Report on the second international workshop on the CCN family of genes

Regulation of cellular communication network factor 1 by Ras homolog family member A in bovine steroidogenic luteal cells

Development of the corpus luteum (CL) requires the growth of a new capillary network from preexisting vasculature, a process known as angiogenesis. Successful building of this capillary network occurs through a sequence of cellular events-differentiation, proliferation, migration, and adhesion-which are regulated by a suite of angiogenic proteins that includes cellular communication network factor 1 (CCN1). We previously reported that the expression of CCN1 was highest in luteal tissue obtained from the early-cycle, 4-d-old bovine CL (i.e., corpus hemorrhagicum) compared to the mid- and late-cycle CL. In the present study, we treated steroidogenic bovine luteal cells from early-cycle CL with luteinizing hormone (LH), but it had no effect on CCN1 expression. Direct stimulation of the canonical LH pathway with forskolin and dibutyryl-cyclic adenosine monophosphate (cAMP), however, inhibited CCN1 mRNA expression. In endothelial cells, stimulation of Ras homolog family member A (RhoA) induces CCN1 expression, whereas RhoA inactivation inhibits it. Yet, it is unknown if regulation of CCN1 in steroidogenic luteal cells works likewise. We hypothesized that a similar mechanism of CCN1 regulation exists in bovine luteal cells and that thrombin, a known RhoA activator, may be a physiologic trigger for this mechanism in the early-cycle CL. To test this hypothesis, ovaries were collected from lactating dairy cows on days 3 or 4 of the estrous cycle, and corpora lutea were dissected and dissociated. Steroidogenic luteal cells were suspended in defined Ham's F12 medium, supplemented with insulin/transferrin/selenium and gentamicin, and seeded into 6-well plates. After 24 h, spent medium was replaced with fresh Ham's F12, and the cells were cultured for 24 to 48 h. Cells were treated for 2 h with defined medium, 10% fetal bovine serum (FBS), thrombin (1, 5, 10 U/mL), or Rho Activator II (0.25, 1, 2 μg/mL). Cells were then lysed for RNA extraction, followed by cDNA generation, and quantitative polymerase chain reaction (qPCR). Thrombin (1, 5, 10 U/mL; n = 3) and Rho Activator II (0.25, 1, 2 μg/mL; n = 6) increased (P < 0.05) CCN1 mRNA expression. In summary, CCN1 in bovine steroidogenic luteal cells was induced by thrombin and appeared to be regulated in a Rho-dependent manner. Future work will elucidate the signaling partners downstream of Rho which leads to CCN1 gene expression.

Matricellular CCN6 (WISP3) protein: a tumor suppressor for mammary metaplastic carcinomas

Located at 6q22-23, Ccn6 (WISP3) encodes for a matrix-associated protein of the CCN family, characterized by regulatory, rather than structural, roles in development and cancer. CCN6, the least studied member of the CCN family, shares the conserved multimodular structure of CCN proteins, as well as their tissue and cell-type specific functions. In the breast, CCN6 is a critical regulator of epithelial-to-mesenchymal transitions (EMT) and tumor initiating cells. Studies using human breast cancer tissue samples demonstrated that CCN6 messenger RNA and protein are expressed in normal breast epithelia but reduced or lost in aggressive breast cancer phenotypes, especially inflammatory breast cancer and metaplastic carcinomas. Metaplastic carcinomas are mesenchymal-like triple negative breast carcinomas, enriched for markers of EMT and stemness. RNAseq analyses of the TCGA Breast Cancer cohort show reduced CCN6 expression in approximately 50% of metaplastic carcinomas compared to normal breast. Our group identified frameshift mutations of Ccn6 in a subset of human metaplastic breast carcinoma. Importantly, conditional, mammary epithelial-cell specific ccn6 (wisp3) knockout mice develop invasive high-grade mammary carcinomas that recapitulate human spindle cell metaplastic carcinomas, demonstrating a tumor suppressor function for ccn6. Our studies on CCN6 functions in metaplastic carcinoma highlight the potential of CCN6 as a novel therapeutic approach for this specific type of breast cancer.

Dual effect of WISP-1 in diverse pathological processes

Wnt-1 inducible signaling pathway-1 (WISP-1), also known as CCN-4, belongs to the connective tissue growth factor (CTGF) family. WISP-1 is primarily expressed in embryonic stem cells and is involved in adult organ development. WISP-1 participates in many cellular processes, including proliferation, differentiation, apoptosis and adhesion. In addition, WISP-1 plays an important role in diverse pathophysiological processes, such as embryonic development, inflammation, injury repairs and cancers. Recent studies showed that WISP-1 was highly correlated with tumor progression and malignant transformation, whereas it played an oncogenic role in colorectal cancer, cholangiocarcinoma, hepatocellular carcinoma and breast cancer. However, interestingly, WISP-1 exerts a tumor-suppressing role in lung and prostate cancers. WISP-1 promotes cell proliferation, adhesion, motility, invasion, metastasis and epithelial-to-mesenchymal transition via particular signaling pathways. In this review, we discussed the structure, expression profile, functions, clinical significance and potential mechanisms of WISP-1 in cancer and non-neoplastic diseases.

High expression of WISP-1 correlates with poor prognosis in pancreatic ductal adenocarcinoma

WNT1 inducible signaling pathway protein 1 (WISP-1) is a member of the CCN family of growth factors and reported to possess an important role in tumorigenesis by triggering downstream events via integrin signaling. However, the exact role of WISP-1 in cancer remains unclear. In this study, we examined the expression pattern of WISP-1 at both mRNA and protein levels and evaluated the prognostic value of WISP-1 in pancreatic ductal adenocarcinoma (PDA). Expression of WISP-1 at mRNA level was upregulated in 17/24 tumor tissues compared to the matched adjacent non-tumor tissues and the result was confirmed by western blotting at protein level. Immunohistochemical staining of 194 pairs of PDA specimens suggested that high expression of WISP-1 is strongly correlated with clinical stage (P=0.003), T classification (P=0.008) and liver metastasis (P=0.012). Consistently, Kaplan-Meier survival curves indicated that patients with high expression of WISP-1 had a shorter survival time independent of clinical stage and lymphatic metastasis status. Moreover, univariate and multivariate analysis confirmed WISP-1 expression, age, classification and liver metastasis as independent prognostic factors for overall survival of PDA patients. Taken together, these results suggest that WISP-1 may serve as a potential prognostic biomarker for PDA.

