Strong capacity of differentiated PD‑L1 CAR‑modified UCB‑CD34+ cells and PD‑L1 CAR‑modified UCB‑CD34+‑derived NK cells in killing target cells and restoration of the anti‑tumor function of PD‑1‑high exhausted T Cells

Background: Using natural killer (NK) cells to treat hematopoietic and solid tumors has great promise. Despite their availability from peripheral blood and cord blood, stem cell-derived NK cells provide an “off-the-shelf” solution.

Methods: In this study, we developed two CAR-NK cells targeting PD-L1 derived from lentiviral transduction of human umbilical cord blood (UCB)-CD34+ cells and UCB-CD34+ derived NK cells. The transduction efficiencies and in vitro cytotoxic functions including degranulation, cytokine production, and cancer cell necrosis of both resultants PD-L1 CAR-NK cells were tested in vitro on two different PD-L1 low and high-expressing solid tumor cell lines.

Results: Differentiated CAR‑modified UCB-CD34+ cells exhibited enhanced transduction efficiency. The expression of anti-PD-L1 CAR significantly (P < 0.05) enhanced the cytotoxicity of differentiated CAR‑modified UCB-CD34+ cells and CAR -modified UCB-CD34+-derived NK cells against PD-L1 high-expressing tumor cell line. In addition, CAR -modified UCB-CD34+-derived NK cells significantly (P < 0.05) restored the tumor-killing ability of exhausted PD-1 high T cells.

Conclusions: Considering the more efficient transduction in stem cells and the possibility of producing CAR-NK cell products with higher yields, this approach is recommended for studies in the field of CAR-NK cells. Also, a pre-clinical study is now necessary to evaluate the safety and efficacy of these two CAR-NK cells individually and in combination with other therapeutic approaches.