The negative feedback mechanism controlling TF expression requires activity of the p70S6 kinase. Western blotting analysis was performed on VEGF- and/or Ang-1–stimulated HUVECs with and without rapamycin. Blots were probed with antibodies against phospho-specific p70S6 kinase targeted at the Thr389 or Thr421/Ser424 site, and β-actin.