Project description:PAX3-FOXO1 is a fusion transcription factor that is the main driver of tumorigenesis leading to the development of alveolar rhabdomyosarcoma (aRMS). Since aRMS cells are addicted to PAX3-FOXO1 activity, the fusion protein also represents a major target for therapeutic interference, which is however challenging as transcription factors usually cannot be inhibited directly by small molecules. Hence, characterization of the biology of PAX3-FOXO1 might lead to the discovery of new possibilities for an indirect inhibition of its activity. Here, our goal was to characterize the proteomic neighborhood of PAX3-FOXO1 and to find candidates potentially affecting its activity and tumor cell viability. Towards this aim, we expressed BirA fused versions of PAX3-FOXO1 (N- and C-terminal) in HEK293T cells under presence of biotin. In the control setup, we expressed the BirA enzyme alone. After Streptavidin purification of biotinylated proteins, we performed mass spectrometry and quantified relative abundances compared to control conditions. This enabled us to determine PAX3-FOXO1 proximal proteins, which we investigated further in orthogonal endogenous systems.
Project description:PAX3-FOXO1 is a fusion transcription factor characteristic for the majority of alveolar rhabdomyosarcoma tumors. It is the main oncogenic driver and deregulates expression of PAX3 target genes. The PAX3-FOXO1 target gene signature was determined in the Rh4 alveolar rhabdomyosarcoma cell line.
Project description:Chimeric transcription factors drive lineage-specific oncogenesis but are notoriously difficult to target. Alveolar rhabdomyosarcoma (RMS) is an aggressive childhood soft tissue sarcoma transformed by the pathognomonic PAX3–FOXO1 fusion protein, which governs a core regulatory circuitry transcription factor (CRC TF) network. Here we show that the histone lysine demethylase KDM4B is a therapeutic vulnerability for PAX3–FOXO1+ RMS. Genetic and pharmacologic inhibition of KDM4B significantly delays tumor growth by disrupting the expression of CRC TFs caused by epigenetic alterations of PAX3–FOXO1-governed super enhancers. Combining KDM4B inhibition with cytotoxic chemotherapy leads to significant tumor regression in preclinical PAX3–FOXO1+ RMS models. In summary, we have identified a targetable mechanism required for maintenance of PAX3-FOXO1-related CRC TF network, which may translate to a novel therapeutic approach for fusion-positive RMS.
Project description:Chimeric transcription factors drive lineage-specific oncogenesis but are notoriously difficult to target. Alveolar rhabdomyosarcoma (RMS) is an aggressive childhood soft tissue sarcoma transformed by the pathognomonic PAX3–FOXO1 fusion protein, which governs a core regulatory circuitry transcription factor (CRC TF) network. Here we show that the histone lysine demethylase KDM4B is a therapeutic vulnerability for PAX3–FOXO1+ RMS. Genetic and pharmacologic inhibition of KDM4B significantly delays tumor growth by disrupting the expression of CRC TFs caused by epigenetic alterations of PAX3–FOXO1-governed super enhancers. Combining KDM4B inhibition with cytotoxic chemotherapy leads to significant tumor regression in preclinical PAX3–FOXO1+ RMS models. In summary, we have identified a targetable mechanism required for maintenance of PAX3-FOXO1-related CRC TF network, which may translate to a novel therapeutic approach for fusion-positive RMS.
Project description:Chimeric transcription factors drive lineage-specific oncogenesis but are notoriously difficult to target. Alveolar rhabdomyosarcoma (RMS) is an aggressive childhood soft tissue sarcoma transformed by the pathognomonic PAX3–FOXO1 fusion protein, which governs a core regulatory circuitry transcription factor (CRC TF) network. Here we show that the histone lysine demethylase KDM4B is a therapeutic vulnerability for PAX3–FOXO1+ RMS. Genetic and pharmacologic inhibition of KDM4B significantly delays tumor growth by disrupting the expression of CRC TFs caused by epigenetic alterations of PAX3–FOXO1-governed super enhancers. Combining KDM4B inhibition with cytotoxic chemotherapy leads to significant tumor regression in preclinical PAX3–FOXO1+ RMS models. In summary, we have identified a targetable mechanism required for maintenance of PAX3-FOXO1-related CRC TF network, which may translate to a novel therapeutic approach for fusion-positive RMS.
