CEACAM5 and neoplasm: Studies found that some cytokines can increase T‐cell activity, of which IL‐12 can mediate multiple immune reactions and some preclinical studies found that IL‐12 had anti‐tumor activity by regulation of immune reactions.28 Clinical studies found that intravenous injections of low dose rhIL‐12 resulted in significant anti‐tumor activity and the corresponding toxic effect was tolerable.29 Therefore, we used CEA‐CAR‐T cells in combination with rhIL‐12 to enhance their activity in treatment of solid tumors.