Although the overall effect of IL-15 on CAR-T cells was generally insignificant in in vitro assays, its role in vivo is marked, resulting in the significantly improved antitumor activity of H9 CAR-IL15 T cells compared with that of unmodified CAR-T cells in both murine tumor models in the presence of lymphodepleting pretreatment. Here, IL15 is linked to neoplasm.