Upregulation of MMP-13 via Runx2 in the stromal cell of Giant Cell Tumor of bone

Human Chorionic Gonadotropin Regulates the Smad Signaling Pathway by Antagonizing TGF-β in Giant Cell Tumor of Bone

BACKGROUND

Giant cell tumor of bone (GCTB) is a locally aggressive bone tumour aggravated by stromal cell proliferation and metastasis.

OBJECTIVE

We investigated the mechanism of action of human chorionic gonadotropin (HCG) in mediating GCTB proliferation and invasion.

METHODS

The expression of HCG was quantified using quantitative real-time PCR. After the primary stromal cells were isolated and identified, the function of HCG in GCTB was estimated using the cell counting kit-8, flow cytometry, scratch experiment, transwell assay, Western blot, and immunofluorescence. Moreover, the mechanism of HCG was assessed through western blotting.

RESULTS

HCG expression was decreased in clinical tissue samples from patients with GCTB. We validated that HCG repressed stromal cell proliferation, migration, invasion, autophagy, and epithelial- mesenchymal transition (EMT) and promoted cell apoptosis in GCTB. We also verified that HCG repressed the autophagy and EMT of stromal cells through the Smad signaling axis in GCTB. HCG inhibited the transduction of the Smad signaling pathway by restraining the binding of the TGF-β II receptor to ligand Activin A.

CONCLUSION

HCG restrained the Smad signaling pathway by antagonizing TGF-β signaling in GCTB. HCG may serve as a useful patent to treat GCTB.

Effects of Epigallocatechin-3-Gallate on Matrix Metalloproteinases in Terms of Its Anticancer Activity

Epidemiological studies have shown that the consumption of green tea has beneficial effects against cancer. Basic studies have provided evidence that epigallocatechin gallate (EGCG) is a major contributor to these effects. Matrix metalloproteinases (MMPs) are zinc-dependent metalloproteinases with the ability to degrade the extracellular matrix proteins and are involved in various diseases including cancer in which MMPs have a critical role in invasion and metastasis. In this review, we discuss the effects of EGCG on several types of MMPs in the context of its anticancer activity. In the promoter region, MMPs have binding sites for at least one transcription factor of AP-1, Sp1, and NF-κB, and EGCG can downregulate these transcription factors through signaling pathways mediated by reactive oxygen species. EGCG can also decrease nuclear ERK, p38, heat shock protein-27 (Hsp27), and β-catenin levels, leading to suppression of MMPs' expression. Other mechanisms by which EGCG inhibits MMPs include direct binding to MMPs to prevent their activation and downregulation of NF-κB to suppress the production of inflammatory cytokines such as TNFα and IL-1β. Findings from studies on EGCG presented here may be useful in the development of more effective anti-MMP agents, which would give beneficial effects on cancer and other diseases.

Multiple roles of Runt-related transcription factor-2 in tooth eruption: bone formation and resorption

OBJECTIVE

The aim was to provide a comprehensive review of the current knowledge of the multiple roles of Runt-related transcription factor-2 (RUNX2) in regulating tooth eruption, focusing on the molecular mechanisms regarding tooth eruption mediated by RUNX2.

DESIGN

Relevant literatures in PubMed, Medline, and Scopus database were searched, and a narrative review was performed. The multiple roles of RUNX2 in regulating tooth eruption was reviewed and discussed.

RESULTS

Aberrant RUNX2 expression leads to disturbed or failed tooth eruption. Tooth eruption involves both the process of bone formation and bone resorption. RUNX2 promotes osteogenesis around the radicular portion of the dental follicle that provides the biological force for tooth eruption through inducing the expression of osteogenesis-related genes in dental follicle cells/osteoblasts. On the other hand, through indirect and direct pathways, RUNX2 regulates osteoclastogenesis and the formation of the eruption pathway.

CONCLUSION

RUNX2 exerts a pivotal and complex influence in regulating tooth eruption. This review provides a better understanding of the function of RUNX2 in tooth eruption, which is beneficial to illuminate the precise molecular mechanism of osteogenesis and bone resorption, aiding the development of effective therapy for the failure of tooth eruption.

Serglycin induces osteoclastogenesis and promotes tumor growth in giant cell tumor of bone

Giant cell tumor of bone (GCTB) is an aggressive osteolytic bone tumor characterized by the within-tumor presence of osteoclast-like multinucleated giant cells (MGCs), which are induced by the neoplastic stromal cells and lead to extensive bone destruction. However, the underlying mechanism of the pathological process of osteoclastogenesis in GCTB is poorly understood. Here we show that the proteoglycan Serglycin (SRGN) secreted by neoplastic stromal cells plays a crucial role in the formation of MGCs and tumorigenesis in GCTB. Upregulated SRGN expression and secretion are observed in GCTB tumor cells and patients. Stromal-derived SRGN promotes osteoclast differentiation from monocytes. SRGN knockdown in stromal cells inhibits tumor growth and bone destruction in a patient-derived orthotopic xenograft model of mice. Mechanistically SRGN interacts with CD44 on the cell surface of monocytes and thus activates focal adhesion kinase (FAK), leading to osteoclast differentiation. Importantly, blocking CD44 with a neutralizing antibody reduces the number of MGCs and suppresses tumorigenesis in vivo. Overall, our data reveal a mechanism of MGC induction in GCTB and support CD44-targeting approaches for GCTB treatment.

