Figure 3

Cell-surface urokinase plasminogen activator (uPA) binding on PMA-stimulated cells. MCF-7 cells were cultured for 16 hours in 5% foetal calf serum/RPMI containing 100 nM PMA (open symbols) or vehicle control (closed symbols). Cells were detached, washed, and pre-incubated for 30 minutes on ice with increasing concentrations of active uPA or PMSF-inactivated uPA. Cells were then washed and analysed for cell-surface uPA level as in Figure 2. Curves were fitted using a one-site binding equation in GraphPad Prism version 4.00 (GraphPad Software, Inc., San Diego, CA, USA). MFI, mean fluorescence intensity; PMA, 12-O-tetradecanoylphorbol 13-acetate; PMSF, alpha-toluenesulfonyl fluoride.