Urokinase Plasminogen Activation System Modulation in Transformed Cell Lines

The role of the plasminogen activation system is to regulate the activity of the extracellular protease plasmin. It comprises the urokinase plasminogen activator (uPA), a specific extracellular protease which activates plasminogen, its inhibitor PAI1, and the urokinase plasminogen activator receptor, uPAR, which localizes the urokinase activity. The plasminogen activation system is involved in tissue remodeling through extracellular matrix degradation, and therefore participates in numerous physiological and pathological processes, which make it a potential biomarker. To investigate the role of these molecules in the cellular processes, we cloned human uPA, PAI1, and uPAR and overexpressed them in two cell lines, the glioblastoma line A1235 and the transformed human embryonal kidney cells HEK 293. We analyzed the urokinase activity and the expression of plasminogen activation system elements on the protein and RNA level by Western blot analysis and RTqPCR. Cell proliferation was followed up by cell counting, cell migration and invasion by wound-healing and the transwell assays, respectively, and cell adhesion and dispersal by spheroid formation. The cells transfected with urokinase sequence had increased urokinase activity and uPA expression, while the PAI1-transfected cells decreased urokinase activity, increased PAI1 expression, and decreased cell migration. HEK 293 cells expressing PAI formed only small spheroids. The effects of the uPA system molecules depended on their interactions with each other and with other molecules in the microenvironment, as well as on the cell-type-specific signaling.