Cell-based assay system for high-throughput screening of anti-photo-aging agents in fibroblast transfectants

The matricellular protein CCN1 is significantly elevated in acutely ultraviolet-irradiated human skin and negatively regulates collagen homeostasis by suppressing collagen synthesis and increasing collagen degradation. In this study, we established a stable cell line, termed CCN1-GFs, by transfection of the pAcGFP1-1-CCN1 promoter plasmid and examined its usefulness as a cell-based assay system for screening anti-aging ingredients. The promoter of the reporter plasmid pAcGFP1-1-CCN1 promoter was transfected into NIH3T3 cells using the Lipofectamine reagent. G418-resistant cells were selected and further cloned. To confirm whether AcGFP1-1-CCN1 promoter plasmid recombined in the NIH3T3 cells, the level of AcGFP1-1-CCN1 was measured by PCR analysis. To determine if NIH3T3 cells expressed the gene encoding green fluorescence protein in a CCN1 promoter-dependent manner, the reporter enzyme activities were assayed using a fluorimeter and flow cytometer. To determine if CCN1 inhibitor, which was selected through this system, exerted a direct effect on the downstream signal, mRNA expression of collagen1 and MMP1A was checked by using real-time PCR. UVB irradiation of CCN1-GFs resulted in increased CCN1 promoter activity. Treatment with retinoic acid, a CCN1 inhibitor, inhibited UV-induced CCN1 promoter activity. Subsequent use of this assay system to screen anti-aging ingredients revealed that CCN1-GFs treated with sclareol showed decreased levels of UVB-induced CCN1 expression. Sclareol attenuated UVB-induced photo-aging by an increase in collagen synthesis and decrease in MMP-1 activity.

Elevated YAP and its downstream targets CCN1 and CCN2 in basal cell carcinoma: impact on keratinocyte proliferation and stromal cell activation

Yes-associated protein (YAP) is a transcriptional co-activator of hippo signaling pathway, which plays an important role in organ size control and tumorigenesis. Here we report that YAP and its downstream transcriptional targets CCN1 and CCN2 are markedly elevated in keratinocytes in human skin basal cell carcinoma tumor islands. In human keratinocytes, knockdown of YAP significantly reduced expression of CCN1 and CCN2, and repressed proliferation and survival. This inhibition of proliferation and survival was rescued by restoration of CCN1 expression, but not by CCN2 expression. In basal cell carcinoma stroma, CCN2-regulated genes type I collagen, fibronectin, and α-smooth muscle actin were highly expressed. Furthermore, atomic force microscopy revealed increased tissue stiffness in basal cell carcinoma stroma compared to normal dermis. These data provide evidence that up-regulation of YAP in basal cell carcinoma impacts both aberrant keratinocyte proliferation, via CCN1, and tumor stroma cell activation and stroma remodeling, via CCN2. Targeting YAP and/or CCN1 and CCN2 may provide clinical benefit in basal cell carcinoma.

CCN proteins: A centralized communication network

The CCN family of proteins includes six members presently known as CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6. These proteins were originally designated CYR61, CTGF, NOV, and WISP-1, WISP-2, WISP-3. Although these proteins share a significant amount of structural features and a partial identity with other large families of regulatory proteins, they exhibit different biological functions. A critical examination of the progress made over the past two decades, since the first CCN proteins were discovered brings me to the conclusion that most of our present knowledge regarding the functions of these proteins was predicted very early after their discovery. In an effort to point out some of the gaps that prevent us to reach a comprehensive view of the functional interactions between CCN proteins, it is necessary to reconsider carefully data that was already published and put aside, either because the scientific community was not ready to accept them, or because they were not fitting with the « consensus » when they were published. This review article points to avenues that were not attracting the attention that they deserved. However, it is quite obvious that the six members of this unique family of tetra-modular proteins must act in concert, either simultaneously or sequentially, on the same sites or at different times in the life of living organisms. A better understanding of the spatio-temporal regulation of CCN proteins expression requires considering the family as such, not as a set of single proteins related only by their name. As proposed in this review, there is enough convincing pieces of evidence, at the present time, in favor of these proteins playing a role in the coordination of multiple signaling pathways, and constituting a Centralized Communication Network. Deciphering the hierarchy of regulatory circuits involved in this complex system is an important challenge for the near future. In this article, I would like to briefly review the concept of a CCN family of proteins and critically examine the progress made over the past 10 years in the understanding of their biological functions and involvement in both normal and pathological processes.

Dysfunction of collagen synthesis and secretion in chondrocytes induced by wisp3 mutation

Wisp3 gene mutation was shown to cause spondyloepiphyseal dysplasia tarda with progressive arthropathy (SRDT-PA), but the underlying mechanism is not clear. To clarify this mechanism, we constructed the wild and mutated Wisp3 expression vectors and transfected into human chondrocytes lines C-20/A4; Wisp3 proteins subcellular localization, cell proliferation, cell apoptosis, and Wisp3-mediated gene expression were determined, and dynamic secretion of collagen in transfected chondrocytes was analyzed by (14)C-proline incorporation experiment. Mutated Wisp3 protein increased proliferation activity, decreased apoptosis of C-20/A4 cells, and aggregated abnormally in cytoplasm. Expression of collagen II was also downregulated in C-20/A4 cells transfected with mutated Wisp3. Wild type Wisp3 transfection increased intracellular collagen content and extracellular collagen secretion, but the mutated Wisp3 lost this function, and the peak phase of collagen secretion was delayed in mutated Wisp3 transfected cells. Thus abnormal protein distribution, cell proliferation, collagen synthesis, and secretion in Wisp3 mutated chondrocytes might contribute to the pathogenesis of SEDT-PA.

