Tumor-targeting nanocarriers amplified immunotherapy of cold tumors by STING activation and inhibiting immune evasion

The low immunogenicity and immune escape are bottlenecks for effective tumor immunotherapy. Here, we synthesized multifunctional polymers comprising a photosensitizer and cationic and thiol derivates and engineered a galactose-installed stimulator of interferon genes (STING) agonist and programmed death ligand 1 (PD-L1) small interfering RNA (siPDL1)-encapsulated nanocarriers (cGAMP-siPDL1@GalNPs) for synergistic immunotherapy of low immunogenic tumors through stimulating robust immune responses. cGAMP-siPDL1@GalNPs efficiently delivered the drugs into cancer cells by targeting the galactose receptors to trigger photo-/redox-/pH-activated drug release. cGAMP-siPDL1@GalNPs stimulated robust antitumor immunity via STING activation and immunogenic cell death (ICD) and inhibited immune escape via knockdown of PD-L1 expression in tumors, which synergistically regulated the immune-suppressive tumor microenvironment. Upon laser irradiation, the nanocarriers efficiently eradicated primary melanoma and orthotopic triple-negative breast tumors and induced ICD effects, which synergically inhibited the distant tumor and spontaneous lung metastasis with improved survival rates. This study presents a strategy for developing nanocarriers to activate antitumor immunity and regulate immune invasion for effective immunotherapy.