice fed a high fat diet NOV plasma levels and its expression in adipose tissue were also significantly increased compared to controls fed a standard diet.

CONCLUSION

Our results strongly suggest that in obese humans and mice plasma NOV levels positively correlated with NOV expression in adipose tissue, and support a possible contribution of NOV to obesity-related inflammation.

Nov/Ccn3, a novel transcriptional target of FoxO1, impairs pancreatic β-cell function

Type 2 diabetes is characterized by both insulin resistance and progressive deterioration of β-cell function. The forkhead transcription factor FoxO1 is a prominent mediator of insulin signaling in β-cells. We reasoned that identification of FoxO1 target genes in β-cells could reveal mechanisms linking β-cell dysfunction to insulin resistance. In this study, we report the characterization of Nov/Ccn3 as a novel transcriptional target of FoxO1 in pancreatic β-cells. FoxO1 binds to an evolutionarily conserved response element in the Ccn3 promoter to regulate its expression. Accordingly, CCN3 levels are elevated in pancreatic islets of mice with overexpression of a constitutively active form of FoxO1 or insulin resistance. Our functional studies reveal that CCN3 impairs β-cell proliferation concomitantly with a reduction in cAMP levels. Moreover, CCN3 decreases glucose oxidation, which translates into inhibition of glucose-stimulated Ca²⁺ entry and insulin secretion. Our results identify CCN3, a novel transcriptional target of FoxO1 in pancreatic β-cells, as a potential target for therapeutic intervention in the treatment of diabetes.

CCN3 protein participates in bone regeneration as an inhibitory factor

CCN3, a member of the CCN protein family, inhibits osteoblast differentiation in vitro. However, the role of CCN3 in bone regeneration has not been well elucidated. In this study, we investigated the role of CCN3 in bone regeneration. We identified the Ccn3 gene by microarray analysis as a highly expressed gene at the early phase of bone regeneration in a mouse bone regeneration model. We confirmed the up-regulation of Ccn3 at the early phase of bone regeneration by RT-PCR, Western blot, and immunofluorescence analyses. Ccn3 transgenic mice, in which Ccn3 expression was driven by 2.3-kb Col1a1 promoter, showed osteopenia compared with wild-type mice, but Ccn3 knock-out mice showed no skeletal changes compared with wild-type mice. We analyzed the bone regeneration process in Ccn3 transgenic mice and Ccn3 knock-out mice by microcomputed tomography and histological analyses. Bone regeneration in Ccn3 knock-out mice was accelerated compared with that in wild-type mice. The mRNA expression levels of osteoblast-related genes (Runx2, Sp7, Col1a1, Alpl, and Bglap) in Ccn3 knock-out mice were up-regulated earlier than those in wild-type mice, as demonstrated by RT-PCR. Bone regeneration in Ccn3 transgenic mice showed no significant changes compared with that in wild-type mice. Phosphorylation of Smad1/5 was highly up-regulated at bone regeneration sites in Ccn3 KO mice compared with wild-type mice. These results indicate that CCN3 is up-regulated in the early phase of bone regeneration and acts as a negative regulator for bone regeneration. This study may contribute to the development of new strategies for bone regeneration therapy.

Cartilage-specific over-expression of CCN family member 2/connective tissue growth factor (CCN2/CTGF) stimulates insulin-like growth factor expression and bone growth

Previously we showed that CCN family member 2/connective tissue growth factor (CCN2) promotes the proliferation, differentiation, and maturation of growth cartilage cells in vitro. To elucidate the specific role and molecular mechanism of CCN2 in cartilage development in vivo, in the present study we generated transgenic mice overexpressing CCN2 and analyzed them with respect to cartilage and bone development. Transgenic mice were generated expressing a ccn2/lacZ fusion gene in cartilage under the control of the 6 kb-Col2a1-enhancer/promoter. Changes in cartilage and bone development were analyzed histologically and immunohistologically and also by micro CT. Primary chondrocytes as well as limb bud mesenchymal cells were cultured and analyzed for changes in expression of cartilage-related genes, and non-transgenic chondrocytes were treated in culture with recombinant CCN2. Newborn transgenic mice showed extended length of their long bones, increased content of proteoglycans and collagen II accumulation. Micro-CT analysis of transgenic bones indicated increases in bone thickness and mineral density. Chondrocyte proliferation was enhanced in the transgenic cartilage. In in vitro short-term cultures of transgenic chondrocytes, the expression of col2a1, aggrecan and ccn2 genes was substantially enhanced; and in long-term cultures the expression levels of these genes were further enhanced. Also, in vitro chondrogenesis was strongly enhanced. IGF-I and IGF-II mRNA levels were elevated in transgenic chondrocytes, and treatment of non-transgenic chondrocytes with recombinant CCN2 stimulated the expression of these mRNA. The addition of CCN2 to non-transgenic chondrocytes induced the phosphorylation of IGFR, and ccn2-overexpressing chondrocytes showed enhanced phosphorylation of IGFR. Our data indicates that the observed effects of CCN2 may be mediated in part by CCN2-induced overexpression of IGF-I and IGF-II. These findings indicate that CCN2-overexpression in transgenic mice accelerated the endochondral ossification processes, resulting in increased length of their long bones. Our results also indicate the possible involvement of locally enhanced IGF-I or IGF-II in this extended bone growth.

