Fig. 6. DNA replication induced by growth factors is modulated by PD 098059. NIH 3T3 cells were cultured in low serum for 4 h, followed by addition of TGF-ß1 (250 pM), FGF-2 (7 ng/ml), or PDGF (10 ng/ml) in the presence (+, ) or absence (-, ) of 50 µM PD 098059, and the cells were incubated for 12 h. For the last hour of the incubation, BrdUrd was added, after which the cells were fixed and immunostained with anti-BrdUrd antibody. Columns, mean fraction of anti-BrdUrd-stained nuclei as compared with all nuclei was determined from five independent experiments; bars, SD. c, control cells.