CD8A and cancer: Within the TME, exhaustion or depletion of antitumor immune components (such as CD8+ and CD4+ T cells, B cells, and DCs), recruitment and expansion of immunosuppressive components (including regulatory T cells (Tregs), TAMs, myeloid-derived suppressor cells (MDSCs), cancer-associated fibroblasts (CAFs)), increased levels of immunosuppressive cytokines (such as TGF-α, TGF-β, VEGF, IL-6, and IL-8), and altered intratumoral metabolic profiles and hypoxia, collectively contribute to resistance to immunotherapy [7,32].