EWSR1 and Ewing sarcoma: To test this hypothesis, we evaluated the levels of the oncogenic fusion proteins EWS-FLI1 and PAX3-FOXO1, which are required for the proliferation of Ewing sarcoma and alveolar rhabdomyosarcoma cell lines, respectively.29, 30 Protein levels of EWS-FLI in EW8 cells and PAX3-FOXO1 in Rh41 cells were reduced by Sgt1 depletion or ganetespib (an Hsp90 inhibitor) treatment (Figures 4a and b).