Fig. 3. FGF-2 and PDGF induce p21 mRNA levels. A and B, Northern blotting analyses of p21 mRNA levels. A, NIH 3T3 cells were pretreated in low serum with or without PD 098059 (80 µM) for 4 h followed by incubation with FGF-2 (5 ng/ml), PDGF (10 ng/ml), or TGF-ß1 (250 pM) for 1 h. B, NIH 3T3 cells were cultured in low serum in the absence (Lanes -) or presence (Lanes +) of 50 µM PD 098059 and TGF-ß1 (250 pM), FGF-2 (7 ng/ml), or PDGF (10 ng/ml) for 16 h. Poly(A)+ mRNAs were prepared, and Northern blotting analyses were performed using 32P-labeled mouse p21 and GAPDH cDNAs as probes. The signals were quantitated by PhosphoImager analyzer and normalized against GAPDH. Fold induction of p21 mRNA as compared with nontreated controls are shown below.