IL13 and fibrosarcoma: To test the effects of the different signaling domains on CAR effector activity, we cocultured the IL13(E12Y)-CAR T cell variants with IL13Rα2-negative HT1080 human fibrosarcoma cells, IL13Rα2-engineered HT1080 (HT1080-Rα2), or the patient-derived GBM line PBT030-2, with glioma stem cell–like characteristics (6), IL13Rα1 and IL13Rα2 profiles shown in ref. 6.