DNA binding domain-independent pathways are involved in EWS/FLI1-mediated oncogenesis

Specific chromosomal translocations involving the ews gene and one of five members of the ets family of transcription factors create ews/ets fusion ge nes that are found in similar to 85% of Ewing's family of tumors. ews/ets f usion genes consistently maintain an intact and functional ets DNA binding domain (DBD) in all of these cases. We demonstrate here, however, that EWS/ FLI1, the most prevalent EWS/ETS fusion, activates oncogenic pathways indep endent of its DBD. In in vivo tumor assays, EWS/FLI1 molecules with either point mutations or a large deletion in the ets DBD retain the ability to ac celerate tumors in NIH 3T3 cells, whereas they lose the ability to bind DNA in vitro. Additionally, whereas inhibition of DBD functions of EWS/FLI1 wi th a dominant negative form of FLI1 is sufficient to inhibit anchorage-inde pendent growth in NIH 3T3 cells, it is ineffective in inhibiting tumor grow th in SCID mice. Usage of this dominant negative construct in a Ewing's tum or cell line, however, does reduce the rate of tumor formation, supporting the need for a functional DBD in this context. Together, these results sugg est that EWS/FLI1 induces both DBD-dependent and DBD-independent oncogenic pathways.