Expression of osteoclast differentiation signals by stromal elements of giant cell tumors

Narlumosbart: First Approval

Narlumosbart () is a recombinant, fully human, anti-receptor activator of nuclear factor kappa-Β ligand (RANKL) IgG4 monoclonal antibody being developed by CSPC Pharmaceutical and its wholly owned subsidiary Shanghai Jinmante Biotechnology for the treatment of giant cell tumour of bone (GCTB), bone metastases from solid tumours and osteoporosis. The RANK/RANKL signalling pathway plays a pivotal role in osteoclastogenesis and in the pathogenesis of GCTB. Narlumosbart specifically binds to RANKL and blocks the interaction of RANKL with RANK, thus inhibiting osteoclastogenesis and bone resorption by osteoclasts. In September 2023, narlumosbart received conditional first approval in China for the treatment of adults with GCTB that is unresectable or when surgical resection would result in severe functional disability. Clinical studies of narlumosbart for bone metastases, postmenopausal osteoporosis and glucocorticoid-induced osteoporosis are underway in China. This article summarizes the milestones in the development of narlumosbart leading to this first approval for the treatment of adults with GCTB.

Denosumab for giant cell tumors of bone from 2010 to 2022: a bibliometric analysis

Giant cell tumors of the bone (GCTB) are considered moderately malignant bone tumors. Denosumab, as a neoadjuvant therapy, provides new possibilities for treating GCTB. However, even after multiple studies and long-term clinical trials, there are limitations in the treatment process. Research data and Medical Subject Headings terms related to denosumab and GCTB were collected from January 2010 to October 2022 using the Web of Science and MeSH ( https://meshb.nlm.nih.gov ) browsers. These data were imported into CiteSpace and VOSviewer softwares for bibliometric analysis. Overall, 445 publications on denosumab and GCTB were identified. Over the last 12 years, the growth rate of the total number of publications has remained relatively stable. The USA published the highest number of articles (83) and had the highest centrality (0.42). Amgen Inc. and Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) First Ortoped Rizzoli were identified as the most influential institutions. Many authors have made outstanding contributions to this field. Lancet Oncology had the highest journal impact factor (54.433). Local recurrence and drug dosage are current research hotspots, and future development trends will mainly focus on prognostic markers of GCTB and the development of new therapies. Further research is required to analyze denosumab's safety and efficacy and understand its local recurrence of GCTB, to identify the optimal dose. Future progress in this field will likely focus on exploring new diagnostic and recurrence markers to monitor disease progression and examine new therapeutic targets and treatment strategies.

The Role of procollagen type 1 amino-terminal propertied (P1NP) Cytochrome P450 (CYPs) and Osteoprotegerin (OPG) as Potential Bone function markers in Prostate Cancer Bone Metastasis

Background: Procollagen type I amino-terminal propeptide (PINP) is often present during osteoblast development and could be a biomarker of early bone development. Osteoprotegerin (OPG) may protect tumor cells from apoptosis. Cytochrome P450 enzymes help tumor development and treatment (CYPs). Cytochrome P450 activates and deactivates anticancer drugs and procarcinogens.

Objective: The study examined the amounts of a diagnostic marker of bone formation, the amino terminal propeptide of type I procollagen (PINP), Osteoprotegerin (OPG), and P450, in prostate cancer patients at different stages and its ability to detect osteoblastic metastases.

Methods: ELISA was used to measure PINP, OPG, and P450 levels in 30 prostate cancer patients. (n = 32) and healthy men’s serum (n = 36).

Results: Prostate cancer patients had higher blood levels of PINP, OPG, and P450 than healthy persons (301.3±134.9, 980±467.2, and 84.2±28.4 pg/mL, respectively). Compared to I+II prostate cancer patients, III+IV patients showed higher serum PINP, OPG, and P450 levels (P 0.001). OPG, P450, and PINP had statistically significant Area under the ROC curve (0.9467, P= 0.0001, 0.91, P= 0.0001, and 0.6977, P= 0.4035) in prostate cancer patients.

Conclusions: Metastatic prostate cancer patients had greater PINP, OPG, and P450 levels, according to our findings. PINP, OPG, and P450 levels may affect prostate cancer progression. These findings imply that serum PINP, OPG, and P450 levels may predict and diagnose prostate cancer.

Bioactive glass selectively promotes cytotoxicity towards giant cell tumor of bone derived neoplastic stromal cells and induces MAPK signalling dependent autophagy

Giant cell tumors of bone (GCTB) are associated with massive bone destructions and high recurrence rates. In a previous study, we observed cytotoxic effects of three different compositions of bioactive glasses (BGs) towards GCTSC but not bone marrow derived stromal cells (BMSC) indicating that BGs represent promising candidates for the development of new therapeutic approaches. In the current study we aimed to investigate the molecular mechanisms that are involved in BG induced cytotoxicity. We observed, that BG treatment was not associated with any signs of apoptosis, but rather led to a strong induction of mitogen activated protein kinases (MAPK) and, as a consequence, upregulation of several transcription factors specifically in GCTSC. Genome wide gene expression profiling further revealed a set of fifteen genes that were exclusively induced in GCTSC or induced significantly stronger in GCTSC compared to BMSC. BG treatment further induced autophagy that was significantly more pronounced in GCTSC compared to BMSC and could be inhibited by MAPK inhibitors. Together with the known osteogenic properties of BGs our findings support the suitability of BGs as therapeutic agents for the treatment of GCTB. However, these data have to be verified under in vivo conditions.

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Bioactive glasses (BG) are selectively cytotoxic towards neoplastic stromal cells.

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BG induced cell death is independent from apoptosis.

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BG activates mitogen activated protein kinases and transcription factors.

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BG trigger differential gene expression in neoplastic versus normal cells.

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BG induce autophagy.

The Osteoclast Traces the Route to Bone Tumors and Metastases

Osteoclasts are highly specialized cells of the bone, with a unique apparatus responsible for resorption in the process of bone remodeling. They are derived from differentiation and fusion of hematopoietic precursors, committed to form mature osteoclasts in response to finely regulated stimuli produced by bone marrow–derived cells belonging to the stromal lineage. Despite a highly specific function confined to bone degradation, emerging evidence supports their relevant implication in bone tumors and metastases. In this review, we summarize the physiological role of osteoclasts and then focus our attention on their involvement in skeletal tumors, both primary and metastatic. We highlight how osteoclast-mediated bone erosion confers increased aggressiveness to primary tumors, even those with benign features. We also outline how breast and pancreas cancer cells promote osteoclastogenesis to fuel their metastatic process to the bone. Furthermore, we emphasize the role of osteoclasts in reactivating dormant cancer cells within the bone marrow niches for manifestation of overt metastases, even decades after homing of latent disseminated cells. Finally, we point out the importance of counteracting tumor progression and dissemination through pharmacological treatments based on a better understanding of molecular mechanisms underlying osteoclast lytic activity and their recruitment from cancer cells.

