Project description:A series of conditional mouse models of embryonal rhabdomyosarcoma, alveolar rhabdomyosarcoma and spindle cell sarcoma were generated and validated for relavence to corresponding human cancers. Conditional mouse models of embryonal rhabdomyosarcoma, alveolar rhabdomyosarcoma and spindle cell sarcoma were created by activation or deletion of Pax3:Fkhr, p53, Ptch1 or Rb1 genes.
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: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:Background: Alveolar rhabdomyosarcoma (ARMS) has a high propensity to metastasize, leading to its aggressiveness and a poor survival rate among those with the disease. More than 80% of aggressive ARMSs harbor a PAX3-FKHR fusion transcription factor, which regulates cell migration and promotes metastasis, most likely by regulating the fusion protein's transcriptional targets. Therefore, identifying druggable transcription targets of PAX3-FKHR that are also downstream effectors of PAX3-FKHR-mediated cell migration and metastasis may lead to novel therapeutic approaches for treating ARMS. Methods: To identify genes whose expression is directly affected by the level of PAX3-FKHR in an ARMS cellular-context, we first developed an ARMS cell line in which PAX3-FKHR is stably down-regulated, and showed that stably downregulating PAX3-FKHR in ARMS cells significantly decreased the cells' motility. We used microarrays analysis to identify genes whose expression level decreased when PAX3-FKHR was downregulated. We used mutational analysis, promoter reporter assays, and electrophoretic mobility shift assays to determine whether PAX3-FKHR binds directly and specifically to the promoter region of the target gene. We used siRNA and pharmacologic inhibitor to downregulate the target gene of PAX3-FKHR and investigated the effect of such downregulation on cell motility, Results: We found that When PAX3-FKHR was downregulated, the expression of carnitine palmitoyltransferase 1A (CPT1A) decreased. We showed that PAX3-FKHR binds directly and specifically to a paired-domain binding-site in the CPT1A promoter region, indicating that CPT1A is a novel direct transcriptional target of PAX3-FKHR. Furthermore, downregulating CPT1Adecreased cell motility in ARMS cells, indicating that CPT1A is a downstream effector of PAX3-FKHR-mediated cell migration and metastasis. Conclusions: Taken together, we have identified CPT1A as a novel direct transcriptional target of PAX3-FKHR and revealed the novel function of CPT1A in promoting cell motility. CPT1A may represent a novel therapeutic target for the treatment of ARMS. Identification of transcription targets of PAX3-FKHR in human alveolar rhabdomyosarcoma: By stably knocking down PAX3-FKHR in human alveolar rhabdomyosarcoma cell line Rh30 and comparing the gene expression profile of the knockdown clone (KD) to the parental Rh30, transcription targets of PAX3-FKHR have been identified. Gene expression in parental Rh30 cells was compared to that in either Rh30 cells stably expressing shRNA targeting PAX3-FKHR (KD) or control non-targeting shRNA (CON), in duplicate.
Project description:Rhabdomyosarcoma is a soft tissue cancer that arises in skeletal muscle due to mutations in myogenic progenitors that lead to ineffective differentiation and malignant transformation. The transcription factors Pax3 and Pax7 and their down-stream target genes are tightly linked with the fusion positive alveolar subtype, whereas the RAS pathway is usually involved in the embryonic, non-fusion variant. Here, we analyse the role of Pax3 in a non-fusion context, by linking alterations in gene expression in pax3a/pax3b double mutant zebrafish with tumour progression in kRAS-induced rhabdomyosarcoma tumours. Several genes in the RAS signalling pathway, including MAPK signalling pathway, were significantly down-regulated in pax3a/pax3b double mutant zebrafish. Onset and progression of rhabdomyosarcoma tumours were also delayed in the pax3a/pax3b double mutant zebrafish indicating that Pax3 transcription factors have an unappreciated role in mediating malignancy also in non-fusion rhabdomyosarcoma.
Project description:A series of conditional mouse models of embryonal rhabdomyosarcoma, alveolar rhabdomyosarcoma and spindle cell sarcoma were generated and validated for relavence to corresponding human cancers.
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:The highly aggressive muscle cancer alveolar rhabdomyosarcoma (ARMS) is one of the most common soft tissue sarcoma of childhood, yet the outcome for unresectable and metastatic disease is dismal and unchanged for nearly 3 decades. To better understand the pathogenesis of this disease and to facilitate novel preclinical approaches, we previously developed a conditional mouse model of ARMS by faithfully recapitulating the genetic mutations observed in the human disease, i.e. activation of Pax3:Fkhr fusion gene with either p53 or Cdkn2a inactivation. In this report we show that this model recapitulates the immunohistochemical profile and the rapid progression of the human disease. We demonstrate that Pax3:Fkhr expression increases during late preneoplasia, but that tumor cells undergoing metastasis are under apparent selection for Pax3:Fkhr expression. At a whole genome level, a cross-species gene set enrichment analysis and metagene projection study showed that our mouse model is most similar to human ARMS when compared to other pediatric cancers. We have defined an expression profile conserved between mouse and human ARMS as well as a Pax3:Fkhr signature, including the target gene, SKP2. We further identified 7 “druggable” kinases over-expressed across species. The data affirms the accuracy of this genetically engineered mouse model. 6 mouse alveolar rhabdomyosarcoma tumors and 3 wild-type skeletal muscles were analyzed.