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.
Keywords: Anticancer; Arabinogalactan; Cytotoxicity; Natural killer cell; Polysaccharides; Rice hull.
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