CD274 and breast cancer: In this study, a synergistic immunotherapy strategy for breast cancer incorporating immune cell infiltration, immunogenic cell death (ICD), and dendritic cell (DC) maturation through a reactive oxygen species (ROS)‐responsive dual‐targeted smart nanosystem (anti‐PD‐L1‐TKNP) for the simultaneous release of DOX, R848, and MIP‐3α in the tumor microenvironment is reported.