MAPK1 and hepatocellular carcinoma: Furthermore, the effects of sorafenib were significantly correlated with basal pERK levels in these HCC cell lines by correlation analysis between the IC50 values of sorafenib and their pERK density values, indicating that sorafenib sensitivity could have direct links with the activation of the RAF/MEK/ERK signaling pathway and basal pERK levels in HCC tumor cells.