Abstract
Cutaneous squamous cell carcinoma (cSCC) is the second most prevalent form of nonmelanoma skin cancer, with 2.4 million cases annually and significant mortality. Photodynamic therapy (PDT) is a promising antitumor strategy, and its integration with immunotherapy has garnered attention. Herein, we develop STBF, a modified chlorin e6 derivative with superior solubility and efficacy, and propose a treatment paradigm integrating PDT with immunotherapy to address conventional PDT limitations in advanced cSCC. Mechanically, STBF-PDT induces PANoptosis, triggering immunogenic cell death through the stimulator of interferon genes (STING) pathway, while the STING agonist amplifies these effects and promotes dendritic cell activation. STBF-PDT reshapes the tumor microenvironment, enhancing immune checkpoint inhibitor responses. Incorporating lymphocyte activation gene 3 (LAG3) blockade further strengthens systemic antitumor immunity by suppressing myeloid-derived suppressor cells while augmenting type 2 conventional dendritic cells, cytotoxic T lymphocytes, and tissue-resident memory T cells. Our findings highlight the potential of STBF-PDT-STING agonism-anti-LAG3 combinations for metastatic and locally advanced cSCC.