Background: B-cell lymphoma is a highly prevalent malignancy of the hematopoietic system. Chimeric antigen receptor (CAR)-natural killer (NK) cell therapy is increasingly being used to treat hematologic malignancies. However, relatively few studies have explored the feasibility of combining CAR-NK therapy with PD-1 inhibitors for lymphoma treatment. This study aimed to investigate the feasibility and therapeutic efficacy of combining CAR-NK cells with a programmed death-1 (PD-1) inhibitor for the treatment of B-cell lymphoma.

Methods: Umbilical cord blood (CB)-derived NK cells were transduced with a retroviral vector encoding CAR-19, interleukin-15 (IL-15), and an inducible caspase-9 (iC9)-based suicide gene. The impact of iC9/CAR-19/IL-15 CAR-NK cell therapy combined with PD-1 inhibitor treatment on lymphoma cell cytotoxicity was evaluated separately through in vitro cell-based assays and in vivo animal experiments.

Results: iC9/CAR-19/IL-15 CAR-NK cells combined with PD-1 inhibitors (a combined therapy) selectively killed primary chronic lymphocytic leukemia (CLL) cells in vitro. The cytokines CD107a, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α) were increased in iC9/CAR-19/IL-15 CAR-NK cells, but were barely changed under the influence of PD-1 inhibitors. Compared to monotherapy, the combined therapy significantly elevated IL-22, IL-6 and IL-15 secretion levels (p < 0.05), and more importantly, greatly extended the survival of model mice (p < 0.001). Furthermore, a decrease in TNF-α, IL-6 and IL-10 levels was observed in the serum of model mice (p < 0.05).

Conclusions: The combined therapy of iC9/CAR-19/IL-15 CAR-NK cells with PD-1 inhibitors exhibits remarkable antitumor activity and prolongs survival, providing a potential novel treatment route for B-cell lymphoma.