The EWS protein is dispensable for ewing tumor growth

EWS encodes a ubiquitously expressed RNA binding protein with largely unkno wn function. In Ewing sarcoma family tumors (EFT), one allele is rearranged with an ETS gene. This is the first description of an EFT with a complete EWS deficiency in the presence of two copies of a rearranged chromosome 22 carrying an interstitial EWS-FLI1 translocation. Absence of EWS protein sug gested that it is dispensable for EFT growth. By sequencing of EWS cDNA fro m unrelated EFTs, we excluded inactivation of EWS as a general mechanism in EFT pathogenesis. Rather, EWS was found to be uniformly expressed in two s plicing variants of similar abundancy, EWS alpha and EWS beta, which differ in a single amino acid. Three EWS negative cell lines were established, wh ich will serve as valuable models to study normal and aberrant EWS function upon reintroduction into the tumor cells.