A systematic review including 110 studies confirmed that chemotherapy could regulate the tumor immune microenvironment, including increasing infiltration of CD8+ cytotoxic T cells, reduction of FOXP3+ Treg and higher PD-L1 expression (29), proving that traditional chemotherapy could cooperate with immune checkpoint inhibitors to improve the anti-tumor ability of tumor reactive T cells by altering tumor immune micro-environment (Figure 1A). This evidence concerns the gene CD8A and neoplasm.