Abstract
The oncogene HDM2 has been implicated in the regulation of the transcription factor, hypoxia inducible factor (HIF). We show in von Hippel-Lindau (VHL)-defective renal carcinoma cells that express constitutively high levels of HIF-1 alpha and HIF-2 alpha that down-regulation of HDM2 by siRNA leads to decreased levels of both HIF-1 alpha and HIF-2 alpha protein levels. However, we show a differential regulation of HDM2 on the HIF angiogenic targets, vascular endothelial growth factor (VEGF), plasminogen activator inhibitor-1 (PAI-1), and endothelin-1 (ET-1): siRNA to HDM2 leads to increased expression of VEGF and PAI-1 proteins but decreased levels of ET-1. We show that HDM2-mediated regulation of these proteins is independent of VHL and p53 but dependent on a novel action of HDM2. Ablation of HDM2 leads to phosphorylation of extracellular-regulated kinase (ERK)1/2 in renal carcinoma cells. We show that regulation of these angiogenic factors is dependent on ERK1/2 phosphorylation, which can be reversed by addition of the MAP/ERK1/2 kinase inhibitors PD98059 and PD184352. This study identifies a novel role for the HDM2 oncoprotein in the regulation of angiogenic factors in renal cell carcinoma.