ASCL1 and cancer: This unexpected change in GBM subtype with tumor cell type also holds when Ascl1-OE tumor cells were assigned using cancer cellular state signature genes derived from human GBMs16, demonstrating that GBM subtype identities, especially proneural and classical, may be better defined by transcriptional targets of ASCL1 and/or OLIG2 rather than the glial cell types by which they may share some overlapping marker gene expression.