CCN3 modulates bone turnover and is a novel regulator of skeletal metastasis

The CCN family of proteins is composed of six secreted proteins (CCN1-6), which are grouped together based on their structural similarity. These matricellular proteins are involved in a large spectrum of biological processes, ranging from development to disease. In this review, we focus on CCN3, a founding member of this family, and its role in regulating cells within the bone microenvironment. CCN3 impairs normal osteoblast differentiation through multiple mechanisms, which include the neutralization of pro-osteoblastogenic stimuli such as BMP and Wnt family signals or the activation of pathways that suppress osteoblastogenesis, such as Notch. In contrast, CCN3 is known to promote chondrocyte differentiation. Given these functions, it is not surprising that CCN3 has been implicated in the progression of primary bone cancers such as osteosarcoma, Ewing’s sarcoma and chondrosarcoma. More recently, emerging evidence suggests that CCN3 may also influence the ability of metastatic cancers to colonize and grow in bone.

Kallikrein-related peptidase 12 hydrolyzes matricellular proteins of the CCN family and modifies interactions of CCN1 and CCN5 with growth factors

Kallikrein-related peptidases (KLKs) are an emerging group of secreted serine proteases involved in several physiological and pathological processes. We used a degradomic approach to identify potential substrates of KLK12. MDA-MB-231 cells were treated either with KLK12 or vehicle control, and the proteome of the overlying medium was analyzed by mass spectrometry. CCN1 (cyr61, ctgf, nov) was among the proteins released by the KLK12-treated cells, suggesting that KLK12 might be responsible for the shedding of this protein from the cell surface. Fragmentation of CCN1 by KLK12 was further confirmed in vitro, and the main cleavage site was localized in the hinge region between the first and second half of the recombinant protein. KLK12 can target all six members of the CCN family at different proteolytic sites. Limited proteolysis of CCNs (cyr61, ctgf, nov) was also observed in the presence of other members of the KLK family, such as KLK1, KLK5, and KLK14, whereas KLK6, KLK11, and KLK13 were unable to fragment CCNs. Because KLK12 seems to have a role in angiogenesis, we investigated the relations between KLK12, CCNs, and several factors known to be involved in angiogenesis. Solid phase binding assays showed that fragmentation of CCN1 or CCN5 by KLK12 prevents VEGF(165) binding, whereas it also triggers the release of intact VEGF and BMP2 from the CCN complexes. The KLK12-mediated release of TGF-β1 and FGF-2, either as intact or truncated forms, was found to be concentration-dependent. These findings suggest that KLK12 may indirectly regulate the bioavailability and activity of several growth factors through processing of their CCN binding partners.

A novel role of CCN3 in regulating endothelial inflammation

The vascular endothelium plays a fundamental role in the health and disease of the cardiovascular system. The molecular mechanisms regulating endothelial homeostasis, however, remain incompletely understood. CCN3, a member of the CCN (Cyr61, Ctgf, Nov) family of cell growth and differentiation regulators, has been shown to play an important role in numerous cell types. The function of CCN3 in endothelial cells has yet to be elucidated. Immunohistochemical analysis of CCN3 expression in mouse tissues revealed robust immunoreactivity in the endothelium of large arteries, small resistance vessels, and veins. We found that CCN3 expression in human umbilical vein endothelial cells (HUVECs) is transcriptionally induced by laminar shear stress (LSS) and HMG CoA-reductase inhibitors (statins). Promoter analyses identified the transcription factor Kruppel-like factor 2 (KLF2) as a direct regulator of CCN3 expression. In contrast to LSS, proinflammatory cytokines reduced CCN3 expression. Adenoviral overexpression of CCN3 in HUVEC markedly inhibited the cytokine-mediated induction of vascular adhesion molecule-1 (VCAM-1). Consistent with this observation, CCN3 significantly reduced monocyte adhesion. Conversely, CCN3 knockdown in HUVECs resulted in enhancement of cytokine-induced VCAM-1 expression. Concordant effects were observed on monocyte adhesion. Gain and loss-of-function mechanistic studies demonstrated that CCN3 negatively regulates nuclear factor kappaB (NF-κB) activity by reducing its translocation into the nucleus and subsequent binding to the VCAM-1 promoter, suggesting that CCN3's anti-inflammatory effects occur secondary to inhibition of NF-κB nuclear accumulation. This study identifies CCN3 as a novel regulator of endothelial proinflammatory activation.

