CCN5 modulates the antiproliferative effect of heparin and regulates cell motility in vascular smooth muscle cells

CCN proteins: opportunities for clinical studies-a personal perspective

The diverse members of the CCN family now designated as CCN1(CYR61), CCN2 (CTGF), CCN3(NOV), CCN4(WISP1), CCN5(WISP2), CCN6(WISP3) are a conserved matricellular family of proteins exhibiting a spectrum of functional properties throughout all organs in the body. Interaction with cell membrane receptors such as integrins trigger intracellular signaling pathways. Proteolytically cleaved fragments (constituting the active domains) can be transported to the nucleus and perform transcriptional relevant functional activities. Notably, as also found in other protein families some members act opposite to others creating a system of functionally relevant checks and balances. It has become apparent that these proteins are secreted into the circulation, are quantifiable, and can serve as disease biomarkers. How they might also serve as homeostatic regulators is just becoming appreciated. In this review I have attempted to highlight the most recent evidence under the subcategories of cancer and non-cancer relevant that could lead to potential therapeutic approaches or ideas that can be factored into clinical advances. I have added my own personal perspective on feasibility.

The role of CCNs in controlling cellular communication in the tumor microenvironment

The Cellular communication network (CCN) family of growth regulatory factors comprises six secreted matricellular proteins that promote signal transduction through cell-cell or cell-matrix interaction. The diversity of functionality between each protein is specific to the many aspects of healthy and cancer biology. For example, CCN family proteins modulate cell adhesion, proliferation, migration, invasiveness, apoptosis, and survival. In addition, the expression of each protein regulates many biological and pathobiological processes within its microenvironment to regulate angiogenesis, inflammatory response, chondrogenesis, fibrosis, and mitochondrial integrity. The collective range of CCN operation remains fully comprehended; however, understanding each protein's microenvironment may draw more conclusions about the abundance of interactions and signaling cascades occurring within such issues. This review observes and distinguishes the various roles a CCN protein may execute within distinct tumor microenvironments and the biological associations among them. Finally. We also review how CCN-family proteins can be used in nano-based therapeutic implications.

Suppression of choroidal neovascularization and epithelial-mesenchymal transition in retinal pigmented epithelium by adeno-associated virus-mediated overexpression of CCN5 in mice

Choroidal neovascularization (CNV) is a defining characteristic feature of neovascular age-related macular degeneration (nAMD) that frequently results in irreversible vision loss. The current strategies for the treatment of nAMD are mainly based on neutralizing vascular endothelial growth factor (VEGF). However, anti-VEGF therapies are often associated with subretinal fibrosis that eventually leads to damages in macula. In this study, we tested whether an anti-fibrotic and anti-angiogenic protein CCN5 can potentially be an effective and safe therapeutic modality in a mouse model of CNV. Laser photocoagulation was utilized to induce CNV, which was followed by intravitreal injection of recombinant adeno-associated virus serotype 2 encoding CCN5 (rAAV2-CCN5). Our data demonstrated that rAAV2-CCN5, but not a control viral vector, rAAV2-VLP, prominently attenuated both CNV lesions and angiogenesis. Aflibercept, which was utilized as a positive control, exhibited similar effects on CNV lesions and angiogenesis in our experimental settings. Upon laser photocoagulation, retinal pigmented epithelium (RPE) cells underwent significant morphological changes including cellular enlargement and loss of hexagonality. rAAV2-CCN5 significantly normalized these morphological defects. Laser photocoagulation also led to fibrotic deformation in RPE cells through inducing epithelial-mesenchymal transition (EMT), which was completely blocked by rAAV2-CCN5. In a striking contrast, aflibercept as well as rAAV2-VLP failed to exhibit any effects on EMT. Collectively, this study suggest that CCN5 might provide a potential novel strategy for the treatment of nAMD with a capability to inhibit CNV and fibrosis simaultaneously.

CCN5 inhibits proliferation and promotes apoptosis of oral squamous cell carcinoma cells

Oral squamous cell carcinoma (OSCC) is a common cancer with poor prognosis and high mortality. The role of CCN5 has attracted a great focus on the regulation of cancer progression. However, the biological function and mechanism of CCN5 in OSCC are still not well elucidated. The current study was designed to determine the effects of CCN5 on OSCC cell proliferation and apoptosis using two OSCC cell lines. Further, LY294002, a PI3K/AKT antagonist, was employed to explore the mechanism underlying the effects of CCN5 in the regulation of OSCC. The results showed that overexpression of CCN5 in TSCCa cells significantly reduced viable cell number, arrested cell cycle, and suppressed cell-cycle regulators (cyclin D1, cyclin E, and CDK2). CCN5 overexpression increased the apoptotic ratio and Hoechst-positive cell number, and altered the apoptotic-related proteins (caspase-3/9, Bax, and Bcl-2). However, CCN5 silencing induced opposite effects on cell proliferation and apoptosis in Tca-8113 cells. In addition, we observed that CCN5 knockdown increased the expression levels of PI3K (p85α and p110α) and phosphorylated AKT at serine 473 (p-AKT Ser473) in Tca-8113 cells. Inhibiting PI3K/AKT signaling with LY294002 rescued the apoptotic process in CCN5-silenced OSCC cells. Finally, xenograft analysis showed that CCN5 represses tumorigenesis of OSCC cells. These findings together suggest that CCN5 functions as a tumor suppressor for OSCC cell development through inactivation of PI3K/AKT signaling pathway, providing a potential candidate for OSCC therapy.

Functional Vascular Tissue Engineering Inspired by Matricellular Proteins

Modern regenerative medicine, and tissue engineering specifically, has benefited from a greater appreciation of the native extracellular matrix (ECM). Fibronectin, collagen, and elastin have entered the tissue engineer's toolkit; however, as fully decellularized biomaterials have come to the forefront in vascular engineering it has become apparent that the ECM is comprised of more than just fibronectin, collagen, and elastin, and that cell-instructive molecules known as matricellular proteins are critical for desired outcomes. In brief, matricellular proteins are ECM constituents that contrast with the canonical structural proteins of the ECM in that their primary role is to interact with the cell. Of late, matricellular genes have been linked to diseases including connective tissue disorders, cardiovascular disease, and cancer. Despite the range of biological activities, this class of biomolecules has not been actively used in the field of regenerative medicine. The intent of this review is to bring matricellular proteins into wider use in the context of vascular tissue engineering. Matricellular proteins orchestrate the formation of new collagen and elastin fibers that have proper mechanical properties-these will be essential components for a fully biological small diameter tissue engineered vascular graft (TEVG). Matricellular proteins also regulate the initiation of thrombosis via fibrin deposition and platelet activation, and the clearance of thrombus when it is no longer needed-proper regulation of thrombosis will be critical for maintaining patency of a TEVG after implantation. Matricellular proteins regulate the adhesion, migration, and proliferation of endothelial cells-all are biological functions that will be critical for formation of a thrombus-resistant endothelium within a TEVG. Lastly, matricellular proteins regulate the adhesion, migration, proliferation, and activation of smooth muscle cells-proper control of these biological activities will be critical for a TEVG that recellularizes and resists neointimal formation/stenosis. We review all of these functions for matricellular proteins here, in addition to reviewing the few studies that have been performed at the intersection of matricellular protein biology and vascular tissue engineering.

