Multiple preclinical studies have shown that engineering CAR-T cells to express proinflammatory cytokines in various combinations (IL-2 and IL-33 [181], IL-12 [182], IL-15 [183], IL-15 and IL-21 alone or in combination [184], IL-18 [59,185,186], and IL-23 [187]) leads to improved CAR-T cell proliferation and control of tumor growth in mouse models of solid tumors. The gene discussed is IL15; the disease is neoplasm.