In this study, we demonstrated that IL-15/IL-15Rα enhanced the function of CAR-T cells both quantitatively and qualitatively, evidenced by improved expansion and cytotoxicity in vitro, more robust production of IFN-γ, IL-2, TNF-α and granzyme B upon co-culture with cancer cells, and enhanced tumor control in vivo. This evidence concerns the gene IL15 and cancer.