Involvement of VEGFR-2 and VEGFR-3 in the lymphatic sprouting induced by Notch inhibition in vitro. (A-B) LEC-coated beads were treated with a blocking Ab against VEGFR-2 (5 μg/mL) or VEGFR-3 (10 μg/mL), a soluble VEGFR-1-Fc (5 μg/mL) or VEGFR3-Fc (5 μg/mL) or control hIgG, in the presence of Dll4-Fc (20 μg/mL) and stained for PECAM-1. Scale bars, 100 μm. (C-D) Quantification of the sprouting in panels A and B. anti-R2 indicates anti–VEGFR-2; anti-R3, anti-VEGFR-3; R1-Fc, VEGFR-1-Fc; and R3-Fc, VEGFR-3-Fc. Results represent means ± SEM summarized from 2 independent experiments with n = 6-12 per group per experiment; ***P < .001 compared with the last bar in panel C.