MDSCs are another critical cell type in TME that are related to angiogenesis, tumor progression, and metastasis.207, 208 MDSCs elevated the expression of anti‐inflammatory cytokines and IDO, leading to Treg activation and antigen‐specific T cell suppression.209 Therefore, nanomedicine aiming at eliminating MDSCs could improve cancer immunotherapy. This evidence concerns the gene IDO1 and cancer.