Next Generation Sequencing of tumor tissue (4T1 cell) of BALB/c

Immune checkpoint blockade (ICB), particularly programmed death 1 (PD-1) and its ligand (PD-L1), has shown considerable clinical benefits in patients with various cancers. Many studies show that PD-L1 expression may be biomarkers to help select responders for anti-PD-1 treatment. Therefore, it is necessary to elucidate the molecular mechanisms that control PD-L1 expression. As a potential chemosensitizer and anticancer drug, copper combined with disulfiram (DSF) kills tumor cells by regulating multiple signaling pathways and transcription factors in vitro and in vivo. Here, we showed that DSF increased PD-L1 expression in triple negative breast cancer (TNBC) cells. Through TCGA data analysis, we found that DNMT1 and IRF7 were highly expressed and the hypermethylation states in the IRF7 gene body promoter region in TNBC vs normal breast tissue (NBT). Then, we demonstrated that DSF affected PD-L1 expression via DNMT1-mediated IRF7 hypomethylation in two TNBC cell lines. In vivo experiments, DSF significantly enhanced the response to PD-1 antibody (Ab) in the triple-negative 4T1 BC mouse model. By analyzing the results of the tumor tissue sequencing, the DSF joint anti-PD-1 Ab could be a significant activation of anti-tumor immunity. And the inactive state of immune associated pathways was found to be reversed, such as Th1 and Th2 cell differentiation, antigen processing and presentation, natural killer cell-mediated cytotoxicity and T cell receptor signal transduction. In conclusion, we found that DSF could up-regulate PD-L1 in TNBC cells and elucidated its mechanism. Our findings revealed that the combination of DSF and anti-PD-1 Ab could activate the tumor immune microenvironment (TIME) to show much better antitumor efficacy than monotherapy. mRNA profiles of 12 samples (4T1 tumor tissue, control/DSF treatment/anti-PD-1 treatment/combine, 3 replicates per group)