Study of CCN3 (NOV) and DDR1 in normal melanocytes and vitiligo skin

We have hypothesised that melanocytes disappear in vitiligo because they are weakly attached to the epidermal basal membrane (melanocytorrhagy). In the epidermis, attachment of melanocytes to collagen IV is mediated through DDR1, which is under the control of CCN3. DDR1 genetic variants have been associated with vitiligo in patients of different ethnic origin. In vitro studies have shown that inhibition of CCN3 induces the detachment of melanocytes. We have studied in parallel the expression of CCN3 and DDR1 in lesional and perilesional skin of patients with vitiligo and the impact of the silencing of CCN3 and DDR1 in normal human melanocytes on their behaviour in epidermal reconstructs. Our in vivo study provides evidence of a dysregulation of the DDR1-CCN3 interaction in vitiligo skin as melanocytes remaining in perilesional skin did not express CCN3. Expression of DDR1 was decreased in lesional versus perilesional vitiligo skin in the majority of patients, and the expression of collagen IV was found decreased in all patients. Silencing of CCN3 in melanocytes induced a significant inhibition of cell adhesion to collagen IV whereas melanocytes transduced with shDDR1 still adhered well on collagen IV and did not increase melanocyte loss in epidermal reconstructs as compared with normal melanocytes. Melanocyte detachment was observed but not in all reconstructs using CCN3 silenced melanocytes. Overall, our study confirms that a downregulation of CCN3 is implicated in melanocyte adhesion in part through DDR1. In vitiligo skin, the interaction of CCN3 with other molecules, such as TGFβ and CCN2, needs to be addressed.

CCN3: the-pain-killer inside me

There is increasing evidence that metalloproteinases are involved in neuropathic pain [Dev et al., Expert Opin Investig Drugs 19:455-468 2010] Hence, the identification of molecules that can regulate MMP9 and MMP2 is warranted. In a recent publication, Kular et al. (2012) claim that CCN3 functions to decrease inflammatory pain via the regulation of two metalloproteinases, MMP2 and MMP9, in response to experimentally-induced inflammation. Their conclusion is based on the following observations : i) the expression of CCN3 was reduced following induction of pain by subcutaneous injection of complete Freund's adjuvent in rat's paw, ii) an inhibition of MMP9 decreased CFA-associated mechanical allodynia, iii) inhibition of CCN3 expression by siRNA led to an upregulation of MMP2 in the dorsal horn of the spinal cord (DHSC) and MMP9 in the dorsal root ganglia (DRG), iv) a partial effect of CCN3 on CFA-induced expression of MMP9 and MMP2 in DRG and DHSC following intrathecal injection of CCN3. Unfortunately, the conclusion of this study is weakened by the lack of experimental evidence showing a direct relationship between the expression of CCN3 and MMPs. Furthermore, several results contained in this manuscript only confirm data that were previously established by others. Owing to the wide range of activities which have been attributed to CCN3 (Perbal, Mol Pathol 54:57-79 2001, Brigstock, J Endocrinol 178:169-175 2003, Perbal, Lancet 363(9402):62-64 2004, Perbal, Cell Commun Signal 4:6 2006, Holbourn et al. Trends Biochem Sci. 33:461-473 2008, Leask and Abraham, J Cell Sci 119:4803-4810 2006, Jun and Lau, Nat Rev Drug Discov 10:945-963 2011, Rachfal and Brigstock, Vitam Horm 70:69-103 2005), the mechanisms underlying the potential role of CCN3 in the expression of these MMPs in the context of inflammatory pain must be thoroughly studied before a meaningful conclusion can be reached. Indeed, Kular et al. description of variations in CCN3, MMP9 and MMP2 levels occurring simultaneously is not sufficient to draw a functional relationship between these three proteins. It should be noted that the expression of CCN3 was already reported to repress MMP9 (Benini et al., Oncogene 24:4349-4361 2005, Fukunaga-Kalabis et al., Oncogene 27:2552-2560 2008) and the roles of CCN3 in inflammatory processes has been extensively documented in the past few years (Bleau et al., Front Biosci 10:998-1009 2005, Lin et al., J Biol Chem 280:8229-8237 2005, Perbal, Cell Commun Signal 4:6 2006, Hughes et al., Diabetologia 50:1089-1098 2007, Lin et al., J Cell Commun Signal 4:141-153 2010, Pasmant et al., J Neuropathol Exp Neurol 69:60-69 2010, Shimoyama et al., Thromb Vasc Biol 30:675-682 2010, Lemaire et al., J Invest Dermatol 130:2517 2010, Chen and Lau, J Cell Commun Signal 4:63-69 2010, Le Dréau et al., Glia 58:1510-1521 2010, Rittié et al. J Cell Commun Signal 5:69-80 2011, Janune et al., J Cell Commun Signal 5:167-171 2011). In addition, the expression of CCN3 in the neurons of dorsal root ganglia and dorsal horn of the spinal horn in rat and human has also been documented (Su et al., C R Acad Sci III 321:883-892 1998, Mol Pathol 54:184-191 2001, Kocialkowski et al., Anat Embryol (Berl) 203:417-427 2001). Implication of CCN3 in cognitive functions (Su et al., Sheng Li Xue Bao 52:290-294 2000) and the possible involvement of CCN3 in the regulation of pain was already suggested almost a decade ago (Perbal, Expert Rev Mol Diagn 3:597-604 2003, Perbal et al., Mol Pathol 56:80-85 2003) with the demonstration of cell-specific effects of CCN3 on intracellular calcium stores and inhibition of anionic channels by CCN3 (Li et al., Mol Pathol 55:250-261 2002, Lombet et al., Cell Commun Signal 1:1 2003, Perbal, Expert Rev Mol Diagn 3:597-604 2003, Perbal et al., Mol Pathol 56:80-85 2003). Aside from these general aspects, and in the light of the potential participation of CCN3 in the whole process of pain sensing, the reader would have appreciated the discussion in this manuscript not being essentially a flat summary of the data presented, but a more thorough discussion of the possible role for CCN3 in the regulation of MMPs and its significance in the context of the wide biological functions of CCN3.

