Animal experiments were approved by the Animal Management Rule of the Chinese Ministry of Health (documentation 55, 2001) and were in accordance with the approved guidelines and the experimental protocol of Nanjing Medical University. Luciferase stably expressed U87 cells were transfected with Lenti-CBX7 or Lenti-Ctrl. Twelve mice purchased from Cancer Institute of the Chinese Academy of Medical Science were randomly divided into CBX7 upregulated group or control group. To establish intracranial glioma model, each nude mouse was implanted with 1 × 106 U87Luciferase/CBX7 or U87Luciferase/Ctrl cells (day 0). The intensity of bioluminescence was positively correlated with the number of U87 cells. Tumor growth was assessed weekly by live animal bioluminescence imaging system. After four times testing (day 7, day 14, day 21 and day 28), the survival of mice was observed until day 60. Then mice were exposed to CO2 to achieve euthanasia. Brains tissue sections were incubated with antibodies including CBX7 and Cyclin E1.