Fig. 1.

CE inhibits VEGFR2 kinase activity. (A) VEGFR2 was incubated with various concentrations of CE and substrate phosphorylation was monitored by enzyme-linked immunosorbent assay. Data are represented as percentage of control (not treated with CE) and are mean ± SD from four experiments. (B) Lineweaver–Burk plot and (C) Dixon plot of the inhibition of VEGFR2 by CE. Increased concentrations of adenosine triphosphate (ATP) were incubated with VEGFR2 and various concentration of CE. (D and E) CE inhibits VEGFR2 signaling. Quiescent HUVECs were incubated in the presence or absence of CE followed by stimulation with VEGF for another 5 min (for VEGFR2) or 2 h (for MAPK, Stat3, Jak2 and Src). Phosphorylation of VEGFR2, MAPK, Stat3, Jak2 and Src was assessed by western blot. β-Actin/β-tubulin level was used as a loading control. Results are representative of two to four experiments.