Benign albeit glycolytic: MCT4 expression and lactate release in giant cell tumour of bone

Giant cell tumour of bone (GCTB) is a histologically benign, locally aggressive skeletal lesion with an unpredictable propensity to relapse after surgery and a rare metastatic potential. The microscopic picture of GCTB shows different cell types, including multinucleated giant cells, mononuclear cells of the macrophage-monocyte lineage, and spindle cells. The histogenesis of GCTB is still debated, and morphologic, radiographic or molecular features are not predictive of the clinical course. Characterization of the unexplored cell metabolism of GCTB offers significant clues for the understanding of this elusive pathologic entity. In this study we aimed to characterize GCTB energetic metabolism, with a particular focus on lactate release and the expression of monocarboxylate transporters, to lie down a novel path for understanding the pathophysiology of this tumour. We measured the expression of glycolytic markers (GAPDH, PKM2, MCT4, GLUT1, HK1, LDHA, lactate release) in 25 tissue samples of GCTB by immunostaining and by mRNA and ELISA analyses. We also evaluated MCT1 and MCT4 expression and oxidative markers (JC1 staining and Bec index) in tumour-derived spindle cell cultures and CD14+ monocytic cells. Finally, we quantified the intratumoural and circulating levels of lactate in a series of 17 subjects with GCTB. In sharp contrast to the benign histological features of GCTB, we found a high expression of glycolytic markers, with particular reference to MCT4. Unexpectedly, this was mainly confined to the giant cell, not proliferating cell component. Accordingly, GCTB patients showed higher levels of blood lactate as compared to healthy subjects. In conclusion, taken together, our data indicate that GCTB is characterized by a highly glycolytic metabolism of its giant cell component, opening new perspectives on the pathogenesis, the natural history, and the treatment of this lesion.

Functions of Exogenous RUNX2 in Giant Cell Tumor of Bone In Vitro

OBJECTIVES

This research aimed to investigate the relative level of Runt-related transcription factor 2 (RUNX2) in giant cell tumor of bone (GCTB). Through the histopathological similarities between osteoporosis and GCTB, the biological functions of exogenous RUNXS were demonstrated in GCTB cell lines. This generated awareness of the molecular mechanism of the biogenesis and metastasis of GCTB, as well as showing the pathways and processes involved in this study. This research also expected to provide hints for the clinical treatment of patients with GCTB, to release the tumor burden and reduce the recurrence rate and metastasis of patients with this condition.

METHODS

The expression of RUNX2 in the tumors was verified by Western Blot, qRT-PCR and immunohistochemistry, compared with the normal tissues' adjacent tumors. Subsequently, the plasmids expressing RUNX2 were constructed, amplified and transfected into the 0404 cell line through transfection kits (0.4, 0.8, 1.6, 2.4 ng/μl). After that, the proliferation, migration, invasion, cellular viability and apoptosis of 0404 cell lines were examined by EDU assay, wound healing assay, transwell assay, annexin v staining, and CCK8 assay, respectively.

RESULTS

The messenger RNA (mRNA) level of RUNX2 in tumors was over 100 folds more than the normal tissues. The protein level of tumors upregulated 8.32(±4.41) folds relatively. After the transfection of RUNX2 overexpressed plasmids into the 0404 cell line, the mRNA level of RUNX2 increased approximately 530.11(±24.87), 1117.96(±77.68), 2835.09(±45.22) and 4781.51(±79.37) folds respectively, and the protein level was upregulated about 4.12(±1.15), 16.73(±1.63), 21.53(±2.41) and 23.39(±0.85) folds respectively. The proliferation of 0404 cells was inhibited by 2.13(±1.02)% of 1.6 ng/μl group and 3.03(±1.76)% of 2.4 ng/μl group. And the migration was inhibited about 45.56(±6.13)%, 50.79(±5.27)%, 63.15(±8.62)% and 93.90(±3.65)% respectively. The invasion was decreased about 14.49(±5.4)%, 37.02(±6.52)%, 42.24(±2.59)% and 48.97(±10.61)% respectively. Meanwhile, FITC Annexin V/PI apoptosis assay demonstrated that RUNX2 plasmids could promote apoptosis rate around 4.15(±0.27)%, 5.07(±0.27)%, 7.61(±0.45)% and 11.32(±1.02)% respectively, and CCK8 proved these plasmids could weaken cellular viability in a concentration-dependent manner with the time passing.

CONCLUSIONS

RUNX2 is highly expressed in giant cell tumors of bone. The RUNX2 overexpressed plasmids we constructed could be successfully transfected into 0404 cell line. Far more importantly, the exogenous RUNX2 can seriously block the biological functions of 0404 cell line in a concentration-dependent manner, including proliferation, translocation, invasion, cellular viability, and apoptosis. Meanwhile, the mechanism was hypothesized and discussed in the article.

Metabolomics profiling of cleidocranial dysplasia

OBJECTIVES

Cleidocranial dysplasia (CCD) is a rare autosomal-dominantly inherited skeletal dysplasia that is predominantly associated with heterozygous mutations of RUNX2. However, no information is available regarding metabolic changes associated with CCD at present.

