RB1 and osteosarcoma: Although candidate oncogenes (e.g., RUNX2, VEGFA, MDM2, and PRIM1) 9-12 and tumor suppressors (e.g., TP53, RB1, and PTEN) 13-15 have been identified in human osteosarcoma, the search for common molecular therapeutic targets in osteosarcoma has been disappointing to date 2.