Abstract
Introduction: Urokinase-type plasminogen activator (uPA) is upregulated in prostate cancer, but its comprehensive impact on the immune microenvironment and the underlying mechanisms remains to be fully elucidated. Methods: uPA expression was analyzed in clinical prostate cancer specimens and correlated with CD8⁺ T cell infiltration. Tumor growth was assessed in the uPA-deficient (uPA-/-)and the uPA inhibitor UK122-treated mouse model. Immune infiltration was evaluated by CyTOF and flow cytometry. Anti-CD19 chimeric antigen receptor (CAR)-engineered WT or uPA-/- CD8⁺ T cells were tested for cytotoxicity against RM1-CD19 cells. The combination of UK122 and anti-PD-1 therapy was assessed. Results: Elevated uPA in prostate cancer specimens inversely correlated with CD8⁺ T cell infiltration. Both genetic uPA ablation and UK122 significantly attenuated tumor growth by enhancing antitumor immunity. uPA deficiency markedly increased CD8⁺ T cell infiltration. uPA-/- CD8⁺ T cells exhibited enhanced cytotoxicity compared to WT CD8⁺ T cells. Tumor-infiltrating uPA-/- CD8⁺ T cells showed higher PD-1 expression. UK122 synergized with anti-PD-1 therapy to promote tumor regression. Discussion: uPA is a significant immunosuppressive regulator in prostate cancer. Its inhibition enhances CD8⁺ T cell function and synergizes with immune checkpoint blockade, supporting uPA targeting as a novel strategy to improve prostate cancer immunotherapy efficacy.