Histological and immunohistochemical features and genetic alterations in the malignant progression of giant cell tumor of bone: a possible association with TP53 mutation and loss of H3K27 trimethylation

In rare cases, giant cell tumor of bone (GCTB) can undergo primary or secondary malignant transformation to malignant giant cell tumor of bone (MGCTB), but the details of the molecular alterations are still unclear. The present study aimed to elucidate the clinicopathologic and molecular features of MGCTBs based on immunohistochemistry, fluorescence in situ hybridization (FISH) and next generation sequencing (NGS) of nine MGCTBs (five primary and four secondary). Seven (78%) of 9 MGCTBs were immunohistochemically positive for H3.3 G34W. In two (22%) patients, although GCTB components were focally or diffusely positive for H3.3 G34W, their malignant components were entirely negative for H3.3 G34W, which was associated with heterozygous loss of H3F3A by FISH. NGS on four MGCTBs revealed pathogenic mutations in TP53 (n = 3), EZH2 (n = 1) and several other genes. Immunohistochemical analysis of the nine MGCTBs confirmed the p53 nuclear accumulation (n = 5) and loss of H3K27me3 expression (n = 3) and showed that they were mutually exclusive. In addition, four (80%) of five cases of pleomorphic or epithelioid cell-predominant MGCTBs were positive for p53, while three (75%) of four cases of spindle cell-predominant MGCTBs were negative for trimethylation at lysine 27 of histone 3 (H3K27me3). The results suggested that p53 alteration and dysfunction of histone methylation as evidenced by H3K27me3 loss may play an important role in the malignant progression of GCTB, and might contribute to the phenotype-genotype correlation in MGCTB. The combined histologic, immunohistochemical and molecular information may be helpful in part for the diagnosis of challenging cases.

New Generation of Meso and Antiprogestins (SPRMs) into the Osteoporosis Approach

Receptor activator of nuclear factor κB (RANK) and its ligand (RANKL) play key roles in bone metabolism and the immune system. The RANK/RANKL complex has also been shown to be critical in the formation of mammary epithelia cells. The female hormones estradiol and progesterone closely control the action of RANKL with RANK. Blood concentration of these sex hormones in the postmenopausal period leads to an increase in RANK/RANKL signaling and are a major cause of women's osteoporosis, characterized by altered bone mineralization. Knowledge of the biochemical relationships between hormones and RANK/RANKL signaling provides the opportunity to design novel therapeutic agents to inhibit bone loss, based on the anti-RANKL treatment and inhibition of its interaction with the RANK receptor. The new generation of both anti- and mesoprogestins that inhibit the NF-κB-cyclin D1 axis and blocks the binding of RANKL to RANK can be considered as a potential source of new RANK receptor ligands with anti-RANKL function, which may provide a new perspective into osteoporosis treatment itself as well as limit the osteoporosis rise during breast cancer metastasis to the bone.

Osteoclasts in Tumor Biology: Metastasis and Epithelial-Mesenchymal-Myeloid Transition

Osteoclast is a specialized cell that originates from monocytic lineage, communicates closely with osteoblasts under physiological conditions, participates in bone modeling and re-modeling, contributes to calcium homeostasis and osteoimmunity. In pathological conditions, it is involved in many tumors such as giant cell bone tumor (osteoclastoma), aneurysmal bone cyst, osteosarcoma, and metastatic cancers, and it usually causes local spread and progression of the tumor, working against the host. Since osteoclasts play an active role in primary bone tumors and bone metastases, the use of anti-osteoclastic agents significantly reduces the mortality and morbidity rates of patients by preventing the progression and local spread of tumors. Osteoclasts also accompany undifferentiated carcinomas of many organs, especially pancreas, thyroid, bladder and ovary. Undifferentiated carcinomas rich in osteoclasts have osteoclastoma-like histology. In these organs, osteoclastoma-like histology may accompany epithelial carcinomas, and de novo, benign and borderline tumors. Mature and immature myeloid cells, including osteoclasts, play an active role in the tumor progression in primary and metastatic tumor microenvironment, in epithelial-mesenchymal transition (EMT), mesenchymal-epithelial-transition (MET), and cancer stem cell formation. Additionally, they are the most suitable candidates for cancer cells in cell fusion due to their evolutionary fusion capabilities. Myeloid features and markers (CD163, CD33, CD68 etc.) can be seen in metastatic cancer cells. Consequently, they provide metastatic cancer cells with motility, margination, transmigration, chemotaxis, phagocytosis, angiogenesis, matrix degradation, and resistance to chemotherapy. For these reasons, we think that the concept of Epithelial-Mesencyhmal-Myeloid-Transition (EMMT) will be more accurate than EMT for cancer cells with myeloid properties.

Towards better understanding of giant cell granulomas of the oral cavity

Giant cell granulomas are enigmatic lesions of the oral cavity characterised by a peculiar combined proliferation of mononuclear and multinucleated giant cells in a mesenchymal stromal background. Central and peripheral giant cell granulomas may have similar pathogenesis and histology but differ in their location and biological behaviour. It is important to differentiate them from other giant cell lesions that can occur in the oral cavity, such as giant cell tumour of the bone, aneurysmal bone cyst, brown tumour of hyperparathyroidism, and giant cell lesions of Ramon syndrome, Noonan syndrome, neurofibromatosis and Jaffe-Campanacci syndrome. A recent insight into their molecular genetics and pathogenesis, with identification of KRAS, FGFR1 and TRPV4 mutations, allows for better diagnostic differentiation and opens the door to the use of pathway inhibitors in the treatment of recurrent or dysmorphic lesions. In this review, we provide an updated summary of the clinical and pathological features of oral cavity giant cell granulomas that help with their precise diagnosis and management.

Anti-IL17 antibody Secukinumab therapy is associated with ossification in giant cell tumor of bone: a case report of pathologic similarities and therapeutic potential similar to Denosumab

Background

Giant cell tumor of bone is a benign, locally aggressive neoplasm. Surgical resection is the preferred treatment method. However, for cases in which resection poses an increased risk to the patient, denosumab (anti-RANKL monoclonal antibody) is considered. Secukinumab is an anti-IL-17 antibody that is used in psoriatic arthritis to reduce bone resorption and articular damage.

Case presentation

One case of giant cell tumor of bone (GCTB) in a patient treated with secukinumab for psoriatic arthritis demonstrated findings significant for intra-lesional calcifications. Histologic examination showed ossification, new bone formation, and remodeling. A paucity of osteoclast type giant cells was noted. Real-time quantitative polymerase-chain-reaction (qRT-PCR) analysis revealed decreased osteoclast function compared to treatment-naive GCTB.

