In a conditional bitransgenic mouse model of Myc-induced T-cell lymphomagenesis, Opavsky et al (12) demonstrated that inactivation of E2F2 (either E2F2+/− or E2F2−/−), but not of E2F1 or E2F3, significantly accelerated tumor onset and progression, indicating an haploinsufficient tumor suppressor function for E2F2 in T cells. This evidence concerns the gene E2F1 and neoplasm.