Natural killer cell–mediated anticancer effects of an arabinogalactan derived from rice hull in CT26 colon cancer–bearing mice

Rice hull polysaccharides (RHPS) have been reported to activate innate immunity in mice. This study investigated the effects of RHPS on natural killer (NK) cell-mediated cytotoxicity in vitro and the possible underlying anticancer mechanisms in vivo. The results showed that sustained exposure to RHPS increased NK-92MI cell-mediated cytotoxicity in a time- and concentration-dependent manner. In addition, RHPS upregulated the expression of Fas ligand, TNF-related apoptosis-inducing ligand, perforin, and granzyme B of NK-92MI cells and induced the secretion of IFN-γ and TNF-α. In the in vivo experiment, colon cancer CT26-bearing mice were used to investigate the effects of RHPS in cytotoxicity and anticancer. The results revealed that RHPS inhibited cancer weight and volume in CT26-bearing mice and significantly upregulated splenic cytotoxicity and NK-cell population. Moreover, RHPS treatment increased NK-cell infiltration in tumors. Thus, RHPS can enhance NK-cell activation in vivo and in vitro, thereby exhibiting anticancer activity.