RESUMO
The core cohesin subunit STAG2 is recurrently mutated in Ewing sarcoma but its biological role is less clear. Here, we demonstrate that cohesin complexes containing STAG2 occupy enhancer and polycomb repressive complex (PRC2)-marked regulatory regions. Genetic suppression of STAG2 leads to a compensatory increase in cohesin-STAG1 complexes, but not in enhancer-rich regions, and results in reprogramming of cis-chromatin interactions. Strikingly, in STAG2 knockout cells the oncogenic genetic program driven by the fusion transcription factor EWS/FLI1 was highly perturbed, in part due to altered enhancer-promoter contacts. Moreover, loss of STAG2 also disrupted PRC2-mediated regulation of gene expression. Combined, these transcriptional changes converged to modulate EWS/FLI1, migratory, and neurodevelopmental programs. Finally, consistent with clinical observations, functional studies revealed that loss of STAG2 enhances the metastatic potential of Ewing sarcoma xenografts. Our findings demonstrate that STAG2 mutations can alter chromatin architecture and transcriptional programs to promote an aggressive cancer phenotype.
Assuntos
Neoplasias Ósseas/genética , Neoplasias Ósseas/patologia , Proteínas de Ciclo Celular/genética , Sarcoma de Ewing/genética , Sarcoma de Ewing/patologia , Animais , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Movimento Celular/genética , Proteínas Cromossômicas não Histona/metabolismo , Elementos Facilitadores Genéticos , Feminino , Regulação Neoplásica da Expressão Gênica , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Camundongos Endogâmicos NOD , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas de Fusão Oncogênica/genética , Fatores do Domínio POU/genética , Fatores do Domínio POU/metabolismo , Complexo Repressor Polycomb 2/genética , Complexo Repressor Polycomb 2/metabolismo , Regiões Promotoras Genéticas , Proteína Proto-Oncogênica c-fli-1/genética , Proteína EWS de Ligação a RNA/genética , Ensaios Antitumorais Modelo de Xenoenxerto , Peixe-Zebra/genética , CoesinasRESUMO
PURPOSE: Ewing sarcoma is an aggressive solid tumor malignancy of childhood. Although current treatment regimens cure approximately 70% of patients with localized disease, they are ineffective for most patients with metastases or relapse. New treatment combinations are necessary for these patients. EXPERIMENTAL DESIGN: Ewing sarcoma cells are dependent on focal adhesion kinase (FAK) for growth. To identify candidate treatment combinations for Ewing sarcoma, we performed a small-molecule library screen to identify compounds synergistic with FAK inhibitors in impairing Ewing cell growth. The activity of a top-scoring class of compounds was then validated across multiple Ewing cell lines in vitro and in multiple xenograft models of Ewing sarcoma. RESULTS: Numerous Aurora kinase inhibitors scored as synergistic with FAK inhibition in this screen. We found that Aurora kinase B inhibitors were synergistic across a larger range of concentrations than Aurora kinase A inhibitors when combined with FAK inhibitors in multiple Ewing cell lines. The combination of AZD-1152, an Aurora kinase B-selective inhibitor, and PF-562271 or VS-4718, FAK-selective inhibitors, induced apoptosis in Ewing sarcoma cells at concentrations that had minimal effects on survival when cells were treated with either drug alone. We also found that the combination significantly impaired tumor progression in multiple xenograft models of Ewing sarcoma. CONCLUSIONS: FAK and Aurora kinase B inhibitors synergistically impair Ewing sarcoma cell viability and significantly inhibit tumor progression. This study provides preclinical support for the consideration of a clinical trial testing the safety and efficacy of this combination for patients with Ewing sarcoma.