NOV (CCN3) regulation in the growth plate and CCN family member expression in cartilage neoplasia

Elevated Expression of CCN3 in Articular Cartilage Induces Osteoarthritis in Hip Joints Irrespective of Age and Weight Bearing

Osteoarthritis (OA) occurs not only in the knee but also in peripheral joints throughout the whole body. Previously, we have shown that the expression of cellular communication network factor 3 (CCN3), a matricellular protein, increases with age in knee articular cartilage, and the misexpression of CCN3 in cartilage induces senescence-associated secretory phenotype (SASP) factors, indicating that CCN3 promotes cartilage senescence. Here, we investigated the correlation between CCN3 expression and OA degenerative changes, principally in human femoral head cartilage. Human femoral heads obtained from patients who received total hip arthroplasty were categorized into OA and femoral neck fracture (normal) groups without significant age differences. Gene expression analysis of RNA obtained from femoral head cartilage revealed that CCN3 and MMP-13 expression in the non-weight-bearing part was significantly higher in the OA group than in the normal group, whereas the weight-bearing OA parts and normal cartilage showed no significant differences in the expression of these genes. The expression of COL10A1, however, was significantly higher in weight-bearing OA parts compared with normal weight-bearing parts, and was also higher in weight-bearing parts compared with non-weight-bearing parts in the OA group. In contrast, OA primary chondrocytes from weight-bearing parts showed higher expression of CCN3, p16, ADAMTS4, and IL-1β than chondrocytes from the corresponding normal group, and higher ADAMTS4 and IL-1β in the non-weight-bearing part compared with the corresponding normal group. Acan expression was significantly lower in the non-weight-bearing group in OA primary chondrocytes than in the corresponding normal chondrocytes. The expression level of CCN3 did not show significant differences between the weight-bearing part and non-weight-bearing part in both OA and normal primary chondrocytes. Immunohistochemical analysis showed accumulated CCN3 and aggrecan neoepitope staining in both the weight-bearing part and non-weight-bearing part in the OA group compared with the normal group. The CCN3 expression level in cartilage had a positive correlation with the Mankin score. X-ray analysis of cartilage-specific CCN3 overexpression mice (Tg) revealed deformation of the femoral and humeral head in the early stage, and immunohistochemical analysis showed accumulated aggrecan neoepitope staining as well as CCN3 staining and the roughening of the joint surface in Tg femoral and humeral heads. Primary chondrocytes from the Tg femoral head showed enhanced expression of Ccn3, Adamts5, p16, Il-6, and Tnfα, and decreased expression of Col2a1 and -an. These findings indicate a correlation between OA degenerative changes and the expression of CCN3, irrespective of age and mechanical loading. Furthermore, the Mankin score indicates that the expression level of Ccn3 correlates with the progression of OA.

Fibroblast Growth Factors and Cellular Communication Network Factors: Intimate Interplay by the Founding Members in Cartilage

Fibroblast growth factors (FGFs) constitute a large family of signaling molecules that act in an autocrine/paracrine, endocrine, or intracrine manner, whereas the cellular communication network factors (CCN) family is composed of six members that manipulate extracellular signaling networks. FGFs and CCNs are structurally and functionally distinct, except for the common characteristics as matricellular proteins. Both play significant roles in the development of a variety of tissues and organs, including the skeletal system. In vertebrates, most of the skeletal parts are formed and grow through a process designated endochondral ossification, in which chondrocytes play the central role. The growth plate cartilage is the place where endochondral ossification occurs, and articular cartilage is left to support the locomotive function of joints. Several FGFs, including FGF-2, one of the founding members of this family, and all of the CCNs represented by CCN2, which is required for proper skeletal development, can be found therein. Research over a decade has revealed direct binding of CCN2 to FGFs and FGF receptors (FGFRs), which occasionally affect the biological outcome via FGF signaling. Moreover, a recent study uncovered an integrated regulation of FGF and CCN genes by FGF signaling. In this review, after a brief introduction of these two families, molecular and genetic interactions between CCN and FGF family members in cartilage, and their biological effects, are summarized. The molecular interplay represents the mutual involvement of the other in their molecular functions, leading to collaboration between CCN2 and FGFs during skeletal development.

Molecular and Genetic Interactions between CCN2 and CCN3 behind Their Yin-Yang Collaboration

Cellular communication network factor (CCN) 2 and 3 are the members of the CCN family that conduct the harmonized development of a variety of tissues and organs under interaction with multiple biomolecules in the microenvironment. Despite their striking structural similarities, these two members show contrastive molecular functions as well as temporospatial emergence in living tissues. Typically, CCN2 promotes cell growth, whereas CCN3 restrains it. Where CCN2 is produced, CCN3 disappears. Nevertheless, these two proteins collaborate together to execute their mission in a yin–yang fashion. The apparent functional counteractions of CCN2 and CCN3 can be ascribed to their direct molecular interaction and interference over the cofactors that are shared by the two. Recent studies have revealed the mutual negative regulation systems between CCN2 and CCN3. Moreover, the simultaneous and bidirectional regulatory system of CCN2 and CCN3 is also being clarified. It is of particular note that these regulations were found to be closely associated with glycolysis, a fundamental procedure of energy metabolism. Here, the molecular interplay and metabolic gene regulation that enable the yin–yang collaboration of CCN2 and CCN3 typically found in cartilage development/regeneration and fibrosis are described.

Cellular communication network factor 3 in cartilage development and maintenance

Cellular communication network factor (CCN) 3 is one of the classical members of the CCN family, which are characterized by common molecular structures and multiple functionalities. Although this protein was discovered as a gene product overexpressed in a truncated form in nephroblastoma, recent studies have revealed its physiological roles in the development and homeostasis of mammalian species, in addition to its pathological association with a number of diseases. Cartilage is a tissue that creates most of the bony parts and cartilaginous tissues that constitute the human skeleton, in which CCN3 is also differentially produced to exert its molecular missions therein. In this review article, after the summary of the molecular structure and function of CCN3, recent findings on the regulation of ccn3 expression and the roles of CCN3 in endochondral ossification, cartilage development, maintenance and disorders are introduced with an emphasis on the metabolic regulation and function of this matricellular multifunctional molecule.

CCN proteins in the musculoskeletal system: current understanding and challenges in physiology and pathology

The acronym for the CCN family was recently revised to represent “cellular communication network”. These six, small, cysteine-enriched and evolutionarily conserved proteins are secreted matricellular proteins, that convey and modulate intercellular communication by interacting with structural proteins, signalling factors and cell surface receptors. Their role in the development and physiology of musculoskeletal system, constituted by connective tissues where cells are interspersed in the cellular matrix, has been broadly studied. Previous research has highlighted a crucial balance of CCN proteins in mesenchymal stem cell commitment and a pivotal role for CCN1, CCN2 and their alter ego CCN3 in chondrogenesis and osteogenesis; CCN4 plays a minor role and the role of CCN5 and CCN6 is still unclear. CCN proteins also participate in osteoclastogenesis and myogenesis. In adult life, CCN proteins serve as mechanosensory proteins in the musculoskeletal system providing a steady response to environmental stimuli and participating in fracture healing. Substantial evidence also supports the involvement of CCN proteins in inflammatory pathologies, such as osteoarthritis and rheumatoid arthritis, as well as in cancers affecting the musculoskeletal system and bone metastasis. These matricellular proteins indeed show involvement in inflammation and cancer, thus representing intriguing therapeutic targets. This review discusses the current understanding of CCN proteins in the musculoskeletal system as well as the controversies and challenges associated with their multiple and complex roles, and it aims to link the dispersed knowledge in an effort to stimulate and guide readers to an area that the writers consider to have significant impact and relevant potentialities.

