Sox2-dependent maintenance of mouse oligodendroglioma involves the Sox2-mediated downregulation of Cdkn2b, Ebf1, Zfp423 and Hey2

Abstract Cancer stem cells (CSC) are essential for tumorigenesis. The transcription factor Sox2 is overexpressed in brain tumors. In gliomas, Sox2 is essential to maintain CSC. In mouse high-grade glioma pHGG, Sox2 deletion causes cell proliferation arrest and inability to reform tumors in vivo; 134 genes are significantly derepressed. To identify genes mediating the effects of Sox2 deletion, we overexpressed into pHGG cells nine among the most derepressed genes, and identified four genes, Cdkn2b, Ebf1, Zfp423 and Hey2, that strongly reduced cell proliferation in vitro and brain tumorigenesis in vivo . CRISPR/Cas9 mutagenesis, or pharmacological inactivation, of each of these genes, individually, showed that their activity is essential for the proliferation arrest caused by Sox2 deletion. These Sox2-inhibited antioncogenes also inhibited clonogenicity in primary human glioblastoma-derived cancer stem-like cell lines. These experiments identify critical anti-oncogenic factors whose inhibition by Sox2 is involved in CSC maintenance, defining new potential therapeutic targets for gliomas. Table of Contents Image Main Points Sox2 maintains glioma tumorigenicity by repressing the antioncogenic activity of a regulatory network involving the Ebf1, Hey2, Cdkn2b and Zfp423 genes. Mutation of these genes prevents the cell proliferation arrest of Sox2-deleted glioma cells.