Inhibition of UPA activity by PAI-2. Inhibition of uPA activity was assessed using the chromogenic assays as described in “Methods and materials.” Supernatants from cells showing forced expression of exogenous GFP or ZNF198 showed virtually undetectable inhibition of uPA activity. In contrast, supernatants from 2 different cell clones expressing the ZNF198/FGFR1 fusion kinase (FUS) show inhibition of uPA activity proportional to the levels of the input protein.