Chimeric cytokine receptor TGF-β RⅡ/IL-21R improves CAR-NK cell function by reversing the immunosuppressive tumor microenvironment of gastric cancer

Gastric cancer remains a significant global health burden, characterized by regional variations in incidence and poor survival prospects in advanced stages. Natural killer (NK) cells play a crucial role in the body's anti-cancer defense, and chimeric antigen receptor (CAR)–NK cell therapy is gaining attention as a cutting-edge and promising treatment method. This study aims to tackle the challenge of TGF-β-mediated tumor immune evasion within the immunosuppressive tumor microenvironment by designing a novel chimeric cytokine receptor TRII/21 R, which consists of extracellular domains of TGF-β receptor II (TRII) and transmembrane and intracellular domains of IL-21 receptor (21 R) and can convert the immunosuppressive signal from TGF-β in the tumor microenvironment (TME) into an NK cell activation signal through the IL-21R-STAT3 pathway. We successfully constructed NKG2D-CAR-NK cells expressing TRII/21 R and demonstrated strong anti-tumor activity against cancer cells both in vitro and in vivo. The co-expression of TRII/21 R in CAR-NK cells enhanced the cytotoxicity, promoted proliferation and survival capabilities, and reduced the expression of exhaustion markers. In the xenograft mouse model, TRII/21R-CAR-NK cells significantly inhibited tumor growth and improved the survival rate of tumor-bearing mice compared to the mice receiving control CAR-NK cells. Additionally, TRII/21 R co-expression enhanced NK cells' infiltration, activation, and persistence within the tumor, indicating a robust anti-tumor response mediated by the JAK-STAT3 signaling pathway. This study underscores the therapeutic potential of TRII/21R-modified CAR-NK cells as a breakthrough strategy for combating cancer.