Conclusions

Secukinumab may play a role in bone remodeling for GCTB. Radiologists, surgeons, and pathologists should be aware of this interaction, which can cause lesional ossification. Further research is required to define the therapeutic potential of this drug for GCTB and osteolytic disease.

Recurrence Rate of Giant Cell Tumor With the Treatment of Scooping Curettage, Burr Down Technique, Phenolization, and Bone Cement

Objective: To find the recurrence and outcomes of giant cell tumors treated with scooping curettage, burr down technique, phenolization, and bone cement.

Method: We conducted a descriptive case series using a non-probability consecutive sampling technique at the Department of Orthopedics, Lahore General Hospital, Lahore, Pakistan, from May 2014 to June 2018. A total of 40 patients aged between 20 to 40 years with Compannacci grade I, II & III giant cell tumors (GCT) were included and patients unfit for the surgery, those with multiple, recurrent, malignant giant cell tumors, tumors involving the axial skeleton, and previously treated cases were excluded. We recorded the side, site of the tumor, post-operative distal neurovascular status, and recurrence of giant cell tumors. The patients were follow-up in the out-patient department (OPD) at the second week, fourth week, 12th week, 24th week, 48th week, 96th week, and 144th week after the surgery. Side, site of the tumor, and post-operative distal neurovascular status were assessed clinically, and recurrence of the tumors was observed clinically and radiologically.

Results: The mean age of all patients was 25.75±5.74 years. Males were 45% (18) and females were 55% (22). Most (12, 30%) tumors were present in the upper limb, and 22 (70%) were present in the lower limb. The majority (24, 60%) tumors were present around the knee joint. Companacci grade I was five (12.5%), grade II was 14 (35%), and grade III was 21 (52%). There were six (15%) pathological fractures. There was no case of distal neurovascular (DNV) injury, and three patients had a recurrence in two years of follow-up.

Conclusion: Giant cell tumor treated with scooping curettage, burr down technique, phenolization and poly-methyl methacrylate showed 7.5% recurrence. The combined use of local adjuvants in the treatment of giant cell tumors is a safe and effective way to reduce the rate of local recurrence.

Histone H3.3 G34 mutations promote aberrant PRC2 activity and drive tumor progression

A high percentage of pediatric gliomas and bone tumors reportedly harbor missense mutations at glycine 34 in genes encoding histone variant H3.3. We find that these H3.3 G34 mutations directly alter the enhancer chromatin landscape of mesenchymal stem cells by impeding methylation at lysine 36 on histone H3 (H3K36) by SETD2, but not by the NSD1/2 enzymes. The reduction of H3K36 methylation by G34 mutations promotes an aberrant gain of PRC2-mediated H3K27me2/3 and loss of H3K27ac at active enhancers containing SETD2 activity. This altered histone modification profile promotes a unique gene expression profile that supports enhanced tumor development in vivo. Our findings are mirrored in G34W-containing giant cell tumors of bone where patient-derived stromal cells exhibit gene expression profiles associated with early osteoblastic differentiation. Overall, we demonstrate that H3.3 G34 oncohistones selectively promote PRC2 activity by interfering with SETD2-mediated H3K36 methylation. We propose that PRC2-mediated silencing of enhancers involved in cell differentiation represents a potential mechanism by which H3.3 G34 mutations drive these tumors.

Denosumab in Giant Cell Tumor of Bone: Current Status and Pitfalls

Denosumab is a monoclonal antibody against RANK ligand for treatment of giant cell tumor of bone (GCTB). Clinical trials and case series have demonstrated that denosumab is relevant to beneficial tumor response and surgical down-staging in patients of GCTB. However, these trials or case series have limitations with a short follow-up. Recent increasing studies revealed that denosumab probably increased the local recurrence risk in patients treated with curettage. This may be caused by the thicken bone margin of tumor that trapped tumor cells from curettage. The direct bone formation by tumor cells in the margin after denosumab treatment also contributed to the local recurrence. in vitro studies showed denosumab resulted in a cytostatic instead of a true cytotoxic response on neoplastic stromal cells. More importantly, denosumab-treated GCTB exhibited morphologic overlap with malignancy, and a growing number of patients of malignant transformation of GCTB during denosumab treatment have been reported. The optimal duration, long term safety, maintenance dose, and optimum indications remain to be elucidated. With these concerns in mind, this review warns that the denosumab therapy of GCTB should be applied with caution.

Significance of EGFR/HER2 Expression and PIK3CA Mutations in Giant Cell Tumour of Bone Development

Giant Cell Tumour of Bone (GCTB) is a rare bone tumour. Locally aggressive and recurrent, it might evolve into pulmonary metastases. Our present work is aimed at investigating the involvement of the epidermal growth factor receptor (ErbB) family and its downstream effectors in the development and recurrence of GCTB. For this purpose, we used a cohort of 32 GCTB patients and we evaluated the clinicohistological features and the expression of RANKL, EGFR, and HER2. The mutation status of KRAS, PI3KCA, and PTEN gene as potential oncogene involved in GCTB was also evaluated. We found a significant correlation between advanced histological stages, overexpression of EGFR/HER2, and tumour recurrence. Moreover, two mutations were found in the PIK3CA gene: a missense mutation, 1634A>C, detected for the first time in GCTB patients, without influencing the stability of the protein, and a frameshift mutation, c.1658_1659delGTinsC, causing the loss of the protein kinase domain. Altogether, these results suggest that overexpression of HER2/EGFR, Campanacci, and histological stages could be used as a novel prognostic marker for GCTB recurrence.

The two faces of giant cell tumor of bone

Giant cell tumor (GCT) is a bone-destructive benign neoplasm characterized by distinctive multinucleated osteoclast-like giant cells with osteolytic properties distributed among neoplastic stromal cells. GCT is locally aggressive with progressive invasion of adjacent tissues and occasionally displays malignant characteristics including lung metastasis. GCT is characterized genetically by highly recurrent somatic mutations at the G34 position of the H3F3A gene, encoding the histone variant H3.3, in stromal cells. This leads to deregulated gene expression and increased proliferation of mutation-bearing cells. However, when GCT complicates Paget disease of bone (GCT/PDB) it behaves differently, showing a more malignant phenotype with 5-year survival less than 50%. GCT/PDB is caused by a germline mutation in the ZNF687 gene, which encodes a transcription factor involved in the repression of genes surrounding DNA double-strand breaks to promote repair by homologous recombination. Identification of these driver mutations led to novel diagnostic tools for distinguishing between these two tumors and other osteoclast-rich neoplasms. Herein, we review the clinical, histological, and molecular features of GCT in different contexts focusing also on pharmacological treatments.

