CD274 and neoplasm: To boost the targeted delivery of PD-L1 siRNA to hypovascularizedlung metastases, a pH-responsive metastatic-targeted catalyst containingtumor-penetrating polymer (TP)/solid lipid-coated Prussian blue (TP-SL@PB)is developed for enhanced PD-L1 siRNA delivery and self-cascade antigencapture to reprogram tumor immunodeficiency (Figure a).