In BC TME, accumulated immunosuppressive cells (e.g., myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs) and regulatory T cells (T regs) and evaluated expression of immune checkpoints (e.g., CTLA-4 and PD-1) were reported to induce immune evasion of tumor cells [44,45]. This evidence concerns the gene PDCD1 and breast cancer.