CRISPR/Cas9-mediated PD-1 attenuation enhances tumor infiltrating lymphocyte-based adoptive cellular therapy in humanized-PDX model of hepatocellular carcinoma.

[BACKGROUND] Tumor-infiltrating lymphocyte (TIL)-based adoptive cellular therapy (ACT) has become a promising therapeutic approach due to its ability to effectively control disease in multiple types of solid tumor. Antibodies against the negative immune checkpoint programmed cell death protein 1 (PD-1) have been widely used in cancer immunotherapy. We hypothesized that PD-1 depletion in hepatocellular carcinoma (HCC) TIL-derived T cells would enhance their anti-tumor efficacy.

[METHODS] CRISPR/ Cas9 system was employed to target PDCD1 in HCC TIL-derived T cells. The phenotypic and functional changes were analyzed by flow cytometry. T-cell receptor (TCR) sequencing and bulk RNA-sequencing of PD-1-edited or non-edited T cells was conducted to examine their differences. Finally, we demonstrated the ability of PD-1-edited or non-edited T cells to inhibit tumor growth in HCC patient-derived xenograft (PDX) models.

[RESULTS] CRISPR/Cas9 system was demonstrated to provide an effective and stable PD-1-editing efficiency. The phenotypes, effector and memory subpopulations of the PD-1-edited T cells were found to have maintained stability, while they did acquire higher potential in terms of autologous tumor cell elimination. Compared to their counterpart, PD-1-edited T cells also retained a higher level of homology with the whole and tumor-specific TCR clonotypes of primary HCC TILs. Furthermore, PD-1-edited T cells exhibited a superior anti-tumor response compared with non-edited T cells in HCC PDX models.

[CONCLUSION] Taken together, our results have provided a foundation for the clinical application of ACT based on genetically modified TIL, offering a new perspective on exploring clinical immunotherapy strategies for HCC, and potentially other solid tumors.