These cells may induce immunotolerance through the expression of immune-checkpoint proteins, such as PD-1 and CTLA-4, on the surfaces of cells, interfering with the immune response at the tumor site, in addition to the secretion of immunomodulators, such as interleukin 10, interleukin 35, and TGF-β [67]. This evidence concerns the gene PDCD1 and neoplasm.