Expression profiling of EWS/FLI identifies NKX2.2 as a critical target gene in Ewingʹs sarcoma

Summary derstanding of Ewingʹs sarcoma development mediated by the EWS/FLI fusion protein has been limited by a lack of knowledge regarding the tumor cell of origin. To circumvent this, we analyzed the function of EWS/FLI in Ewingʹs sarcoma itself. By combining retroviral-mediated RNA interference with reexpression studies, we show that ongoing EWS/FLI expression is required for the tumorigenic phenotype of Ewingʹs sarcoma. We used this system to define the full complement of EWS/FLI-regulated genes in Ewingʹs sarcoma. Functional analysis revealed that NKX2.2 is an EWS/FLI-regulated gene that is necessary for oncogenic transformation in this tumor. Thus, we developed a highly validated transcriptional profile for the EWS/FLI fusion protein and identified a critical target gene in Ewingʹs sarcoma development.