CD28 and neoplasm: This study showed that the treatment of mice bearing large established solid tumors with CAR T cells co-expressing PD1-CD28 switch receptor led to a significantly improved regression of tumors due to enhanced CAR T infiltration, increased CAR T cell proliferation and persistence, decreased susceptibility to tumor-induced hypofunction and attenuation of inhibitor receptor expression, compared with treatments with CAR T cells alone or CAR T cells with PD1 checkpoint inhibitor (Liu et al., 2016a).