Objective To investigate the inhibitory effect and mechanism of lentinan on colitis-associated colorectal cancer (CAC) induced by azomethane (AOM)/dextran sulfate sodium salt (DSS) through the IL-6/ STAT3 pathway.

Methods C57BL/6 mice were randomly divided into a control group, a model group, a low-dose group (0.865 mg/kg lentinan), a medium-dose group (1.73 mg/kg lentinan), and a high-dose group (3.46 mg/kg lentinan). Except the control group, CAC was induced by AOM/DSS in the other groups, and corresponding drugs were injected intraperitoneally during the modeling process. Body mass, disease activity index (DAI) score, colon length, and tumor number were compared among all groups. Hematoxylin–eosin staining was used to observe the pathological morphology of colon. ELISA was utilized to detect the IL-6, IL-1β, and IL-18 contents in serum. Western blot analysis was conducted to detect the expression levels of IL-6, p-STAT3, and c-Myc in colon tissues.

Results The tumor number, DAI score, serum IL-6, IL-1β, and IL-18 contents and the expression levels of IL-6, p-STAT3, and c-Myc in the colon tissue of the model group were higher than those of the control group, while the body mass and colon length were lower than those of the control group (P<0.05). The pathological morphology of colon tissues showed adenocarcinoma formation. After different doses of lentinan intervention, the tumor number, DAI score, serum IL-6, IL-1β, and IL-18 contents and the expression levels of IL-6, p-STAT3, and c-Myc in colon tissues were all lower than those in the model group, while body mass and colon length were higher than those in the model group (P<0.05). The pathological morphology of colon tissues showed adenomas of different grades but no adenocarcinoma was found.

Conclusion Lentinan inhibits CAC formation, and its anticancer effect is related to the inhibition of the IL-6/STAT3 pathway.