Overall, administration of IL-15SA/IL-15RαSu-Fc exhibited a potent antimetastatic activity against not only 4T1 breast (Figure 7) but also CT26 colon carcinoma (Figure 8), and produced a synergistic anti-tumor response against CT26 pulmonary metastasis in combination with checkpoint inhibitors, driven mainly by anti-CTLA-4. Here, CTLA4 is linked to colon carcinoma.