CCN3 (NOV) Drives Degradative Changes in Aging Articular Cartilage

Aging is a major risk factor of osteoarthritis, which is characterized by the degeneration of articular cartilage. CCN3, a member of the CCN family, is expressed in cartilage and has various physiological functions during chondrocyte development, differentiation, and regeneration. Here, we examine the role of CCN3 in cartilage maintenance. During aging, the expression of Ccn3 mRNA in mouse primary chondrocytes from knee cartilage increased and showed a positive correlation with p21 and p53 mRNA. Increased accumulation of CCN3 protein was confirmed. To analyze the effects of CCN3 in vitro, either primary cultured human articular chondrocytes or rat chondrosarcoma cell line (RCS) were used. Artificial senescence induced by H₂O₂ caused a dose-dependent increase in Ccn3 gene and CCN3 protein expression, along with enhanced expression of p21 and p53 mRNA and proteins, as well as SA-β gal activity. Overexpression of CCN3 also enhanced p21 promoter activity via p53. Accordingly, the addition of recombinant CCN3 protein to the culture increased the expression of p21 and p53 mRNAs. We have produced cartilage-specific CCN3-overexpressing transgenic mice, and found degradative changes in knee joints within two months. Inflammatory gene expression was found even in the rib chondrocytes of three-month-old transgenic mice. Similar results were observed in human knee articular chondrocytes from patients at both mRNA and protein levels. These results indicate that CCN3 is a new senescence marker of chondrocytes, and the overexpression of CCN3 in cartilage may in part promote chondrocyte senescence, leading to the degeneration of articular cartilage through the induction of p53 and p21.

Assessment of Iron Metabolism-Related Parameters in Obese Children

Objectives: The aim of the study was to assess the possible associations among biochemical parameters that may be correlated with the possible mechanisms of iron metabolism in healthy children with normal body mass index (BMI), along with morbid obese (MO) children with and without metabolic syndrome (MetS). Methods: To this end, children aged 6-18 years with no history of any acute or chronic diseases were selected as the population of this prospective case-control study. Thirty MO children (with BMI higher than 99th percentile and without MetS findings), 28 MO children (with BMI higher than 99th percentile and with MetS), and 30 healthy children (with BMI values between 15th and 85th percentiles) participated in the study. Then, anthropometric measurements were recorded, followed by performing the complete blood count and serum iron profile. In addition, ferritin, transferrin, hepcidin, irisin, ferroportin, brain-derived neurotrophic factor (BDNF), WISP1, and PTP1/fortilin levels were measured using ELISA. Finally, statistical analyses were performed and P<0.05 was considered as the level of statistical significance. Results: Significant differences were obtained among the groups regarding anthropometric measurements, blood pressures, triacylglycerols, and high-density lipoprotein cholesterol levels. Further, there was a tendency toward an iron deficiency in both MO groups while an increase in ferritin levels was significant in the MetS group. However, BDNF, hepcidin, and ferroportin demonstrated no significant difference among the groups. Eventually, although the above-mentioned parameters were statistically insignificant, fortilin levels indicated a gradual decrease whereas irisin levels represented an increase from control group toward morbid obesity and MetS. Conclusion: In our study, obesity severity and the tendency toward iron deficiency were in accordance with each other. Particularly, different WISP-1 levels in the groups may help predict future complications, along with its use in diagnosing obesity.

Role of the CCN protein family in cancer

The CCN protein family is composed of six matricellular proteins, which serve regulatory roles rather than structural roles in the extracellular matrix. First identified as secreted proteins which are induced by oncogenes, the acronym CCN came from the names of the first three members: CYR61, CTGF, and NOV. All six members of the CCN family consist of four cysteine-rich modular domains. CCN proteins are known to regulate cell adhesion, proliferation, differentiation, and apoptosis. In addition, CCN proteins are associated with cardiovascular and skeletal development, injury repair, inflammation, and cancer. They function either through binding to integrin receptors or by regulating the expression and activity of growth factors and cytokines. Given their diverse roles related to the pathology of certain diseases such as fibrosis, arthritis, atherosclerosis, diabetic nephropathy, retinopathy, and cancer, there are many emerging studies targeting CCN protein signaling pathways in attempts to elucidate their potentials as therapeutic targets. [BMB Reports 2018; 51(10): 486-493].

The emerging role of WISP proteins in tumorigenesis and cancer therapy

Accumulated evidence has demonstrated that WNT1 inducible signaling pathway protein (WISP) genes, which belong to members of the CCN growth factor family, play a pivotal role in tumorigenesis and progression of a broad spectrum of human cancers. Mounting studies have identified that WISP proteins (WISP1-3) exert different biological functions in various human malignancies. Emerging evidence indicates that WISP proteins are critically involved in cell proliferation, apoptosis, invasion and metastasis in cancers. Because the understanding of a direct function of WISP proteins in cancer development and progression has begun to emerge, in this review article, we describe the physiological function of WISP proteins in a variety of human cancers. Moreover, we highlight the current understanding of how the WISP protein is involved in tumorigenesis and cancer progression. Furthermore, we discuss that targeting WISP proteins could be a promising strategy for the treatment of human cancers. Hence, the regulation of WISP proteins could improve treatments for cancer patients.

Chondrosarcoma: A Rare Misfortune in Aging Human Cartilage? The Role of Stem and Progenitor Cells in Proliferation, Malignant Degeneration and Therapeutic Resistance

Unlike other malignant bone tumors including osteosarcomas and Ewing sarcomas with a peak incidence in adolescents and young adults, conventional and dedifferentiated chondrosarcomas mainly affect people in the 4th to 7th decade of life. To date, the cell type of chondrosarcoma origin is not clearly defined. However, it seems that mesenchymal stem and progenitor cells (MSPC) in the bone marrow facing a pro-proliferative as well as predominantly chondrogenic differentiation milieu, as is implicated in early stage osteoarthritis (OA) at that age, are the source of chondrosarcoma genesis. But how can MSPC become malignant? Indeed, only one person in 1,000,000 will develop a chondrosarcoma, whereas the incidence of OA is a thousandfold higher. This means a rare coincidence of factors allowing escape from senescence and apoptosis together with induction of angiogenesis and migration is needed to generate a chondrosarcoma. At early stages, chondrosarcomas are still assumed to be an intermediate type of tumor which rarely metastasizes. Unfortunately, advanced stages show a pronounced resistance both against chemo- and radiation-therapy and frequently metastasize. In this review, we elucidate signaling pathways involved in the genesis and therapeutic resistance of chondrosarcomas with a focus on MSPC compared to signaling in articular cartilage (AC).

