Thereafter, activated CD8+ T cells can recognize TAA presented through a MHC class I molecule on cancer cells and induce their killing via the perforin-granzyme and/or Fas ligand (FasL)/tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) systems, although this depends on the degree of functional inhibition by the TME and the presence of immunosuppressive regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs). This evidence concerns the gene CD8A and neoplasm.