shRNA-based PD-1 suppression preserves memory phenotype and function of CD19-targeted CAR-T cell.

Background: Chimeric antigen receptor T cell (CAR-T) therapy targeting cluster of differentiation 19 (CD19) has shown promise in treating B-cell acute lymphoblastic leukemia (B-ALL), but the long-term efficacy of CD19-targeted CAR-T therapy remains limited. Programmed cell death protein 1 (PD-1), an inhibitory receptor on activated T cells, engages programmed death ligand 1 (PD-L1) in the tumor microenvironment, suppressing CAR-T cell function by impairing key signaling pathways. To address this limitation, we investigated the effect of short hairpin RNA (shRNA)-mediated PD-1 knockdown on alleviating CAR-T cell exhaustion, preserving memory phenotype, and enhancing the long-term efficacy of CD19-targeted CAR-T cells. Methods: To overcome this limitation, we employed shRNA to achieve PD-1 knockdown in CD19-targeting CAR-T cells. Following screening multiple shRNA candidates, we assessed the cytotoxicity, cytokine secretion, and proliferation of PD-1 knockdown CAR-T cells. Their memory phenotype, exhaustion marker, and cytolytic function were further evaluated after repeated antigen stimulation. Therapeutic efficacy and safety were validated in NOD.Cg-PrkdC Results: PD-1 knockdown significantly enhanced CAR-T cell cytotoxicity and persistence against PD-L1+ RAJI (human Burkitt's lymphoma cell line) cells. After three rounds of antigen stimulation, PD-1 knockdown CAR-T cells sustained cytotoxic activity, retained a memory-like phenotype, and displayed attenuated exhaustion markers. Conclusions: PD-1 knockdown mitigates tumor-induced T-cell exhaustion and represents a promising strategy to enhance the durability and potency of CAR-T cell therapy in cancer treatment.