FIGURE 5.

Culture in stiff matrices enhances PRL-activated, SFK-mediated phosphorylation of FAK and ERK1/2. A, serum-starved T47D cells in LD or HD collagen gels were treated with or without PRL (4 nm) for the indicated times. Cell lysates were immunoblotted with the indicated antibodies and quantified by densitometry. Means ± S.D. (error bars) are shown. n = 3. The asterisks denote significant differences between treatments as determined by two-way ANOVA followed by paired t test. *, p < 0.05. B, serum-starved T47D cells in low or high density collagen gels were pretreated with vehicle or PP1 (20 μm) for 1 h prior to treatment with or without PRL (4 nm) for 20 min. Cell lysates were immunoblotted with the indicated antibodies, and representative experiments are shown. C and D, 1.5 × 10⁶ serum-starved T47D cells in low or high density collagen gels were treated with or without PRL (4 nm) for 5 (left) or 10 min (right). Cell lysates were immunoprecipitated (IP) for FAK and immunoblotted with the indicated antibodies. Representative blots are shown.