ABSTRACT
Ewing sarcoma is an aggressive pediatric small round cell tumor that predominantly occurs in bone. Approximately 85% of Ewing sarcomas harbor the EWS/FLI fusion protein, which arises from a chromosomal translocation, t(11:22)(q24:q12). EWS/FLI interacts with numerous lineage-essential transcription factors to maintain mesenchymal progenitors in an undifferentiated state. We previously showed that EWS/FLI binds the osteogenic transcription factor RUNX2 and prevents osteoblast differentiation. In this study, we investigated the role of another Runt-domain protein, RUNX3, in Ewing sarcoma. RUNX3 participates in mesenchymal-derived bone formation and is a context dependent tumor suppressor and oncogene. RUNX3 was detected in all Ewing sarcoma cells examined, whereas RUNX2 was detected in only 73% of specimens. Like RUNX2, RUNX3 binds to EWS/FLI via its Runt domain. EWS/FLI prevented RUNX3 from activating the transcription of a RUNX-responsive reporter, p6OSE2. Stable suppression of RUNX3 expression in the Ewing sarcoma cell line A673 delayed colony growth in anchorage independent soft agar assays and reversed expression of EWS/FLI-responsive genes. These results demonstrate an important role for RUNX3 in Ewing sarcoma.
Subject(s)
Core Binding Factor Alpha 3 Subunit/biosynthesis , Neoplasms, Bone Tissue/genetics , Oncogene Proteins, Fusion/metabolism , Proto-Oncogene Protein c-fli-1/metabolism , RNA-Binding Protein EWS/metabolism , Sarcoma, Ewing/genetics , Cell Differentiation/genetics , Cell Line, Tumor , Core Binding Factor Alpha 3 Subunit/genetics , Gene Expression Regulation, Neoplastic , Humans , Neoplasms, Bone Tissue/pathology , Oncogene Proteins, Fusion/genetics , Proto-Oncogene Protein c-fli-1/genetics , RNA-Binding Protein EWS/genetics , Sarcoma, Ewing/pathologyABSTRACT
Biphenotypic sinonasal sarcoma (SNS) is a newly described tumor of the nasal and paranasal areas. Here we report a recurrent chromosomal translocation in SNS, t(2;4)(q35;q31.1), resulting in a PAX3-MAML3 fusion protein that is a potent transcriptional activator of PAX3 response elements. The SNS phenotype is characterized by aberrant expression of genes involved in neuroectodermal and myogenic differentiation, closely simulating the developmental roles of PAX3.
Subject(s)
DNA-Binding Proteins/genetics , Gene Expression Regulation, Developmental , Gene Fusion/genetics , Nose Neoplasms/genetics , Nuclear Proteins/genetics , Oncogene Proteins, Fusion/genetics , Paired Box Transcription Factors/genetics , Paranasal Sinus Neoplasms/genetics , Transcription Factors/genetics , Chromosomes, Human, Pair 2/genetics , Chromosomes, Human, Pair 4/genetics , Humans , Molecular Sequence Data , Muscle Development/genetics , Neuroectodermal Tumors/genetics , Neuroectodermal Tumors/pathology , Nose Neoplasms/pathology , PAX3 Transcription Factor , Paranasal Sinus Neoplasms/pathology , Phenotype , Response Elements/genetics , Trans-Activators , Translocation, Genetic/geneticsABSTRACT
Runx2 and Axin2 regulate craniofacial development and skeletal maintenance. Runx2 is essential for calvarial bone development, as Runx2 haploinsufficiency causes cleidocranial dysplasia. In contrast, Axin2-deficient mice develop craniosynostosis because of high ß-catenin activity. Axin2 levels are elevated in Runx2(-/-) calvarial cells, and Runx2 represses transcription of Axin2 mRNA, suggesting a direct relationship between these factors in vivo. Here we demonstrate that Runx2 binds several regions of the Axin2 promoter and that Runx2-mediated repression of Axin2 transcription depends on Hdac3. To determine whether Runx2 contributes to the etiology of Axin2 deficiency-induced craniosynostosis, we generated Axin2(-/-):Runx2(+/-) mice. These double mutant mice had longer skulls than Axin2(-/-) mice, indicating that Runx2 haploinsufficiency rescued the craniosynostosis phenotype of Axin2(-/-) mice. Together, these studies identify a key mechanistic pathway for regulating intramembranous bone development within the skull that involves Runx2- and Hdac3-mediated suppression of Axin2 to prevent the untimely closure of the calvarial sutures.
