CD274 and triple-negative breast carcinoma: Overexpression of PD-L1 is found acrossmany tumor types, including metastatic triple negative breast cancer(TNBC).26−28 Targeting immune checkpoints with monoclonal antibodieshas revolutionized the treatment of several difficult-to-treat cancers,28 whereas small molecule inhibitors of PD-L1 havealso shown promising pro-immune antitumor effects in preclinical models.29 Nonetheless, despite their success, immunotherapyis in most cases insufficient to eradicate metastatic tumors in patientswith advanced cancer, even in combination with chemotherapy.