Aging differentially modulates the Wnt pro-survival signalling pathways in vascular smooth muscle cells

We previously reported pro-survival effects of Wnt3a and Wnt5a proteins in vascular smooth muscle cells (VSMCs). Wnt5a achieved this through induction of Wnt1-inducible signalling pathway protein-1 (WISP-1) consequent to β-catenin/CREB-dependent, TCF-independent, signalling. However, we found that as atherosclerosis advances, although Wnt5a protein was increased, WISP-1 was reduced. We hypothesized this disconnect could be due to aging. In this study, we elucidate the mechanism underlying Wnt3a pro-survival signalling and demonstrate the differential effect of age on Wnt3a- and Wnt5a-mediated survival. We show Wnt3a protein was expressed in human atherosclerotic coronary arteries and co-located with macrophages and VSMCs. Meanwhile, Wnt3a stimulation of primary mouse VSMCs increased β-catenin nuclear translocation and TCF, but not CREB, activation. Wnt3a increased mRNA expression of the pro-survival factor WISP-2 in a TCF-dependent manner. Functionally, β-catenin/TCF inhibition or WISP-2 neutralization significantly impaired Wnt3a-mediated VSMC survival. WISP-2 was upregulated in human atherosclerosis and partly co-localized with Wnt3a. The pro-survival action of Wnt3a was effective in VSMCs from young (2 month) and old (18-20 month) mice, whereas Wnt5a-mediated rescue was impaired with age. Further investigation revealed that although Wnt5a induced β-catenin nuclear translocation in VSMCs from both ages, CREB phosphorylation and WISP-1 upregulation did not occur in old VSMCs. Unlike Wnt5a, pro-survival Wnt3a signalling involves β-catenin/TCF and WISP-2. While Wnt3a-mediated survival was unchanged with age, Wnt5a-mediated survival was lost due to impaired CREB activation and WISP-1 regulation. Greater understanding of the effect of age on Wnt signalling may identify targets to promote VSMC survival in elderly patients with atherosclerosis.

The matricellular protein CCN5 inhibits fibrotic deformation of retinal pigment epithelium

Retinal pigment epithelium (RPE) plays an essential role in maintaining retinal function, and its defect is thought to be critically implicated in various ocular disorders. This study demonstrated that the matricellular protein CCN5 was down-regulated in ARPE-19 cells treated with the pro-fibrotic agent transforming growth factor (TGF)-β. A recombinant adenovirus expressing CCN5 (AdCCN5) was used to restore the level of CCN5 in these cells. AdCCN5 prevented TGF-β-induced fibrotic changes, including disruption of tight junctions, up-regulation of mesenchymal marker proteins, and down-regulation of epithelial marker proteins. In addition, AdCCN5 prevented TGF-β-induced functional defects, including increased migratory activity and reduced phagocytic activity. Notably, AdCCN5 reversed morphological and functional defects pre-established by TGF-β prior to viral infection. The CCN5 level was down-regulated in RPE of 18-month-old Ccl2-/- mice, which exhibited retinal defects. Restoration of the CCN5 level via intravitreal injection of a recombinant adeno-associated virus expressing CCN5 (AAV9-CCN5) normalized the altered expression of mesenchymal, epithelial, and functional marker proteins, as assessed by western blotting and immunohistochemistry. Taken together, these data suggest that down-regulation of CCN5 is associated with fibrotic deformation of RPE under pathological conditions and that restoration of the CCN5 level effectively promotes recovery of deformed RPE.

CCN5 in alveolar epithelial proliferation and differentiation during neonatal lung oxygen injury

Lung immaturity is the major cause of morbidity and mortality in premature infants, especially those born <28 weeks of gestation. These infants are at high risk of developing respiratory distress syndrome (RDS), a lung disease caused by insufficient surfactant production and immaturity of saccular/alveolar type II epithelial cells in the lung. RDS treatment includes oxygen and respiratory support that improve survival but also increase the risk for bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by arrested alveolarization, airway hyperreactivity, and pulmonary hypertension. The mechanisms regulating normal alveolar development and how injury disrupts normal development to cause BPD are not well understood. We examined the role of the matricellular protein CCN5 (Cysteine-rich protein 61/Connective tissue growth factor/Nephroblastoma-overexpressed protein) in the development of BPD. Cultured non-proliferating alveolar type II cells expressed low levels of CCN5 protein, and displayed higher levels during proliferation. siRNA targeting of CCN5 reduced alveolar type II cell proliferation and migration in cell culture. In a mouse model of hyperoxia-induced BPD, CCN5 protein was increased only in proliferating alveolar type I cells. Alveolar epithelial cells co-expressing markers of type II cells and type I cells also appeared. The results suggest that hyperoxic injury in immature lungs induces proliferation of type I cells and trans-differentiation of type II cells into type I cells. We propose that the mechanism of the injury response in BPD includes CCN5 expression. Study of CCN5 in neonatal alveolar injury will further our understanding of BPD pathophysiology while providing a mechanistic foundation for therapeutic approaches.

Detection of CCN1 and CCN5 mRNA in Human Cancer Samples Using a Modified In Situ Hybridization Technique

In situ hybridization is an ideal tool for the detection and localization of mRNA expression of specific gene(s) in tissue sections and cell lines for prognosis, predictive markers, and highlighted potential therapeutic targets. Given the importance of CCN1 and CCN5 in breast and pancreatic cancer progression, these two secretory proteins could be novel therapeutic targets. Thus, evaluating the distribution of mRNA of these targets using in situ hybridization could be important preclinical tools. This chapter describes a detailed in situ hybridization technique for the detection of CCN1 and CCN5 in formalin-fixed, paraffin-embedded patient samples of breast and pancreatic cancers.