Promoter Analyses of CCN Genes

Promoter analysis is the most basics in the analysis of gene regulation. Luciferase gene is the most commonly used reporter gene in promoter analysis. Luciferase is an enzyme that is used when firefly and Renilla reniformis (sea pansy) emit light. The first experimental step in this reporter gene assay is to connect a particular DNA segment to a luciferase gene. The second step is to transfect the reporter construct into the cells. Thereafter, stable luciferase will be produced with the help of transcriptional machinery, mRNA transporters, and translational machinery in the cells. Luciferase assay measures the quantity of light that is emitted by luciferin-luciferase reaction. Consistent with the fact that CCN2 expression has been shown to be altered by a variety of stimuli, the CCN2 promoter region also haa been shown to be bound and regulated by multiple transcription factors such as Smad, MMP3, NF-κB, AP1, TCF/LEF, and Sox9.

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

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

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.

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.

NOV inhibits proliferation while promoting apoptosis and migration in osteosarcoma cell lines through p38/MAPK and JNK/MAPK pathways

The nephroblastoma overexpressed (NOV) gene, a member of the CCN gene family that encodes secreted proteins involved in a variety of processes including tumorigenesis, is often altered in a variety of tumors, including osteosarcoma. Recent studies indicated that NOV promotes osteosarcoma metastasis, but its biological functions and molecular mechanisms on osteosarcoma proliferation have yet to be fully elucidated. The aim of the present study was to examine the role of NOV in osteosarcoma biology. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis were performed to characterize the endogenous expression of NOV in osteosarcoma cell lines. Recombinant adenovirus expressing NOV/siNOV (AdNOV/AdsiNOV) was used to infect osteosarcoma cell lines with a relatively low/high endogenous NOV expression to determine the functional relevance of NOV expression to osteosarcoma cell growth and migration in vitro, respectively. As a result, osteosarcoma cell proliferation was significantly reduced by NOV upregulation, indicated by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltrazolium bromide (MTT), colony forming assay and cell cycle analysis. Cell apoptosis was markedly induced, as indicated by Hoechst 33258 staining assay and flow cytometry (FCM) detection. Despite the antiproliferative effect, NOV-transfected osteosarcoma cells exhibited increased migration ability. The possible molecular mechanisms underlying the biological role of NOV were also investigated. The results demonstrated that NOV increased the phosphorylation of p38 and c-Jun N-terminal kinase (JNK) mitogen-actived protein kinases (MAPKs) in osteosarcoma cell lines. When the phosphorylation of p38 and JNK were inhibited by SB203580 (p38 inhibitor) or SP600125 (JNK inhibitor), respectively, the NOV-induced proliferation inhibition and cell apoptosis were reversed. In conclusion, the results revealed that NOV regulates the tumor growth of osteosarcoma cells through activation of the MAPK signaling pathway and promotes osteosarcoma cell migration in vitro.

The role of CCN family genes in haematological malignancies

Haematological malignancies, although a broad range of specific disease types, continue to show considerable overlap in classification, and patients are treated using similar chemotherapy regimes. In this review we look at the role of the CCN family of matricellular proteins and indicate their role in nine haematological malignancies including both myeloid and lymphoid neoplasms. The potential for further haematological neoplasms with CCN family associations is argued by summarising the demonstrated role of CCN family genes in the differentiation of haematopoietic stem cells (HSC) and mesenchymal stem cells. The expanding field of knowledge encompassing CCN family genes and cancers of the HSC-lineage highlights the importance of extracellular matrix-interactions in both normal physiology and tumorigenesis of the blood, bone marrow and lymph nodes.

NOV is upregulated and promotes migration and invasion in bladder cancer

NOV is pro-tumourigenic via epithelial-mesenchymal transition (EMT) in several malignancies but is not studied in bladder cancer (BCa). Whether NOV is responsible for bladder carcinogenesis and the underlying mechanism is unclear. Using immunohistochemical staining, we quantified expressions of NOV, pS6, Vimentin and E-cadherin in 66 bladder cancer and 10 normal bladder urothelium samples. EMT was profiled by EMT index (EMTi) calculated as the ratio of Vimentin to E-cadherin. In vitro and in vivo studies were carried out to profile the role of NOV in the tumourigenesis of BCa. NOV was upregulated in bladder cancer compared to normal tissue, and its expression was correlated to pS6 and EMTi. Expression of NOV was higher in recurrent and multiple tumours and was increased with progression of tumour grade. NOV expression was also higher in BCa cell lines. Silence of NOV attenuated EMT, decreased invasion and migration of BCa cells. Silence of NOV also inhibited xenograft tumour growth and decreased tumour EMT. NOV is pro-tumourigenic in bladder cancer especially in nonmuscle-invasive entities (NMIBC). NOV may promote carcinogenesis via promotion of EMT and association with increased mTOR activity.

NOV promoted the growth and migration of pancreatic cancer cells

NOV, a member of the CCN (Cyr61, CTGF and NOV) family, is involved in diverse biological processes, such as cell adhesion, proliferation and angiogenesis. However, its function in pancreatic cancer remains poorly understood. Here, we found that the expression of NOV was up-regulated in pancreatic cancer tissues. Moreover, over-expression of NOV in pancreatic cancer cells promoted cell proliferation and migration, while knock down the expression of NOV impaired the tumorigenecity of pancreatic cancer cells in vitro and in vivo. Mechanistically, NOV induced epithelial-mesenchymal transition (EMT) and regulated the expression of multiple EMT marker. Taken together, our study suggested the important role of NOV in pancreatic cancer and NOV might be an important therapeutic target.

Roles of heterotypic CCN2/CTGF-CCN3/NOV and homotypic CCN2-CCN2 interactions in expression of the differentiated phenotype of chondrocytes

To identify proteins that regulate CCN2 activity, we carried out GAL4-based yeast two-hybrid screening with a cDNA library derived from a chondrocytic cell line, HCS-2/8. CCN2/CTGF and CCN3/NOV polypeptides were picked up as CCN2-binding proteins, and CCN2–CCN2 and CCN2–CCN3 binding domains were identified. Direct binding between CCN2 and CCN3 was confirmed by coimmunoprecipitation in vitro and in vivo and surface plasmon resonance, and the calculated dissociation constants (K(d)) were 1.17 × 10(-9) m for CCN2 and CCN2, and 1.95 × 10(-9) m for CCN2 and CCN3. Ectopically overexpressed green fluorescent protein–CCN2 and Halo–CCN3 in COS7 cells colocalized, as determined by direct fluorescence analysis. We present evidence that CCN2–CCN3 interactions modulated CCN2 activity such as enhancement of ACAN and col2a1 expression. Curiously, CCN2 enhanced, whereas CCN3 inhibited, the expression of aggrecan and col2a1 mRNA in HCS-2/8 cells, and combined treatment with CCN2 and CCN3 abolished the inhibitory effect of CCN3. These effects were neutralized with an antibody against the von Willebrand factor type C domain of CCN2 (11H3). This antibody diminished the binding between CCN2 and CCN2, but enhanced that between CCN3 and CCN2. Our results suggest that CCN2 could form homotypic and heterotypic dimers with CCN2 and CCN3, respectively. Strengthening the binding between CCN2 and CCN3 with the 11H3 antibody had an enhancing effect on aggrecan expression in chondrocytes, suggesting that CCN2 had an antagonizing effect by binding to CCN3.

