E2F1 and head and neck cancer: A study by Yaoxu et al. investigated the expression of E2F genes in head and neck cancer patients and found that the expression levels of E2F1, E2F2, E2F5, E2F6, E2F7, and E2F8 in the N2 and N3 stages were significantly higher than those in the N0 and N1 stages [47].