MATERIALS AND METHODS

We analyzed members of a CCD family and checked for mutations in the RUNX2 coding sequence using the nucleotide BLAST program. The 3D protein structure of mutant RUNX2 was predicted by I-TASSER. Finally, we analyzed metabolites extracted from plasma using LC-MS/MS.

RESULTS

We identified a novel mutation (c.1061insT) that generates a premature termination in the RUNX2 coding region, which, based on protein structure prediction models, likely alters the protein's function. Interestingly, metabolomics profiling indicated that 30 metabolites belonging to 13 metabolic pathways were significantly changed in the CCD patients compared to normal controls.

CONCLUSIONS

The results highlight interesting correlations between a RUNX2 mutation, metabolic changes, and the clinical features in a family with CCD. The results also contribute to our understanding of the pathogenetic processes underlying this rare disorder.

CLINICAL RELEVANCE

This study provides the first metabolomics profiling in CCD patients, expands our insights into the pathogenesis of the disorder, may help in diagnostics and its refinements, and may lead to novel therapeutic approaches to CCD.

CCR4 promotes metastasis via ERK/NF-κB/MMP13 pathway and acts downstream of TNF-α in colorectal cancer

Chemokines and chemokine receptors are causally involved in the metastasis of human malignancies. As a crucial chemokine receptor for mediating immune homeostasis, however, the role of CCR4 in colorectal cancer (CRC) remains unknown. In this study, we found that high expression of CCR4 in CRC tissues was correlated with shorter overall survival and disease free survival. In vitro and in vivo experiments revealed that silencing CCR4 attenuated the invasion and metastasis of CRC cells, whereas ectopic overexpression of CCR4 contributed to the forced metastasis of these cells. We further demonstrated that matrix metalloproteinase 13 (MMP13) played an important role in CCR4-mediated cancer cell invasion, which is up-regulated by ERK/NF-κB signaling. Positive correlation between CCR4 and MMP13 expression was also observed in CRC tissues. Moreover, our investigations showed that the level of CCR4 could be induced by TNF-α dependent of NF-κB activation in CRC cells. CCR4 might be implicated in TNF-α-regulated cancer cells metastasis. Combination of CCR4 and TNF-α is a more powerful prognostic marker for CRC patients. These findings suggest that CCR4 facilitates metastasis through ERK/NF-κB/MMP13 signaling and acts as a downstream target of TNF-α. CCR4 inhibition may be a promising therapeutic option for suppressing CRC metastasis.

Genome-Wide Transcriptome Profiling of the Neoplastic Giant Cell Tumor of Bone Stromal Cells by RNA Sequencing

Giant cell tumor of bone (GCTB) is the most common non-malignant primary bone tumor reported in Hong Kong. Failure of treatment in advanced GCTB with aggressive local recurrence remains a clinical challenge. In order to reveal the molecular mechanism underlying the pathogenesis of this tumor, we aimed to examine the transcriptome profiling of the neoplastic stromal cells of GCTB in this study. RNA-sequencing was performed on three GCTB stromal cell samples and one bone marrow-derived MSC sample and 174 differentially expressed genes (DEGs) were identified between these two cell types. The top five up-regulated genes are SPP1, F3, TSPAN12, MMP13, and LGALS3BP and further validated by qPCR and Western Blotting. Knockdown of SPP1 was found to induce RUNX2 and OPG expression in GCTB stromal cells but not the MSCs. Ingenuity pathway analysis (IPA) of the 174 DEGs revealed significant alternations in 23 pathways; variant calling analysis revealed 1915 somatic variants of 384 genes with high or moderate impacts. Interestingly, four canonical pathways were found overlapping in both analyses; from which VEGFA, CSF1, PLAUR, and F3 genes with somatic mutation were found up-regulated in GCTB stromal cells. The STRING diagram showed two main clusters of the DEGs; one cluster of histone genes that are down-regulated in GCTB samples and another related to osteoblast differentiation, angiogenesis, cell cycle progression, and tumor growth. The DEGs and somatic mutations found in our study warrant further investigation and validation, nevertheless, our study add new insights in the search for new therapeutic targets in treating GCTB. J. Cell. Biochem. 118: 1349-1360, 2017. © 2016 Wiley Periodicals, Inc.

Clival giant cell tumor - A rare case report and review of literature with respect to current line of management

Giant-cell tumor (GCT) involving the skull base is rare. Sphenoid bone is the most commonly involved bone followed by petrous temporal bone. Histopathology and radiological features of these lesions are similar to GCT involving bone elsewhere. Unlike other sites, skull base is not an ideal site for the radical surgery. Hence adjuvant treatment has pivotal role. Radiation therapy with intensity-modulated radiation therapy, stereotactic radiosurgery or chemotherapy with adriamycin are promising as described in some case reports. Bisphosphonates showed good control in local recurrence. In vitro studies with Zolendronate loaded bone cement and phase 2 trials of Denosumab showed hopeful results, may be useful in future.