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

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

CCN3 (NOV) regulates proliferation, adhesion, migration and invasion in clear cell renal cell carcinoma

The CCN3/nephroblastoma overexpressed gene belongs to the CCN family of genes that encode secreted proteins involved in a variety of processes including tumorigenesis. Altered expression of CCN3 has been observed in human nephroblastoma and renal cell carcinoma (RCC), suggesting that CCN3 plays a role in kidney tumorigenesis. The aim of the present study was to examine the role of CCN3 in clear cell RCC biology. In particular, we studied the expression of CCN3 in 32 pairs of RCC tissues and corresponding normal kidney tissues using immunohistochemistry. The CCN3 gene was transfected into the 786-O cell line and the behaviors of stably transfected clones were analyzed. Results showed the expression of CCN3 was lower in RCC tissues compared to corresponding normal kidney tissues and the expression of CCN3 was inversely correlated with the Ki67 index. CCN3-expressing clones exhibited significantly inhibited cell proliferation. Furthermore, CCN3-transfected 786-O cells exhibited increased adhesion to extracellular matrix proteins, migration and invasion in Matrigel. Our data indicated that CCN3 plays an anti-proliferative role in clear cell RCC cells and promotes the adhesion, migration and invasion of clear cell RCC cells.

Genome-wide differential gene expression in immortalized DF-1 chicken embryo fibroblast cell line

BACKGROUND

When compared to primary chicken embryo fibroblast (CEF) cells, the immortal DF-1 CEF line exhibits enhanced growth rates and susceptibility to oxidative stress. Although genes responsible for cell cycle regulation and antioxidant functions have been identified, the genome-wide transcription profile of immortal DF-1 CEF cells has not been previously reported. Global gene expression in primary CEF and DF-1 cells was performed using a 4X44K chicken oligo microarray.

RESULTS

A total of 3876 differentially expressed genes were identified with a 2 fold level cutoff that included 1706 up-regulated and 2170 down-regulated genes in DF-1 cells. Network and functional analyses using Ingenuity Pathways Analysis (IPA, Ingenuity® Systems, http://www.ingenuity.com) revealed that 902 of 3876 differentially expressed genes were classified into a number of functional groups including cellular growth and proliferation, cell cycle, cellular movement, cancer, genetic disorders, and cell death. Also, the top 5 gene networks with intermolecular connections were identified. Bioinformatic analyses suggested that DF-1 cells were characterized by enhanced molecular mechanisms for cell cycle progression and proliferation, suppressing cell death pathways, altered cellular morphogenesis, and accelerated capacity for molecule transport. Key molecules for these functions include E2F1, BRCA1, SRC, CASP3, and the peroxidases.

CONCLUSIONS

The global gene expression profiles provide insight into the cellular mechanisms that regulate the unique characteristics observed in immortal DF-1 CEF cells.

CCN3 increases cell motility and MMP-13 expression in human chondrosarcoma through integrin-dependent pathway

Chondrosarcoma is a type of highly malignant tumor with a potent capacity to invade locally and cause distant metastasis. Chondrosarcoma shows a predilection for metastasis to the lungs. CCN3, also called nephroblastoma overexpressed gene (NOV), regulates proliferation and differentiation of cancer cells. However, the effect of CCN3 on migration activity in human chondrosarcoma cells is mostly unknown. Here, we found that CCN3 increased the migration and expression of matrix metalloproteinase (MMP)-13 in human chondrosarcoma cells (JJ012 cells). αvβ3 or αvβ5 monoclonal antibody (mAb), phosphatidylinositol 3-kinase (PI3K) inhibitors (Ly294002 and wortmannin) and Akt inhibitor inhibited the CCN3-induced increase of the migration and MMP-13 upregulation of chondrosarcoma cells. CCN3 stimulation increased the phosphorylation of focal adhesion kinase (FAK), PI3K, and Akt. In addition, NF-κB inhibitors also suppressed the cell migration and MMP-13 expression enhanced by CCN3. Moreover, CCN3 increased NF-κB luciferase activity and binding of p65 to the NF-κB element on the MMP-13 promoter. Taken together, our results indicate that CCN3 enhances the migration of chondrosarcoma cells by increasing MMP-13 expression through the αvβ3/αvβ5 integrin receptor, FAK, PI3K, Akt, p65, and NF-κB signal transduction pathway.

[Expressions of Cyr61 and WISP-3 in non-small cell lung cancer and its clinical significance]

背景与目的

Cyr61是非小细胞肺癌（non-small cell lung cancer, NSCLC）生长过程中的一个肿瘤抑制基因，Cyr61与WISP-3同属于CCN基因家族，具有极其明显的序列同源性。本研究通过检测Cyr61和WISP-3在NSCLC组织中的表达，探讨其临床意义。

方法

应用免疫组化SP染色法检测54例NSCLC癌组织和癌旁正常肺组织中Cyr61和WISP-3的表达，并结合临床参数进行分析。

结果

在NSCLC癌组织中Cyr61表达水平低于癌旁正常肺组织（P < 0.001），WISP-3表达水平高于癌旁正常肺组织（P < 0.001）；NSCLC癌组织中Cyr61与WISP-3蛋白表达呈负相关（r=-0.395, P=0.003）；Cyr61的表达与肿瘤的组织学分化程度、病理类型、临床分期、家族史、吸烟史和淋巴结转移有关（P < 0.05）；WISP-3阳性表达率与肿瘤的组织学分化程度、临床分期和年龄有关（P < 0.05）。

结论

Cyr61和WISP-3可能是反映NSCLC进展、生物学行为、转移发生及预后的重要生物学标记物。

Nephroblastoma overexpressed gene (NOV) enhances cell motility and COX-2 upregulation of human osteosarcoma involves αvβ5 integrin, ILK and AP-1-dependent pathways

Osteosarcoma is characterized by a high malignant and metastatic potential. Cyclooxygenase (COX)-2, the inducible isoform of prostaglandin synthase, has been implicated in tumor metastasis. Nephroblastoma overexpressed gene (NOV), also called CCN3, was regulated proliferation and differentiation of cancer cells. However, the effect of NOV on migration activity and COX-2 expression in human osteosarcoma cells is mostly unknown. Here we found that NOV increased the migration and expression of COX-2 in human osteosarcoma cells. αvβ5 monoclonal antibody (mAb), integrin-linked kinase (ILK) and Akt inhibitor reduced the NOV-enhanced the migration and COX-2 up-regulation of osteosarcoma cells. NOV stimulation increased the ILK kinase activity and phosphorylation of Akt. In addition, c-Jun siRNA also antagonized the NOV-mediated migration and COX-2 expression. Moreover, NOV enhanced the AP-1 binding activity and promoter activity. Taken together, these results suggest that the NOV acts through αvβ5 integrin to activate ILK and Akt, which in turn activates c-Jun and AP-1, resulting in the activations of COX-2 and contributing the migration of human osteosarcoma cells.

Temporal and spatial expression of CCN genes in zebrafish

The six mammalian CCN genes (Cyr61, CTGF, Nov, WISP1, WISP2, WISP3) encode a family of secreted, cysteine-rich, multimodular proteins having roles in cell proliferation, adhesion, migration, and differentiation during embryogenesis, wound healing, and angiogenesis. We used bioinformatics to identify 9 CCN genes in zebrafish (zCCNs), 6 of which have not been previously described. When compared with mammalian CCN family members, 3 were paralogs of Cyr61, 2 of CTGF, 2 of WISP1, 1 of WISP2, and 1 of WISP3. No paralog of Nov was found. In situ hybridization was performed to characterize the sites of expression of the zCCNs during early zebrafish development. zCCNs demonstrated both unique and overlapping patterns of expression, suggesting potential division of labor between orthologous genes and providing an alternate approach to gene function studies that will complement studies in mammalian models. Developmental Dynamics 239:1755–1767, 2010. © 2010 Wiley-Liss, Inc.

