CD274 and breast cancer: constructed the MMP‐2‐liable peptide spacer incorporated prodrug vesicles which amplified antitumor immunity to eradicate the tumor in two breast immunocompetent mouse models.[165] The self‐delivery NPs was developed by conjugating programmed cell death ligand 1 (PD‐L1) inhibitor Metformin with photosensitizer Ce6 through MMP‐2 cleavable peptide GPLGVRGDK, fulfilled superior targeting ability, hampered the PD‐L1 expression in breast cancer tissue.[166] Improvement of the chemotherapeutics selectivity through tumor‐associated enzyme‐activated prodrugs is appealing strategy.