PTEN and glioblastoma: GBM model 2 GSCs from the same panel of patient-derived tumor cells maintained at Yale School of Medicine were confirmed to form PTEN-deficient tumors in the brains of immunodeficient mice, and comparison of spheroid volumes after treatment with control or DX1 demonstrated significant suppression of spheroid growth by DX1 in a dose-dependent manner (Supplemental Figure 3).