The in vivo persistence of 4-1BB-CAR-T cells was superior to the CD28, which displayed enhanced phosphorylation intensity (7, 115, 116); the third-generation CAR-T cells sometimes exhibited inferior in vivo persistence and tumor-killing capacity as compared with the second-generation CAR-T cells (8–10); CAR-T cells with PD-1 silencing tended to differentiate into terminally exhausted T cells (96, 97). Here, PDCD1 is linked to neoplasm.