CD8A and neoplasm: Tumor immune escape occurs through a variety of immunosuppressive mechanisms, such as dysfunctional antigen-presenting cells (APCs), tumor cell resistance to immune attack, decreased cytotoxicity of CD8+ T cells and natural killer (NK) cells, induction of immunosuppressive cells such as myeloid-derived suppressor cells (MDSCs), transition of T helper (Th) cells from Th1 to Th2 and Th17, transition of macrophages from M1 to M2 (4).