Glycyrrhizin (GL), an important active ingredient of licorice root, which weakens the proinflammatory effects of high-mobility group box 1 (HMGB1) by blocking HMGB1 signaling. In this study, we investigated whether GL could suppress inflammation and carcinogenesis in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced murine model of colorectal cancer. ICR mice were divided into four groups (n = 5, each)-control group, GL group, colon cancer (CC) group, and GL-treated CC (CC + GL) group, and sacrificed after 20 weeks. Plasma levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α were measured using an enzyme-linked immunosorbent assay. The colonic tissue samples were immunohistochemically stained with DNA damage markers (8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxy-guanosine), inflammatory markers (COX-2 and HMGB1), and stem cell markers (YAP1 and SOX9). The average number of colonic tumors and the levels of IL-6 and TNF-α in the CC + GL group were significantly lower than those in the CC group. The levels of all inflammatory and cancer markers were significantly reduced in the CC + GL group. These results suggest that GL inhibits the inflammatory response by binding HMGB1, thereby inhibiting DNA damage and cancer stem cell proliferation and dedifferentiation. In conclusion, GL significantly attenuates the pathogenesis of AOM/DSS-induced colorectal cancer by inhibiting HMGB1-TLR4-NF-κB signaling.
Keywords: 8-NitroG; 8-OxodG; COX-2; Glycyrrhizin; HMGB1; SOX9; YAP1; colon cancer.