Expression of connective tissue growth factor (CTGF/CCN2) in breast cancer cells is associated with increased migration and angiogenesis

Connective tissue growth factor (CTGF/CCN2) belongs to the CCN family of matricellular proteins, comprising Cyr61, CTGF, NovH and WISP1-3. The CCN proteins contain an N-terminal signal peptide followed by four conserved domains sharing sequence similarities with the insulin-like growth factor binding proteins, von Willebrand factor type C repeat, thrombospondin type 1 repeat, and a C-terminal growth factor cysteine knot domain. To investigate the role of CCN2 in breast cancer, we transfected MCF-7 cells with full-length CCN2, and with four mutant constructs in which one of the domains had been deleted. MCF-7 cells stably expressing full-length CCN2 demonstrated reduced cell proliferation, increased migration in Boyden chamber assays and promoted angiogenesis in chorioallantoic membrane assays compared to control cells. Deletion of the C-terminal cysteine knot domain, but not of any other domain-deleted mutants, abolished activities mediated by full-length CCN2. We have dissected the role of CCN2 in breast tumorigenesis on a structural basis.

Protective effects of Chlorella-derived peptide on UVB-induced production of MMP-1 and degradation of procollagen genes in human skin fibroblasts

UV exposure is known to induce premature aging, which is mediated by matrix metalloproteinase-1 (MMP-1) activity. MMP-1 mRNA expression is up-regulated by elevated cysteine-rich 61 (CYR61) and monocyte chemoattractant protein-1 (MCP-1) via action of transcription factor AP-1. Collagen is degraded by MMP-1 activity but synthesized by transforming growth factor-β (TGF-β) signal. Chlorella has been shown to inhibit UVB-induced MMP-1 level, however its regulatory molecular mechanisms have not been studied. In this study, Chlorella derived peptide (CDP) was added to skin fibroblasts after UVB irradiation and the expression of MMP-1, CYR61, procollagen, c-fos, c-jun, and TGF-β receptor (TbRII) mRNA and MCP-1 production were investigated. CDP (10 or 5mg/ml) diminished UVB-induced MMP-1 and CYR61 mRNA expression and MCP-1 production, whereas, UVB-suppressed procollagen and TbRII mRNA was restored by CDP treatment. UVB-induced c-fos and c-jun expressions were also inhibited by the CDP treatment. Taken together, CDP inhibits UVB-induced MMP-1 expression in skin fibroblasts by suppressing expression of AP-1 and CYR61 and MCP-1 production.

O-fucosylation of thrombospondin type 1 repeats

Thrombospondin type 1 repeats (TSRs) are small cysteine-rich motifs with three conserved disulfide bonds originally described as modules in the thrombospondins. Since then, TSRs have been found as tandem repeats in a wide variety of secreted and cell-surface proteins of diverse function. TSRs in many contexts are known to bind a variety of receptors and have antiangiogenic capabilities. They can be modified with O-linked fucose on serine/threonine found in the consensus, CX(2-3)(S/T)CX(2)G. Here we review what is known about O-fucosylation of TSRs and describe in detail mass spectral methods to map sites of O-fucosylation on proteins containing TSRs. These methods include techniques to identify glycosylated peptides and the relative amounts of elongated products by electrospray ionization mass spectrometry of glycopeptides.

Ultraviolet irradiation induces CYR61/CCN1, a mediator of collagen homeostasis, through activation of transcription factor AP-1 in human skin fibroblasts

UV irradiation from the sun elevates the production of collagen-degrading matrix metalloproteinases (MMPs) and reduces the production of new collagen. This imbalance of collagen homeostasis impairs the structure and function of the dermal collagenous extracellular matrix (ECM), thereby promoting premature skin aging (photoaging). We report here that aberrant dermal collagen homeostasis in UV-irradiated human skin is mediated in part by a CCN-family member, cysteine-rich protein-61 (CYR61/CCN1). CYR61 is significantly elevated in acutely UV-irradiated human skin in vivo, and UV-irradiated human skin fibroblasts. Knockdown of CYR61 significantly attenuates UV irradiation-induced inhibition of type-I procollagen and upregulation of MMP-1. Determination of CYR61 mRNA and protein indicates that the primary mechanism of CYR61 induction by UV irradiation is transcriptional. Analysis of CYR61 proximal promoter showed that a sequence conforming to the consensus binding site for transcription factor activator protein-1 (AP-1) is required for promoter activity. UV irradiation increased the binding of AP-1-family members c-Jun and c-Fos to this AP-1 site. Furthermore, functional blockade of c-Jun or knockdown of c-Jun significantly reduced the UV irradiation-induced activation of CYR61 promoter and CYR61 gene expression. These data show that CYR61 is transcriptionally regulated by UV irradiation through transcription factor AP-1, and mediates altered collagen homeostasis that occurs in response to UV irradiation in human skin fibroblasts.

Cyr61 is up-regulated in prostate cancer and associated with the p53 gene status

Cysteine-rich 61 (Cyr61) is a member of the CCN protein family that has been implicated in diverse biological processes such as cell adhesion, proliferation, angiogenesis, and tumorigenesis. Altered expression of Cyr61 is found to be associated with human cancers. Here we show that Cyr61 was up-regulated in prostate cancer cell lines and tumor tissues. A significant correlation of Cyr61 expression was found between benign prostatic hyperplasia and prostate cancer (P = 0.002). However, there was no significant correlation between levels of PSA and Cyr61 expression (P = 0.2). Cyr61 may represent an independent prostate cancer biomarker and potentially a useful therapeutic target for prostate cancer treatment. In addition, our analysis based on published data and data present in this report indicted that levels of Cyr61 expression associated with the status of the tumor suppressor gene p53 in 32 cancer cell lines analyzed, high levels of Cyr61 expression were found in cell lines with mutant or null p53 gene, whereas lower expression levels of Cyr61 in the cell lines with wild-type p53. We further show that over-expression of dominant negative p53 or down-expression of endogenous wild-type p53 resulted in up-regulation of Cyr61 expression, suggesting a functional link between Cyr61 and p53 in cancers.

