Fig. 7. Optimum response of the PAI-1 gene to TGF-ß1 stimulation in T2 cells requires substrate adhesion. TGF-ß1-induced PAI-1 transcripts requires adhesion (to a fibronectin (FN) substrate) since cells cultured in suspension (agarose, Ag) or stimulated with TGF-ß1 (1 ng/ml) in suspension (Ag+TGF-ß1) did not express PAI-1 mRNA (A). Cells plated onto FN from suspension culture (AgFN) did produce low levels of PAI-1 transcripts, whereas plating onto FN in the presence of TGF-ß1 (AgFN+TGF-ß1) yielded optimal induction. PAI-1 induction as a consequence of FN attachment alone was also attenuated by addition of PD98059 during the 2 hour period of adhesion suggesting that MEK activity was also required for adhesion-dependent expression under growth factor-free conditions (B).