Prognostic role of PD-L1 and immune-related gene expression profiles in giant cell tumors of bone

Giant cell tumor of bone (GCTB) is a locally aggressive and rarely metastatic tumor, with a relatively unpredictable clinical course. A retrospective series of 46 GCTB and a control group of 24 aneurysmal bone cysts (ABC) were selected with the aim of investigating the PD-L1 expression levels and immune-related gene expression profile, in correlation with clinicopathological features. PD-L1 and Ki67 were immunohistochemically tested in each case. Furthermore, comprehensive molecular analyses were carried out using NanoString technology and nCounter PanCancer Immune Profiling Panel, and the gene expression results were correlated with clinicopathological characteristics. PD-L1 expression was observed in 13/46 (28.3%) GCTB (and in 1/24, 4.2%, control ABC, only) and associated with a shorter disease free interval according to univariate analysis. Moreover, in PD-L1-positive lesions, three genes (CD27, CD6 and IL10) were significantly upregulated (p < 0.01), while two were downregulated (LCK and TLR8, showing borderline significance, p = 0.06). Interestingly, these genes can be related to maturation and immune tolerance of bone tissue microenvironment, suggesting a more immature/anergic phenotype of giant cell tumors. Our findings suggest that PD-L1 immunoreactivity may help to select GCTB patients with a higher risk of recurrence who could potentially benefit from immune checkpoint blockade.

[Giant cell tumor of bone : Morphology, molecular pathogenesis, and differential diagnosis]

The histological picture of giant cell tumor of bone is characterized by numerous osteoclast-like giant cells. However, these are not the actual tumor cells, but constitute a reactive infiltrate. Rather, the tumor cells are mononuclear mesenchymal cells, which even reveal an osteoblastic line of differentiation. The CD68-positive macrophages form the second group of mononuclear cells. The receptor activator of nuclear factor kappa-B/ligand (RANK/RANKL) system, which belongs to the tumor necrosis factor (TNF) cytokine family, is decisively involved in the activation of the giant cells. It is generally accepted that a RANKL expression of mononuclear stromal cells is responsible for the development and differentiation of osteoclast-like giant cells. Therefore, the RANKL inhibitor denosumab constituted an essential element for giant cell tumor therapy over the last several years, as it blocks the maturation of osteoclasts and thus the osteolytic activity and the spread of tumor. However, with time it became evident that the not risk-free therapy with denosumab may lead to extensive recurrences upon withdrawal, so this therapy is applied with caution today.At the molecular genetic level, the giant cell tumors of bone are characterized by point mutations in the H3F3A gene. The detection of this mutation is used for the diagnostic differentiation from other bone lesions containing giant cells. Giant cell osteosarcomas rarely contain H3F3A mutations. Chondroblastoma is characterized by mutations in the H3F3B gene.

A review on osteoclast diseases and osteoclastogenesis inhibitors recently developed from natural resources

Natural products have been investigated as potential candidates of novel therapeutics and play a crucial role in advanced medicinal drugs. Natural resources, including local medicinal plants (especially folk medicinal plants), animals, bacteria, and fungi have been used for more than a century, and are precious gifts from nature, providing potential medicines with high safety. Osteoclast-related diseases, such as osteoporosis, rheumatoid arthritis, Paget's disease, osteoclastoma, and periprosthetic osteolysis, are currently the most common reasons for bone inflammation, pain and fractures, resulting in low quality of life. However, the curative effects of current therapeutic drugs for these osteoclast-related diseases are limited, and long-term treatment is needed. Further, in severe cases, surgical treatments are necessary, which may cause unaffordable expenses and subsequent influences such as neuralgia, mental stress, and even development of cancer. Thus, safer inhibitors and potential drugs with enhanced curative effects and quick relief are needed to treat patients with osteoclast diseases. This review aims to introduce the main osteoclast-related diseases and some of the recently developed naturally sourced inhibitors against osteoclastogenesis, also it is desired to attract people's attention on using widely available natural resources for the evolution of new types of osteoclast inhibitors with minimal or no side-effects upon long-term treatments.

Denosumab treatment for giant-cell tumor of bone: a systematic review of the literature

BACKGROUND

Denosumab is a human monoclonal antibody (mAb) that specifically inhibits tumor-associated bone lysis through the RANKL pathway and has been used as neoadjuvant therapy for giant-cell tumor of bone (GCTB) in surgical as well as non-surgical cases. The purpose of this systematic review of the literature, therefore, is to investigate: (1) demographic characteristics of patients affected by GCTBs treated with denosumab and the clinical impact, as well as, possible complications associated with its use (2) oncological outcomes in terms of local recurrence rate (LRR) and development of lung metastasis, and (3) characteristics of its treatment effect in terms of clinical, radiological, and histological response.

METHODS

A systematic review of the literature was conducted using PubMed, EMBASE, and COCHRANE search including the following terms and Boolean operators: "Denosumab" AND "primary bone tumor", "denosumab" AND "giant cell tumor", "denosumab" AND "treatment", and finally, "denosumab" AND "giant cell tumor" AND "treatment" since 2000. After applying inclusion and exclusion criteria, a total of 19 articles were included. The quality of the included studies was assessed using STROBE for the assessment of observational studies.

RESULTS

A total of 1095 patients were included across all 19 studies. Across all the studies included, there were 615 females and 480 males. The mean patient age was 33.7 ± 8.3 years when starting the denosumab treatment. The pooled weighted local recurrence rate was 9% (95% CI 6-12%) and the pooled weighted metastases rate was 3% (95% CI 1-7%). The most common adverse event was fatigue and muscular pain. Radiologic response was estimated to occur in 66-100% of the patients. A significant reduction in pain under denosumab treatment was reported in seven studies and additional improvement in function and mobility was reported by several authors. Only two studies reported musculoskeletal tumor society (MSTS) scores which were better after denosumab treatment.

CONCLUSIONS

The use of denosumab as an adjuvant treatment of GCTB has shown a positive but variable histological response with consistent radiological changes and several types of adverse effects. There is a positive clinical response in terms of pain relief with decrease on the morbidity of surgical procedures to be performed. Finally, oncological outcomes are disparate with neither effect on metastatic disease nor local recurrence rates.

LEVEL OF EVIDENCE

IV.

