In a recent clinical trial evaluating IL-15–engineered GPC3-targeted CAR-T cells for the treatment of hepatocellular carcinoma (HCC), IL-15 expression markedly enhanced CAR-T cell persistence, proliferation, and antitumor efficacy in vivo, demonstrating the potential of cytokine-armored CAR constructs to overcome the immunosuppressive tumor microenvironment (22). The gene discussed is GPC3; the disease is hepatocellular carcinoma.