EPN-13EPITHELIAL-TO-MESENCHYMAL TRANSITIONS IN CHILDHOOD EPENDYMOMAS MECHANISTICALLY LINKS ONCOGENIC C11orf95-RELA FUSION DRIVEN ACTIVATION OF SNAI1/SNAIL

BACKGROUND: Childhood ependymomas are enigmatic tumors and their clinical management remains elusive. Oncogenic gene fusion between C11orf95 and RELA leads to the activation of NF-kB pathway in supratentorial ependymomas. Increased NF-κB levels have been linked with induction of epithelial-mesenchymal transitions(EMTs). Snail/SNAI1 is cardinal EMT causing transcription factor which negatively regulates E-cadherin/CDH1, resulting in activation of EMT phenotype. We hypothesized C11orf95-RELA driven activation of NF-kB pathway may be involved in activation of EMT via Snail. METHODS:RELA fusions were examined using sanger sequencing. Gene expression analysis for NF-kB pathways were performed using published dataset of ependymomas (GSE21687 and GSE66354). Immunohistochemistry for E-cadherin, N-Cadherin, Snail and MIB1 was performed on 40 childhood ependymoma cases. ChIP assay was used to measure the binding of NF-kB/RelA at SNAI1 promoters (in-vivo). RESULTS:75%(18/24) cases of supratentorial tumors showed C11orf95-RELA fusion transcripts. Gene expression analysis confirmed up-regulation of NF-kB pathway with more than 50% of regulators to be overexpressed in supratentorial location. Immunohistochemistry for EMT factors revealed immunopositivity of E-Cadherin(2%), N-Cadherin(76.6%) and Snail(80%) in ependymomas. Significant correlation was observed between C11orf95-RELA fusion, Snail and MIB1(LI > 10). ChIP assay confirmed the binding of NF-kB at SNAI1 promoter. Survival analysis showed presence of C11orf95-RELA fusion(p = 0.03) and Snail(p = 0.041) to be significantly associated with poor prognostic. CONCLUSION: We provide compelling evidence showing that Snail is a direct target of NF-kB/RELA, causing activation of EMT-like state in childhood ependymomas. Our findings offer new insight in the downstream regulation of the C11orf95-RELA fusions and provide a molecular basis for potential targeted therapies of childhood ependymomas.