Pathogenesis of Osteosclerotic Change Following Treatment with an Antibody Against RANKL for Giant Cell Tumour of the Bone.

Background: Giant cell tumours (GCTs) of the bone are intermediate tumours that are locally aggressive. Denosumab, an antibody against receptor activator of nuclear factor kappa-B ligand (RANKL), was recently developed; however, it induces osteosclerotic change through an unknown mechanism. We determined whether osteosclerotic change could be induced by neoplastic stromal cells of giant cell tumours (GCTs).

Patients And Methods: Participants included four patients with GCT of the bone who were treated with neoadjuvant denosumab. Expression of alkaline phosphatase (ALP), osteocalcin (OCN), RANKL and histone H3K36 trimethylation were assessed through immunohistochemistry of biopsy and surgical specimens.

Results: OCN expression was significantly elevated after denosumab treatment, whereas ALP and RANKL expressions were not significantly elevated. Immunofluorescence staining revealed OCN expression and H3K36 trimethylation while their co-localisation was confirmed in the surgical specimens.

Conclusion: Denosumab promoted OCN expression and might induce the osteogenic differentiation of GCT stromal cells.