E2F1 and hepatocellular carcinoma: Hsu et al. found that the regulation of the E2F1–Rb–cyclin E1 complex might play a crucial role in mediating sorafenib resistance in HCC cells, and depletion of cyclin E1 expression reversed sorafenib resistance in HCC cells in terms of cell growth and apoptosis induction (Hsu et al., 2016).