Characterization of Three Novel H3F3A-mutated Giant Cell Tumor Cell Lines and Targeting of Their Wee1 Pathway

The giant cell tumor of bone (GCTB) is a locally aggressive primary bone tumor that is composed of mononuclear stroma cells, scattered macrophages, and multinucleated osteoclast-like giant cells which cause pathologic osteolysis. The stroma cells represent the neoplastic population of the tumor and are characterized by the H3F3A mutation G34W. This point mutation is regarded as the driver mutation of GCTB. We have established three new stable H3F3A mutated GCTB cell lines: U-GCT1, U-GCT2, and U-GCT3M. MK-1775 is a Wee1-kinase inhibitor which has been used for blocking of sarcoma growth. In the cell lines we detected Wee1, Cdk1, Cyclin B1, H3K36me3, and Rrm2 as members of the Wee1 pathway. We analyzed the effect of MK-1775 and gemcitabine, alone and in combination, on the growth of the cell lines. The cell lines showed a significant reduction in cell proliferation when treated with MK-1775 or gemcitabine. The combination of both agents led to a further significant reduction in cell proliferation compared to the single agents. Immunohistochemical analysis of 13 GCTB samples revealed that Wee1 and downstream-relevant members are present in GCTB tissue samples. Overall, our work offers valuable new tools for GCTB studies and presents a description of novel biomarkers and molecular targeting strategies.

Malignant Sarcomatous Transformation of Benign Giant Cell Tumor of Bone after Treatment with Denosumab Therapy: A Literature Review of Reported Cases

Giant cell tumor of bone (GCTB) is a biologically benign and locally aggressive tumor that most often affects the epiphyseal and metaphyseal sites of long bones in the young adult population. Overexpression of receptor activator of nuclear factor kappa B ligand (RANKL) by cancerous mesenchymal stromal cells stimulates a signal transduction cascade that recruits and activates multinucleated osteoclast-like giant cells, resulting in pathologic bone resorption. Denosumab, an RANKL inhibitor that blocks the RANKL-mediated osteoclast activation, has been recently approved by the United States Food and Drug Administration (FDA) for the treatment of aggressive GCTB. Although uncommon, several studies reported drug-related malignant morphological transformation of benign GCTB following treatment with denosumab therapy. The aim of the article was to review the clinicopathological characteristics of all the reported cases of malignant sarcomatous transformation of GCTB after treatment with denosumab therapy in patients without any history of prior exposure to radiotherapy.

Incidence and demographics of giant cell tumor of bone in The Netherlands: First nationwide Pathology Registry Study

Background and purpose - Giant cell tumors of bone (GCT-B) are rare, locally aggressive tumors characterized by an abundance of giant cells. Incidence studies for GCT-B are rare. This is the first study using a fully automated 100% covering pathology database, the nationwide Dutch Pathology Registry (17 million inhabitants), PALGA, to calculate incidence rates for GCT-B. Patients and methods - From PALGA, all pathology excerpts were retrieved for patients diagnosed with GCT-B, giant cell tumors of tenosynovium, and giant cell tumors of soft tissue between January 1, 2009 and December 31, 2013. The incidence of GCT-B was calculated. Results - In total, 8,156 excerpts of 5,922 patients were retrieved; these included 138 first GCT-B diagnosis. For GCT-B the incidence was 1.7 per million inhabitants per year with a male to female ratio of 1:1.38 and a median age of 35 years (9-77). Most common localization was the femur (35%), followed by the tibia (18%). No differences in localization according to age and sex were found. The incidence rate of local recurrence was 0.40 per million inhabitants per year. Interpretation - This is the first nationwide study reporting the incidence of GCT-B, based on a nationwide pathology database with 100% coverage of pathology departments. Current incidence calculations are based only on doctor-driven registries. We confirmed that GCT-B is a rare disease with an incidence that is slightly higher than previously published. The relatively young median age of patients and the high incidence of recurrence stresses the importance of developing more effective treatments for this disease.

Intratibial injection of patient-derived tumor cells from giant cell tumor of bone elicits osteolytic reaction in nude mouse

There have been various reports in the literature of an in vivo model for giant cell tumor of bone (GCTB). However, few suitable animal models of GCTB have been established, due to the fact that GCTB contains three histologically different cell types. To the best of our knowledge, injection of patient-derived GCTB cells into bone environment has not been reported until now. In the present study, the biological behavior of GCTB cells in nude mice was investigated through intratibial injection of patient-derived GCTB cells. Patient-derived GCTB cells were obtained from 5 patients who had not undergone chemo- and radiotherapy. Once isolated, the cell suspension was injected into the tibias of nude mice. The growth process was monitored by weekly observation and photographic documentation using X-ray. Four months after injection, nude mice were sacrificed and the injected tibial samples were fixed, and further analyzed using micro-computed tomography (micro-CT), standard histology, tartrate-resistant acid phosphatase (TRAP) staining and mitochondrial immunofluorescence staining. X-ray, micro-CT and standard histology revealed osteolytic destruction in the proximal end of the tibia. TRAP staining identified TRAP-positive, osteoclast-like cells distributed in the bone marrow interface of the lesion area. Anti-human mitochondrial immunofluorescence staining confirmed that the surviving cells in the osteolytic destruction were of human GCTB cell origin. These findings indicate that intratibial injection of patient-derived GCTB cells may elicit osteolytic destruction in nude mice. The results of the current study present a novel animal model for GCTB, opening new perspectives to investigate this disease and develop therapeutic agents.

Clinical outcome of primary giant cell tumor of bone after curettage with or without perioperative denosumab in Japan: from a questionnaire for JCOG 1610 study

BACKGROUND

Giant cell tumor of bone (GCTB) is an intermediate tumor known to be locally aggressive, but rarely metastasizing. To plan a prospective study of GCTB, we performed a questionnaire survey for institutions participating in the Bone and Soft Tissue Tumor Study Group (BSTTSG) in the Japan Clinical Oncology Group (JCOG) in 2015.

METHODS

We reviewed 158 consecutive patients with primary GCTB treated with curettage without perioperative denosumab from 2008 to 2010 in Japan. We investigated local and distant recurrence rates after definitive curettage. We also investigated the recurrence rate after treatment with preoperative and/or postoperative denosumab with curettage in recent years. There were 40 patients treated with perioperative denosumab, and the factors affecting recurrence in them were investigated.

RESULTS

Answers were available from 24 of 30 institutions (80.0%) participating in JCOG BSTTSG. Thirty (19.0%) and 4 (2.5%) of 158 patients developed local and distant recurrence after curettage without perioperative denosumab from 2008 to 2010, respectively. Campanacci grade and embolization before surgery were significantly associated with increasing incidence of local recurrence after curettage (p = 0.034 and p = 0.022, respectively). In patients treated with perioperative desnosumab, 120 mg denosumab was administered subcutaneously for a median 6 (2-41) and 6 (1-14) times in preoperative and postoperative settings, respectively. The recurrence rates were 6 of 21 (28.6%), 2 of 9 (22.2%), and 0 of 10 (0.0%) in the preoperative, postoperative, and both pre- and postoperative denosumab treatment groups, respectively. With all of the preoperative treatments, administration exceeding five times was significantly associated with a decreased incidence of local recurrence after curettage (p < 0.001).

