PROM1 and glioblastoma: We used three different glioma lines: AC133/CD133-negative U251 wild-type (WT) cells, used as a control; CD133-overexpressing (OE) U251 cells transduced with a CD133-encoding lentivirus [24]; and the patient-derived GBM-SC line NCH421k [25] with an approximately 10–15-fold lower AC133 expression compared to the CD133-OE U251 glioma line (Figure 2A).