Gene expression in giant-cell tumors

Outcome of Reoperation for Local Recurrence Following En Bloc Resection for Bone Giant Cell Tumor of the Extremity

En bloc resection is typically performed to treat giant cell tumors of bone (GCTB), particularly when curettage can be challenging owing to extensive bone cortex destruction with soft tissue extension. Few reports have addressed the clinical outcomes after reoperation for local recurrence in patients with GCTB who underwent en bloc resection. In this multicenter retrospective study, we investigated local recurrence, distant metastasis, malignant transformation, mortality, and limb function in patients treated for local recurrence following en bloc resection for GCTB. Among 205 patients who underwent en bloc resection for GCTB of the extremities between 1980 and 2021, we included 29 with local recurrence. En bloc resection was performed for large tumors with soft tissue extension, pathological fractures with joint invasion, complex fractures, and dispensable bones, such as the proximal fibula and distal ulna. Local re-recurrence, distant metastasis, malignant transformation, and mortality rates were 41.4% (12/29), 34.5% (10/29), 6.9% (2/29), and 6.9% (2/29), respectively. The median Musculoskeletal Tumor Society score was 26 (interquartile range, 23–28). The median follow-up period after surgery for local recurrence was 70.1 months (interquartile range, 40.5–123.8 months). Local recurrence following en bloc resection for GCTB could indicate an aggressive GCTB, necessitating careful follow-up.

Denosumab Does Not Decrease Local Recurrence in Giant Cell Tumor of Bone Treated With En Bloc Resection

We performed a systematic analysis of existing studies to determine whether preoperative denosumab reduces the risk of local recurrence for patients with giant cell tumor of bone treated with en bloc resection and to address the optimal duration of preoperative denosumab with respect to the risk of local recurrence after en bloc resection. Denosumab did not decrease the risk of local recurrence after en bloc resection; the proportion of patients with local recurrence was 3.6% (2 of 56) in the en bloc resection with preoperative denosumab group vs 14.2% (40 of 280) in the en bloc resection alone group, with an overall pooled odds ratio of 0.76 (P=.67). Meta-regression models revealed no association between the duration of preoperative denosumab and the odds of local recurrence after en bloc resection (P=.83). Administration of denosumab for 3 months before en bloc resection is appropriate for sufficient bone hardening to reduce tumor cell spillage and does not result in denosumab-related complications. [Orthopedics. 2021;44(6):326-332.].

Denosumab Treatment for Giant Cell Tumor of the Spine Including the Sacrum

STUDY DESIGN

This was a subanalysis of an international, multicenter, open-label study.

OBJECTIVE

The aim of this study was to assess the efficacy and safety of denosumab in a subset of patients with giant cell tumors of bone (GCTB) of the spine including the sacrum from an international, open-label, single-arm, phase 2 study (ClinicalTrials.gov: NCT00680992).

SUMMARY OF BACKGROUND DATA

Standard GCTB treatment is surgical removal, either by curettage or resection, combined with intraoperative adjuvant therapy; however, some sites may not be amenable to resection (e.g., skull, spine).

METHODS

Adults or skeletally mature adolescents with pathologically confirmed GCTB of the spine including the sacrum, and radiologically measurable evidence of active disease, were included. Patients received denosumab (120 mg subcutaneously) once every 4 weeks during the treatment phase, with loading doses on days 8 and 15 of the first cycle. Patients had surgically unsalvageable GCTB (Cohort 1), had planned surgery expected to result in severe morbidity (Cohort 2), or were enrolled from a previous GCTB study (Cohort 3).

RESULTS

Overall, 132 patients were included in the safety analysis (103 in Cohort 1, 24 in Cohort 2, and five in Cohort 3); 131 patients were included in the efficacy analysis. Kaplan-Meier estimated probabilities of disease progression or recurrence were 3% (95% confidence interval [CI], 0.0-6.2) at year 1 and 7.4% (95% CI, 2.1-12.7) at years 3 and 5 in Cohort 1, and not estimable in Cohorts 2 and 3. Of 23 patients (Cohort 2) with surgery planned at baseline, 10 (43%) had on-study surgery; of these, one patient had reported disease progression or recurrence after the on-study surgery. Clinical benefit was reported in 83% of patients overall (all cohorts).

CONCLUSION

Results from the analysis suggest that denosumab is potentially effective treatment for patients with GCTB of the spine including the sacrum. The adverse event profile was consistent with the full study population.Level of Evidence: 2.

Is Treatment with Denosumab Associated with Local Recurrence in Patients with Giant Cell Tumor of Bone Treated with Curettage? A Systematic Review

BACKGROUND

Denosumab, a monoclonal antibody that binds to receptor activation of nuclear factor-kappa ß ligand (RANKL), has been used as a drug to treat aggressive giant cell tumors of bone. It is unclear whether preoperative denosumab therapy is associated with the local recurrence risk in patients with giant cell tumors of bone treated with curettage. Early evidence suggests that denosumab treatment is associated with a reduction in local recurrence, but other studies have questioned that premise. Curettage after a short course of denosumab (3 to 4 months) has been recommended, especially for large, aggressive giant cell tumors in which complete curettage is difficult to achieve. No randomized studies have documented the benefit of this approach, and some investigators have reported higher local recurrence after denosumab treatment. Due to this confusion, we performed a systematic analysis of existing reports to attempt to answer this question and determine whether the appropriate preoperative denosumab therapy duration could be established.

QUESTIONS/PURPOSES

(1) Is the use of preoperative denosumab associated with local recurrence risk in patients with giant cell tumors of bone treated with curettage compared with those treated with curettage alone? (2) Is the preoperative denosumab therapy duration associated with local recurrence after curettage?

METHODS

We searched the PubMed, EMBASE, and CENTRAL databases on April 26, 2019 and included both randomized and non-randomized studies that compared local recurrence between patients who had giant cell tumors of bone and were treated with curettage after preoperative denosumab and patients treated with curettage alone. Two authors independently screened the studies. There were no randomized studies dealing with denosumab in giant cell tumors of bone, and generally, denosumab was used for more aggressive tumors. We assessed the quality of the included studies using the Risk of Bias Assessment tool for Non-randomized Studies, with a moderate overall risk of bias. We registered our protocol in PROSPERO (registration number CRD42019133288). We selected seven eligible studies involving 619 patients for the final analysis.

