E2F1 and retinoblastoma: In RB1-mutated retinoblastoma, all three activating E2Fs were significantly upregulated: E2F1 (FC = 1.86, P = 2.56E-03), E2F2 (FC = 2.84, P = 2.31E-04), and E2F3 (FC = 3.72, P = 2.18E-10; Table 1).