Osteogenic differentiation of mesenchymal stem cells promoted by overexpression of connective tissue growth factor

OBJECTIVE

Large segmental bone defect repair remains a clinical and scientific challenge with increasing interest focusing on combining gene transfection with tissue engineering techniques. The aim of this study is to investigate the effect of connective tissue growth factor (CTGF) on the proliferation and osteogenic differentiation of the bone marrow mesenchymal stem cells (MSCs).

METHODS

A CTGF-expressing plasmid (pCTGF) was constructed and transfected into MSCs. Then expressions of bone morphogenesis-related genes, proliferation rate, alkaline phosphatase activity, and mineralization were examined to evaluate the osteogenic potential of the CTGF gene-modified MSCs.

RESULTS

Overexpression of CTGF was confirmed in pCTGF-MSCs. pCTGF transfection significantly enhanced the proliferation rates of pCTGF-MSCs (P<0.05). CTGF induced a 7.5-fold increase in cell migration over control (P<0.05). pCTGF transfection enhanced the expression of bone matrix proteins, such as bone sialoprotein, osteocalcin, and collagen type I in MSCs. The levels of alkaline phosphatase (ALP) activities of pCTGF-MSCs at the 1st and 2nd weeks were 4.0- and 3.0-fold higher than those of MSCs cultured in OS-medium, significantly higher than those of mock-MSCs and normal control MSCs (P<0.05). Overexpression of CTGF in MSCs enhanced the capability to form mineralized nodules.

CONCLUSION

Overexpression of CTGF could improve the osteogenic differentiation ability of MSCs, and the CTGF gene-modified MSCs are potential as novel cell resources of bone tissue engineering.

Expression of CCN family of genes in human skin in vivo and alterations by solar-simulated ultraviolet irradiation

The CCN family of proteins is involved in diverse biological functions such as cell growth, adhesion, migration, angiogenesis, and regulation of extracellular matrix. We have investigated expression of CCN family genes and alternations induced by solar-simulated ultraviolet irradiation in human skin in vivo. Transcripts of all six CCN genes were expressed in human skin in vivo. CCN5 was most abundantly expressed followed by CCN2>CCN3>CCN1>CCN4>CCN6. Solar-simulated ultraviolet irradiation increased mRNA expression of CCN1 and CCN2. In contrast, mRNA levels of CCN3, CCN4, CCN5, and CCN6, were reduced. Knowledge gained from this study provides the foundation to explore the functional roles of CCN gene products in cutaneous biology and responses to solar ultraviolet irradiation.

The CCN family of proteins: structure-function relationships

The CCN proteins are key signalling and regulatory molecules involved in many vital biological functions, including cell proliferation, angiogenesis, tumourigenesis and wound healing. How these proteins influence such a range of functions remains incompletely understood but is probably related to their discrete modular nature and a complex array of intra- and inter-molecular interactions with a variety of regulatory proteins and ligands. Although certain aspects of their biology can be attributed to the four individual modules that constitute the CCN proteins, recent results suggest that some of their biological functions require cooperation between modules. Indeed, the modular structure of CCN proteins provides important insight into their structure-function relationships.

The CCN family of proteins: structure-function relationships

The CCN proteins are key signalling and regulatory molecules involved in many vital biological functions, including cell proliferation, angiogenesis, tumourigenesis and wound healing. How these proteins influence such a range of functions remains incompletely understood but is probably related to their discrete modular nature and a complex array of intra- and inter-molecular interactions with a variety of regulatory proteins and ligands. Although certain aspects of their biology can be attributed to the four individual modules that constitute the CCN proteins, recent results suggest that some of their biological functions require cooperation between modules. Indeed, the modular structure of CCN proteins provides important insight into their structure-function relationships.

Matricellular proteins produced by melanocytes and melanomas: in search for functions

Matricellular proteins are modulators of cell-matrix interactions and cellular functions. The group includes thrombospondin, osteopontin, osteonectin/SPARC, tenascin, disintegrins, galectins and CCN proteins. The production of matricellular proteins such as osteopontin, SPARC or tenascin is highly upregulated in melanoma and other tumors but little is known about their functions in tumor growth, survival, and metastasis. The distribution pattern of CCN3 differs from most other matricellular proteins, such that it is produced abundantly by normal melanocytes, but is not significantly expressed in melanoma cells. CCN3 is known to inhibit melanocyte proliferation and stimulate adhesion to collagen type IV, the main component of the basement membrane. CCN3 has a unique role in securing adhesion of melanocytes to the basement membrane distinct from other melanoma-produced matricellular proteins which act as de-adhesive molecules and antagonists of focal adhesion. Qualitative and quantitative changes in matricellular protein expression contribute to melanoma progression similar to the E-cadherin to N-cadherin class switch, allowing melanoma cells to escape from keratinocyte control.

Downregulation of CCN3 expression as a potential mechanism for melanoma progression

Coculture of human melanocytes with keratinocytes upregulates CCN3, a matricellular protein critical to maintenance of normal homeostasis of melanocytes in the skin. CCN3 affects two fundamental features of melanocyte physiology: it inhibits melanocyte proliferation and stimulates their adhesion to the basement membrane. Here we report that expression of CCN3 is downregulated in advanced melanomas. Aggressive melanoma cell lines did not respond to treatment with CCN3 inducers, such as interleukin-1beta (IL-1beta), while less aggressive melanoma cell lines responded similarly to melanocytes. Immunostaining analyses revealed that CCN3 was present in melanoma cells close to the epidermal-dermal interface, but not in melanoma cells that had invaded deep into the dermis or had metastasized to lymph nodes. Contrary to our expectations, overexpression of CCN3 in 1205Lu metastatic melanoma cells did not affect their adhesion to collagen IV. However, CCN3 decreased the transcription and activation of matrix metalloproteinases and suppressed the invasion of 1205Lu melanoma cells. These results suggest that the lack of CCN3 in advanced melanoma cells contributes to their invasive phenotype. Whereas major matricellular proteins, such as osteopontin, tenascin or secreted protein acidic and rich in cysteine (SPARC), are strongly upregulated in melanoma cells; CCN3 is the first member of this family that is downregulated.

