RB1 and osteosarcoma: Uhrf1 KO mice result in embryonic lethality [36]; thus, we generated Uhrf1 cKO mice (Osx-cre Uhrf1lox/lox), Tp53/Uhrf1 DKO (Osx-cre Tp53lox/loxUhrf1lox/lox) and Tp53/Rb1/Uhrf1 triple knockout (Tp53/Rb1/Uhrf1 TKO; Osx-cre Tp53lox/loxRb1lox/loxUhrf1lox/lox) to study the role of UHRF1 in osteosarcoma development.