CD8A and neoplasm: First, radiation upregulates the expression of major histocompatibility complex I molecules on the surface of tumor cells, promotes dendritic cell (DC) maturation and tumor-associated antigen presentation, enhances the secretion of cytokines required for T cell infiltration by DC and tumor cells, such as chemokine (C-X-C motifs) ligand 9 (CXCL9), CXCL10, and CXCL16, and expands CD8+ T cells to enhance their cytotoxic activity [13].