MAPK3 and Hepatic fibrosis: Ribosomal S-6 kinase acting downstream of mitogen-activated protein kinase (MAPK) pathway/extracellular signal-regulated kinase (ERK1/2) signal pathway to phosphorylate C/EBP-beta in hepatic stellate cells was shown to play a critical role in the progression of CCl4-induced liver fibrosis [24].