Inhibition of K⁺ Channels Affects the Target Cell Killing Potential of CAR T Cells

Ion channels of T cells (Kv1.3, KCa3.1, and CRAC) participate in the regulation of activation and effector functions via modulation of the Ca²⁺-dependent pathway. T cells expressing chimeric antigen receptors (CAR T cells) showed a remarkable role in anti-tumor therapy, especially in the treatment of chemotherapy-resistant liquid cancers. Nevertheless, many challenges remain to be overcome to improve the treatment for solid tumors. In this study, we assessed the expression and role of ion channels in CAR T cells. We found that HER2-specific CAR T cells had higher KCa3.1 conductance compared to the non-transduced (NT, control) cells, which was more prominent in the CD8⁺ population (CD4⁺ cell also showed elevation). Conversely, the Kv1.3 expression level was the same for all cell types (CD4⁺, CD8⁺, CAR, and NT). Single-cell Ca²⁺ imaging revealed that thapsigargin-induced SOCE via CRAC is suppressed in CD8⁺ CAR T cells, unlike for CD4⁺ and CD8⁺ NT cells. To dissect the functional role of Kv1.3 and KCa3.1, we used specific antagonists (Kv1.3: Vm24; KCa3.1: TRAM-34): the target cell elimination capacity of the CD8⁺ CAR T cells was improved either by blocking KCa3.1 or Kv1.3. These results imply that ion channels could be a target in CAR T cell immunotherapy elaboration.