Abstract
Ewing sarcoma (ES) involves a tumor-specific chromosomal translocation that produces the EWS-FLI1 protein, which is required for the growth of ES cells both in vitro and in vivo. However, an EWS-FLI1-driven transgenic mouse model is not currently available. Here, we present data from six independent laboratories seeking an alternative approach to express EWS-FLI1 in different murine tissues. We used the Runx2, Col1a2.3, Col1a3.6, Prx1, CAG, Nse, NEFL, Dermo1, P0, Sox9 and Osterix promoters to target EWS-FLI1 or Cre expression. Additional approaches included the induction of an endogenous chromosomal translocation, in utero knock-in, and the injection of Cre-expressing adenovirus to induce EWS-FLI1 expression locally in multiple lineages. Most models resulted in embryonic lethality or developmental defects. EWS-FLI1-induced apoptosis, promoter leakiness, the lack of potential cofactors, and the difficulty of expressing EWS-FLI1 in specific sites were considered the primary reasons for the failed attempts to create a transgenic mouse model of ES.
Highlights
Ewing sarcoma (ES) is a highly malignant tumor of bone and soft tissue that occurs in children, adolescents, and young adults
EWS-FLI1 is required to maintain the growth of ES cell lines, and when the expression level of EWS-FLI1 is reduced by alternative mechanisms, ES cell lines die in culture and xenografts in nude mice regress [6,7,8,9,10,11,12,13]
As untranslated transcripts of the Gt(ROSA)26Sor locus are expressed at high levels in the epididymis and the testis, we evaluated whether the EWS-FLI1/luciferase transcript might be expressed from the Gt(ROSA)26Sor promoter
Summary
Ewing sarcoma (ES) is a highly malignant tumor of bone and soft tissue that occurs in children, adolescents, and young adults. ES cases show a balanced chromosomal translocation [4] that joins the EWS gene (EWing Sarcoma) located on chromosome 22 to an ETS family gene, which is most commonly either FLI1 (Friend Leukemia Insertion) located on chromosome 11, t(11;22) or ERG located on chromosome 21, t(21;22). FLI1 is an ETS family transcription factor with a conserved DNA binding domain. The carboxy terminal half of FLI1 contained in the EWS-FLI1 fusion protein retains its DNA binding domain. EWS-FLI1 binds to DNA through the conserved ETS binding domain. The EWS-FLI1 fusion protein functions by a different mechanism than either EWS or FLI1 [5]. EWS-FLI1 is required to maintain the growth of ES cell lines, and when the expression level of EWS-FLI1 is reduced by alternative mechanisms, ES cell lines die in culture and xenografts in nude mice regress [6,7,8,9,10,11,12,13]
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