Sustained Autocrine Induction and Impaired Negative Feedback of Osteoclastogenesis in CD14+ Cells of Giant Cell Tumor of Bone

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

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

Bisphosphonate-loaded Bone Cement as a Local Adjuvant Therapy for Giant Cell Tumor of Bone: A 1 to 12-Year Follow-up Study

BACKGROUND

Historically, nontargeted adjuvant therapies such as liquid nitrogen, phenol, argon beam, and alcohol have been applied locally after curettage of giant cell tumors (GCT) in the extremities. Systemic bisphosphonates (BP) and denosumab have emerged as osteoclast-targeting therapies because osteoclast-like giant cells, responsible for aggressive bone resorption, are susceptible to BP or denosumab. However, such drugs may cause systemic side effects. We examined the effects of an alternative intraoperative local delivery of BP on GCTs.

MATERIALS AND METHODS

In total, 17 patients with GCTs underwent extended surgical curettage procedures consisting of high-speed burring, traditional adjuvant therapy, and application of BP-loaded polymethylmethacrylate bone cement. Clinical data and follow-up radiographs were reviewed to investigate local recurrence (LR) rate and complications in a retrospective manner.

RESULTS

There were 6 males and 11 females (mean age, 33.7 y). There were no cases of pulmonary metastases. Patient follow-up ranged from 1 to 12 years. There was 1 LR during the follow-up period for an LR rate of 5.9%. The mean final Musculoskeletal Tumor Society (MSTS) score was 29. There were no systemic or localized avascular necrosis or atypical fractures related to BPs noted.

CONCLUSIONS

BP-loaded polymethylmethacrylate is a targeted local adjuvant therapy that is feasible, safe, and may reduce LRs while alleviating the risk of systemic side effects of BPs such as avascular necrosis of jaw and atypical femur fractures. Future prospective randomized clinical trials will strengthen the level of evidence of this proposed targeted therapy.

LEVEL OF EVIDENCE

Therapeutic level IV-see instructions for authors for a complete description of evidence.

In Vitro Study of the Effects of Denosumab on Giant Cell Tumor of Bone: Comparison with Zoledronic Acid

Giant cell tumor of bone (GCTB) is a locally aggressive primary bone tumor that contains numerous osteoclasts formed from marrow-derived precursors through receptor activator of nuclear factor κ-B ligand (RANKL), an osteoclast differentiation factor expressed in neoplastic cells of GCTB. Denosumab, a fully human monoclonal antibody targeting RANKL, has recently been used for the treatment of GCTB, and superior treatment effects have been reported. The aim of this work was to elucidate the mechanism of action of denosumab, and the differences between denosumab and zoledronic acid at the level of GCTB cells. We isolated GCTB cells from 3 patients and separated them into osteoclasts, osteoclast precursors and proliferating spindle-shaped stromal cells (the true neoplastic component), and examined the action of denosumab on differentiation, survival and bone resorption activity of osteoclasts. Denosumab and zoledronic acid inhibited osteoclast differentiation from mononuclear cells containing osteoclast precursors. Zoledronic acid inhibited osteoclast survival, whereas an inhibitory effect of denosumab on osteoclast survival was not observed. The inhibitory effect on bone resorption by both agents was confirmed in culture on dentin slices. Furthermore, zoledronic acid showed dose-dependent inhibition of cell growth of neoplastic cells whereas denosumab had no inhibitory effect on these cells. Denosumab has an inhibitory effect on osteoclast differentiation, but no inhibitory effects on survival of osteoclasts or growth of neoplastic cells in GCTBs.

Energy metabolism in osteoclast formation and activity

Osteoclastogenesis and osteolysis are energy-consuming processes supported by high metabolic activities. In human osteoclasts derived from the fusion of monocytic precursors, we found a substantial increase in the number of mitochondria with differentiation. In mature osteoclasts, mitochondria were also increased in size, rich of cristae and arranged in a complex tubular network. When compared with immature cells, fully differentiated osteoclasts showed higher levels of enzymes of the electron transport chain, a higher mitochondrial oxygen consumption rate and a lower glycolytic efficiency, as evaluated by extracellular flux analysis and by the quantification of metabolites in the culture supernatant. Thus, oxidative phosphorylation appeared the main bioenergetic source for osteoclast formation. Conversely, we found that bone resorption mainly relied on glycolysis. In fact, osteoclast fuelling with galactose, forcing cells to depend on Oxidative Phosphorylation by reducing the rate of glycolysis, significantly impaired Type I collagen degradation, whereas non-cytotoxic doses of rotenone, an inhibitor of the mitochondrial complex I, enhanced osteoclast activity. Furthermore, we found that the enzymes associated to the glycolytic pathway are localised close to the actin ring of polarised osteoclasts, where energy-demanding activities associated with bone degradation take place. In conclusion, we demonstrate that the energy required for osteoclast differentiation mainly derives from mitochondrial oxidative metabolism, whereas the peripheral cellular activities associated with bone matrix degradation are supported by glycolysis. A better understanding of human osteoclast energy metabolism holds the potential for future therapeutic interventions aimed to target osteoclast activity in different pathological conditions of bone.

Expression of colony-stimulating factor 1 is associated with occurrence of osteochondral change in pigmented villonodular synovitis

Pigmented villonodular synovitis (PVNS) is a benign, translocation-derived neoplasm. Because of its high local recurrence rate after surgery and occurrence of osteochondral destruction, a novel therapeutic target is required. The present study aimed to evaluate the significance of protein expression possibly associated with the pathogenesis during the clinical course of PVNS. In 40 cases of PVNS, positivity of colony-stimulated factor 1 (CSF1), its receptor (CSF1R), and receptor activator of nuclear factor kappa-B ligand (RANKL) were immunohistochemically determined. The relationship between the positivity and clinical outcomes was investigated. High positivity of CSF1 staining intensity was associated with an increased incidence of osteochondral lesions (bone erosion and osteoarthritis) (p = 0.009), but not with the rate of local recurrence. Positivity of CSF1R and RANKL staining was not associated with any clinical variables. The number of giant cells was not correlated with positivity of any of the three proteins, or with the clinical outcome. Focusing on knee cases, CSF1 positivity was also associated with the incidence of osteochondal change (p = 0.02). CSF1R positivity was high in cases which had local recurrence, but not significantly so (p = 0.129). Determination of CSF1 and CSF1R expression may be useful as a prognosticator of the clinical course and/or outcomes of PVNS.

The dilemma of denosumab: Salvage of a femoral head giant cell tumour

INTRODUCTION

Denosumab is a monoclonal RANKL antibody which has been shown to be highly effective in treating giant cell tumour (GCT) of bone. We report on its use as a neo-adjuvant agent to avoid morbid surgery for an adolescent.

PRESENTATION OF CASE

We report a case of a15-year old female with a Campanacci 3 GCT involving the femoral head and neck.

DISCUSSION

To preserve bone stock and avoid an outright hip replacement, the patient was given denosumab pre-operatively to consolidate the tumour. After receiving 6 months of treatment, a rim of cortical bone had developed to allow an extended curettage of the tumour to be performed without fear of collapse of the articular surface.

CONCLUSION

This is the first reported case of the use of denosumab in GCT of the femoral head and neck. We describe our experience in the neo-adjuvant use of denosumab and offer suggestions for future use. Further studies will be needed to see if denosumab has a role in conventional GCT and whether it can lead to a lowering of local recurrence rates.