CASP9 and brain cancer: Previous studies demonstrated that COR induces the apoptosis of cancer cells by enhancing intracellular ROS via the ROS/caspase-8/caspase-9/caspase-3/caspase-5/caspase-7 pathway in human leukemia cell lines (U937 and THP-1) in vitro [38] and via an antioxidant protein-mediated pathway (GPX/superoxide dismutase (SOD)/Catalase/ROS/Bax/BCL-2/caspase-9/caspase-3) in brain cancer cell lines (SH-SY5Y and U-251) in vitro [36].