Phenotypic characterization of mononuclear and multinucleated cells of giant cell reparative granuloma of small bones

Multiple versus solitary giant cell lesions of the jaw: Similar or distinct entities?

The majority of giant cell lesions of the jaw present as a solitary focus of disease in bones of the maxillofacial skeleton. Less frequently they occur as multifocal lesions. This raises the clinical dilemma if these should be considered distinct entities and therefore each need a specific therapeutic approach. Solitary giant cell lesions of the jaw present with a great diversity of symptoms. Recent molecular analysis revealed that these are associated with somatic gain-of-function mutations in KRAS, FGFR1 or TRPV4 in a large component of the mononuclear stromal cells which all act on the RAS/MAPK pathway. For multifocal lesions, a small group of neoplastic multifocal giant cell lesions of the jaw remain after ruling out hyperparathyroidism. Strikingly, most of these patients are diagnosed with jaw lesions before the age of 20 years, thus before the completion of dental and jaw development. These multifocal lesions are often accompanied by a diagnosis or strong clinical suspicion of a syndrome. Many of the frequently reported syndromes belong to the so-called RASopathies, with germline or mosaic mutations leading to downstream upregulation of the RAS/MAPK pathway. The other frequently reported syndrome is cherubism, with gain-of-function mutations in the SH3BP2 gene leading through assumed and unknown signaling to an autoinflammatory bone disorder with hyperactive osteoclasts and defective osteoblastogenesis. Based on this extensive literature review, a RAS/MAPK pathway activation is hypothesized in all giant cell lesions of the jaw. The different interaction between and contribution of deregulated signaling in individual cell lineages and crosstalk with other pathways among the different germline- and non-germline-based alterations causing giant cell lesions of the jaw can be explanatory for the characteristic clinical features. As such, this might also aid in the understanding of the age-dependent symptomatology of syndrome associated giant cell lesions of the jaw; hopefully guiding ideal timing when installing treatment strategies in the future.

Giant cell tumour of bone: new treatments in development

Giant cell tumour of bone (GCTB) is a benign osteolytic tumour with three main cellular components: multinucleated osteoclast-like giant cells, mononuclear spindle-like stromal cells (the main neoplastic components) and mononuclear cells of the monocyte/macrophage lineage. The giant cells overexpress a key mediator in osteoclastogenesis: the RANK receptor, which is stimulated in turn by the cytokine RANKL, which is secreted by the stromal cells. The RANK/RANKL interaction is predominantly responsible for the extensive bone resorption by the tumour. Historically, standard treatment was substantial surgical resection, with or without adjuvant therapy, with recurrence rates of 20–56 %. Studies with denosumab, a monoclonal antibody that specifically binds to RANKL, resulted in dramatic treatment responses, which led to its approval by the United States Food and Drugs Administration (US FDA). Recent advances in the understanding of GCTB pathogenesis are essential to develop new treatments for this locally destructive primary bone tumour.

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.

Orthopedic and Orthodontic Treatment in Central Giant Cell Granuloma Treated with Calcitonin

Central giant cell granuloma of the jaw is a benign lesion of unknown etiology that occurs with very low frequency. It mainly occurs in children and young adults and is more common in the mandible. The most common treatment is surgical removal; however, alternative therapies (intralesional injections of corticosteroids, interferon alpha, and calcitonin) have been used in order to avoid undesirable damage to the jaws and teeth. The lesion may cause root resorption, tooth germ displacement, and other dental problems, as well as malocclusion that must be treated orthodontically. The orthodontic, orthopedic, and calcitonin-based treatments of one of these cases is presented.

Mitf induction by RANKL is critical for osteoclastogenesis

Microphthalmia-associated transcription factor (Mitf) regulates the development and function of several cell lineages, including osteoclasts. In this report, we identified a novel mechanism by which RANKL regulates osteoclastogenesis via induction of Mitf isoform E (Mitf-E). Both Mitf-A and Mitf-E are abundantly present in osteoclasts. Unlike Mitf-A, which is ubiquitously expressed and is present in similar amounts in macrophages and osteoclasts, Mitf-E is almost nondetectable in macrophages, but its expression is significantly up-regulated during osteoclastogenesis. In addition to their different expression profiles, the two isoforms are drastically different in their abilities to support osteoclastogenesis, despite sharing all known functional domains. Unlike Mitf-A, small amounts of Mitf-E are present in nuclear lysates unless chromatin is digested/sheared during the extraction. Based on these data, we propose a model in which Mitf-E is induced during osteoclastogenesis and is closely associated with chromatin to facilitate its interaction with target promoters; therefore, Mitf-E has a stronger osteoclastogenic activity. Mitf-A is a weaker osteoclastogenic factor, but activated Mitf-A alone is not sufficient to fully support osteoclastogenesis. Therefore, this receptor activator for nuclear factor-kappaB ligand (RANKL)-induced Mitf phenomenon seems to play an important role during osteoclastogenesis. Although the current theory indicates that Mitf and its binding partner Tfe3 are completely redundant in osteoclasts, using RNA interference, we demonstrated that Mitf has a distinct role from Tfe3. This study provides the first evidence that RANKL-induced Mitf is critical for osteoclastogenesis and Mitf is not completely redundant with Tfe3.

