Antibody to vascular endothelial growth factor slows growth of an androgen-independent xenograft model of prostate cancer.

Abstract

Human tumors are dependent on angiogenesis for growth, and vascular endothelial growth factor (VEGF) is a major regulator of this process. We aimed to study clinical utility of a recombinant humanized monoclonal anti-VEGF antibody (rhu alpha VEGF) in the treatment of the CWR22R androgen-independent xenograft model of prostate cancer. rhu alpha VEGF has previously shown clinical activity in several xenograft cancer models. We administered 5 mg/kg rhu alpha VEGF i.p. twice weekly as a single agent and together with paclitaxel to established CWR22R xenografts. rhu alphaVEGF inhibited established tumor growth by 85% (P < 0.01 for trajectories of the average tumor volumes of the groups) at 3 weeks, but after cessation of rhu alpha VEGF treatment, tumor regrowth ensued. A paclitaxel dosage of 6.25 mg/kg s.c. five times/week slowed tumor growth (72% compared with controls at 3 weeks, P = 0.02). The combination of paclitaxel and rhu alpha VEGF resulted in greater inhibition of tumor growth than that observed with either agent alone (98% growth inhibition, P = 0.024 versus rhualpha VEGF alone and P = 0.02 versus paclitaxel alone). Paclitaxel alone had no antiangiogenic effects at the dosage studied, whereas rhu alpha VEGF had significant inhibition of angiogenesis, noted by microvessel density and CD34 staining. rhu alpha VEGF has cytostatic clinical activity in this androgen-independent prostate cancer xenograft model, and the addition of paclitaxel demonstrates increased clinical activity.