PDCD1 and neoplasm: Nonetheless, genetically modified CAR T to express an IL-4/IL-21 inverted cytokine receptor (4/21 ICR), in which the extracellular domain of the IL-4R is fused to the intracellular domain of the IL-21R, efficiently killed tumor cells producing IL-4 and exhibit an attenuated expression of PD-1 (Programmed cell death protein 1) and Tim-3 (T-cell immunoglobulin domain and mucin domain 3) inhibitory molecules.