Differential Expression and Prognostic Implications of the CCN Family Members WISP-1, WISP-2, and WISP-3 in Human Breast Cancer

BACKGROUND

The CCN family has three Wnt-inducted secreted proteins named WISP-1, WISP-2 and WISP-3. These molecules are known to play a diverse role in cells, but their role in cancer cells remains controversial.

METHODS

In this study, we analyzed the expression of the three WISP molecules at the mRNA and protein levels in a cohort of 122 human breast tumors and 32 normal breast tissues, and we correlated these findings with patients' clinical outcomes.

RESULTS

WISP-1 transcripts were found in lower levels in node-positive tumors compared with node-negative tumors (P < .05); were lower in patients with a moderate (P = .01) and poor Nottingham Prognostic Index prognosis (P < .05) compared with good prognostic groups; were of significantly lower level in grade 3 differentiated tumors (P < .05) compared with grade 1; and were of lower levels in patients who developed metastasis and died from breast cancer-related causes (P < .05 in both comparisons). Almost the reverse was found to be true for WISP-2, which had greater levels of expression in node-positive tumors (P = .0043); higher levels in both moderate and poor prognostic groups compared with the good prognostic group (both P < .05); greater level in both grade 2 and 3 when compared with grade 1 (both P < .05); and higher levels in patients who went on to develop metastases (P < .01). WISP-3 transcript levels showed no statistically significant differences between groups.

CONCLUSIONS

WISPs may play important but contrasting roles in breast cancer. WISP-1 seems to act as a tumor suppressor and WISP-2 as a factor that stimulates aggressiveness; WISP-3 has no definable beneficial or detrimental role.

Expression and physiological role of CCN4/Wnt-induced secreted protein 1 mRNA splicing variants in chondrocytes

CCN4/Wnt-induced secreted protein 1 (WISP1) is one of the CCN (CTGF/Cyr61/Nov) family proteins. CCN members have typical structures composed of four conserved cysteine-rich modules and their variants lacking certain modules, generated by alternative splicing or gene mutations, have been described in various pathological conditions. Several previous reports described a CCN4/WISP1 variant (WISP1v) lacking the second module in a few malignancies, but no information concerning the production of WISP1 variants in normal tissue is currently available. The expression of CCN4/WISP1 mRNA and its variants were analyzed in a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8, and primary rabbit growth cartilage (RGC) chondrocytes. First, we found WISP1v and a novel variant of WISP1 (WISP1vx) to be expressed in HCS-2/8, as well as full-length WISP1 mRNA. This new variant was lacking the coding regions for the second and third modules and a small part of the first module. To monitor the expression of CCN4/WISP1 mRNA along chondrocyte differentiation, RGC cells were cultured and sampled until they were mineralized. As a result, we identified a WISP1v ortholog in normal RGC cells. Interestingly, the WISP1v mRNA level increased dramatically along with terminal differentiation. Furthermore, overexpression of WISP1v provoked expression of an alkaline phosphatase gene that is a marker of terminal differentiation in HCS-2/8 cells. These findings indicate that WISP1v thus plays a critical role in chondrocyte differentiation toward endochondral ossification, whereas HCS-2/8-specific WISP1vx may be associated with the transformed phenotypes of chondrosarcomas.

Connective tissue growth factor: a role in airway remodelling in asthma?

1. Severe persistent asthma is accompanied by structural changes in the airway, referred to as remodelling. The mechanisms driving airway remodelling are poorly understood. 2. Transforming growth factor (TGF)-beta is increased in the airways of patients with asthma. Many of the effects of TGF-beta are mediated by connective tissue growth factor (CTGF). 3. Overexpression of CTGF is linked to many fibrotic diseases, but its exact role in airway remodelling is unknown. 4. Connective tissue growth factor mediates cell adhesion, migration, proliferation, survival, extracellular matrix synthesis and has a role in angiogenesis. 5. Current asthma therapies do not inhibit CTGF induction. 6. Understanding the mechanisms underlying the role of CTGF in airway remodelling may lead to new therapeutic strategies for asthma.

Elevated cysteine-rich 61 mediates aberrant collagen homeostasis in chronologically aged and photoaged human skin

Alterations of human skin connective tissue structure and function are prominent features of chronological aging and solar UV irradiation-induced premature aging (photoaging). These skin connective tissue abnormalities result, in part, from reduced synthesis and elevated degradation of type I collagen, the major structural protein in skin. Here, we report that cysteine-rich 61 (CYR61/CCN1), a novel mediator of collagen homeostasis, is predominantly expressed in human skin connective tissue and is significantly elevated in fibroblasts in chronologically aged (80+ years) and photoaged human skin in vivo. In cultured human skin fibroblasts, elevated CYR61 expression substantially reduces type I procollagen and concurrently increases matrix metalloproteinase-1 (MMP-1), which initiates fibrillar collagen degradation. Elevated CYR61 caused down-regulation of transforming growth factor-beta type II receptor mRNA and protein levels, thereby impairing the transforming growth factor-beta pathway, which reduced type I procollagen and raised MMP-1 expression. Furthermore, elevated CYR61 induced transcription factor activator protein-1 (AP-1), which functions to stimulate MMP-1 expression. Thus, elevated expression of CYR61 in human skin fibroblasts acts through multiple pathways to cause alterations of collagen homeostasis similar to those pathways observed in aged human skin in vivo. These data identify CYR61 as a pivotal regulator of collagen production and degradation in aged and photoaged human skin.

