EXPRESSION AND LOCALIZATION OF UROKINASE-TYPE PLASMINOGEN-ACTIVATOR RECEPTOR IN HUMAN GLIOMAS

Urokinase-type plasminogen activator receptors (uPARs) play an importa nt role in tumor invasion by localizing degradative enzymes at the inv asive zone. In the present study, we examined the presence and distrib ution of uPARs in human gliomas ill vivo. The amounts of uPARs were me asured by radioreceptor assays and Northern blotting and were signific antly higher in anaplastic astrocytomas and glioblastomas than they we re in normal brain tissues and low-grade gliomas. In situ hybridizatio n was performed to investigate the cellular source of uPAR mRNA in var ious types of astrocytomas and normal brain tissues, uPAR mRNA was loc alized in astrocytoma cells and endothelial cells within tumor tissue, especially near sites of vascular proliferation and at the leading ed ges of tumors. uPAR mRNA was also expressed in tumor cells near necrot ic areas. Expression was barely detectable in low-grade astrocytomas a nd normal brain tissues. These results suggest that expression of uPAR in the invading astrocytoma cells may play a significant role in the invasive behaviors of glioblastomas.