Apoptosis in Giant Cell Tumors of Bone

Although giant cell tumor of bone (GCT) is characterized by the extensive multinucleated giant cells among mononuclear stromal cells, proliferation of these cells and multinucleation are not without limit in certain cases. Few studies on oncogenesis of GCT have focused on the negative growth control, including growth arrest and apoptosis. The purpose of this study was to investigate the mechanism of cell death in multinucleated giant cells and stromal cells of GCT. In this study, we have demonstrated that GCT cells can undergo apoptosis. The cells in surgical specimen were positively stained in situ nick end labeling methods, and electron micrographs showed the morphological changes associated with apoptosis in some of stromal cells and multinucleated giant cells. A candidate responsible for this apoptosis was then examined using cultured GCT cells. We focused on Fas that is a major trigger of apoptosis. Cultured GCT cells expressed detectable amount of Fas on their surface. Although GCT cells did a little undergo apoptosis following treatment with anti-Fas alone, combination treatment with cyclohexamide led to an increase in apoptosis of the GCT cells. These data suggested that the sensitizing activity of cyclohexamide on anti-Fas mediated cytotoxicity could happen in vitro.