NF-κB Subunits p50 and RelA Contribute to Oncogenesis in a Mouse Model of ST-EPN

The NF- κB pathway has been demonstrated to be upregulated in supratentorial ependymoma (ST-EPN). Whether the different NF- κB transcription factors contribute to ST-EPN tumorigenesis however, has not been investigated. We assessed the degree to which NF- κB subunits p50 and RelA interact with the ST-EPN fusion mutation C11orf95-RELA in regulating gene expression via colocalization analysis in Hek293T cell nuclei. We analyzed the functional outcomes of overexpression of p50 or RelA, or CRISPR/Cas9-mediated knockdown of p50, in combination with the C11orf95-RELA fusion in vivo by examination of tumor area in P14 – 21 CD1 mice. We further analyzed the effects each of these conditions have on transformed cell morphology using immunohistochemistry and microscopy. Our results show that the C11orf95-RELA fusion and RelA more significantly colocalize with the C11orf95-RELA fusion than does p50 in Hek293T cell nuclei. Overexpression of RelA in combination with the C11orf95-RELA fusion generates larger tumors by P21, while CRISPR knockdown of p50 in neural progenitor cells reduces tumor size, in comparison to age matched controls. While overexpression of RelA with the WT C11orf95-RELA fusion generates tumors that recapitulate WT tumor morphology, overexpression of p50 generates tumors with significantly altered transformed cell morphology. Our data demonstrates that both NF- κB subunits RelA and p50 are capable of interacting with the oncogenic C11orf95-RELA fusion, and that such interaction may contribute to ST-EPN tumorigenesis