EGFRvIII promotes glioma angiogenesis and growth through the NF-κB, interleukin-8 pathway

Sustaining a high growth rate requires tumors to exploit resources in their microenvironment. One example of this is the extensive angiogenesis that is a typical feature of high-grade gliomas. Here, we show that expression of the constitutively active mutant epidermal growth factor receptor, Delta EGFR (EGFRvIII, EGFR*, de2-7EGFR) is associated with significantly higher expression levels of the pro-angiogenic factor interleukin (IL)-8 in human glioma specimens and glioma stem cells. Furthermore, the ectopic expression of Delta EGFR in different glioma cell lines caused up to 60-fold increases in the secretion of IL-8. Xenografts of these cells exhibit increased neovascularization, which is not elicited by cells overexpressing wildtype (wt) EGFR or DEGFR with an additional kinase domain mutation. Analysis of the regulation of IL-8 by site-directed mutagenesis of its promoter showed that DEGFR regulates its expression through the transcription factors nuclear factor (NF)-kappa B, activator protein 1 (AP-1) and CCAAT/enhancer binding protein (C/EBP). Glioma cells overexpressing Delta EGFR showed constitutive activation and DNA binding of NF-kappa B, overexpression of c-Jun and activation of its upstream kinase c-Jun N-terminal kinase (JNK) and overexpression of C/EBP beta. Selective pharmacological or genetic targeting of the NF-kappa B or AP-1 pathways efficiently blocked promoter activity and secretion of IL-8. Moreover, RNA interference-mediated knock-down of either IL-8 or the NF-kappa B subunit p65, in Delta EGFR-expressing cells attenuated their ability to form tumors and to induce angiogenesis when injected subcutaneously into nude mice. On the contrary, the overexpression of IL-8 in glioma cells lacking Delta EGFR potently enhanced their tumorigenicity and produced highly vascularized tumors, suggesting the importance of this cytokine and its transcription regulators in promoting glioma angiogenesis and tumor growth. Oncogene (2012) 31, 4054-4066; doi: 10.1038/onc.2011.563; published online 5 December 2011