Figure 4.

Inhibitory trap effects of the 59.8-kDa N-terminal VEGFR1 fragment of cleaved rmVEGFR1 on VEGF-A₁₆₅-induced mitogenic activity. (A) Cleaved 59.8-kDa rmVEGFR1 fragments were preincubated with 10 ng/mL VEGF-A₁₆₅ for 30 minutes and then added onto plated CPAEs for 10 minutes. Total lysates were harvested for Western blot analysis. Greater ERK protein activation (p-ERK) was observed in cells treated with VEGF-A₁₆₅ only (lane 2) compared to the control (nonstimulated, lane 1). VEGF-induced ERK protein phosphorylation was diminished following the incubation of cells with the cleaved fragment (lane 3). (B) Cleaved 59.8-kDa rmVEGFR1 fragments were preincubated with 10 ng/mL VEGF-A₁₆₅ for 30 minutes and then added onto plated CPAEs for 48 hours. Bromodeoxyuridine incorporation was used to measure proliferating cells. CPAEs were stimulated with VEGF-A₁₆₅ only as a positive control.