CD274 and breast carcinoma: Breast cancer-derived small extracellular vesicles (sEVs) containing microRNAs such as miR-106b-5p and miR-18a-5p induces the upregulation of PD-L1 on TAMs by activating PTEN and protein inhibitor of activated STAT 3 (encoded by PIAS3)/STAT3 signaling pathways, thereby promoting metastatic progression [122].