Figure 1.

Cell-surface plasminogen (plg) binding via (pro)-uPA on MDA-MB-231 cells. MDA-MB-231 cells were detached, washed, and pre-incubated on ice for 30 minutes with antibodies against the uPA A-chain, the uPA B-chain, or an irrelevant isotype control antibody. Cells were then washed and incubated for 45 minutes on ice in the dark with fluorescein isothiocyanate-labelled Glu-plg in the absence (total binding) and presence (lysine-independent binding) of 1 mM tranexamic acid. Cells were then washed and analysed for cell-surface plg binding in the presence of 5 μg/ml of the vital stain, propidium iodide, using dual-colour flow cytometry. Lysine-dependent plg binding was calculated by subtracting lysine-independent binding from total binding. Glu, glutamic acid; uPA, urokinase plasminogen activator.