Expression of CD133 in synovial sarcoma

The development of synovial sarcoma, a translocationally defined soft tissue tumor of unknown histogenesis with considerable resistance to systemic therapy and a poor prognosis, may involve cancer stem-like cells. Recent studies suggest that synovial sarcoma arises from a primitive progenitor-type cell and have shown that synovial sarcomas contain subpopulations with enhanced tumorigenic potential; however, little is known about cancer stem-like cells in synovial sarcoma. Histologic and gene expression studies have reported features of synovial sarcoma that are reminiscent of neural development, suggesting that a neural cancer stem-like cell marker, such as CD133, may mark cancer stem-like cells in synovial sarcoma, allowing for further characterization. Here, the immunohistochemical expression of CD133 in primary synovial sarcoma tumor tissue and synovial sarcoma cell lines is determined. Subpopulations of CD133 expressing cells are present in all primary synovial sarcomas (5/5) and synovial sarcoma cell lines (3/3) examined. Histologically, CD133 positive cells are dispersed and seem to have dendritic processes. This study demonstrates the presence of CD133 expressing cells in synovial sarcoma for the first time and validates 3 synovial sarcoma cell lines as models for further study of the CD133+ subpopulation. The relationship between CD133 expression and cancer stem-like cells suggests that CD133 expressing synovial sarcoma cells may represent cancer stem-like cells in synovial sarcoma, which has significant implications for understanding the pathogenesis of this tumor and developing effective therapies.