E2F1 and neoplasm: A compound can induce apoptosis in tumor cells through several mechanisms, such as blocking the cell cycle (Yang et al., 1996), inhibiting the phosphorylation of Bcl-2 and Bcl-xl (Chen et al., 2015), activating caspases (Wagner and Wagner, 2010), up-regulating E2F1 (Huang et al., 1980), and causing the release of cytochrome c.