POLD1 and glioblastoma: In LN-229 glioblastoma cells, genotyping of the CRISPR/Cas9-edited cells revealed 1/48 (2%) cell clones harboring a mutant POLE allele, 1/48 (2%) cell clones devoid of WT POLE alleles, 20/85 (24%) cell clones harboring a mutant POLD1 allele, and 0/85 cell clones devoid of WT POLD1 alleles (Additional file 1: Table S5).