RESULTS

The proportion of patients with local recurrence ranged from 20% to 100% in the curettage with preoperative denosumab group and ranged from 0% to 50% in the curettage-alone group. The odds ratio of local recurrence ranged from 1.07 to 37.80 in no more than 6 months of preoperative denosumab duration group and ranged from 0.60 to 28.33 in more than 6 months of preoperative denosumab duration group.

CONCLUSIONS

The available evidence for the benefit of denosumab in more aggressive giant cell tumors is inconclusive, and denosumab treatment may even be associated with an increase in the proportion of patients experiencing local recurrence. Because there are no randomized studies and the existing studies are of poor quality due to indication bias (the most aggressive Campanacci 3 lesions or those where even a resection would be difficult and result in morbidity are generally the patients who are treated with denosumab), the evidence to suggest a disadvantage is weak. Denosumab treatment should be viewed with caution until more definitive, randomized studies documenting a benefit (or not) have been conducted. Furthermore, we could not find evidence to suggest an appropriate length of preoperative denosumab before curettage.

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.

Effect of chemotherapy on cancer stem cells and tumor-associated macrophages in a prospective study of preoperative chemotherapy in soft tissue sarcoma

Background

Cancer stem cells (CSC) may respond to chemotherapy differently from other tumor cells.

Methods

This study examined the expression of the putative cancer stem cell markers ALDH1, CD44, and CD133; the angiogenesis marker CD31; and the macrophage marker CD68 in soft tissue sarcomas (STS) before and after 4 cycles of chemotherapy with doxorubicin and ifosfamide in 31 patients with high-grade soft tissue sarcoma in a prospective clinical trial.

Results

None of the markers clearly identified CSCs in STS samples. Macrophages represented a prominent component in viable tumor areas in pre-treatment STS biopsies, ranging from < 5 to > 50%. Furthermore, macrophages expressed CD44 and ALDH1. Macrophage density correlated with baseline maximum standardized uptake value (SUVmax) on fluoro-deoxyglucose positron emission tomography (PET) imaging. Pre-chemotherapy CD68 staining correlated positively with the baseline SUVmax, and negatively with the percent of viable tumor cells in post-chemotherapy resection samples. In particular, cases with more CD68-positive cells at biopsy had fewer viable tumor cells at resection, suggesting a better response to chemotherapy.

Conclusions

In conclusion, ALDH1, CD44, and CD133 are not likely to be useful markers of CSCs in STS. However, our observation of infiltrating macrophages in STS specimens indicates that these immune cells may contribute significantly to STS biology and response to chemotherapy, and could provide a potential target of therapy. Future studies should investigate macrophage contribution to STS pathophysiology by cytokine signaling.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1883-6) contains supplementary material, which is available to authorized users.

Role of intravenous zoledronic acid in management of giant cell tumor of bone- A prospective, randomized, clinical, radiological and electron microscopic analysis

BACKGROUND

The primary treatment of Giant cell tumor of bone is surgical management. Bisphosphonates are antiresorptive drugs which inhibit osteoclast mediated bone resorption and shown to have inhibitory effect on various tumors. The present study aims to establish clinical, ultrastructural and radiological response of intravenous zoledronic acid on giant cell tumor of bone.

METHODOLOGY

Design - Prospective randomized controlled study. A group of 30 patients of GCT bone were randomized into two equal groups. Patients in control group did not receive any adjuvant therapy before surgery. Patients in bisphosphonate group received three doses of intravenous zoledronic acid at four weeks interval prior to definitive surgery. The evaluation was done based on size of swelling, VAS score, plain radiograph, MRI and histopathological and Transmission electron microscopic examination findings.

RESULTS

Significant reduction in VAS score (from mean 5.33 to 1.8), increased mineralization particularly at periphery of lesion in plain radiograph, statistically significant increase in mean apoptotic index, P value < 0.0001 (mean 41.46 in bisphosphonate group and 6.06 in control group) was noted in bisphosphonate group. No significant change in tumor volume is noted in MRI. No significant side effects were noted.

DISCUSSION

One distinctive feature of pathogenesis of GCT bone is osteoclastogenesis which causes extensive bone destruction. Use of intravenous Zoledronic acid counteracts this bone destruction. Further, possible antiangiogenic effect of intravenous bisphosphonates inhibits tumor growth and provides symptomatic improvement.

CONCLUSION

IV Zoledronic acid alleviates pain, produce sclerosis and induce apoptosis hence decrease the rate of tumor progression and decrease the rate of local bone destruction, hence they are useful adjuvant to surgery in GCT.

Denosumab in patients with aneurysmal bone cysts: A case series with preliminary results

Purpose:

Aneurysmal bone cyst (ABC) is a rare skeletal tumor usually treated with surgery/embolization. We hypothesized that owing to similarities with giant cell tumor of bone (GCTB), denosumab was active also in ABC.

Methods:

In this observational study, a retrospective analysis of ABC patients treated with denosumab was performed. Patients underwent radiologic disease assessment every 3 months. Symptoms and adverse events were noted.

Results:

Nine patients were identified (6 male, 3 female), with a median age of 17 years (range 14–42 years). Primary sites were 6 spine–pelvis, 1 ulna, 1 tibia, and 1 humerus. Patients were followed for a median time of 23 months (range 3–55 months). Patients received a median of 8 denosumab administrations (range 3–61). All symptomatic patients had pain relief and 1 had paresthesia improvement. Signs of denosumab activity were observed after 3 to 6 months of administration: bone formation by computed tomography scan was demonstrated in all patients and magnetic resonance imaging gadolinium contrast media decrease was observed in 7/9 patients. Adverse events were negligible. At last follow-up, all patients were progression-free: 5 still on denosumab treatment, 2 off denosumab were disease-free 11 and 17 months after surgery, and the last 2 patients reported no progression 12 and 24 months after denosumab interruption and no surgery.

Conclusions:

Denosumab has substantial activity in ABCs, with favorable toxicity profile. We strongly support the use of surgery and/or embolization for the treatment of ABC, but denosumab could have a role as a therapeutic option in patients with uncontrollable, locally destructive, or recurrent disease.

