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EWS/ETS fusion genes induce epithelial and neuroectodermal differentiation in NIH 3T3 fibroblasts
M A Teitell1, A D Thompson, P H Sorensen
1Department of Pathology, Jonsson Comprehensive Cancer Center, University of California at Los Angeles, USA. mteitell@ucla.edu
Abstract:
Ewing's sarcoma is the least differentiated member of the peripheral primitive neuroectodermal (pPNET) tumor family. Chromosomal translocations involving the EWS gene and five different Ets family transcription factor genes create fusion genes encoding aberrant transcription factors and are implicated in the vast majority of Ewing's sarcoma cases. Here, NIH 3T3 fibroblasts were infected with control (tk-neo or RAS) and two different EWS/ETS-expressing retroviruses. In vitro studies of established polyclonal lines expressing the two EWS/ETS genes, either EWS/FLI1 or EWS/ETV1, showed induction of cytokeratin 15 gene expression. Both fusion genes also caused characteristic gross morphologic, histologic, and ultrastructural changes in NIH 3T3 cells when transformed cell lines were injected into CB-17-scid mice. Native NIH 3T3 cells with a spindled cell morphology were converted to polygonal cells with high nucleo-cytoplasmic ratios that continued to express abundant cytokeratin. Extracellular collagen deposition was abolished, rough endoplasmic reticulum was markedly diminished, and rudimentary cell-cell attachments appeared. Most strikingly, neurosecretory-type dense core granules like those seen in pPNET were now evident. This murine model, created in mesenchyme-derived NIH 3T3 cells, demonstrated new characteristics of both neuroectodermal and epithelial differentiation and resembled small round cell tumors microscopically.
Insights
Ewing sarcoma research reveals that EWS/ETS fusion genes induce neuroectodermal and epithelial differentiation in NIH 3T3 fibroblasts. This creates a murine model resembling small round cell tumors for further study.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Ewing sarcoma is a primitive neuroectodermal tumor characterized by EWS gene translocations.
- These translocations create fusion genes encoding aberrant transcription factors, driving tumorigenesis.
Purpose of the Study:
- To investigate the in vitro and in vivo effects of EWS/ETS fusion genes.
- To establish a murine model for studying Ewing sarcoma differentiation.
Main Methods:
- NIH 3T3 fibroblasts were infected with retroviruses expressing EWS/FLI1 or EWS/ETV1 fusion genes.
- In vitro analysis included gene expression (cytokeratin 15) and cell morphology.
- In vivo studies involved injecting transformed cells into CB-17-scid mice.
Main Results:
- EWS/FLI1 and EWS/ETV1 expression induced cytokeratin 15.
- Transformed NIH 3T3 cells exhibited altered morphology, reduced collagen, and diminished endoplasmic reticulum.
- Neurosecretory-type dense core granules, characteristic of primitive neuroectodermal tumors, were observed.
Conclusions:
- EWS/ETS fusion genes can induce both neuroectodermal and epithelial differentiation in mesenchymal cells.
- The developed murine model recapitulates key features of small round cell tumors, offering a valuable tool for Ewing sarcoma research.