This led us to speculate that a paracrine feedforward loop might be generated between USP6/Ewing sarcoma and NK cells (see model, Fig. 5A), wherein NK cells activated by USP6 produce elevated levels of IFNγ, which feeds back on the USP6/Ewing sarcoma cells to induce synergistic expression of IFN response genes such as CXCL9/CXCL10 due to their elevated expression of IFNGR1 and Jak1 (20). This evidence concerns the gene CXCL9 and Ewing sarcoma.