Mechanistically, naive CD8+ T cells are activated by recognition of specific peptides presented by major histocompatibility class I (MHC-I) on antigen presenting cells (APCs) in peripheral lymphatic organs (Fig. 1), however, tumor cells can significantly reduce MHC-I antigen presentation, thereby "hiding" in front of CD8+ T cells and achieving immune escape. Here, CD8A is linked to neoplasm.