The tumor microenvironment (TME), which includes cancer cells, stromal cells, and distant recruited cells, such as infiltrating immune cells (myeloid cells and lymphocytes), bone marrow-derived cells (BMDCs), and secreted factors such as cytokines and chemokines, play a crucial role in tumor progression and affect the clinical benefit from novel strategies of immunological checkpoint blockade (ICB, PD-1/L1, and CTLA-4) (21, 22). This evidence concerns the gene PDCD1 and cancer.