POLD1 and glioblastoma: Overall, genomic characterization of the 94 GBM GSC samples unveiled among the top mutated genes several driver genes previously described in brain tumors such as TP53, PTEN, RB1, NF1, POLD1, PIK3CA, EGFR, and MSH6, thus indicating that GSCs maintain genetic alterations similar to those found in GBM patients.