Elevated vascular endothelial growth factor (VEGF) levels correlate with increased progression and poor prognosis of head and neck squamous cell carcinonias (HNSCC). VEGF expression is regulated by hypoxia and cytokines, including insulin-like growth factor-l (IGF-l). In this report, we examined IGF-l signaling and VEGF expression in SCC-9 cells. IGF-l and the chemical hypoxia agent, cobalt chloride, each stimulated VEGF secretion and VEGF promoter activation. Cobalt chloride increased Hif-1 alpha protein levels and HIF-l dependent activation of the enolase prorriciter. IGF-l increased these parameters only in the presence of cobalt chloride. IGF-l stimulated PI-3K/Akt and Erk/MAPK pathways in SCC-9 cells, each contributing to Hif- lot expression and VEGF secretion. SCC-9 cells express the VEGF receptors Flk-l and neuropilin-l (Np-1), with VEGF treatment increasing VEGF promoter activity and VEGF secretion that was attenuated by the Flk-l tyrosine kinase inhibitor, ZM 323881. These results demonstrate the presence of ail IGF-l regulated VEGF aUtOCrine loop in HNSCC. (c) 2006 Elsevier Inc. All rights reserved.