Figure 4.

Inhibition of VEGF-mediated endothelial cell proliferation in vitro and the antitumor effect by the adoptive transfer of Igs in vivo. (A) Human umbilical vein endothelial cells were incubated with mouse or human VEGF (300 ng/ml) in the presence of various concentrations of immunoglobulins. Treatment with immunoglobulins from mice immunized with XVEGF-p (■) resulted in the apparent inhibition of endothelial cell proliferation, compared with mice immunized with MVEGF-p (○) or c-p (●) or with nonimmunized mice (▴). But it had no effect on bFGF-mediated endothelial cell proliferation (data not shown). (B) Adoptive transfer of immunoglobulins in vivo. The protective antitumor effect against Meth A cells was tested with purified immunoglobulins (25 mg/kg) from mice immunized with XVEGF-p (●), MVEGF-p (○), or c-p (■) or from nonimmunized mice (▴). Results are expressed as means ± SEM. Asterisks (*) indicate a significant difference in tumor volume (P < 0.05) between immunoglobulins from XVEGF-immunized mice and all other control groups. (C) The survival of the mice in B. Treatment of the mice with immunoglobulins from XVEGF-p-immunized mice (●) resulted in a significant increase in survival, compared with the other controls (P < 0.0005, by log rank test). (D) Protective antitumor effect against Meth A fibrosarcoma was tested with immunoglobulins from mice immunized with XVEGF-p and control vaccines, and immunoglobulins before adoptive transfer were adsorbed with VEGF or bFGF by the immunoadsorption method as detailed (51). The adsorption of the immunoglobulins with VEGF (■) could abrogate the antitumor activity of immunoglobulins from XVEGF-p-immunized mice (●) (P < 0.0005, by log rank test), but bFGF (○) had no effect (P > 0.05). The control groups include immunoglobulins from the mice treated with saline alone (▴) and from MVEGF-p- or c-p-immunized mice (not shown).