PN–GBM tumors are characterized by high expression of OLIG2 and TCF3 genes, whereas MES–GBMs express high levels of MET, CD44, and CHI3LI/YLK40 driver genes [24], as well as a number of passenger genes (TCGA Glioblastoma Genome Atlas https://wiki.cancerimagingarchive.net/display/Public/TCGA–GBM, accessed on 22 April 2021). Here, CD44 is linked to glioblastoma.