In the present study, to better characterize the oncogenic role of the PAX3-FOXO1 fusion protein in the acquisition of aggressive behavior in ARMS, we conducted proteomic studies using a PAX3-FOXO1 knockdown system in ARMS cell lines and in vitro assays, and found that among the protein list, proteins encoded by PPP2R1A were downregulated in the native ARMS cell lines. This evidence concerns the gene PAX3 and alveolar rhabdomyosarcoma.