PARP1 and glioblastoma: To assess cellular toxicity to a single or combined treatment of PARP1 inhibitor (Olaparib; 10nM, 1μM and 10μM) and/or ATR inhibitor (AZD6738; 0.5μM; 1μM, 10μM and 20μM), we performed clonogenic survival assays using two different glioblastoma cell lines (LN428 and LN18).