FOXO1 and alveolar rhabdomyosarcoma: The first and only published model for ARMS [38] in which expression of a conditional Pax3-Foxo1 knock-in fusion oncogene is induced by a Myf6 driven Cre had a low incidence and long latency of tumor development, requiring the presence of two Pax3-Foxo1 alleles on a Trp53-null or Ink4a/Arf-null background.