RAF1 and hepatocellular carcinoma: ETS1, a transcription factor and downstream molecule of the Raf/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling pathway and the PI3K/AKT pathway [42, 43, 51, 52], is downregulated by sorafenib [53] and is involved in drug resistance to sorafenib in HCC [45, 50].