The anti-tumor effect of Euchema serra agglutinin on colon cancer cells in vitro and in vivo.

Eucheuma serra agglutinin (ESA) is a lectin derived from a marine red alga E. serra and binds specifically to mannose-rich sugar chains. Previous reports have indicated that ESA associates with several cancer cells via sugar chains on cell surfaces and induces apoptotic cell death. In this study, we investigated the effect of ESA on Colon26 mouse colon adenocarcinoma cells both in vitro and in vivo. ESA induced cell death against Colon26 cells in vitro, and the expression of caspase-3 and the translocation of phosphatidylserine in ESA-treated Colon26 cells suggested that this cell death was induced through apoptosis. An intravenous injection of ESA significantly inhibited the growth of Colon26 tumors in BALB/c mice; moreover, DNA fragmentation was detected in tumor cells following ESA treatment. These results indicated that ESA is effective as an anti-cancer drug not only in vitro but also in vivo. The side-effects of ESA were not considered to be serious because the decrease in body weight of the mice injected with it was negligible. These observations suggest that ESA has the potential to be an effective anti-tumor drug.