PDCD1 and breast cancer: A recently designed biomimetic magnetic nanoparticle (Fe3O4-SAS@PLT) built from sulfasalazine (SAS)-loaded mesoporous magnetic nanoparticles (Fe3O4) and platelet (PLT) membrane camouflage effectively triggered ferroptosis by inhibiting system xc− and improving the efficacy of programmed cell death 1 (PD-1) immune checkpoint blockade therapy in a mouse model of metastatic tumors of murine breast cancer 4T1 [165].