The major implications of our study include that (i) we have developed an immunocompetent mouse model tool for the study of the Ewing sarcoma TME and the preclinical evaluation of TME-modulating agents in Ewing sarcoma, (ii) our data support the potential use of TGFβ inhibition during radiotherapy to promote immune cell infiltration into Ewing tumors, and (iii) our data indicate that TGFβ inhibition may reduce metastatic potential following radiotherapy in Ewing sarcoma. The gene discussed is TGFB1; the disease is Ewing sarcoma.