The cell-surface urokinase plasminogen activator receptor (uPAR) plays a key role in regulating plasminogen cleavage during extracellular proteolysis. Our recent results demonstrated that uPAR expression is critical for the invasiveness of human gliomas and down regulation of uPAR caused by antisense cDNA transfection inhibits the invasion of these stable antisense uPAR-transfectant clones. To study the role of uPARs in glioma cell invasion, a human neuroglioma cell line (H4) that normally produces low numbers of uPARs was transfected with the expression vector containing full-length human uPAR cDNA. Stable transfectants were analyzed for uPAR mRNA expression, receptor number, in vitro invasion and secretion of uPA and MMP-2. The uPAR-overproducing clones showed a 4-fold increase in uPAR mRNA transcription and approximately 40% increase in receptor numbers. uPAR-overproducing clones also invaded through matrigel to a significantly greater extent than did parent cell line and vector clones. However, the uPAR-overexpressing clones and parent cell lines showed similar uPA and MMP-2 activities. These results suggest that the over-production of uPAR on the surface of neuroglioma cells enhances the invasiveness.

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