Indeed, E2F2/5/8 have been shown to be novel biomarkers for prognosis for ovarian cancer (Zhou et al., 2019), E2F1/2/5/8 for lung cancer (Sun et al., 2018), and multiple members of E2F for gastric and breast cancer (Manicum et al., 2018; Sun et al., 2019). Here, E2F1 is linked to breast cancer.