Synovial sarcoma is a stem cell malignancy

Area of Science:

• Oncology
• Cancer Stem Cell Biology
• Molecular Genetics

Background:

• Synovial sarcoma (SS) is a soft tissue tumor with a characteristic t(X;18) translocation.
• The SS18-SSX fusion gene product is implicated in SS pathogenesis but its cellular origin remains unclear.

Purpose of the Study:

• To investigate the cellular origin and biological properties of human synovial sarcoma.
• To elucidate the role of the SS18-SSX fusion gene in SS development.

Main Methods:

• Establishment and characterization of two novel human SS cell lines (Yamato-SS and Aska-SS).
• Assessment of self-renewal, tumor-forming capacity, and stem cell marker expression (Oct3/4, Nanog, Sox2).
• Evaluation of differentiation potential and gene expression changes upon SS18-SSX silencing via siRNA.

Main Results:

• SS cells exhibit stem-like properties, including self-renewal and tumor formation, independent of surface markers.
• SS cells express stem cell markers and possess limited differentiation potential.
• Silencing SS18-SSX induces morphological changes, broadens differentiation capacity, and alters lineage gene expression.

Conclusions:

• Human multipotent mesenchymal stem cells are likely the cell of origin for synovial sarcoma.
• Synovial sarcoma represents a stem cell malignancy driven by SS18-SSX-mediated dysregulation of stemness and differentiation.