Competition by G3139 for binding of ClRNH32P-OdT18 to collagen I (A), FGF2 (B), PDGF BB (C), and VEGF (D). Competition by G3139 for binding of ClRNH32P-OdT18 to collagen I (A), FGF2 (B), PDGF BB (C), and VEGF (D). G3139 was used as a competitor at the stated concentrations for the binding of the probe (ClRNH32P-OdT18) to the respective heparin-binding proteins, as described in Materials and Methods (left; 12% PAGE). After determination of the IC50 of competition from the plot of normalized band intensity versus log [G3139] (right), values of Kc were determined by the Cheng-Prusoff equation. C.A. Stein et al. Clin Cancer Res 2009;15:2797-2807 ©2009 by American Association for Cancer Research