SDF-1 and CXCR4 are up-regulated by VEGF and contribute to glioma cell invasion

Glioma cells produce vascular endothelial growth factor (VEGF) to induce vascularization and thereby supply the malignant tissue with oxygen and nutrients. However, little is known about the direct effects of VEGF on tumor cells. In this study, we investigate the ability of VEGF to promote proliferation and invasion of human glioma cells (U251n). Since the chemokine and its receptor, SDF-1/CXCR4, promote glioma cell proliferation and are up-regulated in human glioblastomas, we also tested the effects of VEGF on SDF-1 and CXCR4 mRNA expression. Using cell culture, the effect of VEGF on proliferation of U251n cells was measured using ELISA to detect incorporated BrdU as a marker of DNA syntheses. The effects of VEGF and SDF-1 on U251n cell invasion and proliferation were measured using inhibitors to VEGF receptor1 and receptor2, DC101 and MF1 respectively, and a CXCR4 antagonist (AMD3100). SDF-1 and CXCR4 mRNA expression in U25 In and U87MG cells were measured using quantitative PCR. VEGF antisense phosphorothioate, oligodeoxynucleotide (AS-VEGF) was also used to down-regulate VEGF expression in U251n cells. VEGF significantly increased U251n cell proliferation and invasion in a dosedependent manner. These effects were blocked by the VEGF receptor inhibitors, DC101/MF1. The CXCR4 antagonist AMD3100 blocked U251n increased invasion, but not proliferation. CXCR4 and SDF-1 mRNA were up-regulated when U25 In and U87MG cells were treated with VEGF. Eight micrometer VEGF antisense phosphorothioate oligodeoxynucleotide (ASVEGF) down-regulated CXCR4 and SDF-1 mRNA levels in U251n cells. VEGF has a direct effect on U251n glioma cell proliferation and invasion. VEGF up-regulates SDF-1 and CXCR4 mRNA expression, and contributes to U25 In cell invasion. (c) 2005 Elsevier Ireland Ltd. All rights reserved.