The importance of DNA-PK in radiation responses are illustrated by studies on the human glioblastoma cell lines M059K and M059J, proficient and deficient in DNA-PKcs, which show large differences in radioresponsiveness with the latter being hypersensitive (Allalunis-Turner et al, 1995; Lees-Miller et al, 1995). This evidence concerns the gene PRKDC and glioblastoma.