Adeno-Associated Virus-Mediated IL-2 Delivery in Liver Cancer: Immune Activation and Therapeutic Challenges

Hepatocellular carcinoma (HCC), a prevalent primary liver cancer, poses a significant global health challenge. The liver's immune population is selectively enriched in natural killer (NK) cells, natural killer T (NKT) cells, and CD8⁺ T cells, which play critical roles in anti-tumor responses. Interleukin-2 (IL-2) holds promise in activating these immune cells for cancer therapy, but its short half-life and systemic toxicity limit its application. This study aimed to enhance hepatic NK, NKT, and T cells using a liver-preferred adeno-associated virus (AAV) to deliver IL-2 (AAV-IL-2) sustainably for HCC therapy in a syngeneic orthotopic mouse model. At first, we administered high, medium, and low doses of AAV-IL-2 to naive mice, revealing that only the medium dose expanded hepatic NK, NKT, and T cells without inducing toxicity. In HCC-bearing mice, low-dose AAV-IL-2 treatment had minimal effects. Medium-dose AAV-IL-2 treatment expanded and activated hepatic NK, NKT, and T cells but also induced intratumoral CD8⁺ T cell exhaustion. Notably, medium-dose AAV-IL-2 had no suppression of tumor progression but higher mortality. These results underscore the challenging balance required for effective HCC treatment with IL-2, as a medium dose successfully enhances hepatic immune cells but simultaneously induces CD8+ T cell exhaustion and higher mortality.