CRISPR knock-in mediated gene reprogramming to improve the anti-tumor activity of adoptive T cell therapy

Abstract

Because of its robustness and versatility, CRISPR/Cas9-based genome editing has rapidly evolved andis now used for a variety of purposes ranging from basic research to therapeutic applications. CRISPRnot only corrects the genetic mutation in T cells but also improves the therapeutic function of adoptiveT cell therapy. In this thesis, I utilized a CRISPR/AAV-based knock-in system to manipulate the genesrelated to T cell function to enhance the therapeutic function of TCR-T cells. First, the knock-out andknock-in optimization procedure for T cells were demonstrated, and the method for serial lentiviraltransduction and CRISPR/AAV knock-in of activated human T cells was established. Two independentstudies were investigated using this engineering method to increase the anti-tumor efficacy of NY-ESO-1 TCR-T cells. In the first project, to convert the inhibitory signaling into the T cell supportive signal, Iinserted the IL-12 gene into the PDCD1 locus, which allows for tight expression control of the potentimmune-stimulatory cytokine, IL-12, in a T cell activation-dependent way. The suboptimal level of IL-12 released from the edited PDCD locus was sufficient to enhance the function of NY-ESO-1 TCR-Tcells. Consequently, PD-1 edited NY-ESO-1 TCR-T cells not only secreted the increased level ofeffector molecules in vitro but also exhibited robust proliferative capacity during repeat antigenstimulation. In vivo studies subsequently revealed that this PD-1 edited NY-ESO-1 TCR-T cellseffectively eliminated tumors while infiltrating the tumor locus more than control TCR-T cells. In thesecond project, to incorporate a co-stimulatory signal into primary T cell signaling, I inserted the 4-1BBsignaling domain into the CD247 locus, which generates 4-1BB-attached CD3$ \zeta$ in NY-ESO-1 TCR-Tcells. However, I discovered that expressed zBB was incapable of forming a TCR complex andtransducing proper zeta signaling. To address this issue, the N-terminus sequences in 4-1BB weretruncated, which contained a highly clustered positively charged amino acids. The truncated 4-1BB notonly restored TCR complex formation and primary zeta signaling but also delivered the proper 4-1BBsignaling. In vivo studies subsequently demonstrated that these CD247-edited NY-ESO-1 TCR-T Cellsoutperformed control TCR-T cells in tumor control while infiltrating into tumor tissues. Collectively,these findings suggest that the editing of functional genes in T cells will have significant implicationsand provides a novel option for the development of the next generation of TCR-T therapy for solid tumortreatment.