GPX4 and osteosarcoma: Since ROS are known to trigger or promote the mitochondrial apoptotic pathway under cisplatin treatment [14, 15] and GPX4 functions as a resistance molecule to ROS [16], we hypothesized that increased cisplatin-induced apoptosis due to OTULIN depletion in osteosarcoma cells is associated with GPX4 deficiency and increased mitochondrial oxidative stress.