PER2 and glioblastoma: To test this hypothesis and to find novel strategies to treat GBM, we evaluated the effects of 1) synthetic inhibitors of cytosolic kinases such as CHIR99021 (GSK-3 inhibitor) and PF670462 (CK1ε/δ inhibitor), 2) the cryptochrome protein stabilizer (KL001), or 3) clock gene Per2 disruption on GBM T98G cell biology.