Human pancreatic cancer progression: an anarchy among CCN-siblings

Decades of basic and translational studies have identified the mechanisms by which pancreatic cancer cells use molecular pathways to hijack the normal homeostasis of the pancreas, promoting pancreatic cancer initiation, progression, and metastasis, as well as drug resistance. These molecular pathways were explored to develop targeted therapies to prevent or cure this fatal disease. Regrettably, the studies found that majority of the molecular events that dictate carcinogenic growth in the pancreas are non-actionable (potential non-responder groups of targeted therapy). In this review we discuss exciting discoveries on CCN-siblings that reveal how CCN-family members contribute to the different aspects of the development of pancreatic cancer with special emphasis on therapy.

Degradomic and yeast 2-hybrid inactive catalytic domain substrate trapping identifies new membrane-type 1 matrix metalloproteinase (MMP14) substrates: CCN3 (Nov) and CCN5 (WISP2)

Members of the CCN family of matricellular proteins are cytokines linking cells to the extracellular matrix. We report that CCN3 (Nov) and CCN5 (WISP2) are novel substrates of MMP14 (membrane-type 1-matrix metalloproteinase, MT1-MMP) that we identified using MMP14 "inactive catalytic domain capture" (ICDC) as a yeast two-hybrid protease substrate trapping platform in parallel with degradomics mass spectrometry screens for MMP14 substrates. CCN3 and CCN5, previously unknown substrates of MMPs, were biochemically validated as substrates of MMP14 and other MMPs in vitro-CCN5 was processed in the variable region by MMP14 and MMP2, as well as by MMP1, 3, 7, 8, 9 and 15. CCN1, 2 and 3 are proangiogenic factors yet we found novel opposing activity of CCN5 that was potently antiangiogenic in an aortic ring vessel outgrowth model. MMP14, a known regulator of angiogenesis, cleaved CCN5 and abrogated the angiostatic activity. CCN3 was also processed in the variable region by MMP14 and MMP2, and by MMP1, 8 and 9. In addition to the previously reported cleavages of CCN1 and CCN2 by several MMPs we found that MMPs 8, 9, and 1 process CCN1, and MMP8 and MMP9 also process CCN2. Thus, our study reveals additional and pervasive family-wide processing of CCN matricellular proteins/cytokines by MMPs. Furthermore, CCN5 cleavage by proangiogenic MMPs results in removal of an angiogenic brake held by CCN5. This highlights the importance of thorough dissection of MMP substrates that is needed to reveal higher-level control mechanisms beyond type IV collagen and other extracellular matrix protein remodelling in angiogenesis.

SUMMARY

We find CCN family member cleavage by MMPs is more pervasive than previously reported and includes CCN3 (Nov) and CCN5 (WISP2). CCN5 is a novel antiangiogenic factor, whose function is abrogated by proangiogenic MMP cleavage. By processing CCN proteins, MMPs regulate cell responses angiogenesis in connective tissues.

Emerging roles of CCN proteins in vascular development and pathology

The CCN family of proteins consists of 6 members (CCN1-CCN6) that share conserved functional domains. These matricellular proteins interact with growth factors, extracellular matrix (ECM) proteins, cell surface integrins and other receptors to promote ECM-intracellular signaling. This signaling leads to propagation of a variety of cellular actions, including adhesion, invasion, migration and proliferation within several cell types, including epithelial, endothelial and smooth muscle cells. Though CCNs share significant homology, the function of each is unique due to distinct and cell specific expression patterns. Thus, their correct spatial and temporal expressions are critical during embryonic development, wound healing, angiogenesis and fibrosis. Disruption of these patterns leads to severe development disorders and contributes to the pathological progression of cancers, vascular diseases and chronic inflammatory diseases such as colitis, rheumatoid arthritis and atherosclerosis. While the effects of CCNs are diverse, this review will focus on the role of CCNs within the vasculature during development and in vascular diseases.

CCN2 and CCN5 exerts opposing effect on fibroblast proliferation and transdifferentiation induced by TGF-β

Epidural fibrosis might occur after lumbar discectomy and contributes to failed back syndrome. Transforming growth factor (TGF)-β has been reported to influence multiple organ fibrosis, in which connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed 2 (CCN2) and CCN5 are involved. However, the effect of CCN2 and CCN5 on TGF-β induced fibrosis has not yet been elucidated. This study reports that CCN2 and CCN5 play opposing roles in cell proliferation and transdifferentiation of human skin fibroblasts or rabbit epidural scar-derived fibroblasts exposed to TGF-β. We observed that TGF-β1 induced fibroblasts proliferation and differentiation in a dose-dependent manner (from 0 μg/L to 20 μg/L). Meanwhile, CCN2 expression is up-regulated while CCN5 expression is inhibited by TGF-β1 exposure. Furthermore, it is demonstrated that CCN2 overexpression leads to promoted proliferation and elevated collagen and α-smooth muscle actin (α-SMA) expression, which are inhibited by CCN5 overexpression. Moreover, it is shown that the cysteine knot (CT) domain, present in CCN2 but absent in CCN5, plays an essential part in fibroblast proliferation and differentiation. Additionally, enhanced TGF-β and CCN2 expression but decreased CCN5 expression is found in rabbit epidural scar-derived fibroblasts. Overall, the results show the opposing effects of CCN2 and CCN5 on fibroblast proliferation and transdifferentiation induced by TGF-β.

CCN: core regulatory proteins in the microenvironment that affect the metastasis of hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) results from an underlying chronic liver inflammatory disease, such as chronic hepatitis B or C virus infections, and the general prognosis of patients with HCC still remains extremely dismal because of the high frequency of HCC metastases. Throughout the process of tumor metastasis, tumor cells constantly communicate with the surrounding microenvironment and improve their malignant phenotype. Therefore, there is a strong rationale for targeting the tumor microenvironment as primary treatment of HCC therapies. Recently, CCN family proteins have emerged as localized multitasking signal integrators in the inflammatory microenvironment. In this review, we summarize the current knowledge of CCN family proteins in inflammation and the tumor. We also propose that the CCN family proteins may play a central role in signaling the tumor microenvironment and regulating the metastasis of HCC.