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.

Clinical and pathological results of denosumab treatment for giant cell tumors of bone: Prospective study of 14 cases

Objective

Giant cell tumor of bone (GCT) is a primary, osteolytic, benign tumor of the bone. Surgery is the commonly used treatment; however, recurrence remains a problem. Receptor activator of nuclear factor kappa B (RANKL) is responsible for the formation of osteoclastic cells. Discovery of RANKL and its human monoclonal antibody, denosumab, led to use of denosumab for treatment of GCT. The aim of this study was to evaluate clinical and pathological results of treatment of GCT with denosumab and to assess adverse effect profile and recurrence rate.

Methods

Thirteen patients with 14 lesions were enrolled in the study. Mean age was 38.3 years. Patients were given subcutaneous injections of denosumab (120 mg) every 4 weeks (with additional doses on days 0, 8 and 15 in cycle 1 only) and were radiologically evaluated for tumor response. Pain and functional status were measured using Visual Analog Score (VAS) and Musculoskeletal Tumor Society Score (MSTS). Adverse effects were analyzed after each cycle.

Results

Participants were 5 men and 8 women. Mean follow-up was 17 months. One lesion was Campanacci grade I, 8 were grade II, and 5 were grade III. Eight lesions were recurrent, and remaining were primary lesions. After average of 9 cycles (range: 4–17 cycles), all tumors underwent radiological regression. Ten lesions were removed surgically. More than 90% of giant cells were found to have regressed in all pathological specimens. On last follow-up, average VAS was 1 and MSTS was 87%. Fatigue and joint and muscle pain after injections was reported by 46% of patients, and mild hypocalcaemia was seen in 1 patient.

Conclusion

Denosumab has been shown to be a successful drug in treatment of GCT. Denosumab can be used as neoadjuvant for all recurrent lesions, grade II lesions with high surgical risk, grade III lesions, and metastatic cases of GCT.

Level of evidence

Level IV, Therapeutic study

Genome-wide DNA methylation analysis identifies MEGF10 as a novel epigenetically repressed candidate tumor suppressor gene in neuroblastoma

Neuroblastoma is a childhood cancer in which many children still have poor outcomes, emphasising the need to better understand its pathogenesis. Despite recent genome‐wide mutation analyses, many primary neuroblastomas do not contain recognizable driver mutations, implicating alternate molecular pathologies such as epigenetic alterations. To discover genes that become epigenetically deregulated during neuroblastoma tumorigenesis, we took the novel approach of comparing neuroblastomas to neural crest precursor cells, using genome‐wide DNA methylation analysis. We identified 93 genes that were significantly differentially methylated of which 26 (28%) were hypermethylated and 67 (72%) were hypomethylated. Concentrating on hypermethylated genes to identify candidate tumor suppressor loci, we found the cell engulfment and adhesion factor gene MEGF10 to be epigenetically repressed by DNA hypermethylation or by H3K27/K9 methylation in neuroblastoma cell lines. MEGF10 showed significantly down‐regulated expression in neuroblastoma tumor samples; furthermore patients with the lowest‐expressing tumors had reduced relapse‐free survival. Our functional studies showed that knock‐down of MEGF10 expression in neuroblastoma cell lines promoted cell growth, consistent with MEGF10 acting as a clinically relevant, epigenetically deregulated neuroblastoma tumor suppressor gene. © 2016 The Authors. Molecular Carcinogenesis Published by Wiley Periodicals, Inc.

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.

Critical hypercalcemia following discontinuation of denosumab therapy for metastatic giant cell tumor of bone

We report a 14 year-old female with Giant Cell Tumor of Bone, successfully treated with denosumab, who developed critical hypercalcemia after completion of therapy. Five months after her last denosumab treatment, serum calcium rose to 16.5 mg/dL (normal 8.7-10.8 mg/dL), nearly double her prior level of 8.4 mg/dL while receiving denosumab. She required emergent intervention to treat her hypercalcemia, which was attributed to rebound osteoclast activity and osteopetrotic bone. Denosumab is widely used in adults and increasingly in pediatric oncology populations and our experience demonstrates the need for close monitoring for electrolyte derangements following discontinuation.

Giant cell tumor of bone: current treatment options

OPINION STATEMENT

Giant cell tumor of bone (GCTB) comprises up to 20 % of benign bone tumors in the US. GCTB are typically locally aggressive, but metastasize to the lung in ~5 % of cases. Malignant transformation occurs in a small percentage of cases, usually following radiation therapy. Historically, GCTB have been treated primarily with surgery. When the morbidity of surgery would be excessive, radiation therapy may achieve local control. In most cases the primary driver of the malignant cell appears to be a mutation in H3F3A leading to a substitution of Gly34 to either Trp or Leu in Histone H3.3. This change presumably alters the methylation of the protein, and thus, its effect on gene expression. The malignant stromal cells of GCTB secrete RANKL, which recruits osteoclast precursors to the tumor and stimulates their differentiation to osteoclasts. The elucidation of the biology of GCTB led to trials of the anti-RANKL monoclonal antibody denosumab in this disease, with a clear demonstration of beneficial clinical effect. Surgery remains the primary treatment of localized GCTB. When surgery is not possible or would be associated with excessive morbidity, denosumab is a good treatment option. The optimal length of treatment and schedule of denosumab is unknown, but recurrences after apparent complete responses have been observed after stopping denosumab, and long-term follow-up of denosumab treatment may reveal unrecognized effects. The role of denosumab in the preoperative or adjuvant setting will require clinical trials. In some cases local radiation therapy may be useful, although long term effects should be considered.

Overexpression of hypoxia-inducible factor-1α and vascular endothelial growth factor in sacral giant cell tumors and the correlation with tumor microvessel density

Although classified as benign, giant cell tumors of the bone (GCTB) may be aggressive, recur and even metastasize to the lungs. In addition, the pathogenesis and histogenesis remain unclear; thus, the driving factors behind the strong tumor growth capacity of GCTB require investigation. In the present study, the expression levels of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF), which are promoted by hypoxic conditions, were determined in 22 sacral GCTB samples using immunohistochemistry and western blot analysis. Furthermore, CD34 expression was analyzed using these methods. The correlation between HIF-1α or VEGF expression and the tumor microvessel density (MVD) was then determined. The results demonstrated that HIF-1α, VEGF and CD34 were overexpressed in the 22 sacral GCTB specimens, and overexpression of HIF-1α and VEGF correlated with the tumor MVD. Thus, the present study has provided novel indicators for the tumor growth capacity of GCTBs.