New insight into CCN3 interactions--nuclear CCN3 : fact or fantasy?

The identification of potential partners for CCN3(NOV) sheds new light on the biological activity of this signaling protein. In particular, the physical interaction of CCN3 with the IL33 cytokine combined with previous data indicating that CCN3 expression was regulated by TNFalpha and IL1 cytokines, point to CCN3 as a potent player in a variety of inflammatory responses, including neurodegenerative disease, and arthritis. Nuclear proteins that are involved in the regulation of RNA processing and chromatin remodeling were also found to interact with CCN3. These observations reinforce the concept that routing of CCN3 to the cell nucleus where it acts as a transcription regulator, might constitute a key element in the balance between the anti- and pro-proliferative activities of CCN3 proteins.

Integration of Myeloblastosis Associated Virus proviral sequences occurs in the vicinity of genes encoding signaling proteins and regulators of cell proliferation

Aims

Myeloblastosis Associated Virus type 1 (N) [MAV 1(N)] induces specifically nephroblastomas in 8–10 weeks when injected to newborn chicken. The MAV-induced nephroblastomas constitute a unique animal model of the pediatric Wilms' tumor. We have made use of three independent nephroblastomas that represent increasing tumor grades, to identify the host DNA regions in which MAV proviral sequences were integrated. METHODS Cellular sequences localized next to MAV-integration sites in the tumor DNAs were used to screen a Bacterial Artificial Chromosomes (BACs) library and isolate BACs containing about 150 kilobases of normal DNA corresponding to MAV integration regions (MIRs). These BACs were mapped on the chicken chromosomes by Fluorescent In Situ Hybridization (FISH) and used for molecular studies.

Results

The different MAV integration sites that were conserved after tumor cell selection identify genes involved in the control of cell signaling and proliferation. Syntenic fragments in human DNA contain genes whose products have been involved in normal and pathological kidney development, and several oncogenes responsible for tumorigenesis in human.

Conclusion

The identification of putative target genes for MAV provides important clues for the understanding of the MAV pathogenic potential. These studies identified ADAMTS1 as a gene upregulated in MAV-induced nephroblastoma and established that ccn3/nov is not a preferential site of integration for MAV as previously thought. The present results support our hypothesis that the highly efficient and specific MAV-induced tumorigenesis results from the alteration of multiple target genes in differentiating blastemal cells, some of which are required for the progression to highly aggressive stages. This study reinforces our previous conclusions that the MAV-induced nephroblastoma constitutes an excellent model in which to characterize new potential oncogenes and tumor suppressors involved in the establishment and maintenance of tumors.

Structural and functional properties of CCN proteins

The CCN family currently comprises six members (CCN1-6) that regulate diverse cell functions, including mitogenesis, adhesion, apoptosis, extracellular matrix (ECM) production, growth arrest, and migration. These properties can result in a multiplicity of effects during development, differentiation, wound healing, and disease states, such as tumorigenesis and fibrosis. CCN proteins have emerged as major regulators of chondrogenesis, angiogenesis, and fibrogenesis. CCN proteins are mosaic in nature and consist of up to four structurally conserved modules, at least two of which are involved in binding to cell surfaces via molecules that include integrins, heparan sulfate proteoglycans, and low-density lipoprotein receptor-related protein. CCN proteins use integrins as signal transducing receptors to regulate context-dependent responses in individual cell types. The involvement of integrins in mediating CCN signaling allows for considerable plasticity in response because some effects are specific for certain integrin subtypes and integrin signaling is coordinated with other signaling pathways in the cell. In addition to their own biological properties, CCN proteins regulate the functions of other bioactive molecules (e.g., growth factors) via direct binding interactions. CCN molecules demonstrate complex multifaceted modes of action and regulation and have emerged as important matricellular regulators of cell function.

Angiogenesis and lymphangiogenesis: highlights of the past year

PURPOSE OF REVIEW

The purpose of this review is not to provide an extensive overview of well-established mechanisms of angiogenesis and lymphangiogenesis but rather to highlight several recent key studies that constituted a significant conceptual or medical advancement to the field during the past year or so. The authors apologize for their inability, because of space restrictions, to reference all other relevant work of the past or previous years.

RECENT FINDINGS

In 1993, fewer than 400 studies on angiogenesis were published. During the past year alone, more than 4000 angiogenesis studies were reported, making angiogenesis one of the most rapidly growing fields. Moreover, the first studies on lymphangiogenesis were published only a couple of years ago. A milestone in the field in the past year has been the first successful report that the angiogenesis inhibitor bevacizumab (Avastin), an antibody against vascular endothelial growth factor, prolonged the survival of colorectal and renal cancer patients in phase 3 clinical trials. This remarkable achievement provides great promise and hope for the future development of therapeutic strategies to inhibit or stimulate angiogenesis.

SUMMARY

The intensive search for antiangiogenic and proangiogenic mechanisms during the past decade is starting to translate into clinical promise. Further discovery of novel pathways and concepts in angiogenesis may lead to the optimization and refinement of current strategies to improve the clinical benefit and therapeutic safety for a vast number of patients with angiogenesis-related disease.

