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Experimental CCS Models
Establishing preclinical models for clear cell sarcoma of soft tissue
Publication Date:
June 17, 2025
Abstract
Introduction: Clear cell sarcoma of soft tissue (CCSST) is a rare but aggressive soft tissue sarcoma driven by fusion proteins. The translocation of t(12;22) or t(2;22) leads to fusion formation between Ewing Sarcoma Breakpoint Region 1 (EWSR1) and either activating transcription factor 1 (ATF1) or cAMP-response element-binding protein (CREB). Several fusion types have been discovered in CCSST patients. Only type 1 EWSR1-ATF1 fusion is known to be a constitutively active transcription factor. However, the transcriptional activity of other fusion types remains unknown. In addition, there is a significant lack of preclinical in vivo metastasis models for CCSST.
Methods: We evaluated the transcriptional activity of seven EWSR1-ATF1 and one EWSR1-CREB fusion proteins using reporter assays. Migration and invasion assays were performed in CCSST cell lines. To model metastasis in vivo, CCS292 cells expressing firefly luciferase were injected intravenously into NSG mice, and metastatic spread was monitored weekly by bioluminescence imaging.
Results: We show that type 1, 2, 3 and 7 EWSR1-ATF1 fusions, as well as EWSR1-CREB are constitutively active while type 4, 5 and 6 are not. Among the four CCSST cell lines tested, only CCS292 showed invasion and migration potential, despite all lines harboring EWSR1-ATF1 fusions. CCS292 cells with firefly luciferase expression developed robust metastasis in vivo.
Conclusion: All the in-frame fusions are constitutively active. We developed both in vitro and in vivo models of CCSST metastasis based on the CCS292 cell line, which are valuable tools for assessing potential therapeutics for CCSST patients.
Author(s)
Bingbing X. Li and Jake Piesner
Modeling Clear Cell Sarcomagenesis in the Mouse: Cell of Origin Differentiation State Impacts Tumor Characteristics
Publication Date:
February 11, 2013
Abstract
Clear cell sarcoma (CCS) of tendons and aponeuroses is a deadly soft-tissue malignancy resembling melanoma, with a predilection for young adults. EWS-ATF1, the fusion product of a balanced chromosomal translocation between chromosomes 22 and 12, is considered the definitional feature of the tumor. Conditional expression of the EWS-ATF1 human cDNA in the mouse generates CCS-like tumors with 100% penetrance. Tumors, developed through varied means of initiating expression of the fusion oncogene, model human CCS morphologically, immunohistochemically, and by genome-wide expression profiling. We also demonstrate that although fusion oncogene expression in later stages of differentiation can transform mesenchymal progenitor cells and generate tumors resembling CCS generally, expression in cells retaining stem cell markers permits the full melanoma-related phenotype.
Author(s)
Krystal M. Straessler, Kevin B. Jones, Hao Hu, Huifeng Jin, Matt van de Rijn, Mario R. Capecchi
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