PTEN and glioblastoma: As a first approach to analyze the potential of PARP inhibition (PARPi) as monotherapy against GBM we evaluated self-renewal capability, which is a marker of stemness in GSCs, using neurospheres formation assay in primary patient-derived PTEN-proficient GSCs TG1 [21] with two different PARP inhibitors: PJ34 (IC 20 nM) and olaparib (IC 5 nM).