Multifunctional hybrid exosomes enhanced cancer chemo-immunotherapy by activating the STING pathway

Due to the immunosuppressive tumor microenvironment (ITM) resulting from tumor-associated macrophages (TAMs) and regulatory T cells, immune checkpoint blockade and vaccine therapies often lead to an inadequate immune response. Recently, cyclic guanosine monophosphate-adenosine monophosphate synthase/stimulator of interferon gene (cGAS/STING)-mediated innate immunity has emerged as a promising cancer therapeutic, as STING pathway activation could promote dendritic cells (DCs) maturation and tumor-specific cytotoxic T lymphocyte (CTL) and natural killer (NK) cell infiltration. Herein, multifunctional hybrid exosomes for cGAS/STING activation are designed by fusing genetically engineered exosomes carrying CD47 derived from tumor cells with exosomes from M1 macrophages, which are further encapsulated with DNA-targeting agent (SN38) and STING-agonist (MnO2). The hybrid exosomes demonstrate great tumor-targeting capacity and prolong blood circulation time due to the surface decoration of CD47. At the tumor site, the hybrid exosomes induce TAMs polarization to the M1 phenotype and release SN38 to induce DNA damage and Mn2+ to stimulate cGAS/STING activation. Furthermore, the resulting multifunctional hybrid exosomes (SN/Mn@gHE) promote DCs maturation and facilitate CTL infiltration and NK cell recruitment to the tumor region, leading to significant anti-tumor and antimetastatic efficacy. Our study suggests a novel strategy to enhance cancer immunotherapy by activating the STING pathway and ameliorating ITM.