Effects of denosumab on pain and analgesic use in giant cell tumor of bone: interim results from a phase II study

BACKGROUND

Giant cell tumor of bone (GCTB) is an aggressive primary osteolytic tumor. GCTB often involves the epiphysis, usually causing substantial pain and functional disability. Denosumab, a fully human monoclonal antibody against receptor activator of nuclear factor κΒ ligand (RANKL), is an effective treatment option for patients with advanced GCTB. This analysis of data from an ongoing, open-label study describes denosumab's effects on pain and analgesic use in patients with GCTB.

MATERIAL AND METHODS

Patients with unresectable disease (e.g. sacral or spinal GCTB, or multiple lesions including pulmonary metastases) were enrolled into Cohort 1 (N = 170), and patients with resectable disease whose planned surgery was associated with severe morbidity (e.g. joint resection, limb amputation, or hemipelvectomy) were enrolled into Cohort 2 (N = 101). Patients received denosumab (120 mg) subcutaneously every four weeks, with additional doses on study days 8 and 15. Patients assessed worst pain severity with the Brief Pain Inventory - Short Form (BPI-SF) at baseline, at each visit for the first six months, and every three months thereafter.

RESULTS

Clinically relevant pain improvement was reported by 29% of patients in Cohort 1 and 35% in Cohort 2 during week 1 and by ≥ 50% of patients in each cohort at each study visit from months 2-30. Median time to clinically relevant improvement was 30 (95% CI 16, 57) days in Cohort 1 and 15 (95% CI 15, 29) days in Cohort 2. Results in patients with moderate/severe pain at baseline were similar. Fewer than 30% of patients in Cohort 1 and 10% in Cohort 2 experienced clinically relevant pain worsening at any visit through 27 months. Most patients had no/low analgesic use during the study.

CONCLUSION

Most patients treated with denosumab experienced clinically relevant decreases in pain within two months.

Targeting receptor-activator of nuclear kappaB ligand in aneurysmal bone cysts: verification of target and therapeutic response

Aneurysmal bone cyst (ABC) is a benign tumor of bone presenting as a cystic, expansile lesion in both the axial and appendicular skeleton. Axial lesions demand special consideration, because treatment-related morbidity can be devastating. In similar lesions, such as giant cell tumor of bone (GCTB), the receptor-activator of nuclear kappaB ligand (RANKL)-receptor-activator of nuclear kappaB (RANK) signaling axis is essential to tumor progression. Although ABC and GCTB are distinct entities, they both contain abundant multinucleated giant cells and are osteolytic characteristically. We hypothesize that ABCs express both RANKL and RANK similarly in a cell-type specific manner, and that targeted RANKL therapy will mitigate ABC tumor progression. Cellular expression of RANKL and RANK was determined in freshly harvested ABC samples using laser confocal microscopy. A consistent cell-type-specific pattern was observed: fibroblastlike stromal cells expressed RANKL strongly whereas monocyte/macrophage precursor and multinucleated giant cells expressed RANK. Relative RANKL expression was determined by quantitative real-time polymerase chain reaction in ABC and GCTB tissue samples; no difference in relative expression was observed (P > 0.05). In addition, we review the case of a 5-year-old boy with a large, aggressive sacral ABC. After 3 months of targeted RANKL inhibition with denosumab, magnetic resonance imaging demonstrated tumor shrinkage, bone reconstitution, and healing of a pathologic fracture. Ambulation, and bowel and bladder function were restored at 6 months. Denosumab treatment was well tolerated. Post hoc analysis demonstrated strong RANKL expression in the pretreatment tumor sample. These findings demonstrate that RANKL-RANK signal activation is essential to ABC tumor progression. RANKL-targeted therapy may be an effective alternative to surgery in select ABC presentations.

Identification of differentially expressed genes and their subpathways in recurrent versus primary bone giant cell tumors

Giant cell tumor (GCT) of the bone is a benign but locally aggressive bone neoplasm with a strong tendency to develop local recurrent and metastatic disease. Thus, it provides a useful model system for the identification of biological mechanisms involved in bone tumor progression and metastasis. This study profiled 24 cases of recurrent versus primary bone GCT tissues using QuantiGene 2.0 Multiplex Arrays that included Human p53 80-Plex Panels and Human Stem Cell 80-Plex Panels. A total of 32 differentially expressed genes were identified, including the 20 most upregulated genes and the 12 most downregulated genes in recurrent GCT. The genes identified are related to cell growth, adhesion, apoptosis, signal transduction and bone formation. Furthermore, iSubpathwayMiner analyses were performed to identify significant biological pathway regions (subpathway) associated with this disease. The pathway analysis identified 11 statistically significant enriched subpathways, including pathways in cancer, p53 signaling pathway, osteoclast differentiation pathway and Wnt signaling pathway. Among these subpathways, four genes (IGF1, MDM2, STAT1 and RAC1) were presumed to play an important role in bone GCT recurrence. The differentially expressed MDM2 protein was immunohistochemically confirmed in the recurrent versus primary bone GCT tissues. This study identified differentially expressed genes and their subpathways in recurrent GCT, which may serve as potential biomarkers for the prediction of GCT recurrence.

