sVEGFR-3 inhibits VEGF-C–induced VEGFR-2 phosphorylation but not VEGF-A–induced VEGFR-2 phosphorylation. (A) Immunoprecipitation by VEGFR-2 antibody from HUVEC lysate. The input shows soluble and membrane VEGFR-3 bands. However, VEGFR-3 bands were not detected after precipitation, indicating that the two receptors do not heterodimerize. (B) After 24 hours of serum starvation, HUVEC was stimulated with 20 ng/mL VEGF-A or 20 ng/mL VEGF-A + 500 ng/mL recombinant sVEGFR-3. Recombinant sVEGFR-3 did not block VEGF-A–induced VEGFR-2 phosphorylation. (C) After 24 hours of serum starvation, HUVEC was stimulated with 20 ng/mL, 100 ng/mL, or 500 ng/mL VEGF-C or 500 ng/mL VEGF-C + 1750 ng/mL recombinant sVEGFR-3. Recombinant sVEGFR-3 treatment inhibits VEGF-C–induced VEGFR-2 phosphorylation. IP, immunoprecipitation; WB, western blot.