In summary, we could show that (1) the ion channels of T cells necessary for Ca2+-related functions are also present in HER-CAR-expressing T cells, (2) CD8+ CAR T cells have a higher KCa3.1 but lower CRAC level as compared to the control, and (3) the inhibition of Kv1.3/KCa3.1 channels facilitates the cancer cell elimination capacity. The gene discussed is KCNN4; the disease is cancer.