FIGURE 4.

IGF-1-mediated stabilization required Erk activity. A and B, tubes were organized as in Fig. 1A, and LPA- or VEGF-driven regression was monitored in the presence of the indicated agents. PD98059 is a MEK inhibitor and was used at 10 μm. *, p < 0.05; **, p < 0.01; ***, p < 0.001; n = 3; one-way ANOVA. C, working model for how IGF-1 prevented regression. IGF-1 triggered prolonged activation of Erk1/2 and, thereby, antagonized Rho/ROCK, which are required for LPA-driven regression (36, 38). D, human (Hs) DUSP1) expression in tubes exposed to LPA, IGF-1, LPA + IGF-1, or VEGF-A. Tubes on a 24-well scale were organized as in Fig. 1A, and then LPA (10 μm) alone or in combination with IGF-1 (100 ng/ml) or VEGF (2.5 ng/ml) was added for 30 min. For each treatment, total RNA extracted from five wells was pooled. Target gene expression relative to GAPDH was quantified by the double derivative method after quantitative real-time RT-PCR and expressed as -fold increase relative to vehicle (assigned a value of 1). The data in the bar graph are averaged from three independent experiments, and each experiment was performed in duplicate wells. *, p < 0.05; **, p < 0.01; ***, p < 0.001 (one-way ANOVA). Veh, vehicle.