CD8A and neoplasm: Cytotoxic immune cells such as CD8+ T cells, natural killer (NK) cells, cytokine-induced killer (CIK) cells, and lymphokine-activated killer (LAK) cells are internalized by tumor cells; the released granzyme B cannot enter the cytoplasm of the tumor cell through vesicles and is taken up again by cytotoxic cells, which leads to their apoptosis, whereas non-cytotoxic cells, such as B cells, undergo degradation through the lysosomal-dependent pathway (17).