The tumor microenvironment serves as a core immunosuppressive barrier, and T cells are the key effector cells in anti-tumor immunity. Hypoxia, acidity, and nutrient deprivation in the microenvironment, together with immune checkpoints such as PD‑1/PD‑L1 and inhibitory cytokines, lead to insufficient T‑cell infiltration and functional exhaustion, rendering T cells unable to effectively kill tumor cells. Immunotherapy, which relieves suppression and activates T cells, represents an important strategy to overcome the tumor microenvironment.