EWS-FLI-1 and EWS-ERG chimeric mRNAs in Ewing's sarcoma and primitive neuroectodermal tumor

The t(11;22)(q24;q12) and t(21;22)(q22;q12) are specific chromosomal translocations found in the Ewing family of tumors including ES, PNET and Askin tumors. In these translocations, the amino-terminal portion of the EWS gene located in 22q12 fuses to the carboxyl-terminal portion of the FLI-1 gene located in 11q24 or the ERG gene located in 21q22, which belong to the ets oncogene superfamily of transcription activators. We investigated the chimeric mRNAs of 15 ESs (7 cell lines and 8 tumor samples) and 7 PNETs (3 cell lines and 4 tumor samples) using the RT-PCR method and sequencing. We detected 2 types of EWS-ERG chimeric mRNA in 2 ES cell lines and 1 PNET tumor sample in addition to 4 types of EWS-FLI-1 chimeric mRNA in 11 ESs (4 cell lines and 7 tumor samples) and 4 PNETs (2 cell lines and 2 tumor samples). There seemed to be no association between the type of chimeric mRNA and clinical features such as sex, age, primary site and histopathology of the patients. All of the chimeric mRNAs are generated from in-frame junctions and are thought to encode fusion proteins that may be the molecular mechanism involved in the Ewing family of tumors.