CONCLUSION

The recurrence rate of GCTB was still high after curettage, especially in Campanacci grade III, and improvements in the therapeutic strategy are needed in this cohort. There is a possibility that a sufficient dose of preoperative denosumab can reduce recurrence after curettage. Recently, we have started a clinical trial, JCOG1610, to investigate the efficacy of preoperative denosumab in patients who can be treated with curettage in GCTB.

Matrix metalloproteinase-9 expression of GCTSC in peripheral tissue and central tissue of GCTB

Giant cell tumor stromal cell (GCTSC) is the tumor cell of giant cell tumor of bone (GCTB). The biomarkers characterization of GCTSC is critical for the selection of GCTB targeting drugs. We believe the main functions of GCTSC in different part of tumor should be different for different environment. Then the biological behavior and molecular biomarkers of GCTSC should be different as well. Based on this idea, we focused on GCTSC which located in central tissue, peripheral tissue and took MMP-9 as the breakthrough point to carry out research. The results showed MMP-9 staining grade of GCTSC which located in central tissue was slight, whereas multinucleated giant cell staining grade was high. The peripheral tissue was consisted by almost GCTSC with high MMP-9 staining degree and mRNA expression. This study also provided clues and inspiration for reducing GCTB recurrence rate after intralesional curettage with MMP-9 targeted therapy which were aimed at the residual peripheral tissue.

Salleh MS, Yahaya S, Syahrul Fitri ZM. The Values of Receptor Activator Nuclear Kappa-B Ligand Expression in Stage III Giant Cell Tumor of the Bone

BACKGROUND

Giant cell tumor (GCT) of bone is a benign locally aggressive primary bone tumor which is risky for local recurrences and pulmonary metastasis. Till date, there are still many uncertainties in predicting the aggressiveness of GCT. We aim to investigate whether receptor activator nuclear kappa-B ligand (RANKL) expression may determine the prognosis of the lesion.

MATERIALS AND METHODS

We examined RANKL expression in 39 patients (21 males, 18 females) by immunohistochemistry. Four patients (10%) were presented with tumor recurrence, eight patients (20%) were complicated with lung metastasis, and two patients (5%) were presented with both recurrence and lung metastasis. Positive RANKL expression was assessed according to a scoring system evaluating the percentage of the immunostained epithelial area and the staining intensity. The cumulative score was calculated to determine the final score value. Data were analyzed using PASW version 18.0 and independent t-test between nonrecurrence/recurrence groups, and nonlung metastasis/lung metastasis groups. Significance was set at P < 0.05.

RESULTS

Thirty-two patients (82%) scored 3 in RANKL-staining percentage from whole stromal cell population (>75%), 6 patients scored 2, and 1 patient scored 1. Nine patients (23%) scored 3 in RANKL-staining intensity (most intense), 19 patients (48%) scored 2, and 11 patients (29%) scored 1. Twenty six patients (67%) had strong RANKL expression (total score of 5-6), 12 patients (31%) showed moderate score (3-4) whereas only 1 patient (2%) showed weak RANKL expression. Together, the mean value of RANKL-staining percentage was 2.79, intensity 1.95 and the total score 4.77. The mean RANKL-staining percentage between recurrence and nonrecurrence groups was statistically significant (P = 0.009). There was no significant difference in the mean staining intensity and total score between nonrecurrence and recurrence groups, and staining percentage staining intensity and a total cumulative score of RANKL expression between lung metastasis and nonlung metastasis groups.

CONCLUSION

RANKL expression is generally high in Stage III GCT and is a reliable prognostic marker in predicting the risk of local recurrence however not in lung metastasis.

Locally Aggressive Connective Tissue Tumors

In this review, we highlight the complexities of the natural history, biology, and clinical management of three intermediate connective tissue tumors: desmoid tumor (DT) or aggressive fibromatosis, tenosynovial giant cell tumor (TGCT) or diffuse-type pigmented villonodular synovitis (dtPVNS), and giant cell tumor of bone (GCTB). Intermediate histologies include tumors of both soft tissue and bone origin and are locally aggressive and rarely metastatic. Some common aspects to these tumors are that they can be locally infiltrative and/or impinge on critical organs, which leads to disfigurement, pain, loss of function and mobility, neurovascular compromise, and occasionally life-threatening consequences, such as mesenteric, bowel, ureteral, and/or bladder obstruction. DT, PVNS, and GCTB have few and recurrent molecular aberrations but, paradoxically, can have variable natural histories. A multidisciplinary approach is recommended for optimal management. In DT and PVNS, a course of observation may be appropriate, and any intervention should be guided by symptoms and/or disease progression. A surgical approach should take into consideration the infiltrative nature, difficulty in obtaining wide margins, high recurrence rates, acute and chronic surgical morbidities, and impact on quality of life. There are similar concerns with radiation, which especially relate to optimal field and transformation to high-grade radiation-associated sarcomas. Systemic therapies must be considered carefully in light of acute and chronic toxicities. Although standard and novel therapies are promising, many unanswered questions, such as duration of therapy and optimal end points to evaluate efficacy of drugs in clinical practice and trials, exist. Predictive biomarkers and novel clinical trial end points, such as volumetric measurement, magnetic resonance imaging T2 weighted mapping, nuclear imaging, and patient-reported outcomes, are in development and will require validation in prospective trials.

Bispecific Antibody Binding To RANKL and Osteonectin with Enhanced Localization to the Bone

Therapeutics reducing bone turnover, such as denosumab (Dmab), an anti-RANKL antibody, can provide treatments for patients with bone destruction. However, some patients with osteoporosis or localized primary bone tumors and many patients with various types of bone-metastatic cancer display unsatisfactory responses to Dmab. For achieving greater efficiency of RANKL neutralization in the bone microenvironment by enhancing the distribution of Dmab to the bone, we reengineered Dmab by fusing with single-chain variable fragments of an antibody specific for osteonectin (On), which is abundantly expressed in osseous tissues. The bispecific antibody, Dmab-FvOn, showed a similar activity as Dmab in inhibiting RANKL as examined in an osteoclast differentiation assay. When administered to mice, Dmab-FvOn was found to localize in increased proportions at the endosteum of the bone where osteonectin is abundant. Our study suggests that by linking anti-RANKL with an osteonectin-targeting moiety, a greater proportion of the therapeutic effector can be distributed in the bone. Future studies are needed to investigate whether the bispecific antibody can achieve higher therapeutic efficacy and lower toxicity.

