SYT-SSX fusion proteins in synovial sarcomas: detection and characterization with new antibodies.

To identify and characterize the SYT-SSX fusion proteins in synovial sarcomas, we developed two polyclonal antibodies against the N-terminal part and for the C-terminal part of the SYT-SSX2 protein. Specificity was demonstrated on COS-7 cells transfected with two subtypes of SYT-SSX fusion genes, SYT-SSX1 and SYT-SSX2. Both antibodies recognized a single protein of 61 kDa in an immunoprecipitation of the transfected COS-7 cell lysates. These antibodies also detected the native protein of 61 kDa in the lysate of a human synovial sarcoma cell line (HS-SY41) with immunoprecipitation, and in extracts of human synovial sarcomas with western blot analysis. An immunohistochemical study, using human synovial sarcoma tissues, demonstrated that the SYT-SSX fusion proteins localized in the nucleus of the tumor cells. These antibodies provide a useful method for studying the expression of the SYT-SSX fusion proteins.