Targeted nanosensitizer-augmented sono-immunotherapy with STING agonist to remodel the immune microenvironment in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the most common primary malignant disease of the liver. Although immunotherapy offers new opportunities for treating advanced HCC, its therapeutic effect is still limited by the immunosuppressive tumor microenvironment (TME). Herein, a nanosensitizer RGD@Ce6@MSA-2@Liposome (RCM-Lip) is synthesized to specifically initiate the HCC tumor immune microenvironment through sonodynamic therapy (SDT)-triggered immunogenic cell death (ICD) and MSA-2-activated cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. RCM-Lip consists of a sonosensitizer (Chlorin e6, Ce6) with a STING agonist (MSA-2) and a tumor targeting peptide RGD inserted on the outer liposome surface. Under ultrasound irradiation, RCM-Lip generates reactive oxygen species that induce cytotoxicity and apoptosis of tumor cells. Meanwhile, tumor antigens released by apoptosis are taken up by dendritic cells (DCs), while STING is activated in the DCs by MSA-2. Moreover, DC maturation is stimulated, further enhancing the systematic anti-tumor immune responses. Sono-immunotherapy mediated by RCM-Lip promotes DCs maturation and tumor infiltration of CD8⁺T cells, increasing inflammatory cytokine secretion. Consequently, the immunologically "cold" TME of HCC is successfully turned into a "hot" one, leading to a significant tumor suppression effect with good bio-safety. These results suggest a promising method for precise tumor targeting and synergistic cancer sono-immunotherapy. STATEMENT OF SIGNIFICANCE: Our study addressed the therapeutic dilemma of hepatocellular carcinoma (HCC) as an immunological "cold" tumor by the synergistic application of sonodynamic therapy (SDT) and STING agonist. The cGAS-STING signaling pathway plays a pivotal role in innate immunity against cancer, but the clinical application of STING agonists were hampered by inflammatory responses due to off-target activation. Our innovative solution introduces RGD-targeted peptide to encapsulate sonosensitizer and STING agonist, strengthening therapeutic effects and reducing systemic toxicity. The targeted sono-immunotherapy promoted DCs maturation and tumor infiltration of CD8⁺T cells, producing intense tumor-killing effect on mice model with good bio-safety. As a result, the immunological "cold" tumor microenvironment of HCC is successfully turned into a "hot" one.