Decreasing the binding affinity for IL13Rα1 to the micromolar range had the desired effect in in vitro tumor treatment assays, with both C4 and D7 CAR T cells showing diminished responses relative to WT and E12Y CAR T cells when exposed to IL13Rα1-expressing cancer cells and plate-bound IL13Rα1 (Fig. 5). The gene discussed is IL13RA1; the disease is neoplasm.