Domain-specific CCN3 antibodies as unique tools for structural and functional studies

CCN3 is a member of the CCN family of cell growth and differentiation regulators that play key roles during embryonic development, and are associated with severe human pathologies. The level of CCN genes' expression is of prognostic value in several types of tumors. In the present manuscript, we report the isolation and characterization of a new set of antibodies targeted against each individual module of the human CCN3 protein. The need for module-specific antibodies stemmed from recent reports indicating that the expression of truncated CCN variant proteins was associated with development of cancers. Each of the four CCN3 modules were expressed as GST fusion proteins and used for rabbits immunization. Polyclonal IgGs purified by two rounds of affinity-chromatography specifically detected both the individual CCN3 domains and the full length CCN3 protein expressed in mammalian cell lines and tissues, as well as recombinant full length and truncated CCN3 proteins. The purified module-specific antibodies were successfully used for Western blotting, immunoprecipitation, immunofluorescence and immunocytochemistry. These antibodies permitted the detection of CCN3 proteins under native and denaturing conditions, and confirmed the sublocalisation of CCN3 proteins in the extracellular compartment, at the cell membrane, in the cytoplasm and in the nucleus of positive cells. Immunocytochemistry and Western blotting studies performed with the module-specific antibodies identified truncated CCN3 proteins in kidney tumor samples. The detection of these rearranged variants provides clues for their involvement in tumorigenesis. Therefore, these antibodies constitute unique tools for the identification of truncated CCN3 proteins in human tissues and may be of great interest in molecular medicine.

WISP3 (CCN6) is a secreted tumor-suppressor protein that modulates IGF signaling in inflammatory breast cancer

Inflammatory breast cancer (IBC) is the most lethal form of locally advanced breast cancer. We have found that WISP3 is lost in 80% of human IBC tumors and that it has growth- and angiogenesis-inhibitory functions in breast cancer in vitro and in vivo. WISP3 is a cysteine-rich, putatively secreted protein that belongs to the CCN family. It contains a signal peptide at the N-terminus and four highly conserved motifs. Here, for the first time, we investigate the function of WISP3 protein in relationship to its structural features. We found that WISP3 is secreted into the conditioned media and into the lumens of normal breast ducts. Once secreted, WISP3 was able to decrease, directly or through induction of other molecule(s), the IGF-1-induced activation of the IGF-IR, and two of its main downstream signaling molecules, IRS1 and ERK-1/2, in SUM149 IBC cells. Furthermore, WISP3 containing conditioned media decreased the growth rate of SUM149 cells. This work sheds light into the mechanism of WISP3 function by demonstrating that it is secreted and that, once in the extracellular media, it induces a series of molecular events that leads to modulation of IGF-IR signaling pathways and cellular growth in IBC cells.

Potential cellular conformations of the CCN3(NOV) protein

Aim

To study the cellular distribution of CCN3(NOV) and to determine if the carboxyterminus of CCN3 is hidden or masked due to high affinity interactions with other partners. CCN3 was detected using affinity purified antibodies (anti-K19M-AF) as well as a Protein A purified anti-K19M antibodies (anti-K19M IgG) against a C-terminal 19-aminoacid peptide (K19M) of human CCN3 protein. The antibodies were applied in indirect immunofluorescence tests and immunoenzyme assays on glial tumor cell line, G59, and its CCN3-transfected variant G59/540 and the adrenocortical cell line, NCI-H295R.

Results

Anti-K19M-AF antibodies reacted against K19M peptide in ELISA and recognized two bands of 51 kDa and 30 kDa in H295R (adrenocortical carcinoma) cell culture supernatants by immunoblotting. H295R culture supernatants which contained CCN3 as shown by immunoblotting did not react with anti-CCN3 antibodies in liquid phase. Anti-CCN3 antibodies stained the surface membranes of non-permeabilized H295R and cytoplasm in permeabilized H295R cells. Similarly, anti-CCN3 stained surface membranes of G59/540, but did not react with G59 cells. Prominent cytoplasmic staining was observed in G59/540, as well as the cell footprints of G59/540 and H295R were strongly labeled.

