Wnt/β-catenin signaling regulates MAPK and Akt1 expression and growth of hepatocellular carcinoma cells.

In hepatocellular carcinoma (HCC), Wnt/β-catenin, Ras/MAPK and PI3K/AKT signaling pathways form a complex network and play important roles during HCC genesis and development. To study their relationship and the influence on cell growth, the siRNA directed against β-catenin was transfected into HCC HepG2 cells. β-catenin mRNA and protein levels were measured respectively at various times by RT-PCR and Western blot. Furthermore, HCC cell growth was measured by MTT assay. Finally, MAPK family and Akt1 protein levels were also measured by Western blot. After the transfection, β-catenin mRNA levels were markedly inhibited at 24 h and increased gradually at 48, 72 and 96 h; β-catenin protein levels decreased gradually at 24, 48 and 72 h and slightly increased at 96 h. HCC cell growth was inhibited from 24-72 h, but this inhibition decreased at 96 h. ERK1/2 (p42/p44 MAPK), JNK/SAPK, p38 MAPK, and Akt1 protein levels showed no change following transfection, while their phosphorylated protein levels showed changes. Thus, siRNA directed against β-catenin markedly decreased β-catenin gene expression and inhibited cell growth. Wnt/β-catenin signaling pathway might regulate Ras/MAPK and PI3K/Akt signaling pathways through regulation of the phosphorylation state of ERK1/2, JNK/SAPK and Akt1 protein in HCC HepG2 cells. These pathways might compensate for the inhibitory effect of β-catenin, thereby affecting tumor cell growth and others downstream factors.