Fig. 5: Fibroblast growth factor receptor 4 (FGFR4) chimeric antigen receptor (CAR)-modified T cells expressing an inducible caspase-9 (iCasp9) gene are eliminated by chemical inducer of dimerization (CID).

A The structure of the FGFR4–CAR–iCasp9 transgene. The transgene consists of a suicide gene, iCasp9, and FGFR4-specific chimeric antigen receptor (CAR), linked by a 2A-like sequence. iCasp9 consists of a drug-binding domain (FKBP12) connected via a short linker (GGGS) to human caspase-9. B FGFR4-CAR-iCasp9 T cells and FGFR4 CAR-T cells were exposed to CID (AP20187) at the indicated concentrations at different times. Cells were harvested and stained with annexin-V and 7-AAD. Data represent the mean and standard deviation (SD) values of quintuplicate wells. C Cytokine profiling of FGFR4-CAR-iCasp9 T cells and FGFR4 CAR-T cells in response to RH4 cells after 16-h incubation with CID. Data represent the mean and SD values of quintuplicate wells. IL-2 interleukin-2, IL-6 interleukin-6, IFN-γ interferon-γ, TNF-α tumor necrosis factor α. D RH4 cells were co-cultured with FGFR4–CAR–iCasp9 T cells or FGFR4 CAR-T cells at an effector:target ratio of 1:1. Under the condition of co-culture, CAR-T cells were treated with 16 nM CID. Fluorescence-activated cell sorting analysis for annexin-V and 7-AAD in RH4 cells was performed at 0 and 16 h. Data represent the mean and SD values of quintuplicate wells.