Binding of ¹²⁵I-Gly158scuPA to serum-free cultures of LM-TK⁻ cells and their extracellular matrix. Cells were grown for 14 days in completely serum-free medium on gelatin- or fibronectin-coated dishes. Before the binding experiment, the cells were preincubated with buffer only (hatched bars) or with 10 μg/mL multimeric VN for 48 hours (filled bars). Binding of ¹²⁵I-Gly158scuPA to cells and extracellular matrix in the absence or presence of suPAR (1 μg/mL) was performed as indicated. Results are mean ± SEM (cpm/well) of triplicate wells. Similar results were obtained in three separate experiments.