Ovarian cancer has the highest mortality rate of any gynecological disease affecting women in Western countries. VEGF is a crucial inducer of angiogenesis both in vivo and in vitro. VEGF is commonly upregulated in ovarian cancer and is regulated by HIF-1. SU5416 is known to inhibit various stages of tumor growth. In this study, we show that SU5416 inhibited VEGF mRNA expression in ovarian cancer cells in a dose-dependent manner. SU5416 inhibited VEGF expression at the transcriptional level through the HIF-1 DNA binding site. HIF-1 is composed of HIF-1alpha and HIF-1beta subunits. SU5416 specifically decreased HIF-1alpha, but not HIF-1beta protein levels. To understand the signaling pathways regulating SU5416-inhibited VEGF and HIF-1alpha expression, we found that SU5416 inhibited PI3K activity. AKT is a downstream target of PI3K. We found that SU5416 also inhibited AKT and p70S6K1 activation and activity in a dose-dependent manner. These results demonstrate that SU5416 inhibited VEGF and HIF-1alpha expression through the inhibition of PI3K/AKT/p70S6K1 pathway in ovarian cancer cells. These results indicate that SU5416 may be an effective agent for ovarian cancer treatment through the inhibition of VEGF and HIF-1 expression, and the activation of PI3K/AKT/p70S6K1 signaling pathway. (C) 2004 Elsevier Inc. All rights reserved.