E2F1 and central nervous system cancer: Similarly, E2F1 was significantly higher in grade WHO IV gliomas (32.01 ± 2.67) than in grade WHO III gliomas (18.57 ± 1.64) and grade WHO II (7.443 ± 1.64) (P < 0.001) and with the increase in the grade, its expression also showed a gradually increasing trend (Figure 1B).