Influence of bone-derived matrices on generation of bone in an ectopic rat model

Most bone regeneration experimental models that test bone-derived matrices take place in conjunction with the native bone. Here, we compared the relative effectiveness of bone matrix components on bone-marrow-directed osteogenesis in an ectopic model. Cortical bone cylinders consisted of diaphysis of DA rat femurs. They were either demineralized (DBM), deproteinized (HABM), or nontreated (MBM). Fresh bone marrow was placed into cylinders and implanted at subcutaneous thoracic sites of 2-month-old DA rats. At designated times the cylinders were surgically removed from the animals. Microradiographs of DBM and histology of DBM and MBM cylinders demonstrated progressive increase in mineralized bone volume and its trabecular configuration. Bone filled the inner volume of DBM and MBM cylinders within 4 weeks, while in HABM cylinders mostly granulation tissue developed. In the DBM cylinders cartilage deposited within 10 days, while in the MBM cylinders bone was directly deposited. As early as day 3 after marrow transplantation, marrow cells interacting with DBM increased significantly the genes that express the cartilage and the bone phenotype. In conclusion, organic components of bone are needed for marrow-directed osteogenesis.

Nephroblastoma overexpressed (Nov) inactivation sensitizes osteoblasts to bone morphogenetic protein-2, but nov is dispensable for skeletal homeostasis

Overexpression of nephroblastoma overexpressed (Nov), a member of the Cyr 61, connective tissue growth factor, Nov family of proteins, inhibits osteoblastogenesis and causes osteopenia. The consequences of Nov inactivation on osteoblastogenesis and the postnatal skeleton are not known. To study the function of Nov, we inactivated Nov by homologous recombination. Nov null mice were maintained in a C57BL/6 genetic background after the removal of the neomycin selection cassette and compared with wild-type controls of identical genetic composition. Nov null mice were identified by genotyping and absent Nov mRNA in calvarial extracts and osteoblast cultures. Nov null mice did not exhibit developmental skeletal abnormalities or postnatal changes in weight, femoral length, body fat, or bone mineral density and appeared normal. Bone volume and trabecular number were decreased only in 1-month-old female mice. In older mice, after 7 months of age, osteoblast surface and bone formation were increased in females, and osteoclast and eroded surfaces were increased in male Nov null mice. Calvarial osteoblasts from Nov null mice displayed enhanced alkaline phosphatase activity, alkaline phosphatase mRNA, and transactivation of a bone morphogenetic protein (BMP)/phosphorylated mothers against decapentaplegic reporter construct in response to BMP-2. Similar results were obtained after the down-regulation of Nov by RNA interference in ST-2 stromal and MC3T3 cells. Osteoclast number was increased in marrow stromal cell cultures from Nov null mice. Surface plasmon resonance demonstrated direct interactions between Nov and BMP-2. In conclusion, Nov sensitizes osteoblasts to BMP-2, but Nov is dispensable for the maintenance of bone mass.

Prognostic relevance of CCN3 in Ewing sarcoma

Ewing sarcoma is a highly aggressive malignant bone tumor occurring preferentially in children and young adults. At present, only clinical features, such as patient age, presence of clinically evident metastases at diagnosis, and poor response to neoadjuvant chemotherapy, are widely accepted as prognostic indicators in Ewing sarcoma. In this study, we assessed the prognostic value of CCN3 (Nov), a matricellular protein that play crucial roles in bone formation. Polyclonal antibodies directed against each of the different CCN3 modules were used to identify variant CCN3 proteins in tumors and to draw potential relationships between the expression of these variants and the outcome of patients with Ewing sarcoma. Our results confirmed that expression of the full-length CCN3 in Ewing sarcoma is associated to a worse prognostic. Furthermore, we report a possible relationship between the expression of a CCN3 protein lacking an internal module (von Willebrand factor type C) and sensitivity to radiotherapy. We hypothesize that the increased level of variant CCN3 in the tumor cells reduces their tumorigenic potential and results in better outcome.

Cooperative regulation of chondrocyte differentiation by CCN2 and CCN3 shown by a comprehensive analysis of the CCN family proteins in cartilage

CCN2 is best known as a promoter of chondrocyte differentiation among the CCN family members, and its null mice display skeletal dysmorphisms. However, little is known concerning roles of the other CCN members in chondrocytes. Using both in vivo and in vitro approaches, we conducted a comparative analysis of CCN2-null and wildtype mice to study the roles of CCN2 and the other CCN proteins in cartilage development. Immunohistochemistry was used to evaluate the localization of CCN proteins and other chondrocyte-associated molecules in the two types of mice. Moreover, gene expression levels and the effects of exogenous CCN proteins on chondrocyte proliferation, differentiation, and the expression of chondrocyte-associated genes in their primary chondrocytes were evaluated. Ccn3 was dramatically upregulated in CCN2-null cartilage and chondrocytes. This upregulation was associated with diminished cell proliferation and delayed differentiation. Consistent with the in vivo findings, CCN2 deletion entirely retarded chondrocyte terminal differentiation and decreased the expression of several chondrocyte-associated genes in vitro, whereas Ccn3 expression drastically increased. In contrast, the addition of exogenous CCN2 promoted differentiation strongly and induced the expression of the associated genes, whereas decreasing the Ccn3 expression. These findings collectively indicate that CCN2 induces chondrocyte differentiation by regulating the expression of chondrocyte-associated genes but that these effects are counteracted by CCN3. The lack of CCN2 caused upregulation of CCN3 in CCN2-null mice, which resulted in the observed phenotypes, such as the resultant delay of terminal differentiation. The involvement of the PTHrP-Ihh loop in the regulation of CCN3 expression is also suggested.

TGF-beta1 and WISP-1/CCN-4 can regulate each other's activity to cooperatively control osteoblast function

Wnt-induced secreted protein-1 (WISP-1), like other members of the CCN family, is expressed in skeletal tissues. Its mechanism of action remains unknown. Expression of WISP-1 was analyzed in human bone marrow stroma cells (hBMSC) by RT-PCR. We identified two major transcripts corresponding to those of full-length WISP-1, and of the splice variant WISP-1va which lacks a putative BMP/TGF-beta binding site. To investigate the function of WISP-1 in bone, hBMSC cultures were treated with recombinant human (rh)WISP-1 and analyzed for proliferation and osteogenic differentiation. WISP-1 treatment increased both BrdU incorporation and alkaline phosphatase (AP) activity. Considering the known functional synergy found between the TGF-beta super-family and members of the CCN family, we next tested the effect of WISP-1 on TGF-beta1 activity. We found that rhWISP-1 could reduce rhTGF-beta1 induced BrdU incorporation. Similarly, rhTGF-beta1 inhibited rhWISP-1 induction of AP activity. To explore functional differences between the WISP-1 variants, WISP-1 or WISP-1va were transfected into hBMSC. Both variants could strongly induce BrdU incorporation. However, there were no effects of either variant on AP activity without an additional osteogenic stimulus such as TGF-beta1. Taken together our results suggest a functional relationship between WISP-1 and TGF-beta1. To further define this relationship we analyzed the effect of WISP-1 on TGF-beta signaling. rhWISP-1 significantly reduced TGF-beta1 induced phosphorylation of Smad-2. Our data indicates that full-length WISP-1 and its variant WISP-1va are modulators of proliferation and osteogenic differentiation, and may be novel regulators of TGF-beta1 signaling in osteoblast-like cells.