Increased expression of CYR61, an extracellular matrix signaling protein, in human benign prostatic hyperplasia and its regulation by lysophosphatidic acid

Lysophosphatidic acid (LPA) is an endogenous lipid growth factor that is thought to play important roles in cell proliferation and antiapoptosis and therefore may have roles in the development and progression of benign prostatic hyperplasia (BPH). CYR61 (CCN1), on the other hand, is a growth factor-inducible immediate early gene that functions in cell proliferation, differentiation, and extracellular matrix synthesis. Here we show the close relationship between LPA-induced expression of CYR61 and prostate enlargement. CYR61 mRNA and protein were dramatically up-regulated by 18:1 LPA (oleoyl-LPA) within 1 and 2 h, respectively, in both stromal and epithelial prostatic cells. G protein-coupled receptors, i.e. Edg-2, Edg-4, and Edg-7, for LPA were also expressed in both stromal and epithelial prostatic cells. Furthermore, on DNA microarray analysis for normal and BPH patients, CYR61 was found to be related to the development and progression of BPH, regardless of symptoms. Although CYR61 mRNA was synthesized in hyperplastic epithelial cells, in many cases of BPH, CYR61 protein was detected in both the epithelial and stromal regions of BPH patient tissues. The functional contribution of CYR61 to prostatic cell growth was demonstrated by recombinant CYR61 protein and anti-CYR61 neutralizing antibodies, which inhibited CYR61-dependent cell spreading and significantly diminished cell proliferation, respectively. In conclusion, these data support the hypothesis that LPAs induce the expression of CYR61 by activating G proteincoupled receptors and that CYR61 acts as a secreted autocrine and/or paracrine mediator in stromal and epithelial hyperplasia, demonstrating the potential importance of this signaling mechanism in the disease.

CCN proteins: multifunctional signalling regulators

CONTEXT

Although little is known as yet about the processes that coordinate cell-signalling pathways, matrix proteins are probably major players in this type of global control. The CCN (cyr61, ctgf, nov) proteins are an important family of matricellular regulatory factors involved in internal and external cell signalling. This family participates in angiogenesis, chondrogenesis, and osteogenesis, and they are probably involved in the control of cell proliferation and differentiation.

STARTING POINT

Runping Gao and David Brigstock (Hepatol Res 2003; 27: 214-20) recently showed that CCN2 (CTGF, connective tissue growth factor) is a cell-adhesion factor for hepatic stellate cells. On exposure to transforming growth factor beta, hepatic stellate cells produce distinct CCN2 isoforms. Gao and Brigstock assign to CCN2 module 3 the capacity to mediate binding to low-density-lipoprotein receptor-related protein (LRP), which was previously reported to interact with CCN2 and to be involved in various types of signalling. They also establish that CCN2 binding to LRP is heparin dependent and that module 4 of CCN2 promotes LRP-independent adhesion of hepatic stellate cells. The differential binding of CCN2 isoforms to LRP highlights the importance of functional interactions between individual modules, and reinforces the concept that different module combinations might confer agonistic or antagonistic activities. WHERE NEXT? It is essential to understand how the distinct configuration of the various CCN isoform affects their biological activities and bioavailability, and to explore the mechanisms and the regulatory processes involved in the production of truncated CCN isoforms. A better understanding of the structural basis for their multifunctionality is a prerequisite to wider use of CCN proteins in molecular medicine.

Connective tissue growth factor (CCN2) induces adhesion of rat activated hepatic stellate cells by binding of its C-terminal domain to integrin alpha(v)beta(3) and heparan sulfate proteoglycan

Connective tissue growth factor (CCN2, also known as CTGF) is a matricellular protein that appears to play an important role in hepatic stellate cell (HSC)-mediated fibrogenesis. After signal peptide cleavage, the full-length CCN2 molecule comprises four structural modules (CCN2(1-4)) and is susceptible to proteolysis by HSC yielding isoforms comprising essentially modules 3 and 4 (CCN2(3-4)) or module 4 alone (CCN2(4)). In this study we show that rat activated HSC are capable of adhesion to all three CCN2 isoforms via the binding of module 4 to integrin alpha(v)beta(3), a process that is dependent on interactions between module 4 and cell surface heparan sulfate proteoglycans (HSPGs). These findings are based on several lines of evidence. First, integrin alpha(v)beta(3) was detected in HSC lysates by immunoprecipitation and Western blot, and CCN2(4)-mediated HSC adhesion was blocked by anti-integrin alpha(v)beta(3) antibody. Second, as assessed by immunoprecipitation and solid phase binding assay, CCN2(4) bound directly to integrin alpha(v)beta(3) in cell-free systems. Third, destruction or inhibition of synthesis of cell surface HSPGs with, respectively, heparinase or sodium chlorate abrogated HSC adhesion to CCN2(4). Fourth, prior occupancy of heparin-binding sites on CCN2(4) with soluble heparin completely blocked HSC adhesion. These findings indicate that integrin alpha(v)beta(3) functions as a co-receptor with HSPGs for CCN2(4)-mediated HSC adhesion. Furthermore, by peptide mapping and site-directed mutagenesis we demonstrated that the sequence IRTPKISKPIKFELSG within CCN2(4) is a unique binding domain for integrin alpha(v)beta(3) that is sufficient to mediate integrin alpha(v)beta(3)- and HSPG-dependent HSC adhesion. These findings offer the possibility of developing novel antifibrotic therapies that target the integrin-binding domain.

Communication is the key

All forms of communication between human beings have long been recognized as a requirement for reciprocal understanding, transfer of knowledge, and productive development of societies. This also applies to living cells who are organized in «microsocieties» that constantly adjust to their environment through a complex network of signaling pathways. The chemical communication which occurs at various levels results in an integrated exchange of information that is essential for coordinated responses.

We wish to present a few features of Cell Communication and Signaling: an open access, peer-reviewed journal devoted to the publication of manuscripts covering all aspects of cell communication, with a particular focus on molecular processes that govern intercellular signaling and events that sustain cellular communication, both in normal and pathological conditions.

The launching of Cell Communication and Signaling provides us the opportunity to present a brief overview of basic processes underlying cell communication and the signaling processes that take place within and between cells to permit an efficient communication.

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.

Proposal for a unified CCN nomenclature

A proposal is put forth to unify the nomenclature of the CCN family of secreted, cysteine rich regulatory proteins. In the order of their description in the literature, CCN1 (CYR61), CCN2 (CTGF), CCN3 (NOV), CCN4 (WISP-1), CCN5 (WISP-2), and CCN6 (WISP-3) constitute a family of matricellular proteins that regulate cell adhesion, migration, proliferation, survival, and differentiation, at least in part through integrin mediated mechanisms. This proposal is endorsed by the International CCN Society and will serve to eliminate confusion from the multiple names that have been given to these molecules.