“…The newly discovered stimulator of interferon genes (STING), a transmembrane complex located in the endoplasmic reticulum, has opened a new avenue for enhancing the functions of APCs. − It has demonstrated that STING activation can stimulate the production of type I interferons (IFNs) via interferon regulatory factor 3 (IRF3) and nuclear factor kappa B (NF-κB) signaling pathways, which can induce the activation of APCs. , Activated APCs indirectly enable the activation and expansion of CD8 + T cells through the interaction between CD4 + T cells and APCs, or can directly activate CD8 + T cells. − In addition, type I IFNs can act directly on CD4 + T cells and CD8 + T cells to allow clonal expansion. , Multiple studies have reported that intratumoral injection of the STING agonist (cyclic guanosine monophosphate–adenosine monophosphate, cGAMP) was able to reverse tumor immunosuppression and elicit tumor-specific CD8 + T cells. − Therefore, the STING agonist-cGAMP is a potential agent for overcoming the poor immunogenicity of tumor cells and enhancing the functions of APCs. , However, cGAMP is a cyclic di-nucleotide linked by two phosphodiester bonds. Similar to other nucleic acids, it is easy to be degraded by extracellular phosphodiesterase and can hardly cross plasma membrane to enter the cytoplasm. − Several recently published studies have demonstrated that nanoparticles could improve the in vivo delivery efficiency of cGAMP, ,,− but no co-delivery of cGAMP and siRNA into APCs has been reported.…”