Radiological and pathological characteristics of giant cell tumor of bone treated with denosumab

Abstract

We describe a case of giant cell tumor of the proximal tibia with skip bone metastases of the ipsilateral femur in a 20-year-old man. After the neoadjuvant treatment with denosumab, plain radiographs and computed tomography showed marked osteosclerosis and sclerotic rim formation, and ¹⁸F-FDG PET/CT showed a decreased standardized uptake value, whereas magnetic resonance imaging showed diffuse enhancement of the tumor, nearly the same findings as those at pretreatment. Pathological findings of the surgical specimen after the denosumab treatment showed benign fibrous histiocytoma-like features with complete disappearance of both mononuclear stromal cells and multinuclear osteoclast-like giant cells.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1090602085125068

Genetics of rare mesenchymal tumors: implications for targeted treatment in DFSP, ASPS, CCS, GCTB and PEComa

Soft tissue and bone sarcomas comprise a heterogeneous group of mesenchymal tumors that include roughly 130 distinct diagnostic entities. Many of them are exceptionally rare, with only few cases diagnosed worldwide each year. Development of novel targeted treatment in this group of tumors is of special importance since many sarcoma subtypes are resistant to conventional chemotherapy and the effective therapeutic options are limited. In this review we aim to discuss the molecular implications for targeted therapy in selected rare soft tissue and bone sarcoma subtypes, including dermatofibrosarcoma protuberans (DFSP), alveolar soft part sarcoma (ASPS), clear cell sarcoma (CCS), giant cell tumor of bone (GCTB) and perivascular epithelioid cell neoplasms (PEComas). This article is part of a Directed Issue entitled: Rare cancers.

Benign bone tumors

Benign bone lesions are a broad category that demonstrates a spectrum of activities from latent to aggressive. Differentiating the various tumors is important in order to properly determine necessary intervention. This chapter focuses on the presentation, imaging, diagnostic features, and treatment of the most common benign bone tumors in order to help guide diagnosis and management.

Safety and efficacy of denosumab for adults and skeletally mature adolescents with giant cell tumour of bone: interim analysis of an open-label, parallel-group, phase 2 study

BACKGROUND

Giant cell tumour of bone (GCTB) is a very rare, aggressive, and progressive osteolytic tumour for which no standard medicinal treatment or chemotherapy exists. We report interim safety and efficacy results from a phase 2 study of denosumab in patients with GCTB.

METHODS

We did an international, open-label, parallel-group, phase 2 trial of patients with histologically confirmed GCTB and radiographically measurable active disease. Eligible patients were adults or skeletally mature adolescents with radiographic evidence of at least one mature long bone who were at least 12 years old and weighed at least 45 kg. We divided patients into three cohorts--those with surgically unsalvageable GCTB (cohort 1), those with salvageable GCTB whose surgery was associated with severe morbidity (cohort 2), and those who transferred from a previous study of denosumab for GCTB (cohort 3). Patients in cohorts 1 and 2 received 120 mg of subcutaneous denosumab every 4 weeks with loading doses on days 8 and 15 of the first cycle; those in cohort 3 continued the regimen from the previous study. Investigator-determined disease status and clinical benefit were assessed every 4 weeks. Our primary endpoint was the safety profile of denosumab in terms of adverse events and laboratory abnormalities. Prespecified secondary endpoints were time to disease progression in cohort 1 and the proportion of patients without any surgery at 6 months in cohort 2. Safety analyses included all patients who received at least one dose of denosumab. Efficacy analyses included all eligible patients who received at least one dose of denosumab. This study is registered with ClinicalTrials.gov, identifier NCT00680992.

FINDINGS

282 patients, including ten adolescents, were included between Sept 9, 2008, and March 25, 2011. Of the 281 patients analysable for safety, three (1%) had osteonecrosis of the jaw and 15 (5%) hypocalcaemia. The most common grade 3-4 adverse events were hypophosphataemia, which occurred in nine (3%) patients, and anaemia, back pain, and pain in extremities, each of which occurred in three patients (1%). Serious adverse events were reported in 25 (9%) patients. No treatment-related deaths were reported. On the basis of investigators' assessment of disease status, 163 of 169 (96%) analysable patients in cohort 1 had no disease progression after median follow-up of 13 months (IQR 5·8-21·0). In cohort 2, 74 of 100 (74%) analysable patients had no surgery and 16 of 26 (62%) patients who had surgery underwent a less morbid procedure than planned. Median follow-up in cohort 2 was 9·2 months (IQR 4·2-12·9).

INTERPRETATION

Adverse events were consistent with the known safety profile of denosumab. Denosumab was associated with tumour responses and reduced the need for morbid surgery in patients with GCTB. Denosumab represents a new treatment option for patients with GCTB.

FUNDING

Amgen.

Giant cell tumor of bone: a basic science perspective

Comprehending the pathogenesis of giant cell tumor of bone (GCT) is of critical importance for developing novel targeted treatments for this locally-aggressive primary bone tumor. GCT is characterized by the presence of large multinucleated osteoclast-like giant cells distributed amongst mononuclear spindle-like stromal cells and other monocytes. The giant cells are principally responsible for the extensive bone resorption by the tumor. However, the spindle-like stromal cells chiefly direct the pathology of the tumor by recruiting monocytes and promoting their fusion into giant cells. The stromal cells also enhance the resorptive ability of the giant cells. This review encompasses many of the attributes of GCT, including the process of giant cell formation and the mechanisms of bone resorption. The significance of the receptor activator of nuclear factor-κB ligand (RANKL) in the development of GCT and the importance of proteases, including numerous matrix metalloproteinases, are highlighted. The mesenchymal lineage of the stromal cells and the origin of the hematopoietic monocytes are also discussed. Several aspects of GCT that require further understanding, including the etiology of the tumor, the mechanisms of metastases, and the development of an appropriate animal model, are also considered. By exploring the current status of GCT research, this review accentuates the significant progress made in understanding the biology of the tumor, and discusses important areas for future investigation.

RANKL, denosumab, and giant cell tumor of bone

PURPOSE OF REVIEW

Giant cell tumor (GCT) of bone is a benign, osteolytic neoplasm of bone. The receptor activator of NF-KB ligand (RANKL) pathway has recently been shown to play a key role in the pathogenesis of GCT.

RECENT FINDINGS

Treatment for refractory, recurrent, or metastatic GCT remains challenging. The recent development of a monoclonal antibody to RANKL, denosumab, offers promise in the management of these patients. A recent phase 2 study suggested denosumab offers disease and symptom control for patients with advanced or refractory disease. In this population, denosumab appears to be well tolerated. There are key questions which remain to be addressed, including patient selection, optimal scheduling, use as an adjuvant, and application to other giant cell-rich disorders.

SUMMARY

Denosumab offers a new treatment option for a subset of patients with previously untreatable GCT. The role of denosumab in curative treatment is the subject of ongoing studies.

