Structurally distinct enzymatic depolymerization products of Fucus evanescens fucoidan exert cell line-specific...

Fucoidans are sulfated polysaccharides from brown algae with promising anticancer properties, but the specific structural determinants underlying their biological effects remain poorly defined. Here, four different GH107 family endo-fucanases were used to depolymerize Fucus evanescens fucoidan (FeF), yielding eight high- (HMP) and low-molecular weight (LMP) derivatives differing Mw and sulfation. Enzymatic depolymerization revealed the hidden structure regularity of FeF fucoidan, characterized by extended mostly regular sites of [→4)-α-L-Fucp2S-(1→3)-α-L-Fucp2S-(1→]_n and [→4)-α-L-Fucp2S-(1→3)-α-L-Fucp2,4S-(1→]_n linked by less regular sites rich in 2,3-di-sulfated L-fucose residues. The ability of FeF and its enzymatic derivatives to inhibit the colony growth of human cancer cell lines (MCF-7, MDA-MB-231, DLD-1, HuTu80, and SK-MEL-28) was further tested. Reduction in FeF molecular weight (Mw) proved critical for inhibiting colony growth of DLD-1 and MCF-7 cells, with native FeF most potent and LMP derivatives showing practically no effect. In contrast, certain HMP or LMP derivatives with reduced Mw and optimized sulfate content and/or sulfation pattern (especially 2,4-di-sulfated) exhibited enhanced activity against MDA-MB-231, SK-MEL-28, and HuTu 80 cell lines compared to native FeF. Additional EGF-treatment was found to alter the sensitivity of certain cancer cells to specific structural motifs of fucoidans. Certain HMP and LMP derivatives also demonstrated enhanced chemopreventive effects against EGF-induced JB6 Cl41 transformation. These findings reveal that structural determinants of fucoidan anticancer effects differ not only by cancer cell type but also by exogenous or endogenous factors modulating cellular responses. These data further demonstrate the efficacy of specific endo-fucanases in tailoring native fucoidan structure to modulate its biological activity.