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Updated: May 22, 2026
LINE-1 Methylation Analysis in Mesenchymal Stem Cells Treated with Osteosarcoma-Derived Extracellular Vesicles
Published on: February 1, 2020
Myxoid liposarcoma-associated EWSR1-DDIT3 selectively represses osteoblastic and chondrocytic transcription in
Kayo Suzuki1, Yoshito Matsui, Mami Higashimoto
1Department of Orthopaedic Surgery, Faculty of Medicine, University of Toyama, Toyama, Japan.
Background:
Liposarcomas are the most common class of soft tissue sarcomas, and myxoid liposarcoma is the second most common liposarcoma. EWSR1-DDIT3 is a chimeric fusion protein generated by the myxoid liposarcoma-specific chromosomal translocation t(12;22)(q13;q12). Current studies indicate that multipotent mesenchymal cells are the origin of sarcomas. The mechanism whereby EWSR1-DDIT3 contributes to the phenotypic selection of target cells during oncogenic transformation remains to be elucidated.
Methodology/Principal Findings:
Reporter assays showed that the EWSR1-DDIT3 myxoid liposarcoma fusion protein, but not its wild-type counterparts EWSR1 and DDIT3, selectively repressed the transcriptional activity of cell lineage-specific marker genes in multipotent mesenchymal C3H10T1/2 cells. Specifically, the osteoblastic marker Opn promoter and chondrocytic marker Col11a2 promoter were repressed, while the adipocytic marker Ppar-γ2 promoter was not affected. Mutation analyses, transient ChIP assays, and treatment of cells with trichostatin A (a potent inhibitor of histone deacetylases) or 5-Aza-2'-deoxycytidine (a methylation-resistant cytosine homolog) revealed the possible molecular mechanisms underlying the above-mentioned selective transcriptional repression. The first is a genetic action of the EWSR1-DDIT3 fusion protein, which results in binding to the functional C/EBP site within Opn and Col11a2 promoters through interaction of its DNA-binding domain and subsequent interference with endogenous C/EBPβ function. Another possible mechanism is an epigenetic action of EWSR1-DDIT3, which enhances histone deacetylation, DNA methylation, and histone H3K9 trimethylation at the transcriptional repression site. We hypothesize that EWSR1-DDIT3-mediated transcriptional regulation may modulate the target cell lineage through target gene-specific genetic and epigenetic conversions.
Conclusions/Significance:
This study elucidates the molecular mechanisms underlying EWSR1-DDIT3 fusion protein-mediated phenotypic selection of putative target multipotent mesenchymal cells during myxoid liposarcoma development. A better understanding of this process is fundamental to the elucidation of possible direct lineage reprogramming in oncogenic sarcoma transformation mediated by fusion proteins.
Insights
The EWSR1-DDIT3 fusion protein in myxoid liposarcoma selectively represses specific cell lineage genes through genetic and epigenetic mechanisms. This study clarifies how this fusion protein drives oncogenic transformation by altering target cell phenotypes.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Myxoid liposarcoma is a common soft tissue sarcoma.
- The EWSR1-DDIT3 fusion protein, resulting from a specific translocation, is implicated in its development.
- The precise role of EWSR1-DDIT3 in selecting target cells for oncogenic transformation is not fully understood.
Purpose of the Study:
- To elucidate the molecular mechanisms by which the EWSR1-DDIT3 fusion protein mediates phenotypic selection of multipotent mesenchymal cells.
- To investigate the genetic and epigenetic actions of EWSR1-DDIT3 in the context of myxoid liposarcoma.
Main Methods:
- Reporter assays were used to assess the transcriptional activity of cell lineage-specific marker genes.
- Mutation analyses and ChIP assays were performed to understand protein-DNA interactions.
- Cells were treated with histone deacetylase inhibitors and DNA methylation inhibitors to explore epigenetic modifications.
Main Results:
- EWSR1-DDIT3 selectively repressed osteoblastic (Opn) and chondrocytic (Col11a2) promoters but not the adipocytic (Ppar-γ2) promoter in mesenchymal cells.
- Genetic mechanisms involve EWSR1-DDIT3 binding to C/EBP sites and interfering with C/EBPβ function.
- Epigenetic mechanisms include enhanced histone deacetylation, DNA methylation, and H3K9 trimethylation.
Conclusions:
- The study elucidates the genetic and epigenetic mechanisms of EWSR1-DDIT3 in phenotypic selection during myxoid liposarcoma development.
- Understanding these mechanisms is crucial for comprehending lineage reprogramming in sarcoma transformation mediated by fusion proteins.
