Effects of fucoidan on proliferation, AMP-activated protein kinase, and downstream metabolism- and cell cycle-associated molecules in poorly differentiated human hepatoma HLF cells

Survival rates are low in patients with poorly differentiated hepatocellular carcinoma (HCC). Fucoidan, a sulfated polysaccharide derived from brown seaweed, has anticancer activity; however, the effects of fucoidan on poorly differentiated HCC remain unclear. In this study, we investigated the effects of fucoidan on AMP-activated protein kinase (AMPK), a proliferation regulator, and its downstream metabolismand cell cycle-related molecules in a poorly differentiated human hepatoma HLF cell line. HLF cells were treated with fucoidan (10, 50, or 100 mu g/ml; n=4) or phosphate buffered saline (control; n=4) for 96 h. Proliferation was evaluated by counting cells every 24 hrAMPK, TSC2, mTOR, GSK3P, acetyl-CoA carboxylase (ACC), ATP-citrate lyase, p53, cyclin D1, cyclin-dependent kinase (CDK) 4, and CDK6 expression and/or phosphorylation were examined by immunoblotting 24 h after treatment with 100 mu g/ml fucoidan. Cell cycle progression was analyzed by fluorescence-activated cell sorter 48 h after treatment. Treatment with 50 or 100 mu g/ml fucoidan significantly and dose- and time-dependently suppressed HLF cell proliferation (P<0.0001). Fucoidan induced AMPK phosphorylation on 5er172 24 h after treatment. Although no differences were seen in expression and phosphorylation levels of TSC2, mTOR, GSK3 beta, ATP-citrate lyase, and p53 between the control and fucoidan-treated HLF cells, fucoidan induced ACC phosphorylation on Ser79. Moreover, fucoidan decreased cyclin D1, CDK4 and CDK6 expression 24 h after treatment. Furthermore, HLF cells were arrested in the Gl/S phase 48 h after fucoidan treatment. We demonstrated that fucoidan suppressed HLF cell proliferation with AMPK phosphorylation. We showed that fucoidan phosphorylated ACC and downregulated cyclin D1, CDK4 and CDK6 expression. Our findings suggest that fucoidan inhibits proliferation through AMPK-associated suppression of fatty acid synthesis and Gl/S transition in HLF cells.