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.

Giant cell reparative granuloma of the proximal tibia: a case report

Giant cell reparative granulomas (GCRGs) are non-neoplastic inflammatory lesions, usually of the jaw or gingiva or small bones of the hands and feet. We report one such case in the right proximal tibia of a 45-year-old man. Radiological studies showed a lytic lesion with marginal sclerosis in the epiphysis and metaphysis. After open biopsy, a preliminary diagnosis of a benign giant cell tumour was made. One month after admission, the lesion was curetted and filled with cancellous bone and hydroxyapatite. Based on the histology of the curetted lesion, the diagnosis was changed to a GCRG. The patient had an uneventful postoperative course, with no evidence of local recurrence and metastasis. He died from gastric cancer 2 years later.

Adjuvant Antiangiogenic Therapy for Giant Cell Tumors of the Jaws

PURPOSE

To further evaluate a novel treatment protocol for the management of aggressive giant cell lesions (GCLs) consisting of enucleation followed by adjuvant subcutaneous interferon alpha therapy.

PATIENTS AND METHODS

Using a retrospective case series study design, a sample of patients with aggressive GCLs was enrolled between April 1995 and June 2006. Lesions were enucleated with preservation of vital structures. Postoperatively, the patients received daily subcutaneous interferon alpha (3 million units/m2 of body surface area). Interferon treatment continued with regular clinical and radiographic follow-up until the surgical defects filled in with bone, as demonstrated by panoramic radiographs and confirmed by computed tomography. Side effects, such as fever, fatigue, weight loss, decreased white blood cell count, decreased platelet count and elevated liver enzymes, were monitored. After completion of interferon therapy, patients followed for 2 years without evidence of recurrence were considered cured of disease.

RESULTS

The study sample was comprised of 26 subjects (65% female) with a mean age of 18.5 years. At the time of this writing, 16 of the subjects have completed the protocol and are cured of disease, 6 are in remission, and 4 are in active treatment. Four subjects experienced significant side effects from the interferon, requiring modification of treatment.

CONCLUSIONS

Enucleation of aggressive GCLs with preservation of vital structures and adjuvant interferon is an excellent strategy for managing aggressive GCLs. Approximately 15% of subjects developed significant side effects limiting interferon administration and necessitating alternative therapies.

Central giant cell granuloma of the jaw: a review of the literature with emphasis on therapy options

Central giant cell granuloma (CGCG) is a benign lesion of the jaws with an unknown etiology. Clinically and radiologically, a differentiation between aggressive and non-aggressive lesions can be made. The incidence in the general population is very low and patients are generally younger than 30 years. Histologically identical lesions occur in patients with known genetic defects such as cherubism, Noonan syndrome, or neurofibromatosis type 1. Surgical curettage or, in aggressive lesions, resection, is the most common therapy. However, when using surgical curettage, undesirable damage to the jaw or teeth and tooth germs is often unavoidable and recurrences are frequent. Therefore, alternative therapies such as injection of corticosteroids in the lesion or subcutaneous administration of calcitonin or interferon alpha are described in several case reports with variable success. Unfortunately, randomized clinical trials are very rare or nonexistent. In the future, new and theoretically promising therapy options, such as imatinib and OPG/AMG 162, will be available for these patients.

