Antitumor metastasis activity of pectic polysaccharide purified from the peels of Korean Citrus Hallabong

A polysaccharide fraction, HBE-III, was successfully purified in a high yield (40.4%) from its crude polysaccharide (HBE-0) which was prepared from pectinase hydrolysates of the peels of the Korean Citrus Hallabong. In experimental lung metastasis studies of Colon 26-M3.1 carcinoma cells, prophylactic administration of HBE-III significantly inhibited lung metastasis in a dose-dependent manner. In an in vitro cytotoxicity analysis, HBE-III (up to 1000 μg/mL) did not affect the growth of Colon 26-M3.1 cells and normal cells. HBE-III enhanced production of IL-6 and IL-12 by murine peritoneal macrophages. In an assay for natural killer (NK) cell activity, HBE-III (1000 μg/mouse, i.v.) significantly augmented NK cytotoxicity against Yac-1 tumor cells. The depletion of NK cells by injection of mouse anti-asialo GM1 serum abolished the inhibitory effect of HBE-III on lung metastasis of Colon 26-M3.1 cells. These data suggest that HBE-III may inhibit tumor metastasis via activation of macrophages and NK cells.