EXPRESSION OF PLASMINOGEN ACTIVATORS AND PLASMINOGEN-ACTIVATOR INHIBITOR-1 IN DEDIFFERENTIATED CHONDROSARCOMA

BACKGROUND, The plasminogen activator system plays an important role i n different malignant tumors. These enzymes participate in the destruc tion of intercellular matrices and basement membranes and/or can modul ate 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-urok inase type plasminogen activator (u-PA), tissue type plasminogen activ ator (t-PA), and plasminogen activator inhibitor type 1 (PAI-1) were s tudied in various components of dedifferentiated chondrosarcomas of bo ne. METHODS. The expression of u-PA, t-PA, and PAI-1 was investigated in 10 dedifferentiated chondrosarcomas and 14 conventional chondrosarc omas. The plasminogen activator/inhibitor glycoproteins were visualize d immunohistochemically on paraffin sections and the levels of express ion were assessed semiquantitatively. RESULTS. In dedifferentiated cho ndrosarcoma, high grade dedifferentiated components displayed strong, diffuse coexpression of u-PA, t-PA, and PAI-1. For all glycoproteins s tudied, the immunoreactivity was significantly increased compared with the reactions in the low grade cartilaginous component of the same tu mor and conventional chondrosarcoma. In the latter, u-PA, t-PA, and PA I-1 expression was found to be enhanced at invasive foci and in region s of endochondral ossification. CONCLUSIONS. The current study documen ts the overexpression of u-PA, t-PA, and PAI-1 in dedifferentiated cho ndrosarcoma and suggests involvement of the plasminogen activator syst em in the biology of these tumors. (C) 1997 American Cancer Society.