TPO-mediated upregulation of adhesion of HEL cells to fibrinogen is completely inhibited by the PI 3-K inhibitor WT. Binding of ⁵¹Cr-labeled HEL cells to fibrinogen-coated plates was assessed in the presence of no stimulus (nil) or 100 ng/mL TPO in the absence or presence of various doses of WT. Results are expressed in cpm, and represent means ± SD of three separate experiments.