Denosumab induces tumor reduction and bone formation in patients with giant-cell tumor of bone

PURPOSE

Giant-cell tumor of bone (GCTB) is a locally aggressive, benign osteolytic tumor in which bone destruction is mediated by RANK ligand (RANKL). The RANKL inhibitor denosumab is being investigated for treatment of GCTB. We describe histologic analyses of GCTB tumor samples from a phase II study of denosumab in GCTB.

EXPERIMENTAL DESIGN

Adult patients with recurrent or unresectable GCTB received subcutaneous denosumab 120 mg every 4 weeks (with additional doses on days 8 and 15). The primary histologic efficacy endpoint was the proportion of patients who had a 90% or more elimination of giant cells from their tumor. Baseline and on-study specimens were also evaluated for overall tumor morphology and expression of RANK and RANKL.

RESULTS

Baseline tumor samples were typically composed of densely cellular proliferative RANKL-positive tumor stromal cells, RANK-positive rounded mononuclear cells, abundant RANK-positive tumor giant cells, and areas of scant de novo osteoid matrix and woven bone. In on-study samples from 20 of 20 patients (100%), a decrease of 90% or more in tumor giant cells and a reduction in tumor stromal cells were observed. In these analyses, thirteen patients (65%) had an increased proportion of dense fibro-osseous tissue and/or new woven bone, replacing areas of proliferative RANKL-positive stromal cells.

CONCLUSIONS

Denosumab treatment of patients with GCTB significantly reduced or eliminated RANK-positive tumor giant cells. Denosumab also reduced the relative content of proliferative, densely cellular tumor stromal cells, replacing them with nonproliferative, differentiated, densely woven new bone. Denosumab continues to be studied as a potential treatment for GCTB.

PTHrP increases RANKL expression by stromal cells from giant cell tumor of bone

Giant cell tumor of bone (GCT) presents with numerous osteoclast-like multinucleated giant cells that are principally responsible for the extensive bone resorption by the tumor. Although the precise etiology of GCT remains uncertain, the accumulation of giant cells is partially due to the high expression of the receptor activator of nuclear factor-κB ligand (RANKL) from the neoplastic stromal cells. Here, we have investigated whether parathyroid hormone-related protein (PTHrP) plays a role in the pathogenesis of GCT. Immunohistochemistry results revealed PTHrP expression in the stromal cells of the tumor, and that its receptor, the parathyroid hormone type 1 receptor (PTH1R), is expressed by both the stromal cells and giant cells. PCR and Western blot analyses confirmed the expression of PTHrP and PTH1R by isolated stromal cells from five patients presenting with GCT. Treatment of GCT stromal cells with varying concentrations of PTHrP (1-34) significantly increased both RANKL gene expression and the number of multinucleated cells formed from RAW 264.7 cells in co-culture experiments, whereas inhibition of PTHrP with a neutralizing antibody decreased RANKL gene expression. These results suggest that PTHrP is expressed within GCT by the stromal cells and can contribute to the abundant RANKL expression and giant cell formation within the tumor.

Identification of potential biomarkers for giant cell tumor of bone using comparative proteomics analysis

Giant cell tumor of bone can be locally aggressive and occasionally can metastasize in the lungs. To identify new markers predictive of aggressive behavior, we analyzed five patients who developed lung metastasis and five who remained disease free for a minimum of 5 years. Using two-dimensional electrophoresis, we detected 28 differentially expressed spots. Fourteen spots were identified using mass spectrometry, including seven up-regulated and seven down-regulated in metastatic samples and classified according to functional categories. We then selected five proteins involved in cell cycle or apoptosis. Thioredoxin peroxidase, allograft inflammatory factor 1, and ubiquitin E2N had more than threefold up-regulation; glutathione peroxidase 1 had 1.9-fold up-regulation; and heat shock protein 27 showed down-regulation in metastatic samples with a very low P value. After validation and analysis of protein levels, evaluation of clinical impact was assessed in a much wider cohort of primary archival specimens. Immunodetection showed a higher frequency of thioredoxin peroxidase, allograft inflammatory factor 1, ubiquitin E2N, and glutathione peroxidase 1 overexpression in primary tumors that developed into lung metastases or that locally relapsed than in the disease-free group, with variable stain intensity and distribution. Kaplan-Meier analysis showed that high expression of glutathione peroxidase 1 was strongly related to local recurrence and metastasis, suggesting that its up-regulation may identify a subset of high-risk patients with giant cell tumor prone to receive diverse clinical management.

Differential gene expression in classic giant cell tumours of bone: Tenascin C as biological risk factor for local relapses and metastases

AIMS

To identify candidate prognostic biological markers useful in selecting high-risk patients with classic primary giant cell tumours (GCT). GCT specimens with different behaviour associated with an increased risk of local and/or distant relapses were studied.

METHODS AND RESULTS

Screening mRNA microarray analysis followed by real-time polymerase chain reaction and immunohistochemistry on tissue microarray sections was used to validate the prognostic role of differentially expressed genes on a larger series by statistical analysis tests. Global gene expression profiling identified 109 differentially expressed genes according to prognosis. A correlation was found between mRNA levels and clinical outcome identifying Tenascin C (TNC) as the most significant prognostic biological marker. By means of backward Wald logistic regression, TNC overexpression defined an eightfold increased risk for metastasis and fourfold for local recurrence. At the protein level, TNC immunoreactivity resulted in a significant difference in the disease-free survival probability curves, providing a stratification for GCT patients, useful for predicting relapse.

CONCLUSIONS

Our study provides important data for the selection of biomarkers with a significant clinical impact and suggests the importance of TNC expression in identifying GCT patients at a higher risk of relapse for closer follow-up and adjuvant medical therapy.

Giant cell tumour of bone

PURPOSE OF REVIEW

Giant cell tumour of bone (GCT) is the most common benign bone tumour and afflicts a young population. Treatment options for patients with unresectable disease have remained fairly static for the past three decades.

RECENT FINDINGS

Recent discoveries have identified a key role for the osteoclast differentiation factor, receptor activator of nuclear factor kappa B (NF-kappaB) ligand (RANKL), in the genesis of GCT. The development of the fully human monoclonal antibody to RANKL, denosumab, has led to a clinical trial in unresectable GCT. This study demonstrated an 86% response rate, with comparable evidence of clinical benefit, and was well tolerated. Other pathways that may present targets for therapy include the hypoxia-angiogenesis axis and the colony stimulating factor 1 receptor.

