Function and targeting of a 5hmC-methylosome complex in synovial sarcoma

Synovial sarcoma is a deadly form of malignant soft tissue tumors, most commonly affecting children and young adults. Approximately all the patients bear a pathognomonic chromosomal translocation, t(X;18), which fuses the SS18 gene with SSX1, SSX2, or SSX4. The resulting SS18-SSX fusion oncoprotein has been proven to function as a central driver of synovial sarcoma. The known mechanisms of its action primarily depend on aberrant transcriptional regulation that involves both upregulation and downregulation of target gene expression. Over the past decade, it has become increasingly clear that chromatin modifying molecules and their catalyzed histone modifications play important functions in SS18-SSX-mediated synovial sarcomagenesis. However, the biological role of DNA modifications in this process remains much less understood. Our proposed work will focus on 5-hydroxymethylcytosine (5hmC) DNA modification, an epigenetic mark involved in normal development and frequently misregulated in human cancers, to test the overarching hypothesis that perturbation of 5hmC signaling pathways contributes to synovial sarcoma formation. Using newly developed cell models along with functional genomics and proteomics analyses, we will (1) analyze the genomic interaction between SS18-SSX fusion and 5hmC DNA, (2) examine the epigenetic mechanism of 5hmC gene regulation by SS18-SSX, and (3) identify clinically applicable compounds that can directly interrupt the SS18-SSX/5hmC connection to inhibit synovial sarcoma growth. The successful completion of this proposal will collectively yield novel insights into synovial sarcoma biology through previously uncharacterized 5hmC signaling and translate this knowledge into new therapeutic options for managing this devastating disease.