Proteases and interleukin-6 gene analysis in 92 giant cell tumors of bone

Giant cell tumor of bone (GCT) is a benign tumor with a significant tendency to recur locally and rarely to produce pulmonary metastases. It is characterized by the presence of multinucleated osteoclast-like giant cells together with mononuclear spindle-shaped cells. Few prognostic markers have been reported to predict the clinical outcome of GCT patients, so is very important to find the factor that can be implicated in its potential aggressiveness.

Different groups of GCT patients were selected for this study, including patients without evidence of disease and patients who recurred locally or with lung metastasis. The total of 92 tumor samples also included the specimens of the local recurrences and the lung metastases. By using immunohistochemistry and real-time quantitative polymerase chain reaction techniques, the genetic and proteic analyses were performed on the urokinase-type plasminogen activator (u-PA), its receptor (u-PAR) and its inhibitor (PAI-1), which have been described to be frequently implicated in the process of degradation of the extracellular matrix during the metastatic process. Interleukin-6 (IL-6), a cytokine released by GCT cells, which stimulates resorption of bone, was also analyzed.

IL-6, u-PA, u-PAR and PAI 1 genes were found amplified, respectively, in 7%, 5%, 8% and 12% of total cases (92). In particular, the percentages of amplified genes were higher in the GCT cells that gave rise to metastases (12 cases) and in the samples of lung metastases (nine cases) compared with the disease-free group of patients (60 cases).

These results suggest a possible association of these factors with a higher biological aggressiveness of GCT. Morever, it appears that increased expression of the IL-6, u-PA, u-PAR and PAI1 proteins might not depend on mutation of the corresponding genes.