The aim of this study is to investigate the role of Toll-like receptor (TLR) 4 in Ganoderma atrum polysaccharide (PSG-1)-induced antitumor activity. In vitro, the apoptosis rate of S-180 cells was increased in PSG-1-induced peritoneal macrophage derived from C3H/HeN (wild-type) mice, but not from C3H/HeJ (TLR4-deficient) mice. In the S-180 tumor model, phagocytosis, NO and ROS release, phosphorylation of MAPKs and Akt, and expression of NF-κB were increased by PSG-1 in peritoneal macrophage derived from C3H/HeN mice. Furthermore, PSG-1 elevated Th1 cytokine production and enhanced the cytotoxic activity of CTL and NK cells in C3H/HeN mice. In addition, PSG-1 decreased the tumor weight and increased the apoptosis rate and caspase-3 and caspase-9 activities of tumor derived from the C3H/HeN mice. However, none of these activities were observed in C3H/HeJ mice. In summary, these findings demonstrated that the antitumor activity of PSG-1 is mediated by TLR4.
Keywords: Ganoderma atrum polysaccharide; Toll-like receptor 4; adaptive immunity; antitumor; innate immunity.