CD8A and neoplasm: Effector CD8+ T cells gradually degenerate due to continuous tumor antigen stimulation, immunosuppressive cell suppression (e.g., Treg cells and immunosuppressive B cells), and imbalance between physical and chemical status, thereby reducing their proliferation and secretion of effector cytokines (IL-6, TNF-α, and IFN-γ), known as “T cell exhaustion” (Chen et al., 2021).