ID3 and central nervous system cancer: To illustrate that Per2 controls the development of glioma by suppressing Id3, we first overexpressed Id3 in U87 and U251 cells and then transfected a lentiviral vector overexpressing Per2 in Id3 OE cells (Id3 OE+Per2 OE) to confirm that Per2 can reverse the Id3-mediated malignant biological behavior of glioma.