Abstract 444: Hypoxia modulates EWS-FLI1 transcriptional signature and enhances invasiveness and anchorage-independent growth of Ewing's sarcoma cells in-vitro

Abstract

Abstract Hypoxia is an important factor in the tumor cell microenvironment and approximately 1-1.5% of the genome is transcriptionally responsive to hypoxia. Hypoxia-inducible factor-1 (HIF-1) is the major mediator of transcriptional activation under hypoxia. Tumor hypoxia is associated with a more aggressive phenotype of many cancers in adults, but data on pediatric tumors are scarce. By immunohistochemistry, HIF-1α expression was readily detectable in 18/28 primary Ewing′s sarcoma family tumors (ESFT), a group of highly malignant bone-associated tumors in children and young adults, hence we studied the effect of hypoxia on ESFT cell lines in-vitro. Intriguingly, we found that EWS-FLI1 protein expression, which characterizes ESFT, is transiently up-regulated by hypoxia in a HIF-1α-dependent manner. Hypoxia modulated the EWS-FLI1 transcriptional signature relative to normoxic conditions. Both synergistic as well as antagonistic transcriptional effects of EWS-FLI1 and of hypoxia were observed. Consistent with alterations in the expression of metastasis related genes, hypoxia stimulated the invasiveness and soft-agar colony formation of ESFT cells in-vitro. Our data represents the first transcriptome analysis of hypoxic ESFT cells and identifies hypoxia as an important microenvironmental factor modulating EWS-FLI1 expression and target gene activity that may impact the malignant properties of ESFT. This study was funded by: “European Embryonal Tumor Pipeline” 6th framework program of the European Commission (STREP “E.E.T. Pipeline” contract LSHC-CT-2006-037260) and grant 12675 from the Austrian National Bank Jubilaeumsfonds. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 444.