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.