Abnormal skeletal and cardiac development, cardiomyopathy, muscle atrophy and cataracts in mice with a targeted disruption of the Nov (Ccn3) gene

BACKGROUND

Signals from the extracellular environment control many aspects of cell behaviour including proliferation, survival, differentiation, adhesion and migration. It is increasingly evident that these signals can be modulated by a group of matricellular proteins called the CCN family. CCN proteins have multiple domains through which they regulate the activities of a variety of signalling molecules including TGFbeta, BMPs and integrins, thereby influencing a wide range of processes in development and disease. Whilst the developmental roles of CCN1 and CCN2 have been elucidated, very little is known about the function of CCN3 (NOV). To investigate this, we have generated mice carrying a targeted mutation in the Nov gene (Novdel3) which reveal for the first time its diverse functions in embryos and adults.

RESULTS

By replacing Nov exon 3 with a TKneomycin cassette, we have generated Novdel3-/- mice which produce no full length NOV protein and express at a barely detectable level a mutant NOV protein that lacks the VWC domain. In Novdel3-/- embryos, and to a lesser extent in Novdel3+/- embryos, development of the appendicular and axial skeleton was affected with enlarged vertebrae, elongated long bones and digits, delayed ossification, increased bone mineralization and severe joint malformations. Primary embryo fibroblasts from Novdel3-/- mutant embryos showed enhanced chondrogenesis and osteogenesis. Cardiac development was also influenced leading to enlargement and abnormal modelling of the endocardial cushions, associated with septal defects and delayed fusion. In adults, cardiomyopathy was apparent, with hypertrophy and calcification of the septum and left ventricle dilation. Muscle atrophy was seen by 5 months of age, associated with transdifferentiation to fat. Premature tissue degeneration was also seen in the lens, with cataracts present from 6 months.

CONCLUSION

We have generated the first mice with a mutation in the Nov gene (Novdel3). Our data demonstrate that NOV is a regulator of skeletal and cardiac development, and implicates NOV in various disease processes including cardiomyopathy, muscle atrophy and cataract formation. Novdel3 mutants represent a valuable resource for studying NOV's role in the modulation and co-ordination of multiple signalling pathways that underpin organogenesis and tissue homeostasis.

The 5' untranslated regions (UTRs) of CCN1, CCN2, and CCN4 exhibit cryptic promoter activity

CCNs are structurally related matricellular proteins that are highly expressed in many embryonic and adult tissues, including the skeletal system and tumors, where canonical cap-dependent translation is suppressed under hypoxic environments. CCNs are encoded by mRNAs containing long G/C rich 5'-untranslated regions (5'-UTRs). Given that they are expressed under conditions of cellular stress, it has been suggested that the long G/C-rich regions contain internal ribosomal entry sites (IRES) that allow these mRNAS to be translated under conditions where cap-dependent translation is suppressed. Previously published work supported this possibility. However, recent studies have shown that a number of previously reported cellular IRES elements do not in fact possess IRES activity. Here we aimed to reveal whether the 5'UTRs of CCNs harbor IRES activities. The 5'UTRs of CCN1, 2, and 4 were tested in this study. Our results showed that the 5'UTRs of these genes do not contain IRES elements, but instead appear to contain cryptic promoters. Both promoterless and hairpin-containing dicistronic tests showed that transcription was initiated by cryptic promoter elements in 5'UTRs of CCN1, 2, and 4. When dicistronic mRNAs were translated in vitro or in vivo, no IRES activities were detected in the 5'UTRs of CCN1, 2, and 4. Furthermore, these cryptic promoter activities from 5'UTRs of CCN1, 2, and 4 could be detected in various cell types, including chondrocytes, osteoblasts, and endothelial cells, where the cryptic promoter permitted varying degrees of activation. In addition, the core promoter element of the CCN2 5'UTR was identified. CCNs are expressed under conditions of cellular stress, and it has been suggested that some CCN family members utilize IRES-mediated translation initiation to facilitate this expression. We found no evidence for IRES activity, but rather found that the unusually long 5'UTRs of CCNs 1, 2, and 4 harbor cryptic promoters that showed varying degrees of activity in different cell types. These results suggest that these promoters may contribute to the regulation of CCN genes in vivo.

Connective tissue growth factor (CTGF/CCN2) is a downstream mediator for TGF-beta1-induced extracellular matrix production in osteoblasts

Connective tissue growth factor (CTGF/CCN2) is a cysteine-rich, extracellular matrix (ECM) protein that acts as an anabolic growth factor to regulate osteoblast differentiation and function. Recent studies have identified CTGF as a downstream effector of transforming growth factor-beta1 (TGF-beta1) for certain functions in specific cell types. In this study, we examined the role of CTGF as a downstream mediator of TGF-beta1-induced ECM production and cell growth in osteoblasts. Using primary cultures, we demonstrated that TGF-beta1 is a potent inducer of CTGF expression in osteoblasts, and that this induction occurred at all stages of osteoblast differentiation from the proliferative through mineralization stages. TGF-beta1 treatment of osteoblasts increased the expression and synthesis of the ECM components, collagen and fibronectin. When CTGF-specific siRNA was used to prevent TGF-beta1 induction of CTGF expression, it also inhibited collagen and fibronectin production, thereby demonstrating the requirement of CTGF for their up-regulation. To examine the effects of TGF-beta1 on osteoblast cell growth, cultures were treated with TGF-beta1 during the proliferative stage. Cell number was significantly reduced and the cells exhibited a decrease in G1 cyclin expression, consistent with TGF-beta1-induced cell-cycle arrest. Cultures transfected with CTGF siRNA prior to TGF-beta1 treatment showed an even greater reduction in cell number, suggesting that TGF-beta1-induced growth arrest is independent of CTGF in osteoblasts. Collectively, these data demonstrate for the first time that CTGF is an essential downstream mediator for TGF-beta1-induced ECM production in osteoblasts, but these two growth factors function independently regarding their opposing effects on osteoblast proliferation.

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.

Role of CCN2/CTGF/Hcs24 in bone growth

Our bones mostly develop through a process called endochondral ossification. This process is initiated in the cartilage prototype of each bone and continues through embryonic and postnatal development until the end of skeletal growth. Therefore, the central regulator of endochondral ossification is the director of body construction, which is, in other words, the determinant of skeletal size and shape. We suggest that CCN2/CTGF/Hcs24 (CCN2) is a molecule that conducts all of the procedures of endochondral ossification. CCN2, a member of the CCN family of novel modulator proteins, displays multiple functions by manipulating the local information network, using its conserved modules as an interface with a variety of other biomolecules. Under a precisely designed four-dimensional genetic program, CCN2 is produced from a limited population of chondrocytes and acts on all of the mesenchymal cells inside the bone callus to promote the integrated growth of the bone. Furthermore, the utility of CCN2 as regenerative therapeutics against connective tissue disorders, such as bone and cartilage defects and osteoarthritis, has been suggested. Over the years, the pathological action of CCN2 has been suggested. Nevertheless, it can also be regarded as another aspect of the physiological and regenerative function of CCN2, which is discussed as well.

