Nanoenabled Reversal of IDO1-Mediated Immunosuppression Synergizes with Immunogenic Chemotherapy for Improved Cancer Therapy

Certain chemotherapeutics (e.g., oxaliplatin, OXA) can evoke effective antitumor immunity responses by inducing immunogenic cell death (ICD). Unfortunately, tumors always develop multiple immunosuppressive mechanisms, such as the upregulation of immunosuppressive factors, to counteract the effects of immunogenic chemotherapy. Indoleamine 2,3-dioxygenase-1 (IDO1), a tryptophan catabolic enzyme overexpressed in tumor-draining lymph nodes (TDLNs) and tumor tissues, plays a pivotal role in the generation of the immunosuppressive microenvironment. Reversing IDO1-mediated immunosuppression may strengthen the ICD-induced immune response. Herein, we developed a nanoenabled approach for IDO1 pathway interference, which is accomplished by delivering IDO1 siRNA to both TDLNs and tumor tissues with the help of cationic lipid-assisted nanoparticles (CLANs). We demonstrated that the contemporaneous administration of OXA and CLANsiIDO1 could achieve synergetic antitumor effects via promoting dendritic cell maturation, increasing tumor-infiltrating T lymphocytes and decreasing the number of regulatory T cells in a subcutaneous colorectal tumor model. We further proved that this therapeutic strategy is applicable for the treatment of orthotopic pancreatic tumors and offers a strong immunological memory effect, which can provide protection against tumor rechallenge.