SSX4

SSX4 (Synovial Sarcoma X breakpoint 4) is a transcription factor of the SSX family, with no widely established common aliases. It acts as a transcriptional repressor by associating with chromatin-modifying complexes like those containing KDM5B, regulating gene expression linked to cell proliferation and differentiation.
SSX4 is critical in synovial sarcoma, where the t(X;18) translocation forms the SS18-SSX4 fusion—an oncogenic driver. As a cancer-testis antigen, it’s a target for immunotherapies: preclinical and clinical studies explore peptide vaccines and adoptive T-cell transfer against SSX4-expressing tumors, though no specific drugs are yet approved.