XRCC4 and glioblastoma: Notably, CK2β protein is modestly induced in GXP NS and nearly undetectable in Xfl/flPfl/fl (XP-undeleted; WT) NS and normal adult brain (Fig. 2d), indicating CK2 activity may be instigated by DNA damage induced in the XRCC4/p53-deficient setting and pathologically altered in GXP GBMs and the tested GBM cell lines.