calcitonin and Giant-Cell-Tumor-of-Bone

We report here a case of primary osteoclastoma that despite possessing HLA-DR-positive status and 'functional' calcitonin receptors, exhibited aggressive in vitro and in vivo bone resorptive activity. In the osteoclast bone slice assay employing scanning electron microscopy, the giant cell-mediated bone resorption was uninhibited by salmon calcitonin (10 nM) and significantly inhibited by raised extracellular calcium (20 mM). In Fura-2AM based microspectrofluorimetric assays, the presence of the 'functional' calcitonin receptors was ascertained by a rise in intracellular calcium induced by calcitonin and high extracellular calcium. These findings provide evidence for a hitherto unrecognized subtype of giant cells that have HLA-DR-positive status, exhibit avid bone resorptive activity, but remain insensitive to calcitonin despite possessing calcitonin receptors.

Topics: Adult; Analgesics; Bone Neoplasms; Bone Resorption; Calcitonin; Calcium; Giant Cell Tumor of Bone; HLA-DR Antigens; Humans; Immunohistochemistry; Microscopy, Electron, Scanning; Receptors, Calcitonin; Spectrometry, Fluorescence; Tumor Cells, Cultured