CD8A and cancer: Accumulating evidence has demonstrated that the presence of tumor specific T cells has been correlated with improved clinical outcome in different human cancers [28,29], such as CD8+ T cell and CD4+ T cell [30,31], whereas regulatory T cells (Tregs) could accumulate aberrantly in some types of tumor to suppress antitumor immunity and support the establishment of immunological hypo-responsiveness microenvironment [32].