Calcitonin therapy in central giant cell granuloma of the jaw: a randomized double-blind placebo-controlled study

The successful therapeutic use of calcitonin in patients with a central giant cell granuloma has been shown in several case reports. In a prospective, randomized, double-blinded, placebo-controlled clinical trial, 14 patients with a histologically confirmed central giant cell granuloma and normal calcium and parathyroid hormone serum levels were studied over 2 years. Patients were treated with intranasally administered salmon calcitonin (200 IU/day) or a placebo once a day. The placebo-controlled period was 3 months, after which all patients were treated with calcitonin for 1 year. Treatment response was assessed at the end of the placebo-controlled study phase (3 months), at the end of therapy (15 months' timepoint with patients being on calcitonin treatment for either 12 or 15 months) and at 6 months' follow-up. The chi(2)-test was used to compare the proportion of patients with a tumour reduction >/=10% of the pretreatment measurement between the 2 populations at the 3 timepoints: no differences were observed between the placebo group and the calcitonin group. At the 6-month follow-up timepoint, tumour volume had decreased by >/=10% in a total of 7 patients with a 37.9% (95% CI 31.3-44.5%) mean volume reduction in this subgroup. Complete remission was not observed.

Stimulation of osteoclast formation by inflammatory synovial fluid

Peri-articular bone resorption is a feature of arthritis due to crystal deposition and rheumatoid disease. Under these conditions, the synovial fluid contains numerous inflammatory cells that produce cytokines and growth factors which promote osteoclast formation. The aim of this study was to determine whether inflammatory synovial fluid stimulates the formation of osteoclasts. Synovial fluid from rheumatoid arthritis (RA), pyrophosphate arthropathy (PPA) and osteoarthritis (OA) patients was added to cultures (n=8) of human peripheral blood mononuclear cells (PBMCs) in the presence and absence of macrophage colony-stimulating factor (M-CSF) and the receptor activator of NF-kappaB ligand (RANKL). Osteoclast formation was assessed by the formation of cells positive for tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor (VNR) and the extent of lacunar resorption. The addition of 10% OA, RA and PPA synovial fluid to PBMC cultures resulted in the formation of numerous multinucleated or mononuclear TRAP(+) and VNR(+) cells which were capable of lacunar resorption. In contrast to PBMC cultures incubated with OA synovial fluid, there was marked stimulation of osteoclast formation and resorption in cultures containing inflammatory RA and PPA synovial fluid which contained high levels of tumour necrosis factor alpha, a factor which is known to stimulate RANKL-induced osteoclast formation.

NEW MOLECULES IN THE TUMOR NECROSIS FACTOR LIGAND AND RECEPTOR SUPERFAMILIES WITH IMPORTANCE FOR PHYSIOLOGICAL AND PATHOLOGICAL BONE RESORPTION

Osteoclasts are tissue-specific polykaryon bone-resorbing cells derived from the monocyte/macrophage hematopoietic lineage with specialized functions required for the adhesion of the cells to bone and the subsequent polarization of the cell membrane, secretion of acid to dissolve mineral crystals, and release of proteolytic enzymes to degrade the extracellular matrix proteins. Most pathological conditions in the skeleton lead to loss of bone due to excess osteoclastic bone resorption, including periodontal disease, rheumatoid arthritis, and osteoporosis. In rare cases, most of them genetic, patients with osteopetrosis exhibit sclerotic bone due either to a lack of osteoclasts or to non-functional osteoclasts. Mainly because of phenotypic findings in genetically manipulated mice or due to spontaneous mutations in humans, mice, and rats, several genes have been discovered as being crucial for osteoclast formation and activation. Recent breakthroughs in our understanding of osteoclast biology have revealed the critical roles in osteoclast differentiation played by RANKL, RANK, and OPG, three novel members of the tumor necrosis factor ligand and receptor superfamilies. The further study of these molecules and downstream signaling events are likely to provide a molecular basis for the development of new drugs for the treatment of diseases with excess or deficient osteoclastic bone resorption.

Giant cell granuloma of the temporal bone: a case report with immunohistochemical, enzyme histochemical, and in vitro studies

A case of giant cell granuloma (GCG) that occurred in the right temporal bone is reported. The lesion showed histologic features identical to GCG. The multinuclear giant cells (MGCs) in the lesion showed strong reactivity with CD68, but patchy staining for myeloid/histiocyte antigen, alpha-1-antitrypsin, alpha-1-antichymotrypsine, and lysozyme. Activity of tartrate-resistant acid phosphatase was also consistently detected in the MGCs. Some of the mononuclear cells of the lesion exhibited similar immunocytochemical and histochemical reactivity as the MGCs. Ki-67 staining, however, was only detected in the mononuclear cells. The MGCs isolated from the lesion presented characteristic morphology of osteoclasts and possessed the ability to excavate bone in vitro. Thus, the MGCs in GCG appeared to express both macrophage- and osteoclast-associated phenotypes. The mononuclear cells were the major proliferative elements in the lesion and a subpopulation of these cells may represent precursors of the MGCs.