The growth of EwS and also OS xenografts induced the expansion of granulocytic murine MDSC in the blood, spleens, and tumors of NSG mice, which was associated with a lack of antitumor activity of tumor-targeted CAR T cells, and MDSCs isolated from spleens of these mice suppressed CAR T cell proliferation in coculture experiments in vitro [57]. This evidence concerns the gene EWSR1 and neoplasm.