Lymphoma proliferation experiments. Cells (RL, SKI-DLBCL) were plated at 2 × 10⁴ cells/well in triplicate in 96-well, round-bottom plates and were incubated for 48 hours in the presence of serum-free media, growth factors, or VEGFR antibodies. [³H]-Tritiated thymidine (0.5 μCi/well [0.0185 MBq/well]) was added, and radioisotope incorporation into cells after 18 hours of exposure was measured. Experiments were performed at least 3 times, and results of 1 representative experiment are shown. Because of variations in baseline [³H]-tritiated thymidine incorporation between experiments, data are expressed as fold change of the serum-free control for each experiment. (A) Growth of lymphoma cells in the presence of serum-free media, VEGF (50 ng/mL), anti–human VEGFR-2 antibody (IMC-1C11 10 μg/mL), or VEGF + IMC-1C11 (same concentrations). (B) Growth of lymphoma cells in the presence of serum-free media, PlGF (200 ng/mL), anti–human VEGFR-1 antibody (6.12 10 μg/mL), or PlGF + 6.12 (same concentrations). (C) Growth of lymphoma cells in the presence of serum-free media, VEGF (50 ng/mL), 6.12 (10 μg/mL), or VEGF + 6.12 (same concentrations).