Emerging role of CCN family proteins in tumorigenesis and cancer metastasis (Review)

The CCN family of proteins comprises the members CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6. They share four evolutionarily conserved functional domains, and usually interact with various cytokines to elicit different biological functions including cell proliferation, adhesion, invasion, migration, embryonic development, angiogenesis, wound healing, fibrosis and inflammation through a variety of signalling pathways. In the past two decades, emerging functions for the CCN proteins (CCNs) have been identified in various types of cancer. Perturbed expression of CCNs has been observed in a variety of malignancies. The aberrant expression of certain CCNs is associated with disease progression and poor prognosis. Insight into the detailed mechanisms involved in CCN-mediated regulation may be useful in understanding their roles and functions in tumorigenesis and cancer metastasis. In this review, we briefly introduced the functions of CCNs, especially in cancer.

Histochemical Study of Heparin-positive Mast Cells in the Terminal Part of Porcine Ductus Choledochus and Papilla Duodeni Major

The study presented in detail the localization and density of mast cells (MCs) in the intramural part of the common bile duct (CBD) and in the major duodenal papilla (MDP) of domestic swine. MCs' density (number/mm(2) ) in different layers of both of the duct and papilla was evaluated after toluidine blue staining. Their number was higher in the lamina propria mucosae than in the tunica muscularis of the studied structures. The localization of berberine-positive, (heparin containing) MCs and the ratio between them and toluidine blue-positive MCs with γ-ma metachromasia was also established. Ratios of heparin-containing MCs in comparison with all toluidine blue-positive MCs were found as follows: ductus choledochus - 32% in the subglandular connective tissue of lamina propria mucosae in the intramural part of the duct; m. sphincter ductus choledochus - 31% in the circular and 0.06% in the longitudinal muscle layer; subserosa - 59%; papilla duodeni major - 0.03% in the subepithelial connective tissue and 34% in the subglandular connective tissue of lamina propria mucosae, respectively. The established large difference in heparin-positive MCs in both the subepithelial and subglandular connective tissues of CBD and MDP, respectively, is an evidence for the existence of mucosal and connective tissue MCs.

Eyeing the Cyr61/CTGF/NOV (CCN) group of genes in development and diseases: highlights of their structural likenesses and functional dissimilarities

“CCN” is an acronym referring to the first letter of each of the first three members of this original group of mammalian functionally and phylogenetically distinct extracellular matrix (ECM) proteins [i.e., cysteine-rich 61 (CYR61), connective tissue growth factor (CTGF), and nephroblastoma-overexpressed (NOV)]. Although “CCN” genes are unlikely to have arisen from a common ancestral gene, their encoded proteins share multimodular structures in which most cysteine residues are strictly conserved in their positions within several structural motifs. The CCN genes can be subdivided into members developmentally indispensable for embryonic viability (e.g., CCN1, 2 and 5), each assuming unique tissue-specific functions, and members not essential for embryonic development (e.g., CCN3, 4 and 6), probably due to a balance of functional redundancy and specialization during evolution. The temporo-spatial regulation of the CCN genes and the structural information contained within the sequences of their encoded proteins reflect diversity in their context and tissue-specific functions. Genetic association studies and experimental anomalies, replicated in various animal models, have shown that altered CCN gene structure or expression is associated with “injury” stimuli—whether mechanical (e.g., trauma, shear stress) or chemical (e.g., ischemia, hyperglycemia, hyperlipidemia, inflammation). Consequently, increased organ-specific susceptibility to structural damages ensues. These data underscore the critical functions of CCN proteins in the dynamics of tissue repair and regeneration and in the compensatory responses preceding organ failure. A better understanding of the regulation and mode of action of each CCN member will be useful in developing specific gain- or loss-of-function strategies for therapeutic purposes.

The expression of Wnt-1 inducible signaling pathway protein-2 in astrocytoma: Correlation between pathological grade and clinical outcome

Wnt-1 inducible signaling pathway protein-2 (WISP-2) is a member of the CCN family, which is critical for the control of cell morphology, motion, adhesion and other processes involved in tumorigenesis. The expression pattern and clinical significance of WISP-2 in astrocytomas remains unclear. In this study, reverse transcription-polymerase chain reaction was performed to systematically investigate the expression of WISP-2 in 47 astrocytoma tissues of different pathological grades and 10 normal brain tissues. The mRNA expression levels of WISP-2 in the astrocytoma tissues were observed to be significantly higher than those in the normal brain tissues. Furthermore, the upregulation of WISP-2 was found to be associated with astrocytomas of higher pathological grades. Subsequently, 154 astrocytoma and 15 normal brain tissues were analyzed using immunohistochemistry and similar results were obtained. Univariate and multivariate survival analyses were used to determine the correlations between WISP-2 expression and overall survival (OS) and progression-free survival (PFS). The results indicated that the expression of WISP-2 was found to negatively correlate with patient PFS and OS. These results demonstrated that the WISP-2 protein is involved in the pathogenesis and progression of human astrocytomas and may serve as a malignant biomarker of this disease.

Cdc42 and p190RhoGAP activation by CCN2 regulates cell spreading and polarity and induces actin disassembly in migrating keratinocytes

Cell migration requires spatiotemporal integration of signals that regulate cytoskeletal dynamics. In response to a migration-promoting agent, cells begin to polarise and extend protrusions in the direction of migration. These cytoskeletal rearrangements are orchestrated by a variety of proteins, including focal adhesion kinase (FAK) and the Rho family of GTPases. CCN2, also known as connective tissue growth factor, has emerged as a regulator of cell migration but the mechanism by which CCN2 regulates keratinocyte function is not well understood. In this article, we sought to elucidate the basic mechanism of CCN2-induced cell migration in human keratinocytes. Immunohistochemical staining was used to demonstrate that treatment with CCN2 induces a migratory phenotype through actin disassembly, spreading of lamellipodia and re-orientation of the Golgi. In vitro assays were used to show that CCN2-induced cell migration is dependent on FAK, RhoA and Cdc42, but independent of Rac1. CCN2-treated keratinocytes displayed increased Cdc42 activity and decreased RhoA activity up to 12 hours post-treatment, with upregulation of p190RhoGAP. An improved understanding of how CCN2 regulates cell migration may establish the foundation for future therapeutics in fibrotic and neoplastic diseases.

