Acidic polysaccharide from Phellinus linteus inhibits melanoma cell metastasis by blocking cell adhesion and invasion.

The acidic polysaccharide (PL) from Phellinus linteus is an immunostimulator that has therapeutic activity against cancers. Here, we show that PL markedly inhibits melanoma cell metastasis in mice, and report that PL directly inhibits cancer cell adhesion to and invasion through the extracellular matrix, but that it has no direct effect on cancer cell growth. In addition, we found that PL increased macrophage NO production. These results suggest that PL has two antimetastatic functions, i.e., it acts as an immunopotentiator and as a direct inhibitor of cancer cell adhesion.