In recent years, there has been a growing body of research on the efficacy of checkpoint inhibitors with breast cancers, specifically antibodies against cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed cell death-1 protein (PD-1) and programmed cell death ligand-1 (PD-L1) (Figure 1B). This evidence concerns the gene PDCD1 and breast cancer.