The role of the CCN family of proteins in female reproduction

The CCN family of proteins consists of six high homologous matricellular proteins which act predominantly by binding to heparin sulphate proteoglycan and a variety of integrins. Interestingly, CCN proteins are regulated by ovarian steroid hormones and are able to adapt to changes in oxygen concentration, which is a necessary condition for successful implantation. CCN1 is involved in processes of angiogenesis within reproductive systems, thereby potentially contributing to diseases such as endometriosis and disturbed angiogenesis in the placenta and fetus. In the ovary, CCN2 is the key factor for follicular development, ovulation and corpora luteal luteolysis, and its deletion leads to fertility defects. CCN1, CCN2 and CCN3 seem to be regulators for human trophoblast proliferation and migration, but with CCN2 acting as a counterweight. Alterations in the expression of these three proteins could contribute to the shallow invasion properties observed in preeclampsia. Little is known about the role of CCN4-6 in the reproductive organs. The ability of CCN1, CCN2 and CCN3 to interact with numerous receptors enables them to adapt their biological function rapidly to the continuous remodelling of the reproductive organs and in the development of the placenta. The CCN proteins mediate their specific cell physiological function through the receptor type of their binding partner followed by a defined signalling cascade. Because of their partly overlapping expression patterns, they could act in a concert synergistically or in an opposite way within the reproductive organs. Imbalances in their expression levels are correlated to different human reproductive diseases, such as endometriosis and preeclampsia.

The matricellular protein CCN5 regulates podosome function via interaction with integrin αvβ 3

CCN proteins play crucial roles in cell motility, matrix turnover, and proliferation. In particular, CCN5 plays a role in cell motility and proliferation in several cell types; however, no functional binding proteins for CCN5 have been identified. In this study we report that CCN5 binds to the cell surface receptor integrin αvβ3 in vascular smooth muscle cells. Furthermore, this interaction takes place in podosomes, organelles known to degrade matrix and mediate motility. We show that CCN5 regulates the ability of podosomes to degrade matrix, but does not affect podosome formation. The level of CCN5 present in a podosome negatively correlates with its ability to degrade matrix. Conversely, knockdown of CCN5 greatly enhances the matrix-degrading ability of podosomes. These findings suggest that the antimotility effects of CCN5 may be mediated through the direct interaction of CCN5 and integrin αvβ3 in podosomes and the concomitant suppression of matrix degradation that is required for cell migration.

The CCN family proteins: modulators of bone development and novel targets in bone-associated tumors

The CCN family of proteins is composed of six extracellular matrix-associated proteins that play crucial roles in skeletal development, wound healing, fibrosis, and cancer. Members of the CCN family share four conserved cysteine-rich modular domains that trigger signal transduction in cell adhesion, migration, proliferation, differentiation, and survival through direct binding to specific integrin receptors and heparan sulfate proteoglycans. In the present review, we discuss the roles of the CCN family proteins in regulating resident cells of the bone microenvironment. In vertebrate development, the CCN family plays a critical role in osteo/chondrogenesis and vasculo/angiogenesis. These effects are regulated through signaling via integrins, bone morphogenetic protein, vascular endothelial growth factor, Wnt, and Notch via direct binding to CCN family proteins. Due to the important roles of CCN family proteins in skeletal development, abnormal expression of CCN proteins is related to the tumorigenesis of primary bone tumors such as osteosarcoma, Ewing sarcoma, and chondrosarcoma. Additionally, emerging studies have suggested that CCN proteins may affect progression of secondary metastatic bone tumors by moderating the bone microenvironment. CCN proteins could therefore serve as potential therapeutic targets for drug development against primary and metastatic bone tumors.

CCN4 regulates vascular smooth muscle cell migration and proliferation

The migration and proliferation of vascular smooth muscle cells (VSMCs) are essential elements during the development of atherosclerosis and restenosis. An increasing number of studies have reported that extracellular matrix (ECM) proteins, including the CCN protein family, play a significant role in VSMC migration and proliferation. CCN4 is a member of the CCN protein family, which controls cell development and survival in multiple systems of the body. Here, we sought to determine whether CCN4 is involved in VSMC migration and proliferation. We examined the effect of CCN4 using rat cultured VSMCs. In cultured VSMCs, CCN4 stimulated the adhesion and migration of VSMCs in a dose-dependent manner, and this effect was blocked by an antibody for integrin α5β1. CCN4 expression was enhanced by the pro-inflammatory cytokine tumor necrosis factor α (TNF-α). Furthermore, knockdown of CCN4 by siRNA significantly inhibited the VSMC proliferation. CCN4 also could up-regulate the expression level of marker proteins of the VSMCs phenotype. Taken together, these results suggest that CCN4 is involved in the migration and proliferation of VSMCs. Inhibition of CCN4 may provide a promising strategy for the prevention of restenosis after vascular interventions.

CCN5 Expression in mammals. III. Early embryonic mouse development

CCN proteins play crucial roles in development, angiogenesis, cell motility, matrix turnover, proliferation, and other fundamental cell processes. Early embryonic lethality in CCN5 knockout and over-expressing mice led us to characterize CCN5 distribution in early development. Previous papers in this series showed that CCN5 is expressed widely in mice from E9.5 to adult; however, its distribution before E9.5 has not been studied. To fill this gap in our knowledge of CCN5 expression in mammals, RT-PCR was performed on preimplantation murine embryos: 1 cell, 2 cell, 4 cell, early morula, late morula, and blastocyst. CCN5 mRNA was not detected in 1, 2, or 4 cell embryos. It was first detected at the early morula stage and persisted to the preimplantation blastocyst stage. Immunohistochemical staining showed widespread CCN5 expression in post-implantation blastocysts (E4.5), E5.5, E6.5, and E7.5 stage embryos. Consistent with our previous study on E9.5 embryos, this expression was not limited to a particular germ layer or cell type. The widespread distribution of CCN5 in early embryos suggests a crucial role in development.

CCN5/WISP-2: A micromanager of breast cancer progression

The gain of plasticity by a subset of cancer cells is a unique but common sequence of cancer progression from epithelial phenotype to mesenchymal phenotype (EMT) that is followed by migration, invasion and metastasis to a distant organ, and drug resistance. Despite multiple studies, it is still unclear how cancer cells regulate plasticity. Recent studies from our laboratory and others' proposed that CCN5/WISP-2, which is found intracellularly (in the nucleus and cytoplasm) and extracellularly, plays a negative regulator of plasticity. It prevents the EMT process in breast cancer cells as well as pancreatic cancer cells. Multiple genetic insults, including the gain of p53 mutations that accumulate over the time, may perturb CCN5 expression in non-invasive breast cancer cells, which ultimately helps cells to gain invasive phenotypes. Moreover, emerging evidence indicates that several oncogenic lesions such as miR-10b upregulation and activation of TGF-β-signaling can accumulate during CCN5 crisis in breast cancer cells. Collectively, these studies indicate that loss of CCN5 activity may promote breast cancer progression; application of CCN5 protein may represent a novel therapeutic intervention in breast cancer and possibly pancreatic cancer.