Giant-cell tumor of bone with pathological evidence of blood vessel invasion

Giant cell tumor of bone is a rare but aggressive benign tumor that arises at the end of long tubular bones. The tumor rarely metastasizes; however, we report a case in which a giant cell tumor of bone presented with progressive pulmonary metastases. There has been no clear pathologic evidence of the definitive cause or route of metastasis. In our case, the primary tumor site was located in the left femur with pathological evidence of blood vessel invasion. The histological and pathological features of this entity are discussed in this letter to the editor.

AG490 suppresses interleukin-34-mediated osteoclastogenesis in mice bone marrow macrophages

Interleukin-34 (IL-34) has been recently identified as a novel cytokine, substituting for the function of macrophage colony-stimulating factor (M-CSF), a pivotal osteoclastogenic factor involved in bone-related diseases (e.g., osteomyelitis of the jaws). However, the molecular mechanisms are not fully understood. This study aimed to explore the potential mechanism of IL-34 in receptor activator of NF-kB ligand (RANKL)-induced osteoclast formation. We found that IL-34 alone significantly maintained the survival of bone marrow macrophages (BMMs) and enhanced the expression of the osteoclast-related genes TRAP, Ctsk, and NFATc1, as well as TRAP-positive multinucleated cells combined with RANKL, which can be reversed by AG490. Conversely, AG490 did not affect the M-CSF-mediated osteoclastogenesis in the presence of RANKL. The protein expression of p-STAT3 in BMMs was enhanced by IL-34 combined with RANKL compared with RANKL alone, and AG490 inhibited the expression of p-SATA3 at protein level in the IL-34 plus RANKL group, resulting in significantly increased Smad7 expression. This study demonstrated for the first time that IL-34 may play a crucial role in RANKL-induced osteoclastogenesis by promoting the proliferation and differentiation of BMMs, stimulating p-STAT3 expression, and inhibiting the expression of Smad7 in the absence of M-CSF.

Immune mediators in the tumor microenvironment of prostate cancer

Prostate cancer tissue is composed of both cancer cells and host cells. The milieu of host components that compose the tumor is termed the tumor microenvironment (TME). Host cells can be those derived from the tissue in which the tumor originates (e.g., fibroblasts and endothelial cells) or those recruited, through chemotactic or other factors, to the tumor (e.g., circulating immune cells). Some immune cells are key players in the TME and represent a large proportion of non-tumor cells found within the tumor. Immune cells can have both anti-tumor and pro-tumor activity. In addition, crosstalk between prostate cancer cells and immune cells affects immune cell functions. In this review, we focus on immune cells and cytokines that contribute to tumor progression. We discuss T-regulatory and T helper 17 cells and macrophages as key modulators in prostate cancer progression. In addition, we discuss the roles of interleukin-6 and receptor activator of nuclear factor kappa-B ligand in modulating prostate cancer progression. This review highlights the concept that immune cells and cytokines offer a potentially promising target for prostate cancer therapy.

Non-Canonical (RANKL-Independent) Pathways of Osteoclast Differentiation and Their Role in Musculoskeletal Diseases

Osteoclasts are multinucleated cells derived from mononuclear phagocyte precursors (monocytes, macrophages); in the canonical pathway of osteoclastogenesis, these cells fuse and differentiate to form specialised bone-resorbing osteoclasts in the presence of receptor activator for nuclear factor kappa B ligand (RANKL). Non-canonical pathways of osteoclastogenesis have been described in which several cytokines and growth factors are able to substitute for RANKL. These humoral factors can generally be divided into those which, like RANKL, are tumour necrosis family (TNF) superfamily members and those which are not; the former include TNFα lymphotoxin exhibiting inducible expression and competing with herpes simplex virus glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes (LIGHT), a proliferation inducing ligand (APRIL) and B cell activating factor (BAFF); the latter include transforming growth factor beta (TGF-β), interleukin-6 (IL-6), IL-8, IL-11, nerve growth factor (NGF), insulin-like growth factor-I (IGF-I) and IGF-II. This review summarises the evidence for these RANKL substitutes in inducing osteoclast differentiation from tissue-derived and circulating mononuclear phagocytes. It also assesses the role these factors are likely to play in promoting the pathological bone resorption seen in many inflammatory and neoplastic lesions of bone and joint including rheumatoid arthritis, aseptic implant loosening and primary and secondary tumours of bone.

Galectin-3 in bone tumor microenvironment: a beacon for individual skeletal metastasis management

The skeleton is frequently a secondary growth site of disseminated cancers, often leading to painful and devastating clinical outcomes. Metastatic cancer distorts bone marrow homeostasis through tumor-derived factors, which shapes different bone tumor microenvironments depending on the tumor cells' origin. Here, we propose a novel insight on tumor-secreted Galectin-3 (Gal-3) that controls the induction of an inflammatory cascade, differentiation of osteoblasts, osteoclasts, and bone marrow cells, resulting in bone destruction and therapeutic failure. In the approaching era of personalized medicine, the current treatment modalities targeting bone metastatic environments are provided to the patient with limited consideration of the cancer cells' origin. Our new outlook suggests delivering individual tumor microenvironment treatments based on the expression level/activity/functionality of tumor-derived factors, rather than utilizing a commonly shared therapeutic umbrella. The notion of "Gal-3-associated bone remodeling" could be the first step toward a specific personalized therapy for each cancer type generating a different bone niche in patients afflicted with non-curable bone metastasis.

Peroxidase enzymes inhibit osteoclast differentiation and bone resorption

Myeloperoxidase (MPO) and eosinophil peroxidase (EPO) are heme-containing enzymes, well known for their antimicrobial activity, are released in abundance by innate immune infiltrates at sites of inflammation and injury. We have discovered new and previously unrecognised roles for heme peroxidases in extracellular matrix biosynthesis, angiogenesis, and bone mineralisation, all of which play an essential role in skeletal integrity. In this study we used in vitro models of osteoclastogenesis to investigate the effects of heme peroxidase enzymes on osteoclast differentiation and bone resorbing activity, pertinent to skeletal development and remodelling. Receptor activator of nuclear factor kappa B-ligand (RANKL) stimulates the formation of tartate-resistant acid phosphatase (TRAP) positive multinucleated cells and increases bone resorption when cultured with human peripheral blood mononuclear cells (PBMCs) or the RAW264.7 murine monocytic cell line. When RANKL was added in combination with either MPO or EPO, a dose-dependent inhibition of osteoclast differentiation and bone resorption was observed. Notably, peroxidases had no effect on the bone resorbing activity of mature osteoclasts, suggesting that the inhibitory effect of the peroxidases was limited to osteoclast precursor cells. Mechanistically, we observed that osteoclast precursor cells readily internalize peroxidases, and inhibited the phosphorylation of JNK, p38 MAPK and ERK1/2, important signalling molecules central to osteoclastogenesis. Our findings suggest that peroxidase enzymes, like MPO and EPO, may play a fundamental role in inhibiting RANKL-induced osteoclast differentiation at inflammatory sites of bone fracture and injury. Therefore, peroxidase enzymes could be considered as potential therapeutic agents to treat osteolytic bone disease and aberrant bone resorption.

