CAT and neoplasm: To retain their anti‐tumor potential, T cells co‐expressing catalase along with a CAR were designed to overcome high levels of ambient ROS with higher amounts of intracellular catalase, compared with normal CAR‐T cells.[140] However, because it is difficult for cell‐based immunotherapies to avoid damage caused by high ROS levels after delivery, researchers ingeniously exploited ROS‐induced damage to kill tumor cells using cell‐based delivery methods to produce excessive ROS artificially.[141, 142, 143] For example, Huang et al.