CD8A and head and neck squamous cell carcinoma: In HNSCC, E2F4 was negatively correlated with immune cell infiltration by cells, including CD4+ T (R = − 0.185, P = 1.47e−04), CD8+ T (R = − 0.185, P = 3.47e−05), Treg (R = − 0.232, P = 2.03e−07), and T cell follicular helper (R = − 0.208, P = 3.34e−06) cells.