The tumor microenvironment generated by myeloid-derived suppressor cells; regulatory T cells; immunosuppressive cytokines, such as interleukin (IL)-10 and transforming growth factor-β; and ligands for tumor-expressed T-cell inhibitory signaling receptors, such as PD-1 and CTLA-4, contribute to attenuated persistence and antitumor efficacy of CAR T cells in solid tumors14,15. The gene discussed is CTLA4; the disease is neoplasm.