CD274 and breast cancer: AMPK activation further induces endoplasmic reticulum accumulation, endoplasmic reticulum-associated degradation, and decrease in PD-L1 level through PD-L1 phosphorylation and subsequent glycosylation.219 Tumor-infiltrating cytotoxic T cells are correlated with better prognosis in breast cancer.220 Meanwhile, increased TIL infiltration and PD-L1 level are also seen in patients with TNBC.221 In particular, some conventional drugs, including aspirin and atenolol can enhance the antitumor activity of metformin.