Conclusions

The K19M-AF antibody directed against the C-terminal 19-aminoacid peptide of CCN3 recognized the secreted protein under denaturing conditions. However, the C-terminal motif of secreted CCN3 was not accessible to K19M-AF in liquid phase. These anti-CCN3 antibodies stained CCN3 protein which was localized to cytoplasmic stores, cell membranes and extracellular matrix. This would suggest that cytoplasmic and cell membrane bound CCN3 has an exposed C-terminus while secreted CCN3 has a sequestered C-terminus which could be due to interaction with other proteins or itself (dimerization). Thus the K19M-AF antibodies revealed at least two conformational states of the native CCN3 protein.

A structural approach to the role of CCN (CYR61/CTGF/NOV) proteins in tumourigenesis

The CCN (CYR61 [Cystein-rich61]/CTGF [connective tissue growth factor]/NOV [Nephroblastoma overexpressed]) proteins constitute a family of regulatory factors involved in many aspects of cell proliferation and differentiation. An increasing body of evidence indicates that abnormal expression of the CCN proteins is associated to tumourgenesis. The multimodular architecture of the CCN proteins, and the production of truncated isoforms in tumours, raise interesting questions regarding the participation of each individual module to the various biological properties of these proteins. In this article, we review the current data regarding the involvement of CCN proteins in tumourigenesis. We also attempt to provide structural basis for the stimulatory and inhibitory functions of the full length and truncated CCN proteins that are expressed in various tumour tissues.

CCN3 and calcium signaling

The CCN family of genes consists presently of six members in human (CCN1-6) also known as Cyr61 (Cystein rich 61), CTGF (Connective Tissue Growth Factor), NOV (Nephroblastoma Overexpressed gene), WISP-1, 2 and 3 (Wnt-1 Induced Secreted Proteins). Results obtained over the past decade have indicated that CCN proteins are matricellular proteins, which are involved in the regulation of various cellular functions, such as proliferation, differentiation, survival, adhesion and migration. The CCN proteins have recently emerged as regulatory factors involved in both internal and external cell signaling. CCN3 was reported to physically interact with fibulin-1C, integrins, Notch and S100A4. Considering that, the conformation and biological activity of these proteins are dependent upon calcium binding, we hypothesized that CCN3 might be involved in signaling pathways mediated by calcium ions.

In this article, we review the data showing that CCN3 regulates the levels of intracellular calcium and discuss potential models that may account for the biological effects of CCN3.

Differential expression of the ccn3 (nov) proto-oncogene in human prostate cell lines and tissues

AIMS

To investigate the expression of the human ccn3 (hccn3; nov) proto-oncogene, a member of the CCN family of proteins, in prostate epithelial cells and prostate tissue samples.

METHODS

Normal adult prostate luminal epithelial cells immortalised by SV40 large T (PNT1A and PNT1B), metastatic tumours (LNCaP, DU-145, and PC-3), and prostate tissue samples from patients with benign prostatic hyperplasia (BPH) and prostatic adenocarcinoma were used. hccn3 (nov) mRNA was measured by the reverse transcription polymerase chain reaction (RT-PCR) and hCCN3 (NOV) protein expression was determined by immunochemistry.

RESULTS

hccn3 (nov) RNA values were higher in PC-3 cells than in the other prostate cell lines. The immortalised normal cell lines either did not express hccn3 (nov) RNA (PNT1B) or expressed very low amounts (PNT1A). BPH samples expressed variable amounts of hccn3 (nov) RNA. With the use of immunocytochemistry, all cell lines except PNT1A and PNT1B were shown to contain hCCN3 (NOV) protein. hCCN3 (NOV) was localised mainly in the epithelial compartment of BPH and adenocarcinoma samples, and there was evidence of luminal secretion.

CONCLUSION

The overexpression of hccn3 (nov) RNA in cancer cell lines compared with other cell lines and its epithelial localisation in human prostate samples are consistent with a role for hCCN3 (NOV) in prostatic tumorigenesis.

The expression of ccn3 (nov) RNA and protein in the rat central nervous system is developmentally regulated

AIMS

To establish the expression pattern of ccn3 (nov) in the central nervous system (CNS) of adult rats and to determine whether spatiotemporal variations in the expression of ccn3 (nov) are related to specific developmental stages and/or specific CNS functions.

METHODS

The sites of ccn3 (nov) expression have been identified by in situ hybridisation using didoxigenin labelled cRNA and by the reverse transcription-polymerase chain reaction (RT-PCR). The rat CCN3 (NOV) protein was characterised by western blotting performed on brain extracts. The localisation of the CCN3 (NOV) protein in the brain was established by immunocytochemistry.

