Low Molecular Weight Mannogalactofucans Derived from Undaria pinnatifida Induce Apoptotic Death of Human Prostate Cancer Cells In Vitro and In Vivo

Low molecular weight mannogalactofucans (LMMGFs) prepared by enzymatic degradation of high molecular weight Undaria galactofucan (MF) were evaluated for their anti-cancer effects against human prostate cancer. Correlation NMR and linkage analyses confirmed that LMMGFs consist mainly of -fucose and -galactose units: -fucose units are 1,3-linked; -galactose units are terminal, 1,3- and/or 1,6-linked; both sugars are partially sulphated, fucose at positions O-2 and/or O-4 and galactose at O-3. Mannose residue, as a minor sugar, presents as the 1,4-linked terminal units. LMMGFs more significantly induced cell cycle arrest at the G0/G1 phase and cell death via suppression of the Akt/GSK-3/-catenin pathway than MF in human PC-3 prostate cancer cells. LMMGFs upregulated mRNA expression of death receptor-5 (DR-5), the ratio of Bax to Bcl-2, the cleavage of caspases and PARP, the depolarisation of mitochondrial membrane potential, and ROS generation. LMMGFs (200-400mg/kg) effectively reduced both tumour volume and size in a xenografted mouse model. These results demonstrated that LMMGFs attenuate the growth of human prostate cancer cells both in vitro and in vivo, suggesting that LMMGFs can be used as a potent functional ingredient in health-beneficial foods or as a therapeutic agent to prevent or treat androgen-independent human prostate cancer.