PER2 and neoplasm: To determine whether the influence of Per2 overexpression can be similarly verified in vivo, we created U87-Per2 OE cells, U87-Id3 OE cells, U87-Id3 OE+Per2 OE cells, and U87-empty lentiviral vector cells as controls, and tumor cells were intracranially transplanted into nude mice to assess tumorigenesis.