Synovial sarcoma is a gateway to the role of chromatin remodeling in cancer

Stefan K. Zöllner, Claudia Rössig, Jeffrey A. Toretsky

Patients afflicted with synovial sarcoma share the fate of other translocation positive sarcomas; the driver mutation for this cancer is known, yet no means to target the fusion protein SS18-SSX directly exist. Current chemotherapeutic regimens are minimally beneficial, particularly in patients with metastatic disease. SS18-SSX putatively promotes its oncogenic activity through protein-protein interactions that alter genetic programs through chromatin remodeling. This review discusses the functional protein network of SS18-SSX, both wild-type and fusion protein, considers its intrinsically disordered nature, and provides insights into potential therapeutic strategies. A comprehensive overview of the clinical characteristics reveals the need for newly targeted therapeutics based upon oncogenic transformation by the fusion protein SS18-SSX. The wild-type, non-fused proteins SS18 and SSX are presented including their molecular structure and biological function with regard to protein-protein interactions. The interactions of the wild-type proteins inform the oncogenic changes of the fusion protein. The SS18-SSX fusion protein and its protein interactions are described and evaluated for their biological consequences that lead to oncogenesis. This review illustrates the key protein interactions of SS18-SSX that may qualify as primary targets for small molecule-based disruption leading to the development of SS18-SSX-specific drugs. These novel targeted therapeutics may provide a specificity that ultimately improves survival while reducing morbidity of patients with synovial sarcoma.