RESULTS

Increased expression of ccn3 (nov) was detected in the developing brain of rats after birth, as shown by RT-PCR and immunocytochemistry analysis performed on a series of samples taken between day 5 (P5) and day 300 (P300), with a pronounced peak between P15 and P150, suggesting that CCN3 (NOV) might play a role in the maintenance or establishment of specific brain functions. The relatively high amounts of an N-terminal truncated CCN3 (NOV) related protein detected both in the brain tissues and cerebrospinal fluid suggested that post translational processing of CCN3 (NOV) might be particularly prevalent in the brain. Such processing might be of biological importance in the light of the previously reported growth stimulatory effects of N-terminal truncated CCN3 (NOV) isoforms.

CONCLUSIONS

The postnatal differential expression of ccn3 (nov) in the brain of developing rats suggests that CCN3 (NOV) might be involved in the acquisition of specific functions. The rat species provides an as yet unequalled system for these studies. Because the CCN3 (NOV) protein is detected in restricted areas of the brain, it will be interesting to establish whether variations of ccn3 (nov) expression are associated with normal cognitive processes and whether ccn3 (nov) expression is affected by aging. In addition, because CCN3 (NOV) is found in the spinal cord and along the axonal processes, it will be of interest to determine the expression of the normal and truncated isoforms of CCN3 (NOV) in various pathological conditions, such as neurodegenerative diseases.

NOV (nephroblastoma overexpressed) and the CCN family of genes: structural and functional issues

The CCN family of genes presently consists of six distinct members encoding proteins that participate in fundamental biological processes such as cell proliferation, attachment, migration, differentiation, wound healing, angiogenesis, and several pathologies including fibrosis and tumorigenesis. Whereas CYR61 and CTGF were reported to act as positive regulators of cell growth, NOV (nephroblastoma overexpressed) provided the first example of a CCN protein with negative regulatory properties and the first example of aberrant expression being associated with tumour development. The subsequent discovery of the ELM1, rCOP1, and WISP proteins has broadened the variety of functions attributed to the CCN proteins and has extended previous observations to other biological systems. This review discusses fundamental questions regarding the regulation of CCN gene expression in normal and pathological conditions, and the structural basis for their specific biological activity. After discussing the role of nov and other CCN proteins in the development of a variety of different tissues such as kidney, nervous system, muscle, cartilage, and bone, the altered expression of the CCN proteins in various pathologies is discussed, with an emphasis on the altered expression of nov in many different tumour types such as Wilms's tumour, renal cell carcinomas, prostate carcinomas, osteosarcomas, chondrosarcomas, adrenocortical carcinomas, and neuroblastomas. The possible use of nov as a tool for molecular medicine is also discussed. The variety of biological functions attributed to the CCN proteins has led to the proposal of a model in which physical interactions between the amino and carboxy portions of the CCN proteins modulate their biological activity and ensure a proper balance of positive and negative signals through interactions with other partners. In this model, disruption of the secondary structure of the CCN proteins induced by deletions of either terminus is expected to confer on the truncated polypeptide constitutive positive or negative activities.

CTGF (IGFBP-rP2) is specifically expressed in malignant lymphoblasts of patients with acute lymphoblastic leukaemia (ALL)

Connective tissue growth factor (CTGF) is a major chemotactic and mitogenic factor for connective tissue cells. The amino acid sequence shares an overall 28-38% identity to IGFBPs and contains critical conserved sequences in the amino terminus. It has been demonstrated that human CTGF specifically binds IGFs with low affinity and is considered to be a member of the IGFBP superfamily (IGFBP-rP2). In the present study, the expression of CTGF (IGFBP-rP2) in human leukaemic lymphoblasts from children with acute lymphoblastic leukaemia (ALL) was investigated. RNA samples from tumour clones enriched by ficoll separation of bone marrow or peripheral blood mononuclear cells (MNC) from 107 patients with childhood ALL at diagnosis and 57 adult patients with chronic myeloid leukaemia (CML) were studied by RT-PCR. In addition MNC samples from children with IDDM and cord blood samples from healthy newborns were investigated as control groups. Sixty-one percent of the patients with ALL (65 of 107) were positive for CTGF (IGFBP-rP2) expression. In the control groups, no expression of CTGF (IGFBP-rP2) in peripheral MNC was detected, and in the group of adult CML patients only 3.5% (2 of 57) were positive for this gene. The role of CTGF (IGFBP-rP2) in lymphoblastic leukaemogenesis requires further evaluation, as does its potential utility as a tumour marker.