CD8A and neoplasm: CircRNAs possess bidirectional regulatory capacities: they can promote tumor immune evasion by modulating the expression of immune checkpoint molecules, influencing the infiltration and activity of effector immune cells (e.g., CD8+ T cells), recruiting immunosuppressive cells (e.g., regulatory T cells and M2-type macrophages), and regulating immune signaling pathways; meanwhile, they can also activate antitumor immune responses.