In this study, using a combined in vivo and in vitro approach, the expression of the UII/UT system in human hepatocellular carcinoma and in the BEL-7402 human hepatocellular cell line were investigated, and the effect of exogenous UII on the phosphorylation of PKC, ERK1/2, and p38 MAPK was examined to determine the possible mechanism underlying the pathogenesis of hepatocellular carcinoma. The gene discussed is MAPK3; the disease is hepatocellular carcinoma.