Fig. 1

A comparison between random integration and site-specific integration in CAR T cell therapy. Random integration: random integration with viral particles usually includes the utilization of strong viral or non-viral promoters (CMV and EF1α, respectively) that constantly express the CAR transgene if integrated into highly expressed regions. This event is occasionally accompanied by strong exogenous gene expression by normal T/NK cells as well as antigen-independent tonic signaling due to the CAR clustering phenomenon. The pressure and tonic signaling result in the exhaustion of CAR T cells with less central memory phenotype and consequently poor clinical outcomes. Site-specific integration: site-specific integration of the CAR transgene under the active promoters of T/NK cells (such as TCRα) not only does not impose any external pressure but it also allows the CAR transgene to use the corresponding regulatory factors other than the promoter (such as the enhancer/silencer) and also enables the secondary structure of chromatin to regulate CAR expression as a dynamic phenomenon. Therefore, long-lasting central memory T cells with low exhaustion phenotype and high antitumor functionality can be expanded and employed to eradicate tumor cells