Runx2 and microRNA regulation in bone and cartilage diseases

The homeostasis of skeletal tissues requires tight regulation of a variety of signaling pathways, and the onset and progression of skeletal diseases are often caused by signaling abnormalities. MicroRNAs (miRNAs) are short noncoding RNA molecules that have emerged as a new dimension of gene regulation. MiRNAs have been shown to play an important role in the regulation of the differentiation of embryonic and hematopoietic stem cells. However, the role of specific miRNAs and their target genes has not been fully defined in the regulation of mesenchymal stem cells. Runx2 is a key transcription factor controlling MSC differentiation and bone and cartilage function. This article reviews work on Runx2 and miRNA regulation in bone and cartilage diseases.

microRNA and Bone Cancer

MicroRNA molecules have a variety of roles in cellular development and proliferation processes, including normal osteogenesis. These effects are exerted through post-translational inhibition of target genes. Altered miRNA expression has been demonstrated in several cancers, both in the tumor tissue and in the peripheral circulation. This may influence carcinogenesis if the specific miRNA targets are encoded by tumor suppressor genes or oncogenes. To date, most research investigating the role of microRNAs and primary bone tumors has focused on osteosarcoma and Ewing sarcoma. Several microRNAs including the miR-34 family have been implicated in osteosarcoma tumorigenesis via effects on the Notch signaling pathway. Progression, invasion, and metastasis of osteosarcoma tumor cells is also influenced by microRNA expression. In addition, microRNA expression may affect the response to chemotherapy in osteosarcoma and thus hold potential for future use as either a prognostic indicator or a therapeutic target. The EWS-FLI1 fusion protein produced in Ewing sarcoma has been shown to induce changes in miRNA expression. MicroRNA expression profiling may have some potential for prediction of disease progression and survival in Ewing sarcoma. There is limited evidence to support a role for microRNAs in other primary bone tumors, either malignant or benign; however, early work is suggestive of involvement in chondrosarcoma, multiple osteochondromatosis, and giant cell tumors of bone.

Bortezomib Inhibits Giant Cell Tumor of Bone through Induction of Cell Apoptosis and Inhibition of Osteoclast Recruitment, Giant Cell Formation, and Bone Resorption

Giant cell tumor of bone (GCTB) is a rare and highly osteolytic bone tumor that usually leads to an extensive bone lesion. The purpose of this study was to discover novel therapeutic targets and identify potential agents for treating GCTB. After screening the serum cytokine profiles in 52 GCTB patients and 10 normal individuals using the ELISA assay, we found that NF-κB signaling-related cytokines, including TNFα, MCP-1, IL1α, and IL17A, were significantly increased in GCTB patients. The results were confirmed by IHC that the expression and activity of p65 were significantly increased in GCTB patients. Moreover, all of the NF-κB inhibitors tested suppressed GCTB cell growth, and bortezomib (Velcade), a well-known proteasome inhibitor, was the most potent inhibitor in blocking GCTB cells growth. Our results showed that bortezomib not only induced GCTB neoplastic stromal cell (NSC) apoptosis, but also suppressed GCTB NSC-induced giant cell differentiation, formation, and resorption. Moreover, bortezomib specifically suppressed GCTB NSC-induced preosteoclast recruitment. Furthermore, bortezomib ameliorated GCTB cell-induced bone destruction in vivo As a result, bortezomib suppressed NF-κB-regulated gene expression in GCTB NSC apoptosis, monocyte migration, angiogenesis, and osteoclastogenesis. Particularly, the inhibitory effects of bortezomib were much better than zoledronic acid, a drug currently used in treating GCTB, in our in vitro experimental paradigms. Together, our results demonstrated that NF-κB signaling pathway is highly activated in GCTB, and bortezomib could suppress GCTB and osteolysis in vivo and in vitro, indicating that bortezomib is a potential agent in the treatment of GCTB. Mol Cancer Ther; 15(5); 854-65. ©2016 AACR.

Differential Expression of ADAM23, CDKN2A (P16), MMP14 and VIM Associated with Giant Cell Tumor of Bone

Though benign, giant cell tumor of bone (GCTB) can become aggressive and can exhibit a high mitotic rate, necrosis and rarely vascular invasion and metastasis. GCTB has unique histologic characteristics, a high rate of multinucleated cells, a variable and unpredictable growth potential and uncertain biological behavior. In this study, we sought to identify genes differentially expressed in GCTB, thus building a molecular profile of this tumor. We performed quantitative real-time polymerase chain reaction (qPCR), immunohistochemistry and analyses of methylation to identify genes that are putatively associated with GCTB. The expression of the ADAM23 and CDKN2A genes was decreased in GCTB samples compared to normal bone tissue, measured by qPCR. Additionally, a high hypermethylation frequency of the promoter regions of ADAM23 and CDKN2A in GCTB was observed. The expression of the MAP2K3, MMP14, TIMP2 and VIM genes was significantly higher in GCTB than in normal bone tissue, a fact that was confirmed by qPCR and immunohistochemistry. The set of genes identified here furthers our understanding of the molecular basis of GCTB.

A Translational Study of the Neoplastic Cells of Giant Cell Tumor of Bone Following Neoadjuvant Denosumab

BACKGROUND

Giant cell tumor of bone is a primary bone tumor that is treated surgically and is associated with high morbidity in many cases. This tumor consists of giant cells expressing RANK (receptor activator of nuclear factor-κB) and mesenchymal spindle-like stromal cells expressing RANKL (RANK ligand); the interaction of these cells leads to bone resorption. Denosumab is a monoclonal antibody that binds RANKL and directly inhibits osteoclastogenesis. Clinical studies have suggested clinical and histological improvement when denosumab was administered to patients with a giant cell tumor. However, no studies have yet examined the viability and functional characteristics of tumor cells following denosumab treatment.

