PTEN and glioblastoma: Established glioblastoma cells (SF188, T98G, U251, LN229), glioma stem-like cells (NCH421K, NCH644) and glioblastoma cells derived from a PDX-model (GBM12) or a murine transgenic model (MGPP-3; PDGFR+, PTEN−/−, TP53−/−) were treated for 72h with increasing concentrations of L-asparaginase prior to performing MTT- or CellTiter-Glo®-assays.