In these mice, rhabdomyosarcoma is only induced when a Pax3:Foxo1 fusion oncogene is activated with concurrent loss of p53 function (for alveolar rhabdomyosarcoma) or loss of p53 function alone (for embryonal rhabdomyosarcoma) using Cre-lox technology. Here, FOXO1 is linked to embryonal rhabdomyosarcoma.