Identification of target genes in their native cellular context: an analysis of EWS/FLI in Ewing's sarcoma.

Ewing's sarcoma is the second most common tumor of bone in children and young adults, and requires highly intensive chemotherapy along with surgery and/or radiation for successful treatment. Because these therapies are associated with significant short- and long-term side effects, new therapeutic approaches are needed. Most cases of Ewing's sarcoma contain somatic translocations between chromosomes 11 and 22 that result in the t(11;22)(q24;q12). This translocation encodes the EWS/FLI fusion protein. EWS/FLI formation appears to be the critical oncogenic event in the development of Ewing's sarcoma. It is hoped that an in-depth understanding of the mechanism that EWS/FLI uses to cause oncogenic transformation will result in new therapies for this disease. Unfortunately, this hope has not been realized. One difficulty has been the lack of an appropriate model system in which to study the fusion oncoprotein. We recently described and validated the use of retroviral RNA interference approaches to study EWS/FLI in Ewing's sarcoma cell lines. We now put this model into a historical context, and describe the benefits (both perceived and observed) of this model over previous approaches using heterologous cell types.