Nanosized Shikonin Disrupts Tumour-cell Mismatch Repair and Synergizes with Manganese to Sensitize Squamous Carcinoma to Immunotherapy

Head and neck squamous cell carcinoma (HNSCC) exhibits resistance to immune checkpoint blockade (ICB) therapy due to its immune-excluded microenvironment. Immunogenic cell death (ICD) can increase tumor's immunogenicity and further attract immune cell infiltration. Herein, we developed CGKRK-modified lipid nanoparticles (C-SNPs) loaded with shikonin (SHK) and confirmed C-SNPs could effectively target tumors and induce cells to undergo necroptotic ICD both in vitro and in vivo. RNA sequencing revealed that C-SNPs downregulated mismatch repair pathway within tumors. This alteration activated the cGAS-mediated interferon (IFN) response, further raising the expression of programmed cell death ligand-1 (PD-L1) on tumor cells. Although combining C-SNPs with anti-programmed death-1 (anti-PD-1) therapy could promote more dendritic cells and CD8+ T cells infiltrations, tumors' durable response was limited. Ensuing modification of C-SNPs with Mn2+ enhanced the activation of the cGAS-STING axis and promoted the maturation of dendritic cells and differentiation of cytotoxic effector T cells within the tumor under anti-PD-1 therapy. Importantly, combining anti-PD-1 therapy with C-SMNPs exhibited a more sustained tumor-suppressing effect than with C-SNPs. Our findings presented a strategy to overcome resistance to immunotherapy that combining nanonized ICD inducers and manganese, which disrupted tumor cells' mismatch repair, stimulated the cGAS-STING-mediated IFN response and triggered host's antitumor immunity.