Project description:Synovial sarcoma is an aggressive soft-tissue malignancy that is characterized by a pathognomonic t(X;18)(p11.2;q11.2) translocation, which produces the fusion oncogene namedSS18::SSX. Despite recent advancements in our understanding of synovial sarcoma biology, the cell-of-origin remains undefined. A mesenchymal stromal cell (MSC) specific CreERT2 line was employed to expressSS18::SSXin fibroblasts and related cell types, resulting in 100% penetrant synovial sarcoma development in mice, with a median latency period of 16.2 ± 2.5 weeks. Murine tumours exhibited high concordance with human synovial sarcoma sub-types at the histological and molecular levels1. Genetic refinement of the cell-of-origin revealed that synovial sarcomas derive from a rareHic1+Pdgfra+Lgr5+fibroblastic population. Furthermore, longitudinal multi-omic profiling along the transformation continuum revealed the step-wise acquisition of a transformed phenotype initiated by the loss of a mature fibroblastic profile and subsequently, the gradual unmasking of an epigenetically embedded embryonic MSC program. Adult and embryonic MSCs exhibited overlapping H2AK119ub and H3K4me3/H3K27me3 (bivalent) histone marks, while SS18::SSX-mediated transformation culminated in the widespread loss of H3K27me3 at these genes and their consequent transcription. Collectively, these studies define a rare MSC context, conducive for SS18::SSX-mediated transformation, and demonstrate that SS tumorigenesis involves the induction and maintenance of an embryonic-like MSC phenotype.
Project description:Synovial sarcoma is an aggressive soft-tissue malignancy that is characterized by a pathognomonic t(X;18)(p11.2;q11.2) translocation, which produces the fusion oncogene namedSS18::SSX. Despite recent advancements in our understanding of synovial sarcoma biology, the cell-of-origin remains undefined. A mesenchymal stromal cell (MSC) specific CreERT2 line was employed to expressSS18::SSXin fibroblasts and related cell types, resulting in 100% penetrant synovial sarcoma development in mice, with a median latency period of 16.2 ± 2.5 weeks. Murine tumours exhibited high concordance with human synovial sarcoma sub-types at the histological and molecular levels1. Genetic refinement of the cell-of-origin revealed that synovial sarcomas derive from a rareHic1+Pdgfra+Lgr5+fibroblastic population. Furthermore, longitudinal multi-omic profiling along the transformation continuum revealed the step-wise acquisition of a transformed phenotype initiated by the loss of a mature fibroblastic profile and subsequently, the gradual unmasking of an epigenetically embedded embryonic MSC program. Adult and embryonic MSCs exhibited overlapping H2AK119ub and H3K4me3/H3K27me3 (bivalent) histone marks, while SS18::SSX-mediated transformation culminated in the widespread loss of H3K27me3 at these genes and their consequent transcription. Collectively, these studies define a rare MSC context, conducive for SS18::SSX-mediated transformation, and demonstrate that SS tumorigenesis involves the induction and maintenance of an embryonic-like MSC phenotype.
Project description:Synovial sarcoma (SyS) is an aggressive soft-tissue malignancy that is characterized by a pathognomonic t(X;18)(p11.2;q11.2) translocation, which produces the fusion oncogene named SS18::SSX. Despite recent advancements in our understanding of synovial sarcoma biology, the cell-of-origin remains undefined. Here we employ a mesenchymal stromal cell (MSC) specific CreERT2 line to express SS18::SSX in fibroblasts and related cell types, resulting in 100% penetrant synovial sarcoma development in mice, with a median latency period of 16.2 ± 2.8 weeks. Murine tumours exhibit high concordance with human synovial sarcoma subtypes at the histological and molecular levels1. Genetic refinement of the cell-of-origin reveal that synovial sarcomas derive from a rare Hic1+ Pdgfra+ Lgr5+ fibroblastic population. Furthermore, comparative transcriptomic analysis reveals the acquisition of a transformed phenotype initiated by the loss of a mature fibroblastic profile and subsequent unmasking of an epigenetically embedded embryonic MSC program. Adult and embryonic MSCs exhibite overlapping H2AK119ub and H3K4me3/H3K27me3 (bivalent) histone marks, while SS18::SSX-mediated transformation culminates in the widespread loss of H3K27me3 at these genes and their consequent transcription. Collectively, these studies define a rare MSC context, conducive for SS18::SSX-mediated transformation, and demonstrate that SyS tumorigenesis involves the induction and maintenance of an embryonic-like MSC phenotype.
Project description:Synovial sarcoma (SyS) is an aggressive soft-tissue malignancy that is characterized by a pathognomonic t(X;18)(p11.2;q11.2) translocation, which produces the fusion oncogene named SS18::SSX. Despite recent advancements in our understanding of synovial sarcoma biology, the cell-of-origin remains undefined. Here we employ a mesenchymal stromal cell (MSC) specific CreERT2 line to express SS18::SSX in fibroblasts and related cell types, resulting in 100% penetrant synovial sarcoma development in mice, with a median latency period of 16.2 ± 2.8 weeks. Murine tumours exhibit high concordance with human synovial sarcoma subtypes at the histological and molecular levels1. Genetic refinement of the cell-of-origin reveal that synovial sarcomas derive from a rare Hic1+ Pdgfra+ Lgr5+ fibroblastic population. Furthermore, comparative transcriptomic analysis reveals the acquisition of a transformed phenotype initiated by the loss of a mature fibroblastic profile and subsequent unmasking of an epigenetically embedded embryonic MSC program. Adult and embryonic MSCs exhibite overlapping H2AK119ub and H3K4me3/H3K27me3 (bivalent) histone marks, while SS18::SSX-mediated transformation culminates in the widespread loss of H3K27me3 at these genes and their consequent transcription. Collectively, these studies define a rare MSC context, conducive for SS18::SSX-mediated transformation, and demonstrate that SyS tumorigenesis involves the induction and maintenance of an embryonic-like MSC phenotype.
Project description:Synovial Sarcoma (SS) is driven by the SS18::SSX fusion oncoprotein and is ultimately refractory to therapeutic approaches. SS18::SSX alters ATP-dependent chromatin remodeling BAF (mammalian SWI/SNF) complexes, leading to the degradation of canonical (cBAF) complex and amplified presence of an SS18::SSX-containing non-canonical BAF (ncBAF or GBAF) that drives an SS-specific transcription program and tumorigenesis. We demonstrate that SS18::SSX activates the SUMOylation program and SSs are sensitive to the small molecule SAE1/2 inhibitor, TAK-981. Mechanistically, TAK-981 de-SUMOylates the cBAF/PBAF component, SMARCE1, stabilizing and restoring cBAF on chromatin, shifting away from SS18::SSX-driven transcription, resulting in DNA damage, cell death and tumor inhibition across both human and mouse SS tumor models. TAK-981 synergized with cytotoxic chemotherapy through increased DNA damage, leading to tumor regression. Targeting the SUMOylation pathway in SS restores cBAF complexes and blocks the SS18::SSX transcriptome, identifying a therapeutic vulnerability in SS.
Project description:We analyzed the effects of cellular context on the function of the synovial sarcoma-specific fusion protein, SS18-SSX, using human pluripotent stem cells containing the drug-inducible SS18-SSX gene. To investigate the cell-type-dependent effecfts of SS18-SSX, we performed gene expression profiling experiments. Comparison of global gene expressions of hPSCs, hPSC-NCCs, and hPSC-MSCs with or without the inductuion of SS18-SSX2