SS18-SSX [MD234R]

SS18 protein is a part of the SWI/SNF complex. The SS18-SSX fusion oncoprotein is a result of in-frame fusions that fuse the SS18 gene on chromosome 18 with SSX1, SSX2, and SSX4 on X chromosome gene. Human synovial sarcoma (SS) accounts for 8-10% of all soft tissue malignancies and 95% of these malignancies express the recurrent translocation of the SS18 gene on chromosome 18. IHC is routinely used in differential diagnosis because the diagnosis of synovial sarcoma is challenging due to histologic overlap with a range of other tumors. The N-terminal SNH domain of the SS18 interacts with BAF (mSWI/SNF) chromatin remodeling complexes via the N terminal region of BRM and BRG1 subunits. Endogenous SS18 competes with the mutant SS18-SSX fusion for occupancy in the SWI/SNF complexes resulting in the displacement of BAF47 (SNF5) subunit which results in altered function of the SWI/SNF complex thus to deregulated expression of genes such as Sox2 in SS.