Pathogenic role of connective tissue growth factor (CTGF/CCN2) in osteolytic metastasis of breast cancer

The role of CTGF/CCN2 in osteolytic metastasis by breast cancer cells and its mechanism of action were studied. Osteolytic metastasis accompanied by CCN2 and PTHrP overproduction was efficiently inhibited by an anti-CCN2 antibody. Furthermore, we found that CCN2 was induced by PTHrP through PKA-, PKC-, and ERK-mediated pathways therein.

INTRODUCTION

Connective tissue growth factor (CTGF/CCN2) is a mediator of local angiogenesis induced by breast cancer, but its role in osteolytic metastasis has not been evaluated. PTH-related peptide (PTHrP) is another critical factor in the development of the osteolytic metastasis. Using both in vivo and in vitro approaches, we studied whether/how neutralization of CCN2 prevented bone metastasis and how PTHrP signaling is related.

MATERIALS AND METHODS

A mouse model of bone metastasis by human breast cancer cell line MDA231 was treated with a CCN2-neutralizing antibody, and osteolytic bone metastases were assessed on radiographs and immunohistochemistry. Ccn2 gene expression and transcription were examined by Northern blot and luciferase analysis. Immunoblot analysis and kinase inhibitors were used to identify the signaling pathways implicated. Anti-angiogenic/osteoclastogenic effects of ccn2 downregulation were also evaluated.

RESULTS

Treatment of mice with a CCN2-neutralizing antibody greatly decreased osteolytic bone metastasis, microvasculature, and osteoclasts involved. The antibody also suppressed the growth of subcutaneous tumor in vivo and proliferation and migration of human umbilical vein endothelial cells (HUVECs) in vitro. Downregulation of ccn2 also repressed osteoclastogenesis. CCN2 expression was specifically observed in cancer cells producing PTHrP and type I PTH/PTHrP receptor (PTH1R) invaded the bone marrow, and PTHrP strongly upregulated ccn2 in MDA231 cells in vitro. Activation of protein kinase C (PKC) and protein kinase A (PKA) was necessary and sufficient for the stimulation of ccn2 by PTHrP. Indeed, inhibition of the extracellular signal-regulated kinase (ERK1/2), PKC, or PKA by specific inhibitors counteracted the stimulation of ccn2 expression. Incubation of MDA231 cells with PTHrP induced the activation of ERK1/2. Consistent with these findings, inhibition of PKC prevented PTHrP-induced ERK1/2 activation, whereas 12-O-tetradecanoylphorbol13-acetate (TPA), a stimulator of PKC, upregulated it.

CONCLUSIONS

CCN2 was critically involved in osteolytic metastasis and was induced by PKA- and PKC-dependent activation of ERK1/2 signaling by PTHrP. Thus, CCN2 may be a new molecular target for anti-osteolytic therapy to shut off the PTHrP-CCN2 signaling pathway.

A novel mechanism for BCR-ABL action: stimulated secretion of CCN3 is involved in growth and differentiation regulation

Chronic myeloid leukemia (CML) is characterized by the presence of the constitutively active BCR-ABL protein tyrosine kinase. Using a multipotent hemopoietic cell line, FDCP-Mix, expressing BCR-ABL tyrosine kinase, we investigated the initial effects of this kinase in primitive hematopoietic stem cells. We identified down-regulation of a novel gene, CCN3, as a direct consequence of BCR-ABL kinase activity. CCN3 has been reported to function as a tumor suppressor gene in solid tumors. Northern and Western blotting plus immunocytochemical analysis confirmed CCN3 expression is decreased and is tyrosine-phosphorylated in BCR-ABL kinase active FDCP-Mix cells. Decreased cellular CCN3 correlated with increased CCN3 secretion in BCR-ABL kinase active cells. In vitro treatment of human CML cell lines with imatinib or siRNA directed against BCR-ABL significantly reduced BCR-ABL while increasing CCN3 expression. Cells from patients responding to imatinib showed a similar decrease in BCR-ABL and increase in CCN3. CML CD34+ cells treated with imatinib in vitro demonstrated increased CCN3 protein. Transfecting CCN3 into BCR-ABL+ cells inhibited proliferation and decreased clonogenic potential. CCN3 plays an important role in internal and external cell-signaling pathways. Thus, BCR-ABL can regulate protein levels by governing secretion, a novel mechanism for this tyrosine kinase.

CCNs, fibulin-1C and S100A4 expression in leiomyoma and myometrium: inverse association with TGF-beta and regulation by TGF-beta in leiomyoma and myometrial smooth muscle cells

Connective tissue growth factor (CTGF; CCN2) is considered to serve as downstream midiator of TGF-beta action in tissue fibrosis. We tested this hypothesis in paired leiomyoma and myometrium by evaluating the expression of TGF-beta1/TGF-beta3 and CCN2, the other members of the CCN family, CCN3 and CCN4, as well as fibulin-1C and S100A4, calcium-binding proteins that interact with CCNs. The regulatory function of TGF-beta1 on the expression of these genes was further evaluated using leiomyoma (L) and myometrial (M) smooth muscle cells (SMC). Real-time PCR, Western blotting and immunohistochemistry revealed that leiomyomas and myometrium express CCNs, fibulin-1C and S100A4, whose levels of expression with the exception of fibulin-1C were lower in leiomyomas and inversely correlated with the expression of TGF-beta1 and TGF-beta3 (P<0.05). The expression of these genes was menstrual cycle-independent and GnRHa therapy increased the expression of CCN2 in leiomyomas, while inhibiting CCN3, CCN4 and S100A4 in myometrium (P<0.05). TGF-beta (2.5 ng/ml) in a time- and cell-dependent manner, and through MAPK and Smad pathways, differentially regulated the expression of these genes in LSMC and MSMC. We concluded that CCNs, fibulin-1C and S100A4 are expressed in leiomyomas/myometrium with relative expression levels inversely correlating with TGF-betas and influenced by GnRHa and TGF-beta regulatory actions. The results suggest that unlike other fibrotic disorders, CCN2 (CTGF), at least at tissue level, may not serve as a downstream mediator of TGF-beta action in leiomyomas.

NOV story: the way to CCN3

The principal aim of this historical review- the first in a new series- is to present the basic concepts that led to the discovery of NOV and to show how our ideas evolved regarding the role and functions of this new class of proteins. It should prove particularly useful to the new comers and to students who are engaged in this exciting field. It is also a good opportunity to acknowledge the input of those who participated in the development of this scientific endeavour.

New target genes for NOV/CCN3 in chondrocytes: TGF-beta2 and type X collagen

We studied the involvement of NOV/CCN3, whose function is poorly understood, in chondrocyte differentiation. NOV was found to upregulate TGF-beta2 and type X collagen and to act as a downstream effector of TGF-beta1 in ATDC5 and primary chondrocytes. Thus, NOV is a positive modulator of chondrogenesis.

INTRODUCTION

NOV/CCN3 is a matricellular protein that belongs to the CCN family. A growing body of evidence indicates that NOV could play a role in cell differentiation, particularly in chondrogenesis. During chick embryo development, NOV expression is tightly regulated in cartilage, and a high expression of NOV has been associated with cartilage differentiation in Wilms' tumors. However, a precise role for NOV and potential target genes of NOV in chondrogenesis are unknown.