CCN5: biology and pathophysiology

CCN5 is one of six proteins in the CCN family. This family of proteins has been shown to play important roles in many processes, including proliferation, migration, adhesion, extracellular matrix regulation, angiogenesis, tumorigenesis, fibrosis, and implantation. In this review, we focus on the biological and putative pathophysiological roles of CCN5. This intriguing protein is structurally unique among the CCN family members, and has a unique biological activity profile as well.

CCN5: biology and pathophysiology

CCN5 is one of six proteins in the CCN family. This family of proteins has been shown to play important roles in many processes, including proliferation, migration, adhesion, extracellular matrix regulation, angiogenesis, tumorigenesis, fibrosis, and implantation. In this review, we focus on the biological and putative pathophysiological roles of CCN5. This intriguing protein is structurally unique among the CCN family members, and has a unique biological activity profile as well.

The CCN proteins: important signaling mediators in stem cell differentiation and tumorigenesis

The CCN proteins contain six members, namely CCN1 to CCN6, which are small secreted cysteine-rich proteins. The CCN proteins are modular proteins, containing up to four functional domains. Many of the CCN members are induced by growth factors, cytokines, or cellular stress. The CCNs show a wide and highly variable expression pattern in adult and in embryonic tissues. The CCN proteins can integrate and modulate the signals of integrins, BMPs, VEGF, Wnts, and Notch. The involvement of integrins in mediating CCN signaling may provide diverse context-dependent responses in distinct cell types. CCN1 and CCN2 play an important role in development, angiogenesis and cell adhesion, whereas CCN3 is critical to skeletal and cardiac development. CCN4, CCN5 and CCN6 usually inhibit cell growth. Mutations of Ccn6 are associated with the progressive pseudorheumatoid dysplasia and spondyloepiphyseal dysplasia tarda. In stem cell differentiation, CCN1, CCN2, and CCN3 play a principal role in osteogenesis, chondrogenesis, and angiogenesis. Elevated expression of CCN1 is associated with more aggressive phenotypes of human cancer, while the roles of CCN2 and CCN3 in tumorigenesis are tumor type-dependent. CCN4, CCN5 and CCN6 function as tumor suppressors. Although CCN proteins may play important roles in fine-tuning other major signaling pathways, the precise function and mechanism of action of these proteins remain undefined. Understanding of the biological functions of the CCN proteins would not only provide insight into their roles in numerous cellular processes but also offer opportunities for developing therapeutics by targeting CCN functions.

CCN5, a secreted protein, localizes to the nucleus

CCN5, a member of the CCN family of growth factors, inhibits the proliferation and migration of smooth muscle cells in cell culture and animal models. Expressed in both embryonic and adult tissues, CCN5 exhibits a matricellular localization pattern characteristic of secreted proteins that are closely associated with the cell surface. In addition to this observed expression pattern, immunohistochemical evidence suggests the presence of nuclear CCN5 in some cells. To determine if CCN5 localizes to the nucleus we performed immunofluorescence, confocal imaging, and cell fractionation to corroborate the immunohistochemical observations. After confirming the presence of nuclear CCN5 using four independent experimental methods, we identified a single putative nuclear localization signal in the von Willebrand factor C domain of mouse and rat CCN5. Site directed mutagenesis of the three basic amino acids in the putative nuclear localization sequence did not prevent nuclear localization of CCN5 in four different cell types, suggesting that CCN5 nuclear transport is not mediated by the only canonical nuclear localization signal present in the primary amino acid sequence. Future work will address the mechanism of nuclear localization and the function of nuclear versus secreted CCN5.

The opposing effects of CCN2 and CCN5 on the development of cardiac hypertrophy and fibrosis

CCN family members are matricellular proteins with diverse roles in cell function. The differential expression of CCN2 and CCN5 during cardiac remodeling suggests that these two members of the CCN family play opposing roles during the development of cardiac hypertrophy and fibrosis. We aimed to evaluate the role of CCN2 and CCN5 in the development of cardiac hypertrophy and fibrosis. In isolated cardiomyocytes, overexpression of CCN2 induced hypertrophic growth, whereas the overexpression of CCN5 inhibited both phenylephrine (PE)- and CCN2-induced hypertrophic responses. Deletion of the C-terminal (CT) domain of CCN2 transformed CCN2 into a CCN5-like dominant negative molecule. Fusion of the CT domain to the Carboxy-terminus of CCN5 transformed CCN5 into a CCN2-like pro-hypertrophic molecule. CCN2 transgenic (TG) mice did not develop cardiac hypertrophy at baseline but showed significantly increased fibrosis in response to pressure overload. In contrast, hypertrophy and fibrosis were both significantly inhibited in CCN5 TG mice. CCN2 TG mice showed an accelerated deterioration of cardiac function in response to pressure overload, whereas CCN5 TG mice showed conserved cardiac function. TGF-beta-SMAD signaling was elevated in CCN2 TG mice, but was inhibited in CCN5 TG mice. CCN2 is pro-hypertrophic and -fibrotic, whereas CCN5 is anti-hypertrophic and -fibrotic. CCN5 lacking the CT domain acts as a dominant negative molecule. CCN5 may provide a novel therapeutic target for the treatment of cardiac hypertrophy and heart failure.

Domain-and species-specific monoclonal antibodies recognize the Von Willebrand Factor-C domain of CCN5

The CCN family of proteins typically consists of four distinct peptide domains: an insulin-like growth factor binding protein-type (IGFBP) domain, a Von Willebrand Factor C (VWC) domain, a thrombospondin type 1 repeat (TSP1) domain, and a carboxy-terminal (CT) domain. The six family members participate in many processes, including proliferation, motility, cell-matrix signaling, angiogenesis, and wound healing. Accumulating evidence suggests that truncated and alternatively spliced isoforms are responsible for the diverse functions of CCN proteins in both normal and pathophysiologic states. Analysis of the properties and functions of individual CCN domains further corroborates this idea. CCN5 is unique among the CCN family members because it lacks the CT-domain. To dissect the domain functions of CCN5, we are developing domain-specific mouse monoclonal antibodies. Monoclonal antibodies have the advantages of great specificity, reproducibility, and ease of long-term storage and production. In this communication, we injected mixtures of GST-fused rat CCN5 domains into mice to generate monoclonal antibodies. To identify the domains recognized by the antibodies, we constructed serial expression plasmids that express dual-tagged rat CCN5 domains. All of the monoclonal antibodies generated to date recognize the VWC domain, indicating it is the most highly immunogenic of the CCN5 domains. We characterized one particular clone, 22H10, and found that it recognizes mouse and rat CCN5, but not human recombinant CCN5. Purified 22H10 was successfully applied in Western Blot analysis, immunofluorescence of cultured cells and tissues, and immunoprecipitation, indicating that it will be a useful tool for domain analysis and studies of mouse-human tumor models.