Chemotherapy for Bone Sarcoma in Adults

The largest studies of chemotherapy for bone sarcomas are in the pediatric population. Although increasing age is often found to be an adverse prognostic factor in these clinical trials, few studies are aimed at assessing regimens specifically in the adult population. Osteosarcoma and Ewing sarcoma have peak incidences in the pediatric and young adult population but also occur in adults. Chondrosarcoma and giant cell tumor of bone are generally found in adults. In this review, we describe the current status of our knowledge about treating adults with cancers of bone origin. We also describe our experience treating patients in the adult Sarcoma Medical Oncology group at The University of Texas MD Anderson Cancer Center.

MicroRNA-106b inhibits osteoclastogenesis and osteolysis by targeting RANKL in giant cell tumor of bone

Giant cell tumor (GCT) of bone consists of three major cell types: giant cells, monocytic cells, and stromal cells. From microarray analysis, we found that miR-106b was down-regulated in GCT clinical samples and further determined by fluorescence in situ hybridization. In addition, the expression of novel potential target of miR-106b, RANKL, was elevated in GCT along with previously determined targets in other tumors such as IL-8, MMP2 and TWIST. In a RANKL 3′UTR luciferase reporter assays, agomiR-106b repressed the luciferase activity and the effect was eliminated when the targeting site in the reporter was mutated, suggesting a direct regulation of miR-106b on RANKL mRNA. Moreover, overexpression of miR-106b in GCTSCs through TALEN-mediated site-specific knockin clearly inhibited osteoclastogenesis and osteolysis. By grafting the GCT onto the chick CAM, we confirmed the inhibitory effect of miR-106b on RANKL expression and giant cell formation. Furthermore, in an OVX mouse model, silencing of miR-106b increased RANKL protein expression and promoted bone resorption, while up-regulation of miR-106b inhibited bone resorption. These results suggest that miR-106b is a novel suppressor of osteolysis by targeting RANKL and some other cytokines, which indicates that miR-106b may be a potential therapeutic target for the treatment of GCT.

Denosumab for the treatment of giant cell tumor of the bone

Giant cell tumor of bone is typically composed of neoplastic stromal cells and non-neoplastic osteoclastic giant cells. RANK-expressing osteoclastic giant cells are recruited by RANK ligand excreted by the stromal cells, and used by these neoplastic cells to create expansion space. Denosumab specifically binds to and inhibits RANK ligand, thereby eradicating osteoclastic giant cells from the tumor and thus reducing osteolytic activity. Clinical studies reported disease stabilization and clinical benefit in terms of reduced pain and analgesics use, avoided surgeries or surgeries with less morbid procedures. Adverse events observed in patients with giant cell tumor of bone were consistent with the known safety profile of denosumab with a very low incidence of hypocalcemia and osteonecrosis. Overall, denosumab was shown to suppress osteolytic activity and slow disease progression and is thus a treatment option for patients with giant cell tumor of bone.

Influence of osteoarthritis grade on molecular signature of human cartilage

Articular chondrocytes maintain cartilage matrix turnover and have the capacity for anabolic and catabolic activities that can be influenced by injury and disease. This study tested the hypothesis that catabolic genes are upregulated with regional osteoarthritis (OA) disease severity within a joint. With IRB approval, specimens of knee cartilage obtained as discarded tissues from subjects undergoing arthroplasty were partitioned for each subject by OA disease severity and evaluated for gene expression by RT-PCR. There was regional OA grade-associated upregulation of expected inflammatory mediators TNF-α, TNF receptors, IFN-γ, and interleukins as well as genes encoding proteolytic enzymes, including Adamts-5 and MMPs. Osteoclast-related genes, cathepsin K, tartrate-resistant acid phosphatase (TRAP), RANKL, RANK, M-CSF, and c-fms, but not osteoprotegerin, were induced in advanced grades. In vitro treatment of normal human chondrocytes with interleukin-1β upregulated similar genes; this provides evidence that chondrocytes per se can be the source of osteoclast-related factors. Immunohistochemical staining showed that RANK- and RANKL-positive cells were abundant in advanced grades, especially in chondrocyte clusters. This suggests a possible autocrine mechanism by which an osteoclast phenotype is induced in articular chondrocytes. In sum, these studies identified gene expression signatures in human OA cartilage based upon regional disease severity within a joint. There was an effect of OA Grade on expression of osteoclastic lytic enzymes and regulatory factors in human articular chondrocytes. Induction of an osteoclast-like phenotype in chondrocytes may be part of OA progression and suggests specific therapeutic approaches.

Rank ligand as a target in musculoskeletal neoplasms

Receptor activator of nuclear factor-κB ligand (RANKL) is a tumor necrosis factor (TNF) family member, which signals through the osteoclast surface RANK. As such, RANKL is required for osteoclast differentiation and function, namely bone resorption. There is now growing evidence that RANKL is a therapeutic target for musculoskeletal neoplasms, namely giant cell tumor of bone (GCTB) and osteosarcoma.

5-Fluoruracil blocked giant cell tumor progression by suppressing osteoclastogenesis through NF-kappaB signals and blocking angiogenesis

Giant cell tumor of bone (GCTB) is a bone destroying tumor comprised of spindle-like stromal cells and monocytes of myeloid lineage that are differentiated into osteoclast-like multinucleated giant cells. Nuclear factor-Kappa B (NF-κB) has been identified to be essential for GCT progression. Herein, we found that 5-Fluorouracil (5-FU), a widely used chemotherapeutics, is a promising anticancer agent for GCT both targeting spindle-like stromal cells and osteoclast giant cells through NF-κB pathway. In this study, in vitro 5-FU not only directly blocked both stromal cell- and RANKL-induced osteoclastogenesis through NF-κB pathway, but also indirectly inhibited osteoclast formation and angiogenesis by suppressing the expression of osteoclast-activating factors including IL-1β, MCP-1 and tumor angiogenesis factor VEGF in stromal cells. In vivo, we found that 5-FU blocked GCT progression through NF-κB pathway by utilizing our chick embryo chorioallantoic membrane (CAM) model. Taken together, our results suggest that 5-FU can inhibit GCT development by suppressing osteoclast formation through NF-κB pathway and blocking angiogenesis, and may serve as a novel agent in the treatment of GCT.