MATERIALS AND METHODS

ATDC5 cells and primary chondrocytes were either treated with NOV recombinant protein or transfected with a NOV-specific siRNA to determine, using quantitative RT-PCR, the effect of NOV on the expression of several molecules involved in chondrocyte differentiation. Stable ATDC5 clones expressing NOV were also established to show that NOV was a downstream effector of TGF-beta1.

RESULTS

We established that NOV/CCN3 expression increases in ATDC5 cells at early stages of chondrogenic differentiation and precedes the appearance of TGF-beta2 and of several chondrocytic markers such as SOX9 or type X collagen. When exogenously administered, NOV recombinant protein up-regulates TGF-beta2 and type X collagen mRNA levels both in ATDC5 cells and in primary mouse chondrocytes but does not influence SOX9 expression. This regulation also occurs at the endogenous level because downregulation of NOV expression is correlated with an inhibition of TGF-beta2 and type X collagen in primary chondrocytes. Furthermore, we found that NOV expression is downregulated when chondrocytes are exposed to TGF-beta1-dedifferentiating treatment in chondrocytes, further providing evidence that NOV may counteract TGF-beta1 effects on chondrocytes.

CONCLUSIONS

This study provides the first characterization of two new targets of NOV involved in chondrocyte differentiation, shows that NOV acts with TGF-beta1 in a cascade of gene regulation, and indicates that NOV is a positive modulator of chondrogenesis.

Microarray analysis of differential gene expression in temporomandibular joint condylar cartilage after experimentally induced osteoarthritis

OBJECTIVE

To identify the gene expression profile of mandibular condylar cartilage after experimentally induced osteoarthritis (OA).

DESIGN

We studied the gene expression levels in temporomandibular joint (TMJ) condylar cartilage during different stages of experimentally induced OA. The pathological characteristics of normal, early-stage and late-stage osteoarthritic TMJ cartilage were verified by histological techniques. The gene expression profiles in normal and osteoarthritic cartilage were measured by Affymetrix RAE230A microarrays. Some of the gene transcripts were confirmed by quantitative real-time reverse-transcription PCR analysis.

RESULTS

A comprehensive, differentially expressed, gene profile was obtained in TMJ cartilage during the progression of OA. In total, 138 genes and expressed sequence tags were up- or down-regulated at least 2-fold. Some of these genes have been shown to play a role in OA, including matrix-degrading proteases, protease inhibitors and genes involved in cell growth, apoptosis and bone remodeling. However, some genes that had never been reported to be related with OA, such as AQP3, SPP2, NOV, DKK3 and EGLN3, were consistently observed to be up-regulated in this study, suggesting they may be involved in OA progression.

CONCLUSION

This study provides a new gene expression profile of the progression of OA. Further study of these OA-related genes may provide new insights into understanding the molecular mechanisms underlying OA.

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.

Differential expression of CCN-family members in primary human bone marrow-derived mesenchymal stem cells during osteogenic, chondrogenic and adipogenic differentiation

Background

The human cysteine rich protein 61 (CYR61, CCN1) as well as the other members of the CCN family of genes play important roles in cellular processes such as proliferation, adhesion, migration and survival. These cellular events are of special importance within the complex cellular interactions ongoing in bone remodeling. Previously, we analyzed the role of CYR61/CCN1 as an extracellular signaling molecule in human osteoblasts. Since mesenchymal stem cells of bone marrow are important progenitors for various differentiation pathways in bone and possess increasing potential for regenerative medicine, here we aimed to analyze the expression of CCN family members in bone marrow-derived human mesenchymal stem cells and along the osteogenic, the adipogenic and the chondrogenic differentiation.

Results

Primary cultures of human mesenchymal stem cells were obtained from the femoral head of patients undergoing total hip arthroplasty. Differentiation into adipocytes and osteoblasts was done in monolayer culture, differentiation into chondrocytes was induced in high density cell pellet cultures. For either pathway, established differentiation markers and CCN-members were analyzed at the mRNA level by RT-PCR and the CYR61/CCN1 protein was analyzed by immunocytochemistry.

RT-PCR and histochemical analysis revealed the appropriate phenotype of differentiated cells (Alizarin-red S, Oil Red O, Alcian blue, alkaline phosphatase; osteocalcin, collagen types I, II, IX, X, cbfa1, PPARγ, aggrecan). Mesenchymal stem cells expressed CYR61/CCN1, CTGF/CCN2, CTGF-L/WISP2/CCN5 and WISP3/CCN6. The CYR61/CCN1 expression decreased markedly during osteogenic differentiation, adipogenic differentiation and chondrogenic differentiation. These results were confirmed by immuncytochemical analyses. WISP2/CCN5 RNA expression declined during adipogenic differentiation and WISP3/CCN6 RNA expression was markedly reduced in chondrogenic differentiation.

Conclusion

The decrease in CYR61/CCN1 expression during the differentiation pathways of mesenchymal stem cells into osteoblasts, adipocytes and chondrocytes suggests a specific role of CYR61/CCN1 for maintenance of the stem cell phenotype. The differential expression of CTGF/CCN2, WISP2/CCN5, WISP3/CCN6 and mainly CYR61/CCN1 indicates, that these members of the CCN-family might be important regulators for bone marrow-derived mesenchymal stem cells in the regulation of proliferation and initiation of specific differentiation pathways.

Integrin-dependent Functions of the Angiogenic Inducer NOV (CCN3)

The novel angiogenic inducer CCN3 (NOV, nephroblastoma overexpressed) is a matricellular protein of the CCN family, which also includes CCN1 (CYR61), CCN2 (CTGF), CCN4 (WISP-1), CCN5 (WISP-2), and CCN6 (WISP-3). CCN3 is broadly expressed in derivatives of all three germ layers during mammalian development, and its deranged expression is associated with vascular injury and a broad range of tumors. We have shown that CCN3 promotes proangiogenic activities in vascular endothelial cells through integrin receptors and induces neovascularization in vivo (Lin, C. G., Leu, S. J., Chen, N., Tebeau, C. M., Lin, S. X., Yeung, C. Y., and Lau, L. F. (2003) J. Biol. Chem. 278, 24200-24208). In this study, we show that CCN3 is highly expressed in granulation tissue of cutaneous wounds 5-7 days after injury and is capable of inducing responses in primary fibroblasts consistent with wound healing. Purified CCN3 supports primary skin fibroblast adhesion through integrins alpha(5)beta(1) and alpha(6)beta(1) and induces fibroblast chemotaxis through integrin alpha(v)beta(5). We show that CCN3 is a novel ligand of alpha(v)beta(5) in a solid phase binding assay. Although not mitogenic on its own, CCN3 also enhances basic fibroblast growth factor-induced DNA synthesis. Furthermore, CCN3 up-regulates MMP-1 and PAI-1 expression but interacts with TGF-beta1 in an antagonistic or synergistic manner to regulate the expression of specific genes. These findings, together with its angiogenic activity, support a role for CCN3 in cutaneous wound healing in skin fibroblasts and establish its matricellular mode of action through integrin receptors.

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.

Potential cellular conformations of the CCN3(NOV) protein

Aim

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

Results

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

Conclusions

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

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

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