Controlled release from multilayer silk biomaterial coatings to modulate vascular cell responses

A multilayered silk fibroin protein coating system was employed as a drug carrier and delivery system to evaluate vascular cell responses to heparin, paclitaxel, and clopidogrel. The results demonstrated that the silk coating system was an effective system for drug-eluting coatings, such as for stent applications, based on its useful micromechanical properties and biological outcomes. Cell attachment and viability studies with human aortic endothelial cells (HAECs) and human coronary artery smooth muscle cells (HCASMCs) on the drug-incorporated silk coatings demonstrated that paclitaxel and clopidogrel inhibited smooth muscle cell (SMC) proliferation and retarded endothelial cell proliferation. Heparin-loaded silk multilayers promoted HAEC proliferation while inhibiting HCASMC proliferation, desired outcomes for the prevention of restenosis. The preservation of the phenotype of endothelial cells on silk and heparin-loaded silk coatings was confirmed with the presence of endothelial markers CD-31, CD-146, vWF and VE-Cadherin using immunocytochemistry assays. A preliminary in-vivo study in a porcine aorta showed integrity of the silk coatings after implantation and the reduction of platelet adhesion on the heparin-loaded silk coatings.

CCN5 expression in mammals : I. Embryonic and fetal tissues of mouse and human

The six proteins of the CCN family have important roles in development, angiogenesis, cell motility, proliferation, and other fundamental cell processes. To date, CCN5 distribution in developing rodents and humans has not been mapped comprehensively. CCN5 strongly inhibits adult smooth muscle cell proliferation and motility. Its anti-proliferative action predicts that CCN5 would not be present in developing tissues until the proliferation phase of tissue morphogenesis is complete. However, estrogen induces CCN5 expression in epithelial and smooth muscle cells, suggesting that CCN5 might be widely expressed in embryonic tissues exposed to high levels of estrogen. 9-16 day murine embryos and fetuses and 3-7 month human fetal tissues were analyzed by immunohistochemistry. CCN5 was detected in nearly all developing tissues. CCN5 protein expression was initially present in most tissues, and at later times in development tissue-specific expression differences were observed. CCN5 expression was particularly strong in vascular tissues, cardiac muscle, bronchioles, myotendinous junctions, and intestinal smooth muscle and epithelium. CCN5 expression was initially absent in bone cartilaginous forms but was increasingly expressed during bone endochondral ossification. Widespread CCN5 mRNA expression was detected in GD14.5 mice. Although CCN2 and CCN5 protein expression patterns in some adult pathologic conditions are inversely expressed, this expression pattern was not found in developing mouse and human tissues. The widespread expression pattern of CCN5 in most embryonic and fetal tissues suggests a diverse range of functions for CCN5.

Do low-molecular-weight heparins influence the healing process in colon anastomosis?

Anastomosis leakage is one of the most serious complications of colorectal surgery. A role for extracellular matrix remodelling in the healing process of the colon wall has been recently postulated. Changes in matrix metalloproteinase (MMP) activity in the intestinal wall occurring prior to elective resection and primary anastomosis appear to be responsible for dehiscence leading to anastomosis. Thrombophylaxis using low-molecular-weight heparins is routinely administered to all patients during the perioperative period. However, adverse antiproliferative and proapoptotic effects such as limitation of bioavailability of growth factors and angiogenesis inhibition have been characterized in various cell types as a result of heparin administration. It is also likely that relationships exist between extracellular matrix homeostasis and the coagulation/fibrinolysis system. We hypothesize that subcutaneous administration of LMWHs (low-molecular-weight heparins) may influence matrix metalloproteinase activity in the colon wall and increase the risk of postoperative leakage.

Effects of heparin on the production of homocysteine-induced extracellular matrix metalloproteinase-2 in cultured rat vascular smooth muscle cells

OBJECTIVE

To study the effects of heparin on the production of homocysteine-induced extracellular matrix metalloproteinase-2 (MMP-2) in cultured rat vascular smooth muscle cells.

METHODS

The effects of different homocysteine levels (0 micromol/L to 1000 micromol/L) on MMP-2 production and the effects of different heparin concentrations (0 microg/mL to 100 microg/mL) on homocysteine-induced MMP-2 in cultured rat vascular smooth muscle cells were examined using gelatin zymography and Western blotting. The changes in MMP-2 were further compared with various treatments for 24 h, 48 h and 72 h.

RESULTS

Homocysteine (50 micromol/L to 1000 micromol/L) increased the production of MMP-2 significantly in a dose-dependent manner. Increased production of MMP-2 induced by homocysteine was reduced by the extracellular addition of heparin in a dose-dependent manner. Production of MMP-2 with various treatment regimens for 72 h was greater than for 24 h and 48 h.

CONCLUSIONS

Extracellular addition of heparin decreased homocysteine-induced MMP-2 secretion. Data suggest a mechanism by which hyperhomocysteinemia is involved in the pathogenesis of coronary artery disease and demonstrate a beneficial effect of heparin on these conditions.