SUMMARY

Denosumab presents a new treatment option for patients with previously untreatable GCT. The eventual role of denosumab and other targeted agents in the treatment of GCT and related disorders is currently the subject of active study.

Collagenase expression and activity in the stromal cells from giant cell tumour of bone

The characteristic bone destruction in giant cell tumour of bone (GCT) is largely attributed to the osteoclast-like giant cells. However, experimental analyses of bone resorption by cells from GCT often fail to exclude the neoplastic spindle-like stromal cells, and several studies have demonstrated that bone resorption by GCT cells is increased in the presence of stromal cells. The spindle-like stromal cells from GCT may therefore actively contribute to the bone resorption observed in the tumour. Type I collagen, a major organic constituent of bone, is effectively degraded by three matrix metalloproteinases (MMPs) known as the collagenases: MMP-1, MMP-8 and MMP-13. We established primary cell cultures from nine patients with GCT and the stromal cell populations were isolated in culture. The production of collagenases by primary cultures of GCT stromal cells was determined through real-time PCR, western blot analysis and a multiplex assay system. Results show that the cells produce MMP-1 and MMP-13 but not MMP-8. Immunohistochemistry confirmed the presence of MMP-1 and MMP-13 in paraffin-embedded GCT tissue samples. Medium conditioned by the stromal cell cultures was capable of proteolytic activity as determined by MMP-1 and MMP-13-specific standardized enzyme activity assays. The spindle-like stromal cells from GCT may therefore actively participate in the bone destruction that is characteristic of the tumour.

Molecular Pathology of the Genitourinary Tract: Molecular Pathology of Kidney and Testes

With the advent of newer molecular technologies, our knowledge of cellular mechanisms with tumors of the kidney and testis has grown exponentially. Molecular technologies have led to better understanding of interplay between the von Hippel-Lindau gene and angiogenic cytokines in renal cancer and isochromosome 12p in testicular neoplasms. The result has been development of antiangiogenic-targeted therapy within recent years that has become the mainstay treatment for metastatic renal cell cancer. In the near future, classification and diagnosis of renal and testicular tumors through morphologic analysis will be supplemented by molecular information correlating to prognosis and targeted therapy. This article outlines tumor molecular pathology of the kidney and testis encompassing current genomic, epigenomic, and proteonomic findings.

Sarcoma

Sarcomas comprise a heterogeneous group of mesenchymal neoplasms. They can be grouped into 2 general categories, soft tissue sarcoma and primary bone sarcoma, which have different staging and treatment approaches. This review includes a discussion of both soft tissue sarcomas (malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, synovial sarcoma, dermatofibrosarcoma protuberans, angiosarcoma, Kaposi sarcoma, gastrointestinal stromal tumor, aggressive fibromatosis or desmoid tumor, rhabdomyosarcoma, and primary alveolar soft-part sarcoma) and primary bone sarcomas (osteosarcoma, Ewing sarcoma, giant cell tumor, and chondrosarcoma). The 3 most important prognostic variables are grade, size, and location of the primary tumor. The approach to a patient with a sarcoma begins with a biopsy that obtains adequate tissue for diagnosis without interfering with subsequent optimal definitive surgery. Subsequent treatment depends on the specific type of sarcoma. Because sarcomas are relatively uncommon yet comprise a wide variety of different entities, evaluation by oncology teams who have expertise in the field is recommended. Treatment and follow-up guidelines have been published by the National Comprehensive Cancer Network (www.nccn.org).

Giant cell tumor of the uterus: case report and response to chemotherapy

Background

Giant cell tumor (GCT) is usually a benign but locally aggressive primary bone neoplasm in which monocytic macrophage/osteoclast precursor cells and multinucleated osteoclast-like giant cells infiltrate the tumor. The etiology of GCT is unknown, however the tumor cells of GCT have been reported to produce chemoattractants that can attract osteoclasts and osteoclast precursors. Rarely, GCT can originate at extraosseous sites. More rarely, GCT may exhibit a much more aggressive phenotype. The role of chemotherapy in metastatic GCT is not well defined.

Case presentation

We report a case of an aggressive GCT of the uterus with rapidly growing lung metastases, and its response to chemotherapy with pegylated-liposomal doxorubicin, ifosfamide, and bevacizumab, along with a review of the literature.

Conclusion

Aggressive metastasizing GCT may arise in the uterus, and may respond to combination chemotherapy.

Differential gene expression identifies subgroups of ovarian carcinoma

Papillary serous ovarian carcinoma, the most common type of ovarian cancer, displays different biological behavior in different patients. This heterogeneity cannot be recognized by light microscopy. In this study, gene expression in 29 papillary serous ovarian carcinoma samples (21 invasive tumors and 8 borderline tumors), and 17 nonmalignant tissue types comprising 512 samples, was determined using Affymetrix U_133 oligonucleotide microarrays (Affymetrix, Inc., Santa Clara, Calif) representing approximately 40,000 known genes and expression sequence tags (ESTs). Differences in gene expression were quantified as the fold change in gene expression between the various sets of samples. A set of genes was identified that was over-expressed in the invasive ovarian carcinoma samples compared with the normal ovary samples. Principle component analysis of the set of invasive ovarian carcinomas using this set of genes revealed the existence of 2 major subgroups among the invasive ovarian carcinomas. A series of principle component analyses of the ovarian carcinomas using different gene sets composed of genes involved in different metabolic pathways also revealed the same 2 major subgroups of the invasive ovarian carcinomas. Review of the pathology by a single pathologist in a blinded manner suggested that these 2 subgroups differed in pathologic grade. Genes differentially expressed between the 2 ovarian carcinoma subsets were identified. Examination of gene expression in each ovarian carcinoma subset compared with that in 17 different normal tissue types (512 samples) revealed genes specifically over-expressed in ovarian carcinoma compared with these normal tissues. It is concluded that gene expression patterns may be useful in helping to further classify subtypes of papillary serous ovarian carcinoma that may have clinical significance. In addition, the genes identified as over-expressed in each set of serous ovarian carcinoma compared with normal tissues may represent potential biomarkers and/or targets for therapy.

