Antimetastatic effect of glycoprotein isolated from rice bran on colon 26-M3.1 cell line

Innate immune system might be a useful strategy for antimetastatic therapy. To examine the antitumor and immunomodulatory activities of a glycoprotein isolated from rice bran (GRB), we made an experiment on innate immune response against lung metastasis of colon 26-M3.1 carcinoma cells. To prove the effects of GRB, natural killer (NK) cytotoxicity assay and cytokine level estimation in relation to macrophage activation were performed. In experimental lung metastasis of colon 26-M3.1 cells, intravenous administration of GRB 2 days before tumor inoculation induced significant inhibition, by 77%. Intravenous GRB significantly augmented NK cell cytotoxicity against YAC-1 cells by releasing lymphocyte granule-mediated cytotoxic granzyme B. In addition, murine peritoneal macrophages stimulated by GRB produced various cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-12. The results suggest that GRB possesses an antitumor activity that prophylactically prevented tumor metastasis and may be associated with the activation of NK cells and macrophages.