METHODS

Specimens were obtained from six patients with a histologically confirmed giant cell tumor. Two of the patients had been treated with denosumab for six months. Primary cultures of stromal cells from fresh tumor tissue were established. Cell proliferation was measured over a two-day time course. The expression of RANKL and osteoprotegerin was analyzed with use of real-time PCR (polymerase chain reaction).

RESULTS

Histological specimens from both patients who had completed denosumab treatment showed the absence of giant cells but persistence of stromal cells. Cell proliferation studies indicated that proliferation of stromal cells cultured from clinical specimens following denosumab treatment was approximately 50% slower than that of specimens from untreated patients. The expression of RANKL in the specimens from the treated patients was almost completely eliminated.

CONCLUSIONS

Once the giant cell tumor tissue was no longer exposed to denosumab, the stromal cells continued to proliferate in vitro, albeit to a lesser degree. However, they also showed almost complete loss of RANKL expression.

CLINICAL RELEVANCE

It is clear that treatment with denosumab only partially addresses the therapeutic need of patients with a giant cell tumor by wiping out the osteoclasts but leaving the neoplastic stromal cells proliferative.

The multidisciplinary management of giant cell tumor of bone

Giant cell tumor of bone is a locally aggressive lesion with a predilection for local recurrence, and in a small proportion of patients, metastatic disease can develop. Surgery is the mainstay of management for extremity-based lesions. For tumors located in challenging anatomical locations such as the sacrum and spine however, surgery may be associated with unacceptable functional morbidity. There are limited data regarding other treatment modalities such as radiation therapy, cytotoxic chemotherapy, interferon and bisphosphonates. Serial arterial embolization can be effective in some cases. Recent evidence has demonstrated denosumab to be a promising agent in the treatment of unresectable or metastatic disease.

MiR-126-5p regulates osteoclast differentiation and bone resorption in giant cell tumor through inhibition of MMP-13

Giant cell tumor (GCT) of bone is an aggressive skeletal tumor characterized by localized bone resorption. Matrix metalloproteinase-13 (MMP-13) is the principal proteinase expressed by the stromal cells of GCT (GCTSCs) and also considered to play a crucial role in formation of the osteolytic lesion in GCT. However, the exact mechanism of the regulation of MMP-13 expression in GCTSCs was unknown. In this study, we identified miR-126-5p was significantly downregulated in GCTSCs and affect osteoclast (OC) differentiation and bone resorption by repressing MMP-13 expression at the post-transcriptional level. Thus, our studies show that miR-126-5p plays an important physiological role in multinucleated giant cell formation and osteolytic lesion in GCT.

Parathyroid hormone-related protein (PTHrP) modulates adhesion, migration and invasion in bone tumor cells

Parathyroid-hormone-related protein (PTHrP) has been shown to be an important factor in osteolysis in the setting of metastatic carcinoma to the bone. However, PTHrP may also be central in the setting of primary bone tumors. Giant cell tumor of bone (GCT) is an aggressive osteolytic bone tumor characterized by osteoclast-like giant cells that are recruited by osteoblast-like stromal cells. The stromal cells of GCT are well established as the only neoplastic element of the tumor, and we have previously shown that PTHrP is highly expressed by these cells both in vitro and in vivo. We have also found that the stromal cells exposed to a monoclonal antibody to PTHrP exhibited rapid plate detachment and quickly died in vitro. Therefore, PTHrP may serve in an autocrine manner to increase cell proliferation and promote invasive properties in GCT. The purpose of this study was to use transcriptomic microarrays and functional assays to examine the effects of PTHrP neutralization on cell adhesion, migration and invasion. Microarray and proteomics data identified genes that were differentially expressed in GCT stromal cells under various PTHrP treatment conditions. Treatment of GCT stromal cells with anti-PTHrP antibodies showed a change in the expression of 13 genes from the integrin family relative to the IgG control. Neutralization of PTHrP reduced cell migration and invasion as evidenced by functional assays. Adhesion and anoikis assays demonstrated that although PTHrP neutralization inhibits cell adhesion properties, cell detachment related to PTHrP neutralization did not result in associated cell death, as expected in mesenchymal stromal cells. Based on the data presented herein, we conclude that PTHrP excreted by GCT stromal cells increases bone tumor cell local invasiveness and migration.

Myofibroblastic differentiation of stromal cells in giant cell tumor of bone: an immunohistochemical and ultrastructural study

The nature of the mononuclear stromal cells (MSCs) in giant cell tumor of bone (GCTB) has not been thoroughly investigated. The purpose of this study was to evaluate the degree and significance of myofibroblastic differentiation in 18 cases of GCTB by immunohistochemistry (IH) and/or electron microscopy (EM). All immunostained cases were found positive for smooth muscle actin (SMA) and/or muscle specific actin (MSA), most in 1-33% of the MSCs. Ultrastructurally, most MSCs were fibroblasts, and a significant number of cells displayed myofibroblastic differentiation. Myofibroblasts are an important component of MSCs in GCTB. The myofibroblastic population may be responsible in part for the production of matrix metalloproteinases (MMPs), which probably play a role in bone destruction, tumor aggression, and recurrence.

