USP1 and osteosarcoma: Ubiquitin-specific protease 1 (USP1), a sub-type of deubiquitinases, reportedly regulates DNA-repair processes by deubiquitinating proliferating cell nuclear antigen and Fanconi anemia group D2 and preserves cancer stem cells in osteosarcoma by stabilizing inhibitor of DNA binding (ID)1 and ID2 (12, 13).