IAP antagonism was previously published to sensitize cells from breast, prostate, colon, urothelial, cervical, nasopharyngeal, bladder and pancreatic cancers, leukemias, neuroblastomas and gliomas to killing by TRAIL [26, 36, 38, 39, 43-45, 80-85], so the resistance of osteosarcoma cells to this combined treatment is unusual. This evidence concerns the gene TNFSF10 and osteosarcoma.