CD8A and neoplasm: It has been reported that the expression of T cell co-inhibitory molecules (PD1, PD-L1 and CTLA-4) can induce exhaustion of effector T cells, while blockade of PD-1/PD-L1 T cell co-inhibitory axis can efficiently enhance the infiltration of CD8+ T cells into TIME and restore the anti-tumor immune response (255, 256).