Project description:Chimeric transcription factors drive lineage-specific oncogenesis but are notoriously difficult to target. Alveolar rhabdomyosarcoma (RMS) is an aggressive childhood soft tissue sarcoma transformed by the pathognomonic PAX3–FOXO1 fusion protein, which governs a core regulatory circuitry transcription factor (CRC TF) network. Here we show that the histone lysine demethylase KDM4B is a therapeutic vulnerability for PAX3–FOXO1+ RMS. Genetic and pharmacologic inhibition of KDM4B significantly delays tumor growth by disrupting the expression of CRC TFs caused by epigenetic alterations of PAX3–FOXO1-governed super enhancers. Combining KDM4B inhibition with cytotoxic chemotherapy leads to significant tumor regression in preclinical PAX3–FOXO1+ RMS models. In summary, we have identified a targetable mechanism required for maintenance of PAX3-FOXO1-related CRC TF network, which may translate to a novel therapeutic approach for fusion-positive RMS.
Project description:Chimeric transcription factors drive lineage-specific oncogenesis but are notoriously difficult to target. Alveolar rhabdomyosarcoma (RMS) is an aggressive childhood soft tissue sarcoma transformed by the pathognomonic PAX3–FOXO1 fusion protein, which governs a core regulatory circuitry transcription factor (CRC TF) network. Here we show that the histone lysine demethylase KDM4B is a therapeutic vulnerability for PAX3–FOXO1+ RMS. Genetic and pharmacologic inhibition of KDM4B significantly delays tumor growth by disrupting the expression of CRC TFs caused by epigenetic alterations of PAX3–FOXO1-governed super enhancers. Combining KDM4B inhibition with cytotoxic chemotherapy leads to significant tumor regression in preclinical PAX3–FOXO1+ RMS models. In summary, we have identified a targetable mechanism required for maintenance of PAX3-FOXO1-related CRC TF network, which may translate to a novel therapeutic approach for fusion-positive RMS.
Project description:The tumor-specific chromosomal translocation product, PAX3::FOXO1, is an aberrant fusion protein that plays a key role for oncogenesis in the alveolar subtype of rhabdomyosarcoma (RMS). PAX3::FOXO1 represents a validated molecular target for alveolar RMS and successful inhibition of its oncogenic activity is likely to have significant clinical applications. Even though several PAX3::FOXO1 function-based screening studies have been successfully completed, a directly binding small molecule inhibitor of PAX3::FOXO1 has not been reported. Therefore, we screened small molecule libraries to identify compounds that were capable of directly binding to PAX3::FOXO1 protein using surface plasmon resonance technology. Compounds that directly bound to PAX3::FOXO1 were further evaluated in secondary transcriptional activation assays. We discovered that piperacetazine can directly bind to PAX3::FOXO1 protein and inhibit fusion protein-derived transcription in multiple alveolar RMS cell lines. Piperacetazine inhibited anchorage-independent growth of fusion positive alveolar RMS cells but not embryonal RMS cells. Based on our findings, piperacetazine is a molecular scaffold upon which derivatives could be developed as specific inhibitors of PAX3::FOXO1. These novel inhibitors could potentially be evaluated in future clinical trials for recurrent or metastatic alveolar RMS as novel targeted therapy options.
Project description:Results: Using a combination of 4C-seq datasets, we were able to model the three-dimensional organisation of the translocated chromosome in a PAX3:FOXO1 fusion-positive alveolar rhabdomyosarcoma cell line. We show that PAX3 and FOXO1 regulatory landscapes fuse into a novel TAD, allowing the PAX3 promoter to interact ectopically with FOXO1 sequences with potential enhancer function. The borders of this novel TAD correspond to the original 5'- and 3'- borders of the PAX3 and FOXO1 TADs, respectively, suggesting that TAD organisation precedes the formation of regulatory long-range interactions. Conclusions: Our results suggest that the chromosomal translocation that leads to ARMS development generates a novel TAD that favours ectopic PAX3:FOXO1 oncogene activation in non-PAX3 territories, which may be an essential step in the tumorigenic process, as expression in a particular cell type, the often elusive cell-of-origin, may be required for disease development.
Project description:To investigate the effect of PAX3-FOXO1 and B7-H3 in rhabdomyosarcoma, Rh-30 (PAX3-FOXO1 positive rhabdomyosarcoma cell line) was transfected by siPAX3-FOXO1 or siB7-H3. After knockdown, total RNA was extracted and analyzed. As a result, some genes and pathways, such as chemotaxis, differentiation, and INF-gamma production were comonnly effected by PAX3-FOXO1 and B7-H3.