Regulators of skeletal development: a cluster analysis of 206 bone tumors reveals diagnostically useful markers

The molecules Indian hedgehog (IHH), SP7 (also known as osterix), sex-determining region Y-box 9 (SOX9), runt-related transcription factor 2 (RUNX2) and TWIST1 regulate the normal differentiation of osteo- and chondrogenic cells from precursors during skeletal development and remodeling. The aberrant function of the same molecules has been implicated in the pathogenesis of bone tumors. Preliminary studies suggest that antibodies against these molecules have practical, diagnostic or prognostic utility in tumors. However, a comprehensive analysis of the expression of these molecules in a large, diverse set of bone tumors has yet to be reported. The goals of this study were to compare the immunohistochemical profiles of IHH, SP7, SOX9, RUNX2 and TWIST1 among bone tumors and to determine the optimum panel for diagnostic utility. Tissue microarrays prepared from 206 undecalcified tumors (71 osteosarcomas, 26 osteoblastomas/osteoid osteomas, 50 giant cell tumors, 5 chondromyxoid fibromas and 54 chondroblastomas) were stained with antibodies to IHH, SP7, SOX9, RUNX2 and TWIST1. The stains were scored for intensity (0-3+) and distribution. The results were analyzed by cluster analysis. Optimum antibody panels for diagnostic sensitivity and specificity were calculated. Analysis revealed six main clusters that corresponded well to tumor types and suggested a close relationship between the stromal cells of giant cell tumor and the osteoblasts of osteosarcoma. The expression profile of chondromyxoid fibroma and chondroblastoma also suggested related differentiation. The distribution of osteoblastomas and osteoid osteomas was more heterogeneous. RUNX2, SOX9 and TWIST1 represented the most sensitive and specific immunohistochemical panel to distinguish among these diagnoses with the limitation that no result could discriminate between chondroblastoma and chondromyxoid fibroma. IHH and SP7 did not yield additional utility.

Transcriptomic and proteomic analyses in bone tumor cells: Deciphering parathyroid hormone-related protein regulation of the cell cycle and apoptosis

Giant cell tumor of bone (GCT) is an aggressive skeletal tumor characterized by local bone destruction, high recurrence rates, and metastatic potential. Previous works in our laboratory, including functional assays, have shown that neutralization of parathyroid hormone-related protein (PTHrP) in the cell environment inhibits cell proliferation and induces cell death in GCT stromal cells, indicating a role for PTHrP in cell propagation and survival. The objective of this study was to investigate the global gene and protein expression patterns of GCT cells in order to identify the underlying pathways and mechanisms of neoplastic proliferation provided by PTHrP in the bone microenvironment. Primary stromal cell cultures from 10 patients with GCT were used in this study. Cells were exposed to optimized concentrations of either PTHrP peptide or anti-PTHrP neutralizing antiserum and were analyzed with both cDNA microarray and proteomic microarray assays in triplicate. Hierarchical clustering and principal component analyses confirmed that counteraction of PTHrP in GCT stromal cells results in a clear-cut gene expression pattern distinct from all other treatment groups and the control cell line human fetal osteoblast (hFOB). Multiple bioinformatics tools were used to analyze changes in gene/protein expression and identify important gene ontologies and pathways common to this anti-PTHrP-induced regulatory gene network. PTHrP neutralization interferes with multiple cell survival and apoptosis signaling pathways by triggering both death receptors and cell cycle-mediated apoptosis, particularly via the caspase pathway, TRAIL pathway, JAK-STAT signaling pathway, and cyclin E/CDK2-associated G1/S cell cycle progression. These findings indicate that PTHrP neutralization exhibits anticancer potential by regulating cell-cycle progression and apoptosis in bone tumor cells, with the corollary being that PTHrP is a pro-neoplastic factor that can be targeted in the treatment of bone tumors.

Runt-related transcription factor 2 in human colon carcinoma: a potent prognostic factor associated with estrogen receptor

Runt-related transcription factor 2 (RUNX2) belongs to the RUNX family of heterodimeric transcription factors, and is mainly associated with osteogenesis. Previous in vitro studies demonstrated that RUNX2 increased the cell proliferation of mouse and rat colon carcinoma cells but the status of RUNX2 has remained unknown in human colon carcinoma. Therefore, we examined clinical significance and biological functions of RUNX2 in colon carcinoma. RUNX2 immunoreactivity was examined in 157 colon carcinoma tissues using immunohistochemistry. RUNX2 immunoreactivity was evaluated as percentage of positive carcinoma cells [i.e., labeling index (LI)]. We used SW480 and DLD-1 human colon carcinoma cells, expressing estrogen receptor-β (ER) in subsequent in vitro studies. RUNX2 immunoreactivity was detected in colon carcinoma cells, and the median value of RUNX2 LI was 67%. RUNX2 LI was significantly associated with Dukes' stage, liver metastasis and ERβ status. In addition, RUNX2 LI was significantly associated with adverse clinical outcome of the colon carcinoma patients, and turned out an independent prognostic factor following multivariate analysis. Results of in vitro studies demonstrated that both SW480 and DLD-1 cells transfected with small interfering RNA against RUNX2 significantly decreased their cell proliferation, migration and invasive properties. In addition, RUNX2 mRNA level was significantly decreased by ER antagonist in these two cells. These findings all suggest that RUNX2 is a potent prognostic factor in human colon carcinoma patients through the promotion of cell proliferation and invasion properties, and is at least partly upregulated by estrogen signals through ERβ of carcinoma cells.