Some structural determinants of the antiproliferative effect of heparin-like molecules on human airway smooth muscle

Accumulation of airway smooth muscle (ASM) and its infiltration by mast cells are key pathological features of airway remodelling in asthma. Heparin, a major component of mast cell granules, inhibits ASM proliferation by an unknown mechanism. Here, unfractionated heparins and related glycosaminoglycans having structurally heterogeneous polysaccharide side chains that varied in molecular weight, sulphation and anionic charge were used to identify features of the heparin molecule that were required for its antiproliferative activity in cultured human ASM cells. Proliferation induced by 10% fetal bovine serum (FBS) was abrogated by two unfractionated commercial heparin preparations (Sigma and Multiparin) and this effect was reproduced with each of three low-molecular weight heparin preparations (3, 5 and 6 kDa, respectively), demonstrating that antiproliferative activity resided in at least a 3 kDa heparin fraction. N-desulphated 20% re-acetylated (N-de) heparin (anticoagulant) and O-desulphated heparin (O-de) (non-anticoagulant) fractions also inhibited FBS-dependent proliferation (rank potency: Sigma heparin > O-de > N-de) suggesting that the antiproliferative action of heparin involved N-sulphation but was independent of its anticoagulant activity. Other sulphated molecules with variable anionic charge (dextran sulphate, fucoidan, chondroitin sulphates A or B, heparan sulphate) inhibited proliferation to varying degrees, as did the non-sulphated molecules hyaluronic acid and poly-L-glutamic acid. However, nonsulphated dextran had no effect. In summary, attenuation of FBS-dependent proliferation of human ASM by heparin involves but does not depend upon sulphation, although loss of N-sulphation reduces antiproliferative activity. This antiproliferative effect is independent of anionic charge and the anticoagulant actions of heparin.

Microarray analysis of early adipogenesis in C3H10T1/2 cells: cooperative inhibitory effects of growth factors and 2,3,7,8-tetrachlorodibenzo-p-dioxin

C3H10T1/2 mouse embryo fibroblasts differentiate into adipocytes when stimulated by a standard hormonal mixture (IDMB). 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), via the aryl hydrocarbon receptor (AhR), inhibits induction of the key adipogenic gene peroxisome proliferator-activated receptor gamma (PPARgamma) and subsequent adipogenesis. This TCDD-mediated inhibition requires activation of the extracellular signal-regulated kinase (ERK) pathway, which can be accomplished by serum, epidermal growth factor (EGF), or fibroblast growth factor (FGF). In the absence of serum or growth factors, IDMB induced adipogenesis without mitosis. Microarray analysis identified 200 genes that exhibited expression changes of at least twofold after 24 h of IDMB treatment. This time precedes most PPARgamma stimulation but follows the period of TCDD/ERK cooperation and periods of increased cell contraction and DNA synthesis. Functionally related gene clusters include genes associated with cell structure, triglyceride and cholesterol metabolism, oxidative regulation, and secreted proteins. In the absence of growth factors TCDD inhibited 30% of these IDMB responses without inhibiting the process of differentiation. A combination of EGF and TCDD that blocks differentiation cooperatively blocked a further 44 IDMB-responsive genes, most of which have functional links to differentiation, including PPARgamma. Cell cycle regulators that are stimulated by EGF were substantially inhibited by IDMB but these responses were unaffected by TCDD. By contrast, TCDD and EGF cooperatively reversed IDMB-induced changes in cell adhesion complexes immediately prior to increases in PPARgamma1 expression. Changes in adhesion-linked signaling may play a key role in TCDD affects on differentiation.

Activation of KATP channels by H2S in rat insulin-secreting cells and the underlying mechanisms

H2S is an important gasotransmitter, generated in mammalian cells from L-cysteine metabolism. As it stimulates K(ATP) channels in vascular smooth muscle cells, H2S may also function as an endogenous opener of K(ATP) channels in INS-1E cells, an insulin-secreting cell line. In the present study, K(ATP) channel currents in INS-1E cells were recorded using the whole-cell and single-channel recording configurations of the patch-clamp technique. K(ATP) channels in INS-1E cells have a single-channel conductance of 78 pS. These channels were activated by diazoxide and inhibited by gliclazide. ATP (3 mm) in the pipette solution inhibited K(ATP) channels in INS-1E cells. Significant amount of H2S was produced from INS-1E cells in which the expression of cystathinonie gamma-lyase (CSE) was confirmed. After INS-1E cells were transfected with CSE-targeted short interfering RNA (CSE-siRNA) or treated with DL-propargylglycine (PPG; 1-5 mm) to inhibit CSE, endogenous production of H2S was abolished. Increase in extracellular glucose concentration significantly decreased endogenous production of H2S in INS-1E cells, and increased insulin secretion. After transfection of INS-1E cells with adenovirus containing the CSE gene (Ad-CSE) to overexpress CSE, high glucose-stimulated insulin secretion was virtually abolished. Basal K(ATP) channel currents were significantly reduced after incubating INS-1E cells with a high glucose concentration (16 mm) or lowering endogenous H2S level by CSE-siRNA transfection. Under these conditions, exogenously applied H2S significantly increased whole-cell K(ATP) channel currents at concentrations equal to or lower than 100 microm. H2S (100 microm) markedly increased open probability by more than 2-fold of single K(ATP) channels (inside-out recording) in native INS-1E cells (n = 4, P < 0.05). Single-channel conductance and ATP sensitivity of K(ATP) channels were not changed by H2S. In conclusion, endogenous H2S production from INS-1E cells varies with in vivo conditions, which significantly affects insulin secretion from INS-1E cells. H2S stimulates K(ATP) channels in INS-1E cells, independent of activation of cytosolic second messengers, which may underlie H2S-inhibited insulin secretion from these cells. Interaction among H2S, glucose and the K(ATP) channel may constitute an important and novel mechanism for the fine control of insulin secretion from pancreatic beta-cells.

In Ewing's sarcoma CCN3(NOV) inhibits proliferation while promoting migration and invasion of the same cell type

Altered expression of CCN3 has been observed in a variety of musculoskeletal tumours, including Ewing's sarcoma (ES). Despite its widespread distribution, very little is known about its biological functions and molecular mechanisms of action. We transfected CCN3 gene into a CCN3-negative ES cell line and analysed the in vitro and in vivo behaviours of stably transfected clones. Forced expression of CCN3 significantly reduced cell proliferation in vitro, growth in anchorage-independent conditions, and tumorigenicity in nude mice. Despite the antiproliferative effect, CCN3-transfected ES cells displayed increased migration and invasion of Matrigel. The decreased expression of alpha2beta1 integrin receptor and the increased amount of cell surface-associated matrix metalloproteinase (MMP)-9 following the expression of CCN3 may be the basis for the increased migratory abilities of transfected cells. Cells lacking alpha2beta1 are less facilitated to have stable anchorage since the predominant collagen extracted from ES tissue is indeed type I collagen, and proMMP-9 was recently found to provide a cellular switch between stationary and migratory ES cell phase. Our findings are in line with those recently obtained in glioblastoma. However, the underlying molecular mechanisms appear to be different, further highlighting the importance of the cellular context in the regulation of function of CCN proteins.