Nanomedicines modulating myeloid-derived suppressor cells for improving cancer immunotherapy

Great success in immunotherapy has revolutionized clinical cancer treatments. However, the response rate and overall survival rate remain unsatisfactory. As one of the immunological hallmarks of cancer, myeloidderived suppressor cells (MDSCs) induce strong immunosuppression, which leads to great hindrance for immunotherapy of cancer. Thus, MDSCs have been explored as an important immunotherapeutic target to enhance anticancer responses. Nanomedicines have been developed to target MDSCs to improve the immunotherapeutic efficacy owing to their ability of reversing immunosuppressive tumors into immunoresponsive ones. In this review, we describe the function of MDSCs in the tumor microenvironment and the immunosuppressive pathways that inhibit T cell functions. Additionally, recent developments in various nanoparticulate platforms, including nanocapsules, micelles, liposomes, mineralized/metallic nanoparticles and hydrogels, affecting through different pathways and functions of MDSCs as immunomodulatory agents are discussed and highlighted. These nanomedicines have been demonstrated with improved therapeutic efficacies by modulating MDSCs, and they have great potential of translation to clinical application in cancer nano-immunotherapy. (c) 2021 Elsevier Ltd. All rights reserved.