The role of TWIST as a regulator in giant cell tumor of bone

Giant cell tumor of bone (GCT) is an aggressive tumor consisting of multinucleated osteoclast-like giant cells and proliferating osteoblast-like stromal cells. Our group has reported that the stromal cells express high levels of the bone resorbing matrix metalloproteinase (MMP)-13, and that this expression is regulated by the osteoblast transcription factor Runx2. The purpose of this study was to determine the upstream regulation of Runx2 in GCT cells. Using GCT stromal cells obtained from patient specimens, we demonstrated that TWIST, a master osteogenic regulator, was highly expressed in all GCT specimens. TWIST overexpression downregulated Runx2 expression whereas TWIST siRNA knockdown resulted in Runx2 and MMP-13 upregulation. Interestingly, cells obtained from a GCT lung metastasis showed a reverse regulatory pattern between TWIST and Runx2. In mutational analysis, we revealed a point mutation (R154S) at the Helix2 domain of TWIST. This TWIST mutation may be an essential underlying factor in the development and pathophysiology of these tumors in that they lead to inappropriate TWIST downregulation of Runx2, arrested osteoblastic differentiation, and the maintenance of an immature and neoplastic phenotype.

PTHrP induces autocrine/paracrine proliferation of bone tumor cells through inhibition of apoptosis

Giant Cell Tumor of Bone (GCT) is an aggressive skeletal tumor characterized by local bone destruction, high recurrence rates and metastatic potential. Previous work in our lab has shown that the neoplastic cell of GCT is a proliferating pre-osteoblastic stromal cell in which the transcription factor Runx2 plays a role in regulating protein expression. One of the proteins expressed by these cells is parathryroid hormone-related protein (PTHrP). The objectives of this study were to determine the role played by PTHrP in GCT of bone with a focus on cell proliferation and apoptosis. Primary stromal cell cultures from 5 patients with GCT of bone and one lung metastsis were used for cell-based experiments. Control cell lines included a renal cell carcinoma (RCC) cell line and a human fetal osteoblast cell line. Cells were exposed to optimized concentrations of a PTHrP neutralizing antibody and were analyzed with the use of cell proliferation and apoptosis assays including mitochondrial dehydrogenase assays, crystal violet assays, APO-1 ELISAs, caspase activity assays, flow cytometry and immunofluorescent immunohistochemistry. Neutralization of PTHrP in the cell environment inhibited cell proliferation in a consistent manner and induced apoptosis in the GCT stromal cells, with the exception of those obtained from a lung metastasis. Cell cycle progression was not significantly affected by PTHrP neutralization. These findings indicate that PTHrP plays an autocrine/paracrine neoplastic role in GCT by allowing the proliferating stromal cells to evade apoptosis, possibly through non-traditional caspase-independent pathways. Thus PTHrP neutralizing immunotherapy is an intriguing potential therapeutic strategy for this tumor.

AP-1 as a Regulator of MMP-13 in the Stromal Cell of Giant Cell Tumor of Bone

Matrix-metalloproteinase-13 (MMP-13) has been shown to be an important protease in inflammatory and neoplastic conditions of the skeletal system. In particular, the stromal cells of giant cell tumor of bone (GCT) express very high levels of MMP-13 in response to the cytokine-rich environment of the tumor. We have previously shown that MMP-13 expression in these cells is regulated, at least in part, by the RUNX2 transcription factor. In the current study, we identify the expression of the c-Fos and c-Jun elements of the AP-1 transcription factor in these cells by protein screening assays and real-time PCR. We then used siRNA gene knockdown to determine that these elements, in particular c-Jun, are upstream regulators of MMP-13 expression and activity in GCT stromal cells. We conclude that there was no synergy found between RUNX2 and AP-1 in the regulation of the MMP13 expression and that these transcription factors may be independently regulated in these cells.

Differentially expressed genes in giant cell tumor of bone

Giant cells tumors of bone (GCTB) are benign in nature but cause osteolytic destruction with a number of particular characteristics. These tumors can have uncertain biological behavior often contain a significant proportion of highly multinucleated cells, and may show aggressive behavior. We have studied differential gene expression in GCTB that may give a better understanding of their physiopathology, and might be helpful in prognosis and treatment. Rapid subtractive hybridization (RaSH) was used to identify and measure novel genes that appear to be differentially expressed, including KTN1, NEB, ROCK1, and ZAK using quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry in the samples of GCTBs compared to normal bone tissue. Normal bone was used in the methodology RaSH for comparison with the GCTB in identification of differentially expressed genes. Functional annotation indicated that these genes are involved in cellular processes related to their tumor phenotype. The differential expression of KTN1, ROCK1, and ZAK was independently confirmed by qRT-PCR and immunohistochemistry. The expression of the KTN1 and ROCK1 genes were increased in samples by qRT-PCR and immunohistochemistry, and ZAK had reduced expression. Since ZAK have CpG islands in their promoter region and low expression in tumor tissue, their methylation pattern was analyzed by MSP-PCR. The genes identified KTN1, ROCK1, and ZAK may be responsible for loss of cellular homeostasis in GCTB since they are responsible for various functions related to tumorigenesis such as cell migration, cytoskeletal organization, apoptosis, and cell cycle control and thus may contribute at some stage in the process of formation and development of GCTB.

