Expression of plasminogen activators and plasminogen activator inhibitor 1 in dedifferentiated chondrosarcoma

BACKGROUND. The plasminogen activator system plays an important role in different malignant tumors. These enzymes participate in the destruction of intercellular matrices and basement membranes and/or can modulate the growth potency of tumor cells and may even promote metastases. In this study, the expression of three glycoproteins that play a role in the plasminogen activator system as activators of proteolysis-urokinase type plasminogen activator (u-PA), tissue type plasminogen activator (t-PA), and plasminogen activator inhibitor type 1 (PAI-I) were studied in various components of dedifferentiated chondrosarcomas of bone. METHODS. The expression of u-PA, t- PA, and PAI-1 was investigated in 10 dedifferentiated chondrosarcomas and 14 conventional chondrosarcomas. The plasminogen activator/inhibitor glycoproteins were visualized immunohistochemically on paraffin sections and the levels of expression were assessed semiquantitatively. RESULTS. In dedifferentiated chondrosarcoma, high grade dedifferentiated components displayed strong, diffuse coexpression of u-PA, t-PA, and PAI-1. For all glycoproteins studied, the immunoreactivity was significantly increased compared with the reactions in the low grade cartilaginous component of the same tumor and conventional chondrosarcoma. In the latter, u-PA, t-PA, and PAI-1 expression was found to be enhanced at invasive foci and in regions of endochondral ossification. CONCLUSIONS. The current study documents the overexpression of u-PA, t-PA, and PAI-1 in dedifferentiated chondrosarcoma and suggests involvement of the plasminogen activator system in the biology of these tumors.