Giant cell tumour of bone: morphological, biological and histogenetical aspects

The giant cell tumour of bone (GCT) is a locally aggressive intraosseous neoplasm of obscure biological behaviour. Although well defined in clinical, radiological and histological terms, detailed information on its biological development is still relatively incomplete. The tumoral tissue consists of three cell types--the neoplastic giant cell tumour stromal cells (GCTSC), representing the proliferative fraction, secondarily recruited mononuclear histiocytic cells (MNHC) and multinuclear giant cells (MNGC). These cellular components interact together with factors that have a role in regulating osteoclast function in normal bone tissue (e.g. RANK, RANKL, OPG, M-CSF). Recent publications suggest that the neoplastic stromal cells express differentiation features of mesenchymal stem cells. Further research of the pathogenesis of GCT as well as the complex interactions of its cellular populations may provide the knowledge necessary for developing approaches for a biological-based therapy of this neoplasm.

Differential gene expression identifies subgroups of renal cell carcinoma

Clear cell carcinoma of the kidney, the most common subtype of renal cell cancer, displays different biological behavior in different patients. This heterogeneity cannot be recognized by light microscopy. In this study, gene expression in 16 clear cell renal cell carcinoma samples and 17 non-malignant tissue types comprising 539 samples was determined using oligonucleotide microarrays representing approximately 40,000 known genes and ESTs. Differences in gene expression were quantified as the fold change in gene expression between the various sets of samples. A set of genes was identified that was overexpressed in the renal cell carcinoma samples compared with the normal kidney samples. Principle component analysis of the set of renal cell carcinomas using this set of genes overexpressed in renal cell cancer revealed the existence of 2 major subgroups among the renal carcinomas. A series of principle component analyses of the set of renal cell carcinomas using different gene sets composed of genes involved in different metabolic pathways also revealed the same 2 major subgroups of the renal cell cancers. Eisen clustering using the same genes also revealed the same 2 major renal cell cancer subsets. Review of the pathology suggested that these 2 subgroups differed in pathologic grade. Genes differentially expressed between the 2 renal cell cancer subsets were identified. Examination of gene expression in each renal cell cancer subset and the pool of renal cell carcinoma samples compared with that in 17 different normal tissues revealed genes specifically overexpressed in renal cell cancer compared with these normal tissues. The authors conclude that gene expression patterns may be useful in helping to further classify subtypes of renal cell carcinoma that may have clinical significance. In addition, the genes identified as overexpressed in each set of clear cell renal cell carcinomas compared with normal tissues may represent useful targets for therapy.

Giant cell tumors of the bone: Molecular profiling and expression analysis of Ephrin A1 receptor, Claudin 7, CD52, FGFR3 and AMFR

Giant cell tumors (GCTs) of the bone are osteolytic neoplasms with variable degrees of aggressiveness. The aim of this study was the molecular characterization of GCT tissue. We established gene expression profiles and discovered a number of genes that have not been described in GCTs before. RNA was prepared from 7 cryopreserved GCTs (primary tumors n = 5, relapses n = 2) and was hybridized to Affymetrix HG U133A microarrays. Paraffin-embedded samples were used for immunohistochemical validation (primary tumors n = 16, relapses n = 6). Gene ontology revealed that the majority of genes, found to be differentially expressed between primary and recurrent GCTs, were associated with receptor tyrosine kinase activity. We selected one upregulated gene (Claudin 7) and four downregulated genes (CD52, Ephrin A1 receptor, autocrine motility factor receptor [AMFR] and fibroblast growth factor receptor 3 [FGFR3] for further analysis using immunohistochemistry. Immunohistochemical analysis of CD52, AMFR, and Ephrin A1 receptor revealed expression profiles concordant with the microarray data, also with regard to differences between primary tumors and relapses.

DC-STAMP is essential for cell-cell fusion in osteoclasts and foreign body giant cells

Osteoclasts are bone-resorbing cells that play a pivotal role in bone remodeling. Osteoclasts form large multinuclear giant cells by fusion of mononuclear osteoclasts. How cell fusion is mediated, however, is unclear. We identify the dendritic cell–specific transmembrane protein (DC-STAMP), a putative seven-transmembrane protein, by a DNA subtraction screen between multinuclear osteoclasts and mononuclear macrophages. DC-STAMP is highly expressed in osteoclasts but not in macrophages. DC-STAMP–deficient mice were generated, and osteoclast cell fusion was completely abrogated in homozygotes despite normal expression of osteoclast markers and cytoskeletal structure. As osteoclast multinucleation was restored by retroviral introduction of DC-STAMP, loss of cell fusion was directly attributable to a lack of DC-STAMP. Defects in osteoclast multinucleation reduce bone-resorbing activity, leading to osteopetrosis. Similar to osteoclasts, foreign body giant cell formation by macrophage cell fusion was also completely abrogated in DC-STAMP–deficient mice. We have thus identified an essential regulator of osteoclast and macrophage cell fusion, DC-STAMP, and an essential role of osteoclast multinucleation in bone homeostasis.

Macrophage fusion: the making of osteoclasts and giant cells

The fusion of cells is a fundamental biological event that is essential for a variety of developmental and homeostatic processes. Fusion is required for the formation of multinucleated osteoclasts and giant cells, although the mechanisms that govern these processes are poorly understood. A new study now reveals an unexpected role for the receptor, dendritic cell–specific transmembrane protein (DC-STAMP), in this process. The potential mechanism by which DC-STAMP governs fusion and the implications of this finding will be discussed.

Giant cell tumor of the temporal bone--a case report

Background

Giant cell tumor is a benign but locally aggressive bone neoplasm which uncommonly involves the skull. The petrous portion of the temporal bone forms a rare location for this tumor.

Case presentation

The authors report a case of a large giant cell tumor involving the petrous and squamous portions of the temporal bone in a 26 year old male patient. He presented with right side severe hearing loss and facial paresis. Radical excision of the tumor was achieved but facial palsy could not be avoided.

Conclusion

Radical excision of skull base giant cell tumor may be hazardous but if achieved is the optimal treatment and may be curative.