Fig. 3. TGF-ß1 treatment increases the half-life of decay of IB- in Hs578T breast cancer cells. In A, cultures of Hs578T cells were plated at a density of 2 x 105 cells/P100 dish the day before treatment. Cells were treated with 5 ng/ml TGF-ß1 or carrier solution for 48 h and then incubated in the presence of the protein synthesis inhibitor 20 µg/ml emetine for 0, 1, 2, or 4 h. Cytoplasmic extracts were prepared, and equal amounts (30 µg) were subjected to immunoblot analysis for IB- or IB-ß. In B, the autoradiograph for a representative experiment for IB- was quantified by densitometric analysis, and the data were presented as a function of the amount present at time zero, set at 100% for the control and TGF-ß1-treated samples. , BSA control; , treated with TGF-ß1.