Aminated fucoidan promotes the invasion of 3 LL cells through reconstituted basement membrane: its possible mechanism of action.

Fucoidan is reported to have an antimetastatic activity. In the present study, we prepared an amino group-introduced derivative of fucoidan and examined its effect on the invasion of 3 LL cells through a reconstituted basement membrane (MatrigelTM). Unlike native fucoidan, the aminated derivative promoted the tumor cell invasion: maximal promotion (240% of control invasion) was obtained with 5 micrograms/ml. However, with higher concentrations (10-30 micrograms/ml) of the fucoidan derivative, the promotion was gradually reduced to 130% of control. Both native and aminated fucoidans inhibited specifically the attachment of 3 LL cells to laminin. Interestingly, aminated fucoidan, unlike the native one, promoted the tumor cell adhesion to immobilized synthetic laminin B 1 chain peptide, YIGSR, over a concentration range of 0.5-5 micrograms/ml. Higher concentrations (7-20 micrograms/ml) of the aminated derivative suppressed the adhesive ability of 3 LL cells to YIGSR. 3 LL cells secreted a 50-kDa form of urokinase-type plasminogen activator (u-PA) in the culture medium. Addition of aminated fucoidan (5 micrograms/ml) or YIGSR (10 micrograms/ml) resulted in a 1.7-fold increase in u-PA activity. This effect was enhanced up to 3.5-fold when both substances were simultaneously added. The addition of native fucoidan had no effect. The present results suggest that the 67-kDa receptor-mediated binding of 3 LL cells to laminin activates their invasiveness, especially by enhancing the extracellular u-PA levels. Aminated, but not native, fucoidan may act to enhance the laminin-receptor interaction at the limited concentration range.