Induction of apoptosis by laminarin, regulating the insulin-like growth factor-IR signaling pathways in HT-29 human colon cells

In recent years, algae have been highlighted as potential sources of anticancer agents. Laminarin is a molecule found in marine brown algae that has potentially beneficial biological activities. However, these activities have not been investigated. In the present study, we examined the effects of laminarin on HT-29 cells and analyzed its effect on the insulin-like growth factor (IGF-IR) signaling pathway. 3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays revealed that laminarin induced cell death in a dose-dependent manner. Western blotting showed that laminarin decreased mitogen-activated protein kinases (MAPK) and ERK phosphorylation. Decreased proliferation depended on IGF-IR, which was associated with the downregulation of MAPK/ERK. These results are important for understanding the roles of IGF-IR in colon cancer cell tumorigenesis, and suggest that laminarin shows activity against human colon cancer.