Vanadate-induced Expression of Hypoxia-inducible Factor 1α and Vascular Endothelial Growth Factor through Phosphatidylinositol 3-Kinase/Akt Pathway and Reactive Oxygen Species

Ning Gao,Min Ding,Jenny Z Zheng,Zhuo Zhang,Stephen S Leonard,Ke Jian Liu,Xianglin Shi,Bing-Hua Jiang

doi:10.1074/jbc.m200082200

Abstract

Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic helix-loop-helix transcription factor composed of HIF-1 alpha and HIF-1 beta/aryl hydrocarbon nuclear translocator subunits. HIF-1 expression is induced by hypoxia, growth factors, and activation of oncogenes. In response to hypoxia, HIF-1 activates the expression of many genes including vascular endothelial growth factor (VEGF) and erythropoietin. HIF-1 and VEGF play an important role in angiogenesis and tumor progression. Vanadate is widely used in industry, and is a potent inducer of tumors in humans and animals. In this study, we demonstrate that vanadate induces HIF-1 activity through the expression of HIF-1alpha but not HIF-1 beta subunit, and increases VEGF expression in DU145 human prostate carcinoma cells. We also studied the signaling pathway involved in vanadate-induced HIF-1 alpha and VEGF expression and found that phosphatidylinositol 3-kinase/Akt signaling was required for HIF-1 and VEGF expression induced by vanadate, whereas mitogen-activated protein kinase pathway was not required. We also found that reactive oxygen species (ROS) were involved in vanadate-induced expression of HIF-1 and VEGF in DU145 cells. The major species of ROS responsible for the induction of HIF-1 and VEGF expression was H(2)O(2). These results suggest that the expression of HIF-1 and VEGF induced by vanadate through PI3K/Akt may be an important signaling pathway in the vanadate-induced carcinogenesis, and ROS may play an important role.

Highlights

Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic helix-loop-helix transcription factor composed of HIF-1␣ and HIF-1␤/aryl hydrocarbon nuclear translocator subunits
We studied the signaling pathway involved in vanadate-induced HIF-1␣ and vascular endothelial growth factor (VEGF) expression and found that phosphatidylinositol 3-kinase/Akt signaling was required for HIF-1 and VEGF expression induced by vanadate, whereas mitogen-activated protein kinase pathway was not required
To determine the kinetics of HIF-1␣ expression induced by vanadate, cells were treated with 100 ␮M vanadate for various times as indicated, and cellular protein extracts were prepared for analysis of HIF-1␣ and HIF-1␤ protein levels

Summary

Introduction

Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic helix-loop-helix transcription factor composed of HIF-1␣ and HIF-1␤/aryl hydrocarbon nuclear translocator subunits. We demonstrate that vanadate induces HIF-1 activity through the expression of HIF-1␣ but not HIF-1␤ subunit, and increases VEGF expression in DU145 human prostate carcinoma cells. We found that reactive oxygen species (ROS) were involved in vanadate-induced expression of HIF-1 and VEGF in DU145 cells. Inhibition of VEGF expression and of its receptor function dramatically decreases the tumor growth, invasion, and metastasis in animal models [27,28,29,30] Somatic mutations such as oncogene Ras activation and tumor suppressor gene p53 inactivation increase VEGF expression [26]. Mechanism of HIF-1 and VEGF Expression Induced by Vanadate reactive oxygen species (ROS) are considered to play an important role [44, 45]. We tested whether vanadate is able to induce the expression of HIF-1␣ and VEGF in DU145 human prostate carcinoma cells and evaluated the role of individual ROS. The following specific questions were addressed: (a) whether vanadate is able to induce HIF-1 and VEGF expression; (b) which signaling pathway(s) is/are involved in vanadate-induced expression of HIF-1␣ protein; (c) whether ROS species are involved in vanadate-induced HIF-1␣ and VEGF expression; and (d) which species of ROS play a critical role

Methods

Results

Conclusion