Human glioblastoma cells (LN229, U87, and U251) were purchased from the cell bank of the Chinese Academy of Sciences (Shanghai, China). Primary GBM cells (G1, G2 and G3) that derived from three primary GBM surgical specimens were maintained in DMEM supplemented with 10% FBS. Normal human astrocytes were purchased from ScienCell Research Laboratories (USA). Three different sequences of CBX7 siRNA were purchased from GenePharma (Shanghai, China). Lentivirus vectors and plasmids were purchased from GeneChem (Shanghai, China). FK228 was purchased from MedChemExpress (USA).