MAPK8 and osteosarcoma: Overgeneration and accumulation of ROS, inducing apoptosis of HCS 2/8 chondrosarcoma and SJSA osteosarcoma cells through overexpression of Bax, caspase-3, JNK activation, and STAT3 inhibition and lessening the size of the tumor in a patient-derived xenograft (PDX) mouse model