MDSCs inhibit NK-cell-mediated ADCC by repressing the Fc receptor on the surface of NK cells [39] and secrete TGF-β1 to inhibit adaptive immune responses via effector T-cell function, causing expression of Programmed cell Death-1 (PD-1) on the surface of Tumor-Infiltrating Lymphocytes (TILs) [40]. This evidence concerns the gene PDCD1 and neoplasm.