Overexpression of matrix metalloproteinase (MMP)-1 and -9 in central giant cell lesions of the jaws: implications for clinical behavior

OBJECTIVE

The aim of this study was to investigate the relationship between the immunohistochemical expression of MMP-1 and MMP-9 with the clinical behavior of central giant cell lesions (CGCLs) of the jaws.

STUDY DESIGN

Paraffin-embedded tissue from 30 aggressive and 12 nonaggressive CGCLs was assessed for the expression of MMP-1 and MMP-9 using immunohistochemistry.

RESULTS

Although cellular immunolocalization patterns of MMP-1 and MMP-9 were similar, mean values of expression estimation/SID scores of each protease were significantly higher in aggressive CGCLs in comparison with nonaggressive lesions. Moreover, linear regression analysis showed that there was a reasonably good correlation not only between the expression estimation but also among SID scores of the 2 proteolytic enzymes.

CONCLUSION

The findings of this study suggest a role for MMP-1 and MMP-9 in the resorptive activity of different cellular groups in CGCLs and indicate that differences in immunoreactivity of these 2 proteolytic enzymes may underlie the distinct clinical behavior.

Runx2 in human breast carcinoma: its potential roles in cancer progression

Runx2 has been proposed as one of the pivotal factors in the process of osteogenesis and metastasis in human malignancies including breast cancer, but its details have not been evaluated. Therefore, in this study, we evaluated its expression in human breast cancer using immunohistochemistry. One hundred and thirty-seven formalin-fixed and paraffin-embedded breast cancer specimens were used in this analysis of immunohistochemical study. Immunoreactivity was evaluated using the labeling index (LI). Runx2 immunoreactivity was detected in both carcinoma and stromal cells, as well as non-pathological ductal cells. The nuclear LI of Runx2 in carcinoma cells was associated with the clinical stage, histological grade and HER2 status of the patients examined. In addition, among the patients not associated with distant metastasis, those with high Runx2 LI demonstrated a significantly worse clinical outcome than those with a low LI. This was more pronounced in the group of estrogen receptor (ER)-negative cases. In addition, both univariate and multivariate analyses demonstrated that the Runx2 LI in breast carcinoma cells turned out an independent prognostic factor. Results of our present study demonstrated that Runx2 plays very important roles in the progression of breast cancer, especially in those of ER-negative cases.

Evidence for the role of matrix metalloproteinase-13 in bone resorption by giant cell tumor of bone

Giant cell tumor of bone (GCT) is an aggressively osteolytic primary bone tumor that is characterized by the presence of abundant multinucleated osteoclast-like giant cells, hematopoietic monocytes, and a distinct mesenchymal stromal cell component. Previous work in our laboratory has shown that matrix metalloproteinase (MMP)-13 is the principal proteinase expressed by the stromal cells of GCT. The release of cytokines, particularly interleukin-1beta, by the giant cells of GCT acts on stromal cells to stimulate a surge in MMP-13 secretion. The purpose of this study was to determine the bone resorption capabilities of the cellular elements of GCT and the significance of the MMP-13 expression involved in GCT bone resorption. We present a 3-dimensional histomorphometric technique developed to analyze resorption pit depth and yield an accurate measurement of bone resorption with a direct physical view of lacunae on bone slices. In this study, we demonstrate that the mesenchymal stromal cells and the multinucleated giant cells of GCT are independently capable of bone resorption. However, coculture of these 2 cell fractions shows a synergistic increase in bone resorption. In addition, inhibition of MMP-13 reduces resorptive activity of the cells indicating that MMP-13 likely plays an important role in this tumor. This cell-cell cooperation involves giant cell-derived cytokine up-regulation of MMP-13 in the stromal cells, which in turn assists the giant cells in bone resorption. Future research will involve elucidation of the role of cell-cell/matrix communication pathways in bone resorption and tumorigenesis in GCT.

Matrix Metalloproteinase Activity in the Stromal Cell of Giant Cell Tumor of Bone

Giant cell tumor of bone (GCT) is a destructive and potentially metastatic bone tumour in which the characteristic giant cells have classically been considered the culprits in bone destruction. However, the neoplastic element of the tumour consists of propagative osteoblast-like stromal cells that may play a role in bone resorption. The objectives of this study were to determine the expression and activity of the gelatinases, matrix metalloproteinase (MMP)-2 and -9, in GCT stromal cells, and to determine if these cells have bone-resorbing capabilities. We performed immunohistochemistry on clinical specimens, and real-time polymerase chain reaction (PCR) and zymography on cell lysates and conditioned media from cultured clinical GCT specimens in order to evaluate the expression and activity of MMP-2 and-9 in GCT stromal cells. Our results support the fact that GCT stromal cells express MMP-2 and MMP-9 and are capable of gelatin degradation in vitro. These cells may therefore play a role in bone destruction in GCT.