CD8A and cancer: Immune escape has been one of the major characteristics in malignant tumors involving multiple probable mechanisms [54, 55], for example the increasing immune suppressive cells including Treg cells and tumour-associated macrophages (TAM) in tumor microenvironment [47], and the up-regulated expression of immunosuppressive molecules for instance cytotoxic T lymphocyte associated antigen-4 (CTLA-4), also decreasing expression of cancer antigens which results the inactivation of tumor killing CD8 + T cells [56–59].