MDSCs also aid in tumor establishment and sustainment via the production of free radical generating species (O2, NO, PNT, H2O2), nitration of chemokines/cytokines, blockade of CD8+ T cells with tumor cells, and depletion of amino acids essential to T-cell proliferation (i.e., arginine, cysteine, and tryptophan) [12–14, 16, 17]. This evidence concerns the gene CD8A and neoplasm.