Immunostimulation-mediated antitumor activity by preconditioning with rice-shochu distillation residue against implanted tumor in mice.

ABSTRACT

We investigated the ability of rice-shochu postdistillation residue (RSDR) to stimulate the activity of macrophages. RSDR significantly stimulated mouse macrophage activity and induced significant IL-12 production in vitro. In syngeneic C38 solid tumor model in mice, a diet containing 1.0% RSDR caused a significant suppression of tumor growth and prolonged the life span of the tumor-bearing mice. Further, using this model, mice fed for 21 days with RSDR showed significantly increased levels of serum IL-12 and IFN-gamma compared with controls. Moreover, the splenic NK cell activity of mice fed with RSDR was significantly elevated compared with that of mice on a normal diet and thereby suppressed C38 tumor growth. We also investigated the tumor growth suppressing effect of RSDR using a tumor model of B16-F10 melanoma cells. Dietary preconditioning with RSDR significantly suppressed B16-F10 tumor growth. Moreover, RSDR significantly increased the production of IL-12 either before or after B16-F10 tumor